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

Conventional zero-current-switching quasi-resonant converters (ZCS-QRC's) 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-QRC's, a new family of actively-clamped ZCS-QRC's 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 IGBT's and BJT's) are predominantly used as power switches.