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1
Shillington, Rory Brendan. "Silicon Carbide Devices in High Efficiency DC-DC Power Converters for Telecommunications." Thesis, University of Canterbury. Electrical and Computer Engineering, 2012. http://hdl.handle.net/10092/7504.
Full textAbstract:
The electrical efficiency of telecommunication power supplies is increasing to meet customer demands for lower total cost of ownership. Increased capital cost can now be justified if it enables sufficiently large energy savings, allowing the use of topologies and devices previously considered unnecessarily complex or expensive.
Silicon carbide Schottky diodes have already been incorporated into commercial power supplies as expensive, but energy saving components. This thesis pursues the next step of considering silicon carbide transistors for use in telecommunications power converters. A range of silicon carbide transistors was considered with a primary focus on recently developed, normally-off, junction field effect transistors.
Tests were devised and performed to uncover a number of previously unpublished characteristics of normally-off silicon carbide JFETs. Specifically, unique reverse conduction and associated gate current draw relationships were measured as well as the ability to block small reverse voltages when a negative gate-source voltage is applied. Reverse recovery-like characteristics were also measured and found to be superior to those of silicon MOSFETs. These characteristics significantly impact the steps that are required to maximize efficiency with normally-off SiC JFETs in circuits where synchronous rectification or bidirectional blocking is performed.
A gate drive circuit was proposed that combines a number of recommendations to achieve rapid and efficient switching of normally-off SiC JFETs. Specifically, a low transient output impedance was provided to achieve rapid turn-on and turn-off transitions as well as a high dc output impedance to limit the steady state drive current while sustaining the turned-on state. A prototype circuit was constructed using building blocks that are typically found in single chip MOSFET drivers. The circuit was shown to operate well from a single supply, alleviating the need for a split supply such as that required by many published JFET drive circuits. This demonstrated a proof of concept for a single chip JFET driver solution.
An active power factor correction circuit topology was extensively modelled and a prototype designed and tested to verify the model. The circuit was able to operate at switching frequencies in excess of 100kHz when using SiC JFETs, whereas silicon MOSFETs could only achieve switching frequencies of several kHz before switching losses became excessive. The circuit was designed as the dc equivalent for a 2kW, 230V AC input power converter with a split +/-400V dc output.
A commercial single phase telecommunications power converter was modified to utilise normally-off SiC JFETs in its power factor correction circuit. The converter was tested and found to achieve similar electrical efficiency with 1200V SiC JFETs to that achieved with 600V silicon MOSFETs. The performance of the 1200V SiC JFETs in this application was also compared to that of 900V silicon MOSFETs and found to be superior.
Finally, a prototype three-phase cyclo-converter was modified to use 1200V normallyoff SiC JFETs in place of 600V silicon MOSFETs and found to achieve similar electrical efficiency to the silicon MOSFETs in a 208V three phase system. These results strongly indicate that the 1200V SiC JFETs would provide better performance than 900V silicon MOSFETs in a 400V three phase system (that had been considered for commercial development).
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Zhao, Xiaonan. "High-Efficiency and High-Power Density DC-DC Power Conversion Using Wide Bandgap Devices for Modular Photovoltaic Applications." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/89025.
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With the development of solar energy, power conversion systems responsible for energy delivering from photovoltaic (PV) modules to ac or dc grid attract wide attentions and have significantly increased installations worldwide. Modular power conversion system has the highest efficiency of maximum power point tacking (MPPT), which can transfer more solar power to electricity. However, this system suffers the drawbacks of low power conversion efficiency and high cost due to a large number of power electronics converters. High-power density can provide potentials to reduce cost through the reduction of components and potting materials. Nowadays, the power electronics converters with the conventional silicon (Si) based power semiconductor devices are developed maturely and have limited improvements regarding in power conversion efficiency and power density. With the availability of wide bandgap devices, the power electronics converters have extended opportunities to achieve higher efficiency and higher power density due to the desirable features of wide bandgap devices, such as low on-state resistance, small junction capacitance and high switching speed.
This dissertation focuses on the application of wide bandgap devices to the dc-dc power conversion for the modular PV applications in an effort to improve the power conversion efficiency and power density.
Firstly, the structure of gallium-nitride (GaN) device is studied theoretically and characteristics of GaN device are evaluated under testing with both hard-switching and soft-switching conditions. The device performance during steady-state and transitions are explored under different power level conditions and compared with Si based devices.
Secondly, an isolated high-efficiency GaN-based dc-dc converter with capability of wide range regulation is proposed for modular PV applications. The circuit configuration of secondary side is a proposed active-boost-rectifier, which merges a Boost circuit and a voltage-doubler rectifier. With implementation of the proposed double-pulse duty cycle modulation method, the active-boost-rectifier can not only serve for synchronous rectification but also achieve the voltage boost function. The proposed converter can achieve zero-voltage-switching (ZVS) of primary side switches and zero-current-switching (ZCS) of secondary side switches regardless of the input voltages or output power levels. Therefore, the proposed converter not only keeps the benefits of highly-efficient series resonant converter (SRC) but also achieves a higher voltage gain than SRC and a wide range regulation ability without adding additional switches while operating under the fixed-frequency condition. GaN devices are utilized in both primary and secondary sides. A 300-W hardware prototype is built to achieve a peak efficiency of 98.9% and a California Energy Commission (CEC) weighted efficiency of 98.7% under nominal input voltage condition.
Finally, the proposed converter is designed and optimized at 1-MHz switching frequency to pursue the feature of high-power density. Considering the ac effects under high frequency, the magnetic components and PCB structure are optimized with finite element method (FEM) simulations. Compared with 140-kHz design, the volume of 1-MHz design can reduce more than 70%, while the CEC efficiency only drops 0.8% at nominal input voltage condition. There are also key findings on circuit design techniques to reduce parasitic effects. The parasitic inductances induced from PCB layout of primary side circuit can cause the unbalanced resonant current between positive and negative half cycles if the power loops of two half cycles have asymmetrical parasitic inductances. Moreover, these parasitic inductances reflecting to secondary side should be considered into the design of resonant inductance. The parasitic capacitances of secondary side could affect ZVS transitions and increase the required magnetizing current. Because of large parasitic capacitances, the dead-time period occupies a large percentage of entire switching period in MHz operations, which should be taken into consideration when designing the resonant frequency of resonant network.<br>Doctor of Philosophy<br>Solar energy is one of the most promising renewable energies to replace the conventional fossils. Power electronics converters are necessary to transfer power from solar panels to dc or ac grid. Since the output of solar panel is low voltage with a wide range and the grid side is high voltage, this power converter should meet the basic requirements of high step up and wide range regulation. Additionally, high power conversion efficiency is an important design purpose in order to save energy. The existing solutions have limitations of narrow regulating range, low efficiency or complicated circuit structure. Recently, the third-generation power semiconductors attract more and more attentions who can help to reduce the power loss. They are named as wide band gap devices. This dissertation proposed a wide band gap devices based power converter with ability of wide regulating range, high power conversion efficiency and simple circuit structure. Moreover, this proposed converter is further designed for high power density, which reduces more than 70% of volume. In this way, small power converter can merge into the junction box of solar panel, which can reduce cost and be convenient for installations.
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LaBella, Thomas Matthew. "A High-Efficiency Hybrid Resonant Microconverter for Photovoltaic Generation Systems." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/50526.
Full textAbstract:
The demand for increased renewable energy production has led to increased
photovoltaic (PV) installations worldwide. As this demand continues to grow, it is
important that the costs of PV installations decrease while the power output capability
increases. One of the components in PV installations that has lots of room for improvement
is the power conditioning system. The power conditioning system is responsible for
converting the power output of PV modules into power useable by the utility grid while
insuring the PV array is outputting the maximum available power. Modular power
conditioning systems, where each PV module has its own power converter, have been
proven to yield higher output power due to their superior maximum power point tracking
capabilities. However, this comes with the disadvantages of higher costs and lower power
conversion efficiencies due to the increased number of power electronics converters. The
primary objective of this dissertation is to develop a high-efficiency, low cost
microconverter in an effort to increase the output power capability and decrease the cost of
modular power conditioning systems.
First, existing isolated dc-dc converter topologies are explored and a new topology
is proposed based on the highly-efficient series resonant converter operating near the series
resonant frequency. Two different hybrid modes of operation are introduced in order to
add wide input-voltage regulation capability to the series resonant converter while
achieving high efficiency through low circulating currents, zero-current switching (ZCS)
of the output diodes, zero-voltage switching (ZVS) and/or ZCS of the primary side active
switches, and direct power transfer from the source to the load for the majority of the
switching cycle. Each operating mode is analyzed in detail using state-plane trajectory
plots. A systematic design approach that is unique to the newly proposed converter is
presented along with a detailed loss analysis and loss model. A 300-W microconverter
prototype is designed to experimentally validate the analysis and loss model. The converter
featured a 97.7% weighted California Energy Commission (CEC) efficiency with a
nominal input voltage of 30 V. This is higher than any other reported CEC efficiency for
PV microconverters in literature to date.
Each operating mode of the proposed converter can be controlled using simple
fixed-frequency pulse-width modulation (PWM) based techniques, which makes
implementation of control straightforward. Simplified models of each operating mode are
derived as well as control-to-input voltage transfer functions. A smooth transition method
is then introduced using a two-carrier PWM modulator, which allows the converter to
transition between operating modes quickly and smoothly. The performance of the voltage
controllers and transition method were verified experimentally.
To ensure the proposed converter is compatible with different types of modular
power conditioning system architectures, system-level interaction issues associated with
different modular applications are explored. The first issue is soft start, which is necessary
when the converter is beginning operation with a large capacitive load. A novel soft start
method is introduced that allows the converter to start up safely and quickly, even with a
short-circuited output. Maximum power point tracking and double line frequency ripple
rejection are also explored, both of which are very important to ensuring the PV module is
outputting the maximum amount of available power.
Lastly, this work deals with efficiency optimization of the proposed converter. It
is possible to use magnetic integration so that the resonant inductor can be incorporated
into the isolation transformer by way of the transformer leakage inductance in order to
reduce parts count and associated costs. This chapter, however, analyzes the disadvantages
to this technique, which are increased proximity effect losses resulting in higher conduction
losses. A new prototype is designed and tested that utilizes an external resonant inductor
and the CEC efficiency was increased from 97.7% to 98.0% with a marginal 1.8% total
cost increase. Additionally, a variable frequency efficiency optimization algorithm is
proposed which increases the system efficiency under the high-line and low-line input
voltage conditions. This algorithm is used for efficiency optimization only and not control,
so the previously presented simple fixed-frequency modeling and control techniques can
still be utilized.<br>Ph. D.
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Yan, Jinghui. "Full Bridge LLC Converter Secondary Architecture Study for Photovoltaic Application." Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/82490.
Full textAbstract:
The increasing global energy demand calls for attention on renewable energy development. Among the available technology, the photovoltaic (PV) panels is a popular solution. Thus, targeted Power Conditioning Systems (PCSs) are drawing increased attention in research. Microconverter is one of the PCS that can support versatile applications in various power line architectures. This work focuses on the comparison of circuit secondary side architectures for LLC converter for microconverter application.
