JP2006042563A - Power switching circuit, power converter, open circuit failure detecting method, and driving method of semiconductor switching device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect open circuit failure in a modular semiconductor switching device more quickly and surely. <P>SOLUTION: The power switching circuit comprises a voltage detector 6 for detecting the voltage between the main terminals of a modular semiconductor switching device A, a current detector 7 for detecting a main terminal current flowing through the main terminal of the modular semiconductor switching device A, and a control means for determining the internal resistance between the main terminals of the modular semiconductor switching device A based on the voltage between the main terminals received from the voltage detector 6 and the main terminal current received from the current detector 7 and short-circuiting the main terminals by operating a short circuit means when the occurrence of open circuit failure is detected based on the internal resistance between the main terminals. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a power switching circuit, a power converter, an open fault detection method, and a module type semiconductor switching element driving method.

  For example, Japanese Patent Laid-Open No. 2000-175435 discloses a power conversion device that prevents secondary breakdown due to an open failure with respect to an open failure in a power conversion device using a general-purpose modular semiconductor switching element. ing. That is, when a semiconductor power switching element specially developed for a power conversion device is used, the failure mode of the power conversion device is only a short-circuit failure, but when a module type semiconductor switching device is used, for example, the module An open failure may occur due to, for example, a disconnection of a bonding wire in the type semiconductor switching element.

In the module type semiconductor switching element using, for example, an IGBT (Insulated Gate Bipolar Transistor) as a semiconductor power switching element, the power conversion device detects an IGBT open-circuit failure based on a change in the collector-emitter voltage of the IGBT. -Short-circuit switches that permanently short-circuit emitters are connected in parallel. The power converter having such a configuration prevents an overvoltage from being applied to the IGBT due to a short circuit of the short-circuit switch, thereby preventing secondary breakdown of the IGBT.
JP 2000-175435 A

  By the way, in the power converter of the above-mentioned patent document 1, the short circuit switch detects an open circuit failure of the IGBT based on a change in the collector-emitter voltage of the IGBT. However, the change in the collector-emitter voltage due to the open circuit failure of the IGBT is relatively slow, and the open circuit failure of the IGBT cannot be detected at high speed. In order to prevent secondary breakdown of the IGBT more reliably, it is necessary to detect the open failure at a higher speed.

  On the other hand, some of the module type semiconductor switching elements have a configuration in which a plurality of semiconductor power switching elements such as IGBTs are connected in parallel to increase the current rating. In the case where the switch arm of the power conversion device is configured by using the module type semiconductor switching elements in which a plurality of IGBTs are connected in parallel as described above, the open fault detection method in the power conversion device disclosed in Patent Document 1 is a module type. An initial open fault in the semiconductor switching element cannot be detected. That is, for example, in the case where one IGBT in the module type semiconductor switching element initially has an open failure, the other IGBTs that are operating normally are connected in parallel to the IGBT, so that the collector-emitter voltage hardly changes. Therefore, it is difficult to detect the occurrence of an initial open fault.

  Further, in the case of a power conversion device in which a plurality of module-type semiconductor switching elements are connected in series to form a switch arm, the input voltage is divided by a plurality of module-type semiconductor switching elements (that is, IGBTs). The change in the collector-emitter voltage when an open circuit failure occurs is smaller than that in the case where the switch arm is constituted by the one module type semiconductor switching element described above. Therefore, in such a power conversion device, it becomes more difficult to detect the occurrence of an initial open failure.

  The present invention has been made in view of the above-described circumstances, and detects an open failure in a module type semiconductor switching element in which an open failure may occur more quickly and reliably. The purpose of this is to surely prevent proper dielectric breakdown.

  In order to achieve the above object, the present invention comprises a module type semiconductor switching element that is composed of one semiconductor switching element or a plurality of semiconductor switching elements connected in parallel, and that can cause an open failure in the semiconductor switching element. In a power switching circuit for operating a predetermined short-circuit means to short-circuit between main terminals of the module type semiconductor switching element when an open circuit failure occurs in the switching element, a voltage between main terminals of the module type semiconductor switching element is detected. A voltage detector, a current detector for detecting a main terminal current flowing in the main terminal of the module type semiconductor switching element, a voltage between main terminals input from the voltage detector and a main terminal current input from the current detector; Internal resistance between main terminals of module type semiconductor switching element It determined, and control means for short-circuiting between the main terminals by operating the short-circuit means and for detecting the occurrence of open failure on the basis of the internal resistance between the main terminals, employing the solutions of.

