Robust On-line Junction Temperature Estimation of IGBT Power Modules based on Von during PWM Power Cycling

Estimation of the junction temperature Tj is key for protection, diagnostics and prognostics of power IGBT modules. Requirements are low-cost, low calibration effort, low intrusiveness, high accuracy, and high robustness. The objective of this paper is to present an on-line Tj estimation method using low load-current pulses for IGBTs and diodes based on the onstate voltage Von as a Temperature Sensitive Electrical Parameter (TSEP). It associates for the first time a calibration, a model, a pulse generation, a measurement and a robustness tuning to generate an estimation with highest performances. The implemented auto-calibration procedure relies on a reduced set of 3-dimensional data. The temperature estimation method is validated on a PWM switching converter, whereby the interruption of the nominal process is shorter than 100us. The estimations are compared to the measurements taken with infrared camera, with error smaller than ±3°C. In addition, a simple analytical on-line method is proposed to correct the errors caused by successive wire-bond lift-off, attributable to the natural ageing of the module, and maintain it within less than ±2°C. The on-line, accurate, robust and practical implementation of Von as a TSEP, as demonstrated in this paper, is intended for condition monitoring of power semiconductor modules in power cycling and field applications.