JPS5854740B2 - Gate control circuit for gate turn-off thyristor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gate control circuit for gate turn-off and risk, and more particularly to a gate control circuit including a protection circuit.

A gate turn-off thyrisk (hereinafter referred to as a ``GTO thyrisk'') is a thyrisk whose on/off can be controlled by positive and negative gate control signals.Like a three-terminal thyrisk, it is turned on by a forward gate current, but the gate has no power to the cathode. By applying a negative voltage to the gate, part of the anode current is turned into a gate current in the opposite direction, thereby enabling turn-off.

Here, the turn-off time of GTO Cyrisk is G = (
The turn-off time tends to become longer as the gain G becomes larger, being affected by the value of the turn-off gain G expressed by (anode power supply)/(reverse gate power ?N).

When the turn-off time becomes longer as described above, switching loss increases, and when the gain G becomes larger than a certain value determined by the characteristics of the element, the turn-off time becomes infinite and there is a possibility that the turn-off will fail.

In severe cases, a surge current will flow through the device, leading to destruction of the device.

In view of this, it is necessary to use a small turn-off gain G in order to operate the GTO thyristor stably.

However, if the negative voltage applied between the gate and cathode of Cyrisk drops due to a short-term power outage, for example, for 0.1 to 0.3 seconds, the reverse gate current will be suppressed to a small value, resulting in a turn-off gain G. The increase was an unavoidable problem.

Conventionally, this problem was solved by increasing the time constant of the negative voltage power supply applied between the gate and cathode, but in GTO Cyrisk, where the anode current exceeds 100A, the gate current in the reverse direction also increases to several 1OA. Therefore, increasing the time constant of the negative voltage power supply is undesirable because it increases the size and cost.

The present invention has been made in an attempt to eliminate the above-mentioned drawbacks, and an object of the present invention is to provide a gate control circuit for gate turn-off and risk, which is small, simple, and highly reliable.

To achieve this object, the present invention provides a gate control circuit that is driven by an externally supplied on-command signal and an off-command signal and has a power supply element for driving a gate turn-off switch to an off state. , a state detection circuit for detecting the state of the power supply element; a first AND circuit for taking an AND of this detection circuit and the on command signal; and a first AND circuit for taking an AND of this detection circuit and the off command signal. 2 AND circuits, the first and second
The ON command signal and the OFF command signal are supplied through the AND circuit.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows an embodiment of the invention.

In the figure, when transistor 112 is brought into conduction by an on command signal, the voltage of power supply 113 is applied to the gate of thyristor 100 via resistor 114, turning thyristor 100 on.

On the other hand, the power supply 1 is connected via the diode 125 and the resistor 12γ.
The capacitor 123 is charged by the capacitor 26.

Here, when the thyristor 122 becomes conductive due to the off command signal, the gate of the thyristor 100 is reverse biased by the capacitor 123 via the resistor 124, and the thyristor 100 is turned off.

Further, according to the first embodiment, a state detection circuit 130 is provided for detecting the voltage across the power supply 126 for driving the Cyrisk to the OFF state, and further includes an output signal of this state detection circuit 130 and a command signal. AND circuits 111 and 121 perform a logical product with 5ONj and 5OFF, so that the output of the AND circuit 111 drives the transistor 112, and the output of the AND circuit 121 drives the thyristor 122.

Here, the state detection circuit 130 detects the first state signal (
11, 11 or 'o''), and in a state where the voltage of the power supply 126 is reduced and stable operation of the Cyrisk cannot be achieved, a second status signal ()+011 or '1') is output.

Therefore, under normal conditions, the detection circuit 130 outputs the signals IT,
When sending If, the ON command signal S in the state u I If.

When the N or OFF command signal 5OFF is supplied, the AND circuit 'flL121 outputs the respective command signal S.

Send N or 5OFF.

Conversely, the detection circuit 130 detects an abnormality and outputs a signal +10 I
When f is being sent, the ON command signal S in state 111TT is
Even if the ON or OFF command signal 5OFF is supplied, the AND circuit 111゜12.1 does not send out a signal and the SI risk 1
00 is never driven.

