JP2019153976A - DC circuit breaker - Google Patents

Abstract

To provide a dc circuit breaker capable of suppressing extension of the time required for shutdown of an electric current due to extension of current-limiting time by a voltage clamp section.SOLUTION: A semiconductor dc circuit breaker 100, that is, a dc circuit breaker connected between a dc power supply 101 and a load 102, includes: an IGBT 1; a MOSFET 2 connected in parallel to the IGBT 1 and switching at a higher speed than the IGBT 1; and a MOV 3 connected in parallel to each of the MOSFET 2 and the IGBT 1. The semiconductor dc circuit breaker 100 is configured to shut down a dc circuit by turning off the IGBT 1 after the MOSFET 2 is off.SELECTED DRAWING: Figure 3

Description

  In particular, the present invention relates to a DC circuit breaker in which a bipolar switching element and a unipolar switching element are connected in parallel.

  Conventionally, a power semiconductor module for high-speed switching in which a bipolar switching element and a unipolar switching element are connected in parallel is known (see, for example, Patent Document 1).

  The power semiconductor module disclosed in Patent Document 1 is used in a power conversion device such as an inverter. The power semiconductor module includes a unipolar switching element (SiC-MOSFET) and a bipolar switching element (Si-IGBT), and the unipolar switching element and the bipolar switching element are connected in parallel.

  When turning off the power semiconductor module, first, the bipolar switching element is turned off first. At this time, the unipolar switching element is on. Further, after the bipolar switching element is turned off, the unipolar switching element is turned off. Since the turn-off loss of the unipolar switching element is relatively smaller than the turn-off loss of the bipolar switching element, the turn-off loss of the power semiconductor module is relatively small.

JP2013-59190A

  When the semiconductor switch of Patent Document 1 is applied to a DC circuit breaker, the current flowing through the power semiconductor module is limited when the power semiconductor module is off (consumes magnetic energy on the circuit and makes it zero). In addition, there may be a voltage clamp portion connected in parallel to each of the bipolar switching element and the unipolar switching element. In this case, it is known that when the switching element is turned off, a surge voltage is generated in the parasitic inductance between the voltage clamp part and the unipolar switching element due to current flowing from the switching element to the voltage clamp part. .

  In addition, since a voltage in which the surge voltage and the clamp voltage of the voltage clamp unit are combined is applied to the semiconductor switching element, the sum of the surge voltage and the clamp voltage of the voltage clamp unit is prevented so that the semiconductor switching element is not destroyed due to the breakdown of the breakdown voltage. However, it needs to be smaller than the breakdown voltage of the semiconductor switching element. Therefore, when the surge voltage is relatively large, it is necessary to set the clamp voltage relatively small.

  Here, the magnitude of the surge voltage generated in the semiconductor switching element depends on the characteristics of the switching element that is turned off later (switching element that commutates current to the voltage clamp portion), and the switching speed of the switching element that is turned off later is high. It gets bigger. Therefore, when the switching element of Patent Document 1 is applied to a DC circuit breaker and a voltage clamp unit is provided, a unipolar switching element with a high switching speed is turned off after a bipolar switching element with a low switching speed. Surge voltage increases. For this reason, it is necessary to set the clamp voltage of a voltage clamp part small. Further, it is known that the current limiting time by the voltage clamp unit becomes longer as the clamp voltage of the voltage clamp unit is smaller. Therefore, in the case where the voltage clamp unit is provided in Patent Document 1, it is necessary to make the clamp voltage relatively small, so that the current limiting time by the voltage clamp unit becomes long, and the time taken to cut off the current becomes long. There is a point.

  The present invention has been made to solve the above-described problems, and one object of the present invention is to reduce the time taken to cut off the current due to the fact that the current limiting time by the voltage clamp unit becomes longer. It is providing the direct-current circuit breaker which can suppress becoming long.

  In order to achieve the above object, a DC circuit breaker according to one aspect of the present invention is a DC circuit breaker connected between a DC power supply and a load, and is parallel to the bipolar switching element and the bipolar switching element. And a unipolar switching element that switches at a higher speed than the bipolar switching element, and a voltage clamp connected in parallel with each of the unipolar switching element and the bipolar switching element. After the element is turned off, the bipolar switching element is turned off to cut off the direct current.

