Dissertations / Theses: 'Zero current switching'

1

Hua, Guichao. "Novel zero-voltage switching techniques for pulse-width-modulated converters." Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-03242009-040340/.

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Mao, Hengchun. "Soft-switching techniques for high-power PWM converters." Diss., This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-10052007-143055/.

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3

Bills, David Marlin. "Soft Switching Multi-Resonant Forward Converter DC to DC Application for Communications Equipment." Master's thesis, University of Central Florida, 2007. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3497.

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In the field of power electronics there is always a push to create smaller and more efficient power conversion systems. This push is driven by the industry that uses the power systems, and can be realized by new semiconductor devices or new techniques. This examination describes a novel technique for a small and highly efficient method of converting relatively high DC voltage to a very low voltage for use in the telecommunications industry. A modification to the standard Forward Resonant converter results in improvements in component stress, system efficiency, response time, and control circuitry. This examination describes background information needed to understand the concepts in DC to DC power systems, "soft-switching" topologies, and control methods for these systems. The examination introduces several topologies that are currently being used, and several types that have been previously analyzed, as a starting point for the detailed analysis of the proposed converter topology. A detailed analytical analysis is given of the proposed topology, including secondary effects, and component stresses. This analysis is compared to the results found from both Pspice simulation, and a working DC to DC converter. Finally, the topology is examined for potential improvements, and possible refinements to the model described.
M.S.E.E.
School of Electrical Engineering and Computer Science
Engineering and Computer Science
Electrical Engineering MSEE

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4

Li, Yong. "Unified zero-current-transition techniques for high-power three-phase PWM inverters." Diss., Virginia Tech, 2002. http://hdl.handle.net/10919/26843.

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This dissertation is devoted to a unified and comprehensive study of zero-current-transition (ZCT) soft-switching techniques for high-power three-phase PWM inverter applications. Major efforts in this study are as follows: 1) Conception of one new ZCT scheme and one new ZCT topology; 2) Systematic comparison of a family of ZCT inverters; 3) Design, implementation and experimental evaluation of two 55-kW prototype inverters for electric vehicle (EV) motor drives that are developed based on the proposed ZCT concepts; and 4) Investigation of the ZCT concepts in megawatts high-frequency power conversions. The proposed ZCT techniques are also applicable to three-phase power-factor-correction (PFC) rectifiers. In order to minimize switching losses, this work first proposes a new control scheme for an existing three-phase ZCT inverter circuit that uses six auxiliary switches. The proposed scheme, called the six-switch ZV/ZCT, enables all main switches, diodes and auxiliary switches to be turned off under zero-current conditions, and in the meantime provides an opportunity to achieve zero-voltage turn-on for the main switches. Meanwhile, it requires no modification to normal PWM algorithms. Compared with existing ZCT schemes, the diode reverse-recovery current is reduced significantly, the switching turn-on loss is reduced by 50%, the resonant capacitor voltage stress is reduced by 30%, and the current and thermal stresses in the auxiliary switches are evenly distributed. However, a big drawback of the six-switch ZV/ZCT topology, as well as of other types of soft-switching topologies using six auxiliary switches, is the high cost and large space associated with the auxiliary switches. To overcome this drawback, this work further proposes a new three-phase ZCT inverter topology that uses only three auxiliary switches-- the three-switch ZCT. The significance of the proposed three-switch ZCT topology is that, among three-phase soft-switching inverters developed so far, this is the only one that uses fewer than six auxiliary switches and still has the following three features: 1) soft commutation for all main switches, diodes and auxiliary switches in all operation modes; 2) no modification to normal PWM algorithms; and 3) in practical implementations, no need for extra resonant current sensing, saturable cores, or snubbers to protect the auxiliary switches. The proposed six-switch ZV/ZCT and three-switch ZCT inverters, together with existing ZCT inverters, constitute a family of three-phase ZCT inverters. To explore the fundamental properties of these inverters, a systematic comparative study is conducted. A simplified equivalent circuit is developed to unify common traits of ZCT commutations. With the visual aid of state planes, the evolution of the family of ZCT inverters is examined, and their differences and connections are identified. Behaviors of individual inverters, including switching conditions, circulating energy, and device/component stresses, are compared. Based on the proposed six-switch ZV/ZCT and three-switch ZCT techniques, two 55-kW prototype inverters for EV traction motor drives have been built and tested to the full-power level with a closed-loop controlled induction motor dynamometer. The desired ZCT soft-switching features are realized together with motor drive functions. A research effort is carried out to develop a systematic and practical design methodology for the ZCT inverters, and an experimental evaluation of the ZCT techniques in the EV motor drive application is conducted. The design approach integrates system optimization with characterizations of the main IGBT device under the ZCT conditions, selection, testing and characterization of the auxiliary devices, design and selection of the resonant inductors and capacitors, inverter loss modeling and numerical analysis, system-level operation aspects, and layout and parasitic considerations. Different design aspects between these two ZCT inverters are compared and elaborated. The complexity of the 55-kW prototype implementations is compared as well. Efficiencies are measured and compared under a group of torque/speed points for typical EV drive cycles. Megawatts high-frequency power conversion is another potential application of the ZCT techniques. The integrated gate commutated thyristor (IGCT) device is tested and characterized under the proposed six-switch ZV/ZCT condition, and the test shows promising results in reducing switching losses and stresses. Improvements in the IGCT switching frequency and simplification of the cooling requirements under ZCT operations are discussed. In addition, a generalized ZCT cell concept is developed based on the proposed three-switch ZCT topology. This concept leads to the discovery of a family of simplified multilevel soft-switching inverters that reduce the number of auxiliary switches by half, and still maintain desirable features.
Ph. D.

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Lee, Moonhyun. "Digital-Based Zero-Current Switching (ZCS) Control Schemes for Three-Level Boost Power-Factor Correction (PFC) Converter." Diss., Virginia Tech, 2020. http://hdl.handle.net/10919/99694.

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With the increasing demands on electronic loads (e.g. desktop, laptop, monitor, LED lighting and server) in modern technology-driven lives, performance of switched-mode power supply (SMPS) for electronics have been growing to prominence. As front-end converters in typical SMPS structure, ac-dc power-factor correction (PFC) circuits play a key role in regulations of input power factor, harmonics and dc output voltage, which has a decisive effect on entire power-supply performances. Universal ac-line and low-power system (90–264 Vrms, up to 300–400 W) is one of the most common power-supply specifications and boost-derived PFC topologies have been widely used for the purpose. In order to concurrently achieve high efficiency and low-cost system in the PFC stage, zero-current switching (ZCS) control schemes are highly employed in control principles. Representative schemes are discontinuous conduction mode (DCM) and critical conduction mode (CRM). Both modes can realize ZCS turn-on without diode reverse recovery so that low switching losses and low-cost diode utilizations are obtainable. Among various boost-family PFC topologies, three-level boost (TLB) converter has generated considerable research interest in high-voltage high-power applications. It is mainly due to the fact that the topology can have halved component voltage stresses, improved waveform qualities and electromagnetic interference (EMI) from phase interleaved continuous conduction mode (CCM) operations, compared to other two-level boost PFC converters. On the other hand, in the field of universal-line low-power applications, TLB PFC has been thoroughly out of focus since doubled component counts and increased control complexity than two-level topologies are practical burden for the low-cost systems. However, recent researches on TLB PFC with ZCS control schemes have found that cost-competitiveness of the topology is actually comparable to two-level boost PFC converters because the halved component voltage stresses enable usage of low voltage-rating components of which unit prices are cheaper than higher-rating ones. Based on the justification, researches on ZCS control schemes for TLB PFC have been conducted to get enhanced waveform qualities and performance factors. Following the research stream, a three-level current modulation scheme that can be adopted in both DCM and CRM is proposed in Chapter 2 of this dissertation. Main concept of the proposed current modulation is additional degree-of-freedom in current-slope shaping by differentiating on-times of two active switches, which cannot be found from any other single-phase boost-derived PFC topologies. Using the multilevel feature, proposed operations in one switching period consist of three steps: common-switch on-time, single-switch on-time and common-switch off-time. The single-switch on-time step is key design factor of the proposed modulation that can be utilized either in fixed or adjustable form depending on control purpose. Based on the basic modulation concept, three-level CRM control scheme, adjustable three-level DCM control scheme, and spread-spectrum frequency modulation (SSFM) with adjustable three-level DCM scheme are proposed in Chapter 3–5, respectively. In each chapter, implemented control scheme aims to improve different performance factors. In Chapter 3, the proposed three-level CRM scheme uses increased single-switch on-time period to reduce peak inductor current and magnitude of variable switching frequency. It is generally accepted fact that CRM operations suffer from high switching losses and poor efficiency at light load due to considerable increment of switching frequency. Thus, efficiency improvement effect by the proposed CRM scheme becomes remarkable as load condition goes lighter. In experimental verifications, maximum improvement is measured by 1.2% at light load (20%) and overall efficiency is increased by at least 0.4% all over the load range. In Chapter 4, three-level DCM control scheme adopts adjustable single-switch on-time period in fixed switching-frequency framework. The purpose of adjustable control scheme is to widen the length of non-zero inductor current period as much as possible so that discontinued current period and high peak current of DCM operations can be minimized. Experiment results show that, compared to conventional two-level DCM control, full-load peak inductor currents are reduced by 20.2% and 17.1% at 110 and 220 Vrms input voltage conditions, respectively. Moreover, due to turn-off switching energy decrements by the turn-off current reductions, efficiency is also improved by at least 0.4% regardless of input voltage and load conditions. In Chapter 5, a downward SSFM technique is developed first for DCM operations of boosting PFC converters including two-level topologies. This chapter aims to achieve significant reduction of high differential-mode (DM) EMI amplitudes from DCM operations, which is major drawback of DCM control. By using the simple linearized frequency modulation, peak DM EMI noise at full load condition is reduced by 12.7 dBμV than conventional fixed-frequency DCM control. On top of the proposed SSFM, the adjustable three-level DCM control scheme in Chapter 4 is adopted to get further reductions of EMI noises. Experimental results prove that the collaborations of SSFM and adjustable DCM scheme reduce the EMI amplitudes further by 2.5 dBμV than the result of SSFM itself. The reduced EMI amplitudes are helpful to design input EMI filter with higher cut-off frequency and smaller size. Different from two-level boosting PFC converters, TLB PFC topology has two output capacitors in series and inherently suffers from voltage unbalancing issue, which can be noted as topological trade-off. In Chapter 6, two simple but effective voltage balancing schemes are introduced. The balancing schemes can be easily built into the proposed ZCS control schemes in Chapter 3–5 and experimental results validate the effectiveness of the proposed balancing principles. For all the proposed control schemes in this dissertation, detailed operation principles, derivation process of key equations, comparative analyses, implementation method with digital controller and experimental verifications with TLB PFC prototype are provided.
Doctor of Philosophy
Electronic-based devices and loads have been essential parts of modern society founded on rapid advancements of information technologies. Along with the progress, power supplying and charging of electronic products become routinized in daily lives, but still remain critical requisites for reliable operations. In many power-electronics-based supplying systems, ac-dc power-factor correction (PFC) circuits are generally located at front-end to feed back-end loads from universal ac-line sources. Since PFC stages have a key role in regulating ac-side current quality and dc-side voltage control, the importance of PFC performances cannot be emphasized enough from entire system point of view. Thus, advanced control schemes for PFC converters have been developed in quantity to achieve efficient operations and competent power qualities such as high power factor, low harmonic distortions and low electromagnetic interferences (EMI) noises. In this dissertation, a sort of PFC topologies named three-level boost (TLB) converter is chosen for target topology. Based on inherent three-level waveform capability of the topology, multiple zero-current switching (ZCS) control schemes are proposed. Compared to many conventional two-level PFC topologies, TLB PFC can provide additional degree-of-freedom to current modulation. The increased control flexibility can realize improvements of various waveform qualities including peak current stress, switching frequency range, harmonics and EMI amplitude. From the experimental results in this dissertation, improvements of waveform qualities in TLB PFC with the proposed schemes are verified with comparison to two-level current control schemes; in terms of efficiency, the results show that TLB PFC with the proposed schemes can have similar converter efficiency with conventional two-level boost converter in spite of increased component counts in the topology. Further, the proposed three-level control schemes can be utilized in adjustable forms to accomplish different control objectives depending on system characteristics and applications. In each chapter of this dissertation, a novel control scheme is proposed and explained with details of operation principle, key equations and digital implementation method. All the effectiveness of proposals and analyses are validated by a proper set of experimental results with a TLB PFC prototype.

