Base drive for high current low loss bipolar power transistor switches

After an overview of literature on base drives, a new transformer coupled base drive circuit is described which is particularly suitable for high current transistor switches. It has the advantages of very low component count and cost, small size and high efficiency with no driver transistors being rated at full base current. The operation of the main transistor in deep saturation results in low conduction losses, and the dynamic characteristics of the switch are shown to be suitable for inverter applications. A simple mathematical model is proposed and experimental results on a drive for a 350A switch are given.