The averaging technique applied to the modelling of multi-resonant and quasiresonant converters

A method based on the averaging technique for the DC and small-signal modelling of multi-resonant and quasi-resonant DC-DC power converters is presented. The characteristic functions of the switching devices are defined and are determined using a numerical algorithm for multi-resonant power converters and analytic calculations for quasi-resonant power converters. The DC voltage conversion ratio and the small-signal control-to-output and line-to-output transfer functions are derived. It is shown that the order of the small-signal model of multi-resonant and quasi-resonant power converters is the same as that of the conventional pulsewidth-modulated power converters. Therefore, all classes of converters can be analysed using a unified method and the large body of existing knowledge concerning PWM converters can be extended to multi-resonant and quasi-resonant converters.