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6

Haryani, Nidhi. "Zero Voltage Switching (ZVS) Turn-on Triangular Current Mode (TCM) Control for AC/DC and DC/AC Converters." Diss., Virginia Tech, 2020. http://hdl.handle.net/10919/96397.

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One of the greatest technological challenges of the world today is reducing the size and weight of the existing products to make them portable. Specifically, in electric vehicles such as electric cars, UAVs and aero planes, the size of battery chargers and inverters needs to be reduced so as to make space for more parts in these vehicles. Electromagnetic Interference (EMI) filters take up a more than 80 % of these power converters, the size of these filters can be reduced by pushing the switching frequency higher. High frequency operation (> 300 kHz) leads to a size in reduction of EMI filters though it also leads to an increase in switching losses thus compromising on efficiency. Thus, soft switching becomes necessary to reduce the losses, adding more electrical components to the converter to achieve soft switching is a common method. However, it increases the physical complexity of the system. Hence, advanced control methods are adopted for today's power converters that enable soft switching for devices specifically ZVS turn-on as the turn-off losses of next generation WBG devices are negligible. Thus, the goal of this research is to discover novel switching algorithms for soft turn-on. The state-of the-art control methods namely CRM and TCM achieve soft turn-on by enabling bi-directional current such that the anti-parallel body diode starts conducting before the device is turned on. CRM and TCM result in variable switching frequency which leads to asynchronous operation in multi-phase and multi-converter systems. Hence, TCM is modified in this dissertation to achieve constant switching frequency, as the goal of this research is to be able to achieve ZVS turn-on for a three-phase converter. Further, Triangular Current Mode (TCM) to achieve soft switching and phase synchronization for three-phase two-level converters is proposed. It is shown how soft switching and sinusoidal currents can be achieved by operating the phases in a combination of discontinuous conduction mode (DCM), TCM and clamped mode. The proposed scheme can achieve soft switching ZVS turn-on for all the three phases. The algorithm is tested and validated on a GaN converter, 99% efficiency is achieved at 0.7 kW with a density of 110 W/in3. The discussion of TCM in current literature is limited to unity power factor assumption, however this limits the algorithm's adoption in real world applications. It is shown how proposed TCM algorithm can be extended to accommodate phase shift with all the three phases operating in a combination of DCM+TCM+Clamped modes of operation. The algorithm is tested and validated on a GaN converter, 99% efficiency is achieved at 0.7 kVA with a density of 110 W/in3. TCM operation results in 33 % higher rms current which leads to higher conduction losses, as WBG devices have lower on-resistance, these devices are the ideal candidates for TCM operation, hence to accurately obtain the device parameters, a detailed device characterization is performed. Further, proposed TCM+DCM+Clamped control algorithm is extended to three-level topologies, the control is modified to extract the advantage of reduced Common Mode Voltage (CMV) switching states of the three-level topology, the switching frequency can thus be pushed to 3 times higher as compared to state-of-the-art SVPWM control while maintaining close to 99 % efficiency. Two switching schemes are presented and both of them have a very small switching frequency variation (6%) as compared to state-of-the-art methods with >200% switching frequency variation.
Doctor of Philosophy
Power supplies are at the heart of today's advanced technological systems like aero planes, UAVs, electrical cars, uninterruptible power supplies (UPS), smart grids etc. These performance driven systems have high requirements for the power conversion stage in terms of efficiency, density and reliability. With the growing demand of reduction in size for electromechanical and electronic systems, it is highly desirable to reduce the size of the power supplies and power converters while maintaining high efficiency. High density is achieved by pushing the switching frequency higher to reduce the size of the magnetics. High switching frequency leads to higher losses if conventional hard switching methods are used, this drives the need for soft switching methods without adding to the physical complexity of the system. This dissertation proposes novel soft switching techniques to improve the performance and density of AC/DC and DC/AC converters at high switching frequency without increasing the component count. The concept and the features of this new proposed control scheme, along with the comparison of its benefits as compared to conventional control methodologies, have been presented in detail in different chapters of this dissertation.

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Tian, Feng. "Pulse Frequency Modulation ZCS Flyback Converter in Inverter Applications." Doctoral diss., University of Central Florida, 2009. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4266.

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Renewable energy source plays an important role in energy co-generation and distribution. A traditional solar-based inverter system has two stages cascaded, which has simpler controller but low efficiency. A new solar-based single-stage grid-connected inverter system can achieve higher efficiency by reducing the power semiconductor switching loss and output stable and synchronizing sinusoid current into the utility grid. In Chapter 1, the characteristic I-V and P-V curve of PV array has been illustrated. Based on prediction of the PV power capacity installed on the grid-connected and off-grid, the trends of grid-tied inverter for DG system have been analyzed. In Chapter 2, the topologies of single-phase grid-connect inverter system have been listed and compared. The key parameters of all these topologies are listed in a table in terms of topology, power decoupling, isolation, bi-directional/uni-directional, power rating, switching frequency, efficiency and input voltage. In Chapter 3, to reduce the capacitance of input filter, an active filter has been proposed, which will eliminate the 120/100Hz low frequency ripple from the PV array's output voltage completely. A feedforward controller is proposed to optimize the step response of PV array output voltage. A sample and hold also is used to provide the 120/100Hz low frequency decoupling between the controller of active filter and inverter stage. In Chapter 4, the single-stage inverter is proposed. Compared with conventional two-stage inverter, which has two high frequency switching stages cascaded, the single-stage inverter system increases the system efficiency by utilizing DC/DC converter to generate rectified sinusoid voltage. A transformer analysis is conducted for the single-stage inverter system, which proves the transformer has no low-frequency magnetic flux bias. To apply peak current mode control on single-stage inverter and get unified loop gain, adaptive slope compensation is also proposed for single-stage inverter. In Chapter 5, a digital controller for single-stage inverter is designed and optimized by the Matlab Control Toolbox. A Psim simulation verified the performance of the digital controller design. In Chapter 6, three bi-directional single-stage inverter topologies are proposed and compared. A conventional single-stage bi-directional inverter has certain shortcoming that cannot be overcome. A modular grid-connect micro-inverter system with dedicated reactive energy processing unit can overcome certain shortcoming and increase the system efficiency and reliability. A unique controller design is also proposed. In Chapter 7, a PFM ZCS flyback inverter system is invented. By using half-wave quasi-resonant ZCS flyback resonant converter and PFM control, this topology completely eliminates switching loss. A detailed mathematical analysis provides all the key parameters for the inverter design. As the inductance of transformer secondary side get smaller, the power stage transfer function of PFM ZCS flyback inverter system demonstrates nonlinearity. An optimized PFM ZCS flyback DC/DC converter design resolves this issue by introducing a MOSFET on the secondary side of transformer. In Chapter 8, experimental results of uni-direcitonal single-stage inverter with grid-connection, bi-directional single-stage inverter and single-stage PFM ZCS flyback inverter have been provided. Conclusions are given in Chapter 9.
Ph.D.
School of Electrical Engineering and Computer Science
Engineering and Computer Science
Electrical Engineering PhD

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Al, Shammeri Bashar Mohammed Flayyih. "A novel induction heating system using multilevel neutral point clamped inverter." Thesis, University of Plymouth, 2017. http://hdl.handle.net/10026.1/8305.

