Smart power transistors for electronic ballasts

A new vertical power IC process was used to design a cost-competitive, three terminal TO-220 power switching device, the VB348, which is optimized for fluorescent ballast applications. This IC comprises a high voltage power bipolar transistor, MOS emitter switch, drive circuitry and protection features (including overtemperature shutdown). The application in a commercial ballast and the problems related to the various parasitic effects are discussed. Overtemperature protection and reduced variation in switching parameters are key advantages.