APPLICATION OF THE CURRENT-INJECTED MODELING APPROACH TO QUASI-RESONANT CONVERTERS

This paper describes how the current-injected (CI) method, which has b een applied only to pulse-width modulation (PWM) de-de converters, can be extended to quasi-resonant (QR) converters. The methodology for ex tending this small-signal modeling approach is described in detail. It is also shown that QR dynamic models are easy to obtain since they ar e derived directly from pulse-width-modulated converter models. These new models result in a unified block diagram from which zero-voltage-s witching (ZVS) or zero-current-switching (ZCS) transfer functions of t he basic topologies, such as buck, boost, and buck-boost operated in h alf-wave (HW) or full-wave (FW) modes, are found. As an application of this method, a ZVS boost converter and ZCS boost converter were fabri cated and tested. In addition, small-signal models of these converters were derived with the help of the state-space averaging (SSA) method. The agreement of the CI method simulations with the experimental resu lts for the two QR converters is comparable or better than that of the SSA method.