  Here, the magnitude of the surge voltage generated in the voltage clamp part depends on the characteristics of the switching element that is turned off later (the switching element that commutates current to the voltage clamp part), and the switching speed of the switching element that is turned off later is high. It gets bigger. Therefore, in the DC circuit breaker according to one aspect of the present invention, as described above, after the unipolar switching element is turned off, the bipolar switching element that switches at a lower speed than the unipolar switching element is turned off. The surge voltage generated in the voltage clamp portion can be made relatively small. Thereby, a clamp voltage can be set comparatively large. Here, the current limiting time by the voltage clamp unit becomes shorter as the clamp voltage of the voltage clamp unit is larger. Thereby, it can suppress that the current limiting time by a voltage clamp part becomes long. As a result, it is possible to suppress an increase in the time taken to cut off the direct current due to an increase in the current limiting time by the voltage clamp unit. The current limiting means that the value of the current flowing through the voltage clamp unit is reduced to a predetermined value (for example, zero).

  Moreover, since it can suppress that current-limiting time becomes long, it can suppress that the energy consumption by a voltage clamp part becomes large. As a result, it is possible to suppress an increase in the capacity of the voltage clamp unit.

  In the DC circuit breaker according to the one aspect, preferably, the bipolar switching element is turned off after the current value flowing through the unipolar switching element becomes a predetermined value by turning off the unipolar switching element. The DC current is cut off. If comprised in this way, it can suppress that a bipolar switching element is turned off in the state in which the comparatively big electric current is flowing into the unipolar switching element. As a result, it is possible to suppress the commutation of current from the unipolar switching element to the voltage clamp portion, and thus it is possible to more reliably suppress the occurrence of a surge voltage due to the unipolar switching element.

  The DC circuit breaker according to the above aspect is preferably configured such that the bipolar switching element is turned off after a predetermined time after sending a signal to turn off to the unipolar switching element. If comprised in this way, a bipolar type switching element can be turned off at fixed timing with respect to the timing which sends the signal which turns off to a unipolar type switching element. As a result, the timing for turning off the bipolar switching element can be easily controlled.

  In the DC circuit breaker in which the bipolar switching element is turned off after the value of the current flowing through the unipolar switching element becomes zero, the unipolar switching element is preferably detected by a current sensor that detects the current value flowing through the unipolar switching element. The bipolar switching element is configured to be turned off when it is detected that the value of the current flowing through the terminal becomes zero. If comprised in this way, after the value of the electric current which flows into a unipolar type switching element becomes zero reliably, a bipolar type switching element can be turned off.

  The DC circuit breaker according to the above aspect preferably further includes an antiparallel bipolar switching element connected in antiparallel to the bipolar switching element, and the antiparallel bipolar switching is performed after the unipolar switching element is turned off. When the element is turned off, the direct current is cut off. With this configuration, the bipolar switching element and the anti-parallel bipolar switching element are used to cut off the direct current due to the fact that the current limiting time by the voltage clamp unit becomes longer regardless of the direction in which the direct current flows. It can suppress that time becomes long.

  The DC circuit breaker according to the above aspect is preferably configured to conduct a DC current when both the unipolar switching element and the bipolar switching element are turned on. According to this configuration, when one of the unipolar switching element and the bipolar switching element is turned on and the direct current is conducted, the unipolar switching is performed when the direct current is switched from the conduction state to the cutoff state. It is possible to easily control the bipolar switching element to be turned off after the type switching element is turned off.

  In the DC circuit breaker according to the above aspect, the bipolar switching element preferably includes an insulated gate bipolar transistor, and the unipolar switching element includes a field effect transistor. Here, the field effect transistor switches faster than the insulated gate bipolar transistor. Therefore, it is possible to suppress an increase in the time taken to cut off the direct current by using elements having a relatively simple structure such as a field effect transistor and an insulated gate bipolar transistor.

  According to the present invention, as described above, it is possible to suppress an increase in the time taken to cut off the current due to an increase in the current limiting time by the voltage clamp unit.

