JPH0250518A - Driving circuit for static induced type self-arc extinction element and inverter device static induced type self-arc-suppressing element - Google Patents

Abstract

PURPOSE:To always decrease and interrupt and over-current and to prevent the element destruction by taking priority to the fact that a gate voltage is lowered to a prescribed value more than the stopping signal at a control side after the over-current is detected. CONSTITUTION:The gate and collector of a static induced type self-arc extinction element IGBT 10 are connected through a resistance 11 and a diode 12 and the connecting point of the resistance 11 and the diode 12 is connected to the base of a transistor 15. An equivalent overcurrent detecting circuit to detect the collector voltage during the gate voltage impression is constituted at an IGBT 10. An overcurrent detecting signal is transferred to a control side by the transistor 15, the resistance 17, a diode 18 and a capacitor 19 and a gate voltage adjusting circuit is constituted. To the emitter of the transistor 15, a resistance 20 and a capacitor 21 are connected, one side of the capacitor 21 is connected to the base of a transistor 23, the collector of a transistor 23 is the collector of a transistor 3 and an ON holding circuit is constituted. Thus, when the overcurrent is detected, after the flow is surely decreased, the interruption can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a drive circuit for a self-extinguishing element, and particularly to a drive method suitable for safely shutting off an excessive current flowing through the element.

[Conventional technology]

Due to the need for smaller power supplies and lower noise, electrostatic induction self-extinguishing devices (MOS), which can perform high-speed switching operations, have been developed.
-FET, IGBT, etc.) are beginning to be used. Taking these elements, such as IGBTs, as an example, the flowing collector current is determined by the gate voltage and collector voltage, as shown in FIG.

If such an element is used in a main switch of an inverter or the like to operate at high speed, the following problems will arise.

In a power supply device such as an inverter, when an arm short circuit or a load short circuit occurs, a power supply voltage is applied to elements that are in an on-operation state. As a result, an excessive short circuit current flows due to the relationship shown in FIG. 5, for example. In the case of IGBT, JP-A-61-1
As described in Publication No. 85064, if the collector current becomes too large, the device may be destroyed due to the latch-up phenomenon in which it cannot be controlled by the gate voltage. The jump voltage due to the energy of the circuit inductance is large, and it often exceeds the withstand voltage of the element and causes destruction.

For this reason, a proposal has been made to control the gate voltage in an electrostatic induction type self-extinguishing element (Japanese Patent Laid-Open No. 147736/1983).
Publication No. 185064/1983, Japanese Patent Application Laid-open No. 185064/1983
-277063, U.S. Patent No. 4,581.540
No. 4,721,869). These methods reduce and cut off the excessive current, and are suitable methods as long as the excess current can be detected during the energization period and the current can be reduced and cut off.

[Problem to be solved by the invention]

However, in inverters and other devices that perform high-speed switching operations, the energizing period of these elements is narrow, so even if an overcurrent is detected, the energizing period ends while the current is decreasing, and the excessive current is eventually cut off and the elements are damaged. There is a problem of destruction.

It seems that this problem can be solved by detecting the overcurrent and transmitting it to the control side to extend the energization period, but since there is a delay time from detection to control, this problem cannot be solved easily.

The present invention has been made in order to solve such problems.It is an object of the present invention to provide a drive circuit with an overcurrent protection function that always reduces the current and then shuts off the current when an overcurrent is detected. .

[Means to solve the problem]

The driving circuit for an electrostatic induction type self-extinguishing element of the present invention that achieves the above object is characterized by: a constant voltage power source; an electrostatic induction type self-extinguishing element having a collector, an emitter, and a gate; a gate voltage input circuit that applies a voltage generated from the constant voltage power source to the gate of the electrostatic induction type self-extinguishing element according to the magnitude of the on/off command signal; and the electrostatic induction type self-extinguishing element. When the collector voltage of the electrostatic induction type self-extinguishing element is equal to or higher than a predetermined value, the gate voltage is lowered, and the electrostatic induction type self-extinguishing element continues to turn on until the gate voltage decreases to a predetermined value. and means for applying voltage to the gate of the self-extinguishing element.

Further, the inverter device having the electrostatic induction type self-extinguishing element of the present invention which achieves the above object has the following features: 1. second and third constant voltage power supplies, and a load.