As the research foundation, general characteristic of solar energy and PV panel operation are introduced for the understanding of the needs. Previous works are referenced and compared for advantages and limitation. Base on conventional secondary resonant full bridge LLC converter, the two sub-topologies of different secondary rectification network: active, full bridge secondary and active voltage doubler output end LLC converter are presented in detail. The main operating principle is also described in mathematical formula with the corresponding cycle-by-cycle operation to ensure the functional equality before proceeding to performance comparison.
Circuit efficiency analysis is conducted on the main power stage and the key components with frequency consideration. The hardware circuit achieved the designed function while the overall hardware efficiency result agrees with analysis. In the implementation, the transformer is costume built for the system pacification. Another part is the parasitic effect analysis. At a high operating frequency and to achieve very high-frequency operation, parasitic effect need to be fully understood and considered as it may have the dominating effect on the system.<br>Master of Science
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Yang, Gang. "Design of a High Efficiency High Power Density DC/DC Converter for Low Voltage Power Supply in Electric and Hybrid Vehicles." Thesis, Supélec, 2014. http://www.theses.fr/2014SUPL0011/document.
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Cette thèse traite de la conception d’un convertisseur DC / DC destiné aux véhicules électriques et hybrides (2,5 kW, 400V/14V, 250kHz). Dérivé de la topologie LLC à résonance, ce convertisseur bénéficie des nombreux avantages propres à cette structure particulière. C’est ainsi que le prototype réalisé présente un rendement très élevé, une densité de puissance très forte avec des perturbations EMI très réduites. La première partie de cette thèse est consacrée à l’analyse théorique du circuit LLC afin de dégager un modèle de conversion et une stratégie de contrôle adaptée à l’application visée. Afin de conserver un rendement important sur une large plage de charge, une structure basée sur la mise en parallèle de deux modules LLC est proposée. Une nouvelle stratégie de contrôle à deux boucles est également proposée pour équilibrer le courant entre les deux modules. La seconde partie de la thèse fait appel à la simulation et à l’expérimentation. Il s’agit de minimiser la masse et l’encombrement tout en maximisant le rendement. Un composant magnétique spécial est conçu puis dimensionné pour intégrer le transformateur et diverses inductances de résonance. Ce convertisseur met également en œuvre un système de redressement synchrone robuste avec une compensation de phase, un module de puissance avec une résistance thermique très faible et un système de refroidissement efficace par air. Le rendement maximal mesuré est 95%. Le rendement demeure supérieur à 94% sur une plage de puissance s’étalant de 500 W à 2 kW. La densité de puissance est 1W/cm3. La CEM du convertisseur est développée dans cette thèse<br>In this dissertation, a 2.5kW 400V/14V, 250kHz DC/DC converter prototype is developed targeted for electric vehicle/hybrid vehicle applications. Benefiting from numerous advantages brought by LLC resonant topology, this converter is able to perform high efficiency, high power density and low EMI. A first part of this dissertation is the theoretical analysis of LLC: topology analysis, electrical parameter calculation and control strategy. To arrange high output current, this thesis proposes parallel connected LLC structure with developed novel double loop control to realize an equal current distribution. The second part concerns on the system amelioration and efficiency improvement of developed LLC. A special transformer is dimensioned to integrate all magnetic components, and various types of power losses are quantified based on different realization modes and winding geometries to improve its efficiency. This converter also implements a robust synchronous rectification system with phase compensation, a power semiconductor module, and an air-cooling system. The power conversion performance of this prototype is presented and the developed prototype has a peak efficiency of 95% and efficiency is higher than 94% from 500W to 2kW, with a power density of 1W/cm3. The CEM analysis of this converter is also developed in this thesis
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Samir, Anass. "Conception de solutions basses puissances et optimisation de la gestion d'énergie de circuits dédiés aux applications mixtes." Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM4700.
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Depuis trois décennies, la tendance du marché répond à la demande actuelle de miniaturisation et d'augmentation de performances des appareils multimédias. Or, toute réduction des dimensions d'un facteur donné impose une diminution des tensions (pour des raisons de fiabilité). Afin d'y répondre, la réduction de taille des circuits intégrés CMOS atteint des échelles d'intégration submicroniques entrainant une baisse importante de la fiabilité des composants et en particulier des transistors. La création de porteurs chauds, ainsi que la dissipation thermique à l'intérieur des circuits submicroniques, sont les deux phénomènes physiques principaux à l'origine de la baisse de fiabilité. La solution technique permettant de garder un bon degré de fiabilité, tout en réduisant la taille des composants, consiste à réduire la tension d'alimentation des circuits. Parallèlement aux contraintes de performances, les normes environnementales demandent une consommation la plus réduite possible. La difficulté consiste alors en la réalisation de circuits associant une alimentation basse puissance (tension et courant) d'où la notion de circuits " Low Power ". Ces circuits sont pour certains déjà utilisés dans le domaine du multimédia, du médical, avec des contraintes d'intégration différentes (possibilité de composants externes, stabilité, etc.). L'augmentation des performances en vitesse des circuits digitaux nécessite par ailleurs l'utilisation de technologies générant des fuites de plus en plus importantes qui sont incompatibles avec une réduction de la consommation dans des modes de veille sans la mise en place de nouvelles techniques<br>For three decades, the market trend answers the current demand of miniaturization and performance increase of the multimedia devices. Yet, any reduction of the dimensions of a given factor imposes a decrease of the tensions (for reasons of reliability). To answer this question, the downsizing of CMOS integrated circuits reaches submicron scales of integration resulting in a significant decrease in the reliability of components and in particular transistors. The hot carriers creations, as well as heat dissipation within the submicron circuits, are the two main physical phenomena behind the reliability decline. The technical solution to maintain a good degree of reliability, while reducing component size, is to reduce the supply voltage of circuits. In parallel to performance constraints, environmental standards require consumption as small as possible. The challenge is then to build circuits combining low power supply (voltage and current) where the concept of circuits "Low Power". These circuits are used for some already in the field of multimedia, medical, integration with various constraints (possibility of external components, stability, etc..). The speed increase performance of digital circuits also requires the use of technologies that generate leaks increasingly important that are inconsistent with consumption reduction in standby modes without the introduction of new techniques
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Saini, Dalvir K. "Gallium Nitride: Analysis of Physical Properties and Performance in High-Frequency Power Electronic Circuits." Wright State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=wright1438013888.
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Wang, Xiangcheng. "HIGH SLEW RATE HIGH-EFFICIENCY DC-DC CONVERTER." Doctoral diss., University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3196.
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Active transient voltage compensator (ATVC) has been proposed to improve VR transient response at high slew rate load, which engages in transient periods operating in MHZ to inject high slew rate current in step up load and recovers energy in step down load. Main VR operates in low switching frequency mainly providing DC current. Parallel ATVC has largely reduced conduction and switching losses. Parallel ATVC also reduces the number of VR bulk capacitors. Combined linear and adaptive nonlinear control has been proposed to reduce delay times in the actual controller, which injects one nonlinear signal in transient periods and simplifies the linear controller design. Switching mode current compensator with nonlinear control in secondary side is proposed to eliminate the effect of opotocoupler, which reduces response times and simplifies the linear controller design in isolated DC-DC converters. A novel control method has been carried out in two-stage isolated DC-DC converter to simplify the control scheme and improve the transient response, allowing for high duty cycle operation and large step-down voltage ratio with high efficiency. A balancing winding network composed of small power rating components is used to mitigate the double pole-zero effect in complementary-controlled isolated DC-DC converter, which simplifies the linear control design and improves the transient response without delay time. A parallel post regulator (PPR) is proposed for wide range input isolated DC-DC converter with secondary side control, which provides small part of output power and most of them are handled by unregulated rectifier with high efficiency. PPR is easy to achieve ZVS in primary side both in wide range input and full load range due to 0.5 duty cycle. PPR has reduced conduction loss and reduced voltage rating in the secondary side due to high turn ratio transformer, resulting in up to 8 percent efficiency improvement in the prototype compared to conventional methods.<br>Ph.D.<br>School of Electrical Engineering and Computer Science<br>Engineering and Computer Science<br>Electrical Engineering
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Li, Yanchao. "High Power Density and High Efficiency DC-DC Converters." Diss., North Dakota State University, 2018. https://hdl.handle.net/10365/28879.
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Rahimi, Arian. "Design And Implementation Of Low Power Interface Electronics For Vibration-based Electromagnetic Energy Harvesters." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613820/index.pdf.
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For many years batteries have been used as the main power sources for portable electronic devices. However, the rate of scaling in integrated circuits and micro-electro-mechanical systems (MEMS) has been much higher than that of the batteries technology. Therefore, a need to replace these temporary energy reservoirs with small sized continuously charged energy supply units has emerged. These units, named as energy harvesters, use several types of ambient energy sources such as heat, light, and vibration to provide energy to intelligent systems such as sensor nodes. Among the available types, vibration based electromagnetic (EM) energy harvesters are particularly interesting because of their simple structure and suitability for operation at low frequency values (<<br>10 Hz), where most vibrations exits. However, since the generated EM power and voltage is relatively low at low frequencies, high performance interface electronics is required for efficiently transferring the generated power from the harvester to the load to be supplied.
The aim of this study is to design low power and efficient interface electronics to convert the low voltage and low power generated signals of the EM energy harvesters to DC to be usable by a real application. The most critical part of such interface electronics is the AC/DC converter, since all the other blocks such as DC/DC converters, power managements units, etc. rely on the rectified voltage generated by this block. Due to this, several state-of-the-art rectifier structures suitable for energy harvesting applications have been studied. Most of the previously proposed rectifiers have low conversion efficiency due to the high voltage drop across the utilized diodes. In this study, two rectifier structures are proposed: one is a new passive rectifier using the Boot Strapping technique for reducing the diode turn-on voltage values<br>the other structure is a comparator-based ultra low power active rectifier. The proposed structures and some of the previously reported designs have been implemented in X-FAB 0.35 µ<br>m standard CMOS process. The autonomous energy harvesting systems are then realized by integrating the developed ASICs and the previously proposed EM energy harvester modules developed in our research group, and these systems have been characterized under different electromechanical excitation conditions. In this thesis, five different systems utilizing different circuits and energy harvesting modules have been presented. Among these, the system utilizing the novel Boot Strap Rectifier is implemented within a volume of 21 cm3, and delivers 1.6 V, 80 µ<br>A (128 µ<br>W) DC power to a load at a vibration frequency of only 2 Hz and 72 mg peak acceleration. The maximum overall power density of the system operating at 2 Hz is 6.1 µ<br>W/cm3, which is the highest reported value in the literature at this operation frequency. Also, the operation of a commercially available temperature sensor using the provided power of the energy harvester has been shown. Another system utilizing the comparator-based active rectifier implemented with a volume of 16 cm3, has a dual rail output and is able to drive a 1.46 V, 37 µ<br>A load with a maximum power density of 6.03 µ<br>W/cm3, operating at 8 Hz.
Furthermore, a signal conditioning system for EM energy harvesting has also been designed and simulated in TSMC 90 nm CMOS process. The proposed ASIC includes a highly efficient AC-DC converter as well as a power processing unit which steps up and regulates the converted DC voltages using an on-chip DC/DC converter and a sub-threshold voltage regulator with an ultra low power management unit. The total power consumption on the totally passive IC is less than 5 µ<br>W, which makes it suitable for next generation MEMS-based EM energy harvesters.
