The development of a power darlington transistor and hybrid integrated circuit for a DC to DC converter

A power Darlington transistor SubscreteR** and hybrid integrated circuit consisting of two of these in parallel with a fast recovery diode are described. The integrated unit is used as a dc-to-dc converter or "chopper" to control the acceleration and speed of a electric car motor and can deliver 450A of armature current. The Subscrete form permits full testing and matching of transistors before mounting on a common heat spreader. The thermal, mechanical, and electrical characteristics of the transistor Subscrete are discussed, together with the criteria used for matching and performance results obtained with the integrated circuit in a dc converter circuit.