CN109950866B - Current breaker - Google Patents

Abstract

The invention provides a current breaker which can cut off current at high speed and reduce current conduction loss. The current breaker (10) is provided with a main conduction part (11) serving as a conduction part of current and an auxiliary conduction part (12) connected in parallel with the main conduction part, wherein the main conduction part (11) comprises a first semiconductor switch element (1) without a self-turn-off function and a conduction part switching element (2) which is connected in series with the first semiconductor switch element and is used for switching the conduction part, and the auxiliary conduction part (12) comprises a second semiconductor switch element (3). The current interrupter (10) is provided with a control circuit for controlling the on/off operations of the first semiconductor switching element (1), the conduction section switching element (2), and the second semiconductor switching element (3), respectively.

Description

Current breaker

Technical Field

The present invention relates to a current interrupter, and more particularly, to a current interrupter of a composite semiconductor switching structure using a semiconductor switching element.

Background

As a current interrupter for protecting a circuit in the event of an abnormality such as a short circuit, a mechanical switch is known in the simplest configuration. However, in the case of a mechanical switch, an arc may be generated at the time of current interruption due to a reaction speed of a mechanism such as a spring, and a short-circuit current may flow through the arc. As a countermeasure method, a current interrupter having a structure in which a semiconductor switch is connected in parallel to a mechanical switch is known (for example, see patent document 1).

In the case of a configuration in which semiconductor switches are connected in parallel, an arc is not generated in the mechanical switch by diverting a current to the semiconductor switches connected in parallel during a current interrupting operation. However, in the case of this configuration, it is necessary to follow the procedure of turning off the mechanical switch and then turning off the semiconductor switch, and therefore, it takes a relatively long time to cut off the current.

Therefore, the following structure is known: a plurality of semiconductor elements are connected in parallel, one element is caused to function as a switch, and the other element is caused to function as a switch for reducing current conduction loss at the time of stabilization. With regard to such a structure, the following technique is also proposed (for example, patent document 2): a semiconductor element capable of high-speed switching although low withstand voltage is arranged, and the conduction path of current is switched to one element or the other element by turning on or off the semiconductor element. In addition, the following techniques have also been proposed (for example, see patent documents 3 to 6): for example, a thyristor or a triac (triac) having a relatively large current capacity and a relatively small current conduction loss is used as an element that plays a role of reducing the current conduction loss at the time of stabilization, or an alternating current is supported by allowing conduction of a bidirectional current.

Patent document 1: japanese patent No. 5628184

Patent document 2: japanese patent laid-open publication No. 2011-

Patent document 3: japanese patent laid-open publication No. 2005-192354

Patent document 4: japanese laid-open patent publication No. 2006-50697

Patent document 5: japanese patent laid-open No. 2008-54468

Patent document 6: japanese laid-open patent publication No. 2009-81969

Disclosure of Invention

Problems to be solved by the invention

Regarding the configuration using a plurality of semiconductor switching elements, for example, in the configuration described in patent document 6, since a current flows through two semiconductor switching elements, i.e., an IGBT and a MOSFET, a current conduction loss is a loss amount of the two semiconductor switching elements, and it is desired to further reduce the current conduction loss. In addition, as a general characteristic of the semiconductor switching element, a switching speed and an on-resistance are in a trade-off relationship. Therefore, for example, when a semiconductor switching element having a high switching speed is used, the current conduction loss becomes large because the on-resistance becomes large although the switching loss can be reduced. That is, in the conventional art, it is difficult to achieve both high-speed current interruption and reduction of current conduction loss.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a current breaker capable of cutting off a current at high speed and reducing a current conduction loss.

Means for solving the problems

In order to achieve the above object, a current interrupter according to an aspect of the present invention includes a main conduction unit serving as a conduction unit for a current, and an auxiliary conduction unit connected in parallel to the main conduction unit, wherein the main conduction unit includes a conduction unit switching element connected in series with the first semiconductor switching element for switching the conduction unit by an on/off operation of the conduction unit switching element, and a first semiconductor switching element having no self-turn-off function, and the auxiliary conduction unit includes a second semiconductor switching element, and the current interrupter includes a control circuit for controlling on/off operations of the first semiconductor switching element, the conduction unit switching element, and the second semiconductor switching element.

