带箝位辅助谐振支路的改进型变换器研究

移相控制零电压全桥变换器利用变压器漏感和开关管的寄身电容可实现开关管的零电压开关,为了抑制整流输出寄生振荡,可以在初级加入一个谐振电感和两个箝位二极管构成辅助谐振支路,本文将辅助谐振支路与变压器交换位置,使辅助支路与超前臂相连,不仅抑制了次级寄生振荡和电压过冲,使整流管和箝位二极管工作在软开关条件下,而且减小了箝位二极管上电流有效值,减小了次级占空比丢失和初级通态损耗。分析了改进后变换器的工作原理,并对改进前后的变换器进行了比较。实验结果验证了电路的正确性。

Improvement of Full-bridge Converter with Clamping Auxiliary Resonant Commutating Branch

A phase-shifted Zero Voltage Switching(ZVS) Pulse Width Modulation(PWM) full-bridge converter can realize ZVS for the power switches utilizing the leakage inductance of the transformer and the intrinsic capacitors of the power switches.In order to restrain the parasitic oscillation and the voltage ringing of the rectifier diodes,auxiliary resonant commutating network including a resonant inductor and two clamping diodes auxiliary branches can be introduced to the primary side.The converter can be improved just by exchanging the position of the auxiliary branch and the transformer such that the auxiliary branch is connected with the leading leg.So,the improved converter not only restrains the parasitic oscillation and the voltage ringing of the rectifier diodes,makes both the secondary side diodes and auxiliary diodes operating at the soft switching state,but also decreases the rms current of the clamping diodes auxiliary branches and reduces secondary duty cycle loss and the primary current in zero state.Furthermore,the operation principle of the improved converter and the comparison with the conventional converter are analyzed in this paper.It is proved by experimental results.