JPH07122985A - Gate circuit - Google Patents

Abstract

PURPOSE:To provide the gate circuit of an IGBT and a GTR which does not turn on the IGBT and the GTR at the time of turning off a power source. CONSTITUTION:In the gate circuit of an IGBT and a GTR where the bipolarity power source obtained from the rectifier circuit 3 connected with the secondary side of a transducer 2 is made a power source, the control signal of the IGBT or the GTR becomes off when the power source is turned off and the gate voltage of the IGBT or the GTR becomes minus voltage because the bipolarity power source is connected with each capacitor 41 and 42 and the capacitance connected with the plus side of the power source is made smaller than the capacitance connected with the minus side and the voltage on the side of the plus becomes zero first because the resistance value or the capacitance on the plus side of the bipolarity power source is smaller than the resistance value or the capacitance on the minus side. Therefore, plus voltage is not impressed on the gate of the IGBT or GTR when the power source is turned off.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gate circuit for an IGBT or GTR which prevents malfunction of the gate circuit when the power is off.

[0002]

2. Description of the Related Art Conventionally, capacitors and resistors attached to bipolar power supplies of an IGBT gate circuit have the same rating. However, when the power supply of the gate circuit of the IGBT is turned off, the control signal of the IGBT is turned off and the IG
A negative voltage is applied to the gate voltage of BT. For this reason, the voltage on the negative side of the bipolar power source becomes zero first, but at this time the voltage on the positive side still remains,
There is a drawback that the output of the gate circuit becomes a positive voltage and the IGBT is turned on. The GTR gate circuit also has the same drawbacks as the IGBT gate circuit.

[0003]

SUMMARY OF THE INVENTION The present invention has been made to solve the above drawbacks, and an object thereof is to provide an IGBT or GTR gate circuit which does not turn on the IGBT or GTR when the power is turned off.

[0004]

In order to achieve the above object, the first aspect of the present invention is to use an bipolar power source obtained from a rectifier circuit connected to the secondary side of a transformer as a power source.
In the gate circuit, a capacitor is connected to each of the bipolar power supplies, and the capacitor capacity connected to the positive side of the power supply is smaller than the capacitor capacity connected to the negative side. In addition, claim 2
In a gate circuit of an IGBT which uses a bipolar power source obtained from a rectifier circuit connected to the secondary side of a transformer as a power source, a parallel circuit of a resistor and a capacitor is connected to each bipolar power source, It is characterized in that the resistance value of the positive side resistance is made smaller than the resistance value of the negative side resistance. Further, claim 3 uses a bipolar power source obtained from a rectifier circuit connected to the secondary side of the transformer as a power source.
In the TR gate circuit, a parallel circuit of a resistor and a capacitor is connected to each of the bipolar power supplies, and the resistance value or the capacitance of the power supply on the plus side is smaller than the resistance value or the capacitance of the minus side. And

[0005]

According to the present invention, when the power is turned off, the IGB
The control signal of T or GTR is turned off and the gate voltage of IGBT or GTR becomes a negative voltage, but the positive side resistance value or capacitor capacity of the bipolar power supply is smaller than the negative side resistance value or capacitor capacity, so the positive side Voltage becomes zero first. Therefore, no positive voltage is applied to the gate of the IGBT or GTR when the power is off.

[0006]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a circuit configuration diagram of an embodiment of the present invention. As shown in the figure, the power source 1 is connected to the primary side of a transformer 2 for insulating and stepping down, and the rectifier circuit 3 is connected to the secondary side of this transformer 2 to obtain a bipolar power source. A capacitor 41 and a resistor 51 are connected in parallel on the positive side of the bipolar power source, and a capacitor 42 and a resistor 52 are connected in parallel on the negative side. However, the capacitor 42 has a larger capacity than the capacitor 41, and the positive resistance 51
The resistance value of is smaller than the resistance value of the resistor 52 on the negative side.

