Dissertations / Theses: 'LLC resonant converters'

1

Person, Clark Edwin. "Selection of Primary Side Devices for LLC Resonant Converters." Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/31746.

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The demand for high power density, high efficiency bus converters has increased interest in resonant topologies, particularly the LLC resonant converter. LLC resonant converters offer several advantages in efficiency, power density, and hold up time extension capability. Among high voltage (>500V) MOSFETs, Super Junction MOSFETs, such as Infineonâ s CoolMOS parts, offer lower Rds on than conventional parts and are a natural choice for this application to improve efficiency. However, there is a history of converter failure due to reverse recovery problems with the primary switchâ s body diode. Before selecting CoolMOS devices for use in a LLC resonant converter, it is necessary to investigate its performance in this application. Field failures of PWM soft switching phase shift full bridge converters have been attributed to large reverse recovery charge in the primary side MOSFET body diode. Under low load conditions the device cannot fully recover, and the large reverse recovery current can cause the device to enter secondary break down, leading to failure. The unique structure of Super Junction MOSFETs, such as CoolMOS, avoid this failure mode by providing a different path for the reverse current; however, the reverse recovery charge of CoolMOS devices is large and can cause a loss of efficiency. For this reason, it is important to avoid conditions under which the reverse recovery characteristics of the body diode can be seen.
Master of Science

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2

Feng, Weiyi. "State-Trajectory Analysis and Control of LLC Resonant Converters." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/19327.

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With the fast development of communication systems, computers and consumer electronics, the power supplies for telecoms, servers, desktops, laptops, flat-panel TVs, LED lighting, etc. are required for more power delivery with smaller spaces. The LLC resonant converter has been widely adopted for these applications due to the advantages in high efficiency, high power density and holdup time operation capability.
However, unlike PWM converters, the control of the LLC resonant converter is much more difficult because of the fast dynamic characteristic of the resonant tank. In some highly dynamic processes like the load transient, start-up, over-load protection and burst operation, it is hard to control the current and voltage stresses and oscillations in the resonant tank. Moreover, to meet the high power density requirement, the LLC is required to operate at a high switching frequency. Thus the driving of the synchronous rectifier (SR) poses a design challenge as well.
To analyze the fast dynamic characteristic, a graphic state-plane technique has been adopted for a class of resonant converters. In this work, it has been extended to the LLC resonant converter. First of all, the LLC steady state and dynamic behaviors are analyzed in the state plane. After that, a simplified implementation of the optimal trajectory control is proposed to significantly improve the load transient response: the new steady state can be tracked in the minimal period of time.
With the advantages of the state-trajectory analysis and digital control, the LLC soft start-up is optimized as well. The current and voltage stress is limited in the resonant tank during the start-up process. The output voltage is built up quickly and smoothly.
Furthermore, the LLC burst mode is investigated and optimized in the state plane. Several optimal switching patterns are proposed to improve the light load efficiency and minimize the dynamic oscillations. During the burst on-time, the LLC can be controlled to track the steady state of the best efficiency load condition in one-pulse time. Thus, high light-load efficiency is accomplished.
Finally, an intelligent SR driving scheme is proposed and its simple digital implementation is introduced. By sensing the SR drain to source voltage and detecting the paralleled body diode conduction, the SR gate driving signal can be tuned within all operating frequency regions.
In conclusion, this work not only solves some major academic problems about analysis and control of the LLC resonant converter based on the graphic state plane, but also makes significant contributions to the industry by improving the LLC transient responses and overall efficiency.
Ph. D.

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3

Yu, Ruiyang, and 余睿阳. "Design optimization of off-line power converters: from PWM to LLC resonant converteres." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B49799642.

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High power conversion efficiency is desirable in power supplies. Design optimization of on-line power converter is presented in this thesis. High efficiencies over a wide load range, for example 20%, 50% and 100% load, are often required. It is a challenge for on-line pulse-width modulation (PWM) converters to maintain good efficiencies with light load as well as full load. A two-stage multi-objective optimization procedure is proposed to optimization power converter efficiencies at 20%, 50% and 100% load. Two-FET forward prototype converters are built to verify the optimization results. The LLC (abbreviation of two resonant inductor L and one resonant capacitor C ) series resonant converter can provide high power conversion efficiency because of the resonant nature and soft switching. The design of LLC resonant converter is more difficult than that of PWM converters since the LLC resonant converter has many resonant modes. Furthermore, the LLC resonant converter does not have analytical solution for its resonant operation. In this thesis, a systematic optimization procedure is proposed to optimize LLC series resonant converter efficiency. A mode solver technique is developed to solve LLC resonant converter operations. The proposed mode solver employs non-linear programming techniques to solve a set of LLC state equations and determine the resonant modes. Loss models are provided which serve as the objective-function to optimize converter efficiency. Optimization results show outstanding efficiency performance and experimental agreement with optimization. The optimization work extends to the LLC resonant converter with power factor correction (PFC) circuits where the effect of LLC converter input voltage variation cased by the PFC circuit is considered. Detail comparisons of PWM converter and LLC resonant converter loss profiles are also presented. The reasons that LLC resonant converter has higher efficiency are given and supported by quantitative data. Converter lifetime is highly related to component losses and temperature. The lifetime analysis is presented. The analysis reveals that the LLC resonant converter output capacitor is the weakest component concerning life.
published_or_final_version
Electrical and Electronic Engineering
Doctoral
Doctor of Philosophy

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4

Ho, Kwun-yuan Godwin, and 賀觀元. "A novel integrated synchronous rectifier for LLC resonant converter." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B49618180.

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There is ever-increasing demand in telecommunication system, data server and computer equipment for low voltage, high current power supply. LLC resonant converter is a good topology on primary side of the converter because it has soft switching and resonant conversion. However, the passive rectifier in the secondary side has high power dissipation. Synchronous rectifier is a popular method to reduce this rectification loss. Although there are many types of synchronous rectifier for PWM converter, most of them do not function well in LLC resonant converters. It is because the wave form of LLC resonant converter is different from PWM. The objective of this research is to reduce the power dissipation and physical size at the same time. In this thesis, a novel current driven synchronous rectifier with saturable current transformer and dynamic gate voltage control for LLC resonant Converter is presented. This novel circuit reduces the rectification loss and size of the current transformer in the synchronous rectifier. This synchronous rectifier has several outstanding characteristics compared with generic voltage driven and current driven synchronous rectifier. The saturable feature reduces the current transformer turns. Inherent dynamic gate voltage controlled by saturable current transformer reduces gate loss in the MOSFET. A novel driving circuit is proposed for accurate turn off time. It reduces loss significantly. This synchronous rectifier is completely self-contained which can replace the rectifier diode as a drop in replacement. It is insensitive to parasitic inductance. In order to explain the current transformer saturable, a model of saturable current transformer is proposed. A prototype demonstrates the advantages of the proposed current driven synchronous rectifier. Furthermore, a novel integrated synchronous rectifier is presented which provides a more compact system. The synchronous rectifier current transformer is integrated with the main transformer which reduces the number of circuit joints in power path. Each soldering joint generates significance loss in power converter. A pair of 0.5mΩ soldering joint in 25A current path produces 0.62W loss. The placement of the integrated current transformer is important. A criterion for the placement of the current transformer within the main transformer is to avoid interference to the current transformer from the magnetic flux of the main transformer. Thus, a placement method to integrate the current transformer into the main transformer is proposed. An integrated current transformer model is suggested to explain the operation of the integrated synchronous rectifier. A prototype demonstrates the advantages of the integrated synchronous rectifier.
published_or_final_version
Electrical and Electronic Engineering
Master
Master of Philosophy

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5

Huang, Daocheng. "Investigation of Topology and Integration for Multi-Element Resonant Converters." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/24909.

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With the fast development of communication systems, computers and consumer electronics, the power supplies for telecoms, servers, desktops, laptops, flat-panel TVs, LED lighting, etc. are required for more efficient power delivery with smaller spaces. The LLC resonant converter has been widely adopted for these applications due to the advantages in high efficiency, high power density and holdup time operation capability. However, LLC resonant converter meets some issues, especially in high output current applications. Those issues include magnetic design, start-up, short-circuit protection, synchronous rectifier drive, EMI noise and integration, etc. To solve those issues, like start-up and short-circuit protection, SR driving and EMI, etc., a synthesis method is proposed to find the similar resonant topologies like LLC. Based on this method, lots of multi-element resonant converters are found to solve the issues that LLC resonant converter cannot handle. To evaluate the performance of found numerous valuable topologies. Thus, a general evaluation system is required. State-plane analysis with new normalization factors is utilized. Based on it, the voltage stress, current stresses and apparent power of resonant converters are easy to compare. This method can help select suitable circuit topology for certain applications. Meanwhile, it also can help resonant converters' design. The important performance factors, like start-up, short-circuit protection, SR driving, integration and EMI performance, are also taken into account for the whole evaluation system. The high switching frequency is needed recently for high power density requirement. However, LLC resonant converter suffers high transformer loss. Matrix transformer is introduced to reduce winding loss and total volume. Flux cancellation method is utilized to reduce core size and loss. Synchronous Rectifier (SR) devices and output capacitors are integrated into secondary windings to eliminate termination related winding losses, via loss and reduce leakage inductance. The passive integration is necessary for high power density resonant converter, especially for high order system. Based on stress, suitable passive components are chosen for integration. Then, the magnetic integration method is shown based on multi-winding transformer structure. The passive integration principles are discussed. A novel passive integration method is proposed for multi-elements resonant converters. In conclusion, this work is focus on the topology analysis and integration of resonant converters. Searching the suitable topologies for certain application, and evaluate the performance of them. Then, improve the system power density by integration techniques.
Ph. D.

