JPH0324817B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gate drive circuit for a gate turn-off thyristor that is turned on and off by gate current.

A gate turn-off thyristor (hereinafter abbreviated as GTO) has a self-extinguishing ability and is a highly functional power semiconductor device. However, the turn-on gain is lower than that of a thyristor, and overdrive is required when turning on. In addition, the holding current is large, and during the on period, a considerably larger gate current must flow than in a thyristor. Furthermore, at turn-off, a very large off-state current must flow through the gate, resulting in an off-state current of over 200A to cut off the main current of 1000A. As a result, gate circuits tend to be complex and quite expensive. This becomes noticeable in applications where the main circuit voltage is high and the number of semiconductor elements is large, such as inverters for trains, due to the problem of insulation from the gate control circuit.

FIG. 1 is a diagram showing an example of a conventional GTO gate drive circuit, and FIG. 2 is an explanatory diagram of its operation. In Figure 1, P is the positive terminal of the DC power supply, N is the negative terminal of the DC power supply, T _ON is a transistor for ON, S _ON is a thyristor for preventing ON/OFF interference, R ₁ and R ₂ are resistors,
PT _ON is an insulating pulse transformer for ON (hereinafter referred to as ON gate transformer), which constitutes a narrow ON gate circuit.

T _OFF is an OFF transistor, D _F is a diode that blocks the on-gate current from flowing to the OFF circuit,
PT _OFF is an insulating pulse transformer for OFF (hereinafter referred to as OFF gate transformer), which constitutes an OFF circuit.

T _W1 and T _W2 are transistors for generating wide gate pulses that are turned on and off alternately at high frequencies, PT _W is a wide insulating pulse transformer (hereinafter referred to as wide gate transformer), and D _W1 and D _W2 are wide gate transformers. P _TW is a diode for full-wave rectification of the secondary voltage, and R ₃ is a resistor, forming a wide on-gate circuit.

The control signals for each transistor are shown in Figure 2 a to c.
The gate current of the GTO is given as shown in Fig. 2d, and the overdrive current starts to flow at time t ₁ , the overdrive current stops flowing at time t ₂ , and the gate current starts flowing at high frequency as shown in the figure as a wide gate current. The current is full-wave rectified. Furthermore, at time _t3 , an off-gate current flows and turns off the GTO,
The off-state current becomes zero at time _t4 .

This conventional example requires three types of control signals,
The circuit becomes very complex. What is even worse is that, as shown in Figure 1, in addition to the off-circuit current that flows from the GTO cathode to the gate, shown by the solid line, it also flows into the wide on-gate circuit, as shown by the dotted line. Especially when the main current of the GTO is suddenly cut off and there is a voltage between the cathode and gate,
The current is only shown by the dotted line in FIG. This current is a value that cannot be ignored because the resistance is considerably lower than that in the case where the resistor R ₃ is a thyristor (usually 2 to 3 A or more is required as a wide on-current). This current not only reduces the off-current utilization rate, but also when the off-gate pulse disappears,
The current flowing through the wide on-gate circuit also tends to disappear, but the current shown by the dotted line in Figure 1 continues to flow due to the inductance of the winding of the wide gate transformer PT _W and the wiring inductance of the circuit.

On the other hand, the OFF gate transformer PT _OFF generates a reverse induced voltage by cutting off the OFF transistor T _OFF , and operates to block the secondary winding current. Therefore, the current in the wide on-gate circuit described above flows to the gate and cathode of the GTO, as shown by the dotted line at time _t4 in the gate current waveform of FIG. 2d, and may turn on the GTO.

Therefore, a switch element is always required in a wide on-gate circuit, and when a circuit for generating an isolated control signal for controlling this switch element is also considered, the circuit becomes extremely complicated.

Furthermore, as shown in the gate current in Figure 2d, as a wide on-gate signal, discontinuity in the gate current due to the full high frequency is always generated.
This has a very negative effect on the operation of GTO.

The present invention has been made in view of the above-mentioned drawbacks of the conventional art, and the present invention will be explained below based on the drawings of the embodiments. FIG. 3 shows an embodiment of the present invention.
In the GTO gate drive circuit diagram, parts having the same functions as those in FIG. 1 are designated with the same reference numerals. E is a wide on-gate power supply, which may be any insulated DC power supply (hereinafter referred to as DC power supply E). S _W is a control thyristor that turns on and off the wide on-gate current, _R4 is a resistor that limits the gate current of the control thyristor S _W ,
S _OFF is the _SW for turning off the control thyristor _SW .
The off transistor _R5 is a resistor that limits the current that turns on and off this switch element (S _OFF ).

In FIG. 3, the configurations of the narrow ON gate circuit to which the ON control signal is applied and the OFF circuit to which the OFF control signal is applied are the same as in FIG. Connect one end of resistor R ₃ to the positive terminal of , and connect the other end of this resistor R ₃ with
A control thyristor _SW is connected between the gate of the GTO and the cathode facing the gate of the GTO, and a wide on-gate circuit is provided in which the negative electrode of the DC power supply E is connected to the cathode of the GTO. The thyristor S _W is ignited using the secondary voltage of the ON gate transformer PT _ON , and the cathode is connected to the terminal side not marked with the terminal of the secondary winding of the OFF gate transformer PT _OFF , and the anode is connected to the gate of the GTO. A SW- _off transistor S _OFF is connected between the cathode of the diode D _F connected to the anode of the control thyristor SW, and the _{SW -} off transistor
The control thyristor _SW is short-circuited by conduction of S _OFF , and this SW _OFF transistor S _OFF
is made conductive by the secondary voltage of the off gate transformer PT _OFF , and the control thyristor _SW is turned off.

