Active-Clamp ZVS Two-Switch Flyback Converter

This paper introduces a zero voltage switching (ZVS) two-switch flyback pulse-width modulated (PWM) DC-DC converter along with the principle of circuit operation and steady-state analysis. The proposed converter topology is the result of incorporating an auxiliary circuit in place of the clamping diodes on the primary side of the conventional hard-switching two-switch flyback converter, resulting in a soft-switching two-switch flyback converter with reduced switch voltage stresses. The auxiliary circuit is an active-clamp circuit made up of two switches and a clamp capacitor. The active clamp circuit recycles the energy stored in the parasitic transformer leakage inductance, facilitates the ZVS operation of all active switches, and limits the voltage stresses of all the active switches to a value less than or equal to the DC input voltage V-I. Circuit description, principle of operation, steady-state analysis, and simulation results of the proposed converter are presented.