Online Junction Temperature Extraction of SiC Power mosfets With Temperature Sensitive Optic Parameter (TSOP) Approach

Accurate information of the junction temperature of SiC power mosfets ensures safe operation and helps reliability assessment of the devices. In this paper, an online junction temperature extraction method is proposed based on the electroluminescence phenomenon of the body diode of SiC power mosfets. It is found that during the forward conduction interval of the body diode, visible blue light is emitted around the chip, which ascribes to the radiative recombination in the low doped region of SiC mosfets. Experimental results suggest the light intensity changes linearly with the variation of the temperature and behaves as a temperature sensitive optic parameter (TSOP). Further, an electro-thermal-optic model is proposed to reveal the relationship between the electroluminescence intensity, forward current, and junction temperature. Based on the TSOP, an online junction temperature extraction method is proposed for SiC mosfets and verified in an SiC mosfet based inverter. Compared with state-of-the-art methods, the proposed junction temperature measurement method is contactless and immune from the aging of the package.