JP2007097261A - Serial semiconductor switch device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress overvoltage and protect all series switch elements when it falls in such a state that overvoltage is generated in a unit switch circuit. <P>SOLUTION: A series semiconductor switch device, where at least two or more unit switch circuits 7<SB>i</SB>which have switching elements 1<SB>i</SB>being connected in series and snubber circuits 5i for suppressing the transient voltage rise accompanying the ON-OFF of the switching switch concerned are connected in series, is provided with overvoltage suppressing means 8<SB>i</SB>which are connected in parallel separately for each unit switch circuit 7<SB>i</SB>and are energized when specified voltage is applied to it thereby suppressing the overvoltage, current detecting means 9<SB>i</SB>which detect the current flowing at energization of the overvoltage suppressing means, an element abnormality detecting means 21 which outputs a stop command when it receives a current detection signal from any one of these current detecting means, and a switching element switching-off means 23 which switches off all switching elements when it receives a stop command. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a series semiconductor switch device for protecting a unit switch circuit from an overvoltage when an overvoltage is applied.

  Conventionally, when monitoring a failure state of a self-extinguishing semiconductor element, a voltage detection signal at both ends of the switching element is compared with a gate signal to the switching element to detect the failure state of the switching element (Patent Document 1). .

  The failure detection of the switching element described in Patent Document 1 will be described with reference to FIGS. 17 and 18. FIG. 17 is a configuration diagram of the switching element failure detection circuit, and FIG. 18 is a diagram illustrating an operation state of the switching element failure detection circuit when the switching element fails.

Switching element fault detection circuit includes a switching element 1 ₁ snubber circuit 5 ₁ are connected in parallel, the snubber circuit 5 ₁ suppresses transient voltage increase generated with the on-off switching element 1 ₁ It has a function and is composed of a snubber capacitor 2 ₁ , a snubber diode 3 _1, and a snubber resistor 4 ₁ . As the snubber circuit 5 _1, although the RCD snubber configuration, may be a snubber circuit having another structure (for example, RC snubber configuration).

Further, voltage detection means 31 ₁ is connected in parallel to both ends of the switching element 1 ₁ . The voltage detecting unit 31 ₁ detects the voltage across the switching element 1 _1, and sends the voltage detection signal to the comparator 32 _1. Comparator 32 ₁ compares the voltage threshold 33 ₁ the predetermined voltage signal detected by the voltage detecting means 31 _1, if the voltage detection signal is more than the threshold value "H" level signal, the threshold value or less If there is, an element state detection signal 34 ₁ called “L” level signal is output.

In the element failure detection circuit, it is normal if the gate signal ON “H” and OFF “L” to the switching element 1 ₁ and the logic of the element state detection signal 34 ₁ are opposite. That is, if the switching element 1 ₁ is normal, the logic of the element state detection signal 34 ₁ becomes “L” when the gate signal to the switching element 1 ₁ is on “H”, and the gate signal to the switching element 1 ₁ Is OFF “L”, the logic of the element state detection signal 34 ₁ is “H”.

Therefore, as shown in FIG. 18, when the gate signal to the switching element 1 ₁ is “L” and the logic of the element state detection signal 34 ₁ is “L”, the element failure detection circuit is switched to the switching element 1. _{When 1} is detected as a short-circuit failure (see FIG. 1A), the gate signal to the switching element 1 ₁ is “H”, and the logic of the element state detection signal 34 ₁ is “H” detects the switching element 1 ₁ is in an open fault (see FIG. (b)).

As another conventional example, a high voltage pulse generator has been proposed. In this high voltage pulse generator, a non-linear resistance and a light emitting element are connected in series between the high voltage side of the switching element and the gate terminal, and two or more switching elements are connected in series to protect the switching element from overvoltage. There exists a thing of the structure to perform (patent document 2).
JP 2003-289755 A JP-A-5-103486

  By the way, in a high-voltage series semiconductor switch device, a plurality of switching elements are connected in series and the switching elements connected in series are turned on at the same time in order to keep the voltage duty per switching element below the rated voltage of the switching element. , Take off configuration.

  FIG. 19 is a configuration diagram in which the switching element failure detection circuit described in Patent Document 1 is applied to a series semiconductor switch device in which two or more switching elements are connected in series. In this figure, the same parts as those in FIG.

In this series semiconductor switch device, in order to equalize the voltage sharing of each switching element 1 _i (i = 1 to N), the voltage dividing resistor 6 _{i is} parallel to each switching element 1 _i (i = 1 to N). (I = 1 to N) and switching element 1 _i (i = 1 to N), snubber circuit 5 _i (i = 1 to N) and voltage dividing resistor 6 _i (i = 1 to N) Each unit switch circuit 7 _i (i = 1 to N) is configured.

