Common-Mode Filter Design for a Transformerless ZVS Full-Bridge Inverter

The zero voltage switching (ZVS) full-bridge inverter can achieve high efficiency using ZVS sinusoidal pulsewidth modulation (ZVS SPWM) and superjunction MOSFET. For further application in a photovoltaic (PV) system, the leakage current problem of a ZVS full-bridge inverter is investigated. First, the common-mode model of the ZVS full-bridge inverter is presented. The common-mode voltage with the ZVS SPWM is found changing with high frequency and leakage current with such frequency is generated. In order to suppress the leakage current below safety standards, the common-mode filter composed of common-mode inductor and bypass capacitor is applied. The impedance of the common-mode path is analyzed, and the parameters of a common-mode filter are designed based on the common-mode model. With a small common-mode inductor and bypass capacitors, the leakage current of the ZVS full-bridge inverter is remarkably reduced, and the method is verified by the experiment.