A Comparison of Chip Temperature Acquisition Technologies of IGBT Power Modules

Accurate measurement and real-time monitoring of the junction temperature is vital for reliability and performance of insulated-gate bipolar transistor (IGBT) power modules and is a continuously developing area. This study presents a performance comparison of the recent advances in fibre Bragg grating (FBG) sensor application for direct on IGBT chip temperature measurement, with the leading conventional methods for junction temperature acquisition: the chip’s on-state voltage (VCE) based temperature evaluation and the non-contact temperature measurement using a thermal camera. The implementation features, accuracy, limitations and potential error sources for each method are evaluated and compared based on practical tests on a commercial IGBT module. The results expose the VCE based temperature evaluation’s susceptibility to voltage noise and disparities in voltage drops across IGBT terminals and bond wires, with limited and challenging to implement practical methods available to mitigate these. In contrast, the in-situ FBG sensors offer accurate localized real-time IGBT temperature monitoring at a cost of being intrusive to the power module’s geometry. The thermal camera based measurements of IGBT die temperature are found to be limited in practical application by the requirement of a clear line of sight and relatively low response rate of most commercial cameras. The presented analysis aids the understanding of the IGBT temperature measurement method selection and capability based on particular application needs.