Closed-loop control of switching transition of SiC MOSFETs

This paper presents a novel closed-loop active-gatecontrol (AGC) circuit for high-voltage SiC MOSFETs, used in the high-voltage, high-frequency and high-power-density applications. The proposed controller independently adjusts the switching di/dt and dv/dt by closed-loop control of the gate current and enables one to reach optimal performance in terms of loss, device stress, and EMI. The di/dt is adjusted to control the overvoltage stress and peak reverse recovery current while the dv/dt is adjusted to control the common mode (CM) noise and switching loss. The dv/dt is the primary source of the common mode noise in power electronics converters. Dynamic control of switching dv/dt has been somewhat overlooked in the state-of-the art works based on Si based power semiconductor devices (PSDs), and maximum achievable dv/dt is used to decrease the switching loss. However, the magnitude of generated dv/dt in the high-voltage SiC-based applications is appreciable because of the exceptionally higher switching speed of the SiC MOSFETs as compared to Si IGBTs. In contrast to other works, the proposed controller dynamically and independently controls the turn-off di/dt and dv/dt of a SiC MOSFET using closed-loop control of the gate current. Independent control of turn-off di/dt and dv/dt is achieved using a delay compensation circuit. This circuit compensates the total delay in the feedback loop and predicts the onset of transition between dv/dt and di/dt control regions. The proposed control circuit operation and advantages are presented and verified by experimental results.