In the frame of this study, high efficiency CMOS rectifier ICs have been designed and tested together with several vibration based EM energy harvester modules. The results show that the best efficiency and power density values have been achieved with the proposed energy harvesting systems, within the low frequency range, to the best of our knowledge. It is also shown that further improvement of the results is possible with the utilization of a more advanced CMOS technology.
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Liu, Yushi. "Low Profile, High Power Density and High Efficiency DC-DC Converters." Thesis, University of Colorado at Boulder, 2019. http://pqdtopen.proquest.com/#viewpdf?dispub=10980034.
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<p> Due to the ever decreasing thickness and increasing battery size of modern cellphones, battery chargers inside cellphones are required to meet increasingly stringent power density requirements, including small printed circuit board (PCB) area and component height. This thesis is focused on low-profile, high-power-density, and high-efficiency dc-dc converters for battery charging applications. </p><p> This thesis investigates five topologies, including ZVS-QSW buck converter, three-level buck converter, four-level buck converter, a resonant switched capacitor converter, and a new reconfigurable hybrid switched capacitor converter. The operation principle of each topology is described, and the advantages and disadvantages of each topology are analyzed and compared in terms of efficiency and power density. To accurately evaluate the performance of each topology, this thesis utilizes the augmented state-space modeling method that efficiently calculates the steady-state waveforms of a converter. To accurately predict losses, the dynamic on-resistance of GaN transistors and core loss of inductors have been modeled. Furthermore, a comprehensive optimization methodology is utilized to select circuit and component parameters. </p><p> For 2:1 conversation ratio application scenario, two prototypes using GaN transistors and low-voltage Silicon MOSFET have been designed, built and tested for an input voltage range of 5 V to 20 V, an output voltage range of 3 V to 4.2 V, and a maximum output current of 10 A. The prototype with GaN transistors (EPC2023) occupies a PCB area of 358 mm<sup>2</sup> with component height of 1 mm. To maximize efficiency, the converter is designed to achieve ZVS at light-to-medium loads, while sacrificing ZVS to reduce transistor conduction and inductor losses. This prototype converter achieves a peak efficiency of 98.5%. The prototype using low-voltage Silicon MOSFET (CPF03433) occupies a PCB area of 310 mm<sup>2</sup>. A prototype of four-level buck converter with a PCB area of 410 mm<sup>2</sup>, optimized for 3:1 conversion ratio, has also been built and tested. For extreme-power-density application, a prototype with a PCB area of 79.6 mm<sup>2</sup> and component height of 1 mm is built and tested. The prototype converter achieves a peak efficiency of 96.7% and a power density of 3230 W/in<sup>3</sup>.</p><p>
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Ahmed, Oday Ali. "Investigation into high efficiency DC-DC converter topologies for a DC microgrid system." Thesis, University of Leicester, 2012. http://hdl.handle.net/2381/10165.
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Distributed generation in the form of DC microgrids has recently attracted increasing research interest. For integrating primary sources and energy storage devices to the DC bus of a DC microgrid power electronic converters are necessary, but the associated losses may degrade the microgrid efficiency. Therefore, the aim of this work is to develop high-efficiency converters, particularly for fuel cell generators and ultracapacitors energy buffers suitable for use in a stationary distribution system. Based on the evaluation of the fuel cell dynamic performance, a current–fed DC–DC converter design with a lower voltage rating of the switching devices and a higher DC voltage conversion ratio is proposed. A number of optimisation approaches have been applied to further improve the converter efficiency over its full power range. The periodic steady state operation of the converter is analysed in detail; state-space averaging is then used to determine the small signal equations and derive transfer functions. A closed loop controller has been designed and verified by a novel PSpice/Simulink/actual processor co–simulation approach, where the modelling results are validated by experimental results using a model–based design method. To sustain the charging and discharging states of the ultracapacitor, a bidirectional DC–DC converter is required. Based on a comprehensive overview on different DC–DC converter topologies, the research presented here has shown that, bidirectional voltage–fed topology is better suited for dealing with the fast dynamic response of the ultracapacitor. But for a wide input voltage variation, this topology exhibits a higher circulating power flow and higher conduction losses as a consequence. Therefore, a detailed analysis of the bidirectional converter exploring the impact of the circulating power flow interval is developed in this study. Analytic methods have been applied to establish the optimal operation of the bidirectional voltage–fed converter for an ultracapacitor to improve its performance and efficiency. Based on these methods, a novel modulation scheme is proposed that minimises the circulating power flow in the converter, that has been verified by detailed simulation.
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Inam, Wardah. "High efficiency resonant dc/dc converter for solar power applications." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/79153.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2013.<br>This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.<br>Cataloged from student-submitted PDF version of thesis.<br>Includes bibliographical references (p. 109).<br>This thesis presents a new topology for a high efficiency dc/dc resonant power converter that utilizes a resistance compression network to provide simultaneous zero voltage switching and near zero current switching across a wide range of input voltage, output voltage and power level. The resistance compression network maintains desired current waveforms over a wide range of voltage operating conditions. The use of on/off control in conjunction with narrowband frequency control enables high efficiency to be maintained across a wide range of power levels. The converter implementation provides galvanic isolation and enables large (greater than 1:10) voltage conversion ratios, making the system suitable for large step-up conversion in applications such as distributed photovoltaic converters. Three 200 W prototypes were designed, built and tested. The first prototype was made as a proof of concept and operated at a switching frequency of 100 kHz. It had an efficiency of 93.5% (at 25 V input and 400 V output). The second prototype was operated at a switching frequency of 500 kHz and had an efficiency of 93% (at 25 V input and 400 V output). The high frequency losses caused by the ringing in voltage and current due to the resonating parasitics of the transformer were removed with the help of a matching network in the third prototype. This final prototype operated at a switching frequency of 500 kHz and showed that over 95% efficiency is maintained across an input voltage range of 25 V - 40 V (at 400 V output) and over 93.7 % efficiency across a wide output voltage range of 250 V - 400 V (at 25 V input). These experimental results demonstrated the effectiveness of the proposed design.<br>by Wardah Inam.<br>S.M.
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Bretz, Joshua Harlen 1974. "DC-DC converters with high efficiency over wide load ranges." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/9721.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1999.<br>Includes bibliographical references (leaf 63).<br>An integrated switching regulator is presented, including theory of operation, circuit design, and test results. This DC-DC converter introduces several novel circuits which enable more efficient operation at output powers from l00J.1W to lW. Efficiency above 80% is achieved from 500JlW to 500mW. Specifically, depending on the load current, the regulator automatically switches between Pulse Frequency Modulation (PPM) and Pulse Width Modulation (PWM), and also automatically selects the optimum switching MOSFET. The current sensing is done without an additional current sense resistor. PFM mode operation is synchronous to allow sampled data systems to avoid sampling on switching transitions. In all modes of operation, the regulator output voltage is digitally programmable. This enables variable voltage architectures, in which the power supply of a digital system is dynamically changed depending on the throughput requirements, resulting in significant power reductions.<br>by Joshua Harlen Bretz.<br>S.M.
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Muhammad, Musbahu. "High gain non-isolated DC-DC converter topologies for energy conversion systems." Thesis, University of Newcastle upon Tyne, 2017. http://hdl.handle.net/10443/3665.
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Emerging applications driven by low voltage level power sources, such as photovoltaics, batteries and fuel cells require static power converters for appropriate energy conversion and conditioning to supply the requirements of the load system. Increasingly, for applications such as grid connected inverters, uninterruptible power supplies (UPS), and electric vehicles (EV), the performance of a high efficiency high static gain power converter is of critical importance to the overall system. Theoretically, the conventional boost and buck-boost converters are the simplest non-isolated topologies for voltage step-up. However, these converters typically operate under extreme duty ratio, and severe output diode reverse recovery related losses to achieve high voltage gain. This thesis presents derivation, analysis and design issues of advanced high step-up topologies with coupled inductor and voltage gain extension cell. The proposed innovative solution can achieve significant performance improvement compared to the recently proposed state of the art topologies. Two unique topologies employing coupled inductor and voltage gain extension cell are proposed. Power converters utilising coupled inductors traditionally require a clamp circuit to limit the switch voltage excursion. Firstly, a simple low-cost, high step-up converters employing active and passive clamp scheme is proposed. Performance comparison of the clamps circuits shows that the active clamp solution can achieve higher efficiency over the passive solution. Secondly, the primary detriment of increasing the power level of a coupled inductor based converters is high current ripple due to coupled inductor operation. It is normal to interleaved DC-DC converters to share the input current, minimize the current ripple and increase the power density. This thesis presents an input parallel output series converter integrating coupled inductors and switched capacitor demonstrating high static gain. Steady state analysis of the converter is presented to determine the power flow equations. Dynamic analysis is performed to design a closed loop controller to regulate the output voltage of the interleaved converter. The design procedure of the high step-up converters is explained, simulation and experimental results of the laboratory prototypes are presented. The experimental results obtained via a 250 W single phase converter and that of a 500 W interleaved converter prototypes; validate both the theory and operational characteristics of each power converter.
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Manh, Vir Varinder. "An Integrated High Efficiency DC-DC Converter in 65 nm CMOS." Thesis, Linköpings universitet, Elektroniksystem, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-61237.
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This thesis work describes the implementation perspective of an integrated high efficiency DC-DC converter implemented in 65 nm CMOS. The implemented system employs the Buck converter topology to down-convert the input battery voltages. This converter offers its use as a power management unit in portable battery operated devices. This thesis work includes the description of a basic Buck converter along with the various key equations involved which describe the Buck operation as well as are used to deduce the requirements for the various internal building blocks of the system. A detailed description of the operation as well as the design of each of the building blocks is included. The implemented system can convert the input battery voltage in the range of 2.3 V to 3.6 V into an output supply voltage of 1.6 V. The system uses dual-mode feedback control to maintain the output voltage at 1.6 V. For the low load currents the PFM feedback control is used and for the higher load currents the PWM feedback control is used. This converter can supply load currents from 0 to 300 mA with efficiency above 85%. The static line regulation of the system is < 0.1% and the load regulation of the system is < 0.3%. A digital soft-start circuit is implemented in this system. The system also includes the capability to trim the output voltage in ~14 mV steps depending on the 4-bit input digital code.
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Li, Yanchao. "High Power Density and High Efficiency DC-DC Converters Based on Wide Bandgap Semiconductors." Diss., North Dakota State University, 2019. https://hdl.handle.net/10365/32074.
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As the rapid development of semiconductor technologies, more and more power electronic devices are used in our daily life. The power converters are widely used in many emerging areas, such as renewable energy and clean electricity area, information technology (IT) area and transportation area. Due to the high power usage in all these areas, make the power converter highly efficient is becoming more important than ever. Also, high-density power converters are highly desired in more and more applications. Soft-switching technology is one of the key points that help us to achieve the goals. In this research work, a series of soft-switching power converters are presented and analyzed.
First, a modular multilevel converter (MMC) with zero-current switching capability is proposed. By using different control method, the converter can achieve different voltage conversion ratios. Another attractive feature of the proposed MMC is that it can fully utilize the parasitic inductance existed in the converter system.
