一种改进的ZVZCS全桥PWM变换器

Improved ZVZCS full-bridge PWM converter

针对当前零电压、零电流全桥DC/DC变换器需要在辅助电路中增加有源或有损器件及二次侧整流二极管电压应力增大的问题,提出一种改进的电路拓扑结构并对工作过程进行了分析。电路超前臂零电压工作的实现方法与其他传统电路相同,采用外加辅助电容实现;滞后臂的零电流工作条件由2个二极管和1个电容构成的辅助电路实现。辅助电路中不含有源、有损器件,不会增加电路的额外损耗,相比其他拓扑结构,具有更高效率。由于与变压器二次侧抽头并联的钳位电容数值较大,将变压器副边的电压钳位,所以不会增加二次侧的整流管的电压应力。仿真结果验证了电路分析的正确性和设计的可行性。

Conventional ZVZCS （Zero - Voltage and Zero - Current - Switching） full - bridge PWM （Pulse Width Modulation） DC/DC converter needs additional active or consumable device in its auxiliary circuit and raises the voltage stress of rectifier diode,for which an improved circuit topology is proposed with its working process analyzed. The ZVS（Zero- Voltage- Switching） of the leading- leg switches is realized by adding the auxiliary capacitors as conventional converters,while the ZCS （Zero-Current-Switching） of the lagging-leg switches is realized by adding an auxiliary circuit of two diodes and a capacitor. Because there is neither active nor consumable device in the auxiliary circuit,no additional power consumption is needed,making the proposed converter more efficient. Because of the big clamp capacitor,which is connecting in parallel with the center tape at the secondary side of the transformer,the voltage stress of rectifier diode may not rise. The correctness of circuit analysis and the feasibility of converter design are verified by simulation results.