DC breaker

Abstract

This DC breaker (1), which is connected between a power supply and a load, comprises: a current-limiting mechanism (100) that has a semiconductor switch (11) and an MOV (12) which are connected in parallel; and an interruption mechanism (200) that has a mechanical switch (21) and a semiconductor switch (22) which are connected in parallel. The current-limiting mechanism (100) and the interruption mechanism (200) are connected in series. The impedance of the MOV (12) decreases when a voltage lower than the breakdown voltage of the semiconductor switch (11) is applied to the MOV (12).

Description

DC circuit breaker

[0001] The present disclosure relates to a DC circuit breaker.

[0002] Patent Document 1 discloses a technique for preventing contact wear without generating an arc.

[0003] International Publication No. 2017 / 150079

[0004] However, in the technique disclosed in Patent Document 1, when it is assumed that a short-circuit current is interrupted, the opening delay of the main circuit breaker, which is a mechanical switch, is large, and the short-circuit current increases before the opening is completed. When the short-circuit current increases, the overcurrent withstand capability of the mechanical switch and the semiconductor switch and the surge energy withstand capability of the surge absorber increase, so it is necessary to arrange a current-limiting reactor in series with the DC circuit breaker. Arranging the current-limiting reactor can reduce the increasing rate of the short-circuit current, but when the short-circuit current increases for a long time, the current-limiting reactor needs to be enlarged. That is, the circuit scale of the DC circuit breaker increases.

[0005] Therefore, the present disclosure provides a DC circuit breaker capable of reducing the circuit scale.

[0006] A DC circuit breaker according to the present disclosure is a DC circuit breaker connected between a power supply and a load, and includes: a current-limiting mechanism having a first self-extinguishing switch and a first voltage clamp circuit connected in parallel; and an interrupting mechanism having a mechanical switch and a second self-extinguishing switch connected in parallel, wherein the current-limiting mechanism and the interrupting mechanism are connected in series, and the impedance of the first voltage clamp circuit decreases when a voltage lower than the breakdown voltage of the first self-extinguishing switch is applied to the first voltage clamp circuit.

[0007] Note that these comprehensive or specific aspects may be implemented by a system, a method, an integrated circuit, a computer program, or a recording medium such as a computer-readable CD-ROM, and may also be implemented by any combination of a system, a method, an integrated circuit, a computer program, and a recording medium.

[0008] According to the DC circuit breaker of an aspect of the present disclosure, the circuit scale can be reduced.

[0009] This is a circuit diagram showing an example of a DC circuit breaker according to Embodiment 1. This is a diagram showing an example of a tripping sequence by a DC circuit breaker according to Embodiment 1. This is a circuit diagram showing an example of a DC circuit breaker according to Embodiment 2. This is a diagram showing an example of a tripping sequence by a DC circuit breaker according to Embodiment 2. This is a diagram showing an example of a closing sequence by a DC circuit breaker according to Embodiment 2. This is a diagram showing an example of a closing sequence by a DC circuit breaker according to Embodiment 2. This is a circuit diagram showing an example of a DC circuit breaker according to Embodiment 3. This is a circuit diagram showing an example of a DC circuit breaker according to Modification 1 of Embodiment 3. This is a circuit diagram showing an example of a DC circuit breaker according to Modification 2 of Embodiment 3. This is a circuit diagram showing an example of a DC circuit breaker according to Embodiment 4. This is a circuit diagram showing an example of a DC circuit breaker according to Modification 4 of Embodiment 4. This is a circuit diagram showing an example of a bootstrap circuit applied to a DC circuit breaker according to each embodiment. This is a circuit diagram showing an example of a bootstrap circuit applied to a DC circuit breaker according to Modifications 1 and 2 of Embodiment 3. This is a diagram showing an example of connecting other mechanical switches.

[0010] The embodiments will be described in detail below with reference to the drawings.

[0011] The embodiments described below are all general or specific examples. The numerical values, shapes, materials, components, arrangement and connection configurations of components, steps, and the order of steps shown in the following embodiments are examples only and are not intended to limit this disclosure.

[0012] (Embodiment 1) The DC circuit breaker according to Embodiment 1 will be described below.

[0013] Figure 1 is a circuit diagram showing an example of a DC circuit breaker 1 according to Embodiment 1.

[0014] DC circuit breaker 1 is a device connected between a power source and a load, and is used to interrupt the power line connecting the power source and the load. For example, DC circuit breaker 1 interrupts the power line when a short-circuit fault occurs.

[0015] The DC circuit breaker 1 comprises a current-limiting mechanism 100 and a circuit-breaking mechanism 200. The current-limiting mechanism 100 and the circuit-breaking mechanism 200 are connected in series.

[0016] The current limiting mechanism 100 includes a semiconductor switch 11 and a MOV (Metal Oxide Variistor) 12 connected in parallel. The semiconductor switch 11 is an example of a first self-extinguishing switch, and the MOV 12 is an example of a first voltage clamp circuit. The semiconductor switch 11 is, for example, an IGBT (Insulated Gate Bipolar Transistor), but may also be an FET (Field Effect Transistor) or a bipolar transistor. The MOV 12 is an element that conducts when the voltage applied to the MOV 12 is above a specific voltage, and shuts off when the voltage applied to the MOV 12 is below a specific voltage.

[0017] In the following description, an example in which the first voltage clamp circuit is MOV12 will be explained. However, the first voltage clamp circuit is not particularly limited as long as it is a circuit whose impedance decreases when a voltage lower than the breakdown voltage of the semiconductor switch 11 is applied to the first voltage clamp circuit. For example, instead of MOV12, an MPS (Merged PIN Schottky) diode, a Zener diode, or a TVS (Transient Voltage Suppressor) diode may be provided. In other words, the first voltage clamp circuit may include any clamp element from among a varistor, an MPS diode, a Zener diode, and a TVS diode. That is, examples of circuits whose impedance decreases when a voltage lower than the breakdown voltage of the semiconductor switch 11 is applied include varistors, MPS diodes, Zener diodes, and TVS diodes.

[0018] The interruption mechanism 200 has a mechanical switch 21 and a semiconductor switch 22 connected in parallel. The semiconductor switch 22 is an example of a second self-extinguishing switch. The semiconductor switch 22 is, for example, an IGBT, but may also be an FET or a bipolar transistor.

[0019] Figure 1 shows the body diodes of each semiconductor switch, and each body diode is connected in parallel with the corresponding semiconductor switch in the equivalent circuit. Note that antiparallel diodes may actually be connected to each semiconductor switch.

[0020] Although not shown in the figures, the DC circuit breaker 1 may also include a current-limiting reactor connected in series with the current-limiting mechanism 100 and the interruption mechanism 200. A current-limiting reactor is provided because an increase in short-circuit current increases the overcurrent withstand capacity of the mechanical switch 21 and the semiconductor switch 11, as well as the surge energy withstand capacity of the surge absorber.

[0021] In Figure 1, an example is shown in which the interruption mechanism 200 is connected to the power supply side and the current limiting mechanism 100 is connected to the load side. However, the current limiting mechanism 100 may be connected to the power supply side and the interruption mechanism 200 may be connected to the load side. Furthermore, the semiconductor switches 11 and 22 may each be bidirectional switches, and the power supply and load may be swapped in Figure 1. In this case, the power supply and load may be swapped in Figure 1, and the current limiting mechanism 100 and the interruption mechanism 200 may also be swapped.

[0022] Next, we will explain the opening operation, or in other words, the tripping operation, of the DC circuit breaker 1 when a short-circuit fault occurs, using Figure 2.

[0023] Figure 2 is a diagram showing an example of a tripping sequence by a DC circuit breaker 1 according to Embodiment 1. Figure 2(a) shows the DC circuit breaker 1 in the closed state, Figure 2(b) shows the DC circuit breaker 1 during current limiting operation, Figure 2(c) shows the DC circuit breaker 1 during commutation operation, Figure 2(d) shows the DC circuit breaker 1 during demagnetization operation, and Figure 2(e) shows the DC circuit breaker 1 in the tripped state.

[0024] As shown in Figure 2(a), when the DC circuit breaker 1 is in the closed state, that is, when the semiconductor switch 11 and the mechanical switch 21 are in the ON state, current flows through the mechanical switch 21 and the semiconductor switch 11. Since the semiconductor switch 11 and the mechanical switch 21 are in the ON state, the terminal voltage of the DC circuit breaker 1 (specifically, the voltage between the power supply side terminal and the load side terminal of the DC circuit breaker 1) is approximately 0. Note that in the closed state, the semiconductor switch 22 may be in either the ON or OFF state.

[0025] As shown in Figure 2(b), when a short-circuit fault is detected and the semiconductor switch 11 is turned off, a short-circuit current flows through the mechanical switch 21 and the MOV 12, but the back electromotive force of the MOV 12 limits the short-circuit current. The terminal voltage of the DC circuit breaker 1 is the voltage of the MOV 12, and the MOV 12 limits the short-circuit current to a current such that a voltage equivalent to the power supply voltage (Vdc) is generated in the MOV 12. This reduces the peak value of the short-circuit current even if the current-limiting reactor is small, and reduces the overcurrent withstand capability of the semiconductor switch 11 and the mechanical switch 21. In addition, by limiting the current to less than the rated current of the MOV 12 during current-limiting operation, the energy consumption of the MOV 12 during current-limiting operation can be reduced. Note that during current-limiting operation, the semiconductor switch 22 may be in the ON state or the OFF state.