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6

Hsieh, Yi-Hsun. "Accurate Small-Signal Modeling for Resonant Converters." Diss., Virginia Tech, 2020. http://hdl.handle.net/10919/100941.

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In comparison with PWM converters, resonant converters are gaining increasing popularity for cases in which efficiency and power density are at a premium. However, the lack of an accurate small-signal model has become an impediment to performance optimization. Many modeling attempts have been made to date. Besides the discrete time-domain modeling, most continuous-time modeling approaches are based on fundamental approximation, and are thus unable to provide sufficient accuracy for practical use. An equivalent circuit model was proposed by Yang, which works well for series resonant converters (SRCs) with high Q (quality factor), but which is inadequate for LLC resonant converters. Furthermore, the model is rather complicated, with system orders that are as high as five and seven for the SRC and LLC converter, respectively. The crux of the modeling difficulty is due to the underlying assumption based on the use of a band-pass filter for the resonant tank in conjunction with a low-pass output filter, which is not the case for most practical applications. The matter is further complicated by the presence of a rectifier, which is a nonlinearity that mixes and matches the original modulation frequency. Thus, the modulation signal becomes intractable when using a frequency-domain modeling approach. This dissertation proposes an extended describing function modeling that is based on a Fourier analysis on the continuous-time-domain waveforms. Therefore, all important contributions from harmonics are taken into account. This modeling approach is demonstrated on the frequency-controlled SRC and LLC converters. The modeling is further extended to, with great accuracy, a charge-controlled LLC converter. In the case of frequency control, a simple third-order equivalent circuit model is provided with high accuracy up to half of the switching frequency. The simplified low-frequency model consists of a double pole and a pair of right-half-plane (RHP) zeros. The double pole, when operated at a high switching frequency, manifests the property of a well-known beat frequency between the switching frequency and the resonant frequency. As the switching frequency approaches the resonant frequency of the tank, a new pair of poles is formed, representing the interaction of the resonant tank and the output filter. The pair of RHP zeros, which contributes to additional phase delay, was not recognized in earlier modeling attempts. In the case of charge control, a simple second-order equivalent circuit model is provided. With capacitor voltage feedback, the order of the system is reduced. Consequently, the resonant tank behaves as an equivalent current source and the tank property is characterized by a single pole. The other low-frequency pole represents the output capacitor and the load. However, the capacitor voltage feedback cannot eliminate the high-frequency poles and the RHP zeros. These RHP zeros may be an impediment for high-bandwidth design if not properly treated. Based on the proposed model, these unwanted RHP zeros can be mitigated by either changing the resonant tank design or by proper feedback compensation. The accurate model is essential for a high-performance high-bandwidth LLC converter.
Doctor of Philosophy
For high-frequency power conversion, resonant converters are increasingly popular. However, the lack of an accurate small-signal model has become an impediment to performance optimization. The existing equivalent circuit model and its simplified circuit were based on fundamental approximation, where the resonant tank was deemed a good band-pass filter. These models work well for series resonant converters (SRCs) with high Q (quality factor), but are inadequate for LLC resonant converters. The crux of the modeling difficulty is due to the fact that the operation of this type of resonant converter is based on the use of a band-pass filter in conjunction with a low-pass filter. The matter is further complicated by the presence of a rectifier, which is a nonlinearity that mixes and matches the original modulation frequency. Thus, the modulation signal becomes intractable when using a frequency-domain modeling approach. This dissertation proposes an extended describing function modeling that is based on a Fourier analysis on the continuous-time-domain waveforms. Therefore, all important contributions from harmonics are taken into account. This modeling approach is demonstrated on the frequency-controlled SRC, frequency-controlled LLC converter, and charge-controlled LLC converter, and the resulting models are proven to be accurate at all frequencies. A simple equivalent circuit model is provided that targets the frequency range below the switching frequency. This simple, accurate model is able to predict the small-signal behaviors of the LLC converter with high accuracy at half of the switching frequency. At high modulation frequencies, the resonant converter behaves like a non-minimum phase system, which was neither recognized nor characterized before. This property can be represented by RHP zeros, and these RHP zeros may be an impediment for high-bandwidth design if not properly treated. Based on the proposed model, these unwanted RHP zeros can be mitigated by either changing the resonant tank design or by proper feedback compensation. Accurate modeling is essential for a high-performance high-bandwidth LLC converter.

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7

Tian, Shuilin. "Equivalent Circuit Model of High Frequency PWM and Resonant Converters." Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/56676.

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Distributed power system (DPS) is widely adopted in Power supplies for the telecom, computer and network applications. Constant on-time current mode control and V2 control are widely used as point-of-load (POL) converters and voltage regulators (VR) in DPS systems. Series resonant converters (SRC) are widely used in aerospace systems and LLC resonant converters are widely used as Front-end converters in DPS systems. The technological innovations bring increasing demand for optimizing the dynamic performance of the switching regulators in these applications. There has been a strong desire to develop simple and accurate equivalent circuit models to facilitate the design of these converters. Constant on-time current-mode control has been widely used in POL and VRM converters. For multi-phase application, external ramp is required to improve jittering performance using pulse distribution method. Chapter II analyzes the effect of external ramp on small-signal model of constant on-time current mode control. It is found that external ramp brings additional dynamics by introducing a moving pole and a static zero. Next, a three-terminal switch model is proposed based on non-ideal current source concept, where the non-idealness of the current source is presented by a Re2-Le2 branch. Based on the proposed model, design guidelines are proposed based on either worst case design strategy or auto-tuning strategy. V2 control has advantages of simple implementation and fast transient response and is widely used in industry for POL and VR applications. However, the capacitor voltage sideband effect, which casues the instability problem when ceramic capacitors are employed, also needs to be taken into consideration in modeling. Chapter III proposed a unified equivalent circuit model of V2 control, the model is built based on non-ideal voltage source concept. The model represents capacitor voltage sideband effect with a Re2-Le2 branch, which forms the double pole by resonating with power stage output capacitor. The equivalent circuit model is a complete model and can be used to examine all the transfer functions. Bsed on the unified equivalent circuit model, design guidelines for VR applications and general POL applications are provided in Chapter IV, for both constant on-time V2 control and constant frequency V2 control. For resonant converters, the small-sginal modelling is very challenging as some of the state variables do not have dc components but contain strong switching frequency component and therefore the average concept breaks down. For SRC, the equivalent circuit model proposed by E. Yang in [E26] based on the results by the extended describing function concept is the most successful model. However, the order of the equivalent circuit model is too high and the transfer functions are still derived based on numerical solution instead of analytical solutions. Chapter V proposes a methodology to simplify the fifth-order equivalent circuit of SRC to a third-order equivalent circuit. The proposed equivalent circuit model can be used to explain the beat frequency dynamics: when switching frequency is far away from resonant frequency, beat frequency will occur; when the two frequencies are close, beat frequency will disappear and another double pole which is determined by equivalent inductor and output capacitor will be formed. For the first time, analytical solutions are provided for all the transfer functions which are very helpful for feedback design. LLC resonant converters are widely adopted as front-end converter in distributed power system for the telecom, computer and network applications [F2]. Besides, LLC resonant converters are also very popular in other applications, such as LCD, LED and plasma display in TV and flat panels [F3]-[F6]; iron implanter arc power supply[F7]; solar array simulator in photovoltaic application[F8]; fuel cell applications[F9],and so on. For LLC, no simple equivalent circuit model is available and no analytical expressions of transfer functions are presented. Chapter VI proposes an equivalent circuit model for LLC resonant converter. When Fs ≥ Fo, Lm is clamped by the output voltage and LLC behaves very similar as SRC. As a result, the dynamic behavior is similar as SRC: when switching frequency is larger than resonant frequency, the beat frequency double pole show up and the circuit is third-order; when switching frequency is close to resonant frequency, beat frequency double pole disappear and a new double pole formed by equivalent inductor Le and equivalent output capacitor Cf show up. The circuit reduces to second order. When FsPh. D.

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8

Fei, Chao. "Optimization of LLC Resonant Converters: State-trajectory Control and PCB based Magnetics." Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/83206.

