JPS61244261A - Gate circuit of gate turn off thyristor - Google Patents

Abstract

PURPOSE:To prevent the up grade of ON-gate current from being lowered, by providing a switch element in reverse parallel with a reflux diode, and by turning the element ON for a short time on ON-gate current flow start. CONSTITUTION:An ON-gate circuit feeding ON-gate current to the gate of a GTO thyristor 15 is organized with an ON-gate power source 1, ON-gate transistor 5, and the like. An OFF-gate circuit is organized with an OFF-gate power source 2, OFF-gate transistor 6, reflux diode 8, pulse transformer 14 and the like, and a transistor 16 for reverse voltage is provided in reverse parallel with the reflux diode 8. When the GTO thyristor 15 in an OFF-state is turned On, then the transistor 16 for reverse voltage is turned ON at the same time when the ON-gate transistor 5 is ON. As the result, an OFF-gate condenser 4 is discharged, and voltage in the directions of arrow heads is induced to the pulse transformer 14, and current from the ON-gate circuit is in all applied to gates, and the GTO thyristor 15 is exactly turned OFF.

Description

[Detailed description of the invention] [Technical field to which the invention pertains] This invention relates to an off-gate circuit that supplies an off-gate current from the secondary winding of a pulse transformer to the gate of a gate turn-off thyristor, and The present invention relates to a gate circuit of a gate turn-off thyristor in which an on-gate circuit that supplies an on-gate current is connected in parallel with each other.

[Prior art and its problems]

FIG. 2 is a circuit diagram showing a conventional example of a gate circuit of a gate turn-off thyristor. In this figure 782, on-gate power supply 1, on-gate capacitor t3. An on-gate transistor 5 as an on-gate switching element, a resistor 11, and a speed sensor.

The on-gate circuit consisting of the on-gate capacitor 13 is connected between the gate and cathode of the gate turn-off thyristor (hereinafter referred to as GTO (abbreviated as risk) 15), so when the on-gate transistor 5 is turned on, the on-gate capacitor 3 is charged to the polarity shown, so the gate of GTO thyristor 15 → GTO thyristor 15
On-gate current to the cathode of 1. flows and turns on this GTO thyristor 15.

Here resistors 11, 12 and speed-up capacitor 1
3 is a so-called overdrive circuit for quickly turning on the GTO thyristor 15. That is, when the on-gate transistor 5 is in the off state,
Since the speedup capacitor 13 is short-circuited with the resistors 1 and 12, its charge is zero. At this time, when the on-gate transistor 5 is turned on, the differential circuit is formed by the resistor 11 and the speedup capacitor 13. To compose! A so-called overdrive current with a steep upward flow flows,
After that, when the speed-up capacitor 13 is charged, a steady current is determined by the resistance value.

The off-gate circuit includes an off-gate power supply 2) an off-gate capacitor 4, an off-gate transistor 6 as an off-gate switching element, a diode 7, a freewheeling diode 8. It is composed of a pulse transformer 14. The pulse transformer 14 includes a primary winding 14A, a secondary winding 14B, and a reset winding 14C, and the polarities of these three windings are as shown in the figure. It is connected in series with the line 14C, and the Y point is the connection point. In such an off-gate circuit, the off-gate capacitor 4 is charged to the polarity shown by the off-gate power supply 2 via the diode 7, so when the off-gate transistor 6 is turned on, the off-gate capacitor 4 → point Y → primary winding M14A → Off-gate transistor 6 → Off-gate capacitor 40 A capacitor discharge current flows through the circuit. This discharge current is amplified by the pulse transformer 14, and the secondary winding M
14B → Parallel diode 10 → GTO thyristor 15
Since the off-gate current flows through the path from the cathode of the GTO thyristor 15 to the gate of the GTO thyristor 15 and the secondary winding 14B, this GT
O-thyristor 15 will be turned off.

Here, the role of the reset winding a14c of the pulse transformer 14 is as follows. That is, even when the off-gate transistor 6 is turned from on to off in order to reduce the off-gate current to zero, the excitation current continues to flow through the primary winding 14A. Therefore, the potential of the terminal on the opposite side of the reset winding 14C from the Y point decreases, and the freewheeling diode 8 becomes conductive.
Reset, G winding 14C-+Y point → off gate capacitor 4
→Freewheeling diode 8→Reset, and because current flows through the path of winding 14C, the exciting current becomes zero and freewheeling diode 8 is also turned off, so that the iron core of pulse transformer 14 is reset without being saturated.

FIG. 3 is a circuit diagram showing a portion of the conventional example shown in FIG. 2, and the problems of the prior art will be described below using FIG. However, the overdrive circuit part in the on-gate circuit and the circuit part on the primary side of the pulse transformer in the off-gate circuit are not shown because they are not related.