A first circuit having a collector, an emitter, and a gate, a collector-emitter current path connected in series between one terminal and the other terminal of a third constant voltage power supply, and a load connected to the connection point. and a second electrostatic induction type self-extinguishing element.

a first gate voltage input circuit that applies a voltage generated from the first constant voltage power source to the gate of the first electrostatic induction type self-extinguishing element in accordance with the magnitude of the input on/off command signal; and a second gate voltage that applies a voltage generated from the second constant voltage power supply to the gate of the second electrostatic induction self-extinguishing element in accordance with the magnitude of the input on/off command signal. When the input circuit and the collector voltage of the first electrostatic induction self-turning element are equal to or higher than a predetermined value, the gate voltage of the first electrostatic induction self-turning element is lowered, and the gate voltage is lowered. The above-mentioned first OFF command signal is
Without applying the voltage generated from the constant voltage power supply to the gate of the first electrostatic induction type self-extinguishing element, the voltage at which the first electrostatic induction type self-extinguishing element continues to be turned on is applied to the first electrostatic induction type self-extinguishing element. means for applying voltage to the gate of the electrostatic induction type self-extinguishing element;
When the collector voltage of the electrostatic induction type self-extinguishing element is equal to or higher than a predetermined value, the gate voltage of the second electrostatic induction type self-extinguishing element is lowered until the gate voltage decreases to a predetermined value. , without applying the voltage generated from the second constant voltage power supply to the gate of the second electrostatic induction type self-extinguishing element according to the magnitude of the off command signal. and means for applying a voltage to the gate of the second electrostatic induction type self-extinguishing element to keep the self-extinguishing element turned on.

Specifically, a detection signal is output to a drive circuit that supplies a predetermined gate voltage according to a control signal, when the on-voltage of the electrostatic induction type self-turning element exceeds a predetermined voltage while the gate voltage is being supplied. an overcurrent detection circuit, a gate voltage adjustment circuit that reduces the gate voltage with a predetermined time constant, and a detection delay circuit that does not consider a high on-voltage during a turn-on delay period to be an overcurrent when the gate voltage rises. In addition, an on-holding circuit is provided so that the gate voltage adjustment circuit operates for a predetermined period of time in priority to the control signal.

[Effect]

In the above configuration, the normal turn-on delay operation of the element is masked by the detection delay circuit and the overcurrent detection circuit does not operate, and when an overcurrent flows due to an abnormality such as a load and is detected, the gate voltage adjustment circuit operates. Then, an overcurrent signal is output to the control side, and the gate voltage is lowered with a predetermined time constant to reduce the overcurrent. Application of the gate voltage is then stopped in response to a stop (off command) signal from the control side. The voltage application is not stopped, but the overcurrent is sufficiently reduced before being cut off.

Therefore, even if an overcurrent is detected immediately before a stop (off command) signal, element destruction can be prevented without directly interrupting the overcurrent.

〔Example〕

The present invention will be described in detail below based on embodiments with reference to the drawings.

FIG. 1 shows one embodiment of the present invention, which is an example applied to an electrostatic induction type self-extinguishing element IGBT. The voltages of the gate power supplies 1 and 2 are connected to the IG via an NPN transistor 7, a PNP transistor 8, and a resistor 9, which are connected conjointly.
It is applied to the gate of BTIO, and the common base of transistors 7.8 is connected to the collector of NPN transistor 5. The base of the transistor 5 is connected to the collector of the phototransistor 3, and IGBTIO is turned on by giving an on/off command signal to the base of the transistor 3.

It constitutes a drive circuit that controls the off state.

Further, the gate and collector of IGBTIO are connected through a resistor 11 and a diode 12, and the connection point between the resistor 11 and the diode 12 is connected to the base of a transistor 15 through a Zener diode 14, and when a gate voltage is applied to IGBTIO, An isometric overcurrent detection circuit is constructed to detect the level of the collector voltage of the circuit.

Next, the collector of the transistor 15 is connected to the photocoupler 16
, resistor 17 and diode 18 to transistor 7.
A capacitor 19 is connected to the connection point between the resistor 17 and the diode 18. This transfers the overcurrent detection signal to the control side and constitutes a gate voltage adjustment circuit.

A resistor 20 and a capacitor 21 are connected to the emitter of the transistor 15, and one end of the capacitor 21 is connected to the base of the transistor 23.
The collector of the transistor 3 is connected to the collector of the transistor 3 to form an on-holding circuit.

