Online Junction Temperature Monitoring for SiC MOSFETs Using Turn-On Delay Time

Junction temperature is one of the most critical indicators not only for the converter design and operation but also for power devices’ reliability. Online monitoring of junction temperature can provide useful information for converter control, protection, and maintenance. In this paper, an intelligent gate driver with online Tj monitoring capability is developed for SiC MOSFETs. The turn-on delay time is selected as the thermal sensitive electrical parameter (TSEP) for online Tj estimation. Moreover, a gate resistance regulation unit is implemented with 10 times sensitivity improvement to increase the measurement accuracy. Then, an edge-detection-based online turn-on delay time measurement with 200 ps resolution is designed and integrated into the gate driver. In the end, a double pulse test (DPT) platform is applied to collect the calibration curves offline. A SiC-based half-bridge inverter is also built to demonstrate the functionality and performance of the online junction temperature monitoring system. Resultantly, this intelligent gate driver can accurately estimate devices junction temperature during inverter operation.