[0026] As shown in Figure 2(c), after the semiconductor switch 22 is turned on, the mechanical switch 21 is turned off, causing the current flowing through the mechanical switch 21 to be commutated to the semiconductor switch 22. This enables arc-less interruption by commutating before the contact voltage of the mechanical switch 21 reaches the boiling voltage. Alternatively, even if the contact voltage of the mechanical switch 21 reaches the boiling voltage, commutation is completed in a short time, thus shortening the duration of arc discharge. In the method described in Patent Document 1, the short-circuit current continues to increase from the time of short-circuit occurrence until the mechanical switch 21 is opened. Therefore, in order to achieve arc-less commutation, it is necessary to reduce the voltage drop of the commutating semiconductor switch, i.e., the on-resistance, so that the contact voltage of the mechanical switch 21 does not reach the boiling voltage. On the other hand, in the DC circuit breaker 1 of this disclosure, the current during commutation is reduced by the current limiting mechanism 100, so even if a semiconductor switch with high on-resistance is used for the semiconductor switch 22, the contact voltage of the mechanical switch 21 can be suppressed. Therefore, the chip area of ​​the semiconductor switch 22 can be reduced, or the number of switches connected in parallel can be reduced, which leads to miniaturization of the circuit.

[0027] As shown in Figure 2(d), when the semiconductor switch 22 is turned off, the terminal voltage of the DC circuit breaker 1 becomes the sum of the breakdown voltage of the semiconductor switch 22 and the back electromotive force of the MOV 12, and the current is interrupted by the breakdown voltage of the semiconductor switch 22 and the back electromotive force of the MOV 12. Since the terminal voltage of the DC circuit breaker 1 is shared between the semiconductor switch 22 and the MOV 12, the voltage of the MOV 12 can be reduced, that is, the voltage applied to the semiconductor switch 11 connected in parallel with the MOV 12 can be reduced, and a semiconductor switch 11 with a low withstand voltage and low conduction loss can be selected.

[0028] Then, as shown in Figure 2(e), the terminal voltage of the DC circuit breaker 1 matches the voltage of the power supply, and the DC circuit breaker 1 is in the tripped state.

[0029] Thus, when a short-circuit fault is detected while the mechanical switch 21 and semiconductor switch 11 are ON, the semiconductor switch 11 is turned OFF, then the mechanical switch 21 is turned OFF while the semiconductor switch 22 is ON, and then the semiconductor switch 22 is turned OFF. By first turning off the semiconductor switch 11, the short-circuit current can be rapidly reduced by the MOV 12. Next, by turning off the mechanical switch 21 while the semiconductor switch 22 is ON, the current flowing through the mechanical switch 21 can be commutated to the semiconductor switch 22, suppressing the generation of arcs in the mechanical switch 21 and reducing the arc generation time. In other words, wear on the contacts of the mechanical switch 21 can be suppressed. Then, by turning off the semiconductor switch 22, the short-circuit current can be interrupted by the varistor voltage of the MOV 12 and the breakdown voltage of the semiconductor switch 22. Furthermore, if an MPS diode, Zener diode, or TVS diode is provided instead of MOV12, the short-circuit current can be interrupted by the breakdown voltage of the MPS diode, Zener diode, or TVS diode and the breakdown voltage of the semiconductor switch 22 when the semiconductor switch 22 is turned off.

[0030] As explained above, in the event of a short-circuit fault, the MOV 12 of the current-limiting mechanism 100 can rapidly reduce the short-circuit current immediately after the semiconductor switch 11 is turned off, thus allowing for miniaturization of the current-limiting reactor. Furthermore, since the semiconductor switch 22 is connected in series with the MOV 12, the voltage applied to the semiconductor switch 11 connected in parallel with the MOV 12 after the short-circuit current is interrupted is reduced by the breakdown voltage of the semiconductor switch 22. This means that the varistor voltage of the MOV 12 can be reduced. If a low-voltage element can be selected for the MOV 12, the limiting voltage of the MOV 12 when the current that applies the maximum voltage to the semiconductor switch 11 begins to flow is also reduced. Therefore, it becomes unnecessary to use a high-voltage-resistant switch as the semiconductor switch 11. As a result, by using a low-voltage-resistant switch, it is possible to reduce the number of switches connected in parallel to obtain the same on-resistance, or to reduce the chip area. In other words, the semiconductor switch 11 can be miniaturized. Alternatively, the on-resistance of the semiconductor switch 11 can be reduced when using the same chip area, thereby reducing the conduction loss of the semiconductor switch 11. In other words, the heat sink used to dissipate the heat generated by the conduction loss in the semiconductor switch 11 can be made smaller. Therefore, as described above, the DC circuit breaker 1 allows for miniaturization of the current limiting reactor, the semiconductor switch 11, and the heat sink for the semiconductor switch 11, thus reducing the overall circuit size.

[0031] (Embodiment 2) Next, a DC circuit breaker according to Embodiment 2 will be described.

[0032] Figure 3 is a circuit diagram showing an example of a DC circuit breaker 2 according to Embodiment 2.

[0033] The configuration of DC circuit breaker 2 differs from that of DC circuit breaker 1 according to Embodiment 1 in that it includes a tripping mechanism 201 instead of a tripping mechanism 200. Since other aspects are the same as those in Embodiment 1, the following will mainly describe the differences, and the same aspects will be omitted.

[0034] The interruption mechanism 201 further differs from the interruption mechanism 200 according to Embodiment 1 in that it has an MOV 23 connected in parallel with the mechanical switch 21 and the semiconductor switch 22. The mechanical switch 21 and the semiconductor switch 22 are the same as those in Embodiment 1, so their description is omitted. The MOV 23 is an example of a second voltage clamp circuit. The MOV 23 is an element that becomes conductive when the voltage applied to the MOV 23 is above a certain voltage, and becomes interrupted when the voltage applied to the MOV 23 is below a certain voltage.

[0035] In the following, an example in which the second voltage clamp circuit is MOV23 will be described, but the second voltage clamp circuit is not particularly limited as long as it is a circuit in which the impedance of the second voltage clamp circuit decreases when a voltage lower than the breakdown voltage of the semiconductor switch 22 is applied to the second voltage clamp circuit. For example, an MPS diode, Zener diode, or TVS diode may be provided instead of MOV23. In other words, the second voltage clamp circuit may include any clamp element from among a varistor, MPS diode, Zener diode, and TVS diode. That is, examples of circuits in which its own impedance decreases when a voltage lower than the breakdown voltage of the semiconductor switch 22 is applied include varistors, MPS diodes, Zener diodes, and TVS diodes.

[0036] In Figure 3, an example is shown in which the interruption mechanism 201 is connected to the power supply side and the current limiting mechanism 100 is connected to the load side. However, the current limiting mechanism 100 may be connected to the power supply side and the interruption mechanism 201 may be connected to the load side. Furthermore, the semiconductor switches 11 and 22 may each be bidirectional switches, and the power supply and load may be swapped in Figure 3. In this case, the power supply and load may be swapped in Figure 3, and the current limiting mechanism 100 and the interruption mechanism 201 may also be swapped.

[0037] The selection requirements for MOV12 and 23 are described below. For example, the sum of the minimum values ​​of the varistor voltage of MOV23 and the breakdown voltage of the semiconductor switch 22, and the varistor voltage of MOV12, is equal to or greater than the power supply voltage. Also, for example, at least one of the minimum values ​​of the varistor voltage of MOV23 and the breakdown voltage of the semiconductor switch 22, and the minimum value of the varistor voltage of MOV12 and the breakdown voltage of the semiconductor switch 11, is less than the power supply voltage. Note that if an MPS diode, Zener diode, or TVS diode is provided instead of MOV12, the varistor voltage of MOV12 is replaced with the breakdown voltage of the MPS diode, Zener diode, or TVS diode in the above description. Similarly, if an MPS diode, Zener diode, or TVS diode is provided instead of MOV23, the varistor voltage of MOV23 is replaced with the breakdown voltage of the MPS diode, Zener diode, or TVS diode in the above description.

[0038] By using a first voltage clamp circuit and a second voltage clamp circuit having such varistor voltages or breakdown voltages, short-circuit currents can be interrupted, and the element breakdown voltage of the semiconductor switch 11 or semiconductor switch 22 can be reduced. In other words, by using a first voltage clamp circuit and a second voltage clamp circuit such that the sum of the varistor voltage or breakdown voltage of the first voltage clamp circuit and the varistor voltage or breakdown voltage of the second voltage clamp circuit exceeds the voltage of the power supply, short-circuit currents can be interrupted.

[0039] Next, the opening operation (i.e., the tripping operation) of the DC circuit breaker 2 in the event of a short-circuit fault will be explained using Figure 4.