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This thesis investigates a novel DC/AC resonant inverter of Induction Heating (IH) system presenting a Multilevel Neutral Point Clamped (MNPCI) topology, as a new part of power supply design. The main function of the prototype is to provide a maximum and steady state power transfer from converter to the resonant load tank, by achieving zero current switching (ZCS) with selecting the best design of load tank topology, and utilizing the advantage aspects of both the Voltage Fed Inverter (VFI) and Current Fed Inverter (CFI) kinds, therefore it can considered as a hybrid-inverter (HVCFI) category . The new design benefits from series resonant inverter design through using two bulk voltage source capacitors to feed a constant voltage delivery to the MNPCI inverter with half the DC rail voltage to decrease the switching losses and mitigate the over voltage surge occurred in inverter switches during operation which may cause damage when dealing with high power systems. Besides, the design profits from the resonant load topology of parallel resonant inverter, through using the LLC resonant load tank. The design gives the advantage of having an output current gain value of about Quality Factor (Q) times the inverter current and absorbs the parasitic components. On the contrary, decreasing inverter current means decreasing the switching frequency and thus, decreasing the switching losses of the system. This aspect increases the output power, which increases the heating efficiency. In order for the proposed system to be more reliable and matches the characteristics of IH process , the prototype is modelled with a variable LLC topology instead of fixed load parameters with achieving soft switching mode of ZCS and zero voltage switching (ZVS) at all load conditions and a tiny phase shift angle between output current and voltage, which might be neglected. To achieve the goal of reducing harmonic distortion, a new harmonic control modulation is introduced, by controlling the ON switching time to obtain minimum Total Harmonic Distortion (THD) content accompanied with optimum power for heating energy.

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Dvořák, Petr. "Dvojčinný kvazirezonanční DC/DC měnič s transformátorem." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2020. http://www.nusl.cz/ntk/nusl-412973.

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This diploma thesis deals with analysis of function and subsequent construction of a quasi-resonant DC / DC converter 300 V / 50 V for an output of about 1.5 kW. The aim of this work is to test and describe the behavior of an experimental converter at various operating parameters. In the theoretical part, resonant circuits are described, as well as our connection of the resonant converter. Based on the used topology and the simulated behavior of the converter, the individual components of the power circuit and its control and excitation circuit are designed in Chapters 4 and 5. The sixth chapter deals with the construction and testing of the converter, including a description of its behavior. The last chapter contains technical documentation.

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Eleyele, Abidemi Oluremilekun. "Isolated Single-Stage Interleave Resonant PFC Rectifier with Active and Novel Passive Output Ripple Cancellation Circuit." Thesis, Uppsala universitet, Institutionen för elektroteknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-423117.

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With the increasing demand for fast, cheaper, and efficient power converters come the need for a single-stage power factor correction (PFC) converter. Various single-stage PFC converter proposed in the literature has the drawback of high DC bus voltage at the input side and together with the shift to wide bandgap switches like GaN drives the converter cost higher. However, an interleaved topology with high-frequency isolation was proposed in this research work due to the drastic reduction in the DC bus voltage and extremely low input current ripple thereby making the need for an EMI filter circuit optional. Meanwhile, this research work focuses on adapting the proposed topology for a high voltage low current application (EV charger - 400V, 7KW) and low voltage high current application (telecom power supply - 58V, 58A) owing to cost benefits. However, all single-stage PFC are faced with the drawback of second-order (100Hz) output harmonic ripple. Therefore, the design and simulation presented a huge peak to peak ripple of about 50V/3A and 26V/26A for the EV charger and telecom power supply case, respectively. This created the need for the design of a ripple cancellation circuit as the research required a peak to peak ripple of 8V and 200mV for the EV - charger and telecom power supply, respectively. A novel output passive ripple cancellation technique was developed for the EV charger case due to the ease it offers in terms of control, circuit complexity and extremely low THDi when compared with the active cancellation approach. The ripple circuit reduced the 50V ripple to 431mV with the use of a total of 2.2mF capacitance at the output stage. Despite designing the passive technique, an active ripple cancellation circuit was designed using a buck converter circuit for the telecom power supply. The active approach was chosen because the passive has a slow response and incurs more loss at a high current level. Adding the active ripple cancellation circuit led to a quasi-single stage LLC PFC converter topology. A novel duty-ratio feedforward control was added to synchronize the PFC control of the input side with the buck topology ripple cancellation circuit. The addition of the ripple circuit with the feedforward control offered a peak to peak ripple of 6.7mV and a reduced resonant inductor current by half. After analysis, an extremely low THDi of 0.47%, PF of 99.99% and a peak efficiency of 97.1% was obtained for the EV charger case. The telecom power supply offered a THDi of 2.3%, PF of 99.96% with a peak efficiency of 95%.

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Casadei, Erik. "Progetto di un convertitore full-bridge phase-shifted isolato a commutazione risonante." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/10676/.

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L'evoluzione della tecnologia allo stato solido e il fiorire di nuove applicazioni determinano una forte spinta verso la miniaturizzazione dei convertitori elettronici di potenza. Questa riduzione di pesi ed ingombri è particolarmente sentita anche in quei convertitori di media potenza che necessitano di un trasformatore d'isolamento. In quest'ambito assume importante rilievo l'utilizzo di una architettura circuitale a ponte intero e di tecniche in grado di spingere la frequenza di commutazione il più in alto possibile. Questa tesi si propone quindi di studiare a fondo il funzionamento dei convertitori DC/DC isolati di tipo Full-Bridge e pilotati con la tecnica di modulazione Phase-Shifted che ben si presta all'impiego di commutazioni risonanti del tipo Zero-Voltage-Switching. L'analisi teorica sarà corroborata da simulazioni condotte su LTspice e sarà orientata all'individuazione di una metodologia di progetto generale per questo tipo di convertitori. Al fine di formalizzare meglio il progetto si è individuata una possibile applicazione nell'alimentazione di un DC-bus per telecomunicazioni (48 Volt DC sostenuti da batterie) a partire da una fonte di energia fotovoltaica quale una stringa di pannelli operanti con tensioni variabili da 120 a 180 Volt DC. Per questo particolare tipo di applicazione in discesa può avere senso l'impiego di un rettificatore del tipo a duplicazione di corrente, che quindi si provvederà a studiare e ad implementare a secondario del trasformatore d'isolamento. Infine particolare cura sarà dedicata alla parte di controllo che si ha intenzione di integrare all'interno di LTspice così da riuscire a simulare il comportamento dinamico del convertitore e verificare quanto predetto in via teorica mediante l'impiego della procedura che utilizza il K-Factor per la realizzazione della rete compensatrice.

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Han, Sangtaek. "High-power bi-directional DC/DC converters with controlled device stresses." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/49010.

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The objective of the research is to develop a cost-effective high-power bi-directional dc/dc converter with low total-device ratings, reduced system parasitic effects, and a wide input/output range. Additional objectives of the research are to develop a small-signal model and control methods, and to present performance characterizations. Device stresses in the proposed topology are controlled to maintain minimal levels by varying the duty ratio and phase-shift angle between the primary and the secondary bridges, which results in a low total-device rating, when compared to conventional bi-directional dc/dc topologies. In the proposed topology, soft switching, which reduces power loss, can be realized under specific operating conditions. When the condition that causes minimal device stress is satisfied, zero-voltage switching (ZVS) can be obtained. In the research, ZVS capability is explored for a wide range of voltage conditions as well as for the minimal device-stress condition. The performance characterization includes verifying the soft-switching regions and power-loss estimation. Another part of the thesis is the controller design of the converter. Small-signal models and feedback controllers are developed, and the controllers are experimentally validated. Because in the isolated high-frequency converters, transformer saturation is an important issue, a method to prevent transformer saturation is proposed and experimentally validated.

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Katic, Janko. "Highly-Efficient Energy Harvesting Interfaces for Implantable Biosensors." Doctoral thesis, KTH, Integrerade komponenter och kretsar, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-206588.

