JPH11113265A - Invfrter device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inverter device which is constituted so that the inverter device may always surely suppress the occurrence of a surge voltage and may prevent the breakdown of IGBTs(insulated gate bipolar transistors), even when the detecting level of a short-circuit detecting circuit fluctuates. SOLUTION: An inverter device is constituted in such a way that an OR circuit 30 which inputs abnormal current detecting signals from outputs B provided to all driving circuits 15-20 of IGBTs 3-8 is provided, gradually decreasing operation signals outputted from the OR circuit 30 are supplied to inputs C provided to all driving circuits 15-20 and, when a short circuit is detected in any one of the IGBTs 3-8, all IGBTs 3-8 are softly controlled for constriction and slowly turned off from turned-on states. Since the IGBTs 3-8 in all phases are softly controlled for gradual decrease even when an abnormal large current caused by an output short circuit, etc., is detected in any phase, the possibility of occurring surge voltages in the IGBTs which are in the other phase than the phase in which the abnormal current is detected can be eliminated even when the detecting level of the abnormal current fluctuates.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter device using an IGBT (insulated gate bipolar transistor) as a switching element of a main circuit, and more particularly to an inverter device having a short-circuit current protection function when an output is short-circuited. Related to the device.

[0002]

2. Description of the Related Art In recent years, as a main circuit switching element,
Inverter devices using IGBTs are widely used. In such inverter devices using IGBTs, as a protection method when the output is short-circuited, a short-circuit current is quickly detected and a gate voltage is gradually reduced. Conventionally, a so-called soft aperture control method of controlling switching of a switching element by an appropriate aperture has been mainly employed.

[0003] This is because the switching speed of the IGBT is high, so that the IGB caused by the passage of a large current when an output short circuit occurs.
This is because not only the risk of T breakdown but also the surge voltage generated by the interruption of the current exceeds the breakdown voltage of the IGBT, which may cause the breakdown.

This surge voltage is caused by the current change rate di / dt and the wiring inductance when the current is interrupted. If a large current such as a short-circuit current is interrupted at a normal switching speed of the IGBT, A large surge voltage exceeding the breakdown voltage of the IGBT easily occurs.

Therefore, in order to suppress this surge voltage,
When a short-circuit current is detected, as described above, the gate voltage of the IGBT is gradually reduced, thereby gradually decreasing the current of the IGBT, suppressing the current change rate di / dt at the time of interrupting the current, and reducing the surge voltage. They try not to grow.

By the way, in the inverter device according to the prior art, as shown in FIG. 4, all the gate drive circuits 15 to 20 of the IGBTs 3 to 8 which are the switching elements of the main circuit.
A protection circuit is provided for each switching element to detect a short-circuit current independently for each switching element, and to protect each of the IGBTs 3 to 8 from a short-circuit current flow and a surge voltage caused by interruption of the short-circuit current.

In the inverter device according to the prior art shown in FIG. 4, 1 is a rectifier circuit, 2 is a smoothing capacitor, 3 to 8
Is an IGBT, 9 to 14 are flywheel diodes, 1
5 to 20 are IGBT drive circuits (gate drive circuits), 21
Is a short-circuit detecting diode, and 22 is an inverter control circuit. Reference numeral 23 denotes a switch provided on the assumption that the output is short-circuited, and reference numeral 24 denotes a wiring inductance, which will be described later in detail.

The rectifier circuit 1 is composed of six diodes connected in a three-phase bridge as shown in the figure, and converts three-phase AC power supplied from a three-phase AC power source into DC power, and supplies the DC power to a smoothing capacitor 2. While charging, 6 IGBT3 ~
8 serves to supply DC power to a main circuit having a switching element.

Thus, during normal operation, each of the drive circuits 15 to 20 controls the switching of each of the IGBTs 3 to 8 in accordance with the PWM signal supplied from the higher-order inverter control circuit 22, and each of the U, V, W A three-phase AC power is generated at an output terminal, and the three-phase AC power is supplied to a load such as a motor connected to the output terminals U, V, and W.