In order to achieve the above object, a current interrupter according to another aspect of the present invention includes a main conduction unit serving as a conduction unit for a current and an auxiliary conduction unit connected in parallel to the main conduction unit, wherein the main conduction unit includes a series circuit in which a conduction unit switching element and a first semiconductor switching element having no self-turn-off function are connected in antiparallel with each other, the auxiliary conduction unit includes a parallel circuit in which a second semiconductor switching element is connected in antiparallel with a diode to form a bidirectional conduction path, and the current interrupter includes a control circuit for controlling on and off operations of the first semiconductor switching element, the conduction unit switching element, and the second semiconductor switching element.

In the above-described configuration, for example, the first semiconductor switching element has a larger current capacity and higher conductivity than the second semiconductor switching element, and the second semiconductor switching element can perform a switching operation at a higher speed than the first semiconductor switching element. Since the current mainly flows through the first semiconductor switching element, conduction loss can be reduced. When the current is cut off, the conduction part switching element is first turned off, whereby the first semiconductor switching element is easily turned off and the main conduction part is quickly brought into a non-conduction state. In this case, although the current flows to the auxiliary conducting portion including the second semiconductor switching element, the second semiconductor switching element is also a switching element that can be turned off at a higher speed, and therefore, the current breaker as a whole can cut off the current at a high speed. Further, according to the connection relationship and operation of the semiconductor elements as described above, the switching loss generated by the conducting portion switching element and the second semiconductor switching element, which can perform a switching operation at a high speed, is relatively small, and therefore, the switching loss can be reduced.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, it is possible to provide a current interrupter capable of performing high-speed current interruption and reducing current conduction loss.

Drawings

Fig. 1 is a circuit diagram showing a configuration of a main part of a composite semiconductor switch according to a first embodiment of the present invention.

Fig. 2 is a circuit diagram showing the overall configuration of the composite semiconductor switch according to the first embodiment of the present invention.

Fig. 3 is a waveform diagram for explaining the operation of the composite semiconductor switch according to the first embodiment of the present invention.

Fig. 4 is a schematic diagram for explaining an operation of the composite semiconductor switch according to the first embodiment of the present invention.

Fig. 5 is a circuit diagram showing a configuration of a main part of a composite semiconductor switch according to a second embodiment of the present invention.

Fig. 6 is a waveform diagram for explaining an operation of the composite semiconductor switch according to the second embodiment of the present invention.

Fig. 7 is a schematic diagram for explaining an operation of the composite semiconductor switch according to the second embodiment of the present invention.

Description of the reference numerals

1. 1 a: a thyristor (first semiconductor switching element); 2. 2 a: a MOSFET (conduction part switching element); 3. 3 a: an IGBT (second semiconductor switching element); 4: a control circuit; 5: a control device; 10: compound semiconductor switches (current interrupters); 11. 11 a: a main conducting part; 12. 12 a: an auxiliary conduction part; 41: a protection circuit; 42: a gate pulse distribution circuit; 43: a drive circuit; a: a first terminal; b: a second terminal; IN: an input terminal; OUT: an output terminal; CTL: and a control terminal.

Detailed Description

Hereinafter, a current interrupter according to an embodiment of the present invention will be described in detail with reference to the drawings. One of the features of the present invention is to provide a circuit configuration capable of cutting off a current at a high speed and reducing a current conduction loss.

(first embodiment)

First, a first embodiment of the present invention will be described in detail with reference to fig. 1 to 4. The configuration according to the present embodiment will be described with reference to fig. 1 and 2, and the operation according to the present embodiment will be described with reference to fig. 3 and 4.

(Structure)

As shown in fig. 1 and 2, the current interrupter according to the present embodiment is, for example, a composite semiconductor switch 10 applied to a distribution board in a factory or the like, and includes a first semiconductor switching element 1, a conduction portion switching element 2, a second semiconductor switching element 3, and a control circuit 4.

