An Online Gate Oxide Degradation Monitoring Method for SiC Mosfets Based on Turn-On Gate Voltage Filtering

This letter proposes an SiC mosfet gate oxide degradation monitoring method based on the peak value of the bandpass filtered gate voltage during turn-on transitions. The frequency range of the bandpass filter is determined to ensure a proper sensitivity of the detected peak value to the degradation level. The monitoring circuit is presented, including an analog bandpass filter, a peak detector, and a reset pulse generator. Comparing to the existing monitoring schemes, the proposed method is noninvasive and minimizes the interference and new risks to the normal operation of the gate driver. Besides, the proposed monitoring circuit is cost-effective with reduced complexity and less sampling frequency requirement. Multiple high-temperature gate bias tests are performed to accelerate the aging of SiC devices with planar, double trench, and asymmetric trench gate structures. Experimental results from a double pulse tester and a three-phase inverter under dynamic operation verify the effectiveness of the proposed health indicator and the monitoring circuit.