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Energy harvesting is identified as an alternative solution for powering implantable biosensors. It can potentially enable the development of self-powered implants if the harvested energy is properly handled. This development implies that batteries, which impose many limitations, are replaced by miniature harvesting devices. Customized interface circuits are necessary to correct for differences in the voltage and power levels provided by harvesting devices from one side, and required by biosensor circuits from another. This thesis investigates the available harvesting sources within the human body, proposes various methods and techniques for designing power-efficient interfaces, and presents two CMOS implementations of such interfaces. Based on the investigation of suitable sources, this thesis focuses on glucose biofuel cells and thermoelectric harvesters, which provide appropriate performance in terms of power density and lifetime. In order to maximize the efficiency of the power transfer, this thesis undertakes the following steps. First, it performs a detailed analysis of all potential losses within the converter. Second, in relation to the performed analysis, it proposes a design methodology that aims to minimize the sum of losses and the power consumption of the control circuit. Finally, it presents multiple design techniques to further improve the overall efficiency. The combination of the proposed methods and techniques are validated by two highly efficient energy harvesting interfaces. The first implementation, a thermoelectric energy harvesting interface, is based on a single-inductor dual-output boost converter. The measurement results show that it achieves a peak efficiency of 86.6% at 30 μW. The second implementation combines the energy from two sources, glucose biofuel cell and thermoelectric harvester, to accomplish reliable multi-source harvesting. The measurements show that it achieves a peak efficiency of 89.5% when the combined input power is 66 μW.
Energiskörd har identifierats som en alternativ lösning för att driva inplanterbara biosensorer. Det kan potentiellt möjliggöra utveckling av själv-drivna inplanterbara biosensorer. Denna utveckling innebär att batterier, som sätter många begränsningar, ersätts av miniatyriserade energiskördsenheter. Anpassade gränssnittskretsar är nödvändiga för att korrigera för de skillnader i spänning och effektnivå som produceras av de energialstrande enheterna, och de som krävs av biosensorkretsarna. Denna avhandling undersöker de tillgängliga källorna för energiskörd i den mänskliga kroppen, föreslår olika metoder och tekniker för att utforma effektsnåla gränssnitt och presenterar två CMOS-implementeringar av sådana gränssnitt. Baserat på undersökningen av lämpliga energiskördskällor, fokuserar denna avhandling på glukosbiobränsleceller och termoelektriska energiskördare, som har lämpliga prestanda i termer av effektdensitet och livstid. För att maximera effektiviteten hos effektöverföringen innehåller denna avhandling följande steg. Först görs en detaljerad analys av alla potentiella förluster inom boost-omvandlare. Sedan föreslår denna avhandling en designmetodik som syftar till att maximera den totala effektiviteten och effektförbrukningen. Slutligen presenterar den flera designtekniker för att ytterligare förbättra den totala effektiviteten. Kombinationen av de föreslagna metoderna och teknikerna är varierade genom två högeffektiva lågeffekts energigränssnittskretsar. Den första inplementeringen är ett termoelektriskt energiskördsgränssnitt baserat på en induktor, med dubbla utgångsomvandlare. Mätresultaten visar att omvandlaren uppnår en maximal effektivitet av 86.6% vid 30 μW. Det andra genomförandet kombinerar energin från två källor, en glukosbiobränslecell och en termoskördare, för att åstadkomma en tillförlitlig multi-källas energiskördslösning. Mätresultaten visar att omvandlaren uppnår en maximal effektivitet av 89.5% när den kombinerade ineffekten är 66 μW.

QC 20170508

Mi-SoC

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14

Andrade, Alexandre Motta de. "Análise, desenvolvimento e projeto de um conversor duplo Forward on-off zcs para aplicação em fontes chaveadas isoladas." Universidade Federal de Uberlândia, 2012. https://repositorio.ufu.br/handle/123456789/14496.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico
A complete study of a topology resulting from a combination of two Forward structures, attached to the same magnetic core of a transformer and operating as a Full-Bridge converter is presented. In order to reduce the switching losses and the electromagnetic interference, a soft commutation cell that provides ZCS commutation of all the switches is implemented. This converter limits the current on the main switches at the load current because diverts the sinusoidal half cycle to a auxiliary switch. This way, a new Double Forward On-Off ZCS was developed.
Um estudo completo de uma topologia, resultante de uma combinação entre duas estruturas Forward, acopladas ao mesmo núcleo magnético de um transformador, e operando como um conversor Full-Bridge, é apresentado. Com o objetivo de reduzir as perdas por chaveamento e a interferência eletromagnética, uma célula de comutação não dissipativa, que fornece uma comutação ZCS para todas as chaves do conversor é implementada. Este conversor limita a corrente nas chaves principais ao valor da corrente nominal, pois desvia o semiciclo senoidal da corrente ressonante para uma chave auxiliar. Deste modo, um novo conversor Duplo Forward On-Off ZCS é obtido.
Mestre em Ciências

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15

Drda, Václav. "Vícefázový serio-paralelní LLC rezonanční měnič." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2010. http://www.nusl.cz/ntk/nusl-218812.

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The project deals with the design of a switch-mode power supply (SMPS) with a medium and high power output. The power supply uses multiphase control switching. Electric energy is converted through a series parallel LLC resonant circuit to reach the maximum efficiency with a small size and cost efficiency of the designed power supply. The semiconductor switches use ZVS (Zero Voltage Switching) on the primary side and ZCS (Zero Current Switching) on the secondary side of the converter. The design of the converter is based on the knowledge of the high power output converters (types of switching, art topologies) and resonant topologies (series resonant circuit – SRC, parallel resonant circuit – PRC and series parallel circuit –SPRC). The design of the converter was done theoreticaly and tested by using simulation program. The simulation and partial tests served to build prototype the Interleaves Converter (ILLC). The function of the converter was tested in laboratory. The laboratory results have been compared with the theoretical and the simulation results.

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Kaya, Mehmet Can. "Design, Implementation, And Control Of A Two&amp." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12610106/index.pdf.

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In this thesis a two-stage AC/DC/DC power converter is designed and implemented. The AC/DC input stage of the converter consists of the two&
#8211
phase interleaved boost topology employing the average current mode control principle. The output stage consists of a zero voltage switching phase shifted full bridge (ZVS&
#8211
PS&
#8211
FB) DC/DC converter. For the input stage, main design goals are obtaining high input power factor, low input current distortion, and well regulated output dc voltage, and obtaining these attributes in a power converter with high power density. For the input stage, the interleaved structure has been chosen in order to obtain reduced line current ripple and EMI, reduced power component stresses, and improved power density. The control of the pre&
#8211
regulator is provided by utilizing a new commercial monolithic integrated circuit, which provides interleaved continuous conduction mode power factor correction (PFC). The output stage is formed by utilizing the available prototype hardware of a ZVS&
#8211
PS&
#8211
FB DC/DC converter and mainly the system integration and controller design and implementation studies have been conducted. The converter small signal model is derived and utilizing its transfer function and employing voltage loop control, the output voltage regulator has been designed. The output voltage controller is implemented utilizing a digital signal processor (DSP). Integrating the AC/DC preregulator and DC/DC converter, a laboratory AC/DC/DC converter system with high overall performance has been obtained. The overall system performance has been verified via computer simulations and experimental results obtained from laboratory prototype.

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17

Piveta, Renan. "Otimização do rendimento do conversor DAB aplicado ao transformador eletrônico." Universidade Federal de Santa Maria, 2015. http://repositorio.ufsm.br/handle/1/8569.

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This work developed a deep investigation about different three level three level modulation patterns that the DAB converter can operate, and the impact of these different patterns over the converter power flow and efficiency. The DAB converter can be controlled by three design variables, here defined as control trio (D1, D2, φ). D1 is the duty cycle applied to the high voltage Full Bridge, D2 is the duty cycle applied to the low voltage Full Bridge and φ is the angle between the voltages. For the selection of the control trio that allow the current flow reduction and the efficiency maximization, two algorithms based on the sweep of these variables have been developed. First, the switching frequency (fs), the transformation ratio (a) and the inductance (LHV) are defined by the weighted average efficiency (standards) which result in an optimum design (maximum efficiency) considering the transformer load curve. On the second algorithm, one figure of merit is used, here called current factor , which finds the control trio to mitigate the power flow for each operation point, specified by input and output voltages and power. As result, this work figures out the best relation of design parameters (fs, a, LHV) and of the control trio (D1, D2, φ) for all the operation range (power and voltages variations in a defined period) that results in a maximum efficiency to the DAB converter, according with the component technologies. An analysis of the conditions to get zero voltage switching on semiconductors is also performed.
Este trabalho realiza uma investigação aprofundada sobre os diferentes padrões de modulação três níveis três níveis que o conversor DAB pode assumir, e o impacto que esses diferentes padrões provocam sobre a energia circulante na estrutura e sobre o rendimento. O conversor DAB pode ser controlado por três variáveis de projeto, aqui definidos como trio de controle (D1, D2, φ). D1 é a razão cíclica aplicada ao Full Bridge do lado de alta tensão, D2 a razão cíclica aplicada ao Full Bridge do lado de baixa tensão e φ o ângulo de defasagem entre as duas tensões. Para a seleção do trio de controle que permita a redução da corrente circulante e a maximização do rendimento, foram desenvolvidos dois algoritmos baseados na varredura destas variáveis. No primeiro, através do rendimento médio ponderado (normatizado), são encontradas a frequência de comutação (fs), a relação de transformação (a) e a indutância (LHV) que resulta em um projeto ótimo (máximo rendimento) considerando a curva de carga do transformador. Já, no segundo algoritmo, é utilizada uma figura de mérito, aqui denominada de fator de corrente que encontra o trio de controle que mitiga a energia circulante para cada ponto de operação especificado pelas tensões de entrada e saída e potência. Como resultado final, este trabalho aponta a melhor combinação de parâmetros de projeto (fs, a, LHV) e do trio de controle (D1, D2, φ) para toda a faixa de operação (variações de tensões e potências no período de tempo) que implica no máximo rendimento do conversor DAB, de acordo com as tecnologias. Também é realizada uma análise das condições a serem satisfeitas para que a comutação das chaves ocorra sob zero de tensão.

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Tománek, Miloslav. "Simulace účinků zkratových proudů v rozvodnách VVN." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2008. http://www.nusl.cz/ntk/nusl-217579.

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This thesis is engaged in a theoretical calculation of short-circuit currents in electric power system in compliance with the norm ČSN 60909-0 and first of all with calculation of dynamical and thermal effects of short-circuit currents in HV switching stations in accordance with the norm ČSN 60865-1. Next the thesis is engaged in a production of programs for simulation of mechanical effects of short-circuit currents with respect to a dimensioning of constructional elements of switching station and afterwards in a practical simulation of selected parts of the real switching station type „H“ in Slavkov u Brna.

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Lefebvre, Stéphane. "Contribution à la caractérisation de l'IGBT en commutation à zéro de courant." Cachan, Ecole normale supérieure, 1994. http://www.theses.fr/1994DENS0009.