The first semiconductor switching element 1 is a semiconductor switching element having a relatively low on-resistance and a relatively small current conduction loss, and is configured by a separately-excited thyristor in the present embodiment. Hereinafter, for convenience of explanation, the first semiconductor switching element 1 is referred to as a thyristor 1. The conduction part switching element 2 is appropriately referred to as a MOSFET 2. The thyristor 1 has an anode connected to the input terminal IN of the compound semiconductor switch 10, a cathode connected to the drain of the MOSFET2, and a gate connected to the control circuit 4.

The conduction part switching element 2 is a semiconductor switching element having a switching speed higher than that of the first semiconductor switching element and the second semiconductor switching element. In the present embodiment, the conducting part switching element 2 is, for example, a low-voltage MOSFET having an on-resistance of several milliohms when the withstand voltage is of the order of several 10V, and incorporates a body diode or a diode connected in reverse parallel. The source of the MOSFET2 is connected to the output terminal OUT of the composite semiconductor switch 10, and the gate thereof is connected to the control circuit 4. That is, the MOSFET2 is configured to be connected to the cathode side of the thyristor 1. A series circuit is formed by the thyristor 1 and the MOSFET2, which series circuit forms the main conduction part 11 in the compound semiconductor switch 10. The MOSFET2 is an element for switching a current path in the compound semiconductor switch 10, and details of the operation thereof will be described later.

The second semiconductor switching element 3 is a semiconductor switching element having a switching speed higher than that of the thyristor 1. In order to enable a high-speed switching operation, the second semiconductor switching element 3 may be configured by a semiconductor switching element having a relatively low switching loss, and in the present embodiment, may be configured by an IGBT. Hereinafter, the second semiconductor switching element 3 is referred to as an IGBT3 for convenience of description. The IGBT3 has a collector connected to the input terminal IN of the compound semiconductor switch 10 and an emitter connected to the output terminal OUT of the compound semiconductor switch 10. That is, the IGBT3 and the thyristor 1 are connected in parallel with the series circuit of the MOSFET2, and form the auxiliary conduction portion 12 in the composite semiconductor switch 10. The gate of the IGBT3 is also connected to the control circuit 4. The IGBT3 is an element for finally interrupting a current by a high-speed switching operation, and details of the operation thereof will be described later.

When the relationship between the thyristor 1 and the IGBT3 regarding the switching speed and the on-resistance is summarized, the thyristor 1 having a low on-resistance, a small current conduction loss, and a large current capacity acts during the steady-state conduction, and the IGBT3 having a small switching loss, which can perform the switching operation at high speed, acts during the switching operation. In addition, when switching the current path, that is, switching with shared roles, the MOSFET2 with the highest speed among these elements takes the roles.

Next, the control circuit 4 will be explained. The control circuit 4 is a circuit for controlling the timing of applying a voltage to the gate of each semiconductor element (thyristor 1, MOSFET2, IGBT 3) in the compound semiconductor switch 10, and in the present embodiment, the control circuit 4 includes a protection circuit 41, a gate pulse distribution circuit 42, and a drive circuit 43.

The protection circuit 41 is supplied with a control signal (on/off control signal) from the external control device 5 via the control terminal CTL of the compound semiconductor switch 10. The protection circuit 41 detects a current on the input terminal IN side of the compound semiconductor switch 10, and stops supplying the control signal to the gate pulse distribution circuit 42 of the next stage when the current value is equal to or larger than a predetermined overcurrent setting value lim.

The gate pulse distribution circuit 42 gives a predetermined delay time td to the control signal supplied via the protection circuit 41_on、td_offAnd a time difference Δ T, thereby varying the on/off operation timing of each semiconductor switching element. The delay time td will be described later_on、td_offAnd a time difference Δ T.

The drive circuit 43 is connected to the gate pulse distribution circuit 42 for a delay time td given to the control signal_onVoltages are applied to the gates of the semiconductor elements at appropriate timings.

The configuration of the protection circuit 41, the gate pulse assigning circuit 42, and the drive circuit 43 may be any configuration as long as the operation described with reference to fig. 3 can be achieved, and any circuit configuration may be adopted.

In the present embodiment, the thyristor 1, the MOSFET2, the IGBT3, and the control circuit 4 are packaged as one power module and are disposed on a switchboard or the like, and the operation is performed by supplying the above-described one control signal from the external control device 5 to the control terminal CTL, but the present invention is not limited thereto.

