In-Hwan Oh
Fairchild Semiconductor

This paper presents a Parallel-Resonant DC Link (PRDCL) circuit for soft switching main power devices with a single auxiliary power device for low conduction loss in single or three-phase inverter and converter applications. The proposed resonant network with one auxiliary power device is activated whenever it is needed to change the status of power devices connected to a DC link. The proposed resonant network is designed to force the DC link voltage to drop to zero before any power devices in the DC link are turned on. The auxiliary switch in the proposed resonant network is also turned on in a Zero-Voltage-Switching (ZVS) condition. Therefore, the switching losses caused in all power devices in a full-bridge converter and resonant circuit can be effectively eliminated. In addition, there is no conduction loss in the auxiliary power device because the resonant circuit is not activated if there is no status change in the power devices connected in the DC link. Furthermore, the resonant swing voltage in the DC link is well restricted within a predefined voltage level so that the required voltage rating of all power devices in the DC link is nicely constrained. The detailed modes of operation and experimental results are provided to verify the operation.