Online Junction-Temperature Extraction Method for SiC MOSFETs Utilizing Turn-on Delay

This paper presents a method that extracts junction temperature of SiC MOSFETs by measuring a unique turn-on delay. In preceding work, the turn-on delay was identified as a particularly promising temperature-sensitive electrical parameter for SiC MOSFETs. The reasons for this are its simple calibration, its insensitivity to the device current, its linear temperature dependency as well as the particular behavior of the charge carrier mobility of SiC. However, state-of-the-art extraction circuits for turn-on delay only work with a limited time resolution. Thus, they can only be applied to slowly switched SiC MOSFETs. This work proposes a circuit for turn-on delay extraction with a time-to-digital converter that allows the time resolution to be significantly increased. Thereby, the circuitry allows utilizing turn-on delay as an effective temperature-sensitive electrical parameter for junction temperature extraction of SiC MOSFET operated with fast switching transients. The feasibility of the approach is experimentally validated in this work with a developed extraction circuit using a SiC MOSFET power module as a device under test.