On the other hand, when each of the driving circuits 15 to 20 detects the short-circuit current of each of the IGBTs 3 to 8 by the diode 21, as described above, the gate voltage of the IGBT is controlled by soft aperture control, and when the current is cut off. Current change rate di / d
t is suppressed so that the surge voltage does not increase, an alarm signal is output from the output A, and the alarm signal is supplied to the inverter control circuit 22.

In response to this alarm signal, the inverter control circuit 22 sends a signal to each of the drive circuits 15 to 20 in response to the alarm signal.
The transmission of the WM signal is stopped, whereby the emergency stop of the inverter device is performed, so that the protection of the device can be obtained. Next, FIG. 5 shows an example of modularized drive circuits 15 to 20 which are generally used at present. Here, since each of the drive circuits 15 to 20 has the same configuration, only the drive circuit 15 and the drive circuit 20 are shown, and the others are omitted.

The driving circuits 15 and 20 include gate driving circuits 150 and 200 and short-circuit detecting circuits 151 and 201, respectively.
It comprises gate aperture circuits 152 and 202 and alarm output circuits 153 and 203. Hereinafter, IGBT3
The drive circuit 15 of FIG. Gate drive circuit 1
50 is the P supplied from the inverter control circuit 22.
The WM signal is amplified in an electrically isolated state, and the IGBT3
Acts to drive the gate of the

The short-circuit detection circuit 151 functions to detect a short-circuit current flowing through the IGBT 3. When the IGBT 3 is on (conducting), a voltage appearing between its collector and emitter, that is, a collector-emitter voltage is detected. The short circuit current is detected by taking in through the diode 21.

When the IGBT is in the ON state, normally, a detection current flows from the short-circuit detection circuit 151 to the IGBT 3 via the detection diode 21, but when the collector-emitter voltage of the IGBT 3 becomes higher than a specified value, The diode 12 is turned off so that no current flows. When the current stops flowing, the IGBT 3
It is determined that a short-circuit current is flowing through the switch.

In the IGBT, when a large current flows through the IGBT due to an output short circuit or the like, the operation region shifts from the saturation region to the active region, and the collector-emitter voltage rises sharply. It is a thing that uses something.

When a short-circuit current is detected, the gate aperture circuit 152 starts operating in response to a signal supplied from the short-circuit detection circuit 151, gently narrows the gate drive signal as described above, and slowly turns the IGBT 3 from on to off. The soft throttle control for shifting to (interruption) is executed, thereby functioning to prevent generation of a surge voltage.

The alarm output circuit 203 operates in response to a signal supplied from the short-circuit detection circuit 151 when a short-circuit current is detected, and functions to supply an alarm signal to the inverter control circuit 22 via the photocouplers 154a and 154b. . Here, 154a of the photocoupler represents a light emitting side, and 154b represents a light receiving side.

Next, the inverter control circuit 22 includes a control circuit 220, a PWM output circuit 221, and an abnormal signal input circuit 222. The control circuit 220 is constituted by a microcomputer or the like, and executes processing necessary for controlling the entire inverter. The PWM output circuit 221 includes:
As the name implies, it functions to generate a PWM signal necessary for controlling the switching of the IGBT.

The abnormal signal input circuit 22 inputs an alarm signal from the light receiving side 154b of each photocoupler,
An abnormal signal is generated, and the control circuit 220 and the PWM output circuit 2
21 to stop the generation of the PWM signal when an overcurrent is detected. Here, the reason why the photocouplers 154a and 154b are used for transmitting the alarm signal is as follows.
This is to obtain electrical isolation.

[0020]

SUMMARY OF THE INVENTION The above prior art is based on each I
No consideration is given to the fact that the detection level of the short-circuit current of the GBT is inevitable, and as described below, there is a problem in sufficiently suppressing the surge voltage.

In the inverter device, when its output is short-circuited, the short-circuit current passes through at least two upper and lower IGBTs. Therefore, a short-circuit current protection mechanism may be incorporated in each IGBT drive circuit as described above, and each IGBT drive circuit through which the short-circuit current passes may perform a protection operation.

However, the detection level of the short-circuit current
It is almost impossible in practice to make the GBT completely equal, and the existence of variations is inevitable.
When a short circuit occurs, some of them perform a detection operation and others do not. As a result, in the IGBT in which the detection level is low and the detection circuit operates, a large surge voltage is not generated because the gate voltage is softly throttled. However, in the IGBT in which the detection level is high and the detection circuit operates properly, the gate voltage is low. The aperture does not work, and a large current is cut off at a normal switching speed.

