AN5177

Replaces September 2000 version, AN5177-3.0 w Using an improved gate drive to ease GTO series connection problems. w a D . w S a t e e h U 4 t .c om AN5177 Application Note AN5177 Improved Gate Drive For GTO Series Connections Application Note AN5177-3.1 July 2002 INTRODUCTION There are problems encountered with dynamic voltage sharing of series connected GTOs both at turn-on and turn-off. This application note will deal with the problems associated with turnoff and a further note will address turn-on problems. Switching high voltages using rectifier diodes or thyristors is routinely done using devices connected in series. With resistor and capacitor networks connected, 100 devices or more can be wired in series. The basic problem of series connection is to ensure good voltage sharing between devices under both static and dynamic conditions. By using devices selected within defined limits of leakage current and reverse recovery charge, together with correctly sized resistors and capacitors reliable operation is assured. Unfortunately, series connection of GTOs involves more restraints. For traditional applications such as rail traction where high turn-off currents are important series connection of GTOs has not usually been cost effective. A higher voltage GTO has been the preferred solution. However, this application note shows that even standard design GTOs when used with improved performance gate drive units can be successfully connected in series for certain ...