Circuit breaker

Abstract

To provide a circuit breaker that can more accurately determine load-related faults. [Solution] The circuit breaker of the embodiment is a circuit breaker connected between a DC power supply and a load, and includes a switching element connected between a first power line connected to the positive terminal of the DC power supply and a second power line connected to the positive terminal of the load, a current sensor for detecting the current value flowing through the second power line, and a control circuit for controlling the gate signal of the switching element based on a gate command. The control circuit includes a first determination circuit that sends an off signal to the switching element to turn it off when the current value of the current sensor exceeds a first threshold, and sends an on signal to the switching element to turn it on after a first time has elapsed since the off signal was sent, and a second determination circuit that determines that a fault has occurred in the load when the switching element repeatedly turns the circuit off and on for two hours or more.

Description

Technical Field

[0001] Embodiments of the present invention relate to a cutoff device for interrupting a direct current.

Background Art

[0002] A DC power supply system that stores power generated from renewable energy in a large-capacity storage battery and uses the power stored in the storage battery has attracted attention. The DC power supply system includes a DC power source such as a storage battery, a load powered from the DC power source via a power line, and a cutoff device provided between the DC power source and the load. The cutoff device interrupts the DC current supplied from the DC power source to the load, for example, when a short circuit occurs in the load, and electrically disconnects the DC power source and the load.

[0003] When supplying DC power, multiple loads may be connected in parallel to the power line connected to the storage battery. In this configuration, a cutoff device is provided for each of the multiple loads. When an accident such as a short circuit occurs in a certain load, it is necessary to quickly cut off the storage battery and the load using the cutoff device to protect the loads and the storage battery where no accident has occurred.

[0004] When using a cutoff device with low loss for DC short circuits to detect a short circuit accident and protect against high-speed interruption of a large current, there is a concern about path interruption due to false detection because a large current is detected at high speed. For example, there is a concern that path interruption will continue due to false detection caused by rush current or noise flowing when a load is connected to the DC power source.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] The problem that this invention aims to solve is to provide a circuit breaker capable of more accurately determining load faults. [Means for solving the problem]

[0007] The circuit breaker according to the embodiment is a circuit breaker connected between a DC power supply and a load, and comprises a switching element connected between a first power line connected to the positive terminal of the DC power supply and a second power line connected to the positive terminal of the load, a current sensor for detecting the current value flowing through the second power line, and a control circuit for controlling the gate signal of the switching element based on a gate command. The control circuit includes a first determination circuit that sends an off signal to the switching element to turn it off when the current value of the current sensor exceeds a first threshold, and sends an on signal to the switching element to turn it on after a first time has elapsed since the off signal was sent, and a second determination circuit that determines that an accident has occurred in the load when the switching element repeatedly turns the circuit off and on for two hours or more. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a circuit diagram of the circuit breaker according to the first embodiment. [Figure 2] Figure 2 is a block diagram of the control circuit. [Figure 3] Figure 3 is a flowchart illustrating the operation of the circuit breaker. [Figure 4] Figure 4 is a block diagram of the control circuit according to the second embodiment. [Figure 5] Figure 5 is a flowchart illustrating the operation of the circuit breaker. [Figure 6] Figure 6 is a block diagram of the control circuit according to the third embodiment. [Figure 7] Figure 7 is a flowchart illustrating the operation of the circuit breaker. [Figure 8] Figure 8 is a block diagram of the control circuit according to the fourth embodiment. [Figure 9]Figure 9 is a flowchart illustrating the operation of the circuit breaker. [Figure 10] Figure 10 is a circuit diagram of the circuit breaker according to the fifth embodiment. [Modes for carrying out the invention]

[0009] The embodiments will be described below with reference to the drawings. The embodiments shown below are illustrative examples of apparatus and methods for realizing the technical concept of the present invention, and the technical concept of the present invention is not defined by the shape, structure, arrangement, etc. of the components. In the following description, elements having the same function and configuration are denoted by the same reference numerals, and redundant descriptions are omitted.

[0010] [1] First Embodiment [1-1] Configuration of the circuit breaker 1 Figure 1 is a circuit diagram of the circuit breaker 1 according to the first embodiment. The circuit breaker 1 is connected between the DC power supply 2 and the load 3. The circuit breaker 1 has the function of electrically interrupting the DC power supply 2 and the load 3 in the event of an accident (or malfunction), such as a short circuit, in the load 3, thereby protecting the DC power supply 2 and the load 3.

[0011] DC power supply 2 generates DC power. DC power supply 2 is constructed using, for example, a large-capacity storage battery. The positive terminal of DC power supply 2 is connected to the circuit breaker 1 via the positive terminal power line (also called the positive terminal line) PL1, and the negative terminal of DC power supply 2 is connected to the negative terminal power line (also called the negative terminal line) NL. The positive terminal line PL1 connected to DC power supply 2 has a parasitic inductance L1. As the length of the positive terminal line PL1 increases, the parasitic inductance L1 increases.

[0012] Load 3 is a device that consumes DC power. An example of Load 3 is a charger for an electric vehicle (EV). The positive terminal of Load 3 is connected to the circuit breaker 1 via the positive terminal wire PL2. The negative terminal of Load 3 is connected to the negative terminal wire NL. The positive terminal wire PL2 connected to Load 3 has a parasitic inductance L2. As the length of the positive terminal wire PL2 increases, the parasitic inductance L2 increases. For example, in a larger DC power supply system, multiple Load 3s are connected in parallel to the power lines of the DC power supply 2, each connected via multiple circuit breakers 1.

[0013] The interruption device 1 comprises a switching element group 10, a current sensor 13, and a control circuit 20. The switching element group 10 comprises a plurality of switching elements 11 and a plurality of diodes 12. By having a plurality of switching elements 11 in the interruption device 1, it is possible to interrupt large DC currents at high speed. However, it is not limited to this, and the number of switching elements 11 may be one.

[0014] The switching element group 10 has the function of electrically isolating the positive electrode line PL1 and the positive electrode line PL2, as well as electrically isolating the DC power supply 2 and the load 3. Multiple switching elements 11 are connected in parallel. The switching elements 11 are composed of semiconductor elements that can operate at higher speeds than mechanical elements, and are composed of, for example, N-channel MOSFETs (Metal Oxide Semiconductor Field Effect Transistors). As the switching elements 11, bipolar transistors, IGBTs (Insulated Gate Bipolar Transistors), or GTOs (Gate Turn Off thyristors) may also be used.

[0015] In the following description, the configuration of one switching element 11 included in the switching element group 10 will be described, but the configurations of the other switching elements 11 are the same. One end (drain terminal D) of the switching element 11 is connected to the positive electrode line PL1, and the other end (source terminal S) of the switching element 11 is connected to the positive electrode line PL2. The gate terminal G of the switching element 11 is connected to the control circuit 20.

[0016] A diode 12 is connected in reverse parallel to the switching element 11. The diode 12 is a freewheeling diode and has a function of protecting the switching element 11 when a reverse current is supplied to the switching element 11. The diode 12 may be constituted by a parasitic diode of a transistor.

[0017] The current sensor 13 is connected to the positive electrode line PL2. The current sensor 13 detects the current value flowing through the positive electrode line PL2, that is, the current value flowing through the load 3. The current value detected by the current sensor 13 is sent to the control circuit 20 as a current detection signal CDS.

[0018] The control circuit 20 controls the operation of the cutoff device 1. The control circuit 20 supplies a gate signal to the switching element 11 to control the on / off of the switching element 11. Further, the control circuit 20 determines whether an accