Adaptive Level-Shift Gate Driver With Indirect Gate Oxide Health Monitoring for Suppressing Crosstalk of SiC MOSFETs

Abstract

An adaptive level-shift gate driver with indirect gate oxide health monitoring for suppressing crosstalk of bridge-leg configured SiC MOSFETs is proposed. This paper firstly presents a holistic assessment of the changes in major intrinsic parameters before and after aging SiC MOSFETs with repetitive short-circuit tests. Gate leakage is found to be an appropriate precursor to reflect gate oxide degradation. Then, the structure, operation, and design of the proposed gate driver are given. The working principle is based on using a digitally controlled variable resistor in a resistor-capacitor-based voltage divider network to adjust the off-state gate-source voltage. Then, the peak off-state gate-source voltage caused by the spurious voltage is regulated at a level that can avoid shoot-through and reduce off-state voltage stress on the gate. Besides suppressing crosstalk, an optimal off-state gate-source voltage can also improve the life expectancy of SiC MOSFET. By utilizing the loading effect of gate leakage current on the proposed gate driver output, the gate oxide degradation is indirectly monitored by observing the change in the value of the variable resistor. The proposed gate driver has been evaluated on a 1kW inverter prototype under various intrinsic parameter variations. Performance comparisons between proposed and traditional gate drivers are given.