JPH0438597Y2 - - Google Patents

Description

[Detailed Description of the Invention] A. Field of Industrial Application The present invention relates to a state detection circuit for a gate turn-off thyristor (hereinafter referred to as "GTO thyristor").

B. Summary of the invention This invention is combined with the gate circuit of a GTO thyristor, and the voltage between the gate and cathode is
The detection circuit that detects the state of the GTO thyristor uses two photocouplers that operate according to the voltage between the gate and cathode when it is on and the voltage between the cathode and gate when it is off, and generates an oscillation signal according to the output of these photocouplers. By extracting either a low-level signal or a high-level signal, the state of the GTO thyristor can be detected, and when a short circuit occurs, it can be determined whether it is a short circuit when it is on or a short circuit when it is off. It is made to be distinguishable.

C. PRIOR ART In order to protect electrical equipment, it is necessary to monitor, for example, a current flow control unit, and to take immediate countermeasures in the event of a failure. For this reason, the status of the GTO thyristor built into the device is detected, and the detection circuit is generally one that detects the voltage between the anode and cathode.

D Problems to be solved by the invention However, with conventional detection circuits, the circuit configuration is complicated, and although it is possible to determine whether there is a short circuit or not, it is possible to determine whether it is a short circuit when it is on or when it is off. It is not possible to distinguish between short-circuit conditions and short-circuit conditions. On the other hand, in order to take appropriate countermeasures in the event of a GTO thyristor failure, it is desirable to be able to distinguish whether the condition is on or off.

The present invention was developed based on these circumstances, and has a simple configuration, high reliability, and
Moreover, it is an object of the present invention to provide a state detection circuit that can distinguish between short circuit states of GTO thyristors.

E. Means for Solving the Problems The present invention includes a first photocoupler that turns off due to a voltage drop between the gate and cathode when the GTO thyristor is in the on state and short-circuited;
a second photocoupler that is turned on by a voltage between the cathode and gate when the GTO thyristor is normal and in the off state; an oscillator that outputs an oscillation signal when the first photocoupler is in the on state; and the oscillator. an OR circuit whose output is supplied to one input terminal, and a DC power supply which supplies a high-level signal to the other input terminal of the OR circuit only when the second photocoupler is in an on state, for example. It is what it is.

F Effect The output of the OR circuit is, for example, an "oscillation signal" and a "high level signal" when the GTO thyristor is normally on and off, respectively, and a "low level signal" when a short circuit occurs when it is on, and a "low level signal" when it is off. For example, it becomes an "oscillation signal."

G. Embodiment FIG. 1 is a circuit diagram showing an embodiment of the present invention.
E ₁ is a DC power source for turning on, R ₁ is a resistor, and T _r1 is a transistor for turning on, and these constitute an on-gate circuit. E ₂ is DC power supply for off, R ₂
is a resistor, T _r2 is an off transistor, and these constitute an off-gate circuit.

The emitter of the on-transistor T _r1 and GTO
A first photocoupler 2 is provided between the cathode of the thyristor 1 and the first photocoupler 2 which turns off when the emitter voltage of the transistor T _r1 is smaller than a predetermined value. A second photocoupler 3 is provided which is turned on when the voltage between the gates is greater than a predetermined value. D ₁ and D ₂ are diodes. 1st
On the output side of the photocoupler 2, there is a first circuit that is turned off or on depending on whether the photocoupler 2 is turned on or off.
A transistor T _r3 is connected to the output side of the second photocoupler 3 via a Zener diode _ZD1 , and a second transistor T _r4 is connected to the output side of the second photocoupler 3, which is turned off and on depending on whether the photocoupler 3 is turned on or off.
is connected through a Zener diode ZD ₂ . One input terminal of an OR circuit 4 made up of diodes D ₃ and D ₄ and an oscillator 5 are connected to the collector of the first transistor T _r3 .
The collector of the transistor 3 is connected to the other input terminal of the OR circuit 4 and a DC power supply E ₃ for supplying a high level signal to the OR circuit 4. _R3 to _R7 are resistances.

