Degradation monitoring of SiC MOSFET gate-oxide based on differential mode conducted interference spectrum

The gate-oxide degradation of power devices has an important impact on the normal operation of electrical equipment. Therefore, the research on the condition monitoring of gate oxide is of great significance to improve the operation reliability. In this article, a new monitoring method for the gate oxide in silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (MOSFETs) is proposed. Firstly, the degradation mechanism of gate oxide and its influence on the change rate of drain current (di/dt) during device switching are analyzed. Secondly, taking the Buck converter composed of SiC MOSFET as the research object, combined with the EMI equivalent model and conducted interference coupling path of the converter, the relationship between differential mode electromagnetic interference (DM EMI) signal and gate-oxide degradation is established. Finally, the amplitude of DM interference signal is used as the characteristic parameter to monitor the condition of SiC MOSFET gate oxide, and the effectiveness of the monitoring method is verified by experiments. The monitoring method proposed in this paper is applicable to different switching frequencies and load currents, and can monitor the healthy state of gate oxide in SiC MOSFET under laboratory environment and actual working conditions, which has strong practicability.