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Cette étude analyse la commutation de blocage d'un igbt utilise en commutation quasi-résonnante a zéro de courant. Deux igbt de structure technologique différente ont été étudiés, le premier est à base non homogène et a couche tampon, le second à base homogène et contrôlé d'injection de charges par l'émetteur. L'évolution de la charge stockée dans la base du transistor bipolaire interne au blocage est suivie et analysée à l'aide de simulations et d'expérimentations. Différents éléments interviennent sur l'évacuation de la charge stockée donc sur les pertes au blocage, qu'ils soient propres au composant (coefficients d'injection ou durées de vie) ou a sa commande (maintien du canal lors de la conduction de la diode antiparallèle). Ce qui permet de comprendre pourquoi les pertes au blocage sont plus faibles en commutation a zero de courant qu'en commutation commandée. Une caractérisation électrique et thermique de l'igbt permet ensuite de quantifier l'influence des conditions de commutation sur les pertes au blocage. Des limites de fonctionnement sont ainsi définies, pour s'affranchir de l'emballement thermique, principale cause de destruction des igbt a couche tampon en zcs a fréquence de découpage élevée

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20

Hsieh, Jen-Chung, and 謝荏仲. "Zero Voltage Zero Current Switching Three Phase Voltage Relay." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/f7vs63.

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碩士
聖約翰科技大學
電機工程系碩士班
106
The project presents a new three phase voltage protection relay, which use PIC18F27J13 microcontroller to implement the main protection function of the relay such as incorrect phase sequence, overvoltage, undervoltage, phase failure, asymmetry etc. In addition to these functions, we add on the adjustment of the switching phase angle of the relay contactor. While the relay is turn on at zero voltage and turn off at zero current, the spark of the contactor will be eliminated and the power dissipation is reduced, also the EMI is reduced and relay life is extended.

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21

PENG, CHANG-YI, and 彭常益. "A Three-Phase Six-Switch Rectifier with Zero-Voltage-Switching and Zero-Current-Switching Features." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/68662627484730364292.

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碩士
中原大學
電機工程研究所
98
Since the requirements for both regulation and standard on power quality and current harmonics are more strict in recent years, many switch mode rectifier techniques are widely adopted. There are many different kinds of basic types for switch mode rectifier. Three-phase six-switch topology in three-phase supply power system is often used in the equipment of the communication industry due to the facts that it has better power quality, lower current harmonics, and higher reliability; also, it is suitable for need in high power application. Adopting hard switching in switch mode power supply technology would cause low efficiency and high electromagnetic interference. In this thesis, there is an analysis and design for a soft-switching scheme that contains zero voltage switching and zero current switching. This analysis and the design combined with a three-phase six-switch topology rectifier creates a new three-phase soft-switching rectifier which would have characteristics of stable output voltage, high efficient, high power density, high power factor, and low electromagnetic interference.

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22

Hsieh, Li-Hsiung, and 謝禮雄. "Zero-Current-Switching Buck Converter for Battery Chargers." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/54900046370594056741.

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碩士
國立臺灣海洋大學
電機工程學系
100
The resonant converter provides the advantages of low switching losses, small circuit volume, light weight and high power density. Various high-frequency switching converters have replaced traditional hard -switching converters. This thesis presents zero-current-switching buck converter for battery chargers to control resonant converters flexibly. An auxiliary switch is inserted into the resonant loop in the proposed battery charger to control the resonant time precisely. The developed charger has the advantages of the hard-switching converter and the resonant converter with constant -frequency control, reduced resonant time and the operation of all switching components in the charger under the zero-current-switching condition to reduce significantly the switching losses. The developed charger circuit is highly suitable for high-frequency operation and high charging efficiency. This thesis employs the control mode for the switching of two active switches. The operation modes of the circuit and the equivalent circuits are constructed by analyzing the operating principles of the circuit, based on the turn-on conditions of the active switches. The equations used to determine the circuit parameters are derived from the equivalent circuits. Experimental results have demonstrated the theoretical effectiveness of the proposed battery charger circuit. A practical mean charging efficiency of over 90% is obtained.

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23

XIE, SHENG-QUAN, and 謝勝全. "Wireless Power Transfer with Zero-Current-Switching Converter." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/m58b67.

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24

Chiu, Yin-Yuan, and 邱雲源. "Zero-current-switching switched-capacitor bidirectional DC-DCconverter." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/70559327738240605640.

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碩士
輔仁大學
電子工程學系
94
This paper presents the new topologies of zero-current switching switched-capacitor (ZCS SC) quasi-resonant converters with bi-directional power flow control conversion schemes. It possesses the features of quasi resonant switched-capacitor converters: low weight, small volume, high efficiency, low EMI emission and low current stress. A family of zero-current switching switched-capacitor bi-directional converters is proposed to improve the current stress problem during the bi-directional power flow control processing. They are able to provide the voltage conversion ratios from 2 / (double-mode/half-mode) to n / (n-mode/ mode) by using four power MOSFET main switches and a set of switched-capacitors with a small series connected resonant inductor for non-inverting or inverting modes. The operation principle of converter operation of the proposed bi-directional power conversion scheme is described in detail with circuit model analysis for non-inverting/inverting mode. Simulation and experimental results are carried out to verify the concept and the performance of the proposed non-inverting/inverting ZCS SC bi-directional quasi-resonant converters.

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25

Ou, Wei-sheng, and 歐威盛. "Hybrid Zero-Voltage- and Zero-Current-Switching Phase-Shift Full-Bridge Converter." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/85117610964744319402.

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碩士
國立中山大學
電機工程學系研究所
101
Conventional phase-shift full-bridge converter can achieve Zero-Voltage Switching (ZVS) at power switches by phase shift control of switches’ driving signal. However, the problems such as freewheeling circulating loss, duty cycle loss, parasitic ringing and hard to achieves ZVS in the lagging leg switches at light load still exist in the conventional phase-shift full-bridge converter. Thus the conventional phase-shift full-bridge converter can not be operated efficiently at light load. This thesis implements a hybrid Zero-Voltage and Zero Current Switching (ZVZCS) phase-shift full-bridge converter. An auxiliary resonant circuit is added to the secondary side of the conventional phase-shift full-bridge converter to generate resonant current. Based on the generated resonant current, the ZVS for leading-leg switches and ZCS for lagging-leg switches can be achieved without modifying the original switches’ driving Pulse Width Modulation (PWM) signals. The freewheeling circulating loss, duty cycle loss and parasitic ringing can therefore be reduced. The detailed operation modes and circuit parameters design for the proposed converter are analyzed in this thesis. A circuit prototype for the proposed ZVZCS phase-shift full-bridge converter with rated power 480W is implemented in this thesis. The performances between the conventional phase-shift full-bridge converter and the proposed ZVZCS phase-shift full-bridge converter are also investigated. Experimental results demonstrate the features of the proposed ZVZCS converter.

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26

Kuo-Fan, Lin. "Design of the Improved Zero Current Switching PFC Converter." 2005. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0002-1706200511393600.

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27

Lin, Kuo-Fan, and 林國藩. "Design of the Improved Zero Current Switching PFC Converter." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/75176769361446257782.

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碩士
淡江大學
電機工程學系碩士班
93
In the PFC converter design must carefully deal with the hard switching losses due to the recovery current of boost diode. There are two approaches had proposed to solve the hard switching losses issue. One is passive soft switching method and the other is active soft switching method. Practically, the passive soft switching method has been used more widely in industry, because of it has simple, low cost, and reliable. Although, the passive soft switching method has more merits but it still exists some drawbacks that need to be improved. This thesis proposes the improved zero current switching method not only to solve the hard switching issue but also to improve drawbacks of the passive soft switching method. Especially, the saturable core (Amorphous core) and a branch circuit are proposed to substitute the fixed inductor in ZCS circuit. This proposal optimizes the passive soft switching circuit and improves many drawbacks. In this thesis, besides the principle of operation is introduced in detail, the experimental results of the real implementation is compared with the hard switching PFC converter as well as others passive soft switching. According to experimental results, this proposed improved zero current switching method is proved feasible, and also improves the most of drawbacks of passive soft switching methods.

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Liu, LiJen, and 劉立人. "Multi-phase Bidirectional Zero Current Switching Switched-Capacitor Converters." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/91217931783053466578.

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碩士
輔仁大學
電機工程學系
100
This thesis proposes a high efficiency and high power density bidirectional power converters. The proposed multi-phase implementation in the quasi resonant (QR) zero current switching (ZCS) switched capacitor (SC) bidirectional DC-DC converter structure helps to reduce current ripple, switching loss and significantly increase the converter efficiency and power density. This approach provides a more precise output voltage to obtain voltage conversion ratios from the double-mode versus half-mode to n-mode versus 1/n mode. This is accomplished by adding a different number of switched-capacitors and power MOSFET switches with a small series connected resonant inductor for forward and reverse schemes. The size and cost can be reduced when the proposed converter has coupled inductance. This paper presents the simulation and experimental results for two-phase and four-phase with and without coupled inductance QR ZCS SC converters in bidirectional solar energy charging applications.

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29

Shiu, Shin-Ming, and 徐新明. "Analysis and Design of a Novel Interleaved Boost Converter with Zero-Voltage-Switching and Zero-Current-Switching Characteristics." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/80314328637175630676.

