Junction Temperature Estimation for IGBT Modules Through Knee Voltage

Thermo-sensitive electrical parameters (TSEPs) are widely employed in the junction temperature estimation of insulated gate bipolar transistor (IGBT) modules. In this paper, the IGBT on-state voltage at a low conduction current of tens of milliamps is explored as a novel indicator and named IGBT knee voltage. Unlike existing TSEPs, this specific on-state voltage is independent of the operating current and package-level degradation of IGBT modules and has a monotonic thermal dependence. As a result, the junction temperature can be estimated based on the IGBT on-state saturation voltage information without the need for synchronized current sampling and dedicated degradation calibration. A single-phase inverter case study is presented to demonstrate the proposed method. The experimental results verify the monotonic dependence between the IGBT knee voltage and junction temperature.