[0040] Figure 4 shows an example of a tripping sequence by the DC circuit breaker 2 according to Embodiment 2. Figure 4(a) shows the DC circuit breaker 2 in the closed state, Figure 4(b) shows the DC circuit breaker 2 during current limiting operation, Figure 4(c) shows the DC circuit breaker 2 during commutation operation, Figure 4(d) shows the DC circuit breaker 2 during demagnetization operation, and Figure 4(e) shows the DC circuit breaker 2 in the tripped state.

[0041] As shown in Figure 4(a), when the DC circuit breaker 2 is in the closed state, that is, when the semiconductor switch 11 and the mechanical switch 21 are in the ON state, current flows through the mechanical switch 21 and the semiconductor switch 11. Since the semiconductor switch 11 and the mechanical switch 21 are in the ON state, the terminal voltage of the DC circuit breaker 2 (specifically, the voltage between the power supply side terminal and the load side terminal of the DC circuit breaker 2) is approximately 0. Note that in the closed state, the semiconductor switch 22 may be in either the ON or OFF state.

[0042] As shown in Figure 4(b), when a short-circuit fault is detected and the semiconductor switch 11 is turned off, a short-circuit current flows through the mechanical switch 21 and the MOV 12, but the back electromotive force of the MOV 12 limits the short-circuit current. The terminal voltage of the DC circuit breaker 2 is the voltage of the MOV 12, and the MOV 12 limits the short-circuit current to a current such that a voltage equivalent to the power supply voltage (Vdc) is generated in the MOV 12. This reduces the peak value of the short-circuit current even if the current-limiting reactor is small, and reduces the overcurrent withstand capability of the semiconductor switch 11 and the mechanical switch 21. In addition, by limiting the current to approximately the rated current or less by the MOV 12 during current-limiting operation, the energy consumption of the MOV 12 during current-limiting operation can be reduced. Note that during current-limiting operation, the semiconductor switch 22 may be in the ON state or the OFF state.

[0043] As shown in Figure 4(c), when the semiconductor switch 22 is turned on, the mechanical switch 21 is turned off, causing the current flowing through the mechanical switch 21 to be commutated to the semiconductor switch 22. This allows for arc-less interruption by commutating before the contact voltage of the mechanical switch 21 reaches the boiling voltage. Alternatively, even if the contact voltage of the mechanical switch 21 reaches the boiling voltage, commutation is completed in a short time, thus reducing the duration of arc discharge.

[0044] As shown in FIG. 4(d), turning off the semiconductor switch 22 causes the inter-terminal voltage of the DC circuit breaker 2 to become the sum of the back electromotive force of the MOV 23 and the back electromotive force of the MOV 12, and the current is interrupted by the back electromotive force of the MOV 23 and the back electromotive force of the MOV 12. Since the inter-terminal voltage of the DC circuit breaker 2 is shared between the MOV 23 and the MOV 12, the voltage across the MOV 12 can be reduced. That is, the voltage applied to the semiconductor switch 11 connected in parallel with the MOV 12 can be lowered, so that a semiconductor switch 11 with low withstand voltage and low conduction loss can be selected.

[0045] Then, as shown in FIG. 4(e), the inter-terminal voltage of the DC circuit breaker 2 matches the voltage of the power supply, and the DC circuit breaker 2 enters an interrupted state.

[0046] As described above, since the MOV 23 is connected in series with the MOV 12, after the short-circuit current is interrupted, the voltage applied to the semiconductor switch 11 connected in parallel with the MOV 12 is reduced by the varistor voltage of the MOV 23. If an MPS diode, Zener diode or TVS diode is provided instead of the MOV 23, the voltage applied to the semiconductor switch 11 after the short-circuit current is interrupted is reduced by the breakdown voltage of the MPS diode, Zener diode or TVS diode. This means that the varistor voltage of the MOV 12 can be reduced. If an element with a low varistor voltage can be selected for the MOV 12, the limiting voltage of the MOV 12 when a current that applies the maximum voltage to the semiconductor switch 11 starts to flow is also reduced at the same time. Therefore, it is no longer necessary to use a switch with high withstand voltage as the semiconductor switch 11. As a result, using a low withstand voltage switch enables reduction in the number of parallel-connected switches for obtaining the same on-resistance, or reduction in chip area. That is, the semiconductor switch 11 can be reduced in size.

[0047] Next, the closing operation of the DC circuit breaker 2 at the time of starting a system equipped with the DC circuit breaker 2 will be described with reference to FIGS. 5A and 5B.

[0048] FIGS. 5A and 5B are diagrams showing an example of a closing sequence by the DC circuit breaker 2 according to the second embodiment. There are, for example, two closing sequences for the DC circuit breaker 2, and the first closing sequence will be described first with reference to FIG. 5A.

[0049] (a) of FIG. 5A shows the DC circuit breaker 2 in a cut-off state, (b) of FIG. 5A shows the DC circuit breaker 2 during an initial charging operation, and (c) of FIG. 5A shows the DC circuit breaker 2 in a closed pole state.

[0050] As shown in (a) of FIG. 5A, when the DC circuit breaker 2 is in the cut-off state, that is, when the semiconductor switches 11 and 22 and the mechanical switch 21 are in the off state, no current flows through the semiconductor switches 11 and 22 and the mechanical switch 21.

[0051] As shown in (b) of FIG. 5A, when a system equipped with the DC circuit breaker 2 is started, an initial charging operation for gradually charging the capacitance of a load is performed to suppress an inrush current. In the initial charging operation, for example, the semiconductor switch 11 is turned on. The voltage across the terminals of the DC circuit breaker 2 at this time is the voltage of the MOV 23. This allows the voltage applied to the load to be increased stepwise, and allows the capacitance of the load to be gradually charged via the MOV 23.

[0052] As shown in (c) of FIG. 5A, the mechanical switch 21 is turned on, the DC circuit breaker 2 enters the closed pole state, and the normal operation of the system equipped with the DC circuit breaker 2 is started. In the closed pole state, the semiconductor switch 22 may be either in an on state or an off state.

[0053] As described above, when the application of voltage from a power supply to a load is started in a state where the mechanical switch 21 and the semiconductor switches 11 and 22 are off, the semiconductor switch 11 may be turned on, and then the mechanical switch 21 may be turned on. By turning on the semiconductor switch 11 first, a voltage can be applied to the load via the MOV 23, so that the current flowing into the capacitance of the load can be reduced.

[0054] Next, the second closing sequence will be described with reference to FIG. 5B.

[0055] Figure 5B(a) shows the DC circuit breaker 2 in the off state, Figure 5B(b) shows the DC circuit breaker 2 during the initial charging operation, and Figure 5B(c) shows the DC circuit breaker 2 in the closed state.

[0056] As shown in Figure 5B(a), when the DC circuit breaker 2 is in the tripped state, that is, when the semiconductor switches 11 and 22 and the mechanical switch 21 are in the off state, no current flows through the semiconductor switches 11 and 22 and the mechanical switch 21.

[0057] As shown in Figure 5B(b), when a system equipped with a DC circuit breaker 2 is started, an initial charging operation is performed to gradually charge the load capacity in order to suppress inrush current. In the initial charging operation, for example, a mechanical switch 21 is turned on. Alternatively, a semiconductor switch 22 may be turned on instead of the mechanical switch 21. When the mechanical switch 21 or the semiconductor switch 22 is turned on, the terminal voltage of the DC circuit breaker 2 is the voltage of MOV 12. This allows the voltage applied to the load to be increased in stages, and the load capacity can be gradually charged via MOV 12.

[0058] As shown in Figure 5B(c), the semiconductor switch 11 is turned on, the DC circuit breaker 2 is closed, and the normal operation of the system equipped with the DC circuit breaker 2 begins. If the mechanical switch 21 is not turned on during the initial charging operation, the mechanical switch 21 will be turned on in the closed state. Also, in the closed state, the semiconductor switch 22 may be in the on state or the off state. For example, if the semiconductor switch 22 was turned on during the initial charging operation, the semiconductor switch 22 may remain on or off in the closed state.

[0059] Thus, when voltage is applied from the power supply to the load while the mechanical switch 21 and semiconductor switches 11 and 22 are in the off state, at least one of the mechanical switch 21 and semiconductor switch 22 may turn on, and then the semiconductor switch 11 and mechanical switch 21 may turn on. By first turning on the mechanical switch 21 or the semiconductor switch 22, voltage can be applied to the load via MOV 12, thereby reducing the current flowing to the load capacity.

[0060] As explained above, when voltage is applied from the power supply to the load, the voltage may be applied to the load via MOV 12 or 23. Applying voltage to the load via MOV 12 or 23 reduces the current flowing to the load's capacity. In other words, it reduces the inrush current that occurs when voltage is applied from the power supply to the load. As a result, the current withstand capability of the mechanical switch 21 and the semiconductor switch 11 can be reduced, and the mechanical switch 21 and the semiconductor switch 11 can be miniaturized.

[0061] (Embodiment 3) Next, a DC circuit breaker according to Embodiment 3 will be described.

