US 5,493,247 AGranted

Gate circuit for hard driven GTO

AssigneeAsea Brown Boveri AG

InventorHorst Gruning

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Abstract

In a circuit for hard driving a GTO, the conductor inductance (L1) and the internal inductance of the GTO (L2) form, together with a first capacitor (C1) situated in parallel via a switch (S), a series resonance circuit inside the gate circuit. In this connection, the chosen sizes of the first capacitor (C1) and of the first inductance (L1) are such that, if the first capacitor (C1) discharges via the two inductances (L1, L2), the gate current originating from the first capacitor (C1) exceeds half the value of a GTO anode current to be turned off within less than 5 .mu.s in the first quarter cycle of the series oscillatory circuit. Moreover, first means are provided which uncouple the first capacitor (C1) from the generation of the gate current after the first quarter cycle of the resonance circuit and allows the gate current to decay slowly in such a way that, at any time, it is greater than the tail current of the GTO. Finally, second means are provided in the form of a recharging circuit, which means are activated during the decay of the gate current and apply a holding current (V.sub.H) which is sufficient for blocking the gate (G) of the GTO after the decay of the gate current.

Claims7

Dependent claims

A GTO thyristor circuit comprising:

a gate turn-off thyristor (GTO) having an anode, a cathode and a gate;
a drive circuit connected between the gate and the cathode of the (GTO) for switching the (GTO) on and off by applying a gate current to the gate, said driving circuit having conductors and components defining a first inductance and said (GTO) thyristor defining a second inductance, the driving circuit further comprising:
a switch having a first end and a second end, the first end connected to the gate of the (GTO);
a first capacitor connected between the second end of the switch and the cathode and situated in series with the first and the second inductance forming a series resonant circuit;
first means disposed in parallel with said first capacitor, for uncoupling the first capacitor from the gate current after a first quarter cycle of the series resonant circuit and for allowing the gate current to decay slowly such that the gate current is greater than a tail current of the (GTO) at any time, the first means including a first diode having a cathode connected to the cathode of the (GTO);
and
second means, including a series circuit of a second capacitor and a second diode, disposed in parallel with said first capacitor, the second means applying a holding voltage sufficient for blocking the gate of the (GTO) after a decay of the gate current, wherein the second means is activated during the decay of the gate current.

4 more elements

Dependencies are inferred from the claim text.