Analysis of ZVS PWM active clamp isolated converter with secondary voltage step up

Abstract

This article presents an isolated converter with the function of voltage step-up. An active clamp circuit is used to achieve zero voltage switching (ZVS), absorb the stored energy in the transformer leakage inductance and limit the voltage stresses on power switches. During the commutation stage of two complementary switches, the output capacitance of the switches and the leakage inductance of the transformer are resonant. Thus, power switches are turned on at ZVS. Compared to the conventional active clamp forward converter, the proposed circuit has no large output filter inductor. Thus, it has the features of simpler structure, lower cost and no effective duty loss. The voltage stresses on the output diodes are clamped on the output voltage. The circuit configuration, operation principles and design considerations are presented. Finally experimental results are presented for a converter with an input voltage of 24 V, an output voltage of 200 V and operating at switching frequency of 73 kHz, to verify the effectiveness of the proposed converter.