[0062] Figure 6 is a circuit diagram showing an example of a DC circuit breaker 3 according to Embodiment 3.

[0063] The configuration of DC circuit breaker 3 differs from that of DC circuit breaker 2 according to Embodiment 2 in that it includes a tripping mechanism 202 instead of a tripping mechanism 201. Since other aspects are the same as those in Embodiment 2, the following will mainly describe the differences, and the same aspects will be omitted.

[0064] The interruption mechanism 202 further differs from the interruption mechanism 201 according to Embodiment 2 in that it has a resistor 24 connected in series with the MOV 23. The resistor 24 is an example of a first resistor. The mechanical switch 21, semiconductor switch 22, and MOV 23 are the same as those in Embodiment 2, so their description is omitted.

[0065] In Figure 6, an example is shown in which the interruption mechanism 202 is connected to the power supply side and the current limiting mechanism 100 is connected to the load side. However, the current limiting mechanism 100 may be connected to the power supply side and the interruption mechanism 202 may be connected to the load side. Furthermore, the semiconductor switches 11 and 22 may each be bidirectional switches, and the power supply and load may be swapped in Figure 6. In this case, the power supply and load may be swapped in Figure 6, and the current limiting mechanism 100 and the interruption mechanism 202 may also be swapped.

[0066] Regarding the opening operation (i.e., tripping operation) of the DC circuit breaker 3 in the event of a short-circuit fault, since a resistor 24 is provided, the semiconductor switch 22 is turned off during the demagnetization operation in Figure 4(d). As a result, the terminal voltage of the DC circuit breaker 3 becomes the sum of the back electromotive force of MOV 23, the back electromotive force of MOV 12, and the voltage across the resistor 24. The difference is that the current is interrupted by the back electromotive force of MOV 23, the back electromotive force of MOV 12, and the voltage across the resistor 24. Other points are basically the same as the opening operation of the DC circuit breaker 2 according to Embodiment 2, so an explanation is omitted.

[0067] Furthermore, regarding the closing operation of the DC circuit breaker 3 when the system equipped with the DC circuit breaker 3 is started, it differs from that in Embodiment 2 in that when the application of voltage from the power supply to the load begins, the semiconductor switch 11 is turned on and voltage is applied to the load via the MOV 23 and resistor 24, and then the mechanical switch 21 is turned on. Specifically, in the initial charging operation in Figure 5A(b), when the semiconductor switch 11 is turned on, the terminal voltage of the DC circuit breaker 3 is the sum of the voltage of MOV 23 and the voltage generated across resistor 24. Other points are basically the same as the closing operation of the DC circuit breaker 2 in Embodiment 2, so an explanation is omitted.

[0068] In addition to the MOV 23, applying voltage to the load via the resistor 24 further reduces the current flowing through the load's capacity. In other words, it further reduces the inrush current that occurs when voltage is first applied from the power supply to the load. Furthermore, the interruption mechanism 202 and the current limiting mechanism 100, which are used to interrupt short-circuit current, can be repurposed as circuits to reduce inrush current.

[0069] (Modification 1 of Embodiment 3) Next, a DC circuit breaker according to Modification 1 of Embodiment 3 will be described.

[0070] Figure 7 is a circuit diagram showing an example of a DC circuit breaker 3a according to a modified example 1 of Embodiment 3.

[0071] The configuration of the DC circuit breaker 3a differs from that of the DC circuit breaker 3 in Embodiment 3 in that it has a tripping mechanism 202a instead of a tripping mechanism 202. Since other aspects are the same as in Embodiment 3, the following will mainly describe the differences, and the same aspects will be omitted.

[0072] The interruption mechanism 202a differs from the interruption mechanism 202 according to Embodiment 3 in that it further includes a semiconductor switch 25 connected in parallel with the MOV 23 and a resistor 26 connected in series with the semiconductor switch 25. Specifically, the semiconductor switch 25 and resistor 26, which are connected in series with the MOV 23 and resistor 24, are connected in parallel. The mechanical switch 21, semiconductor switch 22, MOV 23, and resistor 24 are the same as those in Embodiment 3, so their description is omitted. The semiconductor switch 25 is an example of a third self-extinguishing switch. The resistor 26 is an example of a second resistor. The semiconductor switch 25 is, for example, an IGBT, but may also be an FET or a bipolar transistor.

[0073] In Figure 7, an example is shown in which the interruption mechanism 202a is connected to the power supply side and the current limiting mechanism 100 is connected to the load side. However, the current limiting mechanism 100 may be connected to the power supply side and the interruption mechanism 202a may be connected to the load side. Furthermore, the semiconductor switches 11 and 22 may each be bidirectional switches, and the power supply and load may be swapped in Figure 7. In this case, the power supply and load may be swapped in Figure 7, and the current limiting mechanism 100 and the interruption mechanism 202a may also be swapped.

[0074] The opening operation (i.e., tripping operation) of the DC circuit breaker 3a in the event of a short-circuit fault is basically the same as the opening operation of the DC circuit breaker 3 according to Embodiment 3, so no explanation will be given. Note that the semiconductor switch 25 is in the off state during the opening operation.

[0075] Furthermore, regarding the closing operation of the DC circuit breaker 3a when a system equipped with the DC circuit breaker 3a is started, it differs from that in Embodiment 3 in that when the application of voltage from the power supply to the load begins, the semiconductor switch 11 turns on and voltage is applied to the load via the MOV 23 and resistor 24, then the semiconductor switch 25 turns on and voltage is applied to the load via resistor 26, and then the mechanical switch 21 turns on. Specifically, in the initial charging operation in Figure 5A(b), when the semiconductor switch 11 is turned on, the terminal voltage of the DC circuit breaker 3a is the sum of the voltage of the MOV 23 and the voltage generated across the resistor 24. Subsequently, when the semiconductor switch 25 is turned on, the terminal voltage of the DC circuit breaker 3a is the voltage generated across the resistor 26. Other points are basically the same as the closing operation of the DC circuit breaker 3 in Embodiment 3, so an explanation is omitted.

[0076] If the semiconductor switch 25 and resistor 26 are not provided, when the semiconductor switch 11 is turned on, the voltage applied to the load changes from a state where voltage is applied via the MOV 23 and resistor 24 to a state where voltage is applied to the load without going through the MOV 23 and resistor 24. In other words, at this time, there is a risk that the current flowing to the load capacity will increase rapidly. Therefore, by turning on the semiconductor switch 25, the state in which voltage is applied to the load can be changed from a state where voltage is applied via the MOV 23 and resistor 24 to a state where voltage is applied via resistor 26. In other words, the rapid increase in current flowing to the load capacity can be suppressed. In addition, by providing resistors 24 and 26, the short-time ratings of each resistor can be used.

[0077] (Modification 2 of Embodiment 3) Next, a DC circuit breaker according to Modification 2 of Embodiment 3 will be described.

[0078] Figure 8 is a circuit diagram showing an example of a DC circuit breaker 3b according to a modified example 2 of Embodiment 3.

[0079] The configuration of the DC circuit breaker 3b differs from that of the DC circuit breaker 3 in Embodiment 3 in that it is equipped with a tripping mechanism 202b instead of a tripping mechanism 202. Since other aspects are the same as those in Embodiment 3, the following will mainly describe the differences, and the same aspects will be omitted.

[0080] The interruption mechanism 202b differs from the interruption mechanism 202 according to Embodiment 3 in that it further has a semiconductor switch 25 connected in parallel with the MOV 23. The mechanical switch 21, semiconductor switch 22, MOV 23, and resistor 24 are the same as those in Embodiment 3, so their description is omitted. The semiconductor switch 25 is an example of a third self-extinguishing switch. The semiconductor switch 25 is, for example, an IGBT, but may also be an FET or a bipolar transistor.

[0081] In Figure 8, an example is shown in which the interruption mechanism 202b is connected to the power supply side and the current limiting mechanism 100 is connected to the load side. However, the current limiting mechanism 100 may be connected to the power supply side and the interruption mechanism 202b may be connected to the load side. Furthermore, the semiconductor switches 11 and 22 may each be bidirectional switches, and the power supply and load may be swapped in Figure 8. In this case, the power supply and load may be swapped in Figure 8, and the current limiting mechanism 100 and the interruption mechanism 202b may also be swapped.

[0082] The opening operation (i.e., tripping operation) of the DC circuit breaker 3b in the event of a short-circuit fault is basically the same as the opening operation of the DC circuit breaker 3 according to Embodiment 3, so no explanation is provided. Note that the semiconductor switch 25 is in the off state during the opening operation.

[0083] Furthermore, regarding the closing operation of the DC circuit breaker 3b when the system equipped with the DC circuit breaker 3b is started, it differs from that in Embodiment 3 in that when the application of voltage from the power supply to the load begins, the semiconductor switch 11 turns on and voltage is applied to the load via the MOV 23 and resistor 24, then the semiconductor switch 25 turns on and voltage is applied to the load via resistor 24, and then the mechanical switch 21 turns on. Specifically, in the initial charging operation in Figure 5A(b), when the semiconductor switch 11 is turned on, the terminal voltage of the DC circuit breaker 3b is the sum of the voltage of the MOV 23 and the voltage generated across the resistor 24. Subsequently, when the semiconductor switch 25 is turned on, the terminal voltage of the DC circuit breaker 3b is the voltage generated across the resistor 24. Other points are basically the same as the closing operation of the DC circuit breaker 3 in Embodiment 3, so an explanation is omitted.

