JP6590437B2 - Semiconductor power converter - Google Patents

Description

  The present invention relates to a semiconductor power conversion device having a function of protecting a semiconductor switch from a short circuit failure.

  In a semiconductor power converter, as a protection circuit for a semiconductor switch when an arm is short-circuited, a circuit in which a fuse is connected in series to the semiconductor switch and a short-circuit current is cut off by blowing the fuse is generally used. Recently, however, various circuits for protecting a semiconductor switch without using a fuse have been provided in order to reduce the inductance of the device and reduce the number of components.

  For example, FIG. 4 is a block diagram conceptually showing the protection circuit of the semiconductor switch (IGBT) described in Patent Document 1, FIG. 5A is an operation waveform at the time of normal switching in FIG. b) is an operation waveform when the semiconductor switch in FIG. 4 is short-circuited.

In FIG. 4, reference numeral 100 denotes a drive circuit that generates a gate signal for the semiconductor switch T, and reference numeral 200 denotes a main circuit of the power conversion apparatus having the semiconductor switch T.
The drive circuit 100 includes a V _ce detection circuit 101 that monitors the collector-emitter voltage V _ce of the semiconductor switch T using a clamp diode or the like. FIG 5 (b) when the element ignition on command, as shown in a short-circuit semiconductor switch, for example the other arm when being output is generated, V _ce is passing always higher from a low voltage level in the on-state voltage level based on moving to, detecting the short of the other arm of the semiconductor switch. FIG. 6 is a characteristic diagram showing the relationship between the collector-emitter voltage _Vce of the IGBT and the emitter current _Ie .

In the prior art of FIG. 4, first, the first short circuit detection circuit 102 is short-circuited by the AND condition of “element firing on command” and “V _ce is _{equal to} or greater than the first threshold value V _th1 ”. To detect.
Here, as shown in FIG. 5A, in order to detect a short circuit based on _Vce , it is necessary to mask the detection operation for a certain time _Tth or longer, and the filter circuit 103 performs its function. This masking function takes a certain time from the element firing on command to _Vce below a certain voltage level during normal switching due to the element characteristics and circuit impedance of the semiconductor switch. Needed to prevent false detection.

In the prior art of FIG. 4, as shown in FIG. 5B, the output of the first short-circuit detection circuit 102 is input to the filter circuit 103 so as to have a time delay _{equal to} or longer than the mask period _Tth , and the output is 2 is input to the short circuit detection circuit 104. The short-circuit detection state continues even after the lapse of the mask period T _th , and the case where the output voltage of the filter circuit 103 exceeds the second threshold value V _th2 is determined as a true short-circuit fault and the second The short circuit detection circuit 104 outputs a short circuit detection signal. The short detection signal, turns off the semiconductor switch T off circuit 105 outputs the element ignition off command, to protect the semi-conductor switch T.

Now, as one of means for increasing the capacity of the power conversion device, as shown in FIG. 7, there is a method of configuring a single arm by connecting a plurality of semiconductor switches in parallel.
FIG. 7 is an example in which the upper and lower arms for one phase of the power converter (inverter) are configured by semiconductor switches T ₁₁ , T ₁₂ and T ₂₁ , T ₂₂ connected in parallel to each other. A driving circuit 200 indicates a main circuit. In addition, 300 is a DC power supply, P is a positive electrode of the DC power supply 300, N is a negative electrode, and U is an AC output terminal.

