JPS61293155A - Gate driving circuit for gate turn-off thyristor - Google Patents

Abstract

PURPOSE:To simplify the organization of a driving circuit, by feeding OFF-gate current and backward bias voltage to a GTO thyristor with a set of a DC power source and a switching element. CONSTITUTION:When a semiconductor switch 2 is closed at the time of zero hour, then the primary side current I1 and the secondary side current I2 of the I1 multiplied by (a), namely, the OFF-gate current of a GTO thyristor 7 get to flow to be increased, and after that, when the connection between the cathodes of the GTO thyristor 7 is counter-recovered, then the both current I1 and I2 get to be reduced. After that, the secondary side current I2 comes to zero, and the primary side current I1 comes to a constant value, and by the constant current, backward bias voltage is applied between the gate cathodes of the GTO thyristor 7. As the result, OFF-gate current and backward bias voltage can be fed through the same DC power source.

Description

[Detailed description of the invention] [Technical field to which the invention pertains] This invention relates to a gate turn-off thyristor that supplies an off-gate current that turns off the gate turn-off thyristor and a reverse bias voltage when the gate turn-off thyristor is turned off. This invention relates to a gate drive circuit.

[Prior art and its problems]

In order to make a gate turn-off thyristor (hereinafter abbreviated as GTO thyristor) conductive, an on-gate current is supplied to the gate of the GTO thyristor, and in order to turn off a conductive GTO thyristor, an off-gate current is also supplied to the gate. There is a need to.

FIG. 7 is a circuit diagram showing a conventional example of a gate drive circuit that supplies an off-gate current to a GTO thyristor, and when it is desired to turn off the conductive GTO thyristor 7,
The semiconductor switch 32 is turned on to supply an off-gate current from the DC power supply 31 through the transformer 33 and diode 34 between the cathode and gate of the GTO thyristor 7. However, in such a circuit, since the transformer 33 is present between the DC power supply 31 that supplies the off-gate current and the GTO thyristor 7, when the GTO thyristor 7 is in the off state, the voltage between the cathode and the gate is It is not possible to supply a reverse bias voltage from this DC power supply 31 to. Therefore, conventionally, as shown in FIG. 7, a separate DC power supply 35 is prepared, and the reverse bias voltage is applied to the GTO thyristor 7 by turning on another semiconductor switch 36 at an appropriate timing.
We are trying to supply it to

In other words, the conventional gate drive circuit that supplies the off-gate current to the GTO thyristor 7 does not require two sets of DC power supplies and two sets of semiconductor switches, but also requires a control circuit that operates the bidirectional conductor switches at appropriate timing. Therefore, the circuit becomes complicated and expensive.
It is an object of the present invention to provide a gate drive circuit for a GTO Zyristor that can supply an off-gate current and a reverse bias voltage to the Syristor.

[Key points of the invention]

This invention combines the DC power supply and the cathode of the GTO Zyristor.
An autotransformer is installed between the GTO thyristor and the GTO thyristor, and the off-gate current to the GTO thyristor is supplied to the transformer action of the autotransformer, and also between the primary and secondary sides of the autotransformer. Taking advantage of the fact that there is no insulation between the GTO zyristor and the other side, the reverse bias voltage between the cathode and the gate when the GTO zyristor is off is determined by the DC voltage applied from the DC power supply through the autotransformer. This is what we are trying to supply.

[Embodiments of the invention]

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

In FIG. 1, a DC power supply 1 includes a semiconductor switch 2 as a switching element, an autotransformer 8, and diodes 9 and 10.
, a capacitor 11 are connected in a circular fashion as shown in the figure, a resistor 12 is connected in parallel to the diode 9, and a diode 1 is connected in parallel to the diode 9.
A resistor 13 is connected in parallel to the series circuit of 0 and the capacitor 11, respectively. In addition, 1 of the above-mentioned autotransformer 8
When the number of turns on the secondary side is R2, the intermediate tap whose number of turns on the secondary side is R2 is coupled to the cathode of the GTO thyristor 7,
The gate of GTO thyristor 7 with diodes 9 and 10
connected to the connection point.

When the GTO thyristor 7 is currently in the on state, the time T
When the semiconductor switch 2 is closed at the instant of =O, the diodes 9 and 10 are turned on, and the primary current of the autotransformer 8 and the secondary current 2 begin to flow.

The voltage of DC power supply 1 is E, and the capacitance of capacitor 11 is C.
1, the resistance value of the resistor 12 is R1, and the resistance value of the resistor 13 is R2, and if the resistance value R2 is a sufficiently large value, the primary side current ■
1 all flows to the capacitor 11, and the excitation current of the autotransformer 8 can be ignored.The primary current 11 and the secondary current 2 of the autotransformer 8 are as follows. 0, which can be approximated by equations (1) and (2). However, L is the leakage inductance on the primary and secondary sides of the autotransformer 8.
It is the equivalent composite inductance when viewed from the next side,
a is the ratio between the number of turns n1 on the primary side and the number n2 on the secondary side of the autotransformer 80, and is 0 (i.e., a = = n1
/n,) Therefore, the current flowing through the diode 9■. is (3)
It is shown by the formula.