When the on-gate transistor 5 is turned on, the on-gate current I supplied from the on-gate capacitor 3 should become 101 and flow to the gate of the GTO thyristor 15, but at the moment when the on-gate transistor 5 is turned on, this On-gate circuit and pulse transformer fF secondary winding 14B! The voltage V of the on-gate capacitor 3 is applied to the two points ilI&, and when this voltage vQ is larger than the voltage VD of the parallel diode 10, the parallel diode 10 is forward biased and becomes conductive. do.

Therefore, the on-gate current 1.01 part is the on-gate capacitor 3 → on-gate transistor 5 → secondary winding 14
A current 102 is shunted along the path B→parallel diode 10→on-gate capacitor 3. Therefore, in order to turn on the GTO thyristor 15,
Since the current 101 flowing through the gate of the O-thyristor 15 is reduced, there is a drawback that the rising slope dIG/dt of the on-gate current required to turn on the thyristor 15 is reduced.

FIG. 4 is a waveform diagram of the conventional partial circuit shown in FIG. 3, and FIG.
4(b) shows the change in the current IG2 that flows into the secondary winding of the pulse transformer, and FIG. That is, at the instant of time To when the on-gate transistor 5 is turned on, Z
The voltage vo at the point is equal to the power supply voltage, which is higher than the layer voltage VD of the parallel transistor 10, so a large shunt current IG2 flows, so the turn-on current IGI rises slowly. . At time T, the Z-point voltage vG becomes lower than the embedding layer voltage VD, and eventually reaches the steady state gate voltage Vl)K, so the shunt current I02 is zero after this time T.

As a measure to improve the above-mentioned problems and satisfy the upward slope dlcVdt of the on-gate current required by the GTO thyristor 15, a) the DC voltage of the on-gate circuit should be increased until the decrease in dIG/dt due to the shunting of the on-gate current can be ignored; make it higher.口) Increase the encircling voltage VD by increasing the number of parallel diodes 10 connected in series. c) Replace the parallel diode 10 with a thyristor or a GTO thyristor. Regarding item (a), the resistance loss and switching loss in the on-gate circuit are large and cannot be ignored. Regarding item (1), parts costs will increase. Item c) increases component costs and complicates the circuit. etc., each steam still has its drawbacks.

[Object of the Invention] ' This invention provides an arrangement in which an off-gate circuit that supplies an off-gate current from a pulse transformer tI secondary to the gate of a GTO thyristor and an on-gate circuit that supplies an on-gate current to the gate of the same GTO thyristor are connected in parallel with each other. Provides an inexpensive and reliable gate turn-or-thyristor gate circuit by preventing a reduction in the upslope of the on-gate current when connected without introducing circuit losses, increased component cost, or circuit complexity. The purpose is to

[Key points of the invention]

This invention provides a gate in which an off-gate circuit that supplies an off-gate current from a pulse transformer secondary winding, an on-gate circuit, and an on-gate circuit that supplies an on-gate current are connected in parallel to each other and connected to the gate of a GTO thyristor. In the circuit, a switch element is provided in antiparallel to the freewheeling diode, and this switch element is turned on for a short time when the on-gate current begins to flow, thereby resetting the pulse transformer.

A current is passed through the upper winding, thereby inducing a voltage in the secondary winding that suppresses the on-gate current from shunting to the pulse transformer secondary winding, thereby preventing shunt and applying it to the gate of the GTO thyristor. On-gate current! This is intended to prevent a decline in the upward slope.

[Embodiments of the invention]

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

In FIG. 1, the on-gate circuit that supplies on-gate current to the gate of the GTO thyristor 15 includes an on-gate power supply 1% on-gate capacitor 3. On-gate transistor 5 as an off-gate switching element, resistors 11 and 1
2) speed-up capacitor 13, and since their respective operations have already been explained in the conventional example circuit shown in FIG. 2, a description of these operations will be omitted.

The off-gate circuit that supplies off-gate current to the gate of the GTO thyristor 15 includes an off-gate power source 2) an off-gate capacitor 4, an off-gate transistor 6 as an off-gate switching element, a diode 7, a freewheeling diode 8, a pulse transformer 14, and a freewheeling circuit. A reverse voltage transistor 16 is provided which is connected in antiparallel to the diode 8, and this off-gate circuit is connected in parallel with the above-mentioned on-gate circuit via the parallel diode 10.

