Power bipolar transistor performance in hard- and soft-switching power converters

This paper presents a detailed performance analysis of a power bipolar junction transistor (BJT) under hard-and soft-switching conditions. The main focus is on improving the switching loss and switching time of the device. It is shown that an improvement by an order of magnitude can be obtained in turn-off loss under soft-switching as compared to hard-switching. This improvement is achieved by exploiting the interaction between the circuit and the device in soft-switching. The effect of circuit components and conditions on switching time and loss of the device is also discussed. Distinct characteristics are observed during soft-switching of the device (ZVS and ZCS). The physical mechanisms responsible for these characteristics are analyzed in detail based on the internal charge dynamics with the aid of an advanced two-dimensional mixed circuit and device simulator. The results obtained from simulations are compared and validated with extensive measured data.