(action)

Next, the current interruption operation of the composite semiconductor switch 10 configured as described above will be described in detail with reference to fig. 3 and 4.

As shown in fig. 3 and fig. 4 (I), initially, a voltage is applied from the control circuit 4 to the gate of the IGBT3, and only the IGBT3 is turned on at a timing t1 while the thyristor 1 and the MOSFET2 are off. Since the IGBT3 is a semiconductor switching element capable of performing a switching operation at a relatively high speed, it can be quickly turned on. By turning on the IGBT3 capable of high-speed switching operation first, the overall starting operation of the compound semiconductor switch 10 is accelerated. In this case, since only the IGBT3 is turned on, only the auxiliary conducting portion 12 is turned on, and thus a current flows through the auxiliary conducting portion 12.

Next, as shown in fig. 3 and (II) of fig. 4, the delay time td after the voltage is applied to the gate of the IGBT3_onThen, a voltage is applied from the control circuit 4 to the gates of the thyristor 1 and the MOSFET2, and the thyristor 1 and the MOSFET2 are turned on at timing t 2. IN this case, since the thyristor 1 has a lower on-resistance and a higher conductivity than the IGBT3, most of the current from the input terminal IN of the compound semiconductor switch 10 flows through the thyristor 1 on the side having a higher conductivity, that is, the main conducting portion 11. Further, with respect to the delay time td_onThe time required for turning on (turn on) the IGBT3, that is, the time until the turn-on operation is completed and the current in the steady state flows, may be secured. Specifically, the delay time td_onAnd about 1 μ sec to 2 μ sec, but is not limited thereto. By turning on the IGBT3 first in this way, the turn-on loss of the thyristor 1 does not occur.

Here, the present inventors simulated the ratio of the currents flowing through the main conduction portion 11 and the auxiliary conduction portion 12. For example, when comparing semiconductor switching elements under the conditions of a rating of 1200V and 50A, the on voltage of the thyristor 1 is 1.4V, and the on resistance is approximately 28 milliohms. On the other hand, with regard to the IGBT3, the on voltage was 1.8V, and the on resistance was approximately 36 milliohms. The MOSFET2 used has an on-resistance of 1 milliohm or less, and since the on-resistance of the main conducting part 11 side is lower than that of the auxiliary conducting part 12 side, the current easily flows to the main conducting part 11 side. That is, since the ratio of the currents flowing through the main conductive part 11 and the auxiliary conductive part 12 can be obtained from the ratio of the on-resistances, the ratio can be set to an appropriate value by appropriately selecting the number of elements connected in parallel. For example, a large number of appropriately selected elements can be connected in parallel to the main conductive portion 11 side to set the on-resistance ratio to the auxiliary conductive portion 12 to a desired appropriate value. Alternatively, for example, it is also possible to intentionally increase the on-resistance by selecting an element to be applied with priority given to the switching speed, using a trade-off relationship between the switching speed and the on-resistance on the auxiliary conducting portion 12 side.

The description returns to the current interruption operation. Next, as shown in fig. 3 and (III) of fig. 4, the voltage application from the control circuit 4 to the gate of the MOSFET2 is stopped, and the MOSFET2 is turned off at a timing t 3. Since the MOSFET2 can be turned off within several 10ns as described above, for example, it is in a non-conductive state immediately after the voltage application to the gate is stopped.

In this stage, the thyristor 1 is kept on and off (disconnected) between the anode and the cathode in a state where avalanche breakdown occurs. In the separately excited thyristor 1, once avalanche breakdown occurs, if only the voltage application to the gate is stopped, the avalanche breakdown does not stop. However, in the present embodiment, since the MOSFET2 is first brought into the non-conductive state, the potential difference generated between the terminals of the MOSFET2 is applied as a reverse bias to the gate of the thyristor 1. By this reverse bias, the charge of the thyristor 1 can be extracted. Then, in a state where the electric charge of the thyristor 1 is extracted, the voltage application to the gate of the thyristor 1 is stopped after the time difference Δ T from the stop of the voltage application to the gate of the MOSFET 2. Thus, at timing t4, thyristor 1 is turned off and becomes non-conductive.