In the main circuit 200 shown in FIG. 7, an operation when a short circuit failure occurs in one of two semiconductor switches connected in parallel in one arm will be described with reference to FIG.
In FIG. 8, for example, when the upper arm semiconductor switches T ₁₁ and T ₁₂ are turned on when the lower arm semiconductor switch T ₂₁ is short-circuited, the upper and lower arms are short-circuited, and the semiconductor switches T ₁₁ , T ₁₂ and T ₂₁ are turned on. Short-circuit currents I ₁₁ , I ₁₂ , and I ₂₁ from the DC power supply 300 respectively flow through. Among them, the magnitude relation between the short-circuit current _{I 11, I 12,} the semiconductor switches _{T 11,} the inductance of the main circuit conductors are commonly connected to _{T 12 L 12} (the current flowing to _{I 3), I} 11> _{I 12} That is, of the upper arm semiconductor switches T ₁₁ and T ₁₂ , a large short circuit current flows through a switch (T _{11 in} this example) having a small inductance until reaching the semiconductor switch T ₂₁ in the lower arm that has undergone a short circuit failure. A small short circuit current will flow through the large switch (T _{12 in} this example).

When the difference between the short-circuit currents I ₁₁ and I ₁₂ is large, the current I ₄ flows between the emitters of the semiconductor switches T ₁₁ and T ₁₂ through the wiring from the driving circuit 100, and as a result, the wiring between the driving circuit 100 and the wiring is connected. Since a voltage drop due to the inductances L ₁₁ and I ₄ occurs, the gate voltage of the semiconductor switch T ₁₁ relatively increases.
A semiconductor switch such as an IGBT has a property of causing a large short-circuit current to flow as the gate voltage increases. Therefore, in the semiconductor switch T ₁₁ in which a large short-circuit current flows among the semiconductor switches T ₁₁ and T ₁₂ , the gate voltage increases → the short-circuit current I ₁₁ is increased, the emitter-to-emitter current I ₄ is increased, and the gate voltage is increased. When the short-circuit current exceeding the short-circuit withstand capability of the element flows during the mask period T _th described above, the semiconductor switch T ₁₁ is damaged. .
The above phenomenon, the larger the inductance L ₁₂ of the main circuit conductor, also more likely to occur the more the number of parallel connections of semiconductor switches in the same arm.

On the other hand, Patent Document 2 mentions speeding up of arm protection when a plurality of semiconductor switches are connected in parallel. However, even in this prior art, the phenomenon of element damage during the mask period _Tth is completely eliminated. It cannot be prevented.

JP 2009-153257 A (paragraphs [0022] to [0027], FIG. 1, FIG. 2, etc.) JP 2012-34528 A (paragraphs [0021] to [0024], FIG. 1 and the like)

As described above, in the conventional techniques such as Patent Documents 1 and 2, in a power conversion device in which one arm is configured by connecting a plurality of semiconductor switches in parallel, when a short circuit occurs, a plurality of semiconductor switches connected in parallel are connected. The phenomenon that the short-circuit current increases due to the current flowing between them and is consequently damaged cannot be prevented completely.
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a semiconductor power conversion device that reliably prevents damage caused by a short circuit failure of a semiconductor switch and spread of damage to the entire device.

In order to solve the above-mentioned problem, the invention according to claim 1 is characterized in that the upper and lower arms connected between the positive and negative electrodes of the DC power supply are constituted by a plurality of semiconductor switches connected in parallel to each other, and the plurality of semiconductor switches of each arm are arranged. A semiconductor power conversion device that is simultaneously turned on and off by the same drive circuit, wherein the drive circuit includes means for detecting a short circuit of the semiconductor switch.
An inter-switch current suppression unit is provided on a signal line between the drive circuit and the control signal input terminal and the current output terminal of the plurality of semiconductor switches,
When at least one semiconductor switch of one of the upper and lower arms has a short circuit failure, and a plurality of semiconductor switches of the other arm are simultaneously turned on,
The other arm close to the short-circuited semiconductor switch of the one arm by suppressing the inter-switch current flowing between the current output terminals of the plurality of semiconductor switches of the other arm by the inter-switch current suppressing unit. A semiconductor power conversion device that suppresses an increase in voltage of the control signal input terminal of the semiconductor switch of
The inter-switch current suppression unit is configured by a constant voltage diode, and the constant voltage diode is connected between the control signal input terminal and the current output terminal of the plurality of semiconductor switches, respectively. The switch-to-switch current flowing between the current output terminals of the plurality of semiconductor switches of the other arm is maintained at a constant voltage between the control signal input terminal and the current output terminal of the plurality of semiconductor switches. It is to suppress .

