Impact of the sensing current density on PN-junction based temperature estimation methods for Si and SiC power devices

Abstract

In this work, the impact of the sensing current density on the virtual junction temperature estimation methods for Si IGBTs and SiC MOSFETs using the pn junction voltage drop as TSEP was investigated. For this purpose, measurements of the temperature characteristics at different sensing current densities were performed on several Si and SiC devices. Additionally, TCAD simulations were performed to verify the measurement results. So far, 0.1% of the devices nominal current is commonly accepted as sensing current guideline for Si IGBTs and with the results of this investigation, this guideline was verified and examined regarding their applicability for SiC MOSFETs. The results indicate that whereas 0.1% of the devices nominal current yield an applicable sensing current for Si IGBTs, this guideline does not deliver a suitable sensing current for the tested SiC MOSFETs. As a consequence, a different approach to determine a suitable sensing current for SiC MOSFETs is proposed.