Junction Temperature Measurement of Freewheeling Diode in IGBT Module Based on Emitter Parasitic Inductance Voltage Undershoot

The junction temperature of the freewheeling diode (FWD) is crucial for the reliability and health management of insulated gate bipolar transistors(IGBTs). This paper proposes a method for monitoring the junction temperature of the FWD using the parasitic inductance voltage undershoot <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$V_{\text {eE2-maxon}}$</tex> as a temperature sensitive parameter(TSEP). In addition, to address the problem that the current TSEPs are difficult to decouple the influence of the opposite IGBT junction temperature, it is proposed to measure the junction temperature of IGBT and FWD by voltage undershoot of different switching dynamics, and then achieving decoupling. Finally, a double-pulse test platform is designed and set up to verify the theoretical analysis. The experimental results show that <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$V_{\text {eE2-maxon}}$</tex> has a good linear relationship with the junction temperature of the FWD and IGBT, so a 3-D lookup table of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$V_{\text {ee2-max}}($</tex> on <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$)-T_{\text {igbt}}-T_{\text {fwd}}$</tex> can be established to estimate FWD junction temperature online.