At a timing t4, since thyristor 1 and MOSFET2 are in a non-conductive state, main conductive part 11 is completely cut off, and a current flows through auxiliary conductive part 12. In the auxiliary conduction part 12, the IGBT3 is turned on, and the low-voltage MOSFET2 is turned off at a time t3 for cutting off the current, and a delay time td is set_offAfter that, the voltage application from the control circuit 4 to the gate of the IGBT3 is stopped, and the IGBT3 is turned off at the timing t 5. The IGBT3 is a semiconductor switching element capable of performing a switching operation at a relatively high speed, and therefore is rapidly brought into a non-conductive state. This also cuts off the auxiliary conduction portion 12, and the entire composite semiconductor switch 10 completes the current cutting operation.

(action)

As described above, according to the configuration of the present embodiment, the current conduction loss can be reduced. Specifically, since the MOSFET2 has an on-resistance of several milliohms when the rated voltage is of the order of several 10V, and the IGBT3 can perform a switching operation at high speed, and the auxiliary conduction unit 12 becomes non-conductive in an extremely short time, the current conduction loss can be considered as a loss amount of one thyristor 1 (first semiconductor switching element) in the main conduction unit 11, substantially without considering the current conduction loss in the MOSFET2 and the IGBT 3. Therefore, the current conduction loss of the entire composite semiconductor switch 10 is smaller than that of the conventional technique in which, for example, a series circuit is formed by a plurality of semiconductor switching elements.

In addition, according to the configuration of the present embodiment, high-speed current interruption can be performed. Specifically, in the above example, the MOSFET2 can be turned off within several 10ns, and the thyristor 1 can also be turned off quickly by appropriately setting the timing of application of the reverse bias generated by the MOSFET2 that is turned off and application of the voltage to the gate from the control circuit 4. Since the IGBT3 is a semiconductor switching element capable of performing a relatively high-speed switching operation, the IGBT can be quickly placed in a non-conducting state by appropriately setting the timing at which the application of voltage to the gate of the IGBT3 is stopped after the thyristor 1 is turned off. Therefore, the entire composite semiconductor switch 10 can cut off the current at high speed.

Since the time during which the current is turned on can be short in the current interrupting operation on the side of the auxiliary conducting portion 12, it is sufficient that the current capacity of the IGBT3 provided on the side of the auxiliary conducting portion 12 is the rated current capacity for a short time. For example, under the above-described simulation conditions, the delay time td from turning on the IGBT3 to turning on the thyristor 1 (and the low-voltage MOSFET 2) is set in consideration of the switching speed described in the data table_onFrom about 1 to about 2 μ sec. Since the IGBT3 can be turned on only for a short time, the size and cost of the element can be reduced.

Further, according to the configuration of the present embodiment, it is possible to prevent the thyristor 1 having no self-turn-off function from being turned on erroneously due to the influence of residual charges.

This point will be explained in detail. In principle, in a thyristor having no self-turn-off function, after avalanche breakdown occurs when a voltage is applied to a gate once and the thyristor is turned on (turned on), if the voltage application to the gate is simply stopped, the avalanche breakdown is not stopped and the thyristor is still turned on. In this regard, the present inventors have made various verifications in connection with the above-described configuration, and have obtained the following findings: even in a state where no current flows to the thyristor in the on state (the thyristor 1 in the above-described configuration), the conduction of the current may be restarted in a very short time when no current flows because the voltage at the time when the parallel-connected IGBT3 is turned off is applied between one turn of the anode-cathode-low-voltage MOSFET2 of the thyristor 1. Hereinafter, in this specification, such a phenomenon of the thyristor 1 is referred to as a false turn-on phenomenon.

