Modeling of basic DC-DC converters

Three basic dc converters-buck, boost, and buck-boost converter are analyzed in this article. Instead of deriving state-space equations of converters, the averaged models of PWM switch both in CCM and DCM are developed first. The models enable to simplify analysis of dc converters without considering nonlinear PWM switch action. Incorporate PWM switch models into power stage circuits, steady-state and small-signal models of the converters can be obtained both in CCM and DCM. The criteria of judging DCM of dc converters are also developed. Finally. small-signal models are verified by comparing frequency response from small-signal model and that from PSIM AC Sweep simulation.