Online Monitoring of Degradation Sensitive Electrical Parameters in Inverter Operation for SiC-MOSFETs

A measurement setup for health and wear-out monitoring via electrical parameters is implemented in a test bench to allow online parameter observation during inverter operation for silicon carbide MOSFETs. A variety of electrical parameters are known to change during operation and over the lifetime of power semiconductor devices and can be an indicator of impending end of life. The observed parameters in this work are drain-source voltage as an indicator of bond-wire fatigue, gate current, indicating degradation in the gate oxide and threshold voltage, which is known to drift in silicon carbide power devices. Due to the isolated measurement design, high-side acquisition of electrical parameters is possible as well. Measurements in a buck-converter configuration are carried out, showing high stability in the output of the implemented acquisition circuits with an update rate of 200 samples per second. This approach has a strong significance in the development of novel power cycling test stands which combine switching losses with conduction losses.