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With the fast development of information technology (IT) industry, the demand and market volume for off-line power supplies keeps increasing, especially those for desktop, flat-panel TV, telecommunication, computer server and datacenter. An off-line power supply normally consists of electromagnetic interference (EMI) filter, power factor correction (PFC) circuit and isolated DC/DC converter. Isolated DC/DC converter occupies more than half of the volume in an off-line power supply and takes the most control responsibilities, so isolated DC/DC converter is the key aspect to improve the overall performance and reduce the total cost for off-line power supply. On the other hand, of all the power supplies for industrial applications, those for the data center servers are the most performance driven, energy and cost conscious due to the large electricity consumption. The total power consumption of today's data centers is becoming noticeable. Moreover, with the increase in cloud computing and big data, energy use of data centers is expected to continue rapidly increasing in the near future. It is very challenging to design isolated DC/DC converters for datacenters since they are required to provide low-voltage high-current output and fast transient response. The LLC resonant converters have been widely used as the DC-DC converter in off-line power supplies and datacenters due to its high efficiency and hold-up capability. Using LLC converters can minimize switching losses and reduce electromagnetic interference. Almost all the high-end offline power supplies employs LLC converters as the DC/DC converter. But there are three major challenges in LLC converters. Firstly, the control characteristics of the LLC resonant converters are very complex due to the dynamics of the resonant tank. This dissertation proposes to implement a special LLC control method, state-trajectory control, with a low-cost microcontroller (MCU). And further efforts have been made to integrate all the state-trajectory control function into one MCU for high-frequency LLC converters, including start-up and short-circuit protection, fast transient response, light load efficiency improvement and SR driving. Secondly, the transformer in power supplies for IT industry is very bulky and it is very challenging to design. By pushing switching frequency up to MHz with gallium nitride (GaN) devices, the magnetics can be integrated into printed circuit board (PCB) windings. This dissertation proposes a novel matrix transformer structure and its design methodology. On the other hand, shielding technique can be employed to suppress the CM noise for PCB winding transformer. This dissertation proposes a novel shielding technique, which not only suppresses CM noise, but also improves the efficiency. The proposed transformer design and shielding technique is applied to an 800W 400V/12V LLC converter design. Thirdly, the LLC converters have sinusoidal current shape due to the nature of resonance, which has larger root mean square (RMS) of current, as well as larger conduction loss, compared to pulse width modulation (PWM) converter. This dissertation employs three-phase interleaved LLC converters to reduce the circulating energy by inter-connecting the three phases in certain way, and proposed a novel magnetic structure to integrated three inductors and three transformers into one magnetic core. By pushing switching frequency up to 1MHz, all the magnetics can be implemented with 4-layer PCB winding. Additional 2-layer shielding can be integrated to reduce CM noise. The proposed magnetic structure is applied to a 3kW 400V/12V LLC converter. This dissertation solves the challenges in analysis, digital control, magnetic design and EMI in high-frequency DC/DC converters in off-line power supplies. With the academic contribution in this dissertation, GaN devices can be successfully applied to high-frequency DC/DC converters with MHz switching frequency to achieve high efficiency, high power density, simplified but high-performance digital control and automatic manufacturing. The cost will be reduced and the performance will be improved significantly.
Ph. D.

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9

Fei, Chao. "Microcontroller (MCU) Based Simplified Optimal Trajectory Control (SOTC) for High-Frequency LLC Resonant Converters." Thesis, Virginia Tech, 2015. http://hdl.handle.net/10919/78117.

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The LLC resonant converter has been widely used as a DC-DC converter due to its high efficiency, high power density and hold-up capability in power supplies for communication systems, computers and consumer electronics. Use of the high-frequency LLC converter has also been increasing in recent years due to its high power density and integrated magnetics, which reduce the total cost. With the fast development of wideband gap devices and novel magnetic materials, the trend of pushing switching frequency higher continues. However, the control characteristics of the LLC resonant converter are much more complex than that of the PWM converter due to the dynamics of the resonant tank. This paper employs state-trajectory analysis to describe and analyze the behavior of the resonant tank. Control methods based on state-trajectory analysis were used to solve the challenges in the control of the LLC resonant converter, including unpredictable dynamics, burst mode for light-load efficiency, soft start-up and short circuit protection. Additionally, digital controllers are gradually taking the place of analog controllers in the control of the LLC resonant converter due to the advantages of the digital controllers over the analog controllers, such as their ability to be flexible and re-configurable, capable of non-linear control, and able to communicate with other controllers. Among the digital controllers, cost-effective microcontrollers (MCU) are preferred for industrial applications. Because of the advantages of the state-trajectory control and the industrial preference in the cost-effective digital controllers, it would be of great benefit to apply state-trajectory control to high-frequency LLC converters with cost-effective digital controllers. This thesis investigates the impact of digital delay on state-trajectory control. Simplified Optimal Trajectory Control (SOTC) for LLC converters is further simplified so that SOTC can be achieved with cost-effective digital controllers. Furthermore, the limitations caused by digital controller are explained in detail, and methods are proposed to apply the SOTC to high frequency LLC converter is proposed. A detailed analysis of fast load transient response, soft start-up, burst mode for light-load efficiency and synchronous rectification (SR) driving is provided. Multi-step SOTC for fast load transient response is proposed to apply cost-effective digital controllers to high-frequency LLC converters; SOTC for soft start-up with only sensing Vo is proposed to minimized the impact of digital delay on state-trajectory control; SOTC for burst mode with multi-step is proposed to eliminate the limitation of minimum off-time caused by digital controllers in constant burst-on time control; a generalized adaptive SR driving method using the ripple counter concept is proposed to significantly reduce controller resource utilization for the SR control of high-frequency LLC converters. The whole control system is demonstrated on a 500kHz 1kW 400V/12V LLC converter with a 60MHz MCU, which integrates all the proposed control methods.
Master of Science

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10

Kollipara, Nagasri. "Control and Optimization of Power in LLC Converter Using Phase Control." Wright State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=wright1535402155288153.

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11

Sun, Bingyao. "High-Frequency Oriented Design of Gallium-Nitride (GaN) Based High Power Density Converters." Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/85054.

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The wide-bandgap (WBG) devices, like gallium nitride (GaN) and silicon carbide (SiC) devices have proven to be a driving force of the development of the power conversion technology. Thanks to their distinct advantages over silicon (Si) devices including the faster switching speed and lower switching losses, WBG-based power converter can adopt a higher switching frequency and pursue higher power density and higher efficiency. As a trade-off of the advantages, there also exist the high-frequency-oriented challenges in the adoption of the GaN HEMT under research, including narrow safe gate operating area, increased switching overshoot, increased electromagnetic interference (EMI) in the gate loop and the power stages, the lack of the modules of packages for high current application, high gate oscillation under parallel operation. The dissertation is developed to addressed the all the challenges above to fully explore the potential of the GaN HEMTs. Due to the increased EMI emission in the gate loop, a small isolated capacitor in the gate driver power supply is needed to build a high-impedance barrier in the loop to protect the gate driver from interference. A 2 W dual-output gate driver power supply with ultra-low isolation capacitor for 650 V GaN-based half bridge is presented, featuring a PCB-embedded transformer substrate, achieving 85% efficiency, 1.6 pF isolation capacitor with 72 W/in3 power density. The effectiveness of the EMI reduction using the proposed power supply is demonstrated. The design consideration to build a compact 650 V GaN switching cell is presented then to address the challenges in the PCB layout and the thermal management. With the switching cell, a compact 1 kW 400 Vdc three-phase inverter is built and can operate with 500 kHz switching frequency. With the inverter, the high switching frequency effects on the inverter efficiency, volume, EMI emission and filter design are assessed to demonstrate the tradeoff of the adoption of high switching frequency in the motor drive application. In order to reduce the inverter CM EMI emission above 10 MHz, an active gate driver for 650 V GaN HEMT is proposed to control the dv/dt during turn-on and turn-off independently. With the control strategy, the penalty from the switching loss can be reduced. To build a high current power converter, paralleling devices is a normal approach. The dissertation comes up with the switching cell design using paralleled two and four 650 V GaN HEMTs with minimized and symmetric gate and power loop. The commutation between the paralleled HEMTs is analyzed, based on which the effects from the passive components on the gate oscillation are quantified. With the switching cell using paralleled GaN HEMTs, a 10 kW LLC resonant converter with the integrated litz-wire transformer is designed, achieving 97.9 % efficiency and 131 W/in3 power density. The design consideration to build the novel litz-wire transformer operated at 400 kHz switching frequency is also presented. In all, this work focuses on providing effective solutions or guidelines to adopt the 650 V GaN HEMT in the high frequency, high power density, high efficiency power conversion and demonstrates the advance of the GaN HEMTs in the hard-switched and soft-switched power converters.
Ph. D.

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12

Panov, Vasil. "LLC resonant converter modelling." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/46521.

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Many of today's power converters use pulse-width modulation(PWM) techniques to regulate the circulating currents and voltages. A significant problem with most dc-dc converters is the increased power loss during switching. These devices typically operate in hard-switching mode which results in switching losses. Resonant converters have been used to minimize or even eliminate this problem. Although LLC resonant converters have shown significant gains in terms of efficiency, their modeling is still a challenge. LLC converters are designed to function in a specific mode and region of operation. It has been difficult to design a stable and robust controller with consistent bandwidth and disturbance rejection for every application. The complexity of the control design is magnified when the LLC converters are controlled using embedded digital control techniques. Recent developments in micro-controllers, including processing speed, power, and memory management, make possible the use of innovative non-linear or adaptive control algorithms, in order to produce high performance LLC circuits. Accurate modeling of the hardware is the key to an effective solution. This thesis presents several modeling techniques of the LLC resonant converter. Previous research is discussed and relevant techniques are used as reference for deriving the models presented here. A new approach will be used to describe the characteristics of the LLC within the operating region. This approach is derived using the method of Least Squares of errors. The method estimates the coefficients of the plant transfer function, which then help to calculate control coefficients in the instantaneous operating condition of the LLC resonant power converter.

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13

Chen, Haoning (William). "LLC Resonant Current Doubler Converter." Thesis, University of Canterbury. Electrical and Computer Engineering, 2013. http://hdl.handle.net/10092/8492.

