Simplified analysis of PWM converters operating in discontinuous conduction mode using alternate forms of the PWM switch models

Abstract

The discontinuous conduction mode (DCM) PWM converter is modeled as a transformer by Vorperian's PWM switch model. The recognition that any of the three transformer terminals can serve as the common terminal leads to two alternate PWM transformer models and the corresponding two alternate PWM switch models. For a given PWM DC-DC converter, one of the three PWM switch models is more "natural" for graphic-oriented analysis/design, e.g., it allows the idealized converter to be analyzed by inspection. Furthermore, all three PWM transformers may be used to graphically manipulate the converter circuit to a form which can be analyzed by inspection. This is demonstrated in the paper by steady-state analysis of a buck converter. The same procedure could be applied to the boost converter.