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

This letter proposes a 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 non-invasive 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 (HTGB) 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.