The present inventors have conducted various experiments to further verify that the following findings are obtained with respect to avoiding the false-connection phenomenon. First, it was found that, by performing the off control of the MOSFET2 connected in series with the thyristor 1 earlier than the thyristor 1, the potential difference generated between the terminals of the MOSFET2 is applied to the thyristor 1 as a reverse bias, but if the voltage application to the gate of the thyristor 1 is stopped in a state where the reverse bias is not applied to a sufficient magnitude, that is, the reverse bias is not applied to a sufficient magnitude to extract the electric charge between the anode and the cathode of the thyristor 1, the thyristor 1 may generate a false turn-on phenomenon. Therefore, in the present invention, the time difference Δ T is set until the voltage application to the gate of the thyristor 1 is stopped after the MOSFET2 is turned off, that is, the voltage application to the gate of the MOSFET2 is stopped. If Δ T is too short, the reverse bias voltage described above does not become a magnitude sufficient to pull out the charge of the thyristor 1. On the other hand, if Δ T is too long, the current cannot be cut off at high speed. In view of these circumstances, it is preferable to appropriately set Δ T so that a reverse bias voltage sufficient to extract the charge of the thyristor 1 can be obtained according to various conditions such as specifications in actual use. Therefore, a configuration can be adopted in which Δ T can be set to the gate pulse distribution circuit 42 from the outside. Alternatively, when the conditions in actual use are known in advance and the preferable value of Δ T is known in advance, the gate pulse distribution circuit 42 may hold Δ T of the preferable value.

Therefore, according to the configuration of the present embodiment, even if the thyristor 1 having no self-turn-off function is used, the thyristor 1 can be prevented from being turned on erroneously in the current interruption operation by a relatively simple circuit configuration, and the operation of the compound semiconductor switch 10 can be stabilized.

(second embodiment)

IN the first embodiment, a description has been given of a case where the current to be cut off by the composite semiconductor switch 10 is a direct current flowing from the input terminal IN to the output terminal OUT. However, in actual use, it is conceivable that the composite semiconductor switch 10 of the present invention is expected to be applied to a demand for a distribution board using, for example, an alternating current. In such a case, it is preferable to adopt a configuration in which a plurality of main conductive parts 11 are provided so as to be able to cope with both positive and negative polarities. Hereinafter, the composite semiconductor switch 10 having such a structure will be described in detail. The same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

(Structure)

As shown in fig. 5, the compound semiconductor switch 10 according to the present embodiment includes thyristors 1 and 1a, MOSFETs 2 and 2a, and IGBTs 3 and 3 a. Further, the compound semiconductor switch 10 includes a control circuit 4 (not shown) as in the first embodiment, and the control circuit 4 is connected to an external control device 5 (not shown). As for the control circuit 4 and the control device 5, a known technique can be applied as in the first embodiment, and therefore, the description thereof will be omitted below. The composite semiconductor switch 10 includes a first terminal a and a second terminal B instead of the input terminal IN and the output terminal OUT IN the first embodiment.

In the present embodiment, the thyristor 1 and the MOSFET2 form the first main conduction part 11, as in the first embodiment. The thyristor 1a and the MOSFET 2a form a second main conductor 11a, are connected in the same manner as the first main conductor 11, and are cascaded (cascade) with the first main conductor 11. More specifically, the thyristor 1a and the MOSFET 2a form a second main conduction part 11a, the second main conduction part 11a being connected in antiparallel with the first main conduction part 11, the direction of current flow being in the opposite direction to the first main conduction part 11.

IGBT3 and IGBT 3a are connected in series to form auxiliary conducting portion 12. The auxiliary conduction part 12 is connected in parallel to the first main conduction part 11 and the second main conduction part 11 a. In the present embodiment, since a current flows in both directions, for example, an IGBT having a diode connected in antiparallel is used for the IGBT3 and the IGBT3 a. In this case, the collector of the IGBT3 and the collector of the IGBT 3a are connected to each other, the emitter of the IGBT3 is connected to the second terminal B, and the emitter of the IGBT 3a is connected to the first terminal a. The diodes are connected from the emitters to the collectors of the IGBTs 3, 3 a.

The first terminal a is provided between the thyristor 1 and MOSFET 2a side end in the first main conduction part 11 and the second main conduction part 11a and the IGBT 3a side end in the auxiliary conduction part 12. The second terminal B is provided between the end on the MOSFET2 and thyristor 1a side in the first main conduction part 11 and the second main conduction part 11a and the end on the IGBT3 side in the auxiliary conduction part 12. Hereinafter, in order to easily understand the present invention, a case where a current flows from the first terminal a to the second terminal B is described as a positive polarity, and a case where a current flows from the second terminal B to the first terminal a is described as a negative polarity.