Second, high power-density switched-capacitor converters start appearing in many emerging applications. On the one hand, the research proposed a multilevel switched-capacitor converter that is capable of zero-voltage switching (ZVS) and voltage regulation. On the other hand, a switched-tank converter with zero-current switching (ZCS) has been studied. Furthermore, adaptive control method has been proposed to solve the issues that are led by component tolerance during the mass production procedure. Besides, a comparison study of the two operation modes is performed. Also, a composite multilevel converter based on switched-capacitor concept has been developed for telecommunication application.
Finally, a 100kW switched-tank converter has been developed to validate that the high power- density and high-efficiency can be achieved by using the switched-capacitor concept.
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Wang, Kunrong. "High-Frequency Quasi-Single-Stage (QSS) Isolated AC-DC and DC-AC Power Conversion." Diss., Virginia Tech, 1998. http://hdl.handle.net/10919/29394.
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The generic concept of quasi-single-stage (QSS) power conversion topology for ac-dc rectification and dc-ac inversion is proposed. The topology is reached by direct cascading and synchronized switching of two variety of buck or two variety of boost switching networks. The family of QSS power converters feature single-stage power processing without a dc-link low-pass filter, a unidirectional pulsating dc-link voltage, soft-switching capability with minimal extra commutation circuitry, simple PWM control, and high efficiency and reliability.
A new soft-switched single-phase QSS bi-directional inverter/rectifier (charger) topology is derived based on the QSS power conversion concept. A simple active voltage clamp branch is used to clamp the otherwise high transient voltage on the current-fed ac side, and at the same time, to achieve zero-voltage-switching (ZVS) for the switches in the output side bridge. Seamless four-quadrant operation in the inverter mode, and rectifier operation with unity power factor in the charger (rectifier) mode are realized with the proposed uni-polar center-aligned PWM scheme. Single-stage power conversion, standard half-bridge connection of devices, soft-switching for all the power devices, low conduction loss, simple center-aligned PWM control, and high reliability and efficiency are among its salient features. Experimental results on a 3 kVA bi-directional inverter/rectifier prototype validate the reliable operation of the circuit. Other single-phase and three-phase QSS bi-directional inverters/rectifiers can be easily derived as topological extensions of the basic QSS bi-directional inverter/rectifier.
A new QSS isolated three-phase zero-voltage/zero-current-switching (ZVZCS) buck PWM rectifier for high-power off-line applications is also proposed. It consists of a three-phase buck bridge switching under zero current and a phase-shift-controlled full-bridge with ZVZCS, while no intermediate dc-link is involved. Input power and displacement factor control, input current shaping, tight output voltage regulation, high-frequency transformer isolation, and soft-switching for all the power devices are realized in a unified single stage. Because of ZVZCS and single-stage power conversion, it can operate at high switching frequency while maintaining reliable operation and achieving higher efficiency than standard two-stage approaches. A family of isolated ZVZCS buck rectifiers are obtained by incorporating various ZVZCS schemes for full-bridge dc-dc converters into the basic QSS isolated buck rectifier topology. Experimental and simulation results substantiate the reliable operation and high efficiency of selected topologies.
The concept of charge control (or instantaneous average current control) of three-phase buck PWM rectifiers is introduced. It controls precisely the average input phase currents to track the input phase voltages by sensing and integrating only the dc rail current, realizes six-step PWM, and features simple implementation, fast dynamic response, excellent noise immunity, and is easy to realize with analog circuitry or to integrate. One particular merit of the scheme is its capability to correct any duty-cycle distortion incurred on only one of the two active duty-cycles which often happens in the soft-switched buck rectifiers, another merit is the smooth transition of the input currents between the 60o sectors. Simulation and preliminary experimental results show that smooth operations and high quality sinusoidal input currents in the full line cycle are achieved with the control scheme.<br>Ph. D.
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Shahin, Ahmed Eid Moussa. "Contribution à l’optimisation des structures de conversion DC/DC non isolées." Thesis, Vandoeuvre-les-Nancy, INPL, 2011. http://www.theses.fr/2011INPL045N/document.
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Dans ce mémoire, nous avons étudié les convertisseurs d’interface permettant l’interconnexion d’une source basse tension non linéaire et d’un bus DC moyenne tension. La source choisie, pour l’étude, était une pile à combustible de type PEM. La structure de puissance retenue correspondant à la mise en cascade d’un convertisseur entrelacé en entrée et d’un convertisseur trois niveaux en sortie. Afin de dimensionner au mieux le convertisseur global, nous avons proposé un modèle analytique permettant de connaitre l’ensemble des pertes dans le système en fonction du point de fonctionnement et de ses paramètres. Nous avons montré que l’ensemble des pertes dans le convertisseur peut être modélisé par deux résistances non linéaires dont l’estimation est possible à partir des modèles moyens du convertisseur. Une commande basée sur le concept de platitude des systèmes différentiels a été utilisée pour assurer les différentes contraintes du système tout en obtenant des propriétés dynamiques élevées en asservissement et en régulation. Dans la dernière partie du mémoire, nous nous sommes intéressés aux solutions permettant de satisfaire les contraintes sur le taux d’ondulation de courant en entrée du convertisseur. Nous avons proposé et dimensionné une nouvelle structure de convertisseur permettant de supprimer les ondulations de courant générées par le convertisseur de puissance. Ce filtre actif se connecte en parallèle avec le convertisseur de puissance. Des résultats expérimentaux ont permis de montrer que le taux d’ondulation de courant d’un convertisseur élévateur a été réduit, le taux d’ondulation de courant passant de 23.3% à 1.9%<br>In this thesis, we studied interface converters enabling the interconnection of a low voltage nonlinear source and a medium voltage DC bus. The source selected for the study was a fuel cell PEM. The chosen power architecture corresponds to a cascaded structure constituted with an interleaved Boost converter at input stage and a three-level Boost converter at output stage. To design the converter, we proposed an analytical model to know the total losses in the system according to the operating point and its parameters. We showed that all losses in the converter can be modeled by two nonlinear resistors. An estimation of these resistors, deduced from average model of the converter, is developed. A control based on the concept of differential systems flatness has been used for the proposed converter structure. It allows taking into account the different system constraints. High dynamic properties as regard to external perturbations or parameters variations are achieved. In the last part of the thesis, we investigate solutions to respect the constraints on the rate of input current ripple. We propose a new active filtering converter connected in parallel with the power one. We have shown that the ripple current of a boost converter was reduced, the ripple current being reduced from 23.3% to 1.9%
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Elmes, John. "High-density and high-efficiency soft switching modular bi-directional dc-dc converter for hybrid electric vehicles." Doctoral diss., University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4589.
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This dissertation presents the design of a high-density and high-efficiency soft-switching bi-directional DC-DC converter for hybrid-electric vehicles. The converter operates in a new bi-directional interleaved variable-frequency quasi-square-wave (QSW) mode, which enables high efficiency, high switching frequency, and high power-density. The converter presented utilizes a new variable frequency interleaving approach which allows for each module to operate in an interleaved position while allowing for tolerance in inductance and snubber capacitor values. The variable frequency interleaved soft-switching operation paired with a high-density nanocrystalline inductor and high-density system structure results in a very high performance converter, well exceeding that of the current technology. The developed converter is intended to achieve three specific performance goals: high conversion efficiency, high power density, and operation with 100 ???????°C coolant. Two markedly different converter prototype designs are presented, one converter using evaporative spray cooling to cool the switching devices, with the second converter using a more traditional coldplate design to cool the switching devices. The 200 kW (25 kW per module) prototype converters exhibited power density greater than 8 kilowatts/liter (kW/L), and peak efficiency over 98%, while operating with 100 ???????°C coolant.<br>ID: 028730758; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Thesis (Ph.D.)--University of Central Florida, 2010.; Includes bibliographical references.<br>Ph.D.<br>Doctorate<br>School of Electrical Engineering and Computer Science<br>Engineering and Computer Science<br>Electrical Engineering
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Liu, Changrong. "A Novel High-Power High-Efficiency Three-Phase Phase-Shift DC/DC Converter for Fuel Cell Applications." Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/26048.
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Fuel cells are a clean, high-efficiency source for power generation. This innovative technology is going to penetrate all aspects in our life, from utility distributed power, transportation applications, down to power sources for portable devices such as laptop computer and cell phones. To enable the usage of fuel cell, developing power converters dedicated for fuel cells becomes imminent.
Currently, the full-bridge converter is the dominating topology in high power dc/dc applications. Although multiphase converters have been proposed, most of them are dealing with high input-voltage systems, and their device characteristic is not suitable for a low voltage source such as a fuel cell. For a high power fuel cell system, high voltage conversion ratios and high input currents are the major obstacles to achieving high-efficiency power conversions. This dissertation proposes a novel 3-phase 6-leg dc/dc power converter with transformer isolation to overcome these obstacles. Major features of the proposed converter include: (1) Increase converter power rating by paralleling phases, not by paralleling multiple devices; (2) Double the output voltage by transformer delta-wye connection, thus lowering the turns-ratio; (3) Reduce the size of output filter and input dc bus capacitor with interleaved control; (4) Achieve Zero-Voltage Zero-Current Switching (ZVZCS) over a wide load range without auxiliary circuitry. High conversion efficiency above 96% is verified with different measurement approaches in experiments.
This dissertation also presents the power stage and control design for the proposed converter. Control design guideline is provided and the design result is confirmed with both simulation and hardware experiments. When using the fuel cell for stationary utility power applications, a low-frequency ripple interaction was identified among fuel cell, dc/dc converter and dc/ac inverter. This low frequency ripple tends to not only damage the fuel cell, but also reduce the source capability. This dissertation also investigates the mechanism of ripple current propagation and exploits the solutions. A linearized ac model is derived and used to explain the ripple propagation. An active ripple reduction technique by the use of the current loop control is proposed. This active current loop control does not add extra converters or expensive energy storage components. Rather, it allows a reduction in capacitance because the ripple current flowing into the capacitor is substantially reduced, and less capacitance can be used while maintaining a clean dc bus voltage. The design process and guideline for the proposed control is suggested, and the effectiveness of this active control is validated by both simulation and experimental results.<br>Ph. D.
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Xiong, Yali. "MODELING AND ANALYSIS OF POWER MOSFETS FOR HIGH FREQUENCY DC-DC CONVERTERS." Doctoral diss., University of Central Florida, 2008. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3589.
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Evolutions in integrated circuit technology require the use of a high-frequency synchronous buck converter in order to achieve low cost, low profile, fast transient response and high power density. However, high frequency operation leads to increased power MOSFET switching losses. Optimization of the MOSFETs plays an important role in improving converter performance. This dissertation focuses on revealing the power loss mechanism of power MOSFETs and the relationship between power MOSFET structure and its power loss. The analytical device model, combined with circuit modeling, cannot reveal the relationship between device structure and its power loss due to the highly non-linear characteristics of power MOSFETs. A physically-based mixed device/circuit modeling approach is used to investigate the power losses of the MOSFETs under different operating conditions. The physically based device model, combined with SPICE-like circuit simulation, provides an expeditious and inexpensive way of evaluating and optimizing circuit and device concepts. Unlike analytical or other SPICE models of power MOSFETs, the numerical device model, relying little on approximations or simplifications, faithfully represents the behavior of realistic power MOSFETs. The impact of power MOSFET parameters on efficiency of synchronous buck converters, such as gate charge, on resistance, reverse recovery, is studied in detail in this thesis. The results provide a good indication on how to optimize power MOSFETs used in VRMs. The synchronous rectifier plays an important role in determining the performance of the synchronous buck converter. The reverse recovery of its body diode and the Cdv/dt induced false trigger-on are two major mechanisms that impact SyncFET's performance. This thesis gives a detailed analysis of the SyncFET operation mechanism and provides several techniques to reduce its body-diode influence and suppress its false Cdv/dt trigger-n. This thesis also investigates the influence of several circuit level parameters on the efficiency of the synchronous buck converter, such as input voltage, circuit parasitic inductance, and gate resistance to provide further optimization of synchronous buck converter design.<br>Ph.D.<br>School of Electrical Engineering and Computer Science<br>Engineering and Computer Science<br>Electrical Engineering PhD
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Wan, Hongmei. "High Efficiency DC-DC Converter for EV Battery Charger Using Hybrid Resonant and PWM Technique." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/32343.
