On-line Junction Temperature Estimation of SiC Power MOSFETs through On-state Voltage Mapping

This paper deals with real-time estimation of the junction temperature of SiC power MOSFETs. The junction temperature of one device of a 4-switch module is real-time estimated by measuring its current and on-state voltage VON at each switching period and entering the temperature look-up table of the device. The temperature model is preliminarily obtained in a dedicated commissioning session, where the VON is measured at different temperature and current conditions. The results show the feasibility of on-line temperature monitoring and even active limitation of the junction temperature of the tested SiC power MOSFET modules, accurately and with an instantaneous dynamic response. Different modules with die from different manufacturers were tested in a H-bridge demonstrator power converter, emulating the operating conditions of real converters such as voltage source DC/AC or DC/DC conversion structures. The commissioning procedure is meant to be performed directly on the final application for each converter. The proposed temperature estimation technique is validated against a thermal camera and compared to direct measurement of the die temperature with a thermistor, showing high accuracy and high feasibility.