Novel ZCS PWM full bridge DC-DC converter

To reduce loss caused by turn-off process of insulated gate bipolar transistor (IGBT) and improve switching frequency of power supply, an assisted circuit composed by a resonant inductor, a resonant capacitor, an aided clamping diode and an aided switch tube is proposed. The aided switch tube is turned on transiently before the main switching tubes close. The primary current is reset rapidly through the resonance between resonant inductor and resonant capacitor. Thus zero current switching (ZCS) of main circuit switching tubes can be realized. The experiment results show that with this converter the ZCS of all switching tubes and the soft converting of output rectifiers can be realized under any load. The resonant inductor in the assisted circuit is also helpful for realizing soft conduction of main switching tubes. This topology is concise and soft switching is realized without increasing voltage stress of rectifiers, the efficiency is over 90% and is hopeful to be further improved.