JPH0227633Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention is a self-arc-extinguishing thyristor that conducts the main current and a self-arc-extinguishing thyristor that supplies the gate current of this thyristor. The present invention relates to an improvement in a gate drive circuit for a self-extinguishing thyristor that can suitably supply an on-gate current when the thyristor is turned off.

Generally, the well-known gate turn-off thyristor (GTO thyristor) and static induction thyristor (hereinafter referred to as
When driving a self-extinguishing thyristor, such as the SI thyristor (SI thyristor), it is necessary to pass a forward current through the gate at turn-on and draw a reverse current from the gate at turn-off. In particular, in order to quickly sweep out carriers accumulated inside the self-extinguishing thyristor at turn-off, it is necessary to make the rising speed of the reverse current as fast as possible. Once this accumulated carrier has been swept out, the gate recovers its function of blocking reverse voltage (hereinafter referred to as gate reverse recovery), but the allowable reverse withstand voltage at this time is low, for example, around 15 (V) in a GTO thyristor. It can be said that there is. For this reason, the gate power supply that supplies the gate reverse current is normally used at a voltage below the allowable reverse withstand voltage in consideration of the voltage applied to the gate during gate reverse recovery. The rise speed of the current was only about 30 (A/μs) at most, and the switching time tended to be long when a large current was on or off. Furthermore, SI thyristors are known for their fast switching times. However, in order to turn it off in a short time, it is necessary to draw out the accumulated carriers as quickly as possible, and a gate drive circuit in which the gate reverse current rises quickly is desired.

In view of these points, the applicant has previously proposed
No. 59-172969 ``Gate driving method for self-extinguishing thyristor'' and Japanese Patent Application Laid-Open No. 59-172970 ``Gate driving circuit for electrostatic induction thyristor''. These include a first self-extinguishing thyristor that conducts the main current, a second self-extinguishing thyristor that conducts the gate current of the first self-extinguishing thyristor, and The conduction of the self-arc-extinguishing thyristor and the second self-arc-extinguishing thyristor are operated reciprocally, and the gate voltage at turn-off is switched between when the gate reverse current is being swept out and after the gate junction has reversely recovered. It has characteristics. This will be explained with reference to FIG.

Here, FIG. 1 is a circuit diagram shown to explain the outline of the operating principle of the above-mentioned application filed by the present applicant, and is shown to facilitate understanding of the present invention.

That is, in the drive method in which the two self-extinguishing thyristors (hereinafter simply referred to as thyristors) 1 and 2 shown in FIG. 7 → Thyristor 1 gate → Thyristor 1 cathode → Thyristor 2 cathode → Thyristor 2 gate → DC power supply 4 A closed circuit is formed, forward current is supplied to the gate of thyristor 1, and after the gate junction of thyristor 2 has reverse recovery. Then, the current will flow through the resistor 11. Furthermore, the capacitor 3 is charged by the DC power supply 6 via the resistor 12 with the polarity shown.

Next, when turning off the energized thyristor 1, open the turn-on switch 7 and close the turn-off switch 8, and the following will occur: DC power supply 5 → Thyristor 2 gate → Thyristor 2 cathode → Thyristor 1 cathode → Thyristor 1 gate → Turn-off switch 8 → resistance 10
→A closed circuit of the DC power supply 5 is formed and the thyristor 2 can be turned on. Therefore, the charge stored in the capacitor 3 is discharged through the following path: capacitor 3 -> thyristor 2 anode -> thyristor 2 cathode -> thyristor 1 cathode -> thyristor 1 gate -> capacitor 3, and the accumulated carriers of thyristor 1 are swept out. Here, the resistor 9 is arranged to continue the flow of gate current of the thyristor 2 when the impedance between the cathode and the gate of the thyristor 1 changes to high impedance.

In this way, the device shown in FIG. 1 is equipped with a capacitor 3 in addition to the DC power supply 5 that applies reverse bias to the thyristor 1, and by skillfully switching between these two gate power supplies, the thyristor 2 can be effectively controlled. This is what makes it work. However, in such a device, if a high-power GTO thyristor or the like is adopted as the thyristor 1, the gate forward current required for ignition thereof would require a considerably large value, especially in such a device. Gate current at turn-on requires high gate drive.

As described above, the circuit that supplies forward current to the gate of thyristor 1 includes a path that passes through the gate of thyristor 2 in the reverse direction (from the cathode to the gate). Therefore, the gate forward current of thyristor 1 short-circuits the resistor 11 and becomes a large current until the gate of thyristor 2 reversely recovers, and after the gate of thyristor 2 reversely recovers,
The impedance becomes high between the thyristor 2 (cathode and gate), flows through the resistor 11, and has a small value. That is, the high gate drive value of the gate forward current of thyristor 1 is limited by the value of the reverse recovery charge of the gate of thyristor 2. Usually, an element having a smaller capacitance is selected as the thyristor 2 than the thyristor 1, and therefore the reverse recovery charge is also small, resulting in a decrease in the current value of the high gate drive.

The present invention has been developed by focusing on the above-mentioned points, and provides an exceptional device that utilizes the important gate voltage switching function at turn-off of the previously filed application and can supply a sufficient gate forward current at turn-on. It is something to do. Hereinafter, the present invention will be explained using embodiment drawings similar to FIG.

