JPS61254066A - Gate circuit of gate turn-off thyristor - Google Patents

Abstract

PURPOSE:To effectively turn ON a GTO thyristor with a voltage between the anode and the cathode of the thyristor as a power source with an overdrive current of the forward bias current of the thyristor. CONSTITUTION:In order to turn ON a GTO thyristor (GTO) 10, an overdrive current of a forward bias current supplied to the gate of the GTO 10 at interrupting time. Thus, a series circuit of a capacitor 31, a capacitor charging resistor 32 and a diode 34 for stopping the discharge of the capacitor 31 is connected in parallel with the GTO 10, a constant-voltage element 33 for limiting the voltage of the capacitor 31 is connected in parallel with the capacitor 31 to composed an overdrive current supply source 30. Thus, the prescribed rising current change rate can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to a gate circuit that turns on a gate turn-off thyristor.

[Prior art and its problems]

A forward bias current must be applied to a gate turn-off thyristor (hereinafter abbreviated as a GTO thyristor) to turn it on and maintain a conductive state, and a reverse bias current must be applied to turn it off and turn it off. No.

FIG. 3 is a typical gate current waveform diagram required for a GTO thyristor. In FIG. 3, the gate current I applied to the gate of the GTO thyristor.

There is a forward bias current that flows during the forward bias period from time t0 to time t2, and a reverse bias current that flows during the reverse bias period after time t3. It is made conductive and the GTO thyristor is extinguished and cut off by reverse bias current.

By the way, the forward bias current that flows during the overdrive bias period is composed of an overdrive current that flows during a period A from time t0 to time tl, and a long width current that flows during a subsequent period B from time t8 to time t. be done. A period #
The overdrive current in C is for aligning the firing times of many unit GTO thyristors connected in parallel inside the GTO thyristor, and is approximately three times as large as the long-width current in period B. It is normal to supply a current of about 100 mL for several tens of microseconds. For example, in a large-capacity GTO thyristor with a controllable current of 100 OA and an anode-cathode breakdown voltage of about 2500 V, the
If low-temperature operation at degrees Celsius is also considered, the long-width current will be 3A and the overdrive current will be as large as IOA.

FIG. 4 is a circuit diagram showing a conventional example of a gate circuit that supplies the gate current shown in FIG. In this Figure 4,
The forward bias current applied to the gate of the GTO thyristor 10 flows from the forward bias power supply 11 through the resistor 16 and the overdrive transistor 14, or through the resistor 17 and the long width transistor 15. The overdrive transistor 14 is a circuit for supplying an overdrive current, and the resistor 17 and the long-width transistor 15 are a circuit for supplying a long-width current. Further, a reverse bias current is applied to the gate of the GTO thyristor 10 by a reverse bias power supply 21 and a reverse bias transistor 22.

When the resistance value of the resistor 16 in the above-mentioned forward bias current supply circuit is 8□6 and the resistance value of the resistor 17 is R, the ratio of the resistance values of these two resistors is determined by the following equation (1). .

FIG. 5 is a diagram showing the conduction state and gate current waveform of each transistor in the conventional example circuit shown in FIG.
Figure (a) shows the conduction state of the overdrive transistor 14, Figure 5 (0) shows the conduction state of the long width transistor 15, Figure 5 (/→ shows the conduction state of the reverse bias transistor 22, Figure 5) shows the changes in the gate current Io flowing in response to these changes. As is clear from FIG. 5, when both the overdrive transistor 14 and the long-width transistor 15 are made conductive during the period A in which the overdrive current is supplied, the DC power supply 11 is connected to the resistor 16 → the overdrive transistor. 14 and the path from the resistor 17 to the long-width transistor 15, an overdrive current with a negative peak value (see FIG. 5) is supplied to the gate of the GTO thyristor 10.

In a period B in which a long-width current is supplied after time t, the overdrive transistor 14 is cut off and the long-width transistor 15 is made conductive following period A.
TO) Is the current value iB at the gate of transistor 10? jjS
Provides long-width current. Further, in the reverse bias period after time 1, the overdrive transistor 14 and the long width transistor 15 are cut off, and the reverse bias transistor 22 is cut off.
conducts, the reverse bias current increases according to the current change rate determined by the voltage of the reverse bias power supply 21 and the wiring inductance of the gate circuit of the GTO thyristor 10, and when carriers are discharged by this reverse bias current lζ, at that point Since the blocking ability between the anode and cathode and between the gate and cathode of this GTO thyristor 1o is restored, the impedance between the gate and cathode increases. Therefore, the reverse bias current is attenuated to a value corresponding to the leakage current (see FIG. 5).

