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
$C_{\text{iss}}$
versus the gate-source voltage
$v_{\text{GS}}$
characteristics (
$C_{\text{iss}^{-}}v_{\text{GS}}$
characteristics) of SiC MOS-FETs implemented in power conversion circuits. The
$C_{\text{iss}^{-}}v_{\text{GS}}$
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
$C_{\text{iss}^{-}}v_{\text{GS}}$
characteristics are suitable as aging precursors for condition monitoring. Using the proposed gate drive circuit, the
$C_{\text{iss}^{-}}v_{\text{GS}}$
characteristics of fresh and aged
$\text{SiC}$
MOSFETs were measured. The experimental results support the effectiveness of the proposed gate drive circuit and condition monitoring system.