JPH07321624A - Gate circuit for self-arc-extinction type semiconductor element - Google Patents

Abstract

PURPOSE:To improve the reliability of the circuit by providing plural electrolytic capacitors in parallel with the gate circuit to monitor the discharge current of each capacitor thereby detecting a capacitor whose capacitance is lost indirectly and avoiding a sudden failure in turn-off. CONSTITUTION:In the gate circuit comprising a self-arc-extinction semiconductor element 1, when the gate circuit is in turn-off operation at a current less than a maximum interrupting current and any capacitor 3 whose capacitance is lost or opened is in existence in the capacitor group, a current of the capacitor 3 detected by current transformers 6a-6n is smaller than the current of the other normal capacitors 3. Since no signal is outputted from a comparator 7 receiving the current of the capacitor 3 whose capacitance is lost, a discrimination device 8 discriminates the defective capacitor. The discrimination device 8 makes discrimination while ranking faulty states depending on output states of plural comparators 7. Thus, the processing for issuing alarm and for conducting protection is ensured for the gate circuit in this way.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gate circuit of a self-arc-extinguishing semiconductor element, and more particularly to a gate circuit of a self-arc-extinguishing semiconductor element for supplying a large steep gate current.

[0002]

2. Description of the Related Art Gate turn-off thyristors (hereinafter referred to as G
Self-extinguishing type semiconductor devices such as TO (abbreviated as TO) and electrostatic induction thyristors (hereinafter abbreviated as SIT) are connected between their control poles (gates) and cathodes (cathodes) in order to turn them on or off at high speed. It is necessary to flow a relatively large gate current with a sharp rise. As a method of obtaining a large current with a sharp rise, a method of discharging the stored charge of the capacitor is generally used. G
The off-gate current for turning off the TO and SIT is very important, and the insufficient off-gate current causes damage to the device.

FIG. 4 shows an example of a circuit for supplying an off-gate current of the GTO. Charge of the capacitor 3 charged by the power supply 2 is turned on to the GTO 1 by turning on the switching element 4. Is configured to supply. Further, there is a relationship between the gate current I _{G of the} GTO 1 and the voltage V _GK between the gate and the cathode as shown in the characteristic diagram of FIG. 5 when the turn-off is completed, and the accumulated charge inside the GTO is discharged by the off-gate current. Then, the Zener voltage characteristic of the gate-cathode voltage on the negative side is restored, and the turn-off is completed.

Normally, in the gate circuit of FIG.
It is rational to set the voltage of 1 to a value that matches the gate-cathode Zener voltage of the GTO. By selecting in this way, the off-gate current after current interruption can be quickly reduced to zero, and the gate power supply capacity can be optimized. However, the capacitor in the gate circuit for discharging the accumulated charge of the large-capacity GTO needs to have a capacity of several thousand to several tens of thousands μF, and in general, an electrolytic capacitor is often used, and one capacitor is sufficient. If it is not possible, multiple electrolytic capacitors are often used in parallel. However, it is known that the electrolytic capacitor causes capacity loss or open failure due to aging.

[0005]

By the way, there has been proposed a method of monitoring and protecting the off-gate current and off-gate voltage of the GTO in order to prevent the failure of turn-off failure of the GTO (see Japanese Patent Application No. 11198662). . Figure 6
Shows the relationship between the anode current and the off-gate current when the off-gate voltage is equal to the Zener voltage between the gate and the cathode. The off-gate current is the dotted line I _RG (solid line I _RGM is the case where the GTO rated current is cut off). ), When the current I _T below the rated current is cut off, only the current determined by the turn-off gain flows, and the rated current I _T
It is smaller than when _TM is shut off. The increase rate di / dt of the off-gate current is determined by the off-gate voltage E and the stray inductance L of the gate circuit, and the maximum off-gate current I _RGmax is determined by the following formula.