Accordingly, in the prior art, a large surge voltage is generated in the IGBT in which the detection circuit does not work, and there is a risk of causing a breakdown voltage breakdown. The inverter device and the operation thereof will be described with reference to the timing chart of FIG.

First, here, the IGBT 3 and the IGBT 8 are on, the other IGBTs are off,
In addition, it is assumed that the short-circuit current detection level by the drive circuit 15 of the IGBT 3 is lower than the short-circuit current detection level by the drive circuit 20 of the IGBT 8. Next, assuming that a short circuit occurs between the output terminal U and the output terminal W, it is assumed that the switch 23 is closed.

In the timing chart of FIG. 6, I ₂₃ is a current flowing through the switch 23 and I ₃ is an IGB
The current flowing through T3, I ₈ is the current flowing through IGBT ₈ ,
₁₂ the current through the diode 12, VG ₃ is IGBT
3, VCE ₃ is the voltage between the collector and the emitter of the IGBT ₃ , VG ₈ is the gate voltage of the IGBT ₈ , V
CE ₈ indicates the collector-emitter voltage of the IGBT ₈ .

Assuming that the switch 23 is turned on at time t ₀ and a short circuit occurs, the IGBT 3
And the short-circuit current I ₂₃ starts flowing through the IGBT 8,
The short-circuit current I ₂₃ is limited by the wiring inductance 24, as a result, as shown, will become gradually larger rises at time t _0. Incidentally, at this time, the short-circuit current I ₂₃ is equal to the current I ₃ flowing through the IGBT 3.

Then, time t ₁ is reached. Here, the short-circuit current I ₂₃ is changed to the IGBT 3 whose short-circuit current detection level is lower.
It is assumed that the detection level of the drive circuit 15 has been reached. Then, here, the drive circuit 15 ignores the PWM signal supplied from the higher-order inverter control circuit 22 and ignores the IGB signal.
The gate voltage VG ₃ of T3, as shown in portion 25, Yuki squeezed gently, thereby controlling the slow off IGBT 3.

As a result, the current I ₃ is cut off relatively slowly, as indicated by the portion 26, so that the voltage VCE ₃
Does not generate a large surge voltage, only with a small surge voltage as shown in section 27,
With respect to the IGBT 3, there is no fear that the withstand voltage is threatened.

However, even if the IGBT 3 is cut off, the IGBT 8 remains on, so that the short-circuit current I ₂₃
The remaining by the action of the wiring inductance 24, commutated and the return current I ₁₂ becomes a diode 12, which is the short-circuit current I _23. As a result, the short-circuit current I ₂₃ remains after time t _1, but thereafter only decreases as shown in the figure, so that the drive circuit 20 of the IGBT 8 remains in a state where it does not reach the detection level, and the short-circuit current I ₂₃ I ₂₃ is than while gradually decay, but continues to flow still.

By the way, the drive circuit 15 that has detected the short circuit at the time t ₁ , at this time,
, And the inverter control circuit 22 responds to this alarm signal at time t _2.
Stops the output of the PWM signal to all of the drive circuits 15 to 20, and thereby the drive circuit 20 stops the output of the PWM signal, thereby stopping the gate voltage VG ₈ of the IGBT _8.
, As shown in a portion 28, as in the normal operation, abruptly enters the cutoff state while maintaining the high switching speed.

As a result, at time t ₂ , IGBT 8 is turned off, and its collector-emitter voltage VCE ₈ has a portion 29
As shown in FIG.
The breakdown voltage is exceeded, causing destruction. here,
The reason why the currents I ₁₂ and I ₂₃ continue to flow for a while after time t ₂ is that the IGBT 8 is commutated to the diode 11.

In FIG. 6, the time t ₁ to the time t ₁
The time to ₂ is drawn quite long, but is exaggerated for clarity, and is actually shorter, with the shortest delay required to process the signal. Not just.

It is an object of the present invention to provide an inverter device capable of always suppressing generation of a surge voltage and preventing breakdown voltage breakdown of an IGBT even if the detection level of a short-circuit detection circuit varies. It is in.

