Operational Verification of Gate Drive Circuit With Condition Monitoring Function for Gate Oxide Degradation of SiC MOSFETs

Abstract

This paper proposes a gate drive circuit with a condition monitoring function for detecting the gate oxide degradation in 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 affect the long-term reliability of power conversion circuits. The proposed condition monitoring function detects the degradation of the gate oxide by measuring the input capacitance $C_{\mathrm{iss}}$ versus the gate–source voltage $v_{\mathrm{GS}}$ characteristics ($C_{\mathrm{iss}}$–$v_{\mathrm{GS}}$ characteristics) of SiC MOSFETs implemented in power conversion circuits. Experiments on the proposed gate drive circuit were conducted using a 400 W-rated buck converter circuit in which a SiC MOSFET is implemented. The experimental results show that the gate drive circuit is capable of online measurement of $C_{\mathrm{iss}}$–$v_{\mathrm{GS}}$ characteristics and gate drive at 20 kHz. The online measurement of the $C_{\mathrm{iss}}$–$v_{\mathrm{GS}}$ characteristics corresponds to the offline measurement with a measurement instrument, indicating the effectiveness of the gate drive circuit.

Keywords

• Condition monitoring
• gate drive circuit
• gate oxide
• long-term reliability
• SiC MOSFET