  According to the present invention, an open circuit failure is detected based on an internal resistance between main terminals calculated from a main terminal current and a main terminal current having good response to an open circuit voltage and an open circuit failure. Can be detected at higher speed and more reliably than the conventional detection method using the voltage between the main terminals.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a circuit diagram of a power switching circuit according to the first embodiment of the present invention.
In this circuit diagram, symbol A is a module type semiconductor switching element, 1 is a gate signal generating circuit, 2 is an E / O converter, 3 is an O / E converter, 4 is a gate voltage control circuit, 5 is an amplifier, A resistor voltage divider 7 is a current detector. Of these components, the gate voltage control circuit 4 is a control circuit in the present embodiment, and the resistance voltage divider 6 is a voltage detector in the present embodiment.

  As shown in the figure, the module type semiconductor switching element A has three IGBTs Tr1 to Tr3 (semiconductor switching elements) connected in parallel, that is, the collector terminals of the IGBTs Tr1 to Tr3 are connected in common, and the emitter terminals are also connected in common. The gate terminals are also connected in common. Each collector terminal is connected to one main terminal T1 to which power is applied from the outside, each emitter terminal is connected to the other main terminal T2 to which power is applied from the outside, and each gate terminal receives a gate signal from the outside. It is connected to the applied control terminal Tc. Further, in each of the IGBTs Tr1 to Tr3, freewheeling diodes D1 to D3 are interposed between the collector and the emitter, respectively.

  Such a module type semiconductor switching element A functions also as a short circuit means. That is, in the module type semiconductor switching element A, the IGBTs Tr1 to Tr3 (semiconductor switching elements) can cause an open failure, and when any of the IGBTs Tr1 to Tr3 causes an open failure as described later, an open failure occurs. A forced short-circuit voltage is input from the amplifier 5 to the non-existing IGBT, and the internal junction is short-circuited.

  The module type semiconductor switching element A in the present embodiment is such that three IGBTs Tr1 to Tr3, that is, semiconductor switching elements are connected in parallel, but the number of semiconductor switching elements in the present invention is limited to this. It is not a thing. That is, the number of semiconductor switching elements may be any number as long as it is one or more. The semiconductor switching element is not limited to the IGBT, and may be another semiconductor switching element such as a MOS transistor or an IEGT (Injection Enhanced Gate Transistor) developed for power switching.

  The gate signal generation circuit 1 generates a pulse-like gate signal for switching and driving the module type semiconductor switching element A, and supplies it to the E / O converter 2. The E / O converter 2 is, for example, a phototransistor. The gate signal is photoelectrically converted into an optical gate signal and output to the O / E converter 3. The O / E converter 3 is, for example, a photodiode, and reproduces the gate signal by photoelectrically converting the optical gate signal and outputs it to the gate voltage control circuit 4. Here, the E / O converter 2 and the O / E converter 3 electrically connect a circuit system including the gate signal generation circuit 1 and a circuit system including the gate voltage control circuit 4 and the module type semiconductor switching element A. It is an insulating means for insulating.

  The gate voltage control circuit 4 outputs the gate signal input from the O / E converter 3 to the amplifier 5. The gate voltage control circuit 4 is connected between the main terminals T1 and T2 of the module type semiconductor switching element A based on the voltage between the main terminals input from the resistance voltage divider 6 and the main terminal current input from the current detector 7. The internal resistance r between the main terminals is calculated, and the internal resistance r between the main terminals is compared with a predetermined determination threshold value Rf, whereby any one of the IGBTs Tr1 to Tr3 in the module type semiconductor switching element A is calculated. If it is determined that an open circuit failure has occurred, an excessive voltage (forced short circuit voltage) that can cause a short circuit breakdown of the internal junctions of the IGBTs Tr1 to Tr3 is generated and output to the amplifier 5. The gate voltage control circuit 4 includes an analog arithmetic circuit, for example, for calculating the internal resistance r between the main terminals.