[0034]

An object of the present invention is to provide an inverter device which uses an IGBT as a main circuit switching element and has an abnormal current detection circuit and a gate voltage soft aperture control circuit in a gate drive circuit of each switching element. An OR circuit for inputting an abnormal current detection signal from all the abnormal current detection circuits of the drive circuit is provided, and the output of the OR circuit causes all the soft aperture control circuits of the gate drive circuit to operate. You.

Even if an abnormally large current due to an output short circuit or the like is detected in any phase, the IGBTs of all phases are subjected to the soft throttle control.
The possibility that a surge voltage is generated even in the GBT can be eliminated.

[0036]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an inverter device according to the present invention will be described in detail with reference to the illustrated embodiments. FIG. 1 shows an embodiment of the present invention.
The remaining components are the same as those shown in FIG. 4 except that each of the driving circuits 15 to 20 has an output B and an input C in addition to the output A. Is the same as the inverter device.

In the drive circuits 15 to 20, first, the output B is a signal representing an abnormal large current such as a short circuit, which is separate from the alarm signal output A, ie, a short circuit detection signal (abnormal current detection signal). ), And the input C is a terminal for inputting a signal for forcibly operating an internal gate aperture circuit, that is, an aperture operation signal.

Therefore, the driving circuit 1 in this embodiment
Reference numerals 5 to 20 denote gate aperture circuits provided inside the corresponding IGBTs 3 to 8 when a short-circuit current is detected.
In addition to operating the (soft aperture control circuit), even when a predetermined signal, that is, an aperture operation signal, is supplied to the input C from the outside, the gate aperture circuit inside is configured to operate. Will be.

Next, the OR circuit 30 is constituted by a 6-input OR circuit, and its inputs are connected to the drive circuits 15 to 15 of all phases.
A short-circuit detection signal is supplied from an output B of the output circuit 20. The OR operation results are output from the output B and supplied to all inputs C of the drive circuits 15 to 20 as an aperture operation signal. .

Therefore, in the embodiment of FIG. 1, when a short-circuit current is detected in the corresponding IGBT in any of the drive circuits 15 to 20, the aperture operation is performed on all of the remaining drive circuits 15 to 20. Signal, so that the IGBT3
When a short-circuit current flows in any one of the IGBTs 8 to 8, the gate throttle circuits in the drive circuits of all the IGBTs are operated, and the gate voltages of the corresponding IGBTs are gradually reduced and turned off.

Next, the operation of this embodiment will be described with reference to FIG.
This will be described with reference to the timing chart of FIG. At this time, as in the case of the prior art of FIG. 6, the IGBT 3 and the IGBT 8 are on, the other IGBTs are off, and the short-circuit current detection level by the drive circuit 15 of the IGBT 3 is higher than the IGBT 8 It is assumed that the switch 23 is closed at time t ₀ and a short circuit occurs between the output terminal U and the output terminal W in this state.

Then, similarly to the prior art, the drive circuit 15 detects a short circuit at time t ₁ , whereby the gate voltage VG ₃ is gradually reduced and the IGBT ₃ is reduced, as shown in a portion 25 in the figure. Slowly transition to shutoff.
Therefore, similarly to the prior art, the current I ₃ is cut off relatively slowly after the time t ₁ , as shown by the portion 26, so that the voltage VCE ₃ has a small surge voltage as shown by the portion 27. Along with this, a large surge voltage is not generated, and therefore, there is no possibility that the breakdown voltage of the IGBT 3 is threatened.

By the way, as described in the prior art, the IGBT 8 is suddenly cut off at a time t ₂ while maintaining the high switching speed.
There is a risk of breakdown with pressure.
In the embodiment, the drive circuit 15 detects the short circuit of the IGBT 3 and operates its own gate aperture circuit, sends out a short circuit detection signal from its output B, and sends it to the OR circuit 30.
As a result, at time t _{1 ′,} which is a short time after the drive circuit 15 detects the short circuit at time t ₁ , the aperture operation signal is supplied to the inputs C of all the drive circuits. Is done.

