Analysis and implementation of a zero voltage switching bi-forward converter

The system analysis and the circuit implementation of a zero voltage switching (ZVS) bi-forward converter is presented here. Two forward converters are adopted in the circuit with the active clamp technique to achieve interleaved PWM operation and load current sharing. Only two switches are used in the proposed converter instead of the four switches in the conventional parallel ZVS converter. Thus, the circuit components and conduction losses are reduced in the proposed converter. In the proposed circuit, the PWM signals of two switches are complementary to each other with a small delay time in order to realise the ZVS turn-on of the switches at the transition interval. Thus, the switching losses and thermal stresses of semiconductors are reduced since the interleaved PWM scheme is used to control two forward converters such that the output ripple currents are partially cancelled out. The sizes of the output chokes and capacitor are reduced. Experiments based on a 300 W prototype are provided to verify the theoretical analysis and the effectiveness of the proposed converter.