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.     

一种单变压器双LLC谐振型变换器

文中提出了一种单变压器结构双LLC网络谐振型变换器。该拓扑实现了Mosfet零电压导通（ZVS）,整流二极管零电流关断（ZCS）,低整流二极管电压应力以及宽范围调压,变压器两个原边绕组同时工作。这种工作模式能够有效地均分励磁电流,降低变压器的设计要求,减小了变压器的尺寸,同时还能减小原边绕组的有效电流,从而减少变压器的铜损。两个串联LLC谐振网络互差半个开关周期工作。输出侧采用全波整流方式,因此整流二极管电压应力为输出电压。由于副边无需电感,因此,设计中可进一步减小变换器尺寸。最后,通过仿真和实验,验证了理论分析的正确性,变换器满载效率可达95.8%。     

基于触发式电感的零电压零电流DC／DC变换器的优化

本文介绍了零电压零电流开关全桥（ZVZCS）DC＼DC变换器。通过添加辅助电路解决了软开关谐振变换器的开关损耗问题。本文叙述了用触发式电感和LC电路的实际应用来实现零电压和零电流开关全桥变换器。通过数学模型分析了在DC＼DC变换操作中变换器的参数对其的影响，用仿真进行了整流参数和工作点的优化。实现了10kW的DC＼DC变换器实验，并在文章中给出了结果。     

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。     

基于软开关技术的100W DC／DC变换器的设计

文章主要介绍了输出电压5V、输出功率100W的DC／DC变换器的设计方法。该变换器电路结构上采用正激一零电流准谐振软开关电路拓扑结构,并结合了有源钳位技术;内部采用高导热灌封材料灌封工艺。该DC／DC变换器具有功率大、体积小、效率高等特点。     

移相全桥ZVS变换器的分析和设计

移相全桥零电压开关变换器是中大功率直直变换场合的理想拓扑之一,但其次级整流二极管反向恢复时,产生严重的寄生振荡,二极管上存在很高的尖峰电压。而文献1中的变换器通过增加一个谐振电感和两个二极管,不仅可以实现软开关,还可以消除次级整流二极管反向恢复引起的电压振荡。基于此变换器的工作原理,文中设计了一台500W移相控制零电压软开关电源,给出了主电路的设计过程和实验波形。     

带有箝位二极管的ZVS全桥三电平DC/DC变换器的研究

介绍了一种改进型的带有箝位二极管的零电压开关(ZVS)全桥三电平DC/DC变换器,详细分析了电路的工作原理。设计实例和仿真结果验证了理论分析的正确性。     

500kHz—1.3MHz零电压准谐振DC／DC变换器

本文以升压(boost)变换器为例,简单地介绍了零电压准谐振DC/DC变换器的工作原理及设计方法,并给出500kHz—1.3MHz升压和回扫(flyback)零电压准谐振变换器的实验结果。     

一种新颖的ZVZCS双管正激变换器

本文提出了一种新颖的、利用辅助电路实现零电压、零电流开关的双管正激变换器。其中,有源钳位辅助电路用来实现主开关管上的零电压开通,同时使该变换器的占空比拓展到50%以上;变压器副边的辅助电路用来实现主开关管以及副边二极管的零电流关断。因此,该变换器中全部开关管均工作在软开关状态下。与其他软开关双管正激变换器相比,该变换器具有结构简单、所用元器件最少等优点。最后,经过一台250W的样机检验,该变换器效率最高可达95.7%,非常适合IGBT应用的场合。     

一种新型正激零电压零电流转换PWM DC/DC变换器

提出一种新型的零电压零电流转换(ZCZVT)的正激拓扑。拓扑工作频率为300kHz,能实现主开关管的零电压开通(ZVS)和零电流关断(ZCS),同时辅助开关管也能实现零电流关断(ZCS),且变压器的磁通复位不需要辅助绕组。文章进行了拓扑的稳态分析,并且讨论了谐振电路的参数设计。最后,在研制一台48V输入、12V/100W输出样机的基础上,实验验证这种新型正激ZCZVT PWM DC-DC变换器的软开关特性。     

A novel ZVS DC/DC converter for high power applications

This paper presents a novel zero voltage switch (ZVS) pulse-width modulation (PWM) DC/DC converter for high power, high output voltage applications. By using two active switches in the secondary side of a transformer, the proposed converter achieves not only ZVS of the active switches in the entire load ranges but also soft commutation of the output rectifier diodes. The proposed topology has simple structure and control strategy. Simulation results and experimental results of a 2.8 kW 200 kHz DC/DC converter are presented.     

Zero-voltage DC/DC converter with asymmetric pulse-width modulation for DC micro-grid system

This paper presents a zero-voltage switching DC/DC converter for DC micro-grid system applications. The proposed circuit includes three half-bridge circuit cells connected in primary-series and secondary-parallel in order to lessen the voltage rating of power switches and current rating of rectifier diodes. Thus, low voltage stress of power MOSFETs can be adopted for high-voltage input applications with high switching frequency operation. In order to achieve low switching losses and high circuit efficiency, asymmetric pulse-width modulation is used to turn on power switches at zero voltage. Flying capacitors are used between each circuit cell to automatically balance input split voltages. Therefore, the voltage stress of each power switch is limited at V_in/3. Finally, a prototype is constructed and experiments are provided to demonstrate the circuit performance.     