It is the figure which showed the circuit structure by which the DC circuit breaker by 1st and 2nd embodiment is arrange | positioned. It is the figure which showed the structure of the DC circuit breaker by 1st Embodiment. It is a figure for demonstrating the state by which the unipolar type switching element was turned off in the DC circuit breaker by 1st Embodiment. It is a figure for demonstrating the timing which each switching element of the DC circuit breaker by 1st Embodiment turns off. It is a figure for demonstrating the state by which the unipolar type switching element and the bipolar type switching element were turned off in the DC circuit breaker by 1st Embodiment. It is a figure for demonstrating the state of the DC circuit breaker at the time of conduction | electrical_connection by 1st Embodiment. It is a figure for demonstrating the relationship between the load factor and loss of a unipolar type switching element and a bipolar type switching element in the DC circuit breaker by 1st Embodiment. It is the figure which showed the structure of the DC circuit breaker by 2nd Embodiment. It is a figure for demonstrating the method to turn off the unipolar type | mold switching element in the DC circuit breaker by the modification of 1st Embodiment.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below with reference to the drawings.

[First Embodiment]
With reference to FIGS. 1-7, the structure of the semiconductor DC circuit breaker 100 by 1st Embodiment is demonstrated. The semiconductor DC circuit breaker 100 is an example of the “DC circuit breaker” in the claims.

  As shown in FIG. 1, the semiconductor DC circuit breaker 100 is connected between a DC power supply 101 and a load 102. The DC power supply 101 is a device that generates DC power, such as solar power generation or a fuel cell. Further, the DC power supply 101 may be a DC power supply obtained by rectifying an AC system. The semiconductor DC circuit breaker 100 is provided to interrupt a DC current flowing between the DC power supply 101 and the load 102. In addition, a current limiting reactor 103 is provided between the DC power source 101 and the semiconductor DC circuit breaker 100 in order to limit the short circuit current of the circuit.

(Configuration of semiconductor DC circuit breaker)
As shown in FIG. 2, the semiconductor DC circuit breaker 100 includes an IGBT (Insulated Gate Bipolar Transistor) 1. The IGBT 1 may have a diode connected in antiparallel. The semiconductor DC circuit breaker 100 includes a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) 2 connected in parallel to the IGBT 1. Further, the MOSFET 2 switches at a higher speed than the IGBT 1. The IGBT 1 and the MOSFET 2 are examples of “bipolar switching element” and “unipolar switching element” in the claims, respectively.

  The drain terminal D of the MOSFET 2 is connected to the current limiting reactor 103 (see FIG. 1), and the source terminal S of the MOSFET 2 is connected to the load 102 (see FIG. 1).

  The MOSFET 2 is an N-channel type MOSFET. Although not shown, the MOSFET 2 has a parasitic diode inside. Specifically, the parasitic diode of the MOSFET 2 functions to cut off the current from the drain terminal D to the source terminal S when the MOSFET 2 is turned off. The MOSFET 2 may be a P-channel type MOSFET.

  Further, the semiconductor DC circuit breaker 100 includes a MOV (Metal Oxide Varistor) 3 connected in parallel with each of the IGBT 1 and the MOSFET 2. By consuming magnetic energy on the circuit by MOV3, it is possible to consume magnetic energy more effectively (even with a large current) more effectively than when magnetic energy is consumed only by switching of IGBT1 and MOSFET2. . MOV3 is an example of the “voltage clamp part” in the claims.

(Operation of semiconductor DC circuit breaker)
Next, the operation of the semiconductor DC circuit breaker 100 will be described with reference to FIGS. In the first embodiment, a case in which a direct current flows from the direct current power source 101 toward the load 102 will be described.

(When semiconductor DC circuit breaker is shut off)
Here, in the first embodiment, the semiconductor DC circuit breaker 100 is configured to interrupt the DC current by turning off the IGBT 1 after the MOSFET 2 is turned off. Specifically, as shown in FIG. 3, MOSFET 2 is first turned off from a state where both IGBT 1 and MOSFET 2 are on (see FIG. 6) when semiconductor DC circuit breaker 100 is conductive. At this time, the current flowing in the MOSFET 2 is commutated to the IGBT 1, and the current (see the broken line arrow) flows only in the IGBT 1.

