JPH04369489A - Failure detection circuit for gto element - Google Patents

Abstract

PURPOSE:To prevent thermal breakdown of an electric part in a GTO drive circuit by detecting a short circuit failure between gate cathodes of a GTO element and terminating the power of the drive circuit. CONSTITUTION:The arcless pulse peak current supplied between the gate G and the cathode K of a GTO element from a capacitor 13 during a turn-off operation is converted with CT 14 and a load resistance 16 to voltage and is detected. A comparison calculation between this detection voltage and a predetermined negative voltage Vs for comparison which absolute value is larger than the usual voltage, is performed with a comparator 17 to detect a short circuit failure in the GTO element 1.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a failure detection circuit for GTO elements.

0002

2. Description of the Related Art FIG. 3 is a circuit diagram showing a conventional driving circuit for a GTO element. In the figure, 1 is a GTO element, and although its main circuit is not shown, it is connected in series or parallel with other GTO elements to form a chopper device or the like. G and K indicate the gate and cathode of GTO element 1. E1 is an ignition power supply, E2 is an extinguishing power supply that also serves as a reverse bias power supply, 2 is an on/off command input terminal, 3 is a transistor whose base is connected to the command input terminal 2, and 4
5 is a capacitor for supplying the ignition pulse peak current (high gate current of high gate on pulse) IGM; 5 is a limiting resistor for limiting the discharge current of capacitor 4; 6
is a limiting resistor for limiting the steady gate current, 7 is a transistor for ignition, 8 is a limiting resistor for limiting the base current of transistor 7, and 9 is a one-shot for generating an extinguishing control pulse of a predetermined time width. Multivibrator (OS
M), 10 is a transistor for reverse bias, 11 is a limiting resistor for limiting the collector current of transistor 10, 12 is a transistor for arc extinction, 13 is an arc extinction pulse peak current (high gate current of high gate off pulse) IG
This is a capacitor for supplying R.

Next, the operation will be explained with reference to the time chart shown in FIG. Now, suppose that an ON command is input to the command input terminal 2 and becomes H level, and accordingly, the transistor 3 and the transistor 7 are turned on. As a result,
The charge accumulated in the capacitor 4 is discharged through the limiting resistor 5 and the transistor 7, and the gate G of the GTO element 1 is discharged.
- supplying an ignition pulse peak current IGM between the cathode K; After the capacitor 4 is discharged, a current is supplied from the ignition power source E1, and this current becomes an ignition pulse steady-state current IG limited by the limiting resistor 6. In addition, in FIG. 4, VG shown by the dotted line in the G-K output during the on period is the gate forward voltage,
Usually less than a few volts.

[0004] In this state, when an off command is input next, the command input terminal 2 falls to the L level. Along with this, transistor 3 is turned off and its collector potential rises, transistor 7 is turned off, and OSM
9 is driven, outputs an arc-extinguishing control pulse, makes the transistor 12 conductive for a predetermined period of time, and generates an arc-extinguishing pulse peak current I between the capacitor 13 and the gate G and cathode K of the GTO element 1.
Supply GR. Also, since the transistor 10 is turned on at the same time as the transistor 3 is turned off, the arc extinguishing power source E
2 to GT via transistor 10 and limiting resistor 11
A current is supplied between the gate G and cathode K of O element 1,
This current is a reverse bias current I that is limited by a limiting resistor 11.
Become GRB.

Note that, among the reverse voltages shown by dotted lines during the OFF period in FIG. 4, VGRM is an avalanche voltage of the gate-cathode junction, which rises after TW1 has elapsed after the start of the turn-off operation and disappears after TW2 has elapsed. VGR is the voltage supplied from the arc-extinguishing power source E2, and VGRB is the gate reverse bias voltage, which is obtained by dividing the voltage of the arc-extinguishing power source E2 by the internal resistance of the GOT element 1 and the limiting resistor 11.

[0006]

[Problem to be Solved by the Invention] Since the conventional drive circuit for the GTO element is configured as described above, if G-K between the gate and cathode of the GTO element 1 is short-circuited, the short-circuit will occur because no detecting means is provided. There was a problem in that the current continued to flow even after this, causing an excessive current to flow and potentially damaging the electrical components due to heat.

The present invention has been made to solve the above-mentioned problems, and is capable of detecting a short-circuit failure between the gate and cathode of a GTO element, and also cuts off the power supply to the drive circuit and prevents thermal breakdown of electrical components. It is an object of the present invention to provide a failure detection circuit for a GTO element that can prevent this.