Ip=I2 11 = (al)・11...
・・・・・・・・・・・・・・・・・・・・・・・・(
3) Assume that the gate-to-cando junction of the GTO thyristor 7 reversely recovers and generates a constant voltage V at time Ta after a certain period of time has elapsed due to the off-gate current of the secondary current generator 2 mentioned above. , the primary current 11 and the secondary current 2 after this time Ta are expressed by the following equations (4) and (5).

However, the time Ta satisfies the following equation (6), and the turns ratio a between the primary and secondary sides of the autotransformer 8 and the voltage E of the DC power supply 1 satisfy the following equation (7). Make a selection that satisfies you.

E-a-VC≦0 ・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・・・・・・・
(7) When E and a have the relationship shown in equation (7), the coefficient of the sine (s in) on the right side of equation (4) above becomes zero or negative. Furthermore, since the coefficient of the cosine (cos) of the second term on the right side is positive, the primary current flow rate 1 begins to decrease after time Ta. This also applies to equation (6), so the secondary current flow rate 2 is likely to decrease after time Ta.

The above-mentioned phenomenon occurs when the resistance value R1 of the resistor 12 is extremely small and the excitation current of the autotransformer 8 can be ignored, but in reality there is a component of the excitation current flowing through the resistor 12, so the primary The side current Il does not become zero. Moreover, since this primary side electrician finally becomes a direct current, the influence of the transformer action of this primary side electrician 1 on the secondary side of the autotransformer 80 disappears. Therefore, the primary current 11 tends to be a certain constant value, while the secondary current 2 tends to become zero, so the current flow through the diode 9. becomes zero when it reaches 2-11, and this switching diode 9 is turned off. Also, since the discharge of the capacitor 1 is prevented by the diode 10,
The primary current factor 1 never becomes negative, and ultimately takes the value shown in equation (8) below.

11= 11d =□・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・・・・・・・
(8) R1+R2 The gate and cathode of the GTO thyristor are reverse biased by the voltage vd generated in the resistor 12 due to the primary current (1) shown in equation (8). This voltage vd is expressed by the following equation (9).

FIG. 2 is a circuit diagram showing a second embodiment of the present invention,
The DC power supply 1, semiconductor switch 2, and G shown in FIG.
TO thyristor 7, autotransformer 8, diodes 9 and 10
, the names, uses, and functions of capacitor 11 and resistors 12 and 13 are all the same as in the case of Fig. 1 mentioned above.The difference from Fig. 1 is that resistor 12 is connected in parallel to the gate and cathode of GTO thyristor 7. 2, the explanation of FIG. 2 will be omitted.

FIG. 3 is a graph showing changes in current and voltage in the example circuit shown in FIG. 1 or FIG.
3 (b) shows the change in the secondary current 2 of the autotransformer 8, and FIG. Each one detects the change in voltage.

In FIG. 3, when the semiconductor switch 2 is closed at time zero, the primary current A and the secondary current A are multiplied by a times F1. That is, the off-gate current of the GTO thyristor 7 begins to flow while increasing, and when the gate-cathode junction of the GTO thyristor 7 reversely recovers at time Ta, the bichamber flow 1
1 and I2 both begin to decrease.

At the time of frost, the secondary current ■2 is zero, and the primary current □ is a constant value Ixd. Due to this Ild, there is a reverse bias voltage vd between the gate and cathode of GTO Cyrisk 7 as shown in equation (9). will be given.

FIG. 4 is a circuit diagram showing a third embodiment of the present invention,
In the third embodiment shown in FIG. 4, the number of turns on the primary side is n3.
An autotransformer 18 whose intermediate terminal is connected to the negative pole side of the DC power supply 1 through a series circuit of a diode 14 and a capacitor 15, and a diode 16 connected in series with the resistor 13 The first thing mentioned above is that
The names, uses, and functions of the DC power supply 1, semiconductor switch 2, GTO thyristor 7, diodes 9 and 10, capacitor 11, and resistors 12 and 13, which are different from the embodiment shown in the figure, are as shown in FIG. Since these are the same as in the case, their explanation will be omitted.

In the third embodiment shown in FIG. 4, the intermediate terminal of the autotransformer 18 is connected to the negative electrode side via the diode 14 and the capacitor 15, so that the intermediate terminal of the autotransformer 18 is Resonant current ■3, which is approximately determined by the leakage inductance value of the part with the number of turns n3 and the capacitance of the capacitor 15, flows through the capacitor 15, and by multiplying this by n3/n2, the resulting current is expressed by equation (2). Therefore, by appropriately selecting the number of turns n3 to the intermediate terminal of the autotransformer 18 and the capacitance of the capacitor 15, the current after the semiconductor switch 2 is closed is It is possible to make the rise of the secondary current I2 larger than in the embodiment shown in FIG.

Note that the diode 14 is only for preventing the discharge of the capacitor 15, and the diode 16 connected in series with the resistor 13 is connected to the resistor 1 when the diode 14 is on.
This is to prevent overvoltage from being applied to 3.