Further, a voltage detection means 31 _i (i = 1 to N) and a comparator 32 _i (i = 1 to N) are provided for each switching element 1 _i (i = 1 to N) connected in series. Each comparator 32 _i (i = 1 to N) compares the output of the voltage detection means 31 _i (i = 1 to N) with the voltage threshold value 33 _i (i = 1 to N) to determine the element state. The detection signal 34 _i (i = 1 to N) is output.

Figure 20 is a diagram illustrating each part current, voltage waveforms in the case where only the switching element 1 _1, for example during operation of the series semiconductor switch device is in an open state.

That is, when the switching element 1 ₁ has an open state, since the current flowing in the switching element 1 ₁ is commutated in the snubber capacitor 2 ₁ through snubber diode 3 _1, and the capacitance of the circuit inductance and the snubber capacitor 2 ₁ by the time tau ₁ due to the resonance period determined by the voltage across the unit switch circuits ₇₁ is increased. Generally, tau ₁ is the number μs~ dozen .mu.s, since the time delay tau ₂ to full switching element off from the open state detecting switching element 1 ₁ is several tens .mu.s about the opening of the switching element 1 ₁ even when all the switching elements 1 _i a _(i = 1 to N) is turned off after detecting the condition, the voltage across the unit switch circuits ₇₁ becomes overvoltage can lead to arcing. Normally, the open state of only the switching element 1 ₁ occurs when one switching element 1 ₁ fails to open or when an erroneous off-gate signal is input to the switching element 1 ₁ .

When such a plurality of switching elements 1 _{i (i} = _1~N) are connected in series, the switching element 1 series-connected _{i (i} = _1~N) is not simultaneously turned on, off, one or several When one switching element is in an open state (the remaining series switching elements are in a conductive state), an overvoltage is applied to the switching element in the open state, which may cause an arc.

In the series semiconductor switch device, voltage detection means 31 _i (i = 1 to N) is connected in parallel with the unit switch circuit 7 _i (i = 1 to N), and these voltage detection means 31 _i (i = 1 to 1). Since the element state detection signal obtained from the voltage detection signal detected by N) and the voltage threshold value are compared with the gate signal, the open state of each switching element 1 _i (i = 1 to N) is detected. There are the following problems.

First, since it is necessary to compare all element state detection signals 34 _i (i = 1 to N) output from the comparator 32 _i (i = 1 to N) with the gate command to the switching element, the switching element 1 There is a problem that the circuit for detecting the open state of _i (i = 1 to N) becomes complicated.

Further, since it is necessary to detect the open state of the switching element 1 _i (i = 1 to N) at a high speed (reducing τ ₂ ) as described above, a filter having a time constant sufficient for noise removal in the element failure detection circuit. It becomes difficult to install a circuit, and as a result, noise immunity is reduced. τ ₂ means a time delay from detection of any switching element open state to turning off of all switching elements 1 _i (i = 1 to N).

Therefore, the capacity of the snubber capacitor 2 _i (i = 1 to N) is increased and the degree of increase in voltage applied to both ends of the unit switch circuit when the switching element is open is decreased (τ ₁ is increased), or Method of holding voltage during τ ₂ and suppressing overvoltage by connecting a voltage-dependent resistor (eg, ZNR (registered trademark) element) in parallel with switching element 1 _i (i = 1 to N) And so on. However, when such measures are taken, there is a problem that the snubber capacitor or the voltage-dependent resistor is enlarged. Note that τ ₁ is the time until one of the switching elements is opened and the voltage across the unit switch circuit is fully increased.

  The present invention has been made in view of the above circumstances, and when an overvoltage is applied to a unit switch circuit due to an abnormal opening of a series semiconductor switch element, the overvoltage is suppressed, and the element has a simple configuration. An object of the present invention is to provide a highly reliable series semiconductor switch device that detects an abnormality and reliably protects all series switching elements.

  In order to solve the above-described problems, the present invention includes a switching element and a snubber circuit that is connected in parallel with the switching element and suppresses a transient voltage increase that occurs when the switching element is turned on / off. A series semiconductor switch device in which at least two unit switch circuits are connected in series, each unit switch circuit being connected in parallel, and conducting when a predetermined voltage is applied to suppress overvoltage One of an overvoltage suppression unit, a current detection unit connected in series with each overvoltage suppression unit and detecting a current flowing when the overvoltage suppression unit is conductive, and the current detection unit provided for each unit switch circuit When a current detection signal is received from one current detection means, an element abnormality detection means for outputting a stop command and receiving this stop command The in-line semiconductor switching device having a switching element off means for turning off the series connected the total switching elements of all the unit switching circuits.