Next, the operation of this circuit will be explained with reference to the time chart shown in FIG.

First, transistor 3 is activated at time t by a signal from the control side.
When the transistor 5 is turned on at o, the base current stops and the transistor 5 is turned off. As a result, the transistor 7
A base current flows through the NPN transistor 7, turning on the NPN transistor 7, and supplying current to the gate of the IGBTIO via the resistor 9. IGBTIO is turned on after the gate-emitter capacitance is charged to a predetermined value.

Note that during the normal on-period, a part of the gate current also flows through the resistor 11 and diode 12 to the collector of IGBTIO. This is to flow the current to the base of the transistor 15 and turn on the transistor 15 when the collector current of the IGBTIO becomes an overcurrent and the collector voltage becomes high. At the early stage of turn-on,
Due to the turn-on delay (tl) of IGBTIO, the collector voltage is high and the same state as an overcurrent occurs, but a detection delay is created by the capacitor 13 to prevent the overcurrent detection circuit from operating.

Overcurrent detection continues after the inspection delay time determined by this resistor 11, capacitor 13, and Zener diode 14.
This is performed only when the collector voltage of TIO is higher than a predetermined voltage. This is the ON state of the transistor 15 mentioned above (
t3).

When transistor 15 turns on (t3), capacitor 1
9 starts discharging through resistor 17, 22 and photocoupler 16. Then, the base voltage of the transistor 7 eventually decreases to a value determined by the ratio of the resistor 6, the resistor 17, and the resistor 22. However, the voltage does not fall below the detection level of the Zener diode 14.

As described above, by lowering the gate voltage of IGBTIO with the time constant of CR, the overcurrent is gradually reduced and a stop (off) command signal from the control side is waited for. The feature is that even if a stop signal (t4) is received from the control side prior to the stop signal, that is, while the gate voltage is decreasing, the circuit maintains the on state until the gate voltage drops to a predetermined value (t5). This is what we have in place.

This is achieved by resistors 22 and 24 and capacitors 2
1. An on-holding circuit composed of a transistor 23.

When the transistor 15 of the overcurrent detection circuit is turned on (t3), a base current initially flows to the transistor 23 via the capacitor 21, and the on-holding circuit operates. Then, as time passes, the capacitor 21 is charged with electric charge, and the capacitor 19 is discharged and the collector current of the transistor 15 becomes smaller.As the current at the base of the transistor 23 becomes smaller, the collector voltage of the transistor 23 rises and the on-holding circuit is activated. Stop (tδ).

In this way, by flowing the base current to the transistor 23 and turning it on only for a predetermined time when the overcurrent detection circuit operates, even if an off signal is received from the control side during this period and the transistor 3 is turned off (ta). Even though
The on state is maintained until the gate voltage of IGBTIO falls to a predetermined value.

As described above, in the present invention, after an overcurrent is detected, priority is given to reducing the gate voltage to a predetermined value over the control signal, so that an excessive current can always be slowly reduced and then shut off. For this reason, it is possible to prevent the occurrence of a voltage jump when turned off, such as when an overcurrent is cut off, and it is possible to prevent element destruction.

FIG. 2 is a circuit diagram showing a second embodiment of the present invention. Components with the same functions as those in FIG. 1 are denoted by the same reference numerals. 1st
The method for detecting overcurrent connected to the collector of IGBTIO is different from the figure. In the embodiment shown in FIG. 1, the value of the gate voltage to be narrowed down could not be made smaller than the level at which overcurrent is determined. In this embodiment, since the detection circuit and the gate voltage narrowing down circuit are separate, the detection level and the final gate voltage for narrowing down can be individually selected.

FIG. 3 is a circuit diagram showing a third embodiment of the present invention. In FIG. 2, a diode 29 is inserted between the collector of the transistor 27 and the gate of IGBTIO, and a diode 30 is inserted between the gate and the positive electrode of the gate power supply.

The former has the feature that reverse bias can be applied without using the resistor 9 during the off-time reverse bias period, and a stable reverse bias can be obtained2, making it possible to lower the reverse bias voltage.

As a result, the loss of the drive circuit can be reduced.