After the anode current is cut off, the off-gate current hardly flows due to the Zener characteristics between the gate and the cathode. Therefore, there is a problem with the capacitor in the off-gate circuit, and even if the cut-off capability is deteriorated, the off-gate current and voltage cannot be monitored. I can't judge.

If an attempt is made to cut off a large current in a state where the turn-off capability is deteriorated due to the loss or opening of the capacitance of the capacitor, the GT will fail due to the turn-off failure.
This is a problem because it will damage O. In the case of GTO application device, even if the turn-off capability is lowered,
It may be required to detect this and give an alarm to avoid sudden shutdown of the device.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a self-arc-extinguishing semiconductor capable of monitoring supply of a necessary and sufficient gate current to a self-arc-extinguishing semiconductor element. It is to provide a gate circuit for the device.

[0009]

In order to achieve the above-mentioned object, the present invention provides a self-extinguishing semiconductor device having a plurality of capacitors for supplying a pulsed off-gate current. In a gate circuit of a self-arc-extinguishing type semiconductor device, a current transformer for detecting a discharge current of each of the capacitors, and a determination means having a function of detecting a decrease in off-gate capability by an output signal of the current transformer are provided. It is characterized by that.

According to a second aspect of the present invention, in a gate circuit of a self-extinguishing semiconductor device, which is provided with a plurality of capacitors for supplying a pulsed off-gate current to the self-extinguishing semiconductor device, a discharge current of the plurality of capacitors is detected. And a determination having a function of detecting a decrease in off-gate capability by detecting the voltage across the resistors by connecting the current transformers for each 2n to the resistors in reverse polarity to each other. It is characterized by having means.

According to a third aspect of the present invention, in a gate circuit of a self-extinguishing semiconductor device having a plurality of capacitors for supplying a pulsed off-gate current to the self-extinguishing semiconductor device, the discharge current of each capacitor is detected. A current transformer for
It is characterized by further comprising a determination means having a function of comparing the current of each of the capacitors and an average value obtained by dividing the off-gate current by the number of capacitors to detect a decrease in off-gate capability.

[0012]

When the gate circuit of the present invention is configured as described above, when the capacitor in the gate circuit has a capacity loss or an open failure, a decrease in turn-off capability is promptly detected to prevent failure of GTO turn-off failure. It is possible to provide a protection function.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit configuration diagram of one embodiment of the present invention (corresponding to claim 1). As shown in FIG. 1, the gate circuit of this embodiment includes a self-arc-extinguishing semiconductor element 1, a power supply 2 , A capacitor group including a plurality of capacitors 3, a switching element 4, an on-gate resistor 5, current transformers 6a to 6n provided for each capacitor, and signals from the current transformers 6a to 6n have a predetermined level. A comparator 7 that outputs a signal when it exceeds
It is composed of a judging device 8 for judging an abnormality according to the output state of the comparator 7.

In the gate circuit of the self-arc-extinguishing type semiconductor device configured as described above, for example, when a current less than the controllable on-current (maximum cut-off current) of the GTO is turned off, a capacitance drop or open may occur in the capacitor group. When the generated capacitor 3 exists, the current values of the capacitors detected by the current transformers 6a to 6n are smaller than the current values of other normal capacitors. Therefore, no signal is output from the comparator 7 to which the current value of the capacitor is input, and the determiner 8 can determine whether or not the capacitor is defective. The determiner 8 can rank and determine the abnormal state according to the output states of the plurality of comparators 7.

FIG. 2 is a circuit configuration diagram of another embodiment of the present invention (corresponding to claim 2), and the same reference numerals as those in FIG. 1 represent the same elements, and the description thereof will be omitted. In this embodiment, the outputs of the current transformers, which detect the currents of a plurality of capacitors, are connected to one resistor 9 with at least 2n units having opposite polarities, and are compared when the voltage generated at the resistor 9 exceeds a predetermined level. The signal is output from the device 7 and input to the determiner 8. With the above configuration, when a capacitance change occurs in one of the capacitors in units of two, the voltage generated in the resistor 9 of the set rises, and the determiner 8 that outputs a signal from the comparator 7 exceeding a preset value is It is possible to judge the abnormality by this signal and perform the protection operation. According to the present embodiment, the number of comparators 7 is small and the structure is simple.

