A driver providing slow turn-off for unsaturated IGBT switches

摘要

During a short ON period an IGBT switch may not reach saturation. Use of a fast driver suitable for a saturated IGBT would cause very rapid turn-off in an unsaturated IGBT, leading to overvoltage and interference. To counteract this problem, a slow drive circuit 18 is selected instead of a fast drive circuit 17 when selector 24 determines that the ON pulse input on line 23 exceeds a predetermined duration. The predetermined duration may be input on line 25 and may be stored in the selector. The timer 22 counts clock pulses on line 21. The circuit may be used in railway traction converters.