Junction temperature measurement method for SiC MOSFETs based on gate internal resistance

Monitoring and safeguarding the junction temperature of SiC MOSFETs can significantly enhance their longevity. This paper presents a method for calculating the junction temperature of SiC MOSFETs based on gate internal resistance, analyses the impact of junction temperature on gate internal resistance, and measures the magnitude of gate internal resistance using resonance technique. Firstly, we analyse the composition of the gate drive circuit for SiC MOSFETs and derive a formula for calculating gate internal resistance through series-based resonance measurement. Secondly, we design a circuit to acquire gate internal resistance data and build a test bench to verify our approach. Experimental results demonstrate that our calculations are accurate under different inductance conditions with an absolute error less than 60 mΩ for 87.5% of data points and less than 30 mΩ for 72.1% of data points. Moreover, 92.3% of calculated junction temperatures are within 5 °C while 64.4% are within 3 °C.