FIG. 3 is a circuit configuration diagram of still another embodiment of the present invention (corresponding to claim 3). Since the same reference numerals as those in FIG. 1 represent the same elements, the description thereof will be omitted. In this embodiment, a current transformer 61 for detecting an off-gate current and an average calculator 10 are additionally set in the constituent elements shown in FIG. From the off-gate current detected by the average calculator 10, an average value when the currents of the capacitors uniformly flow is calculated, and the actual currents of the capacitors are compared by the comparator 7 to cause a difference of a predetermined value or more. Then, a signal is output and input to the determiner 8. According to the present embodiment, it is possible to monitor the off-gate current in the entire range of anode currents regardless of the magnitude of the cut-off anode current.

Since the current transformer 61 can be constructed in a very small size for pulse current, it does not become so large in terms of circuit and is inexpensive. In each of the above-described embodiments, the capacitance decrease of the capacitor is indirectly detected by the discharge current, but the same effect can be obtained by the method of detecting the capacitance decrease of the capacitor by means other than the current transformer.

[0018]

As described above, according to the present invention,
When a plurality of electrolytic capacitors are provided in parallel in the gate circuit of the self-extinguishing type semiconductor device, the discharge current of each capacitor is monitored and the drop in the capacity is indirectly detected by detecting the decrease in the turn-off capability, Since the alarm or protection operation can be performed, it is possible to provide a highly reliable gate circuit of a self-arc-extinguishing semiconductor device capable of preventing sudden turn-off failure.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of an embodiment of the present invention.

FIG. 2 is a circuit configuration diagram of another embodiment of the present invention.

FIG. 3 is a circuit configuration diagram of still another embodiment of the present invention.

FIG. 4 is a conventional gate circuit configuration diagram to which the present invention is applied.

FIG. 5 is a characteristic diagram showing gate-cathode characteristics of GTO.

FIG. 6 is a diagram showing an off-gate current when the GTO current is cut off.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Self-arc-extinguishing type semiconductor element, 2 ... Power supply, 3 ... Capacitor group, 4 ... Switching element, 5 ... On-gate resistance, 6a
6n, 61 ... Current transformer, 7 ... Comparator, 8 ... Judgment device, 9 ...
Resistance, 10 ... Average calculator.

Claims (3)

[Claims] 1. A gate circuit for a self-arc-extinguishing semiconductor device, comprising a plurality of capacitors for supplying a pulsed off-gate current to the self-extinguishing semiconductor device, and a change circuit for detecting a discharge current of each capacitor. A gate circuit for a self-arc-extinguishing semiconductor device, comprising: a current transformer; and a determination unit having a function of detecting a decrease in off-gate capability based on an output signal of the current transformer. 2. A gate circuit for a self-arc-extinguishing semiconductor device, comprising a plurality of capacitors for supplying a pulsed off-gate current to the self-extinguishing semiconductor device, for detecting a discharge current of the capacitors. A current transformer and a determination unit having a function of detecting a decrease in off-gate capability by detecting a voltage across the resistor by connecting the current transformers every 2n to a resistor with opposite polarities. A gate circuit of a self-extinguishing type semiconductor device characterized by the above. 3. A gate circuit for a self-arc-extinguishing semiconductor device, comprising a plurality of capacitors for supplying a pulsed off-gate current to the self-extinguishing semiconductor device, and a change circuit for detecting a discharge current of each capacitor. Self-extinguishing type semiconductor having a function of detecting a reduction in off-gate capability by comparing a current of each capacitor and an average value obtained by dividing the off-gate current by the number of capacitors. Device gate circuit.