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碩士
國立雲林科技大學
電機工程系碩士班
97
A novel interleaved boost converter with zero voltage switching (ZVS) and zero current switching (ZCS) characteristics is proposed in this thesis. This topology is suitable for the applications of high output voltage and low output current. A prototype converter circuit is given for 150V~250V input voltage and 400V with 200W to 600W output. By the interleaved approach, this topology not only decreases the current stress of the main circuit device but also reduces the ripple of the input current and output voltage. Moreover, by establishing the common soft-switching module, the soft-switching interleaved converter can greatly reduce the size and cost. The main switches can achieve the characteristics of ZVS and ZCS simultaneously to reduce the switching loss and improve the efficiency for wide load range. This topology has two operation conditions if the duty cycle can exceed 50%. The converter should have a resonant path to accomplish ZVS or ZCS in different conditions. A driving circuit design for the proposed topology determines the two conditions automatically according to the overlap condition of the duty cycles of the two switches. The driving signal of the soft-switching module is composed of the ZVS driving signal and the overlap driving signal of the two switches to achieve the functions of ZVS and ZCS. The operational principle, theoretical analysis and design method of the proposed converter are presented. Simulation and experimental results are finally used to verify the feasibility and exactness of the proposed converter.

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30

Ming-ChiaLee and 李明嘉. "Zero-Voltage and Zero-Current Switching for Multilevel Modular Capacitor-Clamped DC-DC Converter." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/66245999494816756250.

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碩士
國立成功大學
電機工程學系碩博士班
99
Grouped into two main categories of switched-inductor and switched-capacitor DC-DC power converters, the switching-mode DC-DC power converter is one of the widely used power electronic circuits. With many advantages over the switched-inductor type, the switched-capacitor DC-DC power converter topologies have been widely employed. In this thesis, on the basis of existing topology a zero-voltage and zero-current switching (ZVZCS) scheme for multilevel modular capacitor-clamped DC-DC converter (MMCCC) is proposed and analyzed. The proposed ZVZCS MMCCC circuit features that all switching devices of the circuit can achieve ZVZCS without the need of extra auxiliary switching devices. The proposed ZVZCS MMCCC can eliminate the Miller effect of the power MOSFETs during turn-on operation with the total driving losses reduced. Furthermore, there is no additional voltage and current stress on all switches out of the ZVZCS. A 200 W, four-level, three-module prototype ZVZCS MMCCC circuit has been implemented and verified through simulations and experiments. Superior performance of the proposed circuit to the existing topology has been demonstrated in the thesis.

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31

HOU, YU-YANG, and 侯昱揚. "Zero Field Switching of Perpendicular Synthetic Antiferromagnet by Spin Current." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/vp7t6v.

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碩士
國立中正大學
物理系研究所
105
A series of magnetic multilayered structures are fabricated by sputtering and the current induced magnetization switching by spin Hall effect is studied in this thesis. The samples include: Si(substrate)/ Ta(10)/ MgO(1)/ CoFeB(t1)/ Ru(2.2)/ CoFeB(1.0) / MgO(1) / Ta(3), t1= 1.0, 1.1,1.2,1.3,1.4,1.5,1.6 (units are nanometer). All samples are characterized by vibrating sample magnetometer (VSM) and the one with x= 1.4 is also measured by Hall resistance measurements. The anomalous Hal resistance (Rxy) measurements include the current scan Rxy(I) and field scan Rxy(H), respectively. Note that the Rxy(I)(Rxy(H)) is measured as function of a fixed field (fixed current) and all these results are then mapped to a comprehensive phase diagram. The main interests focus on the current scan Rxy(I). However, the analysis starts with Rxy(H) because these results provide useful information on the relevant magnetic states which help to for clarify the role of the spin current and symmetry of the trilayered structure The results of the sample with t1= 1.4 nm are divided into two parts: 1.The characterization of VSMD: the effective film thickness of the top CoFeB is 0.678nm and bottom CoFeB is 0.663nm.The total dead is 1.039nm.The magnetization of the multilayer is 1312.5emu/cm3, the anisotropy field is 2551 Oe, and the switching field is 606 Oe. 2. The results of anomalous Hall resistance measurements are further divided in to three parts: A. Rxy(Hz): The comparison of the Rxy(Hz) curve with the M (H) curve shows a significant change, which indicates the current effect due to spin current. The magnetic state varies from the z-direction to the orientation with part of the component in the y-direction. This change becomes significant at Current intensity more than 15 mA. Because of the results of positive and negative current measurements are invariant, this effect must be mainly affected by the field-like torque. The magnetic state also transforms from the antiferromagnetic state (a-state) into the spin flop state (v-state) as the current intensity is higher than 17mA. In addition, it reaches a critical point in the current field (Hz, I) diagram. At the critical point the magnetic state transforms from the a- state into the v-state. B. Rxy(Hx): The switching current density in Rxy(Hx) as a function of the Hx is mapped out in a current field (Hx, I) diagram. The diagram is qualitatively similar to (Hz, I) in which the magnetic states change significantly as current > 13mA. The critical current for the magnetic state transition process is smaller than the current required in the Hz direction. The magnetic orientation is not confined in the z-x plane but span in 3-dimentional space. It is presumed that the y-direction effective field is induced by the field-like torque while the z-direction effective field is induced by the damping-like torque due to Hx breaking the in-plane symmetry. A critical point is again identified at I > 13 mA, above which the v-sate and c-state are mixed. C. Rxy(I) : Rxy(I) measures the anomalous Hall resistance by current scan from 20 mA to – 20 mA with a fixed Hx. The CIMS is then studied as a function of Hx. The critical current is mapped out as a function of Hx and form a (I, Hx) diagram. Such diagram not only shows the symmetry of the operation but also gives rise the characteristic parameters including the effective spin Hall angel associated effective anisotropy field. We found that the diagram may be divided into a inner region (-100 Oe < Hx < – 100 Oe) and outer region elsewhere within the range of 500 Oe. The spin Hall angles in the inner and outer regions are θeff = 0.004 and 0.002, respectively. The associated effective anisotropy fields are Hk =597 Oe and 2607 Oe, respectively.

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32

Yang, Kai-Ping, and 楊愷平. "A Novel Loaded-Resonant Converter Using Zero-Current-Switching Topology." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/v6d4m9.

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碩士
崑山科技大學
電機工程研究所
101
Since the earth's energy is limited, use energy efficiently. It is important to enhance the efficiency of the converter in the field of DC to DC converter in power electronics. The resonant converter with soft switching the nature of the class-E resonance converter is currently the most known efficient converter, if we are able to take advantage of the class-E resonance converter, we can reduce unnecessary waste of energy. 　　The thesis is a novel loaded-resonant converter using zero current switching topology, its structure requires an input DC power supply, after the energy storage inductor reaches the switch for the switching operation, through the LC resonance circuit to oscillate, and then be filtered through a bridge rectifier through load, to achieve the DC-DC conversion, the advantage is it only requiring a switch to drive the circuit, and the switch reaches the soft switching, that is, zero current switching (Zero Current Switching, ZCS), the switching loss can be significantly reduced to improve efficiency. 　　After comparing the simulation and experimental results, we confirm the thesis of a novel loaded-resonant converter using zero current switching topology, the overall efficiency can be as high as 93.14%.

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33

Lee, Chin-hung, and 李志鴻. "Study and Analysis a Phase-Shifted Full Bridge Zero-Voltage and Zero-Current-Switching Converter for Current-Doubler Rectifier." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/42214979110880420091.

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碩士
國立臺灣科技大學
電機工程系
95
The purpose of this thesis is to study and analyze a DC/DC switching converter for high output current application, which consists of a phase-shifted full bridge soft switching converter and a current-doubler rectifier. The proposed phase-shifted full bridge soft switching converter has zero-voltage and zero-current-switching features. It realizes ZVS at the leading leg and ZCS at the lagging leg for full bridge switches to improve the drawbacks of the conventional phase-shift circuit with zero-voltage-switching. The current-doubler rectifier increases the efficiency of converter on the transformer secondary side in high output current applications. Therefore, high efficiency and high output current can be accomplished. The thesis describes the operation principles and design procedures for the proposed converter. The IsSpice simulation and the laboratory experiments verify the feasibility of the proposed scheme.

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34

楊岳霖. "Full-bridge phase-shifted zero-voltage and zero-current-switching converter using transformer auxiliary winding." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/16513832659936854844.

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35

夏存孝. "Modeling and Controller Design for Zero-Current-Zero-Voltage-Transition Soft-Switching Boost Power Converter." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/75525304553753788206.

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碩士
國立成功大學
工程科學系
89
In this thesis, the small signal mathematical model of a zero-current-zero-voltage-transition (ZCZVT) soft-switching boost power converter is proposed, and two controllers are also designed to achieve output voltage regulation. The ZCZVT soft-switching converter is composed of a conventional PWM circuit and a resonant circuit to achieve zero voltage/zero current switching (ZVS/ZCS) and constant frequency operation. This converter overcomes the existing problems of high switching losses of the conventional PWM converters and the conduction losses due to high voltage/current stresses of resonant converters. As a result, ZCZVT soft-switching converters are suitable for high power application system. In the literature, the soft-switching converters were only restricted to DC steady-state analysis. Most of researchers thought that the ac small signal mathematical model should be the same as that of the traditional PWM boost converter. Thus the derivation of the ac model has not been done yet. From the analysis results, the input-to-output voltage conversion ratio of the ZCZVT soft-switching converter depends on load. Moreover, the dynamical behavior will be changed under the variations of load. In this thesis, the averaging method for the two-time-scale discontinuous system (AM-TTS-DS) is used to derive the small signal model of a ZCZVT soft-switching converter. Based on this model, a classical controller and a modified integral variable structure controller (MIVSC) are then designed. The simulation responses and experimental results show that the MIVSC controller has better regulation capacity under the variations of load and line voltage variations than classical controller.

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36

Guo, You-Ruei, and 郭祐睿. "Single-Switch Zero-Current-Switching Topology with Series-Parallel Resonant Converter." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/70503089748845205460.

