Analytical model for power bipolar transistor in hard and soft-switching applications

This paper discusses the analytical model developed to explain the dynamics of a power bipolar junction transistor under both hard and soft switching (zero-voltage and zero-current) topologies. The model is developed based on nonquasi-static analysis. It is shown that the carrier dynamics during the turn-off stages of BJT in hard switching varies from soft switching. The carrier profile undergoes significant redistribution, especially in zero-current switching, which results in unique characteristics. Through this model, the physical analysis of the turn-off performance is explained. The model was tested for various critical circuit parameters and switching condition. A good match is observed between the measured and the modeled results, thus validating the model.