Next, the operation of the above embodiment will be explained.
When the GTO thyristor 1 is turned on in a normal state, a gate current flows between the gate and cathode of the GTO thyristor 1 from the ON DC power source E ₁ via the resistor R ₁ and the transistor T _r1 . At this time, by keeping the input voltage of the first photocoupler 2 higher than the operating voltage, the photocoupler 2 is turned on. Note that in order to increase the input voltage of the photocoupler 2, for example, a transistor
Connect a diode in series with T _r1 . On the other hand, since the second photocoupler 3 is in the off state, the first transistor T _r3 and the second transistor T _r4 are in the off and on states, respectively, so that the OR circuit 4 outputs the oscillation signal from the oscillator 5. be done.

When the GTO thyristor 1 is normally off, a gate current flows from the off DC power source E ₂ through the cathode and gate of the GTO thyristor 1 to the resistor R ₂ and the transistor T _r2 . At this time, the first photocoupler 2 is in the on state and the output from the oscillator 5 is supplied to one input terminal of the OR circuit 4, but the second photocoupler 3 is in the on state and the second transistor T _r4 is turned off, which reduces the voltage of DC power source E ₃ and resistances R ₆ and R ₇
A signal with a voltage level determined by (high level signal) is output from the OR circuit 4.

If the GTO thyristor 1 is short-circuited when it is on, the emitter voltage of the transistor T _r1 decreases, so the first photocoupler 2 becomes off. On the other hand, since the second photocoupler 3 is in the off state, both transistors T _r3 and T _r4 are turned on, and as a result, the OR circuit 4 outputs a low level signal.

If the GTO thyristor 1 is short-circuited when it is off, the first photocoupler 2 and the second photocoupler 3 are turned on and off, respectively, so that the OR circuit 4 outputs an oscillation signal from the oscillator 5.

The state of the GTO thyristor 1 is detected based on the output signal from the OR circuit 4 thus generated, and when the thyristor 1 is short-circuited, it is possible to distinguish whether it is a short-circuit state when it is on or a short-circuit state when it is off. be done. For example, OR circuit 4
An output circuit that outputs when an oscillation signal is detected at the subsequent stage,
By providing a matching circuit that matches the output signal of this output circuit and the on-gate signal, it is possible to distinguish between a normal on state and an off short circuit state.

H. Effects of the invention As described above, according to the invention, two photocouplers that operate according to the gate-cathode voltage when on and the cathode-gate voltage when off are used, and oscillation occurs according to the outputs of these photocouplers. The configuration is simple and reliable, as it extracts either a signal, a low-level signal, or a high-level signal.
Since it is possible to distinguish between short-circuited GTO thyristors, appropriate countermeasures can be taken.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention. 1... Gate turn-off thyristor, 2, 3...
...Photocoupler, 4...OR circuit, 5...Oscillator, _E1 ...DC power supply for ON, _E2 ...DC power supply for OFF, _E3 ...DC power supply.

Claims (1)

[Claims for Utility Model Registration] In a state detection circuit of a gate turn-off thyristor combined with a gate circuit of the gate turn-off thyristor, when the gate turn-off thyristor is in an on state and short-circuited, it is turned off due to a voltage drop between the gate and cathode. a first photocoupler that is turned on due to a voltage between the cathode and the gate when the gate turn-off thyristor is in a normal and off state;
an oscillator that outputs an oscillation signal when the second photocoupler is in one of on and off states, an OR circuit to which the output of this oscillator is supplied to one input terminal, and one in which the second photocoupler is in on and off state. and a DC power source that supplies a high-level signal to the other input terminal of the OR circuit when the gate turn-off thyristor is in the state, and the state of the gate turn-off thyristor is detected based on the output signal of the OR circuit. Gate turn-off thyristor status detection circuit.