A Self-Regulating Active Gate Driver of Voltage Overshoot Suppression for SiC MOSFETs Under Variable Load Current Conditions

Compared to silicon-based devices, silicon carbide metal-oxide-semiconductor field-effect transistors (SiC mosfets) can present faster switching speed and operate at higher switching frequency. However, the fast switching speed of SiC mosfets and the inevitable parasitic inductance in the power loop will cause the severe voltage overshoot during the device turn-off transient. And the peak value of the voltage overshoot increases with the load current, which will further aggravate the electromagnetic interference problem and considerably undermine the device reliability. In response to the above problems, this article proposes an active gate driver (AGD) with self-regulating functionality. The proposed AGD can not only quantitatively suppress the voltage overshoot under the variable load current conditions over time, but also has less effect on switching speed and switching loss. Through feedback and detection of the drain–source voltage v_ds and its rate of change dv_ds/dt, the proposed method also achieves accurate identification of turn-off transient stage for the device. Furthermore, the proposed method can dynamically regulate the gate current of the device to control the v_ds overshoot with the set value. Finally, an experimental platform is designed to verify the proposed AGD scheme. Experimental results have shown that this method can achieve an optimal tradeoff between voltage overshoot and turn-off loss, and suppress the v_ds overshoot peak when the load current changes.