Fast and Accurate In-Circuit Calibration of TSEP Curves for Junction Temperature Estimation

The physical size of modern power converters is constantly shrinking, while their power output is increasing. This requires innovative thermal management solutions to handle the power density growth. In this scenario, a real time estimate of the transistor junction temperatures avoids overheating issues, increasing the converter reliability. While a direct measurement is often not feasible, an indirect temperature estimate can be obtained with temperature-sensitive electric parameters (TSEPs). Adopting this technique usually requires an extensive individual characterization of each power device, involving laboratory equipment and thus limiting the method adoption. This article presents a complete solution to accurately characterize the chosen TSEP, adopting a fully in-circuit technique and a custom active gate driver (AGD). This method extracts the required characteristics from each power device, using only the hardware resources of the power converter. The proposed procedure manages the entire calibration process, dealing with device heating, measurement, data collection and synthesis of the temperature estimation model. The authors aim to make the proposed method suitable for a production environment, boosting the adoption of TSEP-based techniques in commercial converters. In this article the proposed procedure is leveraged to characterize and use the on-state resistance TSEP for online estimation in discrete silicon-carbide MOSFETs, although its applicability to other TSEPs and devices is also discussed. Finally, extensive experimental testing is conducted to evaluate the method effectiveness.