A System Level Approach for Online Junction Temperature Measurement of SiC MOSFETs Using Turn-On Delay Time

In this paper, a new online junction temperature monitoring approach for SiC MOSFETs is proposed by measuring the turn-on delay time using the system microcontroller and intelligent gate drive. Specifically, the intelligent gate drive converts the turn-on delay time to the pulse-width of a digital signal. Then the high-resolution capture module in the microcontroller (with 300 picoseconds resolution) is utilized to precisely measure the turn-on delay time. To improve the measurement sensitivity, the intelligent gate drive circuit implements a large gate resistance during the measurement period and immediately switches back to low gate resistance value for normal operations. A prototype is built, and the proposed circuit is tested in both double pulse switching tests and continuous converter operations. From the experimental results, an accurate junction temperature measurement is achieved in real-time with an error less than 1°C.