[0084] If the semiconductor switch 25 is not provided, when the semiconductor switch 11 is turned on, the state in which voltage is applied to the load via the MOV 23 and resistor 24 changes to a state in which voltage is applied to the load without going through the MOV 23 and resistor 24. In other words, at this time, there is a risk that the current flowing to the load capacity will increase rapidly. Therefore, by turning on the semiconductor switch 25, the state in which voltage is applied to the load via the resistor 24 can be restored. In other words, the rapid increase in current flowing to the load capacity can be suppressed.

[0085] (Embodiment 4) Next, a DC circuit breaker according to Embodiment 4 will be described.

[0086] Figure 9 is a circuit diagram showing an example of a DC circuit breaker 4 according to Embodiment 4.

[0087] The configuration of the DC circuit breaker 4 differs from that of the DC circuit breaker 2 according to Embodiment 2 in that it is equipped with a current-limiting mechanism 101 instead of a current-limiting mechanism 100. Since other aspects are the same as those in Embodiment 2, the following will mainly describe the differences, and the same aspects will be omitted from the explanation.

[0088] The current-limiting mechanism 101 differs from the current-limiting mechanism 100 in Embodiment 2 in that it further has a resistor 13 connected in series with the MOV 12. The semiconductor switch 11 and MOV 12 are the same as those in Embodiment 2, so their description is omitted.

[0089] In Figure 9, an example is shown in which the cutoff mechanism 201 is connected to the power supply side and the current limiting mechanism 101 is connected to the load side. However, the current limiting mechanism 101 may be connected to the power supply side and the cutoff mechanism 201 may be connected to the load side. Furthermore, the semiconductor switches 11 and 22 may each be bidirectional switches, and the power supply and load may be swapped in Figure 9. In this case, the power supply and load may be swapped in Figure 9, and the current limiting mechanism 101 and the cutoff mechanism 201 may also be swapped.

[0090] Regarding the opening operation (i.e., tripping operation) of the DC circuit breaker 4 in the event of a short-circuit fault, since a resistor 13 is provided, the semiconductor switch 22 is turned off during the demagnetization operation in Figure 4(d). As a result, the terminal voltage of the DC circuit breaker 4 becomes the sum of the back electromotive force of MOV 23, the back electromotive force of MOV 12, and the voltage across resistor 13. The difference is that the current is interrupted by the back electromotive force of MOV 23, the back electromotive force of MOV 12, and the voltage across resistor 13. Other points are basically the same as the opening operation of the DC circuit breaker 2 according to Embodiment 2, so an explanation is omitted.

[0091] Furthermore, regarding the closing operation of the DC circuit breaker 4 when the system equipped with the DC circuit breaker 4 is started, it differs from that in Embodiment 2 in that when the application of voltage from the power supply to the load begins, at least one of the mechanical switch 21 and the semiconductor switch 22 is turned on, and voltage is applied to the load via the MOV 12 and the resistor 13, and then the semiconductor switch 11 is turned on (if the mechanical switch 21 is not turned on, the mechanical switch 21 is also turned on). Specifically, in the initial charging operation in Figure 5B(b), when at least one of the mechanical switch 21 and the semiconductor switch 22 is turned on, the terminal voltage of the DC circuit breaker 4 is the sum of the voltage of the MOV 12 and the voltage generated across the resistor 13. Other points are basically the same as the closing operation of the DC circuit breaker 2 according to Embodiment 2, so an explanation is omitted.

[0092] In addition to the MOV 12, applying voltage to the load via the resistor 13 further suppresses the current flowing through the load's capacitance. In other words, it further suppresses the inrush current that occurs when voltage is first applied from the power supply to the load. Furthermore, the interruption mechanism 201 and current limiting mechanism 101, which are used to interrupt short-circuit current, can be repurposed as circuits to suppress inrush current.

[0093] (Modification of Embodiment 4) Next, a DC circuit breaker according to a modification of Embodiment 4 will be described.

[0094] Figure 10 is a circuit diagram showing an example of a DC circuit breaker 4a according to a modified example of Embodiment 4.

[0095] The configuration of the DC circuit breaker 4a differs from that of the DC circuit breaker 4 in Embodiment 4 in that it is equipped with a current-limiting mechanism 101a instead of a current-limiting mechanism 101. Since other aspects are the same as those in Embodiment 4, the following will mainly describe the differences, and the same aspects will be omitted.

[0096] The current-limiting mechanism 101a differs from the current-limiting mechanism 101 according to Embodiment 4 in that it further includes a semiconductor switch 14 connected in parallel with the MOV 12. The semiconductor switch 11, MOV 12, and resistor 13 are the same as those in Embodiment 4, so their description is omitted. The semiconductor switch 14 is an example of a third self-extinguishing switch. The semiconductor switch 14 is, for example, an IGBT, but it may also be an FET or a bipolar transistor.

[0097] In Figure 10, an example is shown in which the interruption mechanism 201 is connected to the power supply side and the current limiting mechanism 101a is connected to the load side. However, the current limiting mechanism 101a may be connected to the power supply side and the interruption mechanism 201 may be connected to the load side. Furthermore, the semiconductor switches 11 and 22 may each be bidirectional switches, and the power supply and load may be swapped in Figure 10. In this case, the power supply and load may be swapped in Figure 10, and the current limiting mechanism 101a and the interruption mechanism 201 may also be swapped.

[0098] The opening operation (i.e., tripping operation) of the DC circuit breaker 4a in the event of a short-circuit fault is basically the same as the opening operation of the DC circuit breaker 4 according to Embodiment 4, so no explanation will be given. Note that the semiconductor switch 14 is in the off state during the opening operation.

[0099] Furthermore, regarding the closing operation of the DC circuit breaker 4a when a system equipped with the DC circuit breaker 4a is started, it differs from that in Embodiment 4 in that when the application of voltage from the power supply to the load begins, at least one of the mechanical switch 21 and the semiconductor switch 22 is turned on and voltage is applied to the load via the MOV 12 and the resistor 13, then the semiconductor switch 14 is turned on and voltage is applied to the load via the resistor 13, and then the semiconductor switch 11 is turned on (if the mechanical switch 21 is not turned on, the mechanical switch 21 is also turned on). Specifically, in the initial charging operation in Figure 5B(b), when at least one of the mechanical switch 21 and the semiconductor switch 22 is turned on, the terminal voltage of the DC circuit breaker 4a is the sum of the voltage of the MOV 12 and the voltage generated across the resistor 13. Subsequently, when the semiconductor switch 14 is turned on, the terminal voltage of the DC circuit breaker 4a is the voltage generated across the resistor 13. Other points are basically the same as the closing operation of the DC circuit breaker 4 in Embodiment 4, so the explanation is omitted.

[0100] If the semiconductor switch 14 is not provided, when at least one of the mechanical switch 21 and the semiconductor switch 22 is turned on, the state in which voltage is applied to the load via the MOV 12 and resistor 13 changes to a state in which voltage is applied to the load without going through the MOV 12 and resistor 13. In other words, at this time, there is a risk that the current flowing to the load capacity will increase rapidly. Therefore, by turning on the semiconductor switch 14, the state in which voltage is applied to the load via the resistor 13 can be changed from the state in which voltage is applied to the load via the MOV 12 and resistor 13. In other words, it is possible to suppress the rapid increase in the current flowing to the load capacity.

[0101] In addition, similar to the modification 1 of Embodiment 3, a second resistor may be connected in series with the MOV 12, and the MOV 12 and the second resistor, which are connected in series with the semiconductor switch 14 and resistor 13 connected in series, may be connected in parallel.

[0102] (Other Embodiments) Embodiments have been described above as examples of the technology relating to this disclosure. However, the technology relating to this disclosure is not limited thereto and can be applied to embodiments that are modified, replaced, added to, or omitted as appropriate. For example, the following modified examples are also included in one embodiment of this disclosure.

[0103] For example, a bootstrap circuit may be applied to the DC circuit breaker according to each of the above embodiments. This will be explained with reference to Figures 11 and 12.

[0104] Figure 11 is a circuit diagram showing an example of a bootstrap circuit applied to a DC circuit breaker according to each embodiment (except for the modified examples 1 and 2 of Embodiment 3). Figure 11 shows an example of a bootstrap circuit in which a tripping mechanism is provided on the power supply side and a current limiting mechanism is provided on the load side.

[0105] For example, the bootstrap circuit includes gate drivers (GDs) 31 and 32, a power supply 33, a diode 34, and a capacitor 35.

[0106] GD31 is connected to the gate of semiconductor switch 11 and drives semiconductor switch 11. GD32 is connected to the gate of semiconductor switch 22 and drives semiconductor switch 22.