[0008]

[Means for Solving the Problems] A failure detection circuit for a GTO element according to the present invention provides a fault detection circuit for a GTO element during a turn-off operation of a GTO element.
A detection means for detecting a voltage corresponding to the turn-off current supplied between the gate cathode and a reference value that is larger than the value obtained by converting the current during normal maximum turn-off operation into voltage is compared. GT due to exceeding the standard value
It is equipped with a comparator that considers a short-circuit failure of the O element.

[0009]

[Operation] In the present invention, the turn-off current supplied to the GTO element during the turn-off operation of the GTO element is converted into a voltage and detected, and a comparator performs a comparison operation using this detected voltage and a preset voltage as a comparison voltage. If the absolute value of the detected voltage is larger than this comparison voltage, it is determined that there is a short-circuit failure of the GTO element.

0010

【Example】

Example 1. Hereinafter, one embodiment of the present invention will be described with reference to the drawings. In Figure 1, 1 to 3 and G, K, E1, E
2 is the same as the conventional example shown in FIG. 3, so its explanation will be omitted. 14 is a CT for taking out the current flowing to the capacitor 13, 15 is a diode for making the current taken out by CT14 flow in one direction, 16 is a load resistor for generating a voltage by the current taken out by CT14, and 17 is a load resistor. 16 is a comparator that performs comparison calculations with the comparison voltage VN, SW1 is a switch for turning on and off the ignition power source E1, and SW2 is a switch for turning on and off the arc extinguishing power source E2. be.

Next, the operation will be explained with particular reference to the failure detection operation of the GTO element 1, with reference also to the time chart of FIG. Assume that a so-called element short circuit occurs due to turn-off failure while an off command is input to the command input terminal 2. That is, at the start of the turn-off operation, the value VIGR obtained by converting the extinguishing pulse peak current into a voltage rises steeply, but at this point the turn-off failure occurs and the GTO element 1
If the GTO element 1 is damaged and its gate G and cathode K are also short-circuited, the avalanche voltage VGRM and the subsequent reverse voltages VGR and VGR that occur when the GTO element 1 is healthy
B does not occur.

As a result, the arc extinguishing power source E2 and the capacitor 1
Current supply continues from 3 and VIGR continues to increase. Then, the detected voltage input to the comparator 17 becomes larger than the absolute value of the comparison voltage VN, and the comparator 17 operates to turn off SW1 and SW2 to cut off the power to the drive circuit.

[0013]

[Effects of the Invention] As described above, according to the present invention, the GTO
During arc-extinguishing control of the element, the arc-extinguishing pulse peak current supplied between the gate and cathode is converted into voltage and detected, and this is compared with a predetermined comparison voltage to detect a failure of the GTO element. , the occurrence of a failure in the GTO element can be immediately detected, and the power to the drive circuit can be cut off to prevent thermal destruction of electrical components.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a driving circuit for a GTO element according to an embodiment of the present invention.

FIG. 2 is a time chart during control of the GTO element in FIG. 1;

FIG. 3 is a circuit diagram showing a conventional GTO element drive circuit.

FIG. 4 is a time chart when controlling the GTO element in FIG. 3;

[Explanation of symbols]

1 GTO element 2 Command input terminal 3 Transistor 4 Capacitor 5 Resistance 6 Resistance 7 Tralangista 8 Resistance 10 Transistor 11 Resistance 13 Capacitor 14 CT 14 Diode 16 Load resistance 17 Comparator E1 Ignition power supply E1 Arc extinguishing power supply SW1 Switch SW2 Switch G Gate K Cathode VN Comparison voltage

Claims (1)

[Claims] 1. A detection means for detecting a voltage corresponding to a turn-off current supplied between the gate and the cathode during a turn-off operation of a GTO element, and a detection means for detecting a voltage corresponding to a turn-off current supplied between a gate and a cathode, and a detection means for detecting a voltage corresponding to a turn-off current supplied between a gate and a cathode, and a voltage that is higher than a value obtained by converting the current during a normal maximum turn-off operation into a voltage. A large value is used as a reference value, and when it is compared with the detection voltage and exceeds the reference value, GTO is detected.
A failure detection circuit for a GTO element, comprising a comparator that considers a short-circuit failure of the element.