Analysis and design of asymmetrical ZVS PWM half bridge forward converter with flyback type transformer

A new asymmetrical zero-voltage switching (ZVS) pulse width modulation (PWM) half bridge forward converter with flyback type transformer is proposed. The ZVS operation of proposed converter can be maintained from no load to full load condition since the magnetizing current of the transformer contributes to the ZVS operation at the light load without a considerable conduction loss of the transformer and switch. The synchronous rectification is employed to reduce the rectification loss. The operational principle, large signal modeling, ZVS analysis, and design equations are presented. Experimental results demonstrate that the proposed converter can achieve a large ZVS range and significant improvement in the efficiency for a 100 W (5 V, 20 A) prototype converter.