Gate Drive Circuit with In situ Condition Monitoring System for Detecting Gate Oxide Degradation of SiC MOSFETs

This paper proposes a gate drive circuit with an in situ condition monitoring system for detecting the gate oxide degradation of silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (MOSFETs). Trapped charges in the gate oxide can cause fluctuations in the on-resistance and gate threshold voltages. These phenomena degrade the long-term reliability of power conversion circuits. The proposed condition monitoring system detects the degradation of the gate oxide by measuring the input capacitance Ciss versus the gate-source voltage v GS characteristics (Ciss-v GS characteristics) of SiC MOSFETs implemented in power conversion circuits. The C-iss- v(GS) characteristics are theoretically and experimentally shown to not fluctuate with temperature, whereas the characteristics fluctuate with the degradation of the gate oxide. These results indicate that the C-iss- v(GS) characteristics are suitable as aging precursors for condition monitoring. Using the proposed gate drive circuit, the C-iss-v(GS) characteristics of fresh and aged SiC MOSFETs were measured. The experimental results support the effectiveness of the proposed gate drive circuit and condition monitoring system.