JPS6349099Y2 - - Google Patents

Description

[Detailed explanation of the invention] This invention is a gate turn-off. This relates to a drive circuit for a thyristor (hereinafter abbreviated as GTO).

Figure 1 shows an example of a conventional GTO drive circuit, in which 1 is a GTO, 2 is a power supply used to turn on GTO1, 3 is a resistor, and 4 is a power supply for turning on GTO1.
is a capacitor, and the resistor 3 and capacitor 4 constitute a differentiating circuit. Further, 5 is a limiting resistor for limiting the on-gate current, and 6 is a transistor. Further, 7 is a power supply for turning off GTO1, 8 is a capacitor for supplying off current, and 9 is a power supply for turning off GTO1.
is a transistor. Note that FIG. 2 shows the gate current waveform of the GTO, where A shows the on-gate current waveform and B shows the off-gate current waveform.

However, with this configuration,
GTO's off-gain is generally small, so
Even in the case of GTO1, it is necessary to flow an off-state current (off-gate current) in a pulsed manner that is a fraction of the anode current to be cut off. Therefore, the transistor 9 used in the off-gate circuit becomes larger and more expensive due to the increased number of parallel transistors.

The present invention was devised to solve such problems, and will be explained below using examples.

Fig. 3 shows an embodiment of the GTO drive circuit according to the present invention, in which 11 is the GTO;
2 is a power supply for turning on the GTO 11, and the positive terminal of the power supply 12 for turning on is connected to a resistor 1.
3. Connected to the negative terminal of the ON power supply 12 via the capacitor 14, and the negative terminal of the ON power supply 12 is
Connected to the cathode of GTO11. Here, the resistor 13 and the capacitor 14 constitute a differential circuit for supplying an on-gate current. Reference numeral 15 denotes a transistor for supplying on-state current, and the collector electrode of the transistor 15 is connected to the connection point between the resistor 13 and the capacitor 14, and the emitter electrode of the transistor 15 is connected to the gate of the GTO 11 via a limiting resistor 16. 17 is a diode whose anode electrode is connected to the emitter electrode of the transistor 15 and whose cathode electrode is connected to the collector electrode of the transistor 18; and 19 is a diode whose one end is connected to the cathode electrode of the diode 17 and whose other end is connected to the gate of the GTO 11. Connected capacitor, 20 is GTO1
The positive terminal of the off power source 20 is connected to the cathode of the GTO 11, and the negative terminal of the off power source 20 is connected to the emitter electrode of the transistor 18 and the off current supply thyristor 22. connected to the cathode electrode of Further, 21 is a capacitor connected between the positive terminal and the negative terminal of the off power supply 20, and 23 is a capacitor whose collector electrode is the anode electrode of the thyristor 22.
This is a transistor connected to the gate of the GTO 11 and whose emitter electrode is connected to the gate of the thyristor 22 via a capacitor 24. Note that the capacitor 19 and the transistor 18 are used to turn off the thyristor 22. Further, the diode 17 is inserted to prevent the charge in the capacitor 19 from discharging during the off period.

The operation of the circuit of FIG. 2 having such a configuration will be explained below. First, when the transistor 15 is turned on, the on-gate current flows from the transistor 15 to the diode 17 to the capacitor 19 to the gate of GTO 11 to the cathode of GTO 11, but eventually only the path from transistor 15 to resistor 16, gate of GTO 11 to cathode of GTO 11 is passed. It will flow. When the on-gate current is flowing, the capacitor 19 is charged to the polarity shown.

Next, in order to turn off the GTO 11, when the transistor 23 is turned on, a pulse current flows through the capacitor 24 to the gate of the thyristor 22, turning on the thyristor 22, and causing an off-gate current to flow through the thyristor 22 to the GTO 11. GTO1
After 1 turns off, GTO11 is applied to thyristor 22.
A current corresponding to the leakage current between the gate and cathode of GTO 11 flows, and the gate and cathode of GTO 11 are also biased in the opposite direction.

Then, by turning on the transistor 18 a little before inputting the on signal (the drive signal for the on-current supply transistor 15), the thyristor 22
is reverse biased by the charge on capacitor 19,
Turn off.

Further, in this state, by turning on the transistor 15, the same operation as described above is repeated.

Since the off-gain of GTO is low, the off-state current (off-gate current) needs to flow at a fraction of the anode current that is to be cut off in a pulsed manner.
For this reason, when conventional semiconductor switching elements such as transistors which are limited by the current amplification rate, such as the transistor 9 for supplying off-state current as shown in FIG. 1, are used, the number of parallel elements of these elements increases and the cost becomes high. Therefore, in the embodiment of the present invention shown in FIG. 3, the thyristor 22 is used as the switching element for supplying the off-state current of the off-gate circuit, and the arc-extinguishing power for the thyristor 22 is taken from a part of the on-gate circuit (a part of the on-power supply). Since the arc-extinguishing circuit of the GTO11 is simplified, the gate circuit of the GTO11 can be made smaller and lower in price.

Note that in this embodiment, the transistors 15,
Although transistors 18 and 23 are used, these transistors 15, 18 and 23 can be replaced with other switching elements.

If the GTO drive circuit according to the present invention described above is used, a thyristor is used as the switching element for supplying off-state current in the off-gate circuit, and power for extinguishing the thyristor is taken from a part of the on-gate circuit. miniaturization of
This has extremely great effects, such as being able to lower prices.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing an example of a conventional GTO drive circuit, Figure 2 is a GTO gate current waveform diagram,
FIG. 3 is a circuit diagram showing an embodiment of the GTO drive circuit according to the present invention, in which reference numeral 11 indicates the GTO,
12 is a power supply for turning on, 13 and 16 are resistors, 14 and 1
9, 21, 24 are capacitors, 15, 18, 23
1 is a transistor, 17 is a diode, 20 is an off power supply, and 22 is a thyristor.

Claims (1)

[Scope of utility model registration request] A series connection of a first resistor and a first capacitor is connected in parallel with the ON power supply, and a connection point between the first resistor and the first capacitor is connected to a first switching element and a second resistor. Gate turn-off through. A series body of a diode and a second capacitor is connected to the gate of the thyristor in parallel with the second resistor, and the negative terminal of the turn-on power source is connected to the gate turn-off. The connection point between the diode and the second capacitor is connected to the negative terminal of the OFF power supply and the cathode of the OFF current supply thyristor via a second switching element, and the OFF switch is connected to the cathode of the thyristor. Gate turn off the positive terminal of the power supply. A third capacitor is connected to the cathode of the thyristor and connected in parallel with the power supply for turning off, and the anode of the thyristor is connected to the gate turn-off. A gate turn-off, characterized in that it is connected to the gate of a thyristor, and a third switching element is connected between the anode and gate of the thyristor. Thyristor drive circuit.