GTO thyristors

Major aspects of gate-turn-off (GTO) thyristors are discussed, including device modeling, design considerations, basic research on their switching phenomena, electrical characteristics, and applications. A device design is considered which would increase the maximum interruptible anode current I_ATO and blocking voltage while decreasing the switching time and power dissipation. The most difficult design problem is to determine the dominant factors that affect I_ATO. From experimental and computational results, it is found that I_ATO is increased by a reduced p-base sheet resistance, a thicker n-base layer and an increased gate-cathode breakdown voltage. The turn-off performance is also improved by introducing several modified device structures, such as an anode-shorted emitter construction, an asymmetric n⁺-doped based structure, a buried gate, and a cathode emitter heterojunction GTO thyristor. Typical characteristics are given for a 5000-V 3000-A unit. GTO applications are discussed, including variable-voltage variable-frequency inverter-controlled AC induction motor drive systems and PWM converter systems