(action)

Next, the current interruption operation of the composite semiconductor switch 10 configured as described above will be described in detail with reference to fig. 6 and 7. Hereinafter, a current interruption operation performed when the current has a positive polarity will be described as a representative example.

First, as shown in fig. 6 and (I) of fig. 7, a voltage is applied to the gate of the IGBT3 to turn on the IGBT3 at a timing t 1. In this case, a current flows through the diode of the IGBT 3a and the IGBT3 from the first terminal a toward the second terminal B.

Next, in order to cause a current to flow to the first main conduction part 11, as shown in fig. 6 and (II) of fig. 7, a delay time td after a voltage is applied to the gate of the IGBT3_onThereafter, a voltage is applied to the gates of the thyristor 1 and the MOSFET2 to turn on the thyristor 1 and the MOSFET2 at timing t 2. Thereby, the first main conduction part 11 is turned on, and most of the current flows through the first main conduction part 11. Furthermore, in this caseWhether or not the thyristor 1a and the low-voltage MOSFET 2a are turned on by applying a voltage to the gates of the thyristor 1a and the low-voltage MOSFET 2a is arbitrary. However, in the case of the configuration in which the thyristor 1a and the low-voltage MOSFET 2a are also turned on in the same manner as the thyristor 1 and the low-voltage MOSFET2, since the direction in which the current flows is opposite to the conduction direction of the second main conduction portion 11a, for example, a large current in the opposite direction may be applied to cause element breakdown of the low-voltage MOSFET 2a and the thyristor 1a, it is preferable to adopt control in which the thyristor 1a and the low-voltage MOSFET 2a are not turned on.

Next, as shown in fig. 6 and (III) of fig. 7, before the thyristor 1 is turned off, the application of the voltage to the gate of the MOSFET2 is stopped to turn off the MOSFET2 at timing t 3. The reason why the MOSFET2 is turned off earlier than the thyristor 1 is to provide a reverse bias voltage sufficient to pull out the charge of the thyristor 1, as in the first embodiment.

Next, after the time difference Δ T from the stop of the application of the voltage to the gate of the MOSFET2, the application of the voltage to the gates of the thyristors 1 and 1a is stopped, and the thyristors 1 and 1a are turned off at the timing T4. The thyristor 1 is charged by the reverse bias applied after the time difference Δ T, and therefore, the false turn-on phenomenon can be prevented as in the first embodiment.

Since the first main conduction part 11 is non-conductive, a current flows through the auxiliary conduction part 12 as shown in fig. 6 and (III) of fig. 7. Therefore, td after the voltage application to the gate of the low-voltage MOSFET2 is stopped_offThereafter, the application of the voltage to the gate of the IGBT3 is stopped to turn off the IGBT3 at the timing t 5. Thus, even if the current flowing from the first terminal a toward the second terminal B passes through the diode connected in anti-parallel with the IGBT 3a, the IGBT3 is turned off and therefore does not reach the second terminal B. Therefore, the operation of cutting off the current is completed by the entire composite semiconductor switch 10.

When a current flows from the second terminal B to the first terminal a, that is, when the current has a negative polarity, the on/off operations of the MOSFET 2a, the thyristor 1a, and the IGBT 3a may be controlled in the same order as the above-described control.

As described above, according to the present embodiment, even when the current to be interrupted is an alternating current, the same operation and effect as those of the first embodiment can be obtained.

(other embodiments)

The present invention is not limited to the above-described embodiments, and various modifications and applications can be made. For example, in the above-described embodiment, the case where the second semiconductor switching element is an IGBT has been described as an example. However, for example, in applications where a faster switching speed is required but the withstand voltage can be lower than when using an IGBT, a power MOSFET may be used instead of the IGBT. In this case, by connecting the MOSFET to the auxiliary conducting portion 12 so that a current flows from the source to the drain of the MOSFET, it is expected that a current conduction loss can be further reduced by a so-called synchronous rectification effect.

