An Accurate Small Signal Modeling and Control Loop Design of Active Clamp Flyback Converter

Abstract

An accurate small signal model of active clamp flyback (ACF) converter is proposed in this paper. To obtain a precise model, the ESR of output capacitor was considered. Different to traditional flyback converter, because of the resonant effect, at the three to five times of switching frequency, ACF converter was added two poles which result in high oscillation in frequency responses curve. To get sufficient phase margin and avoid resonant inductor oscillation affect, a fundamental error compensator was given to keep control loop stabled. Then a 65W prototype was implemented to verify the performance of the designed control loop, the simulation and experimental results showed that the adjusted process between different load status haven't result in much voltage overshoot or undershoot and need a long regulate time.