In the invention according to claim 2, the upper and lower arms connected between the positive and negative electrodes of the DC power source are constituted by a plurality of semiconductor switches connected in parallel to each other, and the plurality of semiconductor switches of each arm are simultaneously connected by the same drive circuit. A semiconductor power conversion device to be turned on / off, wherein the drive circuit includes means for detecting a short circuit of the semiconductor switch,
An inter-switch current suppression unit is provided on a signal line between the drive circuit and the control signal input terminal and the current output terminal of the plurality of semiconductor switches,
When at least one semiconductor switch of one of the upper and lower arms has a short circuit failure, and a plurality of semiconductor switches of the other arm are simultaneously turned on,
The other arm close to the short-circuited semiconductor switch of the one arm by suppressing the inter-switch current flowing between the current output terminals of the plurality of semiconductor switches of the other arm by the inter-switch current suppressing unit. A semiconductor power conversion device that suppresses an increase in voltage of the control signal input terminal of the semiconductor switch of
The inter-switch current suppression unit is configured by a resistor,
The resistor is connected between the current output terminals of the plurality of semiconductor switches connected in parallel to each other .

According to the present invention, since the inter-switch current suppression unit made up of a constant voltage diode, a resistor and the like is provided, the semiconductor switch of one arm is short-circuited, and the plurality of semiconductor switches of the other arm are simultaneously turned on, and the upper and lower arms Can be prevented from flowing between the current output terminals of the plurality of semiconductor switches. This prevents the voltage drop due to the current between the switches from acting in the direction of increasing the short-circuit current with respect to the semiconductor switch, and damages to the semiconductor switch due to excessive short-circuit current and damage to the entire power conversion device. Can be prevented.

It is a circuit diagram of the principal part which concerns on the reference form of this invention. It is a circuit diagram of the principal part concerning a 1st embodiment of the present invention. It is a circuit diagram of the principal part concerning 2nd Embodiment of this invention. It is the block diagram which showed notionally the prior art described in patent document 1. FIG. FIG. 5 is an operation waveform diagram of FIG. 4. It is a characteristic view which shows the relationship between the collector-emitter voltage of IGBT, and emitter current. It is the circuit diagram which showed the main circuit for one phase of a power converter, a drive circuit, etc. It is the circuit diagram which showed the main circuit for one phase of a power converter, a drive circuit, etc.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a circuit diagram of a main part showing a reference form of the present invention, in which a main part of a main circuit 200A for one phase of a power converter is shown together with a drive circuit 100. The following embodiments will also be described in the case where an IGBT is used as a semiconductor switch.
In FIG. 1A, semiconductor switches T ₁₁ and T ₁₂ constituting the upper arm of the main circuit 200A are connected in parallel with each other between a positive electrode P of a DC power source (not shown) and an AC output terminal U. Yes. Although not shown, the semiconductor switches (T ₂₁ and T ₂₂ in FIGS. 7 and 8) constituting the lower arm are connected in parallel with each other between the negative electrode N of the DC power source and the AC output terminal U. 202 in the figure is a common connection point between the semiconductor switches T ₁₁ and T ₁₂ connected to the AC output terminal U, and 203 is a main circuit conductor.

A drive circuit 100 for simultaneously turning on and off the semiconductor switches _{T 11, T 12,} the gate of the semiconductor switch _{T 11, T 12} (control signal input terminal) and the signal line 210g between the emitter (current output terminal), 210e is provided with a common mode suppression element 201A such as a common mode core as an inter-switch current suppression unit. As shown in FIG. 1B, the common mode suppression element 201A has an inductance component connected in series to the signal lines 210g and 210e.
Here, a common mode choke coil may be used as the common mode suppression element 201A.