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     

A Three-Phase Current-Fed DC/DC Converter With Active Clamp for Low-DC Renewable Energy Sources

This paper focuses on a new three-phase high power current-fed dc/dc converter with an active clamp. A three-phase dc/dc converter with high efficiency and voltage boosting capability is designed for use in the interface between a low-voltage fuel-cell source and a high-voltage dc bus for inverters. Zero-voltage switching in all active switches is achieved through using a common active clamp branch, and zero current switching in the rectifier diodes is achieved through discontinuous current conduction in the secondary side. Further, the converter is capable of increased power transfer due to its three-phase power configuration, and it reduces the rms current per phase, thus reducing conduction losses. Moreover, a delta-delta connection on the three-phase transformer provides parallel current paths and reduces conduction losses in the transformer windings. An efficiency of above 93% is achieved through both improvements in the switching and through reducing conduction losses. A high voltage ratio is achieved by combining inherent voltage boost characteristics of the current-fed converter and the transformer turns ratio. The proposed converter and three-phase PWM strategy is analyzed, simulated, and implemented in hardware. Experimental results are obtained on a 500-W prototype unit, with all of the design verified and analyzed.      

A zero-voltage and zero-current switching three-level DC/DC converter

This paper presents a novel zero-voltage and zero-current switching (ZVZCS) three-level DC/DC converter. This converter overcomes the drawbacks presented by the conventional zero-voltage switching (ZVS) three-level converter, such as high circulating energy, severe parasitic ringing on the rectifier diodes, and limited ZVS load range for the inner switches. The converter presented in this paper uses a phase-shift control with a flying capacitor in the primary side to achieve ZVS for the outer switches. Additionally, the converter uses an auxiliary circuit to reset the primary current during the freewheeling stage to achieve zero-current switching (ZCS) for the inner switches. The principle of operation and the DC characteristics of the new converter are analyzed and verified on a 6 kW, 100 kHz experimental prototype.     

A novel zero-current-transition full bridge DC/DC converter

This paper proposes a novel zero-current-transition pulse-width modulation full-bridge dc/dc converter. The proposed converter not only achieves zero current switching for the main switches and auxiliary switch in the entire load ranges, but it also realizes soft commutation for the output rectifier diodes. Furthermore, the auxiliary circuit also helps to turn on the main switches softly. Simulation results and experimental results verify the theoretical analysis.     

Analysis,design and implementation of an interleaved three-level PWM DC/DC ZVS converter

This paper presents a new parallel three-level soft switching pulse-width modulation (PWM) converter. The proposed converter has two circuit cells operated by the interleaved PWM modulation. Thus, the ripple currents at input and output sides are reduced. Each circuit cell has two three-level zero voltage switching circuits sharing the same power switches. Therefore, the current and power rating of the secondary side components are reduced. Current double rectifier topology is selected on the secondary side to decrease output ripple current. The main advantages of the proposed converter are soft switching of power switches, low ripple current on the output side and low-voltage rating of power switches for medium-power applications. Finally, the performance of the proposed converter is verified by experiments with 1 kW prototype circuit.     

Soft switching resonant converter with duty-cycle control in DC micro-grid system

Resonant converter has been widely used for the benefits of low switching losses and high circuit efficiency. However, the wide frequency variation is the main drawback of resonant converter. This paper studies a new modular resonant converter with duty-cycle control to overcome this problem and realise the advantages of low switching losses, no reverse recovery current loss, balance input split voltages and constant frequency operation for medium voltage direct currentgrid or system network. Series full-bridge (FB) converters are used in the studied circuit in order to reduce the voltage stresses and power rating on power semiconductors. Flying capacitor is used between two FB converters to balance input split voltages. Two circuit modules are paralleled on the secondary side to lessen the current rating of rectifier diodes and the size of magnetic components. The resonant tank is operated at inductive load circuit to help power switches to be turned on at zero voltage with wide load range. The pulse-width modulation scheme is used to regulate output voltage. Experimental verifications are provided to show the performance of the proposed circuit.     

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.     

Novel ZVS DC-DC converter with low current ripple for light rail transit

This paper develops and studies a three-level zero-voltage turn-on converter for providing auxiliary power system in a DC light rail vehicle. The proposed converter includes a three-level circuit and a half-bridge circuit sharing the same power switches on the high voltage side in order to reduce switch counts and distribute total power into two circuits. The Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs) with a low voltage rating and a turn-on resistance are adopted in the developed converter in order to decrease conduction losses on power switches. On the secondary side, two inductors and four rectifier diodes are employed to reduce output ripple current and transformer secondary winding turns. A duty cycle control based on the phase-shift pulse-width modulation is used to regulate the output voltage and achieve the wide range of zero-voltage turn-on. Experimental results with a prototype with a 760 V input and a 48V/30A output are provided to verify the feasibility and effectiveness of the developed converter.