Online Junction Temperature Monitoring of Power Semiconductor Devices Based on a Wheatstone Bridge

Monitoring the junction temperature of power semi-conductor devices is a requirement for degradation monitoring and predictive maintenance of power-electronic converters and usually achieved by online measurement of a temperature-sensitive electrical parameter (TSEP). The on-state voltage of a MOSFET or an IGBT is such a TSEP; however, a monitoring circuit has to accurately measure the small on-state voltage while withstanding the high off-state voltage across the device. This paper proposes a monitoring circuit for the on-state voltage based on the topology of a Wheatstone bridge. Compared to other approaches in the literature, the proposed circuit promises higher precision and good dynamic response properties. For validation, a test PCB is designed and experiments are carried out. In the experiments, it is shown that the proposed circuit has excellent properties in terms of off-state voltage limitation, on-state voltage resolution, and bandwidth.