What is important here is time 1. An extremely large value of 5 to 10 amperes per microsecond is required as the rate of change in current diA/dt at the rise of the overdrive current flowing from the overdrive current. This current change rate A/dt is determined by the voltage v1 of the bias power supply 11, as shown in equation (2) below.
4 collector-emitter voltage V, GTO thyristor 1
Forward voltage drop between gate and cathode of 0 □Lower vG
And if it is almost determined by the wiring inductance Lo of the gate wiring of this GTO thyristor 1o, then 161c
46° j Therefore, the lower limit value of the voltage V of the forward bias power supply 11 is obtained from the above equation (2) as follows. 9. On the other hand, assuming that the loss occurring in the resistor 17 of the circuit that supplies the long-width current is assumed to be true, this value is expressed by equation (4).

・・・・・・・・・・・・・・・ (4) However, v15
is the collector-emitter voltage of the long-width transistor 15, and R□7 is the resistance value of the resistor 17. As is clear from equation (4), the loss of the resistor 17 will be smaller if the voltage V of the forward bias power supply 11 is set to a value as low as possible to allow a long current to flow, and the capacitance of the forward bias power supply 11 will be reduced. However, in a circuit configuration such as the conventional circuit shown in Fig. 4 (the voltage determined by the 3-volt formula is the minimum value, and unless a higher value is selected, the overdrive current rise current Rate of change diA/dt
cannot be set to the desired value. Therefore, the resistor 17 provided in the circuit that supplies the long-width current generates a large loss,
Therefore, there is a drawback that the capacity of the forward bias power supply 11 must also be large.

FIG. 6 is a circuit diagram showing another conventional example of a gate circuit, which attempts to eliminate the above-mentioned drawbacks. That is, in the other conventional circuit shown in FIG. 6, the long-width current portion of the forward bias current supplied to the gate of the GTO thyristor 10 flows through the path of the long-width power supply 13 → resistor 19 → long-width transistor 15. , and the overdrive current is roughly divided into the long width current by overdrive current 12 → resistor 18
→The current flowing through the path of the overdrive transistor 14 is added.

If the circuit configuration shown in Fig. 6 is used, the overdrive power supply 1
The voltage of ζζ is set to be high enough to make the rise change rate of the overdrive current to the desired level, and the voltage of the long-width power supply 13 is set to reduce the loss that occurs in the resistor 19 when a long-width current flows. Since the voltage can be set as low as possible, the drawbacks of the conventional circuit shown in FIG. 4 mentioned above can be eliminated.

However, the other conventional circuit shown in FIG. 6 requires two sets of power supplies that generate different voltages as forward bias power supplies, which has the disadvantage of complicating the circuit.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a gate circuit for a GTO thyristor that can minimize resistance loss in a circuit that supplies a forward bias current to the gate of a GTO thyristor, and can downsize a forward bias current supply power source.

[Key points of the invention]

In this invention, the overdrive current portion of the forward bias current supplied to the gate of the car-shaped GTO thyristor to turn on the GTO thyristor is obtained from the voltage between the anode and cathode when the GTO thyristor is cut off. A series circuit consisting of a capacitor, a charging resistor for charging this capacitor, and a diode for preventing discharge of the capacitor is connected between the anode and cathode of the GTO thyristor, and the voltage of this capacitor is limited. An overdrive current supply circuit is constructed by connecting a constant voltage element in parallel with a capacitor, thereby obtaining the required rate of change in rising current and minimizing the circuit loss of the long-width current supply circuit for the long-width current. The voltage is supplied from a long-width power source with a voltage selected as follows.

[Embodiments of the invention]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.
The content of the present invention will be explained below with reference to figures.

In FIG. 1, the long-width current portion of the bias current for turning on the GTO thyristor 1o and keeping it on is a value iB, and the long-width power supply 13 → resistor 19 → long-width transistor 15 The voltage of this long power supply 13 is set to a value that minimizes circuit loss, so that the power supply capacity is also minimized.

On the other hand, the overdrive current is supplied from the overdrive current supply source circuit 30 via the resistor 18 and the overdrive transistor 14 to the gate of the GTO thyristor 10 superimposed on the above-mentioned long width current. The current supply source circuit 30 includes a capacitor 31, a charging resistor 32, a Zener diode 33 and a diode 34 as constant voltage elements. That is, since the diode 34, the charging resistor 32, and the capacitor 31 are connected in series and connected in parallel to the anode and cathode of the GTO thyristor 10, when the GTO thyristor 10 is in a cut-off state, the voltage between its anode and cathode is As a result, the capacitor 31 is charged.

