High Off-State Impedance Gate Driver of SiC MOSFETs for Crosstalk Voltage Elimination Considering Common-Source Inductance

The crosstalk voltage on the gate-source terminal of SiC power mosfets in a phase-leg circuit is composed of the gate-drain capacitor introduced voltage and the common-source inductor introduced voltage. The mathematical model of the crosstalk voltage indicates that to suppress two types of crosstalk voltage, there exists a contradictory requirement on the off-state gate loop impedance. This challenge reduces the effectiveness of conventional crosstalk elimination methods. As an improvement, a crosstalk voltage suppression circuit that synchronously eliminates the crosstalk voltage of gate-drain capacitance and the common-source inductance is proposed. In this article, instead of creating low-impedance gate loop in the off-state, a high-impedance gate loop is formatted to eliminate the voltage drop on the common-source inductance. Meanwhile, the potential false turn-on or the negative voltage spikes caused by gate-drain capacitance is eliminated by the precharge voltage in the gate-source capacitor. The required prestored charge is analyzed considering the nonlinear behavior of the junction capacitance of the SiC mosfets. The proposed gate driver is experimentally verified in different switching conditions.