An IGBT Junction Temperature Estimation Method Based on Turn-Off Maximum diC/dt With Decoupling Load Current

Monitoring the junction temperature T-j of insulated gate bipolar transistor modules is crucial for reliable operation in medium/high voltage applications. Among the various temperature-sensitive electrical parameters, the maximum collector current falling rate di(C)/dt(max) is an effective indicator characterized by excellent linearity and amenability to real-time detection. However, current acquisition methods are prone to introduce parasitic parameters, and di(C)/dt(max) is also affected by the load current i(load). In response to these challenges, the printed circuit board Rogowski coil is proposed to measure di(C)/dt(max) and i(load), which can decouple the effect of i(load), and this method has the advantage of being contactless and integratable. In this article, the dependence of di(C)/dt(max) on T-j and i(load) is theoretically analyzed. The system design of the Rogowski coil current sensor, including coil structure, integrator, and peak detection circuit is carried out. The effective bandwidth and measurement accuracy of the sensor are verified based on the vector network analyzer and the double pulse test, and the effectiveness of the method for T-j estimation is verified based on the buck converter.