Soft switching single inductor push-pull converter for 250W AC module applications

In this paper, a soft switching single inductor push-pull converter is proposed. A push-pull converter is suitable for a low power photovoltaic (PV) AC module system because the step-up ratio of a high frequency transformer is high and the number of primary side switches is relatively small. But conventional push-pull converters do not have high efficiency because of high switching losses by hard switching and transformer losses (copper and iron losses) by high turns-ratio of the transformer. In the proposed converter, primary side switches are turned on at zero voltage switching (ZVS) condition and turned off at zero current switching (ZCS) condition through parallel resonance between secondary leakage inductance of the transformer and a resonant capacitor. Therefore the proposed push-pull converter decreases the switching loss using soft switching of the primary switches. Also, the turns-ratio of the transformer can be reduced by half using a voltage-doubler of secondary side. The theoretical analysis of the proposed converter is verified by simulation and experimental results.