IGBT Gate Driver with Accurate Measurement of Junction Temperature and Inverter Output Current

This paper presents a new gate driver that consists of two measuring circuits to determine the junction temperature and the output current of an IGBT or MOSFET power module during inverter operation. To achieve this, a temperature and a current sensitive electrical parameter of the power semiconductor is measured simultaneously. Besides the customer benefit, this combined measurement is very useful in view of accuracy, because most promising current sensitive parameters are also temperature sensitive. For accurate current measurement the gate driver uses the on-state collector-emitter voltage UCE(on) and compensates the impact of the junction temperature by means of the on-chip internal gate resistor RGi. This paper focuses on the accuracy of this new approach and presents two innovative measuring circuits to determine the internal gate resistor and the on-state collector-emitter voltage with high robustness and technical feasibility. Special attention is paid on the calibration and the implementation of the measuring concepts within a gate driver prototype. The sensor properties are examined in double-pulse tests and during the real inverter operation. With an overall error of 1-5% the new gate driver represents a perfect solution to address diagnostic and functional safety issues, but also lower-performance control tasks, with minimum costs. For MOSFETs (Si and SiC) the concept is even more promising.