Here, the charging resistor 32 is for limiting the charging current when charging the capacitor 31, and the diode 34 is for limiting the charging current when charging the capacitor 31.
This is to prevent the charge in the capacitor 31 from discharging through the other GTO thyristor 10 when the GTO thyristor 10 becomes conductive. Furthermore, the Zener diode 33 is used to maintain the voltage of the capacitor 31 at a constant value. Note that 21 is a reverse bias power supply,
Reference numeral 4j22 is a reverse bias transistor, and G
When turning off the TO thyristor 10, these supply a reverse bias current to the gate of the @GTO thyristor 10.

FIG. 2 is an operation waveform diagram of each part in the embodiment circuit shown in FIG. 1, and FIG.
is the anode-cathode voltage v of the GTO thyristor 10
Figure 2 (c) shows the voltage v of the capacitor 31 for a change of 1°.
Each change in O is hailed.

In FIG. 2, since the GTO thyristor lO is in the off state before time t0, the voltage v of the capacitor 31
O is charged to a value v determined by the operating voltage of the Zener diode 33. When the overdrive transistor 4 is made conductive at time t0, the capacitor 31 is used as a power source, and the capacitor 31 → resistor 18 → overdrive transistor 4 → GTO thyristor l
Since an overdrive current with a value of 1 flows in the path from the gate of O to the cathode of the GTO thyristor 10 to the capacitor 31, the voltage value of the capacitor 31 at J falls to vl at the end of the period of 1, that is, at time t. Time 1 when the GTO thyristor 10 turns off again. Until this v
, holds the value. When a reverse bias current is applied to the gate of this GTO thyristor lO and it turns off, the voltage between the anode and cathode rises v0°, so the capacitor 3
1 starts charging again and restores the initial value vo.

As mentioned above, the overdrive current supply circuit 30 is
- between the anode and cathode of the O thyristor 10 #c
! Since this anode-cathode voltage is connected to the power source, it is independent from the long-width power source, and the overdrive current rise change rate "A/dt" can be selected to any value. .

〔Effect of the invention〕

According to the present invention, the overdrive current portion of the forward bias current supplied to the gate of the GTO thyristor is used to ionize the GTO thyristor and maintain its conductive state. As a power supply, it is independent from the power supply for long-width current. Therefore, since the rise rate of change of the overdrive current can be arbitrarily selected to a large value, the GTO thyristor can be turned on quickly and reliably, but the voltage of the power supply that supplies the long width current can be freely selected. ! The gate circuit loss when supplying a long current is minimized, and the capacity of the long power supply is also reduced.
.

Since it can be made small, the device can be made smaller and costs can be reduced.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is an operation waveform diagram of each part in the embodiment circuit shown in FIG. 1IE3 is a waveform diagram of a typical gate current required for a GTO thyristor, FIG. 4 is a circuit diagram showing a conventional example of a gate circuit that supplies the gate current shown in FIG. 3, 11/
Figure X5 is a diagram showing the conduction state of each transistor and the gate current waveform in the conventional circuit shown in Figure 4,
The figure is a circuit diagram showing another conventional example of a gate circuit. DESCRIPTION OF SYMBOLS 10... GTO thyristor, 11... Head bias power supply, 12... Overdrive power supply, 13... Long width power supply, 14... Transistor for overdrive, 15.
・・Long width transistor, 16.17, 18.19・・
・Resistor, 21... Reverse bias power supply, 22... Reverse bias transistor, 30... Overdrive current supply circuit, 31... Capacitor, 32... Charging resistor, 33... Constant voltage Zener diode as an element, 3
4...Figure 1 Figure 3 Figure 4 Cause 1N6 Figure

Claims (1)

[Claims] 1) In a gate circuit that supplies an overdrive current as a forward bias current for turning on a gate turn-off thyristor, and subsequently supplies a long-width current smaller than the overdrive current to the gate of the gate turn-off thyristor. . A gate circuit for a gate turn-off thyristor, wherein the overdrive current is supplied from an overdrive current supply source circuit whose power source is the voltage between the anode and cathode of the gate turn-off thyristor. 2) In the gate circuit according to claim 1,
The overdrive current supply circuit is characterized by comprising a capacitor connected via a diode between the anode and cathode of the gate turn-off thyristor, and a constant voltage element connected in parallel to the capacitor. gate turn-off thyristor gate circuit.