  The present invention is configured as described above, so that when a switching element that constitutes a part of each unit switch circuit fails to open due to, for example, peeling of a bonding wire, a predetermined voltage is applied to the overvoltage suppression means to make it conductive. In addition, the function of suppressing the overvoltage is performed, the current flowing by the conduction of the overvoltage suppressing means is detected by the current detecting means, and this detection signal is sent to the element abnormality detecting means. As a result, a stop command is sent from the element abnormality detection means, and all switching elements connected in series via the switching element off means are turned off. For example, an overvoltage applied to the unit switch circuit due to an open failure of the switching element is suppressed. The series semiconductor switch device can be reliably protected by turning off all the switching elements.

  According to the present invention, when an overvoltage is applied to both ends of the unit switch circuit due to an abnormal opening of the series semiconductor switch element, the overvoltage can be reliably suppressed with a simple configuration, and any one of all unit switch circuits can be suppressed. It is possible to provide a highly reliable series semiconductor switch device capable of quickly turning off all switching elements when an abnormality is detected from one.

Embodiments of the present invention will be described below with reference to the drawings.
In the present invention, in a series semiconductor switch device in which a plurality of switching elements 1 _i (i = 1 to N) are connected in series, when an overvoltage is applied to both ends of the unit switch circuit, On the other hand, it is important to detect an abnormal state of the unit switch circuit and immediately turn off all series switching elements.

  FIG. 1 is a block diagram showing a first embodiment of a series semiconductor switch device according to the present invention. In the figure, the same components as those in FIG. 19 are denoted by the same reference numerals, and detailed description thereof is omitted.

In this series semiconductor switch device, overvoltage suppression means 8 _i (i = 1 to N) and current detection means 9 _i (i = 1 to N) are connected to both ends of a unit switch circuit 7 _i (i = 1 to N). Are connected in parallel.

Each overvoltage suppressing means 8 _i (i = 1 to N) is in a conductive state when a predetermined voltage is applied and has a function of suppressing overvoltage. Each current detection means 9 _i (i = 1 to N) has a function of detecting a current flowing through the corresponding overvoltage suppression means 8 _i (i = 1 to N) and outputting a current detection signal.

Stop upon receiving a current detection signal from the current detecting means any one of the respective current detection means 9 _{i (i} = 1~N) at the output of the current detecting means 9 _{i (i} = 1~N) An element abnormality detection unit 21 configured by, for example, an OR circuit that outputs a command, and a switching that turns off all switching elements 1 _i (i = 1 to N) when a stop command is received from the element abnormality detection unit 21 An element off means 23 is provided. The gate signal generation means 22 generates a gate signal based on the switching element gate command, and applies it to the gates of all the switching elements 1 _i (i = 1 to N) through the switching element off means 23.

Next, the operation of the series semiconductor switch device configured as described above will be described.
As shown in FIG. 2, the overvoltage suppressing means 8 _i (i = 1 to N) has the following characteristics with respect to the energizing current 1a, the both-end voltage Va, and a certain voltage threshold value Vthr.
When Va <Vthr, Ia≈0A
When Va> Vthr, Ia >> 0A
However, Ia is the unit switch circuit 7 _i (i = 1 to N), the current flowing from the high voltage side to the low voltage side through the overvoltage suppression means 8 _i (i = 1 to N), and Va is the unit switch circuit 7 _i (i = 1 to N) is a voltage between both ends when the side connected to the high voltage side is viewed from the side connected to the low voltage side (see FIG. 3). Here, the high voltage side of the unit switch circuit 7 _i (i = 1 to N) means that the switching element 1 _i (i = 1 to N) is in an off state and the unit switch circuit 7 _i (i = 1). ~ N) The side that becomes the high voltage side when a voltage is applied to both ends, and the low voltage side of the unit switch circuit 7 _i (i = 1 to N) indicates the side that becomes the opposite low voltage side. .

The series semiconductor switch device, for example, the switching element 1 ₁ is opened, when the other switching elements 1 ₂ to 1 _N has become conductive, the voltage across the unit switch circuits 7 _1, the unit switch circuits 7 ₁ increases as the time by resonance period determined by the inductance and the snubber capacitor 2 _1. Then, the voltage across the unit switch circuits ₇₁ is when it reaches a voltage threshold Vthr, overvoltage suppression means ₈₁ becomes conductive, the increase in the unit switch circuits ₇₁ across voltage is suppressed. At this time and outputs a current detection signal to a current flowing through the current detection unit 9 ₁ simultaneously, and transmits a stop command to the switching element off means 23, all the switching elements 1 _i a _(i = 1 to N) at the same time Can be turned off. When all the switching elements 1 _i (i = 1 to N) are turned off, the voltage across the unit switch circuit 7 _i (i = 1 to N) is equalized by the voltage dividing resistor 6 _i (i = 1 to N). The series semiconductor switch can be safely stopped.

