A general approach to synthesis and analysis of quasi-resonant converters

Abstract

A method for systematic synthesis of quasi-resonant (QR) topologies by addition of resonant elements to a parent PWM converter network is proposed. It is found that there are six QR classes with two resonant elements, including two novel classes. More complex QR con- verters can be generated by a recursive application of the synthesis method. Topological definitions of all known and novel QR classes fol- low directly from the synthesis method and topological properties of PWM parents. The synthesis of QR converters is augmented by a study of possible switch realizations and operating modes. In particular, it is demonstrated that a controllable rectifier can be used to accomplish the constant-frequency control in all QR classes. Links between the QR converters and the underlying PWM networks are extended to general dc and small-signal ac models, in which the model of the PWM parent is explicitly exposed. Results of steady-state analyses of selected QR classes and operating modes include boundaries of operating regions, dc characteristics, a comparison of switching transitions and switch stresses, and a discussion of relevant design trade-offs.