A Voltage-Edge-Rate-Limiting Soft-Switching Inverter for Wide-Bandgap Devices

Wide-bandgap (WBG) switches can achieve switching times on the order of several nanoseconds. However, faster switches generate larger inverter output dv/dt. Various deleterious effects attributed to large inverter dv/dt have been observed in various applications, especially in motor drive systems. The effects include false turn-on of WBG switches due to crosstalk, transient over-voltages at motor terminals, electromagnetic interference, and motor bearing failures due to micro arcs. A common approach for limiting peak inverter dv/dt involves the insertion of a dv/dt filter. However, the dv/dt filter introduces extra power losses and increases the size/weight of the heat sink. Soft-switching circuits can reduce inverter dv/dt and switching losses, but using soft-switching to accurately control dv/dt has not been fully explored. A new soft-switching circuit, entitled the auxiliary resonant soft-edge pole (ARSEP), is set forth. The ARSEP improves the available soft-switching circuits so that the dv/dt can be accurately controlled through circuit parameter design. An ARSEP inverter prototype based on SiC MOSFETs was designed, simulated, built, and tested to verify its performance and benefits. Compared to a conventional hard-switched inverter with a dv/dt filter, the ARSEP inverter results in a significant reduction in overall power loss, inductor volume, and weight.