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The telecommunications market is one of the large rapidly growing fields in today’s power supply industry due to the increasing demand for telecom distributed power supply (DPS) systems. The half-bridge LLC (Inductor-Inductor-Capacitor) resonant converter is currently the most attractive topology for the design and implementation of 24V/48V DC telecom power converters. The current doubler rectifier (CDR) converter topology was invented and described in the early 1950s which can offer the unique characteristic of halving the output voltage while doubling the output current compared to a standard rectifier. In this thesis, the current doubler converter topology with its unique characteristic is evaluated as a complementary solution to improve the LLC resonant converter performance, especially for the low output voltage and high output current telecommunication applications. A novel half-bridge LLC resonant current doubler converter (LLC-CDR) is proposed in this thesis which can offer several performance benefits compared to conventional LLC-standard rectifier design . The unique characteristics of the LLC-CDR topology can offer significant improvements by transformation of a 48V converter into a 24V converter with the same power density. This thesis introduces a new SPICE-based simulation model to analyse the operation of this novel LLC-CDR converter circuit design. This model can be used to define the critical component parameters for the LLC -CDR circuit output inductor values. It can also be used to predict the circuit overall performance under different load conditions. Both time-domain based transient simulation analysis and frequency-domain based AC analysis provided by this simulation model showed favourable results in comparison to bench measurement results on a prototype. The model provides a valuable insight to reveal some of the unique characteristics of this LLC -CDR topology. It demonstrates a proof of concept that the conventional LLC resonant converter can be easily redesigned for low voltage, high current applications by using the LLC-CDR topology without requiring a new design for the LLC resonant stage components and the power transformer. A new magnetic integration solution was proposed to significantly improve the overall performance in the LLC-CDR topology that had not been published before. The LLC-CDR converter hardware prototypes with two output inductors coupled and uncoupled configurations were extensively modelled, constructed and bench tested.Test results demonstrated the suitability of an integrated coupled inductors design for the novel LLC-CDR converter application. The integrated coupled inductors design can significantly improve the LLC-CDR converter frequency-domain based AC simulation analysis results. In addition, these results also illustrate the potential benefit of how the magnetic integration design in general could reduce the magnetic component size, cost, and weight compared to the uncoupled inductors design. Finally, a hardware prototype circuit was constructed based on a commercial 1800 W single phase telecom power converter to verify the operation of this novel half bridge LLC-CDR topology. The converter prototype successfully operated at both no load and full load conditions with the nominal output voltage halved from 48VDC to 24VDC, and doubled the output current to match the same output power density. It also demonstrates that the efficiency of this novel half bridge LLC –CDR is 92% compares to 90% of EATON’s commercial 24VDC LLC resonant converter, which can fulfill the research goals.

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Cheng, Brian Cheak Shing. "Modelling and control of the LLC resonant converter." Thesis, University of British Columbia, 2012. http://hdl.handle.net/2429/43729.

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To achieve certain objectives and specifications such as output voltage regulation, any power electronics converter must be coupled with a feedback control system. Therefore, a topic of considerable interest is the design and implementation of control systems for the LLC resonant converter. Additionally, with the current trend of smaller, more cost effective and reliable digital signal processors, the implementation of digital feedback control systems has garnered plenty of interest from academia as well as industry. Therefore, the scope of this thesis is to develop a digital control algorithm for the LLC resonant converter. For output voltage regulation, the LLC resonant converter varies its switching frequency to manipulate the voltage gain observed at the output. Thus, the plant of the control system is represented by the small signal control-to-output transfer function, and is given by P(s) =V_o/f. The difficulty in designing compensators for the LLC resonant converter is the lack of known transfer functions which describe the dynamics of the control-to-output transfer function. Thus, the main contribution of this thesis is a novel derivation of the small signal control-to-output transfer function. The derivation model proposes that the inclusion of the third and fifth harmonic frequencies, in addition to the fundamental frequency, is required to fully capture the dynamics of the LLC resonant converter. Additionally, the effect of higher order sideband frequencies is also considered, and included in the model. In this thesis, a detailed analysis of the control-to-output transfer function is presented, and based on the results, a digital compensator was implemented in MATLAB. The compensator's functionality was then verified in simulation. A comparison of the derivation model and the prototype model (based on bench measurements) showed that the derivation model is a good approximation of the true system dynamics. It was therefore concluded that both the bench measurement model and the derivation model could be used to design a z-domain digital compensator for a digital negative feedback control system. By using the derivation model, the main advantages are reduced computational power and the requirement for a physical prototype model is diminished.

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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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16

Amiri, Peyman. "Synchronous rectification for LLC resonant converter in battery charging application." Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/63050.

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Everyday the number of devices with a battery inside is increasing. From smartphones to electric vehicles, batteries are widely used in different power ratings. Charging time is one of the major obstacles in widespread use of battery powered electric vehicles. Developing high power chargers is one of the key steps to achieve fast charging. Developing high power chargers requires design of compact and high efficiency converters. LLC Resonant converter is widely used in the structure of medium to high power chargers. Utilizing synchronous rectification technique, along with the converter intrinsic soft switching characteristic, has led to above 95% efficiency for LLC resonant converter. Due to presence of magnetizing inductance in the structure of resonant tank in LLC resonant converter, the secondary side currents are not completely synchronous with the primary side gate signals. This makes the control of secondary MOSFETs complicated. Although synchronous rectification for LLC resonant converter has been the focus of research for at least a decade, most of the methods developed for synchronous rectification focus on fixed output voltage applications. However, in battery charging process, the output voltage of the converter varies in a wide range. As a result, new flexible synchronous rectification methods are needed to work in different operating points during the charging process. In this research, the requirements for LLC resonant converter in battery charging application are investigated. Based on these requirements, an LLC converter with 24V rated output voltage and maximum 650W output power is designed. Next, the control requirements for LLC resonant converter in battery charging application are explained. Additionally, the settings for an analog integrated circuit from Infineon Technologies are modified to meet the requirement for battery charging application. At the end, experimental results are presented to show the effectiveness of the control settings in different operating conditions.
Applied Science, Faculty of
Engineering, School of (Okanagan)
Graduate

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Petrásek, Radek. "LLC rezonanční měnič středního výkonu." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2008. http://www.nusl.cz/ntk/nusl-217672.

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The aim of this diploma thesis is to study the resonant converters operation. This paper is concretely specialized to design and implementation the LLC resonant converter with output power about 350 watts. LLC resonant converter is prospective solution for similar applications. The general advantages are that the power MOSFETs are working on zero voltage switching condition, which reduce the switching loss and improve EMI performance. The detailed design for the LLC resonant tank characteristics presented in this paper, which fully guarantees the ZVS condition. This study is based on replacing the rectifier and load by an equivalent resistance applies the first harmonics approximation and the assumption that the current trough the diodes of the output rectifier has a sinusoidal waveform.

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18

Liu, Ya. "High Efficiency Optimization of LLC Resonant Converter for Wide Load Range." Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/30990.

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As information technology advances, so does the demand for power management of telecom and computing equipment. High efficiency and high power density are still the key technology drivers for power management for these applications. In order to save energy, in 2005, the U.S. Environmental Protection Agency (EPA) announced the first draft of its proposed revision to its ENERGY STAR specification for computers. The draft specification separately addresses efficiency requirements for laptop, desktop, workstation and server computers. The draft specification also proposes a minimum power supply efficiency of 80% for PCs and 75% to 83% for desktop derived servers, depending on loading condition and server type. Furthermore, recently some industry companies came out with a much higher efficiency target for the whole AC/DC front-end converter over a wide load range. Distributed power systems are widely adopted in the telecom and computing applications for the reason of high performance and high reliability. As one of the key building blocks in distributed power systems, DC/DC converters in the front-end converter are also under the pressure of increasing efficiency and power density. Due to the hold-up time requirement, PWM DC/DC converters cannot achieve high efficiency for well known reasons when they are designed for wide input voltage range. As a promising topology for this application, LLC resonant converters can achieve both high efficiency and wide input voltage range capability because of its voltage gain characteristics and small switching loss. However, the efficiency of LLC resonant converter with diode rectifier still cannot meet the recent efficiency target from industry. In order to further improve efficiency of LLC resonant converters, synchronous rectification must be used. The complete solution of synchronous rectification of LLC resonant converters is discussed in this thesis. The driving of the synchronous rectifier can be realized by sensing the voltage Vds of the SR. The turn-on of the SR can be triggered by the body-diode conduction of the SR. With the Vds compensation network, the precise voltage drop on Rds_on can be achieved, thus the SR can be turned off at the right time. Moreover, efficiency optimization at normal operation over wide load range is discussed. It is revealed that power loss at normal operation is solely determined by the magnetizing inductance while the magnetizing inductor is designed according to dead-time td selection. The mathematic equations for the relationship between power loss and dead-time are developed. For the first time, the relationship between power loss and dead-time is used as a tool for efficiency optimization. With this tool, the efficiency optimization of the LLC resonant converter can be made according to efficiency requirement over a wide load range. With the expectation to achieve high efficiency at ultra-light load, the green mode operation of LLC resonant converters is addressed. The rationale of the issue with the conventional control algorithm is revealed and a preliminary solution is proposed.
Master of Science

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19

Ang, Yong-Ann. "Modelling, analysis and design of LCLC resonant power converters." Thesis, University of Sheffield, 2006. http://etheses.whiterose.ac.uk/15027/.