At this time, if the allowable maximum voltage of the unit switch circuit 7 _i (i = 1 to N) is Vrat · sw and the maximum voltage of the unit switch circuit 7 _i (i = 1 to N) during normal operation is Vmax, The overvoltage suppression means 8 _i (i = 1 to N) is selected so that the voltage threshold Vthr satisfies the following expression (1).
Vmax <Vthr <Vrat · sw (1)
In this way, by selecting a certain voltage threshold value Vthr based on the equation (1), overvoltage is detected during normal operation (unit switch circuit 7 _i (i = 1 to N), both-end voltage <Vmax <Vthr). No current is passed through the suppression means 8 _i (i = 1 to N), and the series semiconductor switch circuit is not affected at all. On the other hand, for example, when the switching element 1 ₁ is in an open state (the switching elements 1 ₂ to 1 _N are in a conductive state) and the voltage across the unit switch circuit 7 ₁ rises to the voltage threshold value Vthr, the overvoltage suppressing means 8 _i (i = 1 to N) is in a conducting state. As a result, the voltage across the unit switch circuits 7 _1, certain voltage threshold Vthr is suppressed (<Vrat · sw) extent allowable maximum voltage Vrat · sw unit switch circuit ₇ i (i = _1~N) since become less, it is possible to avoid damage to the unit switch circuit ₇₁ of the configuration goods by overvoltage in advance.

Also, if the voltage across the current detecting means ₉ i (i = _1~N) current flows through the current detecting means ₉ i (i = _1~N) occurs, when the current flowing current detecting means _{9 i} If the maximum voltage at both ends of (i = 1 to N) is Vdet · max, it is necessary to set a voltage threshold Vthr and a maximum voltage Vdet · max that satisfy the following equation (2).

Vthr + Vdet · max <Vrat · sw (2)
Therefore, by setting Vthr and Vdet · max as in the above-described equation (2), when one (or several) switching elements are in an open state, the voltage across the unit switch circuit is set to the unit. It becomes possible to suppress to the allowable maximum voltage Vrat · sw of the switch circuit.

FIG. 4 is a block diagram showing a second embodiment of the series semiconductor switch circuit according to the present invention.
In the present embodiment, an avalanche diode 10 _i (i = 1 to N) having avalanche characteristics is used as the overvoltage suppressing means 8 _i (i = 1 to N) in the first embodiment. That is, the cathode side of the avalanche diode 10 _i (i = 1 to N) is connected to the high voltage side of the unit switch circuit 7 _i (i = 1 to N), and the other configuration is the first embodiment. It is the same. Accordingly, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

The avalanche diode 10 _i (i = 1 to N) has the same characteristics as those in FIG. 2 described above with respect to the energization current Ia, the both-end voltage Va, and a certain voltage threshold value Vthr.
When Va <Vthr, Ia≈0A
When Va> Vthr, Ia >> 0A
In the above equation, Ia is the current flowing from the cathode of the avalanche diode 10 _i (i = 1 to N) to the anode, and Va is the cathode side viewed from the anode side of the avalanche diode 10 _i (i = 1 to N). The voltage at both ends of

In this series semiconductor switch device, for example, the switching element 1 ₁ is in an open state (the switching elements 1 ₂ to 1 _N are in a conducting state), and the voltage across the unit switch circuit 7 ₁ rises, thereby causing a certain voltage threshold value. When reached Vthr, avalanche diode 10 _1, by conduction becomes avalanche state, increase in the unit switch circuits ₇₁ of the voltage across is suppressed.

At this time detects the current flowing through the current detection unit 9 ₁ simultaneously, by outputting a current detection signal, and transmits a stop command from the element error detection unit 21 to the switching element off means 23, all the switching elements 1 _i (I = 1 to N) can be turned off. When all the switching elements 1 _i (i = 1 to N) are turned off, the voltage across the unit switch circuit 7 _i (i = 1 to N) is equalized by the voltage dividing resistor 6 _i (i = 1 to N). Thus, the series semiconductor switch device can be safely stopped.

Usually, the avalanche withstand capability of the avalanche diode 10 _{i (i} = 1~N) is small, if more responsibility avalanche resistance is applied, even when a short circuit state avalanche diode 10 ₁ loses reverse blocking capability, the The technology according to the invention is satisfied and the series semiconductor switch device can be safely stopped.

FIG. 5 is a block diagram showing a third embodiment of the series semiconductor switch device according to the present invention.
In this embodiment, a voltage-dependent resistor 11 _i (i = 1 to N) having voltage non-linear characteristics is provided as the overvoltage suppressing means 8 _i (i = 1 to N) in the first embodiment. It is a configuration.

This voltage-dependent resistor 11 _i (i = 1 to N) has the following characteristics similar to those of FIG. 2 described above with respect to the energization current Ia, the both-end voltage Va, and a certain voltage threshold value Vthr.
When Va <Vthr, Ia≈0A
When Va> Vthr, Ia >> 0A
In the above equation, Ia is a current that flows from the high voltage side of the unit switch circuit 7 _i (i = 1 to N) to the low voltage side through the voltage-dependent resistor 11 _i (i = 1 to N), and Va is This is the voltage across the unit switch circuit 7 _i (i = 1 to N) when the side connected to the high voltage side is viewed from the side connected to the low voltage side.