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The battery charger plays an important role in the development of electric vehicles (EVs) and plug-in hybrid electric vehicles (PHEVs).This thesis focuses on the DC-DC converter for high voltage battery charger and is divided into four chapters. The background related to EV battery charger is introduced, and the topologies of isolated DC-DC converter possibly applied in battery charge are sketched in Chapter 1. Since the EV battery charger is high voltage high power, the phase-shifted full bridge and LLC converters, which are popularly used in high power applications, are discussed in detail in Chapter 2. They are generally considered as high efficiency, high power density and high reliability, but their prominent features are also limited in certain range of operation. To make full use of the advantages and to avoid the limitation of the phase-shifted full bridge and LLC converters, a novel hybrid resonant and PWM converter combining resonant LLC half-bridge and phase shifted full-bridge topology is proposed and is described in Chapter 3. The converter achieves high efficiency and true soft switching for the entire operation range, which is very important for high voltage EV battery charger application. A 3.4 kW hardware prototype has been designed, implemented and tested to verify that the proposed hybrid converter truly avoids the disadvantages of LLC and phase-shifted full bridge converters while maintaining their advantages. In this proposed hybrid converter, the utilization efficiency of the auxiliary transformer is not that ideal. When the duty cycle is large, LLC converter charges one of the capacitors but the energy stored in the capacitor has no chance to be transferred to the output, resulting in the low utilization efficiency of the auxiliary transformer. To utilize the auxiliary transformer fully while keeping all the prominent features of the previous hybrid converter in Chapter 3, an improved hybrid resonant and PWM converter is proposed in Chapter 4. The idea has been verified with simulations. The last chapter is the conclusion which summaries the key features and findings of the two proposed hybrid converters.<br>Master of Science
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Al-Mothafar, M. R. D. "High frequency inverter-cycloconverter system for DC to AC conversion." Thesis, University of Bath, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378135.
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Sternberg, Kyle Matthew. "High power, high efficiency, low cost DC/DC converters for laser test equipment and residential fuel cell applications." Thesis, Montana State University, 2009. http://etd.lib.montana.edu/etd/2009/sternberg/SternbergK1209.pdf.
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In this work two low cost, high efficiency, high power DC/DC converters are developed. The first converter is targeted for industrial laser applications. The converter is designed for a 400 volt input voltage and a 0-36V output voltage and 0-40A output with a maximum power output of 1500 watts at a cost less than $0.30 / watt. To achieve a high efficiency and low cost at this power level a zero-voltage switched full bridge converter is used. This technology increases the efficiency of the converter past 90% while reducing the size of the components. The converter was built and tested and achieved a 91.5% efficiency at full load. The total cost was $0.28 / watt. This converter met all the design goals while exceeding the cost goals. The second converter is targeted for residential fuel cell applications. This converter utilizes the technology developed for the industrial converter. This residential converter is designed for an input of 26-42 volts at 190 amps and an output of 400 volts and 12 amps at a power level of 5000 watts while maintaining a $40/kilowatt cost goal. To achieve the low cost and high efficiency design goals the converter uses several technologies in its construction. Like the converter for industrial applications this converter utilizes zero voltage switching full bridge converter. To compensate for the high input current a unique multiphase design was designed for the application. A unique parallel input / series output topology and three interleaved converters split the input current to increase the efficiency of the converter. This unique topology increases the switching frequency on the secondary side which reduces the side of the passive components, reducing cost. The converter was built and tested at a light load to verify its operation versus the theory. An estimated 96% efficiency at full load is possible using this topology. The total cost was $39 / kilowatt.
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Trubitsyn, Aleksey. "High efficiency DC/AC power converter for photovoltaic applications." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/60190.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2010.<br>Includes bibliographical references (p. 217-218).<br>This thesis presents the development of a microinverter for single-phase photovoltaic applications that is suitable for conversion from low-voltage (25-40V) DC to high voltage AC (e.g. 240VAC,RMS). The circuit topology is based on a full-bridge series resonant inverter, a high-frequency transformer, and a novel half-wave cyclo-converter. The operational characteristics are analyzed, and a multidimensional control technique is utilized to achieve high efficiency, encompassing frequency control and inverter and cyclo-converter phase shift control. An experimental prototype is demonstrated in DC/DC conversion mode for a wide range of output voltages. The proposed control strategy is shown to allow for accurate power delivery with minimal steps taken towards correction. The prototype achieves a CEC averaged efficiency of approximately 95.1%. Guidelines for optimization are presented along with experimental results which validate the method.<br>by Aleksey Trubitsyn.<br>S.M.
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Zamparette, Roger Luis Brito. "High efficiency MPPT switched capacitor DC-DC converter for photovoltaic energy harvesting aiming for IoT applications." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2017. http://hdl.handle.net/10183/173738.
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Este trabalho apresenta um conversor CC - CC baseado em Capacitores Chaveados de 6 fases e tempos intercalados com o objetivo de coletar energia fotovoltaica projetado em tecnologia CMOS de 130 nm para ser usado em aplicações em Internet das Coisas e Nós Sensores. Ele rastreia o máximo ponto de entrega de energia de um painel fotovoltaico policristalino de 3 cm x 3 cm através de modulação da frequência de chaveamento com o objetivo de carregar baterias. A razão da tensão de circuito aberto foi a estratégia de rastreio escolhida. O conversor foi projetado em uma tecnologia CMOS de 130 nm e alcança uma eficiência de 90 % para potencias de entrada maiores do que 30 mW e pode operar com tensões que vão de 1.25 até 1.8 V, resultando em saídas que vão de 2.5 até 3.6, respectivamente. Os circuitos periféricos também incluem uma proteção contra sobre tensão na saída de 3.6 V e circuitos para controle, que consomem um total máximo de potência estática de 850 A em 3.3 V de alimentação. O layout completo ocupa uma área de 300 x 700 m2 de silício. Os únicos componentes não integrados são 6x100 nF capacitores.
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Yao, Liangbin. "HIGH CURRENT DENSITY LOW VOLTAGE ISOLATED DC-DC CONVERTERSWITH FAST TRANSIENT RESPONSE." Doctoral diss., University of Central Florida, 2007. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3205.
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With the rapid development of microprocessor and semiconductor technology, industry continues to update the requirements for power supplies. For telecommunication and computing system applications, power supplies require increasing current level while the supply voltage keeps decreasing. For example, the Intel's CPU core voltage decreased from 2 volt in 1999 to 1 volt in 2005 while the supply current increased from 20A in 1999 to up to 100A in 2005. As a result, low-voltage high-current high efficiency dc-dc converters with high power-density are demanded for state-of-the-art applications and also the future applications. Half-bridge dc-dc converter with current-doubler rectification is regarded as a good topology that is suitable for high-current low-voltage applications. There are three control schemes for half-bridge dc-dc converters and in order to provide a valid unified analog model for optimal compensator design, the analog state-space modeling and small signal modeling are studied in the dissertation and unified state-space and analog small signal model are derived. In addition, the digital control gains a lot of attentions due to its flexibility and re-programmability. In this dissertation, a unified digital small signal model for half-bridge dc-dc converter with current doubler rectifier is also developed and the digital compensator based on the derived model is implemented and verified by the experiments with the TI DSP chip. In addition, although current doubler rectifier is widely used in industry, the key issue is the current sharing between two inductors. The current imbalance is well studied and solved in non-isolated multi-phase buck converters, yet few discusse this issue in the current doubler rectification topology within academia and industry. This dissertation analyze the current sharing issue in comparison with multi-phase buck and one modified current doubler rectifier topology is proposed to achieve passive current sharing. The performance is evaluated with half bridge dc-dc converter; good current sharing is achieved without additional circuitry. Due to increasing demands for high-efficiency high-power-density low-voltage high current topologies for future applications, the thermal management is challenging. Since the secondary-side conduction loss dominates the overall power loss in low-voltage high-current isolated dc-dc converters, a novel current tripler rectification topology is proposed. Theoretical analysis, comparison and experimental results verify that the proposed rectification technique has good thermal management and well-distributed power dissipation, simplified magnetic design and low copper loss for inductors and transformer. That is due to the fact that the load current is better distributed in three inductors and the rms current in transformer windings is reduced. Another challenge in telecommunication and computing applications is fast transient response of the converter to the increasing slew-rate of load current change. For instance, from Intel's roadmap, it can be observed that the current slew rate of the age regulator has dramatically increased from 25A/uS in 1999 to 400A/us in 2005. One of the solutions to achieve fast transient response is secondary-side control technique to eliminate the delay of optocoupler to increase the system bandwidth. Active-clamp half bridge dc-dc converter with secondary-side control is presented and one industry standard 16th prototype is built and tested; good efficiency and transient response are shown in the experimental section. However, one key issue for implementation of secondary-side control is start-up. A new zero-voltage-switching buck-flyback isolated dc-dc converter with synchronous rectification is proposed, and it is only suitable for start-up circuit for secondary-side controlled converter, but also for house-keeping power supplies and standalone power supplies requiring multi-outputs.<br>Ph.D.<br>School of Electrical Engineering and Computer Science<br>Engineering and Computer Science<br>Electrical Engineering PhD
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Khanna, Puneet. "High voltage conversion for MEMS applications using micromachined capacitors." [Tampa, Fla.] : University of South Florida, 2004. http://purl.fcla.edu/fcla/etd/SFE0000551.
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Miwa, Hidekazu. "High-Efficiency Low-Voltage High-Current Power Stage Design Considerations for Fuel Cell Power Conditioning Systems." Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/42519.
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Fuel cells typically produce low-voltage high-current output because their individual cell voltage is low, and it is nontrivial to balance for a high-voltage stack. In addition, the output voltage of fuel cells varies depending on load conditions. Due to the variable low voltage output, the energy produced by fuel cells typically requires power conditioning systems to transform the unregulated source energy into more useful energy format. When evaluating power conditioning systems, efficiency and reliability are critical. The power conditioning systems should be efficient in order to prevent excess waste of energy. Since loss is dissipated as heat, efficiency directly affects system reliability as well. High temperatures negatively affect system reliability. Components are much more likely to fail at high temperatures. In order to obtain excellent efficiency and system reliability, low-voltage high-current power conditioning systems should be carefully designed.