  The amplifier 5 has an output terminal connected to the control terminal Tc, amplifies the gate signal or forced short-circuit voltage input from the gate voltage control circuit 4 with a predetermined amplification degree, and outputs the amplified signal to the control terminal Tc. The resistor voltage divider 6 divides the voltage between the two main terminals T1 and T2, that is, the collector-emitter voltage of the IGBTs Tr1 to Tr3, by the two resistors R1 and R2 connected in series, and the gate voltage control circuit 4 as a detection voltage. Output to. This detection voltage is a voltage that changes depending on the change in the collector-emitter voltage. The current detector 7 detects a current (main terminal current) flowing through the main terminal T2 and outputs it to the gate voltage control circuit 4 as shown in the figure.

Next, the operation of the power switching circuit configured as described above will be described in detail.
First, a normal switching operation will be described. The module type semiconductor switching element A performs a switching operation by a pulsed gate signal input from the gate voltage control circuit 4 via the amplifier 5.

  That is, the gate voltage control circuit 4 outputs the gate signal input from the O / E converter 3 to the amplifier 5, and as a result, each IGBT TTr1 to Tr3 in the module type semiconductor switching element A is connected to the amplifier 5 and the control terminal. The ON / OFF operation is repeated by the gate signal input to the gate terminal via Tc, and the power applied from the outside between the main terminals T1 and T2 is switched in synchronization with the repetition period of the gate signal.

  The gate voltage control circuit 4 outputs the gate signal to the amplifier 5, while the main terminal voltage continuously input from the resistor voltage divider 6, the main terminal current and gate signal continuously input from the current detector 7. The main terminal internal resistance r in a state where the IGBTs Tr1 to Tr3 are turned on is calculated based on the above. That is, the gate voltage control circuit 4 determines a period in which the IGBTs Tr1 to Tr3 are in the ON state based on the gate signal, and the IGBTs Tr1 to Tr3 are turned on based on the main terminal voltage and the main terminal current in the period. The internal resistance r between the main terminals in the state is calculated. Then, the gate voltage control circuit 4 monitors whether or not an open failure has occurred in any of the three IGBTs Tr1 to Tr3 by comparing the internal resistance r between the main terminals with the determination threshold value Rf.

FIG. 2 is an explanatory diagram showing a change in the internal resistance r between the main terminals due to the occurrence of the open failure.
Of the three IGBTs Tr1 to Tr3 connected in parallel to each other, for example, when one IGBT Tr1 fails to open, the main terminal current decreases, while the current sharing of IGBTs Tr2 and Tr3 that do not open fail increases and the operating point changes. Therefore, the voltage between the main terminals increases. Therefore, as shown in FIG. 2, the internal resistance between main terminals r calculated by the gate voltage control circuit 4 is increased to r1 by the normal internal resistance (normal internal terminal resistance r0). This internal resistance r1 between the main terminals can be assumed from the type of the semiconductor switching element, the configuration of the power converter constituted by the power switching circuit, the usage status of the power converter, and the like.

  That is, as shown in the figure, the determination threshold value Rf is larger than, for example, the normal main terminal internal resistance r0, and a large value that is slightly smaller than the main terminal internal resistance r1 that is assumed when one IGBT Tr1 has an open failure. By setting to, the magnitude relationship between the internal resistance r between the main terminals and the determination threshold value Rf changes before and after one IGBTTTr1 fails to open.

  The gate voltage control circuit 4 determines the occurrence of an open fault based on the change in the magnitude relationship between the internal resistance r between the main terminals and the determination threshold value Rf. When the gate voltage control circuit 4 determines that an open failure has occurred, it outputs a forced short-circuit voltage to the amplifier 5 in place of the gate signal to short-circuit the internal junction of the IGBTs Tr1 to Tr3 that are not open failure. Destroy.

  Here, in the power switching circuit, as described above, the occurrence of an open circuit failure of the IGBTs Tr1 to Tr3 is determined based on the change in the internal resistance r between the main terminals calculated from the main terminal voltage and the main terminal current. Such an open fault detection method is a faster and more reliable detection method than the conventional method based on changes in the voltage between the main terminals.

