JPS6341836Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a thyristor gate control circuit, and particularly to improved reliability.

Generally gate turn-off thyristor (below
GTO (abbreviated as GTO) has the advantage of being a self-extinguishing element compared to a normal three-terminal thyristor element, and can carry a relatively large current compared to a transistor element, and has positive and negative current only during turn-on and turn-off. It is widely used because it has the advantage of being able to control energization by applying a negative gate pulse. 1st
The figure shows an example of a gate control circuit using a conventional GTO, and FIG. 2 is a waveform diagram of each part of the gate circuit shown in FIG.

In Figure 1, 1 is the GTO, 2 is the first transformer for double-wave rectification, and 3 and 4 are the 1st transformers of the first transformer 2.
On-pulse secondary winding 2 applied to the secondary winding 2a
This is a diode that performs double-wave rectification of the b and 2c outputs.
The negative terminal of this double-wave rectified output is connected to the cathode K of the GTO 1, and the positive terminal is connected to the gate G of the GTO 1 via a resistor 5 to provide an on-gate current I _ON . Further, the secondary winding 6b output of the off pulse applied to the primary winding 6a of the second transformer 6 is connected via a switch 7 that closes the output in synchronization with the off pulse.
An off-gate current I _OFF is applied between the gate G and cathode K of GTO1. In Figure 2, a
and b indicate on-pulses and off-pulses during GTO operation, and the process of transition from on to off between times t ₁ , t ₂ , and t ₃ is enlarged and shown in c, d, e, and f.
c is an on-gate current, d is an on-gate current I _ON , e is an off-gate current I _OFF , and f is a gate current I _G that is a combination of an on-gate current I _ON and an off-gate current I _OFF . Between times t ₁ and t ₂ , the on-pulse shown in the figure c is double-wave rectified by the first transformer 2 and diodes 3 and 4, and is caused to flow as an on-gate current I _ON . Assume that the on-pulse is stopped at time _t2 and an off-pulse is applied. At this time, switch 7 is closed in synchronization with this off-pulse, and the off-gate current is applied to the cathode K-GTO of winding 6b-GTO1.
However, as GTO1 recovers its turn-off characteristics, the impedance between its cathode K and gate G increases, and as shown in FIG. The positive electrode and the gate G generate a voltage with negative polarity. On the other hand, due to this voltage, a part of the off-gate current also flows to the double-wave rectifier circuit constituting the on-gate circuit, and it flows from the secondary winding 6b of the second transformer to the secondary side center tap of the first transformer 2 to each secondary Winding 2
b, 2c - diodes 3, 4 - resistor 5 - switch 7 - secondary winding 6b of the second transformer 6. If the windings 2b and 2c constituting the secondary circuit of the first transformer 2 are completely tightly coupled, the current at this time will not generate magnetic flux, but the unbalance of the windings and the diodes 3 and 4 Magnetic flux is generated due to unbalanced impedance of the circuit including the magnetic flux. As a result, a current as shown in the on-gate current I _ON after time _t3 flows, resulting in a gate current _IG as shown in FIG. 2f.
The current I _G ' in the shaded area in the figure f becomes an erroneous ignition signal, resulting in the disadvantage that the GTO 1 is turned on immediately even though it was turned off.

The present invention was developed in view of the above-mentioned drawbacks, and by inserting a balancing resistor in series with each winding that constitutes the double-wave rectifier circuit, magnetic flux is reduced within the double-wave rectifier transformer. The purpose of this invention is to provide a highly reliable gate control circuit.

The following is a circuit diagram of an embodiment of the present invention shown in FIG.
This will be explained in detail with reference to the waveform diagram shown in FIG.
Note that the same parts as in the first and second figures are designated by the same reference numerals. The difference between FIG. 3 and FIG. 1 is that resistors 8 and 9 are inserted in series with the diodes 3 and 4 of the double-wave rectifier circuit constituting the on-gate circuit. According to the circuit diagram shown in Fig. 3, the effect is the same as in Fig. 1 during the period when the on-gate current I _ON is flowing from time _t1 to _t2 , but the effect after the off-pulse is applied at time _t2 . are different. That is, the switch 7 is closed in synchronization with this off-pulse, and the off-gate current I _OFF changes to the secondary winding 6b- of the second transformer 6.
It flows through the path of cathode K of GTO 1 - gate G of GTO 1 - switch 7 - secondary winding 6b, and part of it flows through secondary winding 6b of second transformer 6 - secondary center of first transformer 2. The current flows from the tap through the paths of the secondary windings 2b, 2c, the diodes 3, 4, the resistors 8, 9, the switch 7, and the secondary winding 6b of the second transformer 6. At this time, by balancing the current flowing in both paths with the resistor 8 and the resistor 9, magnetic flux is generated within the first transformer 2 having the respective secondary windings 2b and 2c of the first transformer 2. can be prevented. Therefore, since there is no significant energy in this double-wave rectifier circuit, Fig. 4d,
High reliability can be obtained without generating false firing signals like the on-gate current I _ON , off-gate current I _OFF , and gate current I _G shown in e and f.

Note that although the above embodiment has been described with respect to a GTO gate control circuit, it is clear that the application example of this gate control circuit is not necessarily limited to the GTO.
In other words, it can be used in a gate auxiliary thyristor or a normal three-terminal thyristor element in which a reverse bias voltage is applied between the gate G and cathode K using the same gate control circuit as in the above embodiment, and the same effect can be obtained. can play.

As detailed above, the present invention eliminates false firing signals by inserting a balancing resistor in series with the windings in the double-wave rectifier circuit that provides the on-gate current and constitutes a part of the gate control circuit. It is also possible to provide a gate control circuit that is highly reliable and inexpensive, since it does not require the use of special resistors for balancing a double-wave rectifier circuit and a transformer for transmitting gate pulses. can.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an example of a conventional thyristor gate control circuit, Fig. 2 is a waveform diagram of the circuit shown in Fig. 1, Fig. 3 is a circuit diagram of an embodiment of the present invention, and Fig. 4 is a circuit diagram showing an example of a conventional thyristor gate control circuit. FIG. 4 is a waveform diagram of each part of the above embodiment. 1...GTO, 2, 6...Trans, 3, 4...
...Diode, 7...Switch, 8,9...Resistor.

Claims (1)

[Scope of utility model registration request] The on-pulse is applied to the gate of the thyristor through a double-wave rectifier circuit consisting of a pulse transformer having an intermediate tap and rectifying elements connected to both ends of the pulse transformer, in which each of the rectifying elements is connected to the gate of the thyristor through a resistor. A thyristor comprising a circuit connected to the gate of the thyristor, connecting the intermediate tap of the pulse transformer to the cathode, and supplying an off-gate current between the cathode and the gate of the semiconductor element at the timing of an off command. Gate control circuit.