  In the first embodiment, the semiconductor DC breaker 100 is configured to cut off the DC current by turning off the IGBT 1 after the MOSFET 2 is turned off and the current value flowing through the MOSFET 2 becomes zero. . Note that zero is an example of a “predetermined value” in the claims.

  Specifically, as shown in FIG. 4, after sending a signal to turn off to MOSFET 2, IGBT 1 is turned off after a preset time Δt1 (eg, 1 μs). That is, an off signal is automatically transmitted to the IGBT 1 (from a control unit not shown) after a time Δt1 from the transmission of the off signal to the MOSFET 2 (from a control unit not shown). The time Δt1 is a value set in advance according to the characteristics of the MOSFET 2. An off signal is simultaneously transmitted from the control unit (not shown) to each switching element (IGBT1 and MOSFET 2), and at the timing when the off signal is input to the MOSFET 2 by a circuit between the control unit (not shown) and each switching element. On the other hand, the timing at which the off signal is input to the IGBT 1 may be delayed. The time Δt1 is an example of the “predetermined time” in the claims.

  Specifically, an off signal is transmitted to MOSFET 2 at time t1. Then, at time t2 after time t1 from time t1, the value of the current flowing through MOSFET 2 becomes zero. Since current is commutated from MOSFET 2 to IGBT 1 from time t1 to time t2, the current value of IGBT 1 increases.

  Further, an OFF signal is transmitted to the IGBT 1 at time t3 after time t2 and after time Δt3 (after time t1 and after time Δt1). Then, the current value flowing through the IGBT 1 becomes zero at time t4 after time t3 from time t3. Note that FIG. 4 is a schematic diagram, and the shape and the like of the current waveform may be different from actual ones.

  Note that, as shown in FIG. 5, when an OFF signal is transmitted to the IGBT 1, the current flowing in the IGBT 1 from time t 3 (see FIG. 4) to time t 4 (see FIG. 4) is commutated to MOV 3 ( (See dashed arrows). Then, a current limiting operation is performed by MOV3. In this current limiting operation, the magnetic energy on the circuit is consumed by MOV3, and the current is cut off.

  When the IGBT 1 is turned off and the current commutates to the MOV 3, the surge voltage value generated in the MOV 3 is the product of the circuit inductance (the wiring inductance between the IGBT 1 and the MOV 3) and the time rate of change of the current in the IGBT 1. It becomes. The clamp voltage of MOV3 is set so that the sum of the surge voltage generated in MOV3 and the clamp voltage is smaller than the withstand voltage of the switching elements (IGBT1 and MOSFET2).

In addition, the time t required for the current limiting operation by MOV3 (the time required for reducing the current value to zero) is the circuit inductance (L) and the maximum current (when short-circuited) as shown in the following equation (1). imax) divided by the difference between the clamp voltage (Vclamp) of MOV3 and the voltage (Vdc) of the DC power supply 101. That is, the larger the clamp voltage of MOV3, the shorter the time required for the current limiting operation.

  In the semiconductor DC circuit breaker 100, since the switching elements (IGBT1 and MOSFET2) do not require high-speed (repetitive) switching, the switching loss is almost negligible.

(When semiconductor DC circuit breaker is conducting)
In the first embodiment, as shown in FIG. 6, the semiconductor DC circuit breaker 100 is configured to conduct a DC current when both the MOSFET 2 and the IGBT 1 are turned on. In this case, the same voltage is applied to the MOSFET 2 and the IGBT 1.

  FIG. 7 illustrates the relationship between the load factor and loss of each switching element. The load factor means the magnitude of the current that constantly flows through the switching element. The magnitude of the loss is determined by the magnitude of the product of current and voltage.

  As shown in FIG. 7, the loss of MOSFET 2 changes in a quadratic function with respect to the load factor. Further, the loss of the IGBT 1 changes in a linear function with respect to the load factor. In the case of a light load (when the load factor is smaller than L), the loss of MOSFET 2 is smaller than the loss of IGBT 1. In the case of a heavy load (when the load factor is greater than L), the loss of IGBT 1 is smaller than the loss of MOSFET 2. While both elements are on, current is shunted according to the characteristics of the two switching elements.

