RCD钳位反激变换器的回馈能耗分析及设计考虑

Design and Analysis on Feedback Energy Loss of RCD Clamping Flyback Converters

对RCD钳位反激变换器的能量传输过程进行深入分析,指出为避免反馈电压Uf在整个开关管关断期间向RCD钳位电路提供能量而增大能耗,钳位电容电压UC必须大于Uf;推导得出反馈电压产生的回馈能量Wf的解析表达式,并指出Wf随着UC的增加而减小,且RCD钳位电路的总能耗等于Wf与变压器漏感储能Wlk之和。令Wlk与Wf相等,得出钳位电容的临界钳位电压UCK=2.6 Uf,并指出当UC大于UCK时,回馈电压产生的能量将小于Wlk,并以此作为确定钳位电容电压UC的依据,得出RCD钳位电路元件参数的设计方法。给出实例,通过仿真和实验结果,验证了理论分析的正确性和设计方法的可行性。

The energy transfer process of the flyback converter with RCD clamp circuit was analyzed.It was concluded that the clamp voltage（UC） of the clamp capacitor must be higher than the feedback voltage（Uf） to avoid too much energy loss resulted from the feedback voltage providing energy to the RCD clamp circuit during the period of switch turn-off.The expression of the feedback energy（Wf） generated by the feedback voltage（Uf） was deduced.It was indicated that Wf decreases with the increment of UC,moreover,the total energy loss caused by the RCD clamp circuit is equal to the summation of Wf and Wlk,the energy from the leakage inductor.Let Wf？Wlk,the critical clamp voltage of the clamp capacitor,UCK？2.6Uf,can be obtained.On this basis,the design methods for the element parameters of the RCD clamp circuit were proposed.The validity of the theoretical analysis and the feasibility of the proposed design methods were verified with the simulation and experimental results.