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碩士
崑山科技大學
電機工程研究所
99
Because of the advantages of small circuit size, light weight, low switching loss and high efficiency, resonant converters have now been widely used in various kinds of high-frequency switching converters to replace traditional hard-switching ones. The different combinations of the capacitance and inductance in resonant tank can produce different resonant effects and patterns. Besides, a resonant converter can also achieve ZCS (Zero Current Switching) or ZVS (Zero Voltage Switching) at the time of switching, which can reduce switching losses and enhance the efficiency of converters. Different from traditional class-D resonant converters that require two power switches, the class-E single-switch, ZCS, series-parallel resonant converter presented in this study used only a single switch to lower switching losses to significantly improve overall circuit efficiency. In this study an class-E converter was made based on the operation principle of converters, and the results of experiment and computer simulation analysis were satisfactory. The conversion efficiency of the converter could reach up to 92%.

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37

Chen, Hong-Wen, and 陳鴻文. "A Novel Parallel-Loaded Resonant Converter with Zero-Current-Switching Scheme." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/62994580269605466580.

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碩士
崑山科技大學
電機工程研究所
100
Serious electromagnetic interference (EMI) and cooling problems have been found in the traditional pulse width modulation (PWM) electronic converter. Moreover its switch has to receive a high level of switching stress and the defect of such a high switching losses which made the converter could not operate effectively in high-frequency environment, the raise in conversion efficiency has been facing the bottlenecks. In order to solve these shortcomings, the features of soft-switching in resonant converter, which can be used to do the improvement. The resonant converter will follow up the different connection ways of resonant slot and load, and produce different resonant forms and effects. By selecting appropriate component parameter, and adjusting the switching frequency, which enabled the switch in high frequency environment is easy to operate under the state of zero voltage switching (ZVS) or zero current switching (ZCS), to reduce the switching losses as well as to enhance the efficiency of the converter. This thesis proposed a novel parallel-loaded resonant converter with zero-current-switching scheme, which mainly uses class-E resonant inverter as basic circuit structure and then reinforced its design accordingly. Because of its function only with a single switch, as compared to use two switches of class-D resonant inverter, it not only can reduce the switching losses of a switch, but also increases the overall conversion efficiency. In addition to the characteristics of soft-switching, a novel parallel-loaded resonant converter with zero-current-switching scheme also owns a boosting characteristics. Furthermore, when adding the bridge rectifier and filter circuit to the output end, which makes the outputs end having stable DC voltage and current output. In general, this converter circuit has the advantages of a simple structure, the low cost and high conversion efficiency. The results is conducted through an actual measurement on hardware circuit, and experimental results that the high conversion efficiency of a novel parallel-loaded resonant converter with zero-current-switching scheme can be up to 96% in the final experiment.

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38

Chou, Kun-Hou, and 周廣豪. "A Study of Zero-Current-Switching Series-Resonant DC/AC Inverter." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/61913858392063929942.

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碩士
國立台灣工業技術學院
電子工程技術研究所
85
A new DC/AC inversion for achieving an AC sinusoidal waveform realized by series resonant technique is presented. The power switches are designed to operate at zero-current switching. This system is operated in a forced discontinuous-conduction mode (FDCM). The output power is mainly provided from the energy stored in the resonant capacitor and is independent of the number of resonant quasi-sinusoidal pulses. Three dynamic conversion states including charging, resonant, and RC- discharging states are analyzed. A design consideration for design, simulation , and experiment is explored. A design example of 300W DC/AC inverter is realized to assess the system performance.

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39

HuangShao-wei and 黃少崴. "A Novel Zero-Current-Switching Pulse-Width-ModulatedBuck Converter for Battery Chargers." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/56579758949419486814.

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碩士
崑山科技大學
電機工程研究所
94
The resonant converter provides the advantages of low switching losses, small circuit volume, light weight and high power density. Various high-frequency switching converters have replaced traditional hard -switching converters. This thesis presents a novel zero-current-switching pulse-width-modulated buck converter for battery chargers to control resonant converters flexibly. An auxiliary switch is inserted into the resonant loop in the proposed novel battery charger to control the resonant time precisely. The developed charger has the advantages of the hard-switching converter and the resonant converter with constant -frequency control, reduced resonant time and the operation of all switching components in the charger under the zero-current-switching condition to reduce significantly switching losses. The developed charger circuit is highly suitable for high-frequency operation and high charging efficiency. This thesis employs the pulse-width-modulated control mode for the switching of two active switches. The operation modes of the circuit and the equivalent circuits are constructed by analyzing the operating principles of the circuit, based on the turn-on conditions of the active switches. The equations used to determine the circuit parameters are derived from the equivalent circuits. Experimental results have demonstrated the theoretical effectiveness of the proposed novel battery charger circuit. A practical mean charging efficiency of over 90% is quite satisfactory.

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40

Huang, Jing-Yuan, and 黃敬原. "Design and Implementation of Interleaved Forward Quasi-Resonant Zero Current Switching Converters." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/39407695422272774652.

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碩士
國立成功大學
電機工程學系碩博士班
96
In this thesis, interleaved forward quasi-resonant (QR) zero current switching (ZCS) converters are studied and implemented. Two forward QR converters are parallel connected to increase output power. The interleaved technique is used to control the gate driver signals of two forward QR converters to reduce output current ripple. Also, the QR technique with ZCS is employed to reduce switching losses. The characteristics of the proposed converter are discussed, and the operation principles and design process are studied. Finally, interleaved forward QR ZCS converters with 200 V DC input voltage, 24V/10A output are implemented to verifying the theoretical analysis. Experimental results show that the switches are turned off with ZCS. The output inductor currents are balanced, and the output current ripple is reduced. Besides, the voltage regulation is ±1 %, and the efficiency is 90.9 % under 10 A output condition.

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41

Huang, Jian-Shuen, and 黃建舜. "Zero Field Current Switching by Spin Orbit Torque in Coupled Ferromagnetic Layers." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/53530330114939521556.

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碩士
國立中正大學
物理學系暨研究所
103
When a current passes through a heavy metal, such as Ta or Pt, a spin current may be generated along the transverse direction. This spin current has been observed recently and used for magnetic switching in MgO/CoFeB/Ta or Pt/Cu layered structures, which are perpendicularly magnetized. In this thesis we fabricated Hall bars from thin film samples of synthetic antiferromagnetic structure MgO(1)/CoFeB(1.2)/Ta(1.0 and 2.3)/CoFeB(1.2)MgO(1) (unit: nm) and applied in-plane current to switch the magnetic moment. The Hall resistance measurements include current switch (fixed external field) and field switch (fixed current density) and phase diagrams of the magnetic states are mapped out for each sample. Besides, we found that the switching process exists is influenced by the exchange coupling which depends upon the thickness of Ta. From the Hall resistance results, Ta=1.0 structure is classified as an antiparallel coupled condition while Ta=2.3 is classified as a weak parallel coupled condition. Other major observations included (1) The loop of current switching has a shift that J-H magnetic phase diagram is not symmetric. In Ta=1.0, the positive and negative switching current density are J=±40MA/cm2 with a low magnetic field. When the magnetic field is increased, the positive switching current density is still J=+40MA/cm2 but the negative switching current density becomes J=-20MA/cm2 with the magnetic field Hx=±200Oe. In Ta=2.3,the positive switching current density becomes J=+25MA/cm2 but the negative switching current density keeps J=-36MA/cm2 when the magnetic field increases to Hx=-200Oe. (2) Current switching is different from conventional magnetic field switching, the former is mirror symmetry and the later is inversion symmetry. (3) More interestingly, in the past monolayer structure switching by current needed a external magnetic field to break symmetry,but we found that these coupled systems show zero-field switching indicating the up-down symmetry is intrinsically broken. We got the spin Hall angle is probably 0.063 which is calculated from the switching current density J=40MA/cm2coinciding with the references, and this feature may have application potential. keywords: spin Hall effect、spin torque、current switch、synthetic antiferromagnetic structure、CoFeB

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42

Yeh, I.-Chun, and 葉怡君. "A Novel Zero-Current-Zero-Voltage-Transition Soft-Switching AC/DC Rectifier with High Power Factor Correction." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/12260443214002612857.

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碩士
國立成功大學
工程科學系碩博士班
91
The conventional AC/DC converters commonly are composed of two stages. One is power factor correction stage, and the other is output voltage regulation stage. It thereby needs two switches, and thus causes more costs. To overcome the drawback, the components placement is applied to combine buck-boost and flyback converters into a single-stage isolated HPFC converter. On the basis of the single-stage circuit, the soft-switching technology is then applied to design a novel zero-current-zero-voltage-transition (ZCZVT) soft-switching AC/DC rectifier with high power factor correction. The ZCZVT soft-switching converter exhibits the advantages of both ZVT and ZCT converters. It improves the efficiency of the power converters. To achieve zero voltage switching and zero current switching during switching transitions, the auxiliary switch turns on twice, and thus two resonances occur in one switching period. This converter overcomes the existing problems of high switching losses of the conventional PWM converters and the conduction losses due to high voltage/current stresses of resonance power converters. The AC/DC power converter must exhibit the ability of power factor correction and output voltage regulation. In addition, the voltage of the bulk capacitor is invariant with the load variations. It reveals from the detailed circuit analysis that the high voltage stress of the bulk capacitor is avoided while the power converter is operating in DCM+DCM mode. The power converter discussed in this thesis has inherent gift of PFC when buck-boost converter in the first stage is operating in DCM mode. Hence the PFC controller is not needed. Furthermore, The two-time-scale averaging method is used to derive the small-signal mathematical model of the converter in the switching period, and then derive the averaged model in the line period. The theoretical results can be verified with experimental measurements. Finally on the basis of the derived model, an output voltage regulation controller is designed to eliminate the effect of the variations of line voltage and load on the output voltage.

