Dynamic Vgs-Id monitoring system for junction temperature estimation for MOS gate power semiconductors

Condition monitoring of power devices during operation is gaining importance as demand for high-reliability increases. The junction temperature of a power semiconductor device is a critical indicator of reliability. Therefore, we developed a new method for estimating the junction temperature of Si MOSFET based on the dynamic threshold voltage. The proposed method uses a tiny PCB sensor for detecting source current and capturing dynamic gate-source voltage at different current levels. The measurement circuit was successfully developed and evaluated by a double pulse test. The measured output voltage was digitized by 16-bit ADC included in the microcontroller to achieve the complete monitoring system. The temperature sensitivity of the Si MOSFET was -2.2 mV/°C and it was independent of the high side device temperature.