JPS611259A - Gate control circuit - Google Patents

Abstract

PURPOSE:To supply sufficient gate current to a self-extinguishing semiconductor element by limiting not to apply a gate control to the element until the charging of a capacitor of a gate circuit is completed. CONSTITUTION:If the voltage of a capacitor 20 is sufficiently established when a gate control signal A of a gate turn OFF thyristor is applied, a flip-flop 24 is set, and its output D becomes ''1''. Accordingly, a signal E point is immediately output, and a gate control signal F of the width determined by a monostable multivibrator 26 is obtained. When a gate current supply is completed, the capacitor 20 of the gate circuit is again charged, and when the charged voltage arrives at the predetermined voltage, a photocoupler 22 is turned ON, and next control signal A is again waited. Thus, necessary gate current can be supplied to the gate of a self-extinguishing semiconductor element.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a gate control circuit for a self-extinguishing semiconductor device, and particularly to a gate control circuit for supplying a steep and large gate current.

[Technical background of the invention and its problems]

Self-extinguishing semiconductor devices such as power transistors and gate turn-off thyristors (hereinafter referred to as GTO) have a relatively large gate with a steep rise between the control electrode and the cathode in order to turn on or turn off at high speed. Current needs to flow.

Generally, a method of discharging the accumulated charge in a capacitor is often used to obtain a large current with a steep rise. Figure $5 is an example of a circuit shown for supplying on-gate current of GTO.Power source L1゜E2 and resistor 10
, 11, capacitor addition, switching element 30 and G
It consists of TO5Q. Figure 6 is an example of a circuit for supplying off-gate current to the GTO, with a power supply E and a resistor to
, ii, capacitor 20, and switching element 30
, 40, G'l'05Q, pulse transformer ω,
diode? It consists of 0, 71, and 72. Figure 7 shows another example of a circuit for supplying the off-gate current of the GTO, which includes a power supply E, a capacitor, and a switching element 30.
and GTO50, pulse transformer mark, and diode 70
, 73. Both of these gate circuits are
When each switching element 30 is turned on, a large current with a steep rise is caused to flow from the capacitor, and after the accumulated charge in the capacitor 20 is discharged to a certain value, current can continue to flow from the power source E. When the switching element 30 is turned off, the capacitor 20 is charged again and waits for the next operation.

However, in any of the circuits shown in FIGS. 5 to 7, it takes time until the capacitor 20 is charged to the desired voltage again after the switching element 30 is turned off. That is, in FIGS. 5 and 6, the time constant of the resistor 10 and the capacitor 20 is the same as that of the inductance of the first winding (nl) on the primary side of the pulse transformer 60 and the capacitor 20 in FIG. This is because there is a charging time constant of .

In a large GTO, the on-gate current is, for example, 1
0~30A peak, off-gate current: 200~
300A peak is required. When performing PWM control in a GTO inverter device or the like, it is necessary to consider the charging time of the capacitor described above in order to supply a sufficient on-gate or off-gate current even when the GTO operating frequency becomes high. If an insufficient gate current is supplied, the GTO may be damaged, which poses a problem.

[Purpose of the invention]

SUMMARY OF THE INVENTION Therefore, an object of the present invention has been made in view of the above-mentioned points, and it is an object of the present invention to provide a gate control circuit that can supply a necessary and sufficient gate current to a self-extinguishing semiconductor element.

[Summary of the invention]

In order to achieve this object, the present invention restricts the gate control signal from being applied to the self-turn-off type semiconductor element until the charging of the capacitor in the gate circuit is completed.

[Embodiments of the invention]

Hereinafter, a simple embodiment of the present invention will be explained with reference to FIG. Figure 4 shows the capacitor 2 shown in Figures 1 to 3.
A Zener diode 21 that detects the charging voltage of 0, a 7-otocap 222 that converts the charging voltage into a logic signal, and 1. G
It consists of a monostable multi % 26 triggered by the inverted signal of the gate control signal of TO, a clip 70 tube U, and an AND circuit 5.

FIG. 2 is a time chart showing the operation of FIG. 1.

The operation shown in FIG. 1 will be explained based on FIG. 2.

When the gate control signal A (on-gate signal or off-gate signal) of the GTO is applied, if the voltage of the capacitor 20 is sufficiently established, the 7-lip 70-tub 24 is set, and its output becomes "1". Therefore, the signal at point E is immediately output, and the gate control signal F having the width determined by the monostable circuit 26 is obtained. The flip 70 is reset at the falling edge of the signal A. When the gate control signal F ends and the gate current supply ends,
The capacitor 20 of the gate circuit is charged again, and the charging voltage is set to a predetermined voltage (the Zener diode 21 in FIG.
When the voltage reaches ), the photocoupler 22 turns on,
Waits for the next control signal A again. The broken line in FIG. 2 indicates time t.

If the control signal A is applied before the capacitor is completely charged, the control is such that it waits until time t1 and outputs the outputs E and F after the charging pressure of the capacitor 20 is established.

FIG. 3 shows another embodiment of the present invention, in which the same reference numerals as in the first embodiment represent the same elements. The operation time chart of FIG. 3 is shown in FIG. 4. In Fig. 3, instead of detecting the capacitor voltage in Fig. 1, a time corresponding to the charging time constant of the capacitor is set in advance using a monostable multi-element, and the gate to the GTO is set before this set time elapses. Control signal F
The configuration is such that it does not occur. The broken line in FIG. 4 indicates time t within the monostable multi setting time mentioned above. This figure shows the operation when control signal A is input at time 1. The gate control signal F is output after the time. Furthermore, noise that has entered within the set time is not output.

In FIGS. 1 and 3, the gate control signal F is converted to a fixed width using a monostable multi-channel signal, but the width is not limited to a fixed width.

〔Effect of the invention〕

As explained above, according to the present invention, a capacitor is provided in the gate circuit of a self-extinguishing semiconductor device, and when a large current with a steep rise is supplied to the gate of the device by discharging and discharging the capacitor, By limiting the output of the gate control signal until the voltage of the capacitor reaches a predetermined value or higher, a necessary and sufficient gate current can be supplied to the gate of the self-turn-off type semiconductor element even during PWM control of the inverter. A gate control circuit for a self-extinguishing semiconductor device can be provided.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIG. 2 is a time chart for explaining the operation of FIG. 1, FIG. 3 is a block diagram showing another embodiment of the present invention, and FIG. The figure is the third
A time chart for explaining the operation shown in the figure, and FIGS. 5 to 7 are conventional gate circuit diagrams. E, E,, E2・DC power supply 10, 11 Resistor 2
0 Capacitor 30.40 Switch element 5Q -, GTO60 pulse transformer 70-73 Diode %, 26 Monostable multi 2J... Zener diode 22 Photocoupler 24 7 lipfrog 25... AND gate (7
3] 7) Agent Patent attorney Noriyuki Chika (1 idiot) Fig. 1 Fig. 2 a tf Fig. 3 tρi7 Fig. 5/n Fig. 6 Fig. 7 7θ

Claims (1)

[Claims] In a gate control circuit comprising a capacitor for supplying a gate current with a steep rise and a large peak value to the gate of a self-arc-extinguishing semiconductor element, and a switching element for discharging the accumulated charge of the capacitor, 1. A gate control circuit comprising: a circuit that directly or indirectly determines whether a charging voltage has reached a predetermined value; and the circuit can control closing of the switching element.