The pulse transformer 14 has a primary winding @14A, a lyceter connected in series with it, a winding 11i114c, and a secondary winding 1.
It has three 4B windings, and the polarity of each wire is as shown in the figure. In addition, there are 7 connection points between the primary volume $14A and the lycete volume $140. When an off-gate current is supplied from the off-gate circuit configured in this way, the newly provided reverse voltage transistor 16 remains in the off state, so the operation of the off-gate circuit at this time is shown in FIG. Since this is exactly the same as the conventional circuit and has already been explained, a description of its operation will be omitted.

In the present invention, the on-gate transistor 5 is turned on in order to turn on the GTO thyristor 15 which is in the off state, and at the same time the reverse voltage transistor 16 is turned on. By turning on the reverse voltage transistor 16, the charge of the off-gate capacitor 4 charged to the polarity shown in the figure is transferred to the off-gate capacitor 4 → point Y → resetting, and winding 14C.
→ Reverse voltage transistor 16 → Off-gate capacitor 4
The secondary winding 14 of the pulse transformer 14
At B, a voltage is induced in the direction of the arrow, that is, a voltage in a direction that prevents the on-gate current from being shunted to the secondary winding 14B. If the sum of this induced voltage and the layer voltage VD of the parallel diode IO becomes a value close to the voltage Q from the on-gate circuit, the shunt current will decrease significantly, and if it becomes equal to vG, the shunt current will become zero. Therefore, all the on-gate current from the on-gate circuit is given to the gate. Note that the period during which the reverse voltage transistor 16 is on may be a very short period from time T0 to time Tl in the waveform diagram shown in FIG. 4, and if the reverse voltage transistor 16 is turned off at this time T1, it is turned off Gate capacitor 4 is recharged to GT
Prepare to turn off the O-thyristor 15.

〔Effect of the invention〕

According to this invention, the GTO from the secondary winding of the pulse transformer
In a gate circuit in which an off-gate circuit that supplies an off-gate current to the gate of a thyristor and an on-gate circuit that supplies an on-gate current to the gate of this GTO thyristor are connected in parallel, the pulse transformer is By passing current through the reset winding for a very short time, a voltage is induced in the secondary winding of the pulse transformer in a direction that prevents the on-gate current from being shunted to the secondary winding, thereby turning on the GTO thyristor. Therefore, the on-gate current supplied to the gate is not shunted, so this on-gate current! The uphill gradient d1G/dt does not decrease, and the GTO is reliably and promptly carried out.
Thyristor can be turned on.

Moreover, since it is only necessary to add a switch element in antiparallel to the freewheeling diode to energize the reset winding of the pulse transformer, it is possible to reduce the number of parallel diodes connected in series to suppress the shunting of the on-gate current. It has the advantage of reducing costs and not increasing circuit loss or complicating the circuit. Furthermore, this switch is added because its conduction period is very short and there is no need to flow a large current, so a small capacity one is sufficient.

The cost increase due to the addition of a second element is very small.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention. Fig. 2 is a circuit diagram showing a conventional example of a gate circuit of a gate turn-off thyristor, Fig. 3 is a circuit diagram showing a portion of the conventional example shown in Fig. 2, and Fig. 4 is a circuit diagram showing the conventional example shown in Fig. 3. FIG. 3 is a waveform diagram of a conventional partial circuit. 1...On-gate power supply, 2...Off-gate power supply, 3
... On-gate capacitor, 4... Off-gate capacitor, 5... On-gate switch, on-gate transistor as a first element, 6... Off-gate switch, off-gate transistor as a first element, 7...・Diode, 8...Freewheeling diode, 10...Parallel diode, 11.12...Resistor, 13...Speed-up capacitor% 14...Pulse transformer% 14A・
...Primary winding, 14B...Secondary winding, 14C...Reset 2-way wire, 15...GTO thyristor, 16...
Reverse voltage transistor. Hiki n Yagu

Claims (1)

[Claims] 1) A discharge circuit is configured by the primary winding of a pulse transformer equipped with a reset winding, a capacitor, and an off-gate switch element, and gate turn-off is performed from the secondary winding of the pulse transformer. A gate circuit for a gate turn-off thyristor, in which an off-gate circuit that supplies an off-gate current to the gate of the thyristor and an on-gate circuit that supplies an on-gate current to the gate of the gate turn-off thyristor via an on-gate switch element are connected in parallel to each other. The off-gate circuit is characterized in that the off-gate circuit is provided with reverse voltage inducing means for inducing a voltage with a polarity that prevents the on-gate current from being shunted to the secondary winding of the pulse transformer when the on-gate circuit is in operation. Gate circuit of gate turn-off thyristor. 2) In the gate circuit according to claim 1,
A gate circuit for a gate turn-off thyristor, wherein the reverse voltage inducing means is a switch element that discharges a capacitor charge of the off-gate circuit to a reset winding of a pulse transformer together with an on-gate switching element.