In the second embodiment, the case where IGBTs having diodes connected in antiparallel are used as the second semiconductor switching elements 3 and 3a, respectively, has been described as an example, but reverse blocking IGBTs (RB-IGBTs) may be used. In this case, although the IGBTs 3 and 3a are connected in reverse series in the second embodiment, similar operations and effects can be obtained by connecting RB-IGBTs in reverse parallel.

Further, for example, by using a semiconductor switching element formed of a wide band gap material such as silicon carbide as the second semiconductor switching element and using a high withstand voltage type thyristor or the like as the thyristor 1, a higher withstand voltage can be obtained than in the embodiment, and the application of flowing a larger current can be dealt with.

In the above-described embodiment, the case where the first semiconductor switching element 1 is a thyristor having no self-turn-off function has been described as an example, but, for example, a GTO thyristor may be used. In this case, although the GTO thyristor can be turned on and off in principle in accordance with the voltage application to the gate, an effect of contributing to the turn-off operation of the GTO thyristor can be expected by turning off the MOSFET2 and applying a reverse bias to the GTO thyristor as in the above-described embodiment.

Claims (8)

1. A current interrupter comprising a main conduction part as a conduction part of a current and an auxiliary conduction part connected in parallel to the main conduction part,

the main conduction part includes a conduction part switching element connected in series with the first semiconductor switching element for switching conduction part by on/off operation of the conduction part switching element, and a first semiconductor switching element having no self-turn-off function,

the auxiliary conduction part includes a second semiconductor switching element,

the current interrupter includes a control circuit that controls on and off operations of the first semiconductor switching element, the conduction part switching element, and the second semiconductor switching element,

the control circuit controls the conduction part switching element and the first semiconductor switching element in this order to turn on and off the main conduction part,

the control circuit controls the conduction part switching element and the first semiconductor switching element with a preset time difference Δ T when the main conduction part is cut off, the time difference Δ T being a time for which a reverse bias sufficient for extracting charges of the first semiconductor switching element can be obtained.

2. The current interrupter of claim 1,

the control circuit applies a reverse bias to the gate of the first semiconductor switching element when the main conductive portion is turned off.

3. The current disconnector according to claim 1 or 2,

the control circuit turns on the second semiconductor switching element and then turns on the first semiconductor switching element when the first semiconductor switching element, the conduction section switching element, and the second semiconductor switching element are in an off state.

4. The current interrupter according to claim 3,

the control circuit is externally supplied with one control signal, and the control circuit varies the timings of the on and off operations of the first semiconductor switching element, the conduction portion switching element, and the second semiconductor switching element by giving a predetermined time difference to the one control signal.

5. The current disconnector according to claim 1 or 2,

the first semiconductor switching element, the conduction part switching element, and the second semiconductor switching element are each composed of a thyristor, a MOSFET, and an IGBT.

6. A current interrupter comprising a main conduction part as a conduction part of a current and an auxiliary conduction part connected in parallel to the main conduction part,

in the main conduction part, a series circuit including a conduction part switching element and a first semiconductor switching element having no self-turn-off function are connected in inverse parallel with each other,

in the auxiliary conduction part, parallel circuits formed by connecting diodes in reverse parallel to the second semiconductor switching elements are connected in reverse series with each other to form a bidirectional conduction path,

the current interrupter includes a control circuit that controls on and off operations of the first semiconductor switching element, the conduction part switching element, and the second semiconductor switching element,

the control circuit controls the conduction part switching element and the first semiconductor switching element in this order to turn on and off the main conduction part,

the control circuit controls the conduction part switching element and the first semiconductor switching element with a preset time difference Δ T when the main conduction part is cut off, the time difference Δ T being a time for which a reverse bias sufficient for extracting charges of the first semiconductor switching element can be obtained.

7. The current interrupter of claim 6,

the control circuit applies a reverse bias to the gate of the first semiconductor switching element when the main conductive portion is turned off.

8. The current interrupter according to claim 6 or 7,

the first semiconductor switching element, the conduction part switching element, and the second semiconductor switching element are each composed of a thyristor, a MOSFET, and an IGBT.

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