The latter clamps the maximum value of the gate voltage during the on period to the gate power supply voltage.According to the inventor's experiments, when the IGBTIO is in the on state and the inverter arm is short-circuited or the load is short-circuited, In a state where an overcurrent flows, the collector current increases excessively and the collector voltage also increases. When the collector voltage increases, the gate voltage is charged from the main power supply side to a voltage higher than the gate power supply voltage via the capacitance between the collector and the gate. For this reason, there is a problem that the collector current increases again, and this problem is prevented.

FIG. 4 is a circuit diagram showing a fourth embodiment of the present invention. The position of the photocoupler 16 for transferring the overcurrent detection signal to the control side is different from that in FIG. 3. In this way, the control side can grasp the period during which the gate voltage is applied and the collector voltage is low, that is, the energization width, so that control performance can be improved.

In the overcurrent protection circuits of the first to fourth embodiments of the present invention, the overcurrent detection diode 12 is connected to the collector of IGBTlo. Having the high voltage portion close to the gate circuit is disadvantageous in terms of noise.

FIG. 6 is a diagram schematically showing a cross section of the IGBT.

Inside the IGBT, small-capacity IGBTs called cells are connected in parallel through multiple electrodes. As shown in the figure, the cathode electrode of one cell is separated, and a diode 12 for overcurrent detection is provided inside the IGBT.

By providing the IGBT itself with a terminal for overcurrent detection in this way, the number of high-voltage portions approaching the gate circuit is reduced, so that the reliability of the gate circuit against noise can be improved.

Figure 8 shows a circuit diagram of a three-phase voltage source inverter device, 3
The phase inverter has one arm consisting of two series-connected IGBT switches (S1 + S4. The inductive conductor IM, which is a load, is connected to the switch connection point of a IGBTSt* St, S.
ll, S4. S5. S8 each has the overcurrent protection circuit shown in the first to fourth embodiments of the present invention,
In FIG. 8, the protection circuit is omitted.

〔Effect of the invention〕

As described above, in the present invention, after an overcurrent is detected, priority is given to lowering the gate voltage to a predetermined value rather than a stop signal from the control side, so the overcurrent is always reduced and cut off, preventing element destruction. I can do it.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention, FIG.
FIGS. 3 and 4 show the second embodiment of the present invention. 3゜A circuit diagram showing the fourth embodiment, FIG. 5 is a characteristic diagram of the IGBT, and FIG. 6 is a sectional view of the IGBT in the first to fourth embodiments of the present invention.
FIG. 7 is a time chart showing the operation of the first @, and FIG. 8 is a diagram showing an example of the configuration of an inverter device according to an embodiment of the present invention. 1.2...DC power supply, 3,5,7,8,15,23゜27...Transistor, 4,6,9,11,17゜20
．． 22.24, 25, 26.28...Resistance, 10...
- IGBT, 12, 18, 29, 30... Diode, 13, 19.21... Capacitor, 14... Zener diode, 16... Photocoupler. tot tz t3i, tp ts

Claims (1)

