280 W移相全桥软开关DC/DC变换器设计

为抑制输出整流二极管反向恢复引起的电压振荡,采用原边带箝位二极管的电路拓扑设计DC/DC变换器.通过调节移相角调节输出电压,利用开关管的结电容和外接电容以及原边串联电感作为谐振元件,使开关管能进行零电压开通和关断,与传统的移相变换器相比,在变压器原边增加了2个二极管对输出整流二极管进行箝位,实验表明,该方案在实现开关管零电压开通和关断的同时,能够抑制输出整流二极管两端的电压振荡,减小输出整流二极管的电压应力.     

ZVS移相全桥变换器的优化设计与仿真

针对传统的零电压(ZVS)、零电压零电流(ZVZCS)移相全桥变换器的各种缺陷以及实际参数选取困难的问题,采用一种改进型零电压移相全桥软开关变换器,即在原边钳位两个超快恢复二极管与一隔直电容来降低副边电路的寄生震荡以防止变压器进入磁饱和,为进一步提高变换器的效率,副边采用全波整流。对所设计的电路进行细致的原理分析,给出若干关键值的优化计算过程,并以UC3875作为控制芯片,通过saber仿真验证理论分析的合理性,结果表明电路在实现软开关的同时也抑制了副边整流器件的电压应力,证明了所提优化方案的可靠性。     

储能电感前置软开关移相全桥变流器研究

本文提出了一种适用于低压大电流输出场合的软开关移相全桥变流器。该变流器原边带有储能电感,副边采用同步整流技术,通过合理的设计能够使之工作于断续模式(DCM)。其中原边储能电感可以简单方便地实现超前臂开关管的零电压开通。这种工作模式不但能够实现滞后臂的零电流关断,还能实现副边整流器件的零电流关断,有效地降低其开关损耗、体二极管的反向恢复损耗以及抑制寄生结电容电压震荡尖刺等。又因为副边同步整流管的电压应力受到输出电压箝位,所以可以选用较低耐压的同步整流管降低副边的导通损耗。最后根据理论分析设计研制了一台工作频率100kHz,额定功率300Watts的实验样机验证了它的基本工作原理,而其较高的变换效率也体现了该移相全桥变流器的优点。     

低压大电流大功率软开关全桥变换器拓扑结构分析

分析研究了低压大电流全桥变换器电路拓扑结构。分别介绍了功率变压器初级移相控制零电压(ZVS)PWM和移相控制零电压零电流(ZVZCS)PWM软开关全桥变换器主电路拓扑结构,以及功率变压器次级适宜采用的不同电路拓扑形式,并对其优缺点进行了对比分析。文中简要说明了在变换器输入级加入功率因数校正环节的必要性。     

一种原边带箝位二极管的ZVS移相全桥变换器

移相全桥零电压变换器是中大功率直直变换场合的理想拓扑之一,但在其输出整流二极管反向恢复时,整流桥产生寄生振荡,二极管上存在很高的尖峰电压。这将带来电路损耗,并影响整流桥的使用寿命。本文介绍了一种原边带箝位二极管的电路形式,它能够很好地抑制寄生振荡,消除尖峰电压,分析了其工作原理,制作了一个5.5kW样机,并给出了加二极管前后的对比实验结果。     

SVM控制的复合有源箝位ZVS三相PFC变换器

采用复合有源箝位（CAC）的三相功率因数校正变换器，应用改进的空间矢量控制策略，所有的主开关和辅助开关均为零电压开关，有效的抑制了桥臂开关反并联二极管的反向恢复电流，减少反向恢复损耗。而且，具有开关器件电压应力较低，开关频率固定，输入波形质量好的特点。研制了一台基于DSP控制的10kW实验样机，分析了软开关过程及条件，得到了变换器效率同电路谐振参数之间的关系曲线。测量了软开关变换器的传导干扰频谱，验证了软开关变换器较硬开关变换器有更好的电磁兼容性。     

ZVZCS移相全桥PWM变换器的分析与仿真研究

ZVZCS移相全桥PWM变换器实现了超前桥臂的零电压开关(ZVS)与滞后桥臂的零电流开关(ZCS),其软开关的实现条件比ZVS移相全桥与ZCS移相全桥要好。文章全面分析了这种变换器的工作原理,讨论了实现软开关的条件,设计关键参数并利用SIMetrix软件进行了仿真研究。     