An example of the voltage-dependent resistor 11 _i (i = 1 to N) is a ZNR (registered trademark) element. The V-I characteristic of this ZNR element is similar to the characteristic shown in FIG. 2, and satisfies the characteristic as an overvoltage suppressing means. In general, for example, a ZNR element has a large energy resistance compared to the avalanche resistance of an avalanche diode, so that the intended function of the present invention can be sufficiently exerted without losing the characteristics as an overvoltage suppressing means in an abnormality detection operation. Can be used repeatedly over a long period of time.

FIG. 6 is a block diagram showing a fourth embodiment of a series semiconductor device according to the present invention.
In this embodiment, voltage-dependent elements 12 _i (i = 1 to N) are provided as the overvoltage suppressing means 8 _i (i = 1 to N) in the first embodiment. Since other configurations are the same as those in FIG. 1, the details will be given in the description of FIG.

The voltage-dependent element 12 _i (i = 1 to N) has a current threshold value Va of the voltage-dependent element 12 _i (i = 1 to N), a voltage Va between both ends, and a certain voltage threshold value Vthr. It has the following characteristics as shown in FIG.
When Va <Vthr, Ia≈0A
When the condition Va> Vthr is satisfied, the conductive state is established, and Ia >> 0A.
Note that Va≈0V after the voltage dependent element 12 _i (i = 1 to N) is turned on.

In this characteristic equation, Ia is a current that flows from the high voltage side of the unit switch circuit 7 _i (i = 1 to N) to the low voltage side through the voltage dependent element 12 _i (i = 1 to N), and Va is This is a voltage across the unit switch circuit 7 _i (i = 1 to N) when the side connected to the high voltage side is viewed from the side connected to the low voltage side (see FIG. 8).

Examples of the voltage-dependent element 12 _i (i = 1 to N) include a Sidac element, but other elements may be used.

In this series semiconductor switch circuit, for example, the switching element 1 ₁ is in an open state (the switching elements 1 ₂ to 1 _N are in a conductive state), and the voltage across the unit switch circuit 7 ₁ rises, thereby causing a certain voltage threshold value. When reached Vthr, since the voltage dependent element 12 ₁ becomes conductive, the voltage across the unit switch circuits ₇₁ becomes substantially 0V. At this time and outputs a current detection signal to a current flowing through the current detection unit 9 ₁ simultaneously transmits a stop command to the switching element off means 23. As a result, the switching element off means 23 can safely stop the series semiconductor switch device by turning off all the switching elements 1 _i (i = 1 to N).

The advantage of this embodiment is that by selecting an appropriate voltage-dependent element 12 _i (i = 1 to N), the voltage-dependent element 12 _i (i = 1 to N) is in an abnormality detection operation. The function intended by the present invention can be sufficiently exhibited without losing the characteristics as overvoltage suppressing means, and the voltage-dependent element can be used repeatedly over a long period of time.

FIG. 9 is a block diagram showing a fifth embodiment of a series semiconductor switch device according to the present invention.
In this embodiment, a gap 13 _i (i = 1 to N) is provided as the overvoltage suppressing means 8 _i (i = 1 to N) in the first embodiment. Since other configurations are the same as those in FIG. 1, detailed description thereof will be given to the description of FIG.

This gap 13 _i (i = 1 to N) has the following characteristics similar to those of FIG. 7 described in the fourth embodiment with respect to the energization current Ia, the both-end voltage Va, and a certain voltage threshold value Vthr. Have
When Va <Vthr, the insulation of the air gap 13 _i (i = 1 to N) is maintained, and Ia≈0A
When the condition of Va> Vthr is satisfied, the insulation of the gap 13 _i (i = 1 to N) is broken and discharged between the gaps 13 _i (i = 1 to N), so that Ia >> 0A. During the discharge of the gap 13 _i (i = 1 to N), Va becomes an arc voltage of several tens of volts.

However, in this characteristic equation, Ia is a current flowing from the high voltage side of the unit switch circuit 7 _i (i = 1 to N) to the low voltage side through the air gap 13 _i (i = 1 to N), and Va is a unit. This is the voltage across the switch circuit 7 _i (i = 1 to N) when the side connected to the high voltage side is viewed from the side connected to the low voltage side.

The V-I characteristics of the gap 13 _i (i = 1 to N) are the same as those shown in FIG. 7 and satisfy the characteristics as overvoltage suppressing means. Moreover, by utilizing the insulating properties of the air gap 13 _{i (i} = 1~N), since to satisfy the function of suppressing the overvoltage has a very high reliability. Moreover, the air gap 13 _i (i = 1 to N) can be used repeatedly without losing the characteristics as the overvoltage suppressing means even for repeated failure detection operations.

