JPH1168475A - Drive circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the malfunction of a power element driven even in a case when a driver IC does not function by providing a charge controlling element between the gate and drain of a switching element MOSFET for turning OFF a power element. SOLUTION: The drain terminal and the gate terminal of N-ch MOSFET 13 constituting a driver IC 14 with P-ch MOSFET 11 are connected through a resistor R17 as a charge controlling element. When a power element IGBT 15 is in an OFF state, and the voltage of an IGBT collector terminal 16, quickly increases, a dV/dT current flows but if a driver IC 14 functions, dV/dT is allowed to escape through MOSFET 13 to maintain the gate of IGBT 15 in an OFF state without being charged. Even if a dV/dT current is generated when IC 14 does not function, MOSFET keeps an ON state by the resistor 17 to prevent the gate of IGBT 15 from being charged to keep IGBT 15 in an OFF state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power element drive circuit, and more particularly to a driver IC for driving a gate of a power element such as an IGBT.

[0002]

2. Description of the Related Art A gate driver IC is used for driving a gate of a power element such as an IGBT. FIG. 3 shows the configuration of the driver IC 14 and the driver I.
The connection relationship between C14 and IGBT15 is shown, and the P-ch MOSFET 11 and the N-ch
The gate drive output (half bridge output) of the driver IC 14 composed of the MOSFET 13 is an IGBT
The source terminal of an N-ch MOSFET 13 provided below the gate drive output is connected to the emitter terminal of the IGBT 15. The gate of the P-ch MOSFET 11 is connected to the preamplifier 10.
In addition, the gate of the N-ch MOSFET 13 is
Are connected to each other.

[0003]

In the above configuration, capacitance exists between the gate and the collector and between the gate and the emitter of the IGBT 15. Therefore, when the voltage between the collector and the emitter rapidly rises, a charging current corresponding to the time change dV / dT of the voltage flows from the IGBT collector terminal 16 to this capacitor as shown by an arrow in the figure. At this time, if the driver IC 14 is functioning, the N-ch MOSFET 13 is ON, so that dV /
The dT current is released through the N-ch MOSFET 13. Therefore, the gate of the IGBT 15 is not charged and maintains the OFF state.

However, the power supply of the driver IC 14 is cut off for some reason, etc.
13 is not ON and the voltage changes over time dV / d
If T is large, the IGBT 15 may be turned on. That is, in the case where the operation of the conventional driver IC is not guaranteed for some reason, it has been difficult to prevent the IGBT 15 from malfunctioning due to the voltage change dV / dT.

The drive circuit of the power element according to the present invention has been made in view of such a point. The purpose of the drive circuit is to control the power to be driven even when the driver IC does not function. An object of the present invention is to provide a drive circuit for a power element that can prevent the element from being accidentally turned on by a simple method.

[0006]

To achieve the above object, a first aspect of the present invention is a drive circuit for a power element, comprising: an amplifying section for amplifying an input signal; And a pair of switching elements provided complementarily, and a terminal connected to the amplifying part of a switching element for turning off the power element among the pair of switching elements, A charge control element provided between the power element and a terminal connected to the control input of the power element.

According to a second aspect of the present invention, there is provided a drive circuit for a power element, comprising a power element, an amplifier for amplifying an input signal, and a complementary circuit connected between the amplifier and the power element. And a power element of the pair of switching elements
A charge control element is provided between a terminal of the switching element for FF connected to the amplifying section and a terminal connected to a control input of the power element.

In a third aspect based on the first or second aspect, the charge control element is a resistance element. In a fourth aspect based on the first or second aspect, the switching element is a MOSFET. In a fifth aspect based on the first or second aspect, the switching element is a bipolar transistor.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a diagram showing the configuration of the first embodiment of the present invention. In FIG. 1, a P-ch MOSFET 11 and an N-ch MOSF having a common drain terminal
The gate drive output (half bridge output) of the driver IC 14 composed of the ET 13 is connected to the gate terminal of the IGBT 15, and the source terminal of the N-ch MOSFET 13 provided below the gate drive output is IG
It is connected to the emitter terminal of BT15. Also, N-ch
A drain terminal and a gate terminal of the MOSFET 13 are connected via a resistor R17 as a charge control element. Further, the gate of the P-ch MOSFET 11 is connected to the pre-amplifier 10 to which a signal from a microcomputer or the like is input.
The gate of the MOSFET 13 is connected to the preamplifier 12 to which a signal from a microcomputer or the like is input. Resistance R
17 may be a poly resistance, a diffusion resistance, or the like.

In the above configuration, the IGBT 15
Is in the OFF state, when the voltage of the IGBT collector terminal 16 rapidly rises, a dV / dT current flows through the capacitance between the gate and the collector of the IGBT 15 as shown by the arrow in the figure. At this time, if the driver IC 14 is functioning, the N-ch MOSFET 13 is ON, and the dV / dT current is released through the N-ch MOSFET 13. Therefore, the gate of the IGBT 15 is not charged and maintains the OFF state.

Here, as described above, the driver IC 14
Is not functioning for some reason, in the conventional configuration, the gate of the IGBT 15 is boosted by being charged by the dV / dT current, thereby increasing the I
GBT 15 turns ON. However, in the configuration of FIG. 1, since the resistor R17 is provided between the drain terminal and the gate terminal of the N-ch MOSFET 13, the driver I
Even if C14 is not functioning, N-ch MOSFET13
Maintains the ON state when a dV / dt current is generated by the resistor R17. Thereby, the driver IC 1
Similarly to the case where the device 4 functions, the gate of the IGBT 15 is not charged, and the IGBT 15 is kept in the OFF state.

FIG. 2 is a diagram showing a configuration of a second embodiment of the present invention. The configuration of the second embodiment is basically the same as that of the first embodiment, except that the gate drive output of the driver IC 14 is a P-ch MOS having a common drain terminal.
Instead of the FET 11 and the N-ch MOSFET 13, a PNP transistor 19 and a N
The difference is that the PN transistor 18 is used. The operation of this configuration is the same as the operation of the first embodiment.

[0013]

According to the present invention, even when the driver IC does not function, it is possible to prevent the power element to be driven from being accidentally turned ON by a simple method.
As a result, it is possible to prevent a secondary problem (destruction of the power element, malfunction of the device) due to a malfunction of the power element.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a first embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a second embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a conventional gate drive circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Preamplifier, 11 ... P-ch MOSFET, 12 ... Preamplifier, 13 ... N-ch MOSFET, 14 ... Driver IC, 15 ... IGBT, 16 ... IGBT collector terminal, 17 ... Resistor R, 18 ... NPN transistor, 19 ... PNP Transistor.

Claims (5)

[Claims] 1. A drive circuit for a power element, comprising: an amplifying section for amplifying an input signal; a pair of complementary switching elements connected between the amplifying section and the power element; Of the pair of switching elements, a charge provided between a terminal connected to the amplifier of the switching element for turning off the power element and a terminal connected to a control input of the power element. A drive circuit for a power element, comprising: a control element; 2. A power element, an amplifying section for amplifying an input signal, a pair of switching elements connected between the amplifying section and the power element and provided complementarily, and the pair of switching elements. A charge control element provided between a terminal connected to the amplification unit of the switching element for turning off the power element and a terminal connected to a control input of the power element; A drive circuit for a power element, comprising: 3. The drive circuit according to claim 1, wherein the charge control element is a resistance element. 4. The switching device according to claim 1, wherein the switching element is a MOSFET.
The drive circuit for a power element according to claim 1, wherein: 5. The drive circuit for a power element according to claim 1, wherein the switching element is a bipolar transistor.