Next, the operation of the circuit according to the embodiment shown in FIG. 3 according to the present invention will be explained with reference to FIG. At time _t1 , the on control signal shown in Figure 4a is applied to the on transistor.
Applied to T _ON , turning on the on transistor T _ON . This will turn on the gate transformer PT _ON.
When voltage is applied to PT ON and the thyristor S _ON for preventing on/off interference turns on, the PT _ON secondary winding
Resistor R ₂ → GTO gate → GTO cathode → S _ON →
PT _ON Current flows through the secondary winding path, turning on the GTO. At this time, a resistor which is a parallel circuit of resistor R ₂
Current also flows through the path R ₄ → _SW gate → _SW cathode, turning on the control thyristor _SW . Therefore, current also flows from the DC power supply E through the path of resistor R ₃ →S _W →GTO gate → GTO cathode → DC power supply E, resulting in a wide on-gate current (Figure 4b).

As shown in Figure 4a, the on control signal disappears at time _t2 , and the thyristor S for preventing on/off interference _{turns on.}
is turned off, but the control thyristor _SW continues to be turned on and a wide on-gate current continues to flow from the DC power supply E (Fig. 4b).

At time _t3 , an off control signal is applied to the off transistor _TOFF , turning on the off transistor _TOFF , as shown in FIG. 4c. As a result, a voltage is applied to the off gate transformer PT _OFF , and an off current flows through the path shown by the solid line in Figure 3, turning off the GTO (Figure 4 d). When the GTO is suddenly disconnected, the secondary voltage of the OFF gate transformer PT _OFF causes S _W
Current flows through the off transistor S _OFF through the path shown by the dotted line in Figure 3, turning on the _SW off transistor S _OFF . When the S _W transistor S _OFF turns on, the current flowing through the control thyristor S _W is commutated to the S _W off transistor S _OFF , and the DC power supply E → resistor R ₃ → S _OFF → PT _OFF Secondary winding Line → DC power supply E
Current begins to flow through the path. This operation turns off the control thyristor _SW , and the wide on-gate current no longer flows (Figure 4b). The off-state current becomes zero at time _t4 .

As described above, according to the present invention, with a relatively simple circuit configuration, it is possible not only to overdrive the GTO and perform wide on-gate and off-gate using two narrow-width signals for on and off; Interference between each circuit is completely eliminated, and the wide on-gate current can be made into a complete direct current, making it possible to operate the GTO reliably.

[Brief explanation of drawings]

FIG. 1 is a gate drive circuit diagram of a conventional gate turn-off thyristor, FIG. 2 is an explanatory diagram of the operation of the circuit shown in FIG. 1, and FIG. 3 is a gate drive circuit diagram of a gate turn-off thyristor showing an embodiment of the present invention. FIG. 4 is an explanatory diagram of the operation of the circuit shown in FIG. T _ON ...Transistor for ON, T _OFF ...Transistor for OFF, T _W1 , T _W2 ...Transistor for wide gate pulse generation, PT _ON ...Isolated pulse transformer for ON, PT _OFF ...Isolated pulse transformer for OFF, PT _W ...
Wide isolation pulse transformer, D _W1 , D _W2 , D _F ... diode, S _ON ... thyristor for preventing on/off interference, S _W ... control thyristor, S _OFF ... transistor for SW OFF, _GTO ... gate turn-off thyristor, _R1 to _R5 ...Resistance.

Claims (1)

[Claims] 1 Connect the primary winding of the on-gate transformer and the series circuit of the on-transistor between the positive and negative poles of the low-voltage side DC power supply, and connect the primary winding of the off-gate transformer and the series circuit of the off-transistor. A second resistor R 2 is connected between the positive terminal of the secondary winding of the ON gate transformer and the gate of the controlled gate turn-off thyristor, and a second resistor R ₂ is connected between the negative terminal of the secondary winding of the ON gate transformer and the gate of the controlled gate turn-off thyristor. An on/off interference prevention thyristor is connected between the cathode of the controlled gate turn-off thyristor so that the anode is on the cathode side of the controlled gate turn-off thyristor, and the positive terminal of the secondary winding of the on gate transformer is connected to the on/off interference prevention thyristor. an overdrive circuit in which a first resistor _R1 is connected between the gates of the thyristor for preventing off interference;
The positive terminal of the next winding was connected to the cathode of the controlled gate turn-off thyristor, and a diode was connected between the negative terminal and the gate of the controlled gate turn-off thyristor so that the anode was on the gate side of the controlled gate turn-off thyristor. In the off-gate circuit, one end of the third resistor R ₃ is connected to the positive electrode of the high voltage side DC power supply, the other end of the resistor R ₃ is connected to the anode of the control thyristor, and the cathode of the control thyristor is connected to the controlled gate turn-off. A fourth resistor (R ₄ ) is connected to the gate of the thyristor, and connects the negative terminal of the high-voltage side DC power supply and the cathode of the controlled gate turn-off thyristor, and between the gate of the control thyristor and the positive terminal of the on-gate gate transformer. a wide on-gate circuit connected to the control thyristor, and a control thyristor off transistor so that the collector is connected to the anode of the control thyristor and the emitter is connected to the cathode of the diode, and the base of the control thyristor off transistor is connected to the control thyristor off transistor. A gate drive circuit for a gate turn-off thyristor, characterized in that a fifth resistor (R ₅ ) is connected between the positive terminal of the gate transformer for turning off.