Measuring the junction temperature of an IGBT using its threshold voltage as a temperature sensitive electrical parameter (TSEP)

To ensure the thermally safe operation of a power electronic module it is appropriate to monitor the junction temperatures Tj of its semiconductor devices. In addition, a condition monitoring of the power electronic module can be implemented by comparing the measured temperature data with model based calculated values. Using long-term monitoring of Tj, it is possible to determine thermal weaknesses along the heat path between chip and heat sink as well as wearout of the electrical construction. However, since it is not possible to determine the junction temperature directly in standard applications, an indirect method for determining Tj can be applied. In this paper, the concept for measuring the junction temperature of an IGBT by using its threshold voltage Vth, also known as VoE(th), is described.