[0107] In a half-bridge configuration circuit such as semiconductor switches 11 and 22, a bootstrap circuit as shown in Figure 11 may be used to ensure the drive voltage to the GD32 of the high-side semiconductor switch 22. Capacitor 35 is a bootstrap capacitor for supplying the drive voltage to the semiconductor switch 22.

[0108] Capacitor 35 has one end connected to the node between the collector of semiconductor switch 11 and the emitter of semiconductor switch 22, and the other end connected to the power supply terminal of GD32 and the cathode of diode 34. Diode 34 has its anode connected to power supply 33, and its cathode connected to the power supply terminal of GD32 and capacitor 35. The drive voltage of GD31 is supplied from power supply 33.

[0109] Since capacitor 35 is connected to the power terminal of GD32, the charging voltage of capacitor 35 becomes the driving voltage of GD32, that is, the voltage for controlling the semiconductor switch 22. Capacitor 35 is charged when semiconductor switch 11 is in the ON state.

[0110] The drive voltage of the GD32 of the high-side semiconductor switch 22 can be secured by a bootstrap circuit with a simple circuit configuration consisting of a diode 34 and a capacitor 35, thus reducing cost and size.

[0111] Furthermore, if a current-limiting mechanism is provided on the power supply side and a cutoff mechanism is provided on the load side, the semiconductor switches 11 and 22 shown in Figure 11 are swapped. That is, the gate of semiconductor switch 22 is connected to GD31, and the gate of semiconductor switch 11 is connected to GD32. Even in this case, the drive voltage of GD32 of the high-side semiconductor switch 11 can be secured by a bootstrap circuit with a simple circuit configuration consisting of a diode 34 and a capacitor 35, thus reducing cost and size.

[0112] Figure 12 is a circuit diagram showing an example of a bootstrap circuit applied to DC circuit breakers 3a and 3b according to modified examples 1 and 2 of Embodiment 3. Figure 12 shows an example of a bootstrap circuit in which a tripping mechanism is provided on the power supply side and a current limiting mechanism is provided on the load side.

[0113] For example, the bootstrap circuit includes GD31, 32, and 36, a power supply 33, a diode 34, and a capacitor 35.

[0114] GD31 is connected to the gate of semiconductor switch 11 and drives semiconductor switch 11. GD32 is connected to the gate of semiconductor switch 22 and drives semiconductor switch 22. GD36 is connected to the gate of semiconductor switch 25 and drives semiconductor switch 25.

[0115] A bootstrap circuit, as shown in Figure 12, may be used to ensure the drive voltage to GD32 of the high-side semiconductor switch 22 and GD36 of the high-side semiconductor switch 25. Capacitor 35 is a bootstrap capacitor for supplying the drive voltage to semiconductor switches 22 and 25.

[0116] Capacitor 35 has one end connected to the node between the collector of semiconductor switch 11 and the emitter of semiconductor switch 22, and the node between the collector of semiconductor switch 11 and the emitter of semiconductor switch 25, and the other end connected to the power supply terminals of GD32 and 36 and the cathode of diode 34. Diode 34 has its anode connected to power supply 33 and its cathode connected to the power supply terminal of GD32 and capacitor 35. The drive voltage of GD31 is supplied from power supply 33.

[0117] Since capacitor 35 is connected to the power terminals of GD32 and 36, the charging voltage of capacitor 35 becomes the driving voltage of GD32 and 36, that is, the voltage for controlling semiconductor switches 22 and 25. Capacitor 35 is charged when semiconductor switch 11 is in the ON state.

[0118] The drive voltages for the GD32 and 36 of the high-side semiconductor switches 22 and 25 can be secured by a bootstrap circuit with a simple circuit configuration consisting of a diode 34 and a capacitor 35, thereby reducing cost and size.

[0119] Furthermore, if a current-limiting mechanism is provided on the power supply side and a cutoff mechanism is provided on the load side, the semiconductor switches 11 and 22 shown in Figure 12 are swapped. That is, the gate of semiconductor switch 22 is connected to GD31, and the gate of semiconductor switch 11 is connected to GD32. Also, semiconductor switches 25 and GD36 shown in Figure 12 are connected to the low side. Even in this case, the drive voltage of GD32 of the high-side semiconductor switch 11 can be secured by a bootstrap circuit with a simple circuit configuration consisting of a diode 34 and a capacitor 35, thus reducing cost and size.

[0120] For example, in the above embodiment, an example was described in which the DC circuit breaker is installed between the positive terminals of the power supply and the load, but the DC circuit breaker may also be installed between the negative terminals of the power supply and the load. In other words, the DC circuit breaker is connected between either the positive terminals or the negative terminals of the power supply and the load.

[0121] Furthermore, another mechanical switch may be connected between the positive terminal and the negative terminal of the power supply and the load. This will be explained using Figure 13.

[0122] Figure 13 shows an example of connecting other mechanical switches. In Figure 13, an example is shown in which a DC circuit breaker 2 is provided between the positive terminals and another mechanical switch 300 is provided between the negative terminals. This allows for interruption of both the positive and negative terminals. Alternatively, for example, the DC circuit breaker 2 may interrupt one terminal (the positive terminals in Figure 13) before the other mechanical switch 300. By operating the DC circuit breaker 2 before the other mechanical switch 300, the other mechanical switch 300 can be turned off while no current is flowing through it, thereby suppressing the generation of arcs in the other mechanical switch 300. As an interruption method, the timing may be changed by delaying the signal to the mechanical switch 300 itself. Alternatively, the delay may be achieved by reducing the voltage applied to the coil when demagnetizing the coil for driving the mechanical contacts. This can be achieved by using a freewheeling diode in the demagnetization circuit.

[0123] Furthermore, when supplying power to the high-side semiconductor switch using a bootstrap circuit, the bootstrap capacitor can be charged before the mechanical switch 300, located between the negative terminals, closes when the switch is turned on. This allows the high-side semiconductor switch to be driven immediately after the closing is complete, enabling immediate shutdown after the closing is complete.

[0124] For example, in the above embodiment, the description of the control circuit, such as a microcontroller, that controls each switch (semiconductor switch and mechanical switch) in the DC circuit breaker was omitted, but the DC circuit breaker may be equipped with such a control circuit.

[0125] For example, in Embodiment 2, if a short-circuit fault is detected while the mechanical switch 21 and semiconductor switch 11 are ON, the control circuit may turn off the semiconductor switch 11, then turn off the mechanical switch 21 while the semiconductor switch 22 is ON, and then turn off the semiconductor switch 22. Also, if the application of voltage from the power supply to the load is started while the mechanical switch 21, semiconductor switches 11 and 22 are OFF, the control circuit may turn on the semiconductor switch 11, and then turn on the mechanical switch 21. Alternatively, if the application of voltage from the power supply to the load is started while the mechanical switch 21, semiconductor switches 11 and 22 are OFF, the control circuit may turn on at least one of the mechanical switch 21 and semiconductor switch 22, and then turn on the semiconductor switch 11 and the mechanical switch 21.

[0126] For example, in the modified examples 1 and 2 of Embodiment 3, when the application of voltage from the power supply to the load is initiated, the control circuit may turn on the semiconductor switch 11 to apply voltage to the load via the MOV 23 and resistor 24, then turn on the semiconductor switch 25 to apply voltage to the load via resistor 24, and then turn on the mechanical switch 21.

[0127] For example, in a modified version of Embodiment 4, when the application of voltage from the power supply to the load is initiated, the control circuit may turn on the mechanical switch 21 to apply voltage to the load via the MOV 12 and resistor 13, then turn on the semiconductor switch 14 to apply voltage to the load via resistor 13, and then turn on the semiconductor switch 11.

[0128] For example, if this disclosure is implemented in a program (software), each step is executed by the program using hardware resources such as the computer's CPU, memory, and input / output circuits. In other words, each step is executed by the CPU obtaining data from memory or input / output circuits, performing calculations, and outputting the calculation results to memory or input / output circuits.

[0129] In the above embodiment, each component included in the DC circuit breaker may be implemented by dedicated hardware or by executing a software program suitable for each component. Each component may also be implemented by a program execution unit such as a CPU or processor reading and executing a software program recorded on a recording medium such as a hard disk or semiconductor memory.

[0130] Some or all of the functions of the DC circuit breaker according to the above embodiment are typically implemented as an LSI, which is an integrated circuit. These may be individually integrated on a single chip, or some or all of them may be integrated on a single chip. Furthermore, the integration is not limited to an LSI, but may also be implemented with dedicated circuits or general-purpose processors. An FPGA (Field Programmable Gate Array) that can be programmed after LSI manufacturing, or a reconfigurable processor that can reconfigure the connections and settings of circuit cells inside the LSI may also be used.

[0131] Furthermore, if advances in semiconductor technology or other derived technologies lead to the emergence of integrated circuit technologies that can replace LSIs, then naturally, those technologies may be used to integrate each component included in the DC circuit breaker into an integrated circuit.

[0132] Furthermore, this disclosure also includes forms obtained by applying various modifications to the embodiments that a person skilled in the art could conceive, and forms realized by arbitrarily combining the components and functions of each embodiment without departing from the spirit of this disclosure.