Low-voltage high-current systems require carefully designed PCB layouts and bus bars. The bus bar and PCB trace lengths should be minimized. Therefore, each needs to be designed with the other in mind. Excessive PCB and bus bar lengths can introduce parasitic inductances and resistances which are detrimental to system performance. In addition, thermal management is critical. High power systems must have sufficient cooling in order to maintain reliable operation.
Many sources of loss exist for converters. For low-voltage high-current systems, conduction loss and switching loss may be significant. Other potential non-trivial sources of loss include magnetic losses, copper losses, contact and termination losses, skin effect losses, snubber losses, capacitor equivalent series resistance (ESR) losses, and body diode related losses. Many of the losses can be avoided by carefully designing the system. Therefore, in order to optimize efficiency, the designer should be aware of which components contribute significant amounts of loss. Loss analysis may be performed in order to determine the various sources of loss. The system efficiency can be improved by optimizing components that contribute the most loss.
This thesis surveys some potential topologies suitable for low-voltage high-current systems. One low-voltage high-current system in particular is analyzed in detail. The system is called the V6, which consists of six phase legs, and is arranged as a three full-bridge phase-shift modulated converter to step-up voltage for distributed generation applications. The V6 converter has current handling requirements of up to 120A. Basic operation and performance is analyzed for the V6 converter. The loss within the V6 converter is modeled and efficiency is estimated. Calculations are compared with experimental results. Efficiency improvement through parasitic loss reduction is proposed by analyzing the losses of the V6 converter. Substantial power savings are confirmed with prototypes and experimental results. Loss analysis is utilized in order to obtain high efficiency with the V6 converter. Considerations for greater current levels of up to 400A are also discussed. The greater current handling requirements create additional system issues. When considering such high current levels, parallel devices or modules are required. Power stage design, layout, and bus bar issues due to the high current nature of the system are discussed.<br>Master of Science
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Song, Yu Jin. "Analysis and design of high frequency link power conversion systems for fuel cell power conditioning." Diss., Texas A&M University, 2004. http://hdl.handle.net/1969.1/2678.
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In this dissertation, new high frequency link power conversion systems for the fuel cell power conditioning are proposed to improve the performance and optimize the cost, size, and weight of the power conversion systems. The first study proposes a new soft switching technique for the phase-shift controlled bi-directional dc-dc converter. The described dc-dc converter employs a low profile high frequency transformer and two active full-bridge converters for bidirectional power flow capability. The proposed new soft switching technique guarantees soft switching over wide range from no load to full load without any additional circuit components. The load range for proposed soft switching technique is analyzed by mathematical approach with equivalent circuits and verified by experiments. The second study describes a boost converter cascaded high frequency link direct dc-ac converter suitable for fuel cell power sources. A new multi-loop control for a boost converter to reduce the low frequency input current harmonics drawn from the fuel cell is proposed, and a new PWM technique for the cycloconverter at the secondary to reject the low order harmonics in the output voltages is presented. The performance of the proposed scheme is verified by the various simulations and experiments, and their trade-offs are described in detail using mathematical evaluation approach. The third study proposes a current-fed high frequency link direct dc-ac converter suitable for residential fuel cell power systems. The high frequency full-bridge inverter at the primary generates sinusoidally PWM modulated current pulses with zero current switching (ZCS), and the cycloconverter at the secondary which consists of only two bidirectional switches and output filter capacitors produces sinusoidally modulated 60Hz split single phase output voltage waveforms with near zero current switching. The active harmonic filter connected to the input terminal compensates the low order input current harmonics drawn from the fuel cell without long-term energy storage devices such as batteries and super capacitors.
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Malou, Amokrane. "A study on an integrated 4-Switch Buck-Boost DC-DC converter with high efficiency for portable applications." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEI027.
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L’augmentation des performances des produits portables requièrent une exploitation la plus efficace possible de la batterie afin de permettre à ces produits d’être utilisés le plus longtemps possible avant d’être rechargés. Les circuits en aval ont besoin d’une source de tension stable qui peut varier pour chacun d’entre eux entre 1.0 V et 5.5 V à partir d’une tension d’entrée pouvant varier entre 2.5V et 5V. Un convertisseur DC-DC à 4 interrupteurs de type dévolteur-survolteur apparait comme une solution intéressante permettant des opérations de diminutions et d’augmentations de tension d’une part, et d’autres part le meilleur compromis entre rendement, performances dynamiques et coûts (en termes de place occupée sur le Silicium et sur la carte). ON Semiconductor a développé et produit un prototype en technologie CMOS 0.25 µm (procédé propriétaire) d’un tel convertisseur qui sert d’étude de cas pour la thèse. Le convertisseur opère selon plusieurs modes de fonctionnement (mode dévolteur, mode survolteur et mode dévolteur-survolteur) à cause d’un impératif de fonctionnement en fréquence de commutation fixe. Le mode dévolteur-survolteur est le sujet principal traité dans la thèse. Le mode dévolteur-survolteur, aussi appelé mode de transition, peut être implémenté via plusieurs Séquences de Topologie (SdT) possibles. Trois SdTs sont comparées en termes de rendement parmi lesquelles figure la SdT implémentée par le prototype. Les performances dynamiques du convertisseur dans ses différents mode de fonctionnement sont ensuite étudiées en dérivant les expressions analytiques des fonctions de transfert qui les caractérisent. Les modèles dérivés dans Matlab et Mathcad pour évaluer le rendement et les performances dynamiques du convertisseur sont ensuite utilisés pour développer un outil servant à obtenir un dimensionnement rapide de la boucle de contrôle du convertisseur. À partir de cette étape, la stabilité du convertisseur dans ses différents modes de fonctionnement est analysée en utilisant la théorie de Floquet et un modèle échantillonné-linéarisé du convertisseur permettant l’établissement d’une méthodologie de conception d’un tel convertisseur. Enfin, pour améliorer le rendement en mode de transition pour tous les points de fonctionnement, un algorithme contrôlant la valeur de l’hystérésis du comparateur utilisé dans la boucle de contrôle a été développé en Verilog, simulé dans l’environnement CADENCE et implémenté en FPGA. Cet algorithme peut améliorer le rendement de près de 3% en mode de transition comparé au réglage initial de la valeur d’hystérésis<br>The increase in the performances of the portable devices calls for an energy conversion from the battery that is the most efficient as possible in order to make the devices last as long as possible. The downstream circuits need a steady voltage supply which can vary for each one of them from 1.0 V to 5.5 V from an input voltage varying between 2.5 V and 5 V. A 4-Switch Buck-Boost (4SBB) DC-DC converter appears to be the solution which can perform step-up and step-down voltage perations and get the best trade-off between fficiency, dynamic performances and costs (in terms of Silicium and Board area). ON Semiconductor has developed and taped out in CMOS 0.25 µm (ON Semiconductor process) a 4SBB converter which serves as the case study of the thesis. The converter operates in multiple modes (namely Buck mode, Boost mode and Buck-Boost mode) due to fixed frequency operations. The Buck-Boost mode is the main topic dealt with in the thesis. The Buck-Boost mode, also called "transition mode", can be implemented using several possible Sequences of Topologies (SoT). Three SoTs are compared in terms of efficiency among which the one implemented in the converter. Then the dynamical performances of the converter are studied for the different modes of operations by deriving the analytical expressions of the relevant transfer functions. The models derived in Matlab and Mathcad to evaluate efficiency and dynamical performances are then used to develop a tool to get a rapid sizing of the converter’s control loop components. From this step, the stability of the converter is analyzed using Floquet’s theory and Sampled-Data modeling enabling the building of a design methodology to design such a converter. Finally, to enhance efficiency in Buck-Boost mode whatever the working conditions, an algorithm controlling the hysteresis value of the control loop’s comparator has been developed in Verilog, simulated in CADENCE and implemented in FPGA. This algorithm can improve efficiency by almost 3% in Buck-Boost mode compared to its default setting
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Pollet, Benjamin. "Convertisseurs DC-DC piézoélectrique avec stockage provisoire d’énergie sous forme mécanique." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLN045/document.
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Les convertisseurs de puissance sont de plus en plus utilisés, notamment avec l’explosion des objets nomades/connectés, certes de faibles puissance (<100 W), mais où les contraintes de volume, d’épaisseur ou de rendement sont forte. Dans ce contexte, l’utilisation des matériaux piézoélectriques constitue une excellente alternative aux convertisseurs à base d’inductances. Ces matériaux possèdent en effet de nombreux avantages comme des densités de puissances élevées, une géométrie fine et plane et sont notamment plus faciles à intégrer comparé aux inductances magnétiques classiquement utilisées. Un nouveau type de convertisseurs piézoélectrique, sans inductance, est présenté dans lequel le résonateur piézoélectrique assure une fonction de stockage d’énergie. À chaque période de résonance, le résonateur piézoélectrique prélève de l’énergie à la source d’entrée, la stocke provisoirement sous forme mécanique et la redistribue à la charge permettant ainsi la conversion de puissance. Des commutations à zéros de tension sont également garanties pour assurer des rendements élevées à fréquences élevées. Une première topologie (chapitre 2 et 3) intégrant ces principes est présentée. Un modèle analytique incluant les pertes mécaniques décrivant le comportement du convertisseur ainsi qu’un modèle de simulation sont élaborés. Le concept est validé expérimentalement et l’on obtient des rendements très élevés (jusqu’à 98%) sur une grande plage de puissance (de quelques mW à 1,8 W) pour plusieurs gains en tension (1,5 à 3). L’étude de cinq résonateurs de dimensions différentes renseigne sur l’influence de la géométrie sur les performances des convertisseurs et permet de concevoir une méthodologie de dimensionnement de ce résonateur. D’autres topologies plus complexes (chapitre 4) sont explorées et des perspectives d’améliorations et de mises sur le marché sont présentées<br>The increasing demand for power convertors in various application fields implies specific constraints and specific technological solutions. In this context, working with piezoelectric material constitutes an excellent alternative of classical inductor-based converter. Indeed, these materials enable a high-power density, thin and planar geometry and can be integrated on silicon more easily than popular wire-wound magnetic components. A new kind of piezoelectric inductorless converter, in which the piezoelectric material acts as an energy storage element, is presented. At each resonant period, the piezoelectric resonator takes energy from the input source, stores it temporarily and releases it to the load (and therefore enabling the power conversion). Soft switching is assured to maintain very high efficiencies for high frequencies. A first topology (chapter 2 and 3) in which those principles are applied is introduced. An analytical model which integrates the mechanical losses and a simulation model are developed enabling a good understanding of the converter behavior. The concept is experimentally validated and very high efficiency conversions (up to 98 %) are achieved for a large range of output power (from mW to 1.8 W) and for different output gains. The study of five different-size piezoelectric resonators enables to understand the impact of geometric parameters of the resonator on the converter performances and therefore to propose a resonator design methodology. More complex topologies are also described (chapter 4) and a discussion on improvement possibilities and perspectives to have a complete and industrialized converter concludes the thesis
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Grant, David. "High power density AC to DC conversion with reduced input current harmonics." Thesis, University of Newcastle upon Tyne, 2015. http://hdl.handle.net/10443/3906.