LLC谐振半桥变换器的设计

LLC谐振半桥变换器可以在全电压范围内、全负载条件下使得初级端 MOSFET实现ZVS（零电压开关）,次级整流二极管实现ZCS（零电流开关）,减少了开关损耗,大大提高了效率。而且在输入电压和负载范围变化比较大的情况下,其开关频率变化较小,有利于主参数的设计。这种变换器通常应用在高频功率变换领域。文中首先使用 FHA（基波近似原理）进行 LLC谐振半桥变换器的建模,然后分析了如何对变换器中的电气参数进行选择,最后设计了一个工作在70~150 kHz频率下300 W的 LLC谐振变换器。     

一种新型降压式同步整流开关电源设计

设计了一种同时应用同步整流和ZVT软开关技术的新型开关电源变换电路。在整流部分应用阻抗更小的MOSFET代替传统二极管实现了同步整流。采用软开关技术实现了开关管的导通或关断时,在零电压或零电流条件下完成。同时,利用PSIM软件对所设计的拓扑结构进行了模拟仿真,仿真结果表明,所设计的电路有效提高了变换器的整体效率,并减少了物理器件损耗。     

一种全桥ZVZCS DC/DC变换器的研究

提出了一种全桥零电压零电流(FB-ZVZCS)DC/DC变换器拓扑,副边采用电容和二极管构成了两个辅助电路,它们与谐振电感谐振形成的阻断电压源相串联,实现了滞后臂较大范围的ZCS,同时此种结构抑制了副边整流二极管尖峰电压;针对高输出电压设计,输出采用双全桥串联整流电路以降低整流二极管的高电压应力和解决它们的均压问题。变换器控制简单、没有辅助开关和缓冲电路。文中详细分析了工作原理和参数设计,仿真和样机实验验证了方案的正确性。     

Zero-voltage-switching PWM three-level converter with two clamping diodes

A zero-voltage-switching pulsewidth-modulation three-level (ZVS PWM TL) converter realizes ZVS for the switches with the use of the leakage inductance (or external resonant inductance) and the output capacitors of the switches, however, the rectifier diodes suffer from reverse recovery which results in oscillation and voltage spike. In order to solve this problem, this paper proposes a novel ZVS PWM TL converter, which introduces two clamping diodes to the basic TL converter to eliminate the oscillation and clamp the rectified voltage to the reflected input voltage; in the meanwhile, all the switches keep to realize ZVS. Furthermore, the proposed ZVS PWM TL converter can be simplified by removing the two freewheeling diodes. The operation principle of the novel converter and the simplified converter are analyzed and are verified by a prototype converter. The experimental results are also included in this paper.     

Zero-Voltage-Switching PWM Hybrid Full-Bridge Three-Level Converter With Secondary-Voltage Clamping Scheme

A hybrid full-bridge (H-FB) three-level (TL) converter can realize zero-voltage-switching for switches with the use of resonant inductance (including the leakage inductance of the transformer) and intrinsic capacitors of the switches. As it can operate in three-level and two-level (2L) modes, the secondary rectified voltage is always close to the output voltage over the input-voltage range; thus, the output filter requirement is significantly less. Meanwhile, the voltage stress of the rectifier diodes can also be reduced. Therefore, the H-FB TL converter is very attractive for wide input-voltage-range applications. However, there is a serious voltage oscillation across the rectifier diodes caused by reverse recovery like the Buck-derived converters. In this paper, two clamping diodes are introduced to the H-FB TL converter to eliminate the voltage oscillation across the rectifier diodes. The arrangement of the positions of the resonant inductance and the transformer is discussed. The operation principle of the proposed converter is analyzed in details. A 1.2-kW prototype was built and tested in the laboratory to verify the operation of the proposed converter.     

Zero-voltage-switching PWM three-level converter with current-doubler-rectifier

This paper proposes a zero-voltage-switching (ZVS) pulse-width modulation three-level converter with current-doubler-rectifier, which achieves ZVS for all the switches under wide load range and in a wide line range. The rectifier diodes commutate naturally, therefore no oscillation occurs. The determination of the output filter inductance and the blocking capacitor is discussed in details. The experimental results are presented to verify the operation principle of the proposed converter.     

Analysis and Optimal Design Considerations for an Improved Full Bridge ZVS DC–DC Converter With High Efficiency

This paper proposes an improved full bridge dc–dc converter, which can achieve zero-voltage-switching (ZVS) with wide input voltage range and load range. The operation principle of the converter and the optimal design considerations for high efficiency and ZVS range are analyzed. By adding two clamp diodes and two small coupled inductors at the primary side of the transformer, the voltage ringing across rectifier diodes is reduced. Therefore, Schottky diodes can be employed to reduce conduction loss, and high efficiency is achieved. A 1.2-kW/105-kHz prototype was made with an efficiency higher than 95% at full load to verify the theoretical analysis.     