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The thesis investigates the modelling, analysis, design and control of 4th -order LCLC resonant power converters. Both voltage-output and current-output variants, are considered. Key research outcomes are the derivation of new frequency- and time-domain models of the converters, based on normalised component ratios, and including the effects that parasitic elements have on circuit behaviour, and a detailed account of multi-resonant characteristics; extensions to the use of cyclicmode modelling methods for application to LCLC converters, to provide rapid steady-state analysis, thereby facilitating the use of the derived methodologies as part of an interactive design tool; the formulation of analytical methods to predict the electrical stresses on tank components-an important consideration when designing resonant converters, as they are often higher than for hard-switched converter counterparts; the characterisation of both continuous and discontinuous modes of operation and the boundary conditions that separate them; and a substantial treatment of the modelling, analysis and design of LCLC converters that can provide multiple regulated outputs by the integrated control of both excitation frequency and pulse-width-modulation. The proposed methodologies are employed, for validation purposes, in the realisation of two proof-of concept demonstrator converters. The first, to satisfy the requirements for delivering 65V (rms) to an electrode-less, SW, fluorescent lamp, to improve energy efficiency and lifetime, and operating at a nominal frequency of 2.65 MHz, is used to demonstrate capacitively-coupled operation through the lamp tube, thereby mitigating the normally detrimental effects of excitation via the electrodes. The second prototype considers the realization of an LCLC resonant power supply that can provide multiple regulated outputs without the need for post-regulation circuitry. The two outputs of the supply are independently, closed-loop regulated, to provide asymmetrical output voltage distributions, using a combination of frequency- and duty-control. Although, an analysis of the supply shows that the behaviour is extremely complex, due, in particular, to the highly non-linear interaction between the mUltiple outputs and parasitic inductances, and rectifier, an analysis to provide optimum performance characteristics, is proposed. Moreover, a PICIFPGA-based digital controller is developed that allows control of the transient performance of both outputs under start-up and steady-state conditions.

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Gilbert, Adam John. "Analysis, design and control of LCC resonant power converters." Thesis, University of Sheffield, 2007. http://etheses.whiterose.ac.uk/15028/.

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Through the judicious and efficient use of energy in both domestic and commercial products, the rate at which the world's fossil fuels and mineral resources are depleted, can be minimised, thereby securing energy reserves for the future. This thesis considers a number energy saving roles the power systems engineer can contribute, with specific emphasis on the impact of improving DC-DC power converters for providing significant energy savings. It is shown that by increasing the efficiency of such converters, through the greater use of switched-mode supplies, huge reductions in the production of green house gases can be obtained. Moreover, resonant converters, a specific subset of switched-mode supply, are identified as a candidate technology for future widespread use. Since the behavioural dynamics of resonant converters are inherently non-linear, the analysis and design of such systems is extremely complex when compared to other families of converter, and has been a critical factor in impeding their widespread adoption. This thesis therefore aims to provide new tools to aid the designer in overcoming such reservations. Novel analysis and design procedures are developed in Chapters 3 and 4, for the series-parallel inductively-smoothed and capacitively smoothed resonant converters, respectively, which, unlike previously reported techniques, allows a designer with little knowledge of resonant converter systems to readily select preferred components for the resonant tank based on design specifications. Specifically, the analysis in Chapter 3 develops a new methodology that extends 'Fundamental Mode Analysis' (FMA) techniques, and provides a first-order estimate of component values to meet a given specification. Chapter 4 then considers the steady state behaviour of the converter, from a state-plane perspective, and provides exact component values and electrical stress analyses based on ideal converter characteristics. The presented methodology normalises the converter behaviour, such that the gain of the resonant tank (at the resonant frequency and minimum load resistance), and the ratio between the two tank capacitances, fully characterises the behaviour of the converter as the load is varied and the output voltage regulated. To further aid the designer, various new design curves are presented that makes the use of traditional, and complicated, iterative calculation procedures, redundant. Chapter 5 further develops a high speed 1 transient analysis technique for resonant converters that is shown to provide a IOOx reduction in simulation times compared to integration-based methods, by considering only signal envelopes. The technique is shown to significantly aid in the design of variable frequency controllers. Chapters 6 and 7 further consider the control of resonant converters. Specifically, Chapter 6 derives a novel self-oscillating control methodology, which, unlike previously published techniques, approximately linearises the large-signal dynamics of the converter, and thereby readily enables the robust design of an outer loop controller for output-voltage/-current regulation purposes. Additionally, in contrast to other methods for the robust control of resonant converters, little knowledge of the converter state-variables is required, thereby minimising the number of high-bandwidth sensors necessary. The technique simply requires the real-time polarity of current-flow through the series-inductor, and output-voltage/-current, to be known. Through additional (optional) measurement of supply-voltage and a feed-forward control component, the effects of supply-voltage disturbance are shown to be greatly attenuated, thereby requiring reduced outer-loop control action and improving overall regulation performance. Finally, Chapter 7 considers the control of resonant converters when the cost of isolated feedback sensors is prohibitive. Unlike traditional techniques, where the output-voltage is estimated under fixed load conditions, through use of an Extended Kalman Filter observer scheme, non-isolated measurements are used to estimate both the output-voltage and the load-resistance. The load resistance estimation is then used to aid in fault-detection and for improving transient dynamic behaviour via the provision of feed-forward action, resulting in safer converter operation and enhanced regulation performance, and, ultimately, reduced cost.

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21

Hsu, Chi-Lun, and 許繼倫. "Efficiency Analysis of LLC Resonant Converters." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/50065916316761517229.

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碩士
國立彰化師範大學
電機工程學系
104
Abstract This thesis proposes a study of efficiency analysis for LLC resonant converters. Since LLC resonant converters possess characteristics of soft-switching, high efficiency and low electromagnetic interference, are suitable to be used for power conversions. In general, efficiency is an important parameter to impact the performances of LLC resonant converters. However, only a few researches were presented for the efficiency analysis of LLC resonant converters in detail. Therefore, the efficiency of LLC resonant converters is necessary to study due to it is usually determined from the previous experience of the researchers. In this thesis, the equivalent circuit model of LLC resonant converters with non-ideal parts of the components is adopted to derive the effect upon the efficiency, and then the efficiency resulted from non-ideal components of LLC resonant converters can be discussed by this derivative result. Finally, a prototype with 380 V input and 24 V/240 W output, is implemented to estimate the feasibility of the proposed efficiency analysis for LLC resonant converters.

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Yen-ChihWang and 王彥智. "Small-Signal Analysis of LLC Resonant Converters." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/05907993223223430340.

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碩士
國立成功大學
電機工程學系專班
99
This thesis presents the small-signal analysis of the full-bridge LLC resonant converter with the variable-frequency control. In order to determine the frequency characteristics of the full-bridge LLC resonant converter, the control-to-output transfer function and corresponding poles and zeros need to be derived. Therefore, a novel small-signal analysis using the concept of frequency modulation (FM) and frequency demodulation (FDM) is proposed. The variable-frequency control scheme can be treated as a frequency modulator because the small-signal perturbation causes frequency variation. Then, the FM signal can be demodulated by the LLC resonant tank and the full-wave rectifier to the load. Therefore, the control-to-output transfer function can be derived. With the further simplification of the derived transfer function, the poles and zeros can be obtained to predict the frequency characteristics. Based on the derived transfer function, the Bode diagrams can be plotted by Mathcad? to compare with the SIMPLIS? simulation results. Finally, a prototype circuit of the 576W full-bridge LLC resonant converter is built to validate the derived transfer function through the gain/phase measurement station which is constructed by using the gain/phase analyzer, PSM1735.

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Huang, Shiang-Kai, and 黃詳凱. "Interleaved LLC Resonant Converters with Digital Control." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/75825081309366798931.

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碩士
國立臺灣科技大學
電機工程系
102
The LLC resonant converter has several characteristics and it has been widely used in DC/DC power application. However, it has large current ripple on secondary side due to lacking output inductor. Several aluminum electrolytic capacitors have to be used in parallel to meet the ripple current specification and reduce output voltage ripple. Consequently, the power density of the converter is decreased. The interleaved LLC converter is suitable for the high output current application since interleaved configuration has several features such as less stress on components and less current ripple. However, the interleaved LLC converter performs worse in terms of the system efficiency when it operates in low load. In addition, it also has a current balance issue due to tolerance of components. In this research, an analysis of above phenomenon and solutions are provided. A digital signal controller is used to generate the interleaved control signal and achieve the control algorithms for the above mentioned problems. By employing the proposed techniques, the digital-control interleaved LLC converter with optimal control strategy is achieved. The low load efficiency is improved and the unbalance issue also be solved.

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Wang, Wei-Kai, and 王威愷. "LLC Resonant Converters with Current Ripple Reduction." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/69548973928814800057.

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碩士
國立臺灣科技大學
電機工程系
101
Two LLC converters LLC with Taiwan Tech center-tapped rectifier (LLC-TCT) and current ripple reduction LLC-TCT are proposed in the thesis. In addition to having zero-voltage switching operation on the MOSFETs and zero-current switching on the rectifier diodes inherited from their predecessors, both converters have several additional features. For instance, the rectifier diodes are clamped to the output voltage due to the absence of filter inductor, the utilization of the clamping series-diode technique, and the recovery of the transformer secondary leakage energy. Moreover, the load current is shared by the output filter capacitor and the L-C-L filter cell constructed by the leakage inductance of the secondary windings and one clamping capacitor. As a result, the required high-voltage output filter capacitor can be reduced. To reduce input current ripple, moreover, an input current ripple reduction LLC-TCT converter (RR-LLC-TCT) is proposed. It features low di/dt on the input current waveform. As a result, the required high-voltage input filter capacitor can be reduced. These characteristics make it desirable for high frequency, high efficiency and high input-voltage and output-voltage power conversion applications such as solar power conversion or larger size LCD TV back light driver. In addition to the descriptions of the operation principle, theoretical analysis, and design considerations, three high frequency converters, LLC-CT, LLC-TCT, and RR-LLC-TCT, with 300-400-V input and 200-V/400-W output specification are built and tested to demonstrate their feasibility.