[0133] (Note) The above description of embodiments discloses the following technology.

[0134] (Technical 1) A DC circuit breaker connected between a power source and a load, comprising: a current-limiting mechanism having a first self-extinguishing switch and a first voltage clamp circuit connected in parallel; and a tripping mechanism having a mechanical switch and a second self-extinguishing switch connected in parallel, wherein the current-limiting mechanism and the tripping mechanism are connected in series, and the impedance of the first voltage clamp circuit decreases when a voltage lower than the breakdown voltage of the first self-extinguishing switch is applied to the first voltage clamp circuit.

[0135] According to this, in the event of a short-circuit fault, the short-circuit current can be rapidly reduced by the first voltage clamp circuit of the current-limiting mechanism immediately after the first self-extinguishing switch is turned off, thus allowing for miniaturization of the current-limiting reactor. Furthermore, since the second self-extinguishing switch is connected in series with the first voltage clamp circuit, after the short-circuit current is interrupted, the voltage applied to the first self-extinguishing switch, which is connected in parallel with the first voltage clamp circuit, is reduced by the breakdown voltage of the second self-extinguishing switch. This means that the varistor voltage of the first voltage clamp circuit can be reduced. If an element with a low varistor voltage can be selected for the first voltage clamp circuit, the limiting voltage of the first voltage clamp circuit when the current that applies the maximum voltage to the first self-extinguishing switch begins to flow is also reduced simultaneously. Therefore, it becomes unnecessary to use a switch with a high voltage rating as the first self-extinguishing switch. As a result, by using a low-voltage switch, it is possible to reduce the number of switches connected in parallel to obtain the same on-resistance, or to reduce the chip area. In other words, the first self-extinguishing switch can be miniaturized. Alternatively, the on-resistance of the first self-extinguishing switch can be reduced when using the same chip area, thereby reducing the conduction loss of the first self-extinguishing switch. In other words, the heat sink used to dissipate the heat generated by the conduction loss in the first self-extinguishing switch can be reduced.

[0136] For example, in a mechanical DC circuit breaker, the opening delay is large, which necessitates increasing the size of the current-limiting reactor, LC resonant circuit, and MOV, resulting in a larger circuit size. Similarly, in a semiconductor DC circuit breaker, the heat sink required to dissipate the heat generated by the conduction losses of the semiconductor switch is also large, resulting in a larger circuit size. Furthermore, in a hybrid system combining mechanical and semiconductor methods, the current-limiting reactor and MOV must be large, resulting in a larger circuit size. In contrast, according to the DC circuit breaker of this disclosure, as described above, the current-limiting reactor, the first self-extinguishing switch, and the heat sink for the first self-extinguishing switch can be miniaturized, thus reducing the circuit size.

[0137] (Technical 2) The DC circuit breaker according to Technical 1, wherein the first voltage clamp circuit includes a clamping element selected from a varistor, an MPS diode, a Zener diode, and a TVS diode.

[0138] In this way, short-circuit current can be rapidly reduced using a varistor, MPS diode, Zener diode, or TVS diode.

[0139] (Technology 3) The DC circuit breaker according to Technology 1 or 2, wherein the interruption mechanism further comprises a second voltage clamp circuit connected in parallel with the mechanical switch and the second self-extinguishing switch, and the impedance of the second voltage clamp circuit decreases when a voltage lower than the breakdown voltage of the second self-extinguishing switch is applied to the second voltage clamp circuit.

[0140] According to this, since the second voltage clamp circuit is connected in series with the first voltage clamp circuit, after the short-circuit current is interrupted, the voltage applied to the first self-extinguishing switch connected in parallel with the first voltage clamp circuit will be reduced by the varistor voltage or breakdown voltage of the second voltage clamp circuit. This means that the varistor voltage of the first voltage clamp circuit can be reduced, for example. If an element with a low varistor voltage can be selected for the first voltage clamp circuit, the limiting voltage of the first voltage clamp circuit when the current that applies the maximum voltage to the first self-extinguishing switch begins to flow will also be reduced. Therefore, it becomes unnecessary to use a switch with a high voltage rating as the first self-extinguishing switch. As a result, by using a low-voltage switch, it is possible to reduce the number of switches connected in parallel to obtain the same on-resistance, or to reduce the chip area. In other words, the first self-extinguishing switch can be miniaturized. Alternatively, the on-resistance of the first self-extinguishing switch can be reduced when using the same chip area, and the conduction loss of the first self-extinguishing switch can be reduced. In other words, the heat sink used to dissipate the heat generated by the conduction loss in the first self-extinguishing switch can be reduced.

[0141] (Technical 4) The DC circuit breaker according to Technical 3, wherein the second voltage clamp circuit includes a clamping element selected from a varistor, an MPS diode, a Zener diode, and a TVS diode.

[0142] In this way, the varistor voltage or breakdown voltage of the varistor, MPS diode, Zener diode, or TVS diode can reduce the voltage applied to the first self-extinguishing switch after the short-circuit current is interrupted.

[0143] (Technical 5) The DC circuit breaker according to Technical 3 or 4, wherein the sum of the minimum value of the varistor voltage or breakdown voltage of the second voltage clamp circuit and the breakdown voltage of the second self-extinguishing switch and the varistor voltage or breakdown voltage of the first voltage clamp circuit is greater than or equal to the voltage of the power supply, and at least one of the minimum value of the varistor voltage or breakdown voltage of the second voltage clamp circuit and the breakdown voltage of the second self-extinguishing switch and the varistor voltage or breakdown voltage of the first voltage clamp circuit and the breakdown voltage of the first self-extinguishing switch is less than the voltage of the power supply.

[0144] By using a first voltage clamp circuit and a second voltage clamp circuit having such a varistor voltage or breakdown voltage, the short-circuit current can be interrupted, and the element breakdown voltage of the first self-extinguishing switch or the second self-extinguishing switch can be reduced.

[0145] (Technical 6) A DC circuit breaker according to any one of Technical 1 to 5, wherein when a short-circuit fault is detected while the mechanical switch and the first self-extinguishing switch are in the ON state, the first self-extinguishing switch is turned OFF, then the mechanical switch is turned OFF while the second self-extinguishing switch is in the ON state, and then the second self-extinguishing switch is turned OFF.

[0146] According to this, first, by turning off the first self-extinguishing switch, the short-circuit current can be rapidly reduced by the first voltage clamp circuit. Next, by turning off the mechanical switch while the second self-extinguishing switch is ON, the current flowing through the mechanical switch can be commutated to the second self-extinguishing switch, thereby suppressing the generation of arcs in the mechanical switch. In other words, wear on the contacts of the mechanical switch can be suppressed. Then, by turning off the second self-extinguishing switch, the short-circuit current can be interrupted by the varistor voltage or breakdown voltage of the first voltage clamp circuit and the breakdown voltage of the second self-extinguishing switch or the varistor voltage or breakdown voltage of the second voltage clamp circuit.

[0147] (Technical 7) A DC circuit breaker according to any one of Technical 3 to 5, wherein when the application of voltage from the power source to the load is initiated, the voltage is applied to the load via the first voltage clamp circuit or the second voltage clamp circuit.

[0148] According to this, applying voltage to the load via the first or second voltage clamp circuit reduces the current flowing through the load's capacity. In other words, it reduces the inrush current that occurs when voltage is first applied from the power source to the load. As a result, the current withstand capability of the mechanical switch and the first self-extinguishing switch can be reduced, and the mechanical switch and the first self-extinguishing switch can be miniaturized. Furthermore, the interruption mechanism and current-limiting mechanism for interrupting short-circuit current can be repurposed as circuits for reducing inrush current.

[0149] (Technical 8) The DC circuit breaker according to Technical 7, wherein when the application of voltage from the power source to the load is started while the mechanical switch, the first self-extinguishing switch, and the second self-extinguishing switch are in the off state, the first self-extinguishing switch turns on, and then the mechanical switch turns on.

[0150] According to this, by first turning on the first self-extinguishing switch, a voltage can be applied to the load via the second voltage clamp circuit, thereby reducing the current flowing through the load's capacity.

[0151] (Technical 9) The DC circuit breaker according to Technical 7, wherein when the application of voltage from the power source to the load is started while the mechanical switch, the first self-extinguishing switch, and the second self-extinguishing switch are in the off state, at least one of the mechanical switch and the second self-extinguishing switch turns on, and thereafter the first self-extinguishing switch and the mechanical switch turn on.

[0152] According to this, by first turning on the mechanical switch or the second self-extinguishing switch, a voltage can be applied to the load via the first voltage clamp circuit, thereby reducing the current flowing through the load's capacity.

[0153] (Technical 10) A DC circuit breaker according to any one of Technical 7 to 9, further comprising a first resistor connected in series with the first voltage clamp circuit or the second voltage clamp circuit, wherein when the application of voltage from the power supply to the load is started, the voltage is applied to the load via the first voltage clamp circuit or the second voltage clamp circuit and the first resistor.

[0154] According to this, by applying voltage to the load via a first resistor in addition to the first or second voltage clamp circuit, the current flowing through the load's capacitance can be further reduced. In other words, the inrush current that occurs when the application of voltage from the power supply to the load begins can be further reduced.

