A High-Frequency Soft Switched Inverter with a Low-Loss and Low Device Stress Auxiliary ZVT Circuit for High-Voltage Applications

The virtues of Wide Band Gap (WBG) devices and the increasing importance of inverters in the future grid have laid the foundation for high-frequency inverters to emerge as they offer miniaturization by reducing output filter size. Nonetheless, mitigating the high switching losses can be technically demanding, and hence the soft-switching inverters have become conspicuous. In this paper, we have proposed a low-loss zero-voltage-transition (ZVT) auxiliary circuit which helps realize a low device stress for a high-voltage application. The auxiliary voltage is obtained from a low-power flyback converter. Just one flyback converter is needed for all the poles of the inverter. While this ZVT circuit helps achieve zero voltage switching (ZVS) for the main switches, the auxiliary MOSFET turns off with zero-current switching (ZCS). The conduction time of the auxiliary ZVT circuit is minimal compared to the switching period, hence consuming low power. The ZVT circuit design and operation are validated with extensive simulation and experimental results.