Modeling Turn-off Process of High-Power IGBT Based on Both Quasi Static and Nonquasi Static Assumptions

The calculation for carrier distribution in the quasi-neutral base region is necessary for modeling the turn- off process of an insulated gate bipolar transistor (IGBT). The carrier distribution difference between quasi static (QS) and nonquasi static (NQS) conditions and its influences on turn- off characteristics of a high-power IGBT are worthy of further study. In this article, the carrier distribution differences between QS and NQS conditions in different turn- off stages are first analyzed. In addition, based on the derived conclusions, a novel method modeling the turn- off process of high-power IGBTs is further proposed. In the method, the turn- off process before the collector–emitter voltage increases to the direct current (dc) voltage is modeled under the QS condition. In contrast, after the collector–emitter voltage increases to the dc voltage, the turn- off process is modeled under the NQS condition. Subsequently, the method is verified by comparisons with popular models and experiments. By adopting both QS and NQS assumptions, the proposed method can simplify the calculation and avoid considering the two-dimensional carrier distribution effect in the base. The method is implemented into SABER circuit simulator with MAST language and shows a high accuracy and considerable calculation efficiency.