Analysis of integrated buck-flyback ZVS converter

This paper presents the system analysis and circuit implementation of a soft switching converter based on buck-flyback topology to have a large voltage step-down between the output and input sides. Compared with the conventional buck converter, the proposed converter has wide turn-on period so that the lower output voltage can be achieved. An active snubber circuit is connected in parallel with the main switch to achieve zero voltage switching (ZVS). The resonance is based on the output capacitance of power switch and resonant inductance at the transition interval between the main and auxiliary switches. Therefore, the turn-on switching losses of power switch are reduced. The circuit configuration, system analysis, and design consideration of the proposed converter are presented in detail. Finally, experimental results based on a laboratory prototype with 240 W rated power are provided to verify the effectiveness of the proposed converter.