A unified method for the small-signal modelling of multi-resonant and quasi-resonant converters

A method based on the averaging technique for the small-signal modelling of multi-resonant and quasi-resonant DC-DC converters is presented. The characteristic functions of the switching devices are defined and are determined using a numeric algorithm for multi-resonant converters and analytic calculations for quasi-resonant converters. 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 converters is the same as that of the conventional pulse-width-modulated 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.