Online Estimation of the Junction Temperature Based on the Gate Pre-Threshold Voltage in High-Power IGBT Modules

A model for the online estimation of junction temperature based on the gate pre-threshold voltage in high-power insulated-gate bipolar transistors (IGBTs) was proposed. First, the turn-on behavior and temperature dependence of the gate-emitter voltage during the turn-on delay period were studied. It was revealed that the turn-on waveform of the gate-emitter voltage exhibits a point of inflection after which the voltage between the gate and emitter increases significantly; at this point, the relationship between the voltage and the temperature changes from a positive correlation to a negative correlation. Meanwhile, analyses on the basis of semiconductor physics revealed that the negative correlation between gate-emitter voltage and temperature is caused by the temperature dependence of the flatband voltage. Finally, a model for estimating the junction temperature was established based on a combination of the turn-on delay time and the gate prethreshold voltage which is negatively correlated with the temperature, to eliminate the effect of the bus voltage.