FIG. 10 is a block diagram showing a sixth embodiment of a series semiconductor switch device according to the present invention.
In this embodiment, the current detection means 9 _i (i = 1 to N), which is a component of the first to fifth embodiments, is changed to the main circuit potential of the unit switch circuit 7 _i (i = 1 to N). While the potential is fixed, an insulating means 14 _i (i = 1 to N) is interposed between the current detecting means 9 _i (i = 1 to N) and the element abnormality detecting means 21. That is, in the sixth embodiment, the current detection signal detected by the current detection means 9 _i (i = 1 to N) is electrically insulated by the insulation means 14 _i (i = 1 to N), and the detection signal is detected. Only to the element abnormality detecting means 21.

With such a configuration, all the detection signals of the current detection means 9 _i (i = 1 to N) have the same potential in the element abnormality detection means 21, so that the unit switch circuits 7 _i (i with different potentials are used. Although it is necessary to electrically insulate the detection signal output from = 1 to N) by some means, the insulating means 14 _i (i = 1 to N) can play the role.

For example, consider a current transformer that is not electrically connected to the main circuit of the unit switch circuit 7 _i (i = 1 to N) as the current detection means 9 _i (i = 1 to N). Although the potentials of the unit switch circuits 7 _i (i = 1 to N) are different from each other, for example, the potentials of the OR circuits constituting the element abnormality detection means 21 are the same, so the required withstand voltage for the current transformer is the unit switch circuit. 7 _i (i = 1 to N) varies. Further, the required withstand voltage of the current transformer attached to the unit switch circuit having the highest potential is equal to or higher than the maximum potential of the series semiconductor switch device, which is not realistic and lacks reliability.

The advantage of this embodiment is that the current detection signal detected by the current detection means 9 _i (i = 1 to N) is converted into the unit switch circuit 7 _i (i = i = N) using the insulation means 14 _i (i = 1 to N). 1 to N) is electrically insulated from the main circuit, and the current detection means 9 _i (i = 1 to N) is set to the main circuit potential of the unit switch circuit 7 _i (i = 1 to N), and the unit switch circuit 7 _i (i = 1 to N), overvoltage suppressing means 8 _i (i = 1 to N), and current detecting means 9 _i (i = 1 to N) can be configured identically.

FIG. 11 is a block diagram showing a seventh embodiment of the series semiconductor switch device according to the invention.
In this embodiment, a transformer 15 _i (i = 1 to N), for example, is used as the insulating means 14 _i (i = 1 to N) in the sixth embodiment. Accordingly, other configurations are the same as those in FIGS. 1 and 10, and details will be left to the description of those drawings.

In this embodiment, when current detection means 9 _i (i = 1 to N) that generates a voltage at both ends at the time of current detection is used, as described in the first embodiment, equation (2) Therefore, the maximum voltage Vdet · max at both ends of the current detection means 9 _i (i = 1 to N) should be as small as possible.

And since the detection signal from the current detection means 9 _i (i = 1 to N) is transmitted through the transformer 15 _i (i = 1 to N), the voltage level of the detection signal is changed to the transformer 15 _i (i = 1 to N) can be changed by changing the winding ratio, and even if the maximum voltage Vdet · max at both ends of the current detection means 9 _i (i = 1 to N) is set small, element abnormality The detection signal can be reliably detected on the detection means 21 side.

FIG. 12 is a block diagram showing an eighth embodiment of a series semiconductor switch device according to the present invention.
This embodiment is an example in which, for example, an optical fiber 16 _i (i = 1 to N) serving as an optical transmission medium is used as the insulating means 14 _i (i = 1 to N) in the sixth embodiment. Other configurations are the same as those in FIGS. 1 and 10, and details will be left to the description of those drawings.

The advantage of the present embodiment is that the withstand voltage of the optical fiber 16 _i (i = 1 to N) is about 10 kV / mm, so that it can be easily insulated. In addition, it is possible to provide a more reliable series semiconductor switch device without the influence of malfunction due to electrical noise.

FIG. 13 is a block diagram showing a ninth embodiment of a series semiconductor switch device according to the invention.
In this embodiment, the current detection means 9 _i (i = 1 to N) in the eighth embodiment is configured as follows. That is, as the current detecting means 9 _i (i = 1 to N), a shunt resistor 17 _i (i = 1 to N) is connected in series with the overvoltage suppressing means 8 _i (i = 1 to N). A series circuit of a current limiting resistor 19 _i (i = 1 to N) and a light emitting element 18 _i (i = 1 to N) is connected in parallel to both ends of 17 _i (i = 1 to N). 18 _i (i = 1 to N) and optical fiber 16 _i (i = 1 to N) are optically coupled.

