Characterization and physical modeling of power bipolar transistors in soft switching converters

In this paper, an extensive performance analysis of a power bipolar junction transistor (BJT) under hard- and soft-switching is discussed. The main focus is on improving the switching loss and switching time of the device by exploiting the interaction between the circuit and the device. The effect of the circuit components, switching sequence on switching loss of the device is also discussed. The charge dynamics of the device is explained in detail using simulation results from an advanced 2-D circuit and device simulator and the simulated and modeled results are compared with the measured data. In addition, two models of power BJT is proposed based on charge-control techniques. The existing models can simulate the storage time, delay time to a good accuracy. However, the fall time performance is compromised upon. This is because the existing models do not account for the charge decay due to recombination. Macromodeling technique is adopted to model the recombination current which gives a closer match with the measured results.