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This thesis investigates the bene ts and challenges arising from the use of minimal capacitance in AC to DC converters. The purpose of the research is to ultimately improve the power density and power factor of electrical systems connected to the grid. This is carried out in the con- text of a low cost brushless DC drive system operating from an o ine power supply. The work begins with a review of existing applications where it is prac- tical to use a limited amount of DC link capacitance. The vast majority of these have a load which is insensitive to supply power variations at twice the line frequency. Low performance motor drives are found to be the most prevalent, with the inertia of the rotor mitigating the e ect of torque ripple. Further research is carried out on active power factor cor- rection techniques suitable for this application, leading to the conclusion that no appropriate systems exist. A power supply is developed to enable a 24V, 200W brushless motor drive to operate from the mains. The system runs successfully using only 1μF of DC link capacitance, which causes the motor supply volt- age to have 100% ripple. It is noted that whilst this drastically reduces the low frequency input current harmonics, those occurring at the load switching frequency are greatly increased. To combat this, a novel active power factor correction system is proposed using a notch lter to detect the input current error. The common problem of voltage feedback ripple is avoided by eliminating the voltage control loop altogether. The main limitations are identi ed as a high sensitivity to load step changes and variations in line frequency. Despite this, a high power factor is maintained in all operating conditions, as well as compliance with the relevant harmonic standards.
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Steckler, Pierre-Baptiste. "Contribution à la conversion AC/DC en Haute Tension." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI075.
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Le courant alternatif (AC) se prêtant bien à la majorité des problématiques de production, de transport et de distribution de l'électricité, on comprend qu'il soit massivement utilisé. Cependant, depuis plus d'un siècle, les bénéfices du courant continu haute tension (HVDC, pour High Voltage Direct Current) pour les longues distances sont bien connus. Aux interfaces, des convertisseurs AC/DC sont requis, leur composition évoluant au fil des avancées technologiques. Après avoir présenté les spécificités du HVDC et les contraintes qu'il introduit sur les convertisseurs AC/DC, ce manuscrit se focalise sur trois topologies : Modular Multilevel Converter (MMC), Alternate Arm Converter (AAC) et Series Bridge Converter (SBC). Elles sont présentées, dimensionnées et analysées en détail, puis comparées de façon quantitative en utilisant des indicateurs de performance originaux. Il en ressort que le MMC et le SBC sont particulièrement intéressants. La méthode de commande conventionnelle du MMC est ensuite présentée et ses propriétés structurelles sont mises en évidence. Une première loi de commande originale est présentée, avec des performances similaires mais une complexité inférieure à l'état de l'art. La seconde est non linéaire, basée sur la théorie de la platitude différentielle, et permet un suivi de puissance très rapide tout en assurant la stabilité exponentielle globale du système. Ces lois de commande sont évaluées en simulation, avec un modèle moyen et un modèle détaillé intégrant 180 sous-modules par bras. La dernière partie concerne le SBC. Après l'avoir modélisé, des résultats concernant une analyse structurelle de la topologie sont présentés ainsi qu'une loi de commande originale. Le rôle fondamental du transformateur pour les convertisseurs à structure série comme le SBC est souligné. Enfin, les performances de la loi de commande proposée sont testées en simulation<br>As Alternating Current (AC) is well suited for most of the production, transmission, and distribution applications, its massive use is easy to understand. However, for over a century, the benefits of High Voltage Direct Current (HVDC) for long-distance energy transmission are well known. To connect both, AC/DC converters are mandatory, whose nature evolves with technological progress. After the problematic induced by HVDC on AC/DC converters is presented, this manuscript is focused on three topologies: Modular Multilevel Converter (MMC), Alternate Arm Converter (AAC) and Series Bridge Converter (SBC). They are presented, sized, analyzed thoroughly, and compared in quantitative terms, using original key performance indicators. It appears that MMC and SBC are particularly promising. The conventional control method of the MMC is then presented, and its structural properties are highlighted. A first original control law is presented, with similar performances but less complexity than the state-of-the-art. A second control law, non-linear and based on differential flatness theory, is introduced. It allows a very fast power tracking response while ensuring the global exponential stability of the system. These control laws are tested in simulation, using an average model and a detailed model with 180 sub-modules per arm. The last part is dedicated to the SBC. After a modeling step, some results regarding its structural analysis are presented, and an original control law is introduced. The essential role of the transformer for series converters like the SBC is highlighted. Finally, the performance of the proposed control law is assessed in simulation
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Kushnerov, Alexander. "High-Efficiency Self-Adjusting Switched Capacitor DC-DC Converter with Binary Resolution." Phd thesis, 2010. http://tel.archives-ouvertes.fr/tel-00507494.
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Switched-Capacitor Converters (SCC) suffer from a fundamental power loss deficiency which make their use in some applications prohibitive. The power loss is due to the inherent energy dissipation when SCC operate between or outside their output target voltages. This drawback was alleviated in this work by developing two new classes of SCC providing binary and arbitrary resolution of closely spaced target voltages. Special attention is paid to SCC topologies of binary resolution. Namely, SCC systems that can be configured to have a no-load output to input voltage ratio that is equal to any binary fraction for a given number of bits. To this end, we define a new number system and develop rules to translate these numbers into SCC hardware that follows the algebraic behavior. According to this approach, the flying capacitors are automatically kept charged to binary weighted voltages and consequently the resolution of the target voltages follows a binary number representation and can be made higher by increasing the number of capacitors (bits). The ability to increase the number of target voltages reduces the spacing between them and, consequently, increases the efficiency when the input varies over a large voltage range. The thesis presents the underlining theory of the binary SCC and its extension to the general radix case. Although the major application is in step-down SCC, a simple method to utilize these SCC for step-up conversion is also described, as well as a method to reduce the output voltage ripple. In addition, the generic and unified model is strictly applied to derive the SCC equivalent resistor, which is a measure of the power loss. The theoretical predictions are verified by simulation and experimental results.
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Lee, Yu-Huei, and 李昱輝. "Single-Inductor Dual-Output Step-Down DC-DC Converter with High Power Conversion Efficiency for SoC System." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/28592344390662246142.
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博士<br>國立交通大學<br>電控工程研究所<br>100<br>A single-inductor dual-output (SIDO) step-down DC-DC converter with continuous conduction mode (CCM) operation is proposed to achieve an area-efficient power management module. The low-voltage energy distribution controller (LV-EDC) can simultaneously guarantee good voltage regulation and low output voltage ripple. With the proposed dual-mode energy delivery methodology, cross regulation in steady-state output voltage ripple, which is rarely discussed, and cross regulation in load transient response are both effectively reduced. In addition, the energy mode transition operation helps obtain the appropriate energy operation mode using the energy delivery paths for dual outputs. Moreover, within the allowable output voltage ripple, the automatic energy bypass (AEB) mechanism can reduce the number of energy delivery paths, thereby ensuring voltage regulation and further enhancing efficiency. In addition, the energy prediction function can also help effectively eliminate the transient cross regulation. It is because the energy distribution for the output with a constant load condition can be remained unchanged, so as to avoid the unwilling voltage variations at output. The test chip fabricated in 65 nm CMOS and achieves 91% peak efficiency, low output voltage ripple, on-chip compensation, and excellent load transient response with eliminate transient cross regulation for a high efficiency system-on-a-chip (SoC) integration.
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Chiu, Chao-Chang, and 邱昭彰. "A High Power Conversion Efficiency AC/DC Power Module for Liquid Crystal Display Television System." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/84y8t8.
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博士<br>國立交通大學<br>電控工程研究所<br>103<br>This thesis presents an AC/DC power module, composed of buck-type power factor correction (PFC) converter, primary side regulation (PSR) converter, and secondary side flexible voltage scaling (FVS) converter, for liquid crystal display (LCD) television (TV) system. First of all, the proposed buck-type PFC converter modulates the input current by the sine square modulation mechanism (SSCM) to shape the input AC current as sine wave and thus in-phase with input AC source. Moreover, high total harmonic distortion (THD) in conventional dead angle problem in buck-type PFC can be reduced by the proposed line voltage rebuilt (LVR) technique. Conventional line current is zero in dead angle period and the detected line voltage contains the output voltage information. Therefore, the proposed LVR technique rebuilds the line voltage to remove the offset problem for reducing THD. Second, the proposed PSR converter not only provides the standby power for TV system but also directly charges the battery by the AC source. The PSR converter removes the feedback network in conventional flyback converters. The proposed self-calibrated knee voltage detector (SC-KVD) accurately senses the output voltage information by an auxiliary winding. Moreover, the test chip fabricated in 0.5μm 500V UHV process can be powered on directly by the AC source for high efficiency and compact size through the use of 500V ultra-high voltage device. Third, the proposed secondary side FVS converter moves the controller of flyback converter from the primary side to the secondary side. The proposed overall power management (OPM) in TV system can improve overall conversion efficiency by the flexible voltage scaling (FVS) technique in cooperation with conventional dynamic voltage scaling (DVS) technique. The test chips of the buck-type PFC converter, PSR converter and FVS converter were fabricated in 0.5μm ultra-high voltage CMOS process with chip area of 4.75 mm2,3.125mm2 and 4.05 mm2, respectively, to demonstrate the improved performance. Overall performance can show high accuracy, compact size, high flexibility, and high efficiency in this thesis.
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Barnett, Raymond Elijah. "High efficiency RF to DC conversion and ultra-low-power analog front end circuits for low-cost field-powered UHF RFID /." 2007. http://proquest.umi.com/pqdweb?did=1441203891&sid=4&Fmt=2&clientId=10361&RQT=309&VName=PQD.
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Chen, Kuan-cheng, and 陳冠丞. "High-efficiency high-voltage DC/DC step-down chip design." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/36796732916723368848.
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碩士<br>國立雲林科技大學<br>電子與光電工程研究所碩士班<br>101<br>In this thesis, it uses the process of TSMC 0.25 um CMOS HIGH VOLTAGE MIXED SIGNAL to complete a total of three wafers and be off the assembly line of TSMC through CIC. The wafers are as the following respectively: (a) low-dropout linear regulator. Measurement results show that the feature of low voltage drop allows the conversion efficiency is up to 98.5% when the input voltage and the output voltage of circuit are similar; (b) simple-switching buck converter. It uses relatively simple feedback circuit to complete PWM control, and measurement results show that the PWM frequency will be decreased as the load increases, which can be applied to the load sensing in the future; (c) digital control switching buck converter. It uses all-digital way to control and generate PWM. It can fix PWM to obtain the best output voltage. The circuit can provide different voltage levels conversion according to the different functional needs.
Additionally, digital control switching buck converter uses FPGA to achieve LED driver circuit and then apply to LED driving. According to different applications, it uses different LED serial number, so LED is also changed as the driving voltage. This paper presents self-adaptive voltage regulation LED driving system. The input voltage is fixed at 40V, and the output voltage can follow different LED serial number to adjust to optimal driving automatically. The maximum output current can be driven to 1A. It can adjust LED brightness in accordance with user requirements.
The circuit test results show the adjustable output voltage range is 0V ~ 38V, and it can drive 10 1W white LED (300mA), or 10 3W White LED (500mA), or 5 5W white LED (600mA) with maximum efficiency 84.69%.
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Wu, Mao-Fu, and 吳懋富. "Wide Load Range High Efficiency Multiphase DC-DC Converter." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/sad22v.