Next, the operation of the series semiconductor switch device configured as shown in FIG. 13 will be described with reference to FIGS. 14 shows the case where, for example, the voltage-dependent resistor 11 _i (i = 1 to N) (see FIG. 5) is used as the overvoltage suppressing means, FIG. 15 shows the voltage-dependent element 12 _i (i = 1 to N) (see FIG. 6) and the air gap 13 _i (i = 1 to N) (see FIG. 9), FIG. 16 shows an avalanche diode 10 _i (i = 1 to N) (FIG. It is a figure which shows the operation | movement waveform at the time of using 4 reference).

Now, for example, the switching element 1 ₁ is in an open state as shown in FIG. 1A (the switching elements 1 ₂ to 1 _N are in a conducting state), and the voltage across the unit switch circuit 7 ₁ rises to a certain voltage threshold Vthr. when reached (shown (b)), the over-voltage suppression means ₈₁ be turned, increase in the unit switch circuits ₇₁ of the voltage across is suppressed (shown (c)). At the same time, when the overvoltage suppressing means 8 ₁ becomes conductive, a current determined by the ratio of the shunt resistor 17 ₁ and the current limiting resistor 19 ₁ flows to the light emitting element 18 ₁ (illustration (D)). 18 ₁ emits light. A current detection signal insulated from the main circuit potential of the unit switch circuit 7 ₁ by light is transmitted to the element abnormality detecting means 21 through the optical fiber 16 ₁ . Element error detection unit 21 receives the current detection signal through the optical fiber 16 _1, sends a stop command to the switching element off means 23. When receiving the stop command, the switching element off means 23 turns off all the switching elements 1 _i (i = 1 to N). Therefore, the series semiconductor switch device can be stopped safely.

Since the shunt resistor 17 _i (i = 1 to N) generates a voltage at both ends at the time of current detection, it is necessary to satisfy the relational expression (2) (see the first embodiment). Now, when the maximum value of the current flowing through the shunt resistor 17 _i (i = 1 to N) is Imax and the resistance value of the shunt resistor 17 _i (i = 1 to N) is Rs, Vdet · max = Rs Since Imax, if the shunt resistor 17 _i (i = 1 to N) having a resistance value Rs that satisfies the above equation (2) is selected, the unit switch circuit 7 _i (i = 1 to 1) at the time of abnormality is selected. N) It is possible to suppress the voltage between both ends to be equal to or lower than the allowable maximum voltage Vrat · sw of the unit switch circuit.

According to such a configuration, the light-emitting element 18 _i (i = 1 to N) can be easily obtained from the current flowing through the overvoltage suppressing means 8 _i (i = 1 to N) at the time of abnormality without taking a complicated configuration. The highly reliable detection signal can be transmitted to the element abnormality detecting means 21 while emitting light and utilizing the characteristics of the optical fiber 16 _i (i = 1 to N).

Therefore, according to the first to ninth embodiment described above, the off-gate signal or the like erroneously to the switching element 1 _{i (i} = 1~N) failure or switching elements 1 _{i (i} = 1~N) Therefore, any one or several of the switching elements 1 _i (i = 1 to N) of the unit switch circuit 7 _i (i = 1 to N) are in an open state, and an overvoltage is applied to the switching element in the open state. Even in the applied state, it is possible to suppress an overvoltage from being applied to both ends of the open element, and any one of the switching elements 1 _i (i = 1 to N) is open. Is detected, and a stop command is transmitted to the switching element off means 23 to turn off all the switching elements 1 _i (i = 1 to N). Cancel And a highly reliable series semiconductor switch device can be provided.

  In addition, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS The block diagram which shows 1st Embodiment of the series semiconductor switch apparatus which concerns on this invention. FIG. 5 is a VI characteristic diagram for explaining the overvoltage suppressing means shown in FIG. 1. The figure explaining the relationship between the voltage and electric current in an overvoltage suppression means. The block diagram which shows 2nd Embodiment of the series semiconductor switch apparatus which concerns on this invention. The block diagram which shows 3rd Embodiment of the series semiconductor switch apparatus which concerns on this invention. The block diagram which shows 4th Embodiment of the series semiconductor switch apparatus which concerns on this invention. FIG. 7 is a VI characteristic diagram illustrating the voltage dependent element shown in FIG. 6. The figure explaining the relationship between the voltage and current in a voltage dependence element. The block diagram which shows 5th Embodiment of the series semiconductor switch apparatus which concerns on this invention. The block diagram which shows 6th Embodiment of the series semiconductor switch apparatus which concerns on this invention. The block diagram which shows 7th Embodiment of the series semiconductor switch apparatus which concerns on this invention. The block diagram which shows 8th Embodiment of the series semiconductor switch apparatus which concerns on this invention. The block diagram which shows 9th Embodiment of the series semiconductor switch apparatus which concerns on this invention. FIG. 10 is a diagram illustrating current and voltage waveforms of each part of a series semiconductor switch circuit having a configuration using a voltage-dependent resistor as overvoltage suppressing means and using the ninth embodiment. FIG. 25 is a diagram illustrating current and voltage waveforms of each part of a series semiconductor switch circuit having a configuration using a voltage-dependent element and a gap as overvoltage suppressing means and using the ninth embodiment. FIG. 25 is a diagram showing current and voltage waveforms of each part of a series semiconductor switch circuit having a configuration using an avalanche diode as overvoltage suppressing means and using the ninth embodiment. Configuration diagram of switching element failure detection circuit described in Patent Document 1 Operational schematic diagram of switching element failure detection circuit described in Patent Document 1 The block diagram which applied the switching element failure detection circuit described in patent document 1 to the series semiconductor switch apparatus FIG. 20 is a current waveform and voltage waveform diagram when each switching element shown in FIG. 19 is in an open state.

