Voltage-clamped forward quasi-resonant converter with soft switching and reduced switch stress

An auxiliary voltage-clamped reset winding is introduced into a conventional forward quasi-resonant converter (QRC) for improving the common defect of huge voltages across resonant switches. In this circuit topology, the parasitic capacitance of the switch is used with the magnetising inductance of the transformer for the resonant action. Moreover, the auxiliary winding in this circuit is utilised for resetting the magnetic flux of the transformer and clamping the peak resonant voltage of the switch. In addition, experimental results taken from a laboratory prototype with input voltage of 90 V and output voltage of 50 V are presented to demonstrate the effectiveness of the proposed voltage-clamped forward QRC in comparison with a conventional forward QRC.