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碩士<br>國立臺灣科技大學<br>電子工程系<br>107<br>For a system-on-chip (SoC) of mobile device, the power supply is required to have driving capability of high current, high efficiency, fast load transient, small area and so on. Wide Load Range High Efficiency Multiphase DC-DC Converter is presented in this paper. By advantage of constant on time control achieve fast transient response and By using adjustable area of mosfet, frequency and numbers of phases improve efficiency. Finally, the figure of efficiency can get better curve in wide load.The chip is implemented in TSMC 0.18μm 1P6M CMOS process. The chip area including PADs is 2.5×1.515 mm2. The specifications of the converter are the input voltage range of 3V~3.6V, output voltage of 1.8V, switch frequency of 2 MHz, current range of 10mA~2000mA. The off-chip inductance and capacitance are 2.7 μH and 10 μF, respectively. ESR of the output capacitance is 15 mΩ. When converter current is set as 300mA, the efficiency improved is up to 25%.
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Yang, Shun-Pin, and 楊舜斌. "A High Efficiency Switched-Capacitor DC-DC up Converter." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/82947824464929343599.
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碩士<br>國立中山大學<br>電機工程學系研究所<br>91<br>A new DC-DC up converter with high efficiency and low output ripple is proposed. We replace previous charge pump converters by switched-capacitor converters to improve the power efficiency and add a voltage regulator at the output to reduce the ripple voltage. The converter reduces the magnitude of output voltage ripples to 36% of the previous converter, and improves the power efficiency from 58% to 73%. The proposed converter is designed to obtain 1.6 mA driving capability with a output voltage around 5.3 ~ 5.4 V. A VCO is also added as the load to test the converter circuit. The VCO is insensititive to power supply noises. The proposed converter circuit is simulated in a TSMC 0.35-um Mixed-mode (2P4M) CMOS process.
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Chen, Chien-cheng, and 陳建成. "A High Efficiency Current Mode Control DC-DC Buck Converter." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/07494232505610402844.
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碩士<br>國立中央大學<br>電機工程研究所<br>99<br>In this changing rapidly era of electronic technology, the major demands of portable electronics are short, thin, and full functionalities. These sub-circuits of the portable electronics, which use batteries for power sources, need a stable supply voltage generating by power converters. These power converters must have low power consumption and high efficiency to extend the service time of portable electronics. Thus, a high efficiency current mode buck converter is presented in this thesis.
The proposed buck converter uses current-mode controlling mechanism to accelerate the transient response during the transient period. It senses the current variation of the output inductor. Therefore, it achieves low operating current and high efficiency by removing the V-to-I converting circuit. This buck converter has better performance in the specification of efficiency comparing with traditional buck converter with current-mode controlling. This current-mode buck converter is fabricated with TSMC 0.35um 3.3 V CMOS process. In the proposed buck converter, the operation voltage is form 3.8 V to 5.5 V, the output voltage is 3.3 V, the output current is from 0.05 A to 1 A, and the highest efficiency is 97.4 %. The line regulation and load regulation are 17.5 mV/V and 1.15 mV/A, respectively. The chip area is 2.46 mm2.
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Zhao, Ruichen. "Analysis, modeling, and control of highly-efficient hybrid dc-dc conversion systems." Thesis, 2012. http://hdl.handle.net/2152/ETD-UT-2012-12-6609.
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This dissertation studies hybrid dc-dc power conversion systems based on multiple-input converters (MICs), or more generally, multiport converters. MICs allow for the integration of multiple distributed generation sources and loads. Thanks to the modular design, an MIC yields a scalable system with independent control in all sources. Additional characteristics of MICs include the improved reliability and reduced cost. This dissertation mainly studies three issues of MICs: efficiency improvement, modeling, and control.
First, this work develops a cost-effective design of a highly-efficient non-isolated MIC without additional components. Time-multiplexing (TM) MICs, which are driven by a time-multiplexing switching control scheme, contain forward-conducting-bidirectional-blocking (FCBB) switches. TM-MICs are considered to be subject to low efficiency because of high power loss introduced by FCBB switches. In order to reduce the power loss in FCBB switches, this work adopts a modified realization of the FCBB switch and proposes a novel switching control strategy. The design and experimental verifications are motivated through a multiple-input (MI) SEPIC converter. Through the design modifications, the switching transients are improved (comparing to the switching transients in a conventional MI-SEPIC) and the power loss is significantly reduced. Moreover, this design maintains a low parts-count because of the absence of additional components. Experimental results show that for output power ranging from 1 W to 220 W, the modified MIC presents high efficiency (96 % optimally). The design can be readily extended to a general n-input SEPIC. The same modifications can be applied to an MI-Ćuk converter.
Second, this dissertation examines the modeling of TM-MICs. In the dynamic equations of a TM-MIC, a state variable from one input leg is possible to be affected by state variables and switching functions associated with other input legs. In this way, inputs are coupled both topologically and in terms of control actions through switching functions. Coupling among the state variable and the time-multiplexing switching functions complicate TM-MICs’ behavior. Consequently, substantial modeling errors may occur when a classical averaging approach is used to model an MIC even with moderately high switching frequencies or small ripples. The errors may increase with incremental number of input legs. In addition to demonstrating the special features on MIC modeling, this dissertation uses the generalized averaging approach to generate a more accurate model, which is also used to derive a small-signal model. The proposed model is an important tool that yields better results when analyzing power budgeting, performing large-signal simulations, and designing controllers for TM-MICs via a more precise representation than classical averaging methods. Analyses are supported by simulations and experimental results.
Third, this dissertation studies application of a decentralized controller on an MI-SEPIC. For an MIC, a multiple-input-multiple-output (MIMO) state-space representation can be derived by an averaging method. Based on the averaged MIMO model, an MIMO small-signal model can be generated. Both conventional method and modern multivariable frequency analysis are applied to the small-signal model of an MI-SEPIC to evaluate open-loop and closed-loop characteristics. In addition to verifying the nominal stability and nominal performance, this work evaluates robust stability and robust performance with the structured singular value. The robust performance test shows that a compromised performance may be expected under the decentralized control. Simulations and experimental results verify the theoretical analysis on stability and demonstrate that the decentralized PI controller could be effective to regulate the output of an MIC under uncertainties.
Finally, this work studies the control of the MIMO dc-dc converter serving as an active distribution node in an intelligent dc distribution grid. The unified model of a MIMO converter is derived, enabling a systematical analysis and control design that allows this converter to control power flow in all its ports and to act as a power buffer that compensates for mismatches between power generation and consumption. Based on the derived high-order multivariable model, a robust controller is designed with disturbance-attenuation and pole-placement constraints via the linear matrix inequality (LMI) synthesis. The closed-loop robust stability and robust performance are tested through the structured singular value synthesis. Again, the desirable stability and performance are verified by simulations and experimental results.<br>text
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Chang-YingWu and 吳長穎. "A Novel High Conversion Ratio Bidirectional DC-DC Converter with Coupled-Inductor." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/71988440308826225047.
Full textAbstract:
碩士<br>國立成功大學<br>電機工程學系碩博士班<br>100<br>In this thesis, a novel high conversion ratio bidirectional DC-DC converter with coupled-inductor technique is proposed. In boost mode, two capacitors are parallel charged and series discharged by the coupled-inductor. Thus, high step-up voltage gain can be achieved with an appropriate duty ratio. The voltage stress on the main switch is reduced by a clamp circuit. Therefore, low resistance RDS(ON) of the main switch can be adopted to reduce conduction loss. In buck mode, two capacitors are series charged and parallel discharged by coupled-inductor. The high step-down gain is achieved. Besides, all of the switches are zero voltage-switching (ZVS) turned on and the switching loss can be improved. Due to two active clamp circuits, The efficiency can be further improved. The operating principle and steady-state analyses of the voltage gain are discussed. Finally, a 24-V input voltage, 400-V output voltage, and 200-W output power prototype circuit is implemented in the laboratory to verify the performance.
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"A power electronic converter for high voltage step down DC-DC conversion." Thesis, 2010. http://hdl.handle.net/10210/3482.
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Ma, Mengzhe. "Design of high efficiency step-down switched capacitor DC/DC converter." Thesis, 2003. http://hdl.handle.net/1957/30904.
Full textAbstract:
Recently, switched capacitor DC/DC converters are extensively used in
portable electronic devices because they feature many advantages, such as high
efficiency, small package, low quiescent current, minimal external components and
low cost.
In this thesis, two step-down switched capacitor DC/DC converters are
designed. One has the fixed output options 1.5V, 1.8V and 2.0V. The other one has the
output 1.2V. These two converters are implemented in 0.5��m CMOS process through
National Semiconductor Corporation. The design is verified by the circuit-level
simulations, and design issues are discussed.<br>Graduation date: 2004
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Li, Chi-Hung, and 黎紀宏. "High-Efficiency Resonant Boost DC/DC Converter with Full Digital Control." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/6cpx9v.
Full textAbstract:
碩士<br>國立交通大學<br>電控工程研究所<br>101<br>This thesis concluded the design and implementation of high efficiency resonant boost DC-DC converter. Its circuit structure contained 2 stages. The full bridge phase-shift circuit was equipped the front one for producing the rectangle waves, which then were raised to high voltage and segregated. The second stage using the LC resonant circuit efficiently stepped up. This converter is widely applied to solar panel, fuel cell and a variety of step-up systems.
In the contents discussed the principle of resonant circuit and analysed the frequency conversion and phase-shift modes. According to the gain curve collected via simulation, it testified that it was doable to improve the efficiency of the switches control.The experimental results revealed that the lowest efficiency was around 87.9% as the load was varied between 30W and 300W, and the highest efficiency was 96.3% as the load was at 210W.
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Huang, Shih-Ming, and 黃士銘. "Design and Implementation of a High-Efficiency Bidirectional DC-DC Converter." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/9fjgv3.
Full textAbstract:
碩士<br>國立臺灣科技大學<br>電機工程系<br>102<br>This thesis studies the design and implementation of a non-isolated dual-half-bridge bidirectional DC-DC converter. Using the presented topology, high efficiency can be achieved under wide-range load variations by the zero-voltage-switching features and phase-shift control method. In this thesis, dsPIC33FJ16GS502 digital signal controller (DSC) is utilized to implement the digital controller of the bidirectional DC-DC converter. According to the experimental results, a light-load efficiency over 92 % and a full-load efficiency over 97% can be achieved.
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Lin, Yong-Kai, and 林詠凱. "Design and Implementation of a High Efficiency Bidirectional DC/DC Converter." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/bjpfvb.
Full textAbstract:
碩士<br>國立臺北科技大學<br>電機工程系所<br>94<br>The objective of this thesis is to design and implement a high efficiency bidirectional DC/DC converter for fuel cell systems, which converts the energy from battery (or load) to fuel cell and visa versa. When the converter operates in buck mode, the power is provided by battery with constant voltage. In contrast, when the converter operates in boost mode, the battery is charged by fuel cells or regenerative energy of load with constant current. The details of the specification include:
Power rating = 1.5 kW
Voltage rating =24V/45V
First, the operation principle of bidirectional DC/DC converter is described. Then, the designed bidirectional DC/DC converter is verified by SIMULINK and the converter is realized. Moreover, the implemented bidirectional DC/DC converter controlled by dSPACE is verified by experimental results. Experimental results confirm that the energy can be converted in two directions by the implemented bidirectional DC/DC converter and the efficiency is over than 90%.