FIG. 2 shows the main structure of an embodiment of the present invention, in which 13, 14 and 15 are capacitors, 16 is a diode, 17 and 18 are field effect transistors (FET), and 19 is a resistor. In the figure, the same reference numerals as in FIG. 1 indicate parts having the same function. Here, detailed explanations of the same components as those shown in FIG. 1 will be omitted, but the points that are constructed to improve the apparatus shown in FIG. 1 and their functions are as follows.

Now, in FIG. 2, when igniting the thyristor 1, the FET 17 is first turned on by an on control signal (not shown). However, in this case, FET
It is assumed that 18 is also turned off by an off control signal (not shown).

At this time, the electric charge of the capacitor 14 charged by the DC power supply 4 is as follows: thyristor 1 gate → thyristor 1 cathode →
Thyristor 2 cathode → Thyristor 2 gate →
It flows through diode 16 → FET 17 and can supply forward current to the gate of thyristor 1. Next, even if the gate junction of thyristor 2 reversely recovers and becomes high impedance between the (cathode and gate) of thyristor 2, (resistance 1
Since the charging current of the capacitor 13 flows through the series circuit of 9 → capacitor 13), this resistor 1
By selecting a small value of 9, the high gate drive current value required to fire the thyristor 1 can be sufficiently satisfied. Next, when the charging voltage of the capacitor 13 increases and the diode 16 is forward biased, the current flows through (the resistor 11 to the diode 16), and from then on, the current limited by the resistor 11 continues to flow throughout the ON period. Become.

Then, in order to turn off the thyristor 1 which is in the conductive state, the FET 18 is turned on by, for example, the above-mentioned off control signal, and the FET 17 is turned off by the on control signal. At this time, the electric charge of the capacitor 15 charged by the DC power supply 5 is first transferred from the diode 16 → capacitor 13 → resistor 19 →
Thyristor 1 cathode → Thyristor 1 gate →
It flows through the FET 18, discharging the charge in the capacitor 13, and flushing out the accumulated carrier in the thyristor 1. Further, as the discharge of the capacitor 13 progresses, the cathode potential of the thyristor 2 decreases, and the gate of the thyristor 2 is forward biased. Therefore, the current flows through the path of capacitor 15 → thyristor 2 gate → thyristor 2 cathode → thyristor 1 cathode → thyristor 1 gate → FET 18 → capacitor 15, and thyristor 2 is fired.
Then, when the thyristor 2 fires, the DC power supply 6
Capacitor 3 charged via resistor 12 by
The charge is discharged via the following: capacitor 3 → thyristor 2 anode → thyristor 2 cathode → thyristor 1 cathode → thyristor 1 gate → capacitor 3, and the accumulated carrier of thyristor 1 is quickly swept away. Note that when the gate junction of the thyristor 1 reversely recovers, the impedance between the gate and the cathode increases, and its value is determined by the resistor 9 connected in parallel to the thyristor 1. Further, the voltage generated across the resistor 9 at this time is approximately regulated by the voltage of the DC power supply 5. Therefore, even if the voltage of the DC power source 6 is selected to be larger than the allowable gate reverse voltage of the thyristor 1, if the voltage of the DC power source 5 is selected to be less than the above-mentioned allowable gate reverse voltage, after the gate junction of the thyristor 1 as described above reversely recovers. The voltage of the DC power supply 6 that exceeds the voltage of the DC power supply 5 is automatically shared by the thyristor 2, which is very convenient.

As explained above, according to the present invention, the main current supply thyristor and the gate current supply thyristor are operated in opposition, and the gate power supply can be switched at turn-off, and the gate forward current can be sufficiently supplemented at turn-on. Moreover, an extremely useful device can be provided.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram for explaining a previous application by the present applicant, shown to facilitate understanding of the present invention;
FIG. 2 is a circuit diagram showing the main part of an embodiment of the present invention. 1, 2...Self-extinguishing thyristor (thyristor),
3, 13, 14, 15...Capacitor, 4, 5, 6
...DC power supply, 9, 11, 12, 19...Resistance, 16
...diode, 17,18...field effect transistor (FET).

Claims (1)

[Scope of utility model registration request] Connecting the cathode terminal of a first self-arc-extinguishing thyristor that conducts the main current and the cathode terminal of a second self-arc-extinguishing thyristor that conducts the gate current of the first self-arc-extinguishing thyristor; ,
a first capacitor having a charging function is connected between the anode terminal of the second self-extinguishing thyristor and the gate terminal of the first self-extinguishing thyristor;
a first switching element that forward biases the gate of the second self-arc-extinguishing thyristor when electrical conduction occurs between the gate terminal of the first self-arc-extinguishing thyristor and the gate terminal of the second self-arc-extinguishing thyristor; and a second capacitor having a charging function, a third capacitor having a charging function is connected to the gate terminal of the first self-extinguishing thyristor, and the first self-extinguishing thyristor when conductive. A first series connection body consisting of a second switching element for forward biasing the gate of the thyristor is disposed, and a second series connection body consisting of a resistor and a capacitor is connected to the cathode terminal of the first self-extinguishing thyristor.
the first series connection body and the second series connection body are arranged in series, and the first series connection body and the second series connection body are connected in series, and the second series connection body is connected in series.
The cathode side of a diode whose anode side is connected to the gate terminal of the self-arc-extinguishing thyristor is connected to the connection point of the first series-connected body and the second series-connected body, A gate drive circuit for a self-arc-extinguishing thyristor configured to connect a resistor between the gate terminal and the cathode terminal of the second self-arc-extinguishing thyristor and between the gate terminal and the cathode terminal of the second self-arc-extinguishing thyristor.