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Costa, Válter de Sousa. "LLC resonant charger with variable inductor control." Master's thesis, 2016. http://hdl.handle.net/10400.26/18421.

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The present work pretends to study the operation and behavior of the LLC resonant converter topology considering a battery charging application, using the traditional switching frequency control and a new control variable, the variable inductance, provided by a current controlled device, the Variable Inductor (VI). During this work, a brief state of the art regarding general types of power converters and resonant power converters is presented. The LLC resonant converter topology and its advantages and disadvantages are described. The VI principle of operation and structure is presented and discussed and, in the end some information about batteries and its behavior under charging and discharging conditions is presented. The considered batteries characteristics for the studied battery charger are shown and the adopted charging profile is presented. In the following chapters, a theoretical analysis of the LLC resonant converter operation and behavior under switching frequency or VI control is performed and presented. A design methodology is proposed for the converter considering both switching frequency and VI control, separately or simultaneously. Simulations of the converter operation under open-loop condition were made, and simulation results were obtained and discussed. A prototype was built and test results were obtained. The prototype uses a SiC MOSFET (Silicon Carbide Metal Oxide-Semiconductor Field Effect Transistor) based inverter working at 100 kHz controlled with fiber optic drivers. To build the prototype, Printed Circuit Boards (PCB) were designed, manufactured and built. An high-frequency transformer and a VI were also design and built. Finally, theoretical, simulation and experimental results are confronted in order to reach conclusions regarding to the proposed design methodology and the prototype operation. This final analysis allows validating the LLC-VI resonant converter as a good option for a battery charger.

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Wang, Chao-Chun, and 王超駿. "Optimization Design of LLC Half-Bridge series-Resonant Converters." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/14838067190596831519.

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碩士
中原大學
電機工程研究所
96
This thesis primarily aims to achieve the most highly optimal design for LLC-SRC in terms of safety, stability and reliability. The main circuitry used is LLC-SRC as it is able to achieve high efficiency, low level of EMI emissions, and high power density. Investigation of LLC-SRC design was conducted by using the L6599 PWM IC of STMicroelectronics. The optimization design of LLC-SRC was achieved to implement a 90W PSU. It is able to achieve high efficiency and meet EPA regulation. The electrical functions compares with experimental results and a laboratory prototype are measured in detail. The electrical functions are satisfactory.

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Liang, Cherng-huei, and 梁成輝. "Design and Implementation of Interleaved LLC Half-bridge Resonant Converters." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/47910954625498361254.

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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 LLC half-bridge resonant converters are designed and implemented. In order to increase output power, two LLC resonant converters are parallel-connected. Two gate driver signals of switches are interleaved by 90 degrees to reduce output-current ripple. Besides, switch losses on power devices can be reduced by zero voltage switching(ZVS) and output diode with zero current switching(ZCS). The characteristics of the proposed topology are discussed, and the operation principles and design process are also addressed in this thesis. Finally, interleaved LLC half-bridge resonant converters with input 380~420 V and output 24 V/20 A is implemented to verify the theoretival feasibility.

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Wu, Bing-Yue, and 吳秉岳. "Simulation and Analysis of Interleaved LLC Resonant Converters with Parameter Errors." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/q2v46p.

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碩士
健行科技大學
電機工程系碩士班
106
This paper investigates the influence of module current imbalance due to parameter errors in an interleaved LLC resonant power converter. First the current imbalance theory is explained. Next the operation of an interleaved LLC resonant power converter is analyzed and simulated. Finally, the impact to the power converter performance by current imbalance is examined. The parameter errors including transformer turns ratio n, resonant inductance Lr, resonant capacitance Cr, and magnetized inductance Lm, are considered. Results obtained from this research can be applied to help enhance yield rate in production lines, for example, by setting up the optimal standard for incoming material examination.

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Lin, Song-Po, and 林松柏. "Comparison and Analysis of Voltage Feedback Control in LLC Series Resonant Converters." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/jt8rm8.

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碩士
健行科技大學
電機工程系碩士班
106
The LLC resonant power converter has been found increasing applications in the field of power supplies. It features high efficiency, low EMI, zero voltage switching and zero current switching. The switching losses are much less than that of the PWM converters. Besides, the resonant inductor can be designed to integrate into the transformer. To cope with the demands of smaller size and reduced cost for commercial products, this paper proposes a new PSR (Primary Side Regualtion) method to replace the SSR(Secondary Side Regulation) for LLC resonant converter output voltage control. In this method, an auxiliary coil at the primary side is utilized to induce a voltage signal, which is then processed to be used for output voltage regulating purpose. The proposed method is verified through a prototype LLC resonant converter with input voltage 110~240V and output 48V/100W. The result was compared with that of the traditional method.

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30

Lin, Meng-Fan, and 林孟帆. "Optimization Design of Planar Transformer for High Frequency LLC Series Resonant Converters." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/u9m6cr.

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碩士
國立臺灣科技大學
電子工程系
106
Magnetic components are the main source of power losses in high step-down LLC resonant converters. Therefore, to achieve high efficiency and high power density, improving the magnetic element is an important issue. Ferrite cores with high permeability and low core loss are widely used in high-frequency switching power supplies. The core loss mainly results from hysteresis loss and eddy current loss. Therefore, this thesis aims to analyze and optimize the structure of ferrite cores using Maxwell software to implement the Finite Element Method (FEM). Changing the distribution of magnetic flux density to reduce core loss results in a tradeoff design between the volume and loss of magnetic core. Then, the transformer can be optimized to achieve high circuit efficiency. Finally, a 750-W LLC resonant converter prototype with specifications of 380-V input voltage, 12-V output voltage, and 500-kHz switching frequency is implemented and tested to verify the feasibility of different architectures on transformer cores.

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Lyu, Zong-Han, and 呂宗翰. "A Light-Load Efficiency Improvement Technique for Full-Bridge LLC Resonant Converters." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/5jm447.

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碩士
國立臺灣科技大學
電機工程系
106
Comparing with conventional resonant converters, the LLC resonant converter boasts benefits including regulates the output voltage with a relatively small variation of switching frequency, achieves zero voltage switching (ZVS) over wide operating range and utilizes all essential parasitic elements for achieving ZVS. In this thesis, a hybrid control strategy of full bridge LLC resonant converter is proposed. Using this control strategy, full bridge LLC resonant converter operates in variable frequency modulation under normal to heavy load and in phase shift modulation under light load. All the switches can realize ZVS from nearly zero to full load without any auxiliary circuit. The detailed operation principles and design considerations are analyzed first, and the implementation of the proposed hybrid control strategy is presented and discussed. To validate the correctness and effectiveness of the proposed method, a 480 W prototyping circuit is built and tested. According to the experimental results, the conversion efficiency can be improved by 6.87 %, 2.21 % and 1.03% when operating under 5 %, 10% and 20 % load comparing with conventional variable frequency modulation.

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32

Liu, Kai-Ping, and 劉開平. "Design and Implementation of LLC Resonant Converters to Improve Standby Power Efficiency." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/44556877509224567744.

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碩士
國立臺灣科技大學
電機工程系
102
This thesis presents a novel solution of improving standby efficiency applied to half-bridge high power LLC resonant converter which can be used in the renewable generation systems of the distributed power systems. The main goal is that solar and wind power can be produced in both high-efficiency and stable output to supply loads in various conditions of loads. In order to achieve the above objectives, this thesis will further study the series and parallel resonant power converters and propose light load control strategies. Series and parallel resonant power converters are mainly composed by the symmetrical half-bridge circuit with a resonant tank and transformers. Using frequency control changed the characteristics of the resonant tank to achieve the purpose of the output voltage modulation. By comparing to the traditional fixed- frequency hard cut power supplies, series and parallel resonant power converters can achieve zero-voltage switching or zero-current switching to reduce switching losses. In practical applications, the power supply is often under light load or no-load conditions. The efficiency of series and parallel resonant power converters is poor in both cases. In this thesis, the proposed control circuit can reduce switching loss and improve the standby efficiency. Except using the output voltage sensor as a feedback signal in this control circuit, there is even a synchronizing detector as a feedback signal which can make the auxiliary control circuit synchronizing with the primary side. Finally, the way to improve the LLC converter efficiency in standby mode is verified with software simulation by SIMetrix/SIMPLIS.

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33

Lin, Guan-Wei, and 林官緯. "Optimization Design of Fraction-Turns Transformer for High Frequency LLC Series Resonant Converters." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/5mx2p7.

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碩士
國立臺灣科技大學
電子工程系
106
For the high step-down LLC resonant converters with low voltage and high power output, main sources of power losses are copperloss of secondary side and coreloss, also the volume of magnetic component decided total capacity of circuits. Therefore, to achieve high efficiency and high power density, improving the magnetic element is an important issue. The fraction-turns transformer structure can reduce copper length of secondary side, through which can reduce the copper loss of transformer. Therefore, this thesis aims to analyze the availability of fraction-turns transformer structure design based-on LLC resonant converter using Maxwell software. Finally, a 1MHz, 380/12V, 1000W LLC resonant converter using gallium nitride (GaN) devices with a peak efficiency of 97% is achieved.

