Quasi-Resonant Voltage Doubler With Snubber Capacitor for Boost Half-Bridge DC–DC Converter in Photovoltaic Micro-Inverter

Abstract

This paper proposes a quasi-resonant boost half-bridge dc-dc converter with high power conversion efficiency and a wide input voltage range for a photovoltaic micro-inverter. The proposed converter has a combined structure of a boost-integrated half-bridge converter on the primary side of the transformer and a voltage doubler with a snubber capacitor on the secondary side. By using the quasi-resonance techniques, it achieves zero-voltage switching (ZVS) turn-on and low turn-off losses for the switches, as well as ZVS turn-on for the diodes. In addition, the proposed converter has no dc-magnetizing current for the transformer due to the dc-blocking capacitor, and it doubles the voltage gain with half the voltage stress of diodes through the voltage doubler. The effectiveness of the converter was verified with a 300-W prototype with an input voltage range of 13-50 V, an output voltage of 400 V, and a switching frequency of 50 kHz. The experimental results show that the converter had more than 90.0% power conversion efficiency for the output power range of ~300 W, and its maximum power conversion efficiency was 97.5% for an output power of 160 W.