Transient time-domain analysis of zero-current switching quasi-resonant converters

The authors introduce a general PSPICE switch model that can be used to implement zero-current switching (ZCS) in most quasi-resonant (QR) converters. This switch model allows the investigation of transient phenomenon in such converters. Using the ZCS-QR buck converter as an example, the authors show that tremendously large peak values can be encountered if the converter output filter is not properly designed. In addition, it is shown that ZCS is not guaranteed during the transient even if ZCS is achievable in the steady state. An output filter design procedure to reduce the peak values during the transient is proposed