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43

Chen, Wen-Chung, and 陳文鍾. "Study and Implementation of a Current-Fed Push-Pull High Voltage Converter with Zero-Current Switching." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/45171022539630995950.

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碩士
國立成功大學
電機工程學系碩博士班
96
In this thesis, a current-fed push-pull high voltage converter with zero-current switching (ZCS) is studied and implemented. The first stage is a buck converter that utilizes pulse width modulation (PWM) to regulate the output voltage. The second stage is a push-pull converter which is used to transfer energy from low voltage side to high voltage side. Moreover, the stray components of the high voltage transformer are integrated into the resonant tank of the current-fed push-pull converter. Thus, the proposed converter can achieve ZCS operation of the active switches of the push-pull converter, and the unpredictable resonant phenomenon can be avoided. The characteristics of the various topologies are expressed. The operating principles of the proposed converter are presented, and the steady-state analysis is also discussed in this thesis. Finally, a laboratory prototype with 400 V input and 5 kV/1 kW output is implemented to verify the theoretical analysis.

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44

楊學智. "Zero-Voltage and Zero-Current-Switching(ZVZCS) Full-Bridge PWM Converter Using a Simple Reset Current Principle of the Inverse Diodes in Series." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/01025025871065122573.

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碩士
國立海洋大學
電機工程學系
90
It has been known that PWM converter needs to flow all load current as switch is changed. The switch needs to bear higher changed stress and loss which is in proportion to the frequency of switch. Besides, both di/dt and dv/dt produced from change can cause severe EMI. In order to lower volume and weight of converter its frequency needs to be raised for increasing power density. However, it makes defect of switch converter worse than before. The thesis uses full-bridge PWM ZVZCS converter to improve switch loss and increase the efficiency of system under high switching frequency. We use inverse series of two diodes at the end of circuit. They not only attain the effect of major current reset but also don’t need to enhance auxiliary winding or active clamp for assistance. We combine theory with computer simulation to prove it.

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45

SieJian-Wun and 謝健文. "Battery Charger of a Novel Zero-Current-Switching Buck Converter for Photovoltaic Modules." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/33457159256246959727.

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碩士
崑山科技大學
電機工程研究所
95
As a clean and renewable source, solar energy has been used widely in recent years. Solar energy generation systems generally consist of a photovoltaic array, which converts sunlight into electrical energy as the solar cells produce a flow of electrons through the absorption of light photons, and a energy storage device. Batteries are used to store the excess available energy from the photovoltaic array during the day and provide energy for the load during the times of little or no sun. The main drawbacks of solar energy generation systems are high fabrication cost, and low energy conversion efficiency. For increasing conversion efficiency, many charging techniques have been proposed and implemented. A simple, fast and reliable converter for rechargeable batteries with soft-switching schemes by photovoltaic arrays is proposed. Simply by inserting an auxiliary switch in series with the resonant capacitor in the traditional zero-current switching converter, a novel zero-current switching converter for battery charger is obtained in this paper. Moreover, when compared with the battery charger with the traditional pulse-width-modulated one, the novel battery charger with zero-current switching converter indeed reduces the loss between the switch voltage and the switch current of the active power switch, resulting in the reduction of switch losses. The optimal circuit parameters of the novel battery charger are designed by applying the frequency response curve and electric functions derived from the circuit configuration. The main advantages of the proposed battery charger as compared with conventional one are shorter charging time, higher efficiency and lower cost. Finally, the experimental test results are illustrated to show the efficiency of the topology, and the charging efficiency is as high as 85%.

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46

LIU, XING-FU, and 劉興富. "Steady-state analysis and design of^^zero-current-switching resonant DC/DC converter." Thesis, 1991. http://ndltd.ncl.edu.tw/handle/44501903550247876289.

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47

Lin, Yuang-Shing, and 林永祥. "Multiple Output/Input Zero-Current-Switching Switched-Capacitor Bi-directional DC-DC Converter." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/74609719356434117207.

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碩士
輔仁大學
電子工程學系
95
This thsis proposes multiple-output/input zero-current-switching (ZCS) switched–capacitor bi-directional power flow control conversion schemes. The principle of the proposed bi-directional power conversion scheme is described in detailed circuit model analysis. Simulation and experimental results are carried out to verify the validity and the soft switching performance of the proposed multiple-output/input zero-current-switching switched–capacitor bi-directional dc-dc converter. The maximum efficiency can achieve about 93% and 94% for the forward and reverse power flow control schemes, respectively. Multiple output/input ZCS SC converter can easily extended m/ mode and n/ mode by using different voltage conversion reaio.

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48

Liao, Jian-Cheng, and 廖建程. "A Novel Single-Switch Series-Loaded Resonant Converter with Zero-Current-Switching Scheme." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/45549501618012652873.

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碩士
崑山科技大學
電機工程研究所
100
Up to now the class-E resonant converter of all kinds is the most efficient converter. The converter shows with low electromagnetic interference, low switching losses, smaller size, high efficiency and low cost advantages. In the high frequency mode, the resonant converter caused by the different resonance effects due to the different permutations and combinations of the resonance of the resonant tank inductor and resonant power. The resonant converter when the power transistor does the switch could achieve the zero voltage switching or the zero current switching, so that is able to reduce the loss at the power switch. To enhance the efficiency of the conversion rate and reduce unnecessary waste of energy the time of the switch. This thesis presents a new single-switch series load resonant converter. Using the power switch at zero current operating effectively reduces the switching losses, and promotes the efficiency of the converter. Besides only using the single switch runs high-frequency switching, Compared with traditional class-D converter would obtain the higher conversion efficiency, and the combination of the resonant tank consisting of inductors and capacitors produces the desired voltage and current. At the same time by adjusting the switching frequency of the power switch achieves the flexible switching characteristics, and controls the output voltage and current. Distal of this thesis would implement a series of load converter switch of new single-component parameters, specifications and simulation results, and then are compared with each others to verify the proposed new single-switch zero-current switching series load resonant converter. Finally, the experimental results show that this new single-switch zero-current switching series load resonant converter, the overall circuit efficiency by up to 96%. The result shows quite good, and also achieve the desired goals or more.

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49

Hung, YA-Hsu, and 洪雅勗. "Design and Implementation of a Two-Switch Forward Converter with Zero-Current-Switching." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/12286166559859086960.

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碩士
國立成功大學
電機工程學系碩博士班
96
In this thesis, a two-stage AC-DC power supply is studied and implemented. The front stage is a power factor correction AC-DC boost converter, and the rear stage is a two-switch forward DC-DC converter, which is suitable in the high input voltage applications. Also, the quasi-resonant technology is applied to this converter to reduce the switching losses and improve efficiency. First, the characteristics of forward converters are discussed. Secondly, the operation principles and design process of the two-switch forward converter are analysis. Finally, the two-stage power supply with universal AC input voltage 90 V~264 V, DC output voltage 24 V, and DC output current 10 A is implemented to verify the performance of the propose circuit.

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50

CHEN, YI-HSUAN, and 陳毅軒. "Current Induced Zero Field Switching in Perpendicularly Magnetized MgO/CoFeB/W/CoFeB/MgO." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/9b68uq.

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碩士
國立中正大學
物理系研究所
106
A series of magnetic multilayered structures are fabricated by sputtering and the current induced magnetization switching by spin Hall effect is studied in this thesis. The samples include: Si(substrate)/Ta(10)/MgO(1)/CoFeB(x)/W(1)/CoFeB(1.1)/MgO(1)/Ta(3), x= 1.2, 1.3, 1.4 (units are nanometer). All samples are characterized by vibrating sample magnetometer (VSM) and the one with x= 1.4 is also measured by Hall resistance measurements. The anomalous Hall resistance (Rxy) measurements include the current scan Rxy(I) and field scan Rxy(H). The results of sample x=1.4 nm are divided into two parts: 1.The characterization of VSM: the effective film thickness of the top CoFeB is 0.649 nm and bottom CoFeB is 0.511 nm. The total dead layer is 1.34 nm. The magnetization of the multilayer is 1600 emu/cm3, the anisotropy field is 4000 Oe, and the switching field is 300 Oe. 2.The results of anomalous Hall resistance measurements are further divided in to three parts: A.Rxy(Hz): The comparison of the Rxy(Hz) curve with the M(H) curve shows a significant change. The magnetic state varies as current density varies, indicating the current effect due to spin current. This change becomes significant at Current intensity more than ±12 mA, it changed from three magnetic states to four magnetic states. Because of the results of positive and negative current measurements are invariant, this effect must be mainly affected by the field-like torque. The magnetic state varies from the z-direction to the orientation with part of the component in the y-direction. So we can find the critical point (± 12 mA) in the diagram. At the critical point the magnetic state transforms from the a-state into the c-state. B.Rxy(Hx): The results of field scan Rxy(Hx) show that the magnetic states change between c-state and inverse c-state by current induced Hz,eff. No obovios spin flop state (v-state) is observed probably because the anisotropy energy is lager than the indicating a strong spin current effect. Basically, the magnetic moments are confined in z-x plane at low current density but the gradually change to be confined z-y plane at I>12mA. C.Rxy(I): Rxy(I) measures the anomalous Hall resistance by current scan from 25 mA to – 25 mA with a fixed Hx. The critical current can also be seen in the (J-Hx) phase diagram. We found that the diagram may be divided into a inner region (-100 Oe < Hx < 100 Oe) and outer region elsewhere within the range of 500 Oe. At inner region the switching current is more than the critical current and the slope is larger than outer region. Zero field switching is also observed indicating that the field like torque may initiate process and break the in-plane symmetry.

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