  In other words, the change in the voltage between the main terminals when an open circuit failure occurs is poor in response due to the influence of the external circuit capacitance and the parasitic capacitance of the power switching circuit itself, but the change in the main terminal current varies between the main terminals. Responsiveness is better than a change in voltage. Therefore, a change in internal resistance r between main terminals calculated from a voltage between main terminals and a main terminal current is more responsive than a change in voltage between main terminals. Therefore, the open fault detection method in the power switching circuit is a detection method faster than the conventional method. Although it is conceivable to detect an open circuit failure based on a change in main terminal current with good responsiveness, the main terminal current changes greatly during normal operation, so it is actually very difficult and not practical.

  Further, when the module type semiconductor switching element A has a configuration in which a plurality of (three) IGBTs Tr1 to Tr3 (semiconductor switching elements) are connected in parallel as in this power switching circuit, one IGBT Tr1 has an open failure. The change in the voltage between the main terminals is small. In addition, the change in the voltage between the main terminals becomes smaller as the number of semiconductor switching elements connected in parallel increases. Therefore, as a method for detecting an initial open failure of one or several semiconductor switching elements in a module type semiconductor switching element in which a plurality of semiconductor switching elements are connected in parallel, the internal resistance r between main terminals in this embodiment is A detection method based on change is effective.

  Furthermore, as will be described later, some power converters configured by combining power switching circuits include a switch arm by connecting a plurality of power switching circuits in series. In such a power conversion device, the voltage of the input power is divided by a plurality of power switching circuits connected in series. Therefore, when the semiconductor switching element has an open failure, the change in the voltage between the main terminals is a single power switching circuit. Therefore, the open failure cannot be reliably detected. However, in this embodiment, since the change in the internal resistance between the main terminals of the power switching circuit is used, an open failure of the semiconductor switching element can be reliably detected.

  Therefore, according to this power switching circuit, the open failure is detected at high speed and reliably, and the main terminals T1 and T2 of the module type semiconductor switching element A are short-circuited. Therefore, the module type semiconductor switching element A and this are connected in series. In addition, secondary dielectric breakdown of other module type semiconductor switching elements can be prevented more reliably, and a current path can be secured and the operation of the power converter can be continued.

  On the other hand, in this power switching circuit, the module type semiconductor switching element A has the function of the short-circuit means, but this eliminates the need for a separate dedicated component having the function of the short-circuit means, so the number of parts can be reduced. Therefore, cost reduction can be realized.

Next, a power switching circuit according to a second embodiment of the present invention will be described with reference to FIG.
The power switching circuit according to the first embodiment has a function as a short-circuit means by the module type semiconductor switching element A itself. The power switching circuit according to the second embodiment is shown in FIG. Thus, a thyristor 8 (non-self-extinguishing semiconductor switching element) functioning as a short-circuit means is inserted between the main terminals of the module type semiconductor switching element A.

  That is, when the gate voltage control circuit 4 ′ in this power switching circuit determines the occurrence of an open failure based on the change in the internal resistance r between the main terminals, it outputs a control signal for turning on the thyristor 8 to the thyristor 8. As a result, the thyristor 8, which is a non-self-extinguishing semiconductor switching element, changes its state from the OFF state to the ON state, the main terminals T1, T2 of the module type semiconductor switching element A are short-circuited and the short-circuit state is maintained. .

  Since this power switching circuit can also detect an open-circuit failure at high speed and with certainty in the same manner as the power switching circuit according to the first embodiment, secondary insulation of other module type semiconductor switching elements is possible. Breakage can be prevented more reliably, and a current path can be secured and the operation of the power converter can be continued.

