Die Failure Degree Evaluation Method in Multidie IGBT Power Modules Based on Turn-Off Gate Voltage Undershoot and Overshoot

Abstract

High-power converters often employ insulated-gate bipolar transistor (IGBT) modules with multiple dies connected in parallel. Evaluating the die open-circuit failure degree caused by all bonding wire liftoffs can provide failure warnings to enhance reliability. This article proposes the undershoot ( $V_{\text {ge}^{\prime }\_{\text {us}}}$ ) and overshoot ( $V_{\text {ge}^{\prime }\_{\text {os}}}$ ) based on the gate-auxiliary emitter voltage during the turn-off process as two novel die failure sensitive parameters (DFSPs) for evaluating die failure degrees. First, the analysis reveals that die open-circuit failure leads to a decrease in $V_{\text {ge}^{\prime }\_{\text {us}}}$ and $V_{\text {ge}^{\prime }\_{\text {os}}}$ , which are unaffected by operating conditions. Then, a double-pulse test platform is constructed to investigate the effects of die failure and various factors on $V_{\text {ge}^{\prime }\_{\text {us}}}$ and $V_{\text {ge}^{\prime }\_{\text {os}}}$ . The experimental results demonstrate that as the number of failed dies increases, the proposed DFSPs decrease. Moreover, the failure sensitivity is enhanced, and the method remains insensitive to variations in operating conditions. Finally, a pulse counting-based evaluation method and a circuit are proposed. This method relies solely on pulse pattern recognition without requiring precise DFSP sampling, thus offering a novel evaluation mode. The proposed circuit supports plug-and-play functionality without needing high-performance analog-to-digital converters (ADCs) or timers. This method improves robustness and simplicity while ensuring safety, providing a new perspective for failure warning of the multidie modules.