Patent GB-1430637-A (GB)
Title: Switching circuits comprising a gate controlled switching device
IPC: H03K17/73
Filed: 1973-05-10
Abstract: 1430637 Gate controlled switching device circuits SONY CORP 10 May 1973 [15 May 1972 (2)] 22344/73 Heading H3T [Also in Division H2] A switching circuit comprises a gate controlled switching device 1 (Fig. 1) having an anode, cathode and gate switching means 4 connected to the gate, a voltage source 5 connected in series to the switching means and having a polarity for providing a first gate current flowing from the cathode to the gate during conduction of the switching means, current supplying means 6 comprising an inductor 7 connected to the gate in parallel to a series connection of the switching means 4 and the voltage source 5, the current supplying means 6 providing a second gate current flowing from the gate to the cathode during the non-conduction of the switching means 4 and control signal supplying means 20 connected to the switching means 4 for controlling the conductivity of the switching means 4 in accordance with a control signal. At the instant when a gate controlled switching device 4 is made conductive by a positive control signal (S, Fig. 2A, not shown) applied from 20 a negative gate current (IG 1 , Fig. 2D, not shown) flows from the cathode of the GCS 1 to its gate so that the GCS 1 is made non- conductive. When the control signal (S) goes negative the GCS 4 is made non-conductive. Now the energy stored in a coil 7, when the GCS 4 was conductive, supplies a current (12, Fig. 2C, not shown) to the GCS 1 so as to provide a positive gate current (IG 2 , Fig. 2D, not shown) to make the GCS 1 conductive to pass current through the load 2. The GCS 1 is repeatedly controlled to be on or off in accordance with the control signals S. In the horizontal deflection output circuit of a TV receiver shown in Fig. 3 driving pulses from a horizontal oscillator (not shown) are applied to 20 so that the GCS 1 is made on or off to flow a sawtooth waveform current through the horizontal deflection coil 16. The horizontal deflection circuit further includes a damper diode 14 and a capacitor 15 for resonance. In a modification a coil (19, Fig. 4, not shown) is connected between the anode of the GCS 4 and the gate of the GCS 1 so that the turn-off gate current (IG 1 ) for the GCS 1 becomes large abruptly at its initial period and its fall time becomes short to be able to carry out its switching abruptly. In a still further modification (Fig. 5, not shown) the GCS 4 is replaced by a transistor (21) which when on supplies a turn-off gate current to the GCS 1 and a turn-on gate current from the current supplier 6 when the transistor (21) is off. In order to avoid damage to the GCS1 by overload, over current through the GCS 1 is detected by a transistor (24, Fig. 6, not shown) which turns on to trigger on the GCS 4 so as to turn off the GCS 1. In a modification of this (Fig. 7, not shown) a transistor (27) is turned off on detecting the over current through the GCS 1 and a Zener diode 31 is made conductive to turn on the GCS 4, so as to turn off the GCS 1 and protect it from over-voltage. The switching circuit can be formed as an integrated circuit.