隔离Boost变换器用反激箝位的研究

隔离Boost变换器具有高频电气隔离、易于多路输出、输入电流纹波小、负戢短路时可靠性高等优点。但是由于变压器漏感存在，开关管关断时升压电感电流无法瞬时流入变压器，从而在开关管两端产生浪涌电压。本文通过增加一个与升压电感耦合的反激线圈和一个连接到输出电容的整流二板管，构成反激箝位电路。在开关管关断时，反激整流二级管导通，将升压电感中存储的部分能量传输到输出电容，从而限制了升压电感两端的电压，达到箝位的目的。文中研究了升压电感和反激线圈的匝比对反激箝位作用的影响。500W原理样机的实验结果显示，该电路起到了箝位作用，改善了元器件工作环境。

Flyback Clamp of Isolated Boost Converter

Isolated Boost converter has advantages of high frequency electric isolation, multi-output solutions, lower input ripple current, and high reliability for the short circuit of the load, etc. However, the transformer leakage inductance will cause a surge voltage across the switches. To solve this problem, this paper proposes an novel flyback clamp circuit consisted of an additional flyback winding coupled with the boost inductor and a diode connected to the output terminal. When the switch is turned off, the scheme can operate and transfer part of the energy stored in the boost inductor to the bulk output capacitor, which can alleviate the surge voltage and clamp the inductor voltage to the reflected output voltage. The influence of the turns ratio of the flyback winding with respect to the boost choke on flyback clamp is discussed. An experiment on a prototype converter with a design rating of 500 W shows that the clamp mode of isolated Boost converter is effective.