[0155] (Technical 11) The DC circuit breaker according to Technical 10, further comprising a third self-extinguishing switch connected in parallel to the first voltage clamp circuit or the second voltage clamp circuit, wherein when the application of voltage from the power supply to the load is started, voltage is applied to the load via the first voltage clamp circuit or the second voltage clamp circuit and the first resistor, thereafter the third self-extinguishing switch is turned on, voltage is applied to the load via the first resistor, thereafter the first self-extinguishing switch and the mechanical switch are turned on.

[0156] According to this, if a third self-extinguishing switch is not provided, when the first self-extinguishing switch and the mechanical switch are turned on, the state changes from one in which voltage is applied to the load via the first or second voltage clamp circuit and the first resistor, to one in which voltage is applied to the load without going through the first or second voltage clamp circuit and the first resistor. In other words, at this time, there is a risk that the current flowing to the load capacity will increase rapidly. Therefore, by turning on the third self-extinguishing switch, the state can be changed from one in which voltage is applied to the load via the first or second voltage clamp circuit and the first resistor, to one in which voltage is applied to the load via the first resistor. In other words, it is possible to suppress the rapid increase in current flowing to the load capacity.

[0157] (Technical 12) A DC circuit breaker according to Technical 10, further comprising a third self-extinguishing switch connected in parallel to the first voltage clamp circuit or the second voltage clamp circuit, and a second resistor connected in series with the third self-extinguishing switch, wherein when the application of voltage from the power supply to the load is started, voltage is applied to the load via the first voltage clamp circuit or the second voltage clamp circuit and the first resistor, thereafter the third self-extinguishing switch is turned on, voltage is applied to the load via the second resistor, thereafter the first self-extinguishing switch and the mechanical switch are turned on.

[0158] According to this, if the third self-extinguishing switch and the second resistor are not provided, when the first self-extinguishing switch and the mechanical switch are turned on, the state in which voltage is applied to the load via the first or second voltage clamp circuit and the first resistor changes to a state in which voltage is applied to the load without going through the first or second voltage clamp circuit and the first resistor. In other words, at this time, there is a risk that the current flowing to the load capacity will increase rapidly. Therefore, by turning on the third self-extinguishing switch, the state in which voltage is applied to the load via the second resistor can be changed from the state in which voltage is applied to the load via the first or second voltage clamp circuit and the first resistor. In other words, the rapid increase in the current flowing to the load capacity can be suppressed. In addition, by providing the first resistor and the second resistor, the short-time rating of each resistor can be used.

[0159] (Technical 13) A DC circuit breaker according to any one of Technical 1 to 12, wherein the first self-extinguishing switch and the second self-extinguishing switch are each bidirectional switches.

[0160] According to this, short-circuit current can be interrupted even when current flows from the load to the power supply (for example, when charging).

[0161] (Technical 14) A DC circuit breaker according to any one of Technical 1 to 13, wherein the DC circuit breaker is connected between one of the positive terminals and negative terminals of the power supply and the load, and another mechanical switch is connected between the other of the positive terminals and negative terminals of the power supply and the load, and the DC circuit breaker interrupts the connection between the one terminal before the other mechanical switch.

[0162] This allows for the interruption of both the positive and negative terminals. Furthermore, by operating the DC circuit breaker before other mechanical switches, arc generation in other mechanical switches can be suppressed. Additionally, if other mechanical switches are located between the negative terminals, the following effects are achieved. Specifically, when power is supplied to the high-side semiconductor switch using a bootstrap circuit, the bootstrap capacitor can be charged before the bootstrap capacitor closes by turning on the low-side semiconductor switch before the other mechanical switch located between the negative terminals closes during switching on. This allows the high-side semiconductor switch to be driven immediately after closing is complete, enabling immediate interruption after closing is complete.

[0163] This disclosure can be applied to DC circuit breakers and the like that connected between a power source and a load.

[0164] 1, 2, 3, 3a, 3b, 4, 4a DC circuit breakers 11, 14, 22, 25 Semiconductor switches 12, 23 MOV 13, 24, 26 Resistors 21, 300 Mechanical switches 31, 32, 36 GD 33 Power supplies 34 Diodes 35 Capacitors 100, 101, 101a Current limiting mechanisms 200, 201, 202, 202a, 202b Circuit breaker mechanisms

Claims

1. A DC circuit breaker connected between a power source and a load, comprising: a current-limiting mechanism having a first self-extinguishing switch and a first voltage clamp circuit connected in parallel; and a tripping mechanism having a mechanical switch and a second self-extinguishing switch connected in parallel, wherein the current-limiting mechanism and the tripping mechanism are connected in series, and the impedance of the first voltage clamp circuit decreases when a voltage lower than the breakdown voltage of the first self-extinguishing switch is applied to the first voltage clamp circuit.

2. The DC circuit breaker according to claim 1, wherein the first voltage clamp circuit includes a clamping element selected from a varistor, an MPS (Merged PIN Schottky) diode, a Zener diode, and a TVS (Transient Voltage Suppressor) diode.

3. The DC circuit breaker according to claim 1, wherein the interruption mechanism further comprises a second voltage clamp circuit connected in parallel with the mechanical switch and the second self-extinguishing switch, and the impedance of the second voltage clamp circuit decreases when a voltage lower than the breakdown voltage of the second self-extinguishing switch is applied to the second voltage clamp circuit.

4. The DC circuit breaker according to claim 3, wherein the second voltage clamp circuit includes a clamping element selected from a varistor, an MPS diode, a Zener diode, and a TVS diode.

5. The DC circuit breaker according to claim 3, wherein the sum of the minimum value of the varistor voltage or breakdown voltage of the second voltage clamp circuit and the breakdown voltage of the second self-extinguishing switch and the varistor voltage or breakdown voltage of the first voltage clamp circuit is greater than or equal to the voltage of the power supply, and at least one of the minimum value of the varistor voltage or breakdown voltage of the second voltage clamp circuit and the breakdown voltage of the second self-extinguishing switch and the varistor voltage or breakdown voltage of the first voltage clamp circuit and the breakdown voltage of the first self-extinguishing switch is less than the voltage of the power supply.

6. A DC circuit breaker according to any one of claims 1 to 5, wherein if a short-circuit fault is detected while the mechanical switch and the first self-extinguishing switch are in the ON state, the first self-extinguishing switch is turned OFF, then the mechanical switch is turned OFF while the second self-extinguishing switch is in the ON state, and then the second self-extinguishing switch is turned OFF.

7. A DC circuit breaker according to any one of claims 3 to 5, wherein when the application of voltage from the power supply to the load is initiated, the voltage is applied to the load via the first voltage clamp circuit or the second voltage clamp circuit.

8. The DC circuit breaker according to claim 7, wherein when the application of voltage from the power supply to the load is started while the mechanical switch, the first self-extinguishing switch, and the second self-extinguishing switch are in the off state, the first self-extinguishing switch turns on, and then the mechanical switch turns on.

9. The DC circuit breaker according to claim 7, wherein when the application of voltage from the power supply to the load is started while the mechanical switch, the first self-extinguishing switch, and the second self-extinguishing switch are in the off state, at least one of the mechanical switch and the second self-extinguishing switch turns on, and thereafter the first self-extinguishing switch and the mechanical switch turn on.

10. The DC circuit breaker according to claim 7, further comprising a first resistor connected in series with the first voltage clamp circuit or the second voltage clamp circuit, wherein when the application of voltage from the power supply to the load is initiated, the voltage is applied to the load via the first voltage clamp circuit or the second voltage clamp circuit and the first resistor.

11. The DC circuit breaker according to claim 10, further comprising a third self-extinguishing switch connected in parallel to the first voltage clamp circuit or the second voltage clamp circuit, wherein when the application of voltage from the power supply to the load is initiated, voltage is applied to the load via the first voltage clamp circuit or the second voltage clamp circuit and the first resistor, thereafter the third self-extinguishing switch is turned on, voltage is applied to the load via the first resistor, and thereafter the first self-extinguishing switch and the mechanical switch are turned on.

12. The DC circuit breaker according to claim 10, further comprising: a third self-extinguishing switch connected in parallel to the first voltage clamp circuit or the second voltage clamp circuit; and a second resistor connected in series with the third self-extinguishing switch, wherein when the application of voltage from the power supply to the load is started, voltage is applied to the load via the first voltage clamp circuit or the second voltage clamp circuit and the first resistor; thereafter, the third self-extinguishing switch is turned on, voltage is applied to the load via the second resistor; and thereafter, the first self-extinguishing switch and the mechanical switch are turned on.

13. The DC circuit breaker according to any one of claims 1 to 5, wherein the first self-extinguishing switch and the second self-extinguishing switch are each bidirectional switches.

14. The DC circuit breaker is connected between one of the positive terminals and negative terminals of the power supply and the load, another mechanical switch is connected between the other of the positive terminals and negative terminals of the power supply and the load, and the DC circuit breaker interrupts the connection between the one terminal before the other mechanical switch, according to any one of claims 1 to 5.

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