  Specifically, in the case of a light load, the loss of MOSFET 2 is smaller than that of IGBT 1, so that a relatively large current flows through MOSFET 2. Note that no current flows through the IGBT 1 when a voltage necessary to turn on the IGBT 1 is not applied. In this case, a current flows only through the MOSFET 2. Further, the IGBT 1 may have a configuration in which a plurality of IGBTs are connected in parallel, and the MOSFET 2 may have a configuration in which a plurality of MOSFETs are connected in parallel. The ratio of shunting may be adjusted according to the number of elements of IGBT1 and MOSFET2.

  In the case of a heavy load, the current is shunted between the MOSFET 2 and the IGBT 1. In this case, a relatively large current flows through the IGBT 1 having excellent characteristics under heavy load. Thereby, in each of the light load and the heavy load, a larger amount of current can flow through the element having the lower loss, so that the conduction loss of the semiconductor DC circuit breaker 100 can be reduced.

  As a result, even in the case of a heavy load, the value of the current flowing through the MOSFET 2 becomes relatively small, so that the resistance value of the MOSFET 2 can be made relatively large. As a result, it is possible to suppress an increase in the chip area of MOSFET 2 (since the resistance value of MOSFET 2 and the chip area of MOSFET 2 are inversely proportional).

(Effect of 1st Embodiment)
In the first embodiment, the following effects can be obtained.

  In the first embodiment, as described above, the semiconductor DC circuit breaker 100 is configured to interrupt the DC current by turning off the IGBT 1 after the MOSFET 2 is turned off. Here, the magnitude of the surge voltage generated in MOV3 depends on the characteristics of a switching element that is turned off later (switching element that commutates current to MOV3), and increases as the switching speed of the switching element that turns off later increases. Accordingly, after the MOSFET 2 is turned off, the surge voltage generated in the MOV 3 can be made relatively small by turning off the IGBT 1 that switches at a lower speed than the MOSFET 2. Thereby, a clamp voltage can be set comparatively large. Here, the current limit time by MOV3 becomes shorter as the clamp voltage of MOV3 increases. Thereby, it can suppress that the current limit time by MOV3 becomes long. As a result, it is possible to suppress an increase in the time taken to cut off the direct current due to an increase in the current limiting time by MOV3.

  Moreover, since it can suppress that current limiting time becomes long, it can suppress that the energy consumption by MOV3 becomes large. As a result, an increase in the capacity of MOV3 can be suppressed.

  Further, it is possible to suppress an increase in the time taken to cut off the direct current by using elements having a relatively simple structure such as a field effect transistor (MOSFET) and an insulated gate bipolar transistor (IGBT).

  Further, in the first embodiment, as described above, after the current value flowing through the MOSFET 2 becomes zero due to the MOSFET 2 being turned off, the IGBT 1 is turned off to cut off the direct current. The circuit breaker 100 is configured. Thereby, it is possible to prevent the IGBT 1 from being turned off while a current is flowing through the MOSFET 2. As a result, current commutation from MOSFET 2 to MOV 3 can be suppressed, and generation of a surge voltage due to MOSFET 2 can be more reliably suppressed.

  In the first embodiment, as described above, the semiconductor DC circuit breaker 100 is configured such that the IGBT 1 is turned off after a preset time Δt1 after sending the signal to the MOSFET 2 to be turned off. Thereby, IGBT1 can be turned off at a fixed timing with respect to the timing of sending a signal to turn off to MOSFET2. As a result, it is possible to easily control the timing at which the IGBT 1 is turned off.

  In the first embodiment, as described above, the semiconductor DC circuit breaker 100 is configured so that a DC current is conducted when both the MOSFET 2 and the IGBT 1 are turned on. Thereby, compared with the case where one of the MOSFET 2 and the IGBT 1 is turned on and the DC current is conducted, the control for turning off the IGBT 1 after the MOSFET 2 is turned off at the time of transition from the conduction state of the DC current to the cutoff state is performed. It can be done easily.