Therefore, the driving circuit 20 of the IGBT 8 is
Also operates the gate aperture circuit of FIG.
The gate voltage VG8 of the GBT ₈ is gradually reduced. As a result, after the time t ₁ ′, the current I _{8 of} the IGBT ₈
Is also shut off relatively slowly, as indicated by section 41, and thus the collector-emitter voltage V
CE ₈ also has only a small surge voltage as shown in the portion 42, and no large surge voltage is generated.

As a result, after that, at time t ₂ , the inverter control circuit 22 switches the PWM
Even if the generation of the signal is stopped, there is no danger that a surge voltage will be generated anymore. Of course, there is no danger that the withstand voltage of the IGBT 8 will be threatened. Therefore, according to this embodiment, , IGB which is a main circuit switching element
T destruction can always be reliably prevented.

Next, an embodiment of the present invention in which each of the driving circuits 15 to 20 including the OR circuit 30 is realized using a generally used IGBT driving module will be described.
This will be described with reference to FIG. In this embodiment, the driving circuits 15 to 20 have the same configuration.
, Only the drive circuit 20 is shown, and the others are omitted.

The embodiment shown in FIG. 3 is different from the prior art circuit shown in FIG. 5 in that each of the driving circuits 15 to 20 is further provided with a photocoupler 155 to 205 and a photocoupler 156 to 2.
06 is provided so that the function of the OR circuit 31 is obtained. Therefore, except that these photocouplers are added, the circuit is the same as the circuit of FIG.

In this embodiment, each driving circuit 1
As a method of operating the gate aperture circuits 152 and 202 with an aperture operation signal supplied from the outside in 5 to 20, a photocoupler 156 is connected to the detection input of the short-circuit detection circuits 151 and 201.
To 156b and 206b of the light receiving side of
The method employs a method in which a detection signal is cut off to forcibly cause a state where a short circuit is detected.

As described above, the driving circuits 15 to 20
The operation of detecting the short-circuit current of the IGBTs 3 to 8 by the short-circuit detection circuits 151 and 201 detects the voltage between the collector and the emitter of each IGBT, and determines that an abnormality occurs when the current stops flowing from the detection terminal to the collector of the IGBT. It has become.

Therefore, in this embodiment, the light receiving side 156b of the photocouplers 156 to 206 is utilized by utilizing this.
06b, the drive circuit 1
5 to 20 inputs are turned on and off. As a result, the modularized drive circuits 15 to 20
The advantage is that the device can be used as it is without tweaking the inside of the device.

For this reason, first, the photocouplers 155-2
05 are connected to the outputs of alarm output circuits 153 to 203, respectively, and the light emitting sides 154a to 154 of photocouplers provided for transmitting alarm signals are connected.
4a in series. As a result, the light emitting sides 155a to 205a of these photocouplers
201 detects a short circuit, and outputs an alarm output circuit 153-2.
03 generates an alarm signal, the photocoupler 154
The light-emitting sides 154a to 204a emit light simultaneously.

Next, these photocouplers 155-20
The light receiving sides 155b and 205b of the fifth line 5 are commonly connected to a line 50, and further commonly connected to a power supply Vcc via a series resistor 51. And another photo coupler 156-2
The light-emitting sides 156a to 206a of 06 are connected in parallel to the line 50 via respective series resistors 157 and 207.

As a result, the light emitting sides 156a to 206a of the photocouplers 156 to 206 always emit light, and the light receiving sides 156b and 206b are turned on.
Light receiving side 155b, 205 of photocouplers 155-205
When any one of b is turned on, the potential of the line 50 becomes low level, so that the light emitting sides 156a to 206a of the photocouplers 156 to 206 all stop emitting light, and the light receiving sides 156b and 206b are turned off. Would be done.

Accordingly, the light receiving side 156b of the photocouplers 156 to 206 at the detection input of each of the drive circuits 15 to 20,
The on / off operation of the 206b is performed by the alarm output circuit 153.
203 are obtained as OR logic conditions of the alarm signals, and the function as the OR circuit 31 can be obtained.

