An Online Monitoring Method of IGBT Junction Temperature Based on Turn-Off Miller Plateau Current

Abstract

The insulated gate bipolar transistors (IGBTs) are most widely used in power electronics converters, and the junction temperature is a significant indicator for evaluating the IGBT reliability. In this article, in order to realize noninvasive monitoring of the main power circuit, the Miller plateau current is adopted as the thermosensitive electrical parameter (TSEP), and the proposed method can realize high accuracy for monitoring junction temperature of IGBTs. First, the Miller plateau current is adopted and studied as the gate-side TSEP. The turn-off process of IGBT and the character of Miller plateau current are studied. Subsequently, a sampling circuit and the parameters calculation method based on current transformer (CT) have been designed and analyzed. The uncertainty and integrability of sampling circuit have been discussed. Finally, the double-pulse test and inverter experimental platforms have been developed to validate the theoretical analysis. The experimental results have confirmed the accuracy of the theoretical analysis, the proposed method can achieve high accuracy and sensitivity for monitoring junction temperature of IGBTs from the gate-drive side. In addition, the sampling circuit is simple and easy to be integrated on the gate-drive circuit.