Although not shown, the drive circuit 100 monitors the collector-emitter voltage V _ce of the semiconductor switch and detects a short circuit when the voltage V _ce exceeds a predetermined threshold, as in FIG. . Also, the semiconductor switch constituting the lower arm is given an element on command and an element off command from this drive circuit.

In this reference state, when the semiconductor switches T ₁₁ and T ₁₂ of the upper arm are simultaneously turned on in a state where one of the semiconductor switches of the lower arm is short-circuited, the upper and lower arms are short-circuited. In this case, as described with reference to FIG. 8, the short circuit currents I ₁₁ and I ₁₂ flowing through the semiconductor switches T ₁₁ and T ₁₂ are biased due to the inductance of the main circuit conductor 203, so that the semiconductor switches T ₁₁ and T ₁₂ Current between the emitters (inter-switch current) I ₄ tends to flow, but the flow of the inter-emitter current I ₄ is suppressed by the action of the common mode suppression element 201A.
Therefore, semiconductor switches of the direction which is short-circuit current flows much, for example because the rise of the gate voltage of the switch T ₁₁ is also suppressed, it is possible to prevent the short-circuit current continues to increase.

Here, since ordinary power converters are often equipped with a common mode core or the like for EMC countermeasures and prevention of element misfiring, there is a short circuit between the emitters during a short circuit depending on the inductance of the main circuit conductor and wiring. By selecting a common mode suppression element having characteristics effective for suppressing the current I ₄ , it is possible to protect the semiconductor switch and thus the power conversion device while minimizing the increase in the number of components.

Next, FIG. 2 is a circuit diagram of the main part showing the first embodiment of the present invention. The same circuit components as those in FIG. 1 are denoted by the same reference numerals.
In the first embodiment, as shown in FIG. 2A, the inter-switch current is applied to the signal lines 210g and 210e between the drive circuit 100 and the gates and emitters of the semiconductor switches T ₁₁ and T ₁₂ of the main circuit 200B. A constant voltage diode 201B is provided as a suppression unit. The constant voltage diode 201B is configured by connecting two constant voltage diode elements in reverse series as shown in FIG. 2B, and determines the gate-emitter voltage of the semiconductor switches T ₁₁ and T _12. It is necessary to connect to keep the voltage.

In the first embodiment, also as a voltage drop in the wiring between the emitter of the emitter current I ₄ is flowing driving circuit 100 and the semiconductor switch T ₁₁ or T ₁₂ occurs during a short circuit of the semiconductor switch, a constant voltage The diode 201B can keep the gate-emitter voltage of each switch constant. Therefore, it is possible to prevent the semiconductor switch towards the short-circuit current flows often, for example short-circuit current of the switch T ₁₁ that continues to increase, by the same principle as reference embodiment of Figure 1, the upper and lower arms of the semiconductor switch Breakage can be prevented.

FIG. 3 is a circuit diagram of a main part showing a second embodiment of the present invention. The same circuit components as those in FIGS. 1 and 2 are denoted by the same reference numerals.
In the second embodiment, as shown in FIGS. 3A and 3B, an inter-switch current is applied to the signal line 210e between the drive circuit 100 and the emitters of the semiconductor switches T ₁₁ and T ₁₂ of the main circuit 200C. An emitter resistor 201C as a suppression unit is connected in series.

In the second embodiment, when the lower arm semiconductor switch is short-circuited, the emitter resistor 201C limits the inter-emitter current I ₄ flowing between the upper arm semiconductor switches T ₁₁ and T ₁₂ , so that, for example, the semiconductor switch T ₁₁ The rise of the gate voltage can be prevented.
Therefore, it is possible to prevent the short-circuit current from continuing to increase and to prevent the semiconductor switches of the upper and lower arms from being damaged by the same principle as that of the above-described embodiments.
In this embodiment, since the drive signal is delayed by the emitter resistor 201C even during the normal switching operation of the semiconductor switches T ₁₁ and T ₁₂ , it is necessary to pay attention to changes in switching characteristics.