[Second Embodiment]
Next, the configuration of the semiconductor DC circuit breaker 200 according to the second embodiment will be described with reference to FIG. The semiconductor DC circuit breaker 200 of the second embodiment includes an antiparallel IGBT 4. In addition, the same structure as the said 1st Embodiment attaches | subjects and shows the same code | symbol as 1st Embodiment, and abbreviate | omits description.

(Configuration of semiconductor DC circuit breaker)
As shown in FIG. 8, the semiconductor DC circuit breaker 200 includes an IGBT 11. The semiconductor DC circuit breaker 200 includes a MOSFET 12 connected in parallel with the IGBT 11. The MOSFET 12 includes a MOSFET 12a and a MOSFET 12b connected in series with each other. Each of the MOSFET 12a and the MOSFET 12b is an N-channel MOSFET. Each of MOSFET 12a and MOSFET 12b may be a P-channel type MOSFET. The IGBT 11 is an example of the “bipolar switching element” in the claims. The MOSFET 12 (MOSFET 12a and MOSFET 12b) is an example of the “unipolar switching element” in the claims.

  The drain terminal Da of the MOSFET 12a is connected to the current limiting reactor 103 (see FIG. 1), and the drain terminal Db of the MOSFET 12b is connected to the load 102 (see FIG. 1). Further, the source terminal Sa of the MOSFET 12a and the source terminal Sb of the MOSFET 12b are connected.

  Although not shown, each of the MOSFET 12a and the MOSFET 12b has a parasitic diode therein. Specifically, the parasitic diode of the MOSFET 12a functions to cut off the current from the drain terminal Da to the source terminal Sa. The parasitic diode of the MOSFET 12b functions to cut off the current from the drain terminal Db to the source terminal Sb.

  The semiconductor DC circuit breaker 200 includes an anti-parallel IGBT 4 that is connected to the IGBT 11 in anti-parallel. Each of the IGBT 11 and the anti-parallel IGBT 4 is a reverse blocking IGBT element having a sufficient withstand voltage against the reverse bias. The anti-parallel IGBT 4 is an example of the “anti-parallel bipolar switching element” in the claims.

  Further, each of the MOSFET 12a and the MOSFET 12b switches at a higher speed than the IGBT 11 and the antiparallel IGBT4.

  Here, in the second embodiment, the semiconductor DC circuit breaker 200 is configured to interrupt the DC current by turning off the anti-parallel IGBT 4 after the MOSFET 12b is turned off. Specifically, when cutting off the direct current flowing from the load 102 to the direct current power supply 101, the semiconductor DC breaker 200 cuts off the direct current by turning off the anti-parallel IGBT 4 after turning off the MOSFET 12b. Is configured to do. Further, in the case of interrupting a direct current flowing from the DC power supply 101 (see FIG. 1) to the load 102 (see FIG. 1), the semiconductor DC breaker 200 is turned off by turning off the IGBT 11 after the MOSFET 12a is turned off. The DC current is cut off.

  Other configurations of the second embodiment are the same as those of the first embodiment.

(Effect of 2nd Embodiment)
In the second embodiment, the following effects can be obtained.

  In the second embodiment, as described above, the semiconductor DC circuit breaker 200 is configured to interrupt the direct current by turning off the anti-parallel IGBT 4 after the MOSFET 12b is turned off. As a result, the IGBT 11 and the anti-parallel IGBT 4 can suppress an increase in the time required to cut off the direct current due to an increase in the current limiting time by the MOV3 regardless of the direction in which the direct current flows.

  The remaining effects of the second embodiment are similar to those of the aforementioned first embodiment.

[Modification]
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiment but by the scope of claims for patent, and further includes all modifications (modifications) within the meaning and scope equivalent to the scope of claims for patent.

  For example, in the first embodiment, an example in which the bipolar switching element (IGBT1) is turned off after a predetermined time (Δt1) after a signal to turn off is sent to the unipolar switching element (MOSFET 2). Although shown, the present invention is not limited to this. For example, as shown in FIG. 9, the semiconductor DC breaker 300 may be configured to turn off the bipolar switching element (IGBT1) using the current sensor 104.