Explanation of symbols

1 ₁ to 1 _N ... switching element, 2 ₁ to 2 _N ... snubber capacitor, 3 _{1 to} 3 _N ... snubber diode, 4 ₁ to 4 _N ... snubber resistance, 5 _{1 to} 5 _N ... snubber circuit, 6 _{1 to} 6 _N ... Voltage divider resistor, 7 _{1 to} 7 _N ... Unit switch circuit, 8 ₁ to 8 _N ... Overvoltage suppression means, 9 _{1 to} 9N ... Current detection means, 10 ₁ to 10 _N ... Avalanche diode, 11 _{1 to} 11 _N ... Voltage Dependent resistor, 12 _{1 to} 12 _N ... Voltage dependent element, 13 _{1 to} 13 _N ... Air gap, 14 _{1 to} 14 _N ... Insulation means, 15 ₁ to 15 _N ... Transformer, 16 _{1 to} 16 _N ... Optical fiber , 17 _{1 to} 17 _N ... shunt resistance, 18 ₁ to 18 _N ... light emitting element, 19 _{1 to} 19 _N ... current limiting resistance, 21 ... element abnormality detection means (logical sum circuit), 22 ... gate signal generation means, 23 ... Switching element off means.

Claims (9)

At least two or more unit switch circuits composed of a switching element and a snubber circuit that is connected in parallel with the switching element and suppresses a transient voltage increase generated when the switching element is turned on or off are connected in series. In the connected series semiconductor switch device,
Overvoltage suppression means connected in parallel for each of the unit switch circuits, conducting when a predetermined voltage is applied, and suppressing overvoltage,
A current detection means connected in series with each overvoltage suppression means and detecting a current flowing when the overvoltage suppression means is conductive;
An element abnormality detection means for outputting a stop command when receiving a current detection signal from any one of the current detection means provided for each unit switch circuit;
And a switching element off means for turning off all the switching elements connected in series of all the unit switch circuits when receiving the stop command.   2. The series semiconductor switch device according to claim 1, wherein the overvoltage suppressing means is an avalanche diode having an avalanche characteristic, and a cathode side of the diode is connected to a high voltage side of the unit switch circuit.   2. The series semiconductor switch device according to claim 1, wherein the overvoltage suppressing means is a voltage dependent resistor having a voltage non-linear characteristic.   The series semiconductor switch device according to claim 1, wherein the overvoltage suppressing unit is a voltage-dependent element that becomes conductive when a predetermined voltage is applied.   2. The series semiconductor switch device according to claim 1, wherein the overvoltage suppressing means is a gap that breaks down and becomes conductive when a predetermined voltage is applied. In the series semiconductor switch device according to any one of claims 1 to 5,
Insulating means is provided for fixing each of the current detection means to the main circuit potential of the corresponding unit switch circuit, and for electrically isolating the detection signal detected by each current detection means and transmitting it to the element abnormality detection means. A series semiconductor switch device characterized by that.   As the insulating means, a transformer is provided between each of the current detecting means and the element abnormality detecting means, and detection signals detected by the respective current detecting means are transmitted to the primary side and the secondary side of the transformer. The serial semiconductor switch device according to claim 6, wherein the serial semiconductor switch device is insulated and transmitted.   As the insulating means, an optical transmission medium is provided between each of the current detecting means and the element abnormality detecting means, and a detection signal detected by each of the current detecting means is transmitted through the optical transmission medium. The series semiconductor switch device according to claim 6. The current detecting means includes a shunt resistor connected in series with the overvoltage suppressing means, a light emitting element connected in parallel with the shunt resistor, and a current flowing in the light emitting element connected in series with the light emitting element. Consisting of current limiting resistance to flow,
9. The series semiconductor switch device according to claim 8, wherein when the overvoltage suppressing means is in a conductive state, the light emitting element emits light and the light emission signal is incident on the optical transmission medium.

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