In each of the above-described embodiments, the case where the inter-switch current suppression unit (common mode suppression element 201A, constant voltage diode 201B, or emitter resistor 201C) is provided in the signal lines 210g and 210e of the upper arm semiconductor switches T ₁₁ and T ₁₂ will be described. However, the inter-switch current suppression unit can be similarly provided on the signal line between the two semiconductor switches of the lower arm and the drive circuit 100. As a result, even when the semiconductor switch of the upper arm is short-circuited first, it is possible to prevent an increase in the short-circuit current of the semiconductor switch of the lower arm.
Needless to say, the number of semiconductor switches connected in parallel in each arm is not limited to two, and an inter-switch current suppression unit may be provided for each semiconductor switch connected in parallel.

  The present invention can be used not only for an IGBT but also for a power conversion device in which each arm is configured by connecting a plurality of semiconductor switches such as power bipolar transistors and MOSFETs in parallel.

100: Drive circuits 200A, 200B, 200C: Main circuit 201A: Common mode suppression element (inter-switch current suppression unit)
201B: Constant voltage diode (inter-switch current suppression unit)
201C: Emitter resistance (inter-switch current suppression unit)
202: common connection terminal 203: main circuit conductor 210g, 210e: signal line 300: DC power supply _{T 11, T 12, T 21} , T 22: semiconductor switch P: positive N: negative U: AC output terminal

Claims (2)

A semiconductor power conversion device in which upper and lower arms connected between the positive and negative electrodes of a DC power source are configured by a plurality of semiconductor switches connected in parallel to each other, and the plurality of semiconductor switches of each arm are simultaneously turned on / off by the same drive circuit. In the semiconductor power conversion device, the drive circuit includes means for detecting a short circuit of the semiconductor switch.
An inter-switch current suppression unit is provided on a signal line between the drive circuit and the control signal input terminal and the current output terminal of the plurality of semiconductor switches,
When at least one semiconductor switch of one of the upper and lower arms has a short circuit failure, and a plurality of semiconductor switches of the other arm are simultaneously turned on,
The other arm close to the short-circuited semiconductor switch of the one arm by suppressing the inter-switch current flowing between the current output terminals of the plurality of semiconductor switches of the other arm by the inter-switch current suppressing unit. a voltage of the control signal input terminals of the semiconductor switch semiconductors power converter that to suppress the rise of,
The inter-switch current suppression unit is configured by a constant voltage diode, and the constant voltage diode is connected between the control signal input terminal and the current output terminal of the plurality of semiconductor switches, respectively. The switch-to-switch current flowing between the current output terminals of the plurality of semiconductor switches of the other arm is maintained at a constant voltage between the control signal input terminal and the current output terminal of the plurality of semiconductor switches. The semiconductor power converter characterized by suppressing. A semiconductor power conversion device in which upper and lower arms connected between the positive and negative electrodes of a DC power source are configured by a plurality of semiconductor switches connected in parallel to each other, and the plurality of semiconductor switches of each arm are simultaneously turned on / off by the same drive circuit. In the semiconductor power conversion device, the drive circuit includes means for detecting a short circuit of the semiconductor switch .
An inter-switch current suppression unit is provided on a signal line between the drive circuit and the control signal input terminal and the current output terminal of the plurality of semiconductor switches,
When at least one semiconductor switch of one of the upper and lower arms has a short circuit failure, and a plurality of semiconductor switches of the other arm are simultaneously turned on,
The other arm close to the short-circuited semiconductor switch of the one arm by suppressing the inter-switch current flowing between the current output terminals of the plurality of semiconductor switches of the other arm by the inter-switch current suppressing unit. A semiconductor power conversion device that suppresses an increase in voltage of the control signal input terminal of the semiconductor switch of
The inter-switch current suppression unit is configured by a resistor ,
A semiconductor power conversion device , wherein the resistor is connected between the current output terminals of the plurality of semiconductor switches connected in parallel to each other .

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