Utilization of an active-clamp circuit to achieve soft switching inflyback converters

Flyback derived power convertor topologies are attractive because of their relative simplicity when compared with other topologies used in low power applications. Incorporation of active-clamp circuitry into the flyback topology serves to recycle transformer leakage energy while minimizing switch voltage stress. The addition of the active-clamp circuit also provides a mechanism for achieving zero-voltage-switching (ZVS) of both the primary and auxiliary switches. ZVS also limits the turn-off di/dt of the output rectifier, reducing rectifier switching losses, and switching noise due to diode reverse recovery. This paper analyzes the behavior of the ZVS active-clamp flyback operating with unidirectional magnetizing current and presents design equations based on this analysis. Experimental results are then given for a 500 W prototype circuit illustrating the soft-switching characteristics and improved efficiency of the power converter. Results from the application of the active-clamp circuit as a low-loss turn-off snubber for IGBT switches is also presented     

Novel constant frequency PWM DC/DC converter with zero voltageswitching for both primary switches and secondary rectifying diodes

A zero-voltage-switching (ZVS) DC/DC converter operating at constant frequency and having wide linearity is proposed. ZVS operation is achieved not only for the primary switches but also for the secondary rectifier diodes to reduce the switching stresses and losses. The converter overcomes other shortcomings of the conventional resonant DC/DC converters, among which are the high VA ratings of devices and passive components and load-dependent DC characteristics     

Zero-Voltage Switching Two-Transformer Full-Bridge PWM Converter With Lossless Diode-Clamp Rectifier for PDP Sustain Power Module

This paper presents a zero-voltage switching (ZVS) two-transformer full-bridge (TTFB) pulsewidth modulation (PWM) converter with lossless diode-clamp rectifier for a plasma display panel sustaining power module (PSPM). The TTFB converter has series-connected two transformers which act as an output inductor as well as a main transformer. Although the naturally doubled leakage inductor due to the series-connected two transformers contributes to achieve the ZVS of the lagging leg, it creates a serious voltage ringing across the output rectifier diodes. This results in the heavy voltage stresses across the rectifier diodes. Thus the dissipative snubber circuits are required in spite of the severe power dissipation. To overcome these problems, a new lossless diode-clamp rectifier (LDCR) is employed as the output rectifier, which helps the voltage across rectifier diodes to be clamped at one half the output voltage ($V_o/$2) or a full output voltage$(V_o)$. Therefore, no dissipative snubber circuits for the rectifier diodes are needed and a high efficiency as well as a low noise output voltage can be realized. In addition, the clamping capacitors of the LDCR can help considerably to reduce the primary circulating current. The operations, analysis, and design consideration of proposed converter are presented. Also, a 425-W, 385-$V_ dc$input, 170-$V_ dc$output prototype is constructed and experimental results show the validity of the proposed converter.     

Analysis, Design, and Implementation of a Parallel ZVS Converter

A soft-switching converter is presented in this paper to achieve a zero-voltage-switching (ZVS) turn on for all switches. Two half-bridge converters with asymmetric pulsewidth-modulation scheme are connected in parallel to control the output voltage at the desired value and achieve load-current sharing. Based on the output capacitance of power switches and the resonant inductance, including the external inductance and the transformer leakage inductance, the resonance can be achieved at the transition interval of power switches. Therefore, the ZVS turn on of power switches can be realized. The peak voltage of the power switches is limited to input dc voltage. The center-tapped rectifier is adopted at the transformer secondary side to achieve a full-wave rectification. Operation principles, steady-state analysis, and design equations of the proposed converter are discussed in detail. Finally, experimental results based on a 240-W prototype are provided to verify the performance and the feasibility of the proposed converter.     

A Novel High-Power-Density Three-Level LCC Resonant Converter With Constant-Power-Factor-Control for Charging Applications

This paper proposes a variable-frequency zero-voltage-switching (ZVS) three-level LCC resonant converter that is able to utilize the parasitic components of the high turns-ratio transformer. By applying a three-level structure to the primary side, the voltage stress of the primary switches is half of the input voltage. Low-voltage MOSFETs with better performance can be used in this converter, and zero-current-switching (ZCS) is achieved for rectifier diodes. By applying a magnetic integration technique, only one magnetic component is required in this converter. The power factor concept of resonant converters is proposed and analyzed, and a novel constant power-factor control scheme is proposed. Based on this control strategy, the circulating energy of resonant converters is considerably reduced. High efficiency can be obtained for high-voltage high-power charging applications. The operation principle of the converter is analyzed and verified on a 700-kHz, 3.7-kW prototype, with which a power density of 72 ${hbox {W/inch}}^{3}$ is achieved.