FIG. 5 is a graph showing changes in current and voltage in the third embodiment circuit shown in FIG. 4, and FIG. Figure 5←) shows the resonant current taken out from the intermediate terminal of the autotransformer 18■3
Similarly, FIG. 5(c) shows the change in the secondary current I2 of the autotransformer 18, and FIG. 5(c) shows the change in the voltage across the resistor 12.

As is clear from FIG. 5, when the semiconductor switch 2 closes at time zero, the resonant current ■3 increases rapidly and reaches time T.
The peak value is reached at c, but due to this resonant current, the rise of the secondary current I2 of the autotransformer 18 also becomes rapid, allowing the GTO thyristor 7 to be turned off more quickly. . The other parts of the graph shown in FIG. 5 are the same as the graph shown in FIG. 3 described above, and therefore the explanation of those parts will be omitted.

FIG. 6 is a circuit diagram showing a fourth embodiment of the present invention,
This is a circuit in which a resistor 21 and semiconductor switches 22 and 23 are added to the circuit of the embodiment shown in FIG.
TO thyristor 7, autotransformer 8, diodes 9 and 10
, capacitor 11, and resistors 12 and 13 are the same as in FIG. 1, so their explanation will be omitted.

The fourth embodiment shown in FIG. 6 is a GTO thyristor 7.
The positive charge accumulated in the capacitor 11 when supplying the off-gate current to the GTO thyristor 7 is intended to be used as the on-gate current when turning on the GTO thyristor 7. In other words, when closing the semiconductor switch 2 to turn off the conductive GTO thyristor 7, the semiconductor switches 22 and 23 are kept in the off state, so an off-gate current flows through the GTO thyristor and turns it off. I have already mentioned this. Therefore, when the GTO thyristor 7 is in the off state and reverse bias voltage is supplied from the DC power supply, if the semiconductor switch 2 is opened and the semiconductor switches 22 and 23 are closed, the capacitor 11 is Charges accumulated in polarity are transferred from capacitor 11 → resistor 21 → semiconductor switch 22 →
This discharge current, that is, the on-gate current, is discharged along the path of the gate of the GTO thyristor 7 → the cand of the GTO thyristor 7 → the semiconductor switch 23 → the capacitor 11, and the GTO thyristor 7 is turned on. With the addition of a few components, the energy stored in the capacitor 11 can be used effectively.

〔Effect of the invention〕

According to this invention, an autotransformer is provided between the cathode and gate of the GTO thyristor and the DC power supply, and an off-gate current is supplied to the GTO thyristor by utilizing the transformer action of the autotransformer. , when the GTO thyristor is off, the gate canad is connected from the DC power source through the autotransformer by taking advantage of the fact that the primary and secondary sides of the autotransformer are not insulated. Since the off-gate current and reverse bias voltage can be supplied from the same DC power supply, it is possible to reduce the number of DC power supplies and switching elements that open and close them, and also to There is no need for a control circuit for controlling the operation timing of the switch elements, which has the advantage of simplifying the circuit and reducing costs. Furthermore, by adding a few components, the energy stored in the capacitor when supplying the off-gate current can be used as the on-gate current when turning on the GTO thyristor, reducing the amount of energy used in the gate drive circuit, and reducing the amount of energy used in the on-gate drive circuit. It also has the advantage of being simplified.

[Brief Description of the Drawings] Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2 is a circuit diagram showing a second embodiment of the invention, and Fig. 3 is a circuit diagram showing a second embodiment of the invention. 2 is a graph showing changes in current, frost, and pressure in the example circuit shown in FIG. 2. FIG. FIG. 4 is a circuit diagram showing a third embodiment of the present invention, FIG. 5 is a graph showing changes in current and voltage in the third embodiment circuit shown in FIG. 4, and FIG. FIG. 7 is a circuit diagram showing a fourth embodiment of the invention. FIG. 7 is a circuit diagram showing an embodiment of a gate drive circuit that supplies an off-gate current to the GTO Cyrisk. 1...DC power supply, 2...Semiconductor switch as a switching element, 7...GTO thyristor, 8.18...Auto transformer, 9, 10,1
4.16...Diode, 11.15...
...Capacitor, 12,13.21...Resistor, 22.23...Semiconductor switch. Figure 3 1-μ

Claims (1)

[Claims] 1) In a circuit that supplies between the gate and cathode of a gate turn-off thyristor an off-gate current that turns off the gate turn-off thyristor and a reverse bias voltage when the gate turn-off thyristor is turned off, one of two diodes whose anodes are connected to each other. Connecting the positive pole side of the DC power supply to the cathode of the first diode through a series circuit of an autotransformer and a switch element, and connecting the negative pole side of the DC power supply to the cathode of the second diode through a capacitor, means for connecting a center tap of the autotransformer to a cathode of the gate turn-off thyristor, connecting a junction between the two diodes and a gate of the gate turn-off thyristor, and bypassing the current flowing through the first diode; A gate drive circuit for a gate turn-off thyristor, comprising means for bypassing a current flowing through a series circuit of a second diode and a capacitor.