A small-signal model for SEPIC, Cuk and flyback converters as power factor preregulators in discontinuous conduction mode

The authors describe small-signal models for SEPIC, Cuk, and flyback converters as power factor preregulators in discontinuous conduction mode (voltage follower approach) and constant frequency, using CIECA (current injected equivalent circuit approach). Implementations with and without input voltage feedforward, using resistive load, constant power and constant current loads, are analyzed, and their respective transfer functions are obtained. The applicability of an integrated circuit (usually used in continuous conduction mode) in the control loop is also presented. Simulation results are presented, validating the models to be used in control loop design