Analysis, design and implementation of an active clamp flyback converter

This paper presents the detailed circuit operation, mathematical analysis, and design example of the active clamp flyback converter. The auxiliary switch and clamp capacitor are used in the flyback converter to recycle the energy stored in the transformer leakage in order to minimize the spike voltage at the transformer primary side. Therefore the voltage stress of main switch can be reduced. The active clamped circuit can also help the main switch to turn on at ZVS using the switch output capacitor and transformer leakage inductance. First the circuit operation and mathematical analysis are provided. The design example of active clamp flyback converter is also presented. Finally the experimental results based on a 120 W prototype circuit are provided to verify the system performance