The application areas of conventional push-pull converters are limited because of high voltage stress of switches (twice of input voltage). This paper presents a novel zero-voltage and zero-current-switching (ZCS) PWM push-pull three-level converter in which the voltage stress of switches is input voltage. With phase-shifted modulation strategy, the leading switches can only realize zero-voltage-switching (ZVS), and the lagging switches can realize ZCS when block capacitor and block diodes are added. Using the strategy, the converter overcomes the drawbacks presented by the conventional push-pull converter, such as magnetic aberration, large switch loss, and voltage spike on switches, so it can get higher efficiency, and a wider application area. The operating principle of the new converter is analyzed and verified on a 600 W, 50 kHz experimental prototype. Several zero-voltage and zero-current-switching PWM push-pull three-level converters are proposed.%由于传统推挽直流变换器中开关管的电压应力高(输入电压的两倍),故该变换器的应用范围受到限制.本文提出了一种新型的零电压零电流开关PWM推挽三电平直流变换器,其中开关管的电压应力为输入电压.对该变换器采用移相控制,可以发现超前管只能实现零电压开关;加入阻断电容和阻断二极管可以使滞后管实现零电流开关.在这种控制方式下该变换器克服了传统推挽变换器存在的偏磁现象、开关损耗大、开关管有电压尖峰等缺点,使得其变换效率更高,有更广的应用范围.该变换器的工作原理在一个600 W,50 kHz的实验样机上得以分析和验证.最后,本文还提出了另外几种零电压零电流开关PWM推挽三电平直流变换器.
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