  On the other hand, in this power switching circuit, the module type semiconductor switching element A is not provided with the function of the short-circuit means as in the first embodiment described above, but the thyristor 8 which is a separate component from the module type semiconductor switching element A. Is used as a short-circuit means. In the power switching circuit of the first embodiment, for example, when a bonding wire exists in the path from the control terminal Tc to the gate terminals of the IGBTs Tr1 to Tr3, and the IGBTs Tr1 to Tr3 cause an open failure due to the disconnection of the bonding wire. A forced short-circuit voltage cannot be applied to the gate terminal, and therefore, there may occur a situation where it is impossible to short-circuit and destroy an IGBT that is not open-circuited among the IGBTs Tr1 to Tr3. Since the thyristor 8 which is a separate component from the element A is used as a short-circuit means, it is possible to avoid such a situation and reliably short-circuit the main terminals T1 and T2. It goes without saying that a triac may be used instead of the thyristor 8.

  Finally, as an example, a power conversion device using the power switching circuit according to the first embodiment will be described with reference to FIG.

  This power conversion apparatus converts, for example, 60 Hz three-phase AC power (that is, AC power of AC system A) into 50 Hz three-phase AC power (that is, AC power of AC system B), and 60 Hz three-phase AC power. A total of ten converter circuits K1 to K10 that convert electric power into DC power and a total of ten inverter circuits M1 to M10 that convert this DC power into three-phase AC power of 50 Hz. That is, in this power converter, a total of ten converter circuits K1 to K10 having the same performance are connected in parallel, and a total of ten inverter circuits M1 to M10 having the same performance are connected in parallel to thereby convert the power conversion capacity. Is improved to, for example, about 300 MW.

  Focusing on one converter circuit K1 or inverter circuit M1, the converter circuit K1 and the inverter circuit M1 have switch arms corresponding to each phase of the three-phase alternating current, that is, a total of six switch arms as shown in the figure. Each switch arm is configured by connecting a total of 100 module type semiconductor switching elements having the same function as the power switching circuit in each of the embodiments described above with respect to an open circuit failure while using IGBTs as semiconductor switching elements. ing. Each module type semiconductor switching element includes one IGBT, but a plurality of IGBTs may be connected in parallel like the module type semiconductor switching element A described above.

  According to the power conversion device configured as described above, any IGBT is used because the power switching circuit having the same function as the power switching circuit of the first and second embodiments described above with respect to an open failure is used. In other words, open failure of a module type semiconductor switching element is detected at high speed and reliably, so that secondary insulation breakdown of other module type semiconductor switching elements can be prevented more reliably, and a current path is secured and power is reduced. The operation of the converter can be continued.

In addition, this invention is not limited to the said embodiment, For example, the following modifications can be considered.
(1) In the above description, the case where the IGBT is used as the semiconductor switching element has been described. However, the present invention is not limited to the IGBT as long as the semiconductor switching element can cause an open failure. Is possible.

(2) The power switching circuit described above includes the power converter that converts the AC power described above into other AC power, the converter circuit that converts AC power into DC power, and the inverter circuit that converts DC power into AC power. The present invention can also be applied to a chopper circuit that converts DC power to other DC power.

(3) The above-described power switching circuit uses the module type semiconductor switching element itself or a thyristor as a short-circuit means, but short-circuits a constant voltage diode connected in parallel between the main terminals of the semiconductor switching element instead of the free-wheeling diode. It may be used as a means. In this case, the constant voltage diode short-circuits between the main terminals of the semiconductor switching element by itself short-circuiting when the module type semiconductor switching element fails to open and the voltage between the main terminals of the semiconductor switching element exceeds a predetermined value. By using the constant voltage diode as a short-circuit means in this way, secondary insulation breakdown of other module type semiconductor switching elements can be more reliably performed without providing a separate means for detecting the voltage between the main terminals and the main terminal current. In addition to being able to prevent, a current path is secured and the operation of the power converter can be continued.

