JPS6114750B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention forces the gate turn-off thyristor (a thyristor element whose anode current can be turned on and off by changing the polarity of the gate signal) in response to an abnormality when the gate turn-off thyristor turns off. This invention relates to a semiconductor control device that prevents destruction due to failure of extinguishing a gate turn-off thyristor.

Figure 1 shows an example of a conventional semiconductor control device.
In the figure, 1 is a gate turn-off thyristor (hereinafter abbreviated as GTO), 2 is a power supply, and 3 is a load, and these GTO 1, power supply 2, and load 3 are connected in series. Also, 4, 5 and 6 are respectively
Among the anode, gate, and cathode electrodes of the GTO 1, the gate electrode 5 is connected to the negative electrode of the power source 2 via a power source 7 and a switch element (for example, a transistor element) 8. Further, the gate electrode 5 is connected to the negative electrode of the power source 2 via a control power source 9, a switch (for example, a transistor element) 10, and a current limiting resistor 11. Further, the negative electrode of the power source 2 is connected to the cathode electrode 6.

Based on this configuration, the switch 10 is turned on and a gate-on current flows from the gate electrode 5 to the cathode N layer 12 to turn on the GTO 1 and supply power to the load 3. In order to stop the supply of GTO 1, a relatively large pulse current is caused to flow from the cathode electrode 6 to the N layer 12 using an off circuit using a power supply 7 and a switch 8 to turn off the GTO 1. When turning off GTO1, (a) when the load current that GTO1 should be turned off exceeds a specified value, (b) when the off-gate current falls below the specified value due to an abnormality in the off circuit, (c) what happens? For some reason, when there is an abnormality such as when the slope dv/dt of the terminal voltage of GTO 1 when the gate is turned off exceeds a specified value, GTO 1 is usually short-circuited and destroyed near the center portion 13 of the cathode.

Conventionally, it has been proposed to turn on the switch 10 on the gate-on side to re-ignite the GTO 1, but since the normal power supply 9 has a small voltage and capacity, and there is an off-power supply 7 circuit, this circuit cannot be used. A loop is created, and the on signal is not supplied to GTO1, and even if it is supplied, the on state is weak and is not sufficient to restart it in the event of an abnormality.

In view of these points, the present invention applies a large gate-on current to the gate turn-off thyristor from the gate electrode for restriking, thereby reliably restriking the gate turn-off thyristor, and preventing the gate turn-off thyristor from turning off due to an abnormality. The purpose is to provide a semiconductor control device that prevents permanent damage, and will be described below using examples.

FIG. 2 shows an embodiment of the semiconductor control device according to the present invention, and in this figure, the same reference numerals are used for the same parts or parts having the same functions as in FIG. 1. 12a and 12b are divided cathode N layers, and cathode electrodes 6a and 6b are provided on these N layers 12a and 12b, and these electrodes 6a and 6
b is connected to the positive electrode of the gate reverse power source 7 and the negative electrode of the power source 2. Reference numeral 14 denotes a restriking gate electrode disposed between the divided cathode electrodes 6a and 6b.
6 to the positive electrode of a comparatively large control power supply 20 on the power supply voltage side, which is provided separately from a turn-off power supply (not shown). Here, the diode 15 is for covering the withstand voltage (blocking voltage applied to the GTO 1) of the switch element 16.
Reference numeral 17 is a current shunt that detects a change in the slope of the anode current of GTO 1 during the falling period, that is, a portion of the current increase within the frame C of the two-dot chain line in FIG. 4B. Based on the detection signal of this current shunt 17, a control signal Source 18 turns switch element 16 on.

Next, the operation will be explained.

When the switch element 8 is turned on, a reverse voltage is applied from the gate reverse power supply 7 between the divided cathode electrodes 6a, 6b and the gate electrode 5, and the GTO 1 is turned off.

Figure 3 shows the normal turn-off operation waveform of GTO, where i _T (t) is the current waveform flowing through GTO1,
v _A (t) is the voltage waveform across GTO1 at this time,
i _gr (t) represents the waveform of the gate reverse current applied to turn it off, and v _g (t) represents the waveform of the terminal voltage between the gate and cathode.

As shown in the waveform of FIG. 3, the current i _T (t) falls when the junction J ³ of FIG. 2 is in the recovery state, and the voltage of the control power supply 20 is applied to the switch 16 of FIG. GTO1 is damaged during the turn-off period shown in FIG. 3, especially after the current i _T (t) begins to fall. That is, at this time, the voltage v _g (t) between the gate and the cathode has recovered from the short state, and therefore, the change (increase) in the slope during the falling period of the anode current (see FIG. 4B) is expressed as the current shunt 17.
When detected, the switch 16 is turned on by the control signal source 18, so that the positive voltage of the control power source 20 is applied to the terminal (gate electrode) 14 via the diode 15. Therefore, from the control power supply 20 to the terminal (gate electrode) 14 → the lower semiconductor layer (P ₂ layer) of the junction J ₃ →
Cathode N ₂ layers 12a, 12b → cathode electrode 6
A large current flows through the paths a and 6b. This current is applied to power supply 7 to reverse bias junction _J3 .
Since the current flowing from the cathode through the _N2 layer and the _P2 layer is larger than the current flowing from the cathode to the P2 layer, the junction _J3 , which was previously reverse biased by turning on the switch element 8, becomes forward biased, and as a result, GTO1 turns on (re-ignition). .