  Specifically, the current sensor 104 detects a current value flowing through the MOSFET 2. The semiconductor DC circuit breaker 300 is configured such that the IGBT 1 is turned off when the current sensor 104 detects that the value of the current flowing through the MOSFET 2 has become zero. Specifically, when the current sensor 104 detects that the value of the current flowing through the MOSFET 2 has become zero, a signal is transmitted to a control unit (not shown). A control unit (not shown) transmits an off signal to the IGBT 1 when receiving the signal. Thereby, the IGBT 1 can be reliably turned off after the value of the current flowing through the MOSFET 2 becomes zero. In the configuration of the second embodiment, control using a current sensor may be performed.

  In the first and second embodiments, the example in which the bipolar switching elements (IGBT1, IGBT11) are turned off after the value of the current flowing through the unipolar switching elements (MOSFET2, MOSFET12) becomes zero has been shown. The present invention is not limited to this. For example, the bipolar switching elements (IGBT1, IGBT11) may be turned off after the value of the current flowing through the unipolar switching elements (MOSFET2, MOSFET12) becomes a predetermined value close to zero.

  In the first and second embodiments, the bipolar switching element is an insulated gate bipolar transistor (IGBT) and the unipolar switching element is a field effect transistor (MOSFET). The invention is not limited to this. For example, the bipolar switching element may be a BJT (Bipolar Junction Transistor) or a GTO (Gate Turn-Off Thyristor). Further, for example, the unipolar switching element may be a SIT (Static Induction Transistor) or the like.

  In the first and second embodiments, the example in which the MOV is used as the voltage clamp unit has been described. However, the present invention is not limited to this. For example, a Zener diode may be used as the voltage clamp unit.

  In the first embodiment, the example in which both the unipolar switching element (MOSFET 2) and the bipolar switching element (IGBT1) are turned on when conducting is shown. However, the present invention is not limited to this. For example, at the time of conduction, either one of the unipolar switching element (MOSFET 2) and the bipolar switching element (IGBT1) may be turned on.

  In the second embodiment, the bipolar switching element (IGBT 11) and the anti-parallel bipolar switching element (anti-parallel IGBT 4) are connected in parallel. However, the present invention is not limited to this. Absent. A series circuit of a bipolar switching element and a diode element, and a series circuit of an antiparallel bipolar switching element and a diode element may be connected in antiparallel.

1,11 IGBT (Bipolar type switching element)
2, 12, 12a, 12b MOSFET (unipolar switching element)
3 MOV (voltage clamp)
4 Reverse Parallel IGBT (Reverse Parallel Bipolar Switching Element)
100, 200, 300 Semiconductor DC circuit breaker (DC circuit breaker)
101 DC power supply 102 Load 104 Current sensor Δt1 time (predetermined time)

Claims (7)

A DC circuit breaker connected between a DC power source and a load,
A bipolar switching element;
A unipolar switching element connected in parallel to the bipolar switching element and switching at a higher speed than the bipolar switching element;
A voltage clamp unit connected in parallel with each of the unipolar switching element and the bipolar switching element,
A DC circuit breaker configured to interrupt a direct current by turning off the bipolar switching element after the unipolar switching element is turned off.   The direct current is cut off by turning off the bipolar switching element after the current value flowing through the unipolar switching element becomes zero by turning off the unipolar switching element. The DC circuit breaker according to claim 1.   3. The DC circuit breaker according to claim 1, wherein the bipolar switching element is turned off after a predetermined time after sending a signal to turn off to the unipolar switching element. 4. .   When the current sensor that detects the current value flowing through the unipolar switching element detects that the current value flowing through the unipolar switching element has reached a predetermined value, the bipolar switching element is turned off. The DC circuit breaker according to claim 2, which is configured as follows. An anti-parallel bipolar switching element connected in anti-parallel to the bipolar switching element;
5. The DC current is configured to be cut off by turning off the anti-parallel bipolar switching element after the unipolar switching element is turned off. 6. DC circuit breaker.   The DC circuit breaker according to any one of claims 1 to 5, wherein both the unipolar switching element and the bipolar switching element are turned on to conduct the DC current. The bipolar switching element includes an insulated gate bipolar transistor,
The DC breaker according to any one of claims 1 to 6, wherein the unipolar switching element includes a field effect transistor.

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