1 is a circuit diagram showing a configuration of a power switching circuit according to a first embodiment of the present invention. It is explanatory drawing which shows the change of internal resistance Rs between main terminals by generation | occurrence | production of an open fault in 1st Embodiment of this invention. It is a circuit diagram which shows the structure of the power switching circuit concerning 2nd Embodiment of this invention. It is a circuit diagram which shows the structure of the power converter device concerning one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS A ... Module type semiconductor switching element, 1 ... Gate signal generation circuit, 2 ... E / O converter, 3 ... 3 is O / E converter, 4 ... Gate voltage control circuit, 5 ... Resistance voltage divider, 6 ... Current detection vessel

Claims (15)

In the case where a semiconductor switching element, which includes one semiconductor switching element or a plurality of semiconductor switching elements connected in parallel, is capable of causing an open fault in the semiconductor switching element, A power switching circuit for operating a predetermined short-circuit means to short-circuit between main terminals of the module type semiconductor switching element,
A voltage detector for detecting a voltage between main terminals of the module type semiconductor switching element;
A current detector for detecting a main terminal current flowing in the main terminal of the module type semiconductor switching element;
The internal resistance between the main terminals of the module type semiconductor switching element is obtained from the voltage between the main terminals input from the voltage detector and the main terminal current input from the current detector, and based on the internal resistance between the main terminals And a control means for operating the short-circuit means to short-circuit between the main terminals when the occurrence of an open failure is detected.   2. The power switching circuit according to claim 1, wherein the short-circuit means is a semiconductor switching element, and the control means causes an internal short-circuit breakdown of the semiconductor switching element by applying an excessive drive signal to the semiconductor switching element. .   2. The power switching circuit according to claim 1, wherein the short-circuit means is a non-self-extinguishing semiconductor switching element interposed between main terminals of the module type semiconductor switching element. In the case where a semiconductor switching element, which includes one semiconductor switching element or a plurality of semiconductor switching elements connected in parallel, is capable of causing an open fault in the semiconductor switching element, A power switching circuit for operating a predetermined short-circuit means to short-circuit between main terminals of the module type semiconductor switching element,
The power switching circuit, wherein the short-circuit means is a constant voltage diode that is connected in parallel between the main terminals and short-circuits itself when the voltage between the main terminals exceeds a predetermined value.   The power switching circuit according to claim 1, wherein the semiconductor switching element is an IGBT (Insulated Gate Bipolar Transistor).   6. A power converter comprising: one or a plurality of power switching circuits according to claim 1 connected in series to form one switch arm, and a combination of a plurality of the switch arms.   The power converter according to claim 6, wherein the power converter is an inverter circuit that converts DC power into AC power.   The power converter according to claim 6, wherein the power converter is a converter circuit that converts AC power into DC power.   The power converter according to claim 6, wherein the power converter is a chopper circuit that converts DC power into other DC power.   The power conversion device according to claim 6, wherein the power conversion device is an AC conversion circuit configured by a converter circuit and an inverter circuit and converting AC power into other AC power. A module-type semiconductor switching element that includes one semiconductor switching element or a plurality of semiconductor switching elements connected in parallel, switches power applied between main terminals, and can cause an open circuit failure in the semiconductor switching element. A method for detecting an open failure of an element,
The internal resistance between the main terminals of the module type semiconductor switching element is obtained from the voltage between the main terminals applied between the main terminals and the main terminal current flowing through the main terminals, and the occurrence of the open fault based on the internal resistance between the main terminals. An open fault detection method, characterized by: A driving method of a module type semiconductor switching element, comprising one semiconductor switching element or a plurality of semiconductor switching elements connected in parallel, switching electric power applied between main terminals and causing the semiconductor switching element to cause an open failure. And
Obtain the internal resistance between the main terminals from the voltage between the main terminals applied between the main terminals and the main terminal current flowing through the main terminals,
Determine the occurrence of an open failure between the main terminals based on the internal resistance between the main terminals,
When the occurrence of the open failure is determined, the main terminals are short-circuited. A method for driving a module type semiconductor switching element, comprising:   13. The method of driving a module type semiconductor switching element according to claim 12, wherein the main terminals are short-circuited by passing an excessive driving current through the semiconductor switching element to destroy the inside.   13. The module type semiconductor according to claim 12, wherein a non-self-extinguishing type semiconductor switching element is interposed between main terminals of the module type semiconductor switching element, and the main terminals are short-circuited by the non-self-extinguishing type semiconductor switching element. Switching element driving method. The method of driving a module type semiconductor switching element according to any one of claims 12 to 14, wherein the semiconductor switching element is an IGBT (Insulated Gate Bipolar Transistor).

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