By the way, Figure 4 shows the results of investigating the details of the current waveform flowing through GTO1 when a failure occurs.
is a waveform of normal operation, but B of the same figure is a waveform before an abnormality (failure) occurs, and it was found that the current tends to increase once during the current decreasing period. As shown in Figure 4B, the tendency for the current to increase once during the current falling period occurs when the current that should be cut off is too large for the gate reverse current, or when the gate reverse current is too large for the current that should be cut off. This occurs either when the voltage is too small or when the slope (dv/dt) of the reapplied voltage is too large. Therefore, as shown in FIG. 2, the current increase (abnormality) during the falling phase of the anode current i _T (t) is detected by the current shunt 17, and the control signal source 18 outputs the signal from the switch 16.
Control power supply 2 is immediately turned on by issuing an on command to
Large gate on current (ignition command) from 0
It can be applied to GTO1, re-igniting GTO1, and preventing damage due to failure to extinguish the arc. Usually GTO1
The turn-off of is recovered from the side near the off terminal 5 in FIG. It is preferable to provide the re-ignition electrode (terminal) 14 at a portion far from the rear. A general model of this embodiment is shown in FIG. That is, the central portion of each cathode terminal 6 is divided into sections 6a and 6b, and gate terminals 14 for restriking are provided.
4 are connected by a conductive wire 19 and connected to a diode 15.

Note that the voltage of the control power supply 20 is specified to be below the breakdown voltage of junction _J3 , but this voltage is usually about 15 to 20V, and the restriking current is
It is easy to flow a gate current of 10A or more.

The operation example of the present invention was explained by detecting the abnormal current waveform value shown in FIG. 4 (see box C in FIG. 4B) using the current shunt 17 in FIG. 2 and turning on the switch 16. However, this is not limited to ignition of the switch 16. For example GTO
It is also possible to detect, for example, by the current shunt 17, when the current layer flowing through the switch 1 exceeds a specified value, and to fire the switch 16 so as not to issue an off signal. Furthermore, although not shown, the slope dv/dt of the terminal voltage of GTO 1 is detected, and when this value exceeds a specified value, the switch 16 is fired and the GTO
1 can be re-fired. Although the current of the GTO 1 becomes as shown in section C in FIG. 4B during an abnormality, the present invention is not necessarily limited to the method of detecting the current waveform of this section C and igniting the switch 16.

Furthermore, the gate turn-off thyristor (DTO) in this embodiment includes not only a thyristor that can be turned on and off by a gate, but also a thyristor that assists turn-off by applying a reverse bias to the gate.

As described above, according to the present invention, abnormal operation during the turn-off period of the gate turn-off thyristor can be detected by, for example, anode current (switching current).
For example, a control power supply provided separately from the turn-on power supply is used to flow a restriking gate current from the restriking gate electrode to the restriking gate electrode. The gate turn-off thyristor can be forcibly re-ignited, and damage caused by failure of the gate turn-off thyristor to extinguish can be prevented, which is extremely effective.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing an example of a conventional semiconductor control device, Fig. 2 is an explanatory diagram showing an embodiment of the semiconductor control device according to the present invention, and Fig. 3 is a normal turn-off operation waveform of a gate turn-off thyristor. FIG. 4 is a diagram for explaining the current waveform flowing through the gate turn-off thyristor when a failure occurs. FIG. 5 is a model plan view showing an embodiment of the present invention. Gate turn-off thyristor (GTO), 2 and 7 are power supply, 3 is load, 4 is anode electrode, 5 is gate electrode for off, 6a, 6b
is a cathode electrode, 8, 16 is a switch element, 12
a, 12b are cathode N layers, 14 is a gate electrode for restriking, 15 is a diode, 17 is a current shunt, 18 is a control signal source, 19 is a conducting wire, 20
indicates the control power supply.

Claims (1)

[Claims] 1. In a circuit that applies a positive or negative gate signal to the gate of a gate turn-off thyristor to turn on and off this gate turn-off thyristor element, a gate electrode for restriking separate from the gate is provided, and the A semiconductor control device characterized in that the gate turn-off thyristor is configured to detect a turn-off failure of the gate turn-off thyristor and force the gate turn-off thyristor to re-ignite by flowing a rest-ignition gate current from a rest-ignition gate electrode. Device.