同步整流反激变换器在FCCM模式下环流能量回馈技术研究

Research on energy feedback technology of synchronous rectifier flyback converter in FCCM mode

单端反激同步整流变换器工作于轻载状态时会产生反向环流,造成功率损耗,并且通常用于监测环流的零点检测电路结构复杂、控制难度大.为避免这些问题,本文采用了一种结构简单的新型同步整流电路,无需抑制反向环流,而是通过匹配谐振参数的方式使得同一周期内整流MOS第二次开启,充分回收环流能量.同时,本文对轻载时各工作阶段电压电流表达式与谐振时间做了定量计算,并给出实验波形.验证结果表明,该结构可使环流能量无损回馈,同时实现开关管零电压开关(ZVS),且有效抑制低频阻尼振荡,使轻载时的电路工作效率大幅提升.

When the single-ended flyback synchronous rectifier converter works at light load, the reverse circulating current causes power loss. The zero-point detection circuit has complex structure and is difficult to control, which is usually used to monitor the reverse circulating current. This paper presents a new type of synchronous rectifier circuit with simple structure. Instead of suppressing the reverse circulating current, the rectifier MOS is turned on for the second time in the same cycle by matching the resonance parameters to fully recover the circulating energy. This paper quantitatively calculates the voltage and current expressions and resonance time of each working phase at light load, and gives the experimental waveforms. The verification results show that the structure can make non-destructive feedback of circulating energy, realize zero voltage switching(ZVS) of the switching tube, and effectively suppress low-frequency damped oscillation, which greatly improves the working efficiency of the circuit at light load.