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34

Huang, Zhèng-èr, and 黃正二. "Current Balancing Control of Interleaved LLC Resonant Converters by Pulse-Width Modulation Method." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/60192251864568185150.

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碩士
健行科技大學
電機工程系碩士班
103
This thesis proposes to use pulse-width modulation (PWM), instead of frequency modulation (FM), to regulate the output voltage and balance the module currents of an interleaved LLC resonant converter. The imbalance of module currents in power converters with modules connected in parallel is usually a problem caused by parameter errors of component, which is unavoidable and unsolvable by the regular FM method. The thesis combines the Fundamental component approximation method and the Fourier series analysis technique to explain the principle that a half bridge resonant converter can be controlled by the PWM method. Analysis and design of LLC resonant converter based on PWM control are performed. In addition, the control system is designed to include two PWM control loops. While the inner loop is to balancing the module currents by using the master-slave control logic, the outer loop is to regulating the output voltage of the converter. A 300W/380Vin/19Vout interleaved LLC resonant converter with two modules connected in parallel had been realized in this thesis to verify the proposed method, in which the DSP TMS320F28035 was used as the control platform. As a result, the experimental measure showed that all the half bridge switches can be turned on with zero voltage, the current balancing effect can be improved at least 75%, and the maximum converter efficiency obtained is 94%.

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35

Wang, Chao-Chun, and 王超駿. "Optimization Design of Synchronous Rectification for High-efficiency LLC Half-bridge Resonant Converters." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/25272233767132704030.

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博士
國立臺灣科技大學
電子工程系
103
This dissertation mainly aims to study the optimal design for half-bridge LLC resonant converter with synchronous rectifier. In order to further improve the efficiency and reliability, zero-voltage switching, compensated sensing of synchronous rectifier technologies and integrated drivers are adopted. Operating principles and design considerations are analyzed and discussed in detail. The experimental results of a 12V/ 200W laboratory prototype are shown to verify the feasibility of the proposed scheme. The highest efficiency is achieved to 97.6% at 100% load. The average efficiency is achieved to 95.7% at 10% to 100% load conditions.

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36

Chen, Shih-Yuan, and 陳世源. "The Control of Synchronous Rectification Scheme and the Tracking of Resonant Frequency Technique in Digital LLC Resonant Converters." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/53s6b9.

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碩士
國立臺北科技大學
電機工程研究所
103
This thesis focuses on digital and implementation of digital LLC resonant server power supply. We use the control method built in the digital signal processor to let Synchronous Rectification switches reach near zero current switching, and propose a new resonant frequency tracking technique which makes light-to-heavy load switching frequency operate in resonant frequency so that the server power will enhance the overall efficiency. First, with near-synchronous characteristic of LLC primary and secondary-side switches Vds, we used digital signal processor to synchronize primary-side and secondary-side switches Vds to achieve near-zero-current switching for synchronous rectification switches in between light-to-full loads. In the front-end of the server power supply, the voltage level of the power factor correction (PFC) and LLC switching frequency fs have a closely related electrical property. Inspired by this, we adopted digital signal processor to sense if LLC switching frequency fs equals to resonant frequency fr. Then, we use the digital signal processor to modulate the voltage level of voltage calibrator, which will subsequently influence the LLC switching frequency. As a result, the converter achieves the resonant frequency tracking function during light-to-full loads. Finally, we made use of 400W LLC resonant server power supply by 3Y Power Technology Inc. to compare differences between analog and digital control efficiency. By replacing the analog control with the digital control method, the results show an improved overall efficiency of 1~2% as well as redundant power supply with 80 plus platinum specification.

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37

Chen, Shih-Shian, and 陳仕賢. "Using Variable Resonant Inductor to Realize Conversion Efficiency Improvement and Abnormal Input Voltage Operation for Half-bridge LLC Series Resonant Converters." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/ayhvmq.

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碩士
國立中山大學
電機工程學系研究所
107
Under the fixed transformer magnetizing inductance, the conversion efficiency of an LLC series resonant converter will be affected by the inductances of resonant inductor in the resonant tank corresponding to different resonant frequencies, resonant inductor ratios, and frequency response gains. Therefore, it will be helpful to improve the conversion efficiency of an LLC series resonant converter if a variable resonant inductor can be designed and the relationship corresponding to the switching frequency, resonant inductor and conduction loss can be analyzed. Besides, the LLC series resonant converter also need to increase the tolerance of abnormal input voltage quality. Most researches in the past focused on the hold-up time for the lower input voltages, but the strategies for the over voltages need more investigation. How to achieve both the conversion efficiency improvement and the abnormal input voltage operation for LLC series resonant converters are worthy of study. Therefore, a novel half-bridge LLC series resonant converter with variable resonant inductor is proposed in this thesis to achieve full load conversion efficiency improvement and abnormal input voltage operation. The resonant inductor of a conventional LLC series resonant converter is divided into two inductors, one of which is connected to a transformer and a full-bridge circuit with four secondary switches. The variable inductance is achieved by controlling the duty cycle of the secondary switches to limit the time and voltage across the inductor in participating resonance operation. Through the proposed novel architecture, the equivalent inductance of resonant inductor can be controlled and selected under different loads to realize the better whole-load conversion efficiency for the proposed converter. In addition, under the abnormal input voltages the converter can also be operated at rated voltage by controlling the duty ratios of secondary switches. A half-bridge LLC series resonant converter with an input DC voltage of 380V, an output DC voltage of 12V, and a rated output power of 600W is designed and implemented in this thesis. The trends of calculated and measured efficiencies are compared. Experimental results show that by selecting different resonant inductances through the duty cycle of secondary switches, a maximum conversion efficiency improvement of 3.28% at light loads and higher whole-load conversion efficiency compared to a conventional LLC converter can be obtained by the proposed converter. Furthermore, the proposed converter can maintain the rated output voltage when input voltages are 240V and 400V.

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38

Yung-Chyang-Wang and 王永強. "LLC Resonant Half Bridge Converter." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/65223932741609639976.

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39

Chen, Song-Cian, and 陳頌謙. "Near Constant-Frequency LLC Resonant Converter." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/80169305727621846036.

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碩士
建國科技大學
電機工程系暨研究所
99
This study proposed a new LLC resonant converter with near constant-frequency. With the characteristic of soft switching, LLC resonant converters presents the advantages of high conversion efficiency and low electromagnetic interference (EMI) that they are suitable for high-frequency power converters. Nonetheless, LLC resonant converters are operated with variable-frequency control that the designs of EMI filters become more complicated and difficult. Besides, when working in light load, the efficiency conversion is lower and the output voltage ripples are larger. In this case, the LLC resonant converter, which could work in Near Constant-Frequency, is proposed in this study. To achieve the function of Near Constant-Frequency, a frequency-converted Resonant Tank is designed to change the resonant frequency with the change of load. Furthermore, the LLC resonant converter with Near Constant-Frequency remains the characteristic of high efficiency conversion and largely improves the conversion efficiency with light load. The LLC resonant converter with near constant-frequency control is first analyzed; then, chaotic ganetic algorithm is utilized to design the key circuit element parameters of the converter; and finally, the near constant-frequency LLC resonant converter is completed. The experimental results show that the efficiency of the ultra-light load 6W is 78.2%, the efficiency of 18W reaches 89.3%, the maximum efficiency of the circuit presents 94.5%, and the change of the operation frequency 24W~240W appears 1.1kHz.

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40

Chun-HsuYang and 楊淳旭. "IC Design for LLC Resonant Converter." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/41940660259405825488.

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碩士
國立成功大學
電機工程學系碩博士班
101
In this thesis, a controller for a half-bridge LLC resonant DC-DC converter with light-load efficiency improvement is realized. The high switching frequency and circulating current in the resonant tank result the poor efficiency of a LLC resonant converter under light load condition. The light-load efficiency improvement is limited with the conventional burst-mode control. To improve efficiency further, a modified burst-mode control is implemented in the proposed controller. The switching frequency decreases gradually during burst-on time to reduce the number of switching cycles under the same output ripple. Moreover, in burst-on time, the first pulse drives the MOSFET at high side with limited pulse width to suppress the initial current in resonant tank. The last switching cycle in burst-on time must be complete to ensure that initial conditions of each burst cycle are the same. Consequently, the switching losses are reduced by proposed control strategy, and light-load efficiency is improved. This chip is fabricated with TSMC 0.25um CMOS high voltage mixed signal general purpose process.

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41

HUANG, NIAN-ZHONG, and 黃念中. "Research of LLC Resonant DC Converter." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/n59wwt.

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碩士
中華科技大學
機電光工程研究所碩士班
106
This thesis mainly discusses the LLC resonant power converter. We uses the characteristics of the resonant converter's soft switching and analyzes the operation principle of the LLC resonant converter. The advantages of the LLC resonant converter are as follows: The switch has Zero voltage switching, secondary side rectification with zero current. The LLC resonant converter has the advantage of a fixed duty cycle. It uses primary transformer primary leakage inductance, magnetizing inductance, parasitic elements of the MOSFET, and resonant capacitors to generate resonance to reduce switching losses and improve efficiency. The half-bridge switching, LLC resonance, and step-down rectification have been simulated by the PSIM software. The waveforms of the transient and steady-state response of the DC-DC converter system have been presented. The zero-voltage switching, frequency of the LLC resonant converter and secondary side rectification with zero current are presented in this thesis. From the results of simulation to verify their effectiveness.