The state detection circuit 130 is configured as shown in FIG. 2, for example.

That is, when the power supply 126 is at a certain voltage or higher, the Zener diode 131 is in a conductive state and the photocoupler 133 is driven via the resistor 132.
The light receiving element 133b becomes conductive due to the light emitted from the light receiving element 133b, and the signal I+ 111 is sent out by the power source 134 and the resistor 135.

Further, when the voltage of the power supply 126 becomes lower than a certain value, the Zener diode 131 becomes non-conductive, the photocoupler 133 is not driven, and the detection circuit 130 sends out a signal "O'".

FIG. 3 shows another embodiment of the present invention, in which a capacitor 323 is used as a power source element for driving the thyristor 300 into the OFF state, and the voltage across this capacitor 323 is detected by a detection circuit 330. It is.

When the transistor 312 becomes conductive, the power supply 3
13 and the resistor 314, the Cyrisk 300 is turned on, and at this time, the capacitor 323 is charged.

Therefore, when the thyristor 322 becomes conductive, the thyristor 300 is reverse biased by the voltage of the capacitor 323 through the resistor 324, and is turned off.

Here, the voltage across the capacitor 323 is detected by the detection circuit 33.
By detecting it as 0 and using it as one input of the AND circuits 311 and 321, the same effect as the embodiment shown in FIG. 1 can be obtained.

Note that the initial state of the capacitor 323 must be in an uncharged state (charged charge = 0), but normally the capacitor 323
Due to the leakage resistance valve of 3 itself, the finite impedance of the detection circuit 330, the uncharged state is maintained.

However, the thyristor 322 turns on and the capacitor 323
The charge flows through the resistor 324 and returns to the thyristor 3 during discharge.
22 is turned off, a charge remains in the capacitor 323.

Therefore, as shown in FIG. 3, a series circuit of a diode 331 and a resistor 332 is connected in parallel to the capacitor 323.

In this way, the residual charge can be discharged and the capacitor can be brought into an uncharged state.

If the gate control circuit as described above is applied to an inverter, it will be as shown in FIG. 4 (only one phase is shown for convenience), and the voltage of the power source 400 is taken out as an alternating current voltage via the transformer 401.

The voltage at each part is as shown in Figure 5, where ga is the gate voltage of Cyrisk 100A, and the figure is the gate voltage of Cyrisk 100A.
B shows the gate voltage, and C in the figure shows the output voltage of the transformer 401.

The present invention can provide a small, simple, and highly reliable gate control circuit for a gate turn-off circuit by monitoring the voltage across the power supply element that drives the circuit in the off state as described above.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of an embodiment of this invention, Fig. 2 is a main circuit diagram of an embodiment of this invention, Fig. 3 is a circuit diagram of another embodiment of this invention, and Fig. 4 is a circuit diagram of an embodiment of this invention. Application example circuit diagram of the embodiment,
FIG. 5 is a diagram of voltage waveforms at various parts of the application example shown in FIG. 100.122.300.322...Sirisk, 111.121,311.321...AND circuit, 112,312...Transistor, 1
13゜126.134,313,400...Power supply, 123゜323...Capacitor, 130,
330...state detection circuit, 131...
Zener diode, 133...photocoupler,
401...Trance.

Claims (1)

[Claims] 1. An on-power element for driving the gate turn-off thyristor to the on-state, an off-power element for driving the gate turn-off thyristor to the off-state, and an output voltage of the off-power element. a detection circuit that detects whether or not the value is greater than or equal to a predetermined value; a first AND circuit that takes the logical product of the output of this detection circuit and an on-command signal supplied from the outside; a second AND circuit that takes a logical product of the off command signals to be output, and a first switching element that is driven by the output of the first AND circuit and provides a gate signal from the on power supply element to the gate turn-off signal. , a second switching element driven by the output of the second AND circuit and providing a gate signal from the off-power supply element to the gate turn-off switch.