A Passive Augmented Circuit for EMI Reductions of Full-Bridge Inverters With Conventional Phase Shift Control in Wireless Power Transfer Systems

In this article, a passive circuit is designed for full-bridge inverters with conventional phase shift control in wireless power transfer (WPT) systems to achieve zero-voltage switching (ZVS) for any load conditions. The passive circuit is consisting of two diodes, two capacitors, and one inductor without any active switches. The implementation of ZVS can reduce the electromagnetic interference (EMI) radiation of the full-bridge inverter with the phase shift angle from 0° to 180° (full range). Both simulation and experimental results have validated that the proposed auxiliary circuit can address the hard switching issue of the conventional WPT system, and ZVS can be achieved for the full-bridge inverter in both constant current and constant voltage control modes of the WPT system. The empirical EMI tests reveal that the augmented circuit can significantly reduce the conducted EMI of the driving circuit with a full range of phase shift angle to meet the standard EN55022.