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42

Chen, Peng-Ruei, and 陳芃瑞. "Implementation of the LLC Resonant Converter." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/02429844998477385969.

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碩士
崑山科技大學
電機工程研究所
104
This thesis presents an isolated half-bridge converter for high efficiency battery charger. The power stage uses a resonant LLC topology since it improves efficiency, reduces EMI signature and provides better transformer utilization compared to conventional topologies. In the resonant tank, only one magnetic component is needed, the leakage inductance of transformer is used as resonant inductance. With proper selection of the resonant tank and modulation of the operation switching frequency, the power switches of proposed circuit can achieve zero voltage switching (ZVS), and rectifier diodes are turned off at ZCS if the switching frequency is less than the series resonant frequency. Due to the ZVS and ZCS yielded by the LLC converter, the switching loss is reduced and the system efficiency is enhanced. Finally, a prototype of 150V input and 110W output is constructed. The SPICE simulation and experimental results of the ZVS and ZCS, unique frequency modulation efficiency are presented to prove the feasibility of the designed LLC resonant converter.

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43

Chan, Chih-Hao, and 詹智皓. "Implementation and Study of LLC Resonant Converter." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/50964565994434461961.

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碩士
建國科技大學
電機工程系暨研究所
97
This thesis conducts Genetic Algorithm and Taguchi method to determine the component values of the resonant circuit. Since LLC resonant converter possesses soft-switching characteristic and has high transfer efficiency and low electromagnetic interference, it is suitable to be used in switching power supplies. Nevertheless, the high output current ripple requiring a larger capacitor is a major drawback that limits the applications of LLC resonant converter. Even though current-shaping technologies have been proposed for overcoming the above-mentioned defect, but there is still no systematic method for the determination of the resonant circuit parameters effectively. Therefore this study develops a novel method to implement a productive resonant circuit for depressing the output current ripple and the experimental results show that there is 20.4% reduction in full-load operation. This thesis first analyzes the operation principles of the LLC resonant converter and the same converter with current-shaping technogy. Afterward MathCAD and Genetic Algorithm are adopted to analyze and determine the resonant circuit parameters for the lowest output current ripple. Also IsSpice software is used for circuit simulations. Besides, the theoretical values obtained from theoretical analysis are confined to the standard specifications of elements, so that proper element specifications cannot be established and the functioning of prototype circuit is far from ideal. Therefore Taguchi method is conducted to achieve optimal design. Eventually, an LLC resonant converter with current shaping is implemented and thus proves the feasibility of the proposed method.

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44

Yang, Chih-Lung, and 楊志隆. "Analysis and Implementation of LLC Resonant Converter." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/75066414087761942462.

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碩士
雲林科技大學
電機工程系碩士班
96
Analysis and implementation of an LLC resonant converter with multiple outputs are presented in this thesis. The advantages of resonant converter are high efficiency, high switching frequency and high power density. The LLC converter are suitable for TFT-LCD power supply module. The proposed LLC resonant converter can supply 12V and 24V output voltages at the same time. The front stage of proposed converter is a boost converter with high power factor. The flyback converter is also designed to provide the standby power for the full circuit. The experimental results and the measured values are proved in this thesis.

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45

Chen, Ya-chun, and 陳雅君. "Design and Implementation of LLC Resonant Converter." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/39933214325948361006.

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碩士
國立成功大學
電機工程學系碩博士班
97
In this thesis, an LLC resonant converter is designed and implemented. The power losses of power devices and transformer are analyzed at different load conditions. Especially, the performance of LLC resonant converter operated with various burst-mode frequency and high-switching frequency are discussed and compared under light load conditions. Finally, a laboratory prototype LLC resonant converter with input 400V and output 24V/10A is implemented to verify the analysis and discussion.

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46

Chu, Yu-Hsien, and 朱育賢. "High-Efficiency Design of LLC Resonant Converter." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/23657062494546645211.

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碩士
國立臺灣大學
電機工程學研究所
96
The LLC resonant converter has the merit of fixed duty cycle operation. A combination of parasitic components, which includes the MOSFET output capacitance and the leakage inductance of the isolation transformer, produces a resonant action and reduces drain-source voltage prior to turn-on. Moreover, the switching loss is reduced relatively.Therefore, high efficiency operation of system is achieved.An experimental prototype of 115~264Vac input, 19V/4.73A output, the resonant converter full load efficient reaches 95.31%. The subject of this thesis is to analyze and design a LLC resonant converter. The LLC resonant converter allows zero voltage turn-on of switches while retaining the merits of simple circuit designed and low stresses accompanied with variable frequency control. The LLC resonant converter uses parasitic components to resonate. Therefore, additional resonant components are not required. Moreover, the switching stresses are reduced by using of the zero voltage switching (ZVS) resonant technique.

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47

Chen, Jyue-Long, and 陳珏龍. "Design and Implementation of Resonant Capacitor Controlled LLC Resonant Converter." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/uaae3v.

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碩士
國立中央大學
電機工程學系
106
This thesis focuses on the design and implementation of a half-bridge LLC resonant converter with power factor correction. The traditional LLC resonant converter suffer from the problem of poor light-load efficiency. Burst-mode is usually used to solve this problem, but Burst-mode has problems like large output voltage ripple, acoustic noise, poor dynamic response. This thesis proposes a resonant capacitor controlled LLC resonant converter to improve light-load efficiency. In addition, this control method can be used to extend hold-up time. Finally, this thesis implements a 300W AC/DC power supply. The input voltage range is 90 ~ 264V_ac, the output voltage is 50V_dc, and the output current is 6 A at full-load. The overall average power factor is more than 0.94. The average efficiency is 90%, and the highest efficiency is 93%. Finally, the relevant experimental results verify that the designed resonant capacitor controlled half-bridge LLC resonant converter with power factor correction has the effect of improving light load efficiency and extending the hold-up time.

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48

Lin, Jin-Bin, and 林晉賓. "Implementing 300W LLC Resonant Converter Based on DSP." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/16974892168657392082.

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碩士
國立交通大學
機械工程學系
101
In recent years, many electronic products development towards miniaturization, it’s necessary to increase switching frequency, so that the magnetic element in the DC-DC converter becomes smaller. How to reduce the switching loss and keep high efficiency, it will become an important issue. In this thesis investigates the LLC half-bridge resonant circuit with synchronous rectification, when the switch turns on can achieve zero voltage switching or zero current switching, and decreases the switching loss. The system based on TMSF28027 DSP chip, and use digital PID controller. The maximum output power is 300 W, the average output voltage is 12 V, and the output current as high as 25 A. The maximum switching frequency is 160 KHz, and use two different measures to realize synchronous rectification. In current sensing measure, the maximum efficiency can reach about 91%, the average efficiency can reach about 84% under the full load.

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49

Su, Hsuan-Ching, and 蘇玄靖. "Study and Implementation of 350W LLC resonant converter." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/zts6t6.

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碩士
國立雲林科技大學
電機工程系
107
This thesis studies an 80Plus-certified power converter to improve circuit efficiency by using zero voltage switching technology. Among lots of power conversion technologies, LLC resonant converter has many advantages such as low switching loss and high efficiency. The resonant tank is used in the LLC resonant converter. Since the input impedance of resonant tank is operated at inductive load, the input fundament current is lagging to the fundamental voltage. Therefore, power switches can be turned on at zero voltage switching over wide range of input voltage and load current. In addition to clarifying the operating principles and design principle of the LLC architecture, Microsoft Excel is used to plot the frequency response curve in order to understand the effect on the voltage gain under different conditions. Finally, a 350W LLC resonant converter was developed by using the variable frequency control IC UCC25600. The electric specifications of the LLC converter are Vin=300V~400V, Vo=12V, and Io=29A. Finally, experiments are provident to show the circuit performance.

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50

Ping-Sheng, Chen, and 陳平昇. "Interleaved Three-Level Fixed-Frequency LLC Resonant Converter." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/09605790964952761940.

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碩士
健行科技大學
電機工程系碩士班
102
This thesis proposes to utilize the fixed-frequency PWM control strategy to replace the traditional phase-shift modulation for realization of a high-efficiency interleaved three-level LLC resonant converter. Result obtained from this research is suitable for application in areas where high voltage, high power, and high stability DC-DC conversion is required. The proposed converter consists of two modules of three-level LLC resonant converter, in which the switching frequency is kept fixed and phase angle between modules is 90° shifted. Major advantages of such converter design include smaller power required by modules, fixed-frequency optimal operating point, and smaller output ripples. Other merits like switch stress is half the input voltage, switch turns on at zero voltage over full load range, control algorithm is simpler, and electromagnetic interference filters become more effective are also attributes of the converter. The thesis starts with the introduction of the basic theory behind half bridge resonant conversions. Then the principle of PWM operation in resonant converters is addressed and the PWM pattern that is appropriate for resonance applications is discussed. In addition, the design algorithm based on the worst case is applied for control margin reservation. Finally an interleaved LLC resonant converter of 50kHz and 1.2kW, with input voltage 520V and output voltage 48V, is simulated and implemented to verify the theory and analysis, in which the Digital Signal Processor TMS320F28035 is used as a control platform. The result obtained from experiments shows that the resonant converter can be successfully controlled by the fixed-frequency PWM method. The output voltage ripple can be improved by 50%. The maximum converter efficiency measured is 98% and is 94.9% at rated condition.

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