反激变换器箝位电路的设计

Design of clamp circuit in flyback converter

反激式变换器原边漏感引起的电压尖峰对功率器件和电路性能影响很大,本文基于抑制漏感尖峰影响的目的,考虑到次级反射电压也为箝位电路提供能量,同时箝位电容电压并非不变量,采用了一种改进的箝位电路的设计方法,推导出的表达式,结合反激变换器应力、效率和传导干扰实验,得出了随着箝位电阻值的增大,变换器的效率会提高、传导干扰会变差的结论。根据反激变换器对效率和EMI的侧重点不同,选取箝位电路参数可以满足反激变换器不同的设计要求。

Voltage spike caused by flyback converter leakage inductance has a great influence on power device and circuit performance.Considering reflected voltage of secondary side could provide power for clamping circuit,contemporarily,clamp capacitor voltage is not invariant,this paper is to suppress the leakage inductance spike effect.Improved clamping circuit design has been applied in this paper,combining with flyback stress and conducted interference test,thus concluded that with the increase of R value,the converter efficiency is increasing and conducted interference deteriorating.According to different focuses on efficiency and EMI,selecting clamping circuit parameter can meet various design for flyback converter.