[0055] The operation of the embodiment of FIG. 3, to describe the timing diagram of FIG. 2, the first time t ₁ earlier, since all the light-emitting side 156a~206a of the photocoupler 156 to 206 are light-emitting operation, the Light receiving side 156b, 20
6b is in the ON state, and accordingly, each of the driving circuits 15 to 20
The short-circuit current detection function is maintained as it is. Therefore, when a short circuit occurs in the IGBT ₃ at time t ₁ , the detection function of the short circuit detection circuit 151 of the drive circuit 15 immediately works, and as a result, the gate aperture circuit 152 and the alarm output circuit 153 operate.

Therefore, the light emitting side 15 of the photocoupler 155
5a emits light, and the light receiving side 155b thereof is turned on.
56a to 206b are all turned off. As a result,
Light receiving sides 156b to 206 of photocouplers 156 to 206
Since all of b are turned off, the input of the short-circuit detection circuit 201 of the drive circuit 20 is electrically disconnected from the diode 21.

[0057] Thus, the short circuit detecting circuit 201 is in a state of detecting a forced short circuit operates gate aperture circuit 202 from time t ₁ at a predetermined delay time has elapsed time t ₁ after ', the portion 40 As shown, the gate voltage VG8 of the IGBT ₈ is gradually reduced. As a result, this time t
_{After 1} ′, the current I _{8 of} the IGBT ₈ is also cut off relatively slowly, as indicated by the part 41, and thus the IGBT 8
The collector-emitter voltage VCE _{8 of FIG. 1} also involves only a small surge voltage as shown in the portion 42, and short-circuit protection can be reliably obtained without generating a large surge voltage.

Therefore, according to this embodiment, when a short circuit occurs, the gate throttle circuits 152 to 202 can be operated in the drive circuits 15 to 20 of all phases, so that the surge voltage at the time of the short circuit occurs Suppress the occurrence of
It is possible to eliminate the possibility that the IGBTs 3 to 8 are exposed to a high voltage exceeding the breakdown voltage, and to reliably protect the inverter device from an output short circuit.

[0059]

According to the present invention, when the output short-circuit of the inverter device is detected, in any case, the IGBTs of all the phases are always turned off under the soft throttle control. In addition, even if the detection level of the abnormal current varies, the generation of the surge voltage can always be surely suppressed. As a result, according to the present invention, the protection function is reliably exerted even when the output is short-circuited, and it is possible to protect the IGBT from easily providing a highly reliable inverter device that is not likely to be subjected to withstand voltage breakdown.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of an inverter device according to the present invention.

FIG. 2 is a timing chart for explaining the operation of one embodiment of the present invention.

FIG. 3 is a block diagram illustrating a specific example of a drive circuit according to an embodiment of the present invention.

FIG. 4 is a circuit diagram illustrating an example of an inverter device according to the related art.

FIG. 5 is a block diagram showing a specific example of a drive circuit in an inverter device according to the related art.

FIG. 6 is a timing chart for explaining the operation of the conventional inverter device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Rectifier circuit 2 Smoothing capacitor 3-8 IGBT (insulated gate bipolar transistor) 9-14 Flywheel diode 15-20 Drive circuit (gate drive circuit) 21 Diode for short circuit detection 22 Upper inverter control circuit 23 Switch for assumption 24 Wiring inductance 30 OR circuit (OR circuit)

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hiroshi Chiba 7-1-1, Higashi Narashino, Narashino-shi, Chiba Industrial Equipment Division, Hitachi, Ltd. (72) Inventor Mutsuo Tokashiki 7-1-1 Higashi-Narashino, Narashino-shi, Chiba No. 7 Industrial Equipment Division, Hitachi, Ltd. (72) Inventor Satoko Ishii 7-1-1 Higashi Narashino, Narashino City, Chiba Prefecture (72) Inventor Masayuki Hirota 7-1, Higashi Narashino, Narashino City, Chiba Prefecture No. 1 Hitachi Keiyo Engineering Co., Ltd.

Claims (1)

[Claims] An insulated gate is used as a main circuit switching element.
In an inverter device using a bipolar transistor and having an abnormal current detection circuit and a gate voltage soft aperture control circuit in the gate drive circuit of each switching element, an abnormal current detection signal is output from all the abnormal current detection circuits of the gate drive circuit. An inverter device, comprising: an input OR circuit; and an output of the OR circuit configured to operate all of the soft aperture control circuits of the gate drive circuit.