Recent developments in actuators: GTO and related devices

Abstract

In addition to the established silicon devices for power switching and motor control, the bipolar transistors and the thyristors, new devices such as power field-effect transistors, gate-turn-off thyristors (GTO) and integrated power devices have been developed in recent years. Power MOS field-effect transistors allow very fast switching with low control power, because they have no stored charge. Their on-state resistance, however, is very high in high voltages devices. Bipolar transistors with high volatge capability have low current gain at high current densities, mainly because of recombination of the stored charge in the emitter layers. GTO thyristors do not suffer from these effects, so they can be designed for very high voltages. Though they need high turn-off current gate pulses, GTO circuits are simpler and, in many applications, more economical than thyristor circuits, because the commutation circuit can be omitted. A short comparative description of these devices is given, and the GTO is described in greater detail. As an important example for power device integration, developments of optothyristors (or optotriacs) are shown which will result in simplified solid-state relay technologies.