Junction Temperature Measurement during Inverter Operation using a TJ-IGBT-Driver

The junction temperature of an IGBT power module is a key parameter for its optimal operation and reliability. In recent years different sensor systems were presented for real-time TJmeasurement, but none of these solutions could prove its functionality during the real inverter operation. For the first time this paper presents an IGBT gate driver with integrated real-time TJ-measurement and investigates its properties within a working voltage source inverter. The measurement is based on the on-chip internal gate resistor RGi, whose temperature is determined by superimposing the negative gate voltage with a high-frequency identification signal. Therefore the driver consists of a small control unit that manages the entire identification process during the regular switching operation of the IGBT and calculates its junction temperature using a pre-programmed reference sensor curve. Within an automatic one-point calibration at room temperature a certain power modules can be adjusted to this sensor curve. To demonstrate the functionality of the TJ-measurement during inverter operation the driver is integrated into one phase of a voltage source inverter. The junction temperature variations that can be measured at low-frequency phase currents and during the emulation of different load-profiles show very good agreement with the temperature that is measured with an IRcamera. Thereby the so-called TJ-IGBT-Driver offers a very good temperature and time resolution of 1 K and 2.5 ms. In summary, this paper shows a working sensor system that allows real-time junction temperature measurement of conventional IGBT power modules with very good sensor properties and in a way that is suitable for series production.