Development of Online Temperature Monitoring Circuitry for Wide Band-Gap Transistors in Motor Drive Applications

Monitoring the temperature of motor drive power transistors is essential for ensuring safety and reliability. However, sensing the die temperature may require specialized packaging or high-precision detection techniques. This study proposes a cross-voltage measurement circuit for online monitoring of transistor die temperature during motor drive operation. This method measures the transistor's on-state cross-voltage and uses the measured motor current to calculate the transistor's resistance. This allows the die temperature to be estimated from initial recorded data or the component datasheet. The proposed circuit is tested with SiC MOSFETs and GaN E-HEMTs through temperature-controlled multiple pulse tests and motor drive experiments. The pulse test shows that the on-resistance calculated from the measured cross-voltage correlates with the experimental temperature. Moreover, the drive test shows that this method can measure the component temperature online. Notably, the circuit enables cross-voltage monitoring during actual motor drive operation. The signal can be directly interfaced with a standard microcontroller via analog-to-digital conversion, offering a practical and scalable solution for online temperature monitoring in motor drives.