[Claims] 1. A constant voltage power source; an electrostatic induction type self-extinguishing element having a collector, an emitter, and a gate; a gate voltage input circuit for applying the generated voltage to the gate of the electrostatic induction type self-extinguishing element; , means for applying a voltage to the gate of the electrostatic induction type self-extinguishing element to keep the electrostatic induction type self-extinguishing element on until the gate voltage decreases to a predetermined value. Drive circuit for inductive self-extinguishing element. 2. A constant voltage power supply, an electrostatic induction type self-extinguishing element having a collector, an emitter, and a gate, and a voltage generated from the constant voltage power supply according to the magnitude of the input on/off command signal. A gate voltage input circuit that applies to the gate of the electrostatic induction self-extinguishing element, and when the collector voltage of the electrostatic induction self-extinguishing element is equal to or higher than a predetermined value, reduce the gate voltage so that the gate voltage reaches a predetermined value. According to the magnitude of the off command signal, the voltage generated from the constant voltage power supply is not applied to the gate of the electrostatic induction self-extinguishing element until the voltage decreases to the value of . and means for applying a voltage that keeps the element on to the gate of the electrostatic induction self-turning off element. 3. A constant voltage power supply, an electrostatic induction type self-extinguishing element having a collector, an emitter, and a gate, and a voltage generated from the constant voltage power supply according to the magnitude of the input on/off command signal to be connected to the static A gate voltage input circuit that applies to the gate of the electrostatic induction self-extinguishing element, and when the collector voltage of the electrostatic induction self-extinguishing element is equal to or higher than a predetermined value, reduce the gate voltage so that the gate voltage reaches a predetermined value. and a circuit for maintaining the on-state of the electrostatic induction self-turn-off element until the value of the electrostatic induction self-turn-off element decreases to a value of . 4. A device that supplies a gate voltage to the gate of an electrostatic induction type self-extinguishing element in response to an on/off command signal, comprising means for lowering the gate voltage when the collector voltage of the self-extinguishing element exceeds a predetermined value. 1. A drive circuit for an electrostatic induction self-extinguishing element, characterized in that it cannot be turned off by an on/off command signal until the gate voltage drops to a predetermined value. 5. The electrostatic capacitor according to any one of claims 1 to 4, wherein the drive switch for supplying the gate voltage is driven by both an on/off command signal and a signal from overcurrent detection. Drive circuit for inductive self-extinguishing element. 6. The electrostatic induction type self-extinguishing device according to any one of claims 1 to 4, wherein the gate voltage is not charged from the collector side of the self-extinguishing element to a level higher than a predetermined gate voltage. Arc element drive circuit. 7. Claims 1 to 4, characterized in that the gate voltage is clamped using a diode as a power source of the gate circuit.
A drive circuit for an electrostatic induction self-extinguishing element according to any one of the above. 8. An electrostatic induction type self-extinguishing element with a collector voltage detection terminal, characterized in that a part of the emitter in the self-extinguishing element is divided and used for collector voltage detection. 9. The drive circuit for an electrostatic induction type self-extinguishing element according to any one of claims 1 to 4, characterized in that the width of the ON signal is widened until the gate voltage drops to a predetermined value. 10. Between the gate power supply and the gate terminal of the self-extinguishing element,
1. A drive circuit for an electrostatic induction type self-extinguishing element, characterized in that it is provided with means for bypassing when the gate terminal voltage becomes higher than the gate power supply voltage. 11. Any one of claims 1 to 4, characterized in that a resistor and a diode are connected in series between the gate terminal and the collector terminal of the self-extinguishing element, and the potential at the connection point is used as a comparison signal. A drive circuit for an electrostatic induction type self-extinguishing element as described above. 12. A comparison signal generation circuit is provided separately from a gate voltage generation circuit that supplies the gate terminal of the self-extinguishing element, and a resistor and a diode are connected in series between the comparison signal and the collector terminal of the self-extinguishing element; 5. A drive circuit for an electrostatic induction type self-extinguishing element according to claim 1, wherein the potential at the connection point is used as a comparison signal. 13. The drive circuit for a static induction type self-turning element according to claim 12, wherein the comparison signal generating circuit and the gate terminal of the self-turning off element are connected via a diode. 14, comprising first, second, and third constant voltage power supplies, a load, a collector, an emitter, and a gate, with a collector-emitter current path connecting one terminal and the other terminal of the third constant voltage power supply; first and second electrostatic induction type self-extinguishing elements connected in series between them and a load connected to the connection point; a first gate voltage input circuit that applies a voltage generated from a constant voltage power source to the gate of the first electrostatic induction type self-extinguishing element; a second gate voltage input circuit that applies a voltage generated from a second constant voltage power supply to the gate of the second electrostatic induction self-extinguishing element; When the collector voltage is above a predetermined value, the gate voltage of the first electrostatic induction self-extinguishing element is lowered, and the gate voltage is lowered according to the magnitude of the OFF command signal until the gate voltage is reduced to a predetermined value. 1st above
means for applying a voltage generated from a constant voltage power source to the gate of the first electrostatic induction self-turning element without applying it to the gate of the first electrostatic induction self-turning element; When the collector voltage of the second electrostatic induction type self-extinguishing element is equal to or higher than a predetermined value, the gate voltage of the second electrostatic induction type self-extinguishing element is lowered, and the gate voltage is reduced to a predetermined value. up to the second turn according to the magnitude of the off command signal
Without applying the voltage generated from the constant voltage power source to the gate of the second electrostatic induction self-turn-off element, the voltage at which the second electrostatic induction self-turn-off element continues to be turned on is applied to the second electrostatic induction self-turn-off element. An inverter device having an electrostatic induction type self-extinguishing element, comprising means for applying voltage to the gate of the electrostatic induction type self-extinguishing element.