Measurement Deviation of the Virtual Junction Temperature by the Saturation Voltage Drop Method for Insulated-Gate Bipolar Transistors

In engineering application, the saturation voltage drop (<inline-formula> <tex-math notation="LaTeX">$V_{\text {CE}}$ </tex-math></inline-formula>) method is widely used for junction temperature prediction. However, it is difficult to characterize the peak temperature by the virtual junction temperature measured by the <inline-formula> <tex-math notation="LaTeX">$V_{\text {CE}}$ </tex-math></inline-formula> method. In this article, the reasons why the virtual junction temperature is lower than the peak junction temperature were explained by analyzing the internal current distributions of the module for different temperature distributions. Using an equivalent model composed of discrete devices, the virtual junction temperatures for different temperature distributions and measuring currents were measured. The current-weighted temperatures for different measuring currents were also calculated using the branch current. The virtual junction temperature and current-weighted temperature were compared and investigated in combination with simulation results under ideal conditions. The variation law of the virtual junction temperature with the sense current and the temperature distribution was determined, which will aid in the measurement of the junction temperature in engineering.