Novel actively-clamped zero-current-switching quasi-resonant converters

Conventional zero-current-switching quasi-resonant converters (ZCS-QRCs) suffer from disadvantages of high switch current stress and variable switching frequency. This paper proposes the use of a "current-clamping circuitry" to overcome these disadvantages. By incorporating such a circuit into the family of ZCS-QRCs, a new family of actively-clamped ZCS-QRCs is derived. These converters feature constant-frequency operation and zero-current turn-off for power transistors (without increased current stress), which are useful for high-power applications, where minority-carrier semiconductor devices (such as IGBTs and BJTs) are predominantly used as power switches.