The control signal 6 of the IGBT 7 is input to an insulating circuit 8 composed of a photocoupler, and its output is input to an amplifier circuit 9. As the power source of the amplifier circuit 9, the positive side of the capacitor 41 and the negative side of the capacitor 42 are used. The output of the amplifier circuit 9 is the gate series resistance 1
Connected to the gate of the IGBT7 through 0
The emitter of is connected to AG, which is the zero potential of the bipolar power supply.

Next, the operation of this embodiment will be described with reference to the time chart of FIG. Now, when the power supply 1 is turned off,
The control signal 6 of the IGBT 7 is turned off, and the gate voltage of the IGBT 7 becomes a negative voltage. Therefore, of the bipolar power supplies supplied to the amplifier circuit 9, the negative power supply consumes a large amount of current, but the capacitor 42 has a larger capacity than the capacitor 41. Therefore, the voltage of the positive power supply capacitor 41 becomes zero first, and After a further delay, the voltage of the negative power supply capacitor 42 becomes zero. Therefore, when the power supply 1 is turned off, the positive voltage is not applied to the gate of the IGBT 7, so that the IGBT 7 does not turn on erroneously.

As another embodiment of the present invention, capacitors 41 and 42 and resistors 51 and 52 are connected to the bipolar power supplies supplied to the amplifier circuit 9 connected to the gate circuit of the IGBT 7, respectively. Even if the resistance value of the resistor 51 is set smaller than the resistance value of the resistor 52 on the minus power source side, the same operation as in the above embodiment is obtained. That is, when the power supply 1 is turned off, the gate voltage of the IGBT 7 becomes a negative voltage.
For this reason, a current more than the current consumption of the negative power source flows through the resistor 51 on the positive power source side, and the voltage on the positive side becomes zero first. Therefore, when the power supply 1 is turned off, the IGB
Since the gate of T7 does not become a positive voltage and decreases to zero with a negative voltage, the IGBT 7 does not turn on erroneously.

Although the IGBT gate circuit has been described in each of the above-described embodiments, the present invention is not limited to the IGBT element but can be applied to a GTR element.

[0011]

As described above, according to the present invention,
Since the illegal operation of the gate circuit of the IGBT or GTR at the time of power-off can be prevented, the IGBT or GTR is prevented from being illegally turned on, and the reliability can be improved.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of an embodiment of the present invention.

FIG. 2 is a time chart of each point when the power is turned off in FIG.

[Explanation of symbols]

1 ... Power supply, 2 ... Transformer, 3 ... Rectifier circuit, 41, 42 ...
Capacitors, 51, 52 ... Resistors, 6 ... Control signals, 7 ... I
GBT, 8 ... Insulation circuit, 9 ... Amplification circuit, 10 ... Gate series resistance.

Claims (3)

[Claims] 1. A gate circuit of an IGBT, which uses a bipolar power source obtained from a rectifier circuit connected to a secondary side of a transformer as a power source, wherein a capacitor is connected to each bipolar power source, and the positive side of the power source. An IGBT gate circuit characterized in that the capacitance of the capacitor connected to is smaller than the capacitance of the capacitor connected to the negative side. 2. A gate circuit of an IGBT which uses a bipolar power source obtained from a rectifier circuit connected to the secondary side of a transformer as a power source, wherein a parallel circuit of a resistor and a capacitor is connected to each bipolar power source, A gate circuit of an IGBT, wherein a resistance value of a positive side resistance of the power source is made smaller than a resistance value of a negative side resistance. 3. A gate circuit of a GTR using a bipolar power source obtained from a rectifier circuit connected to the secondary side of a transformer as a power source, wherein a parallel circuit of a resistor and a capacitor is connected to each bipolar power source, A gate circuit of a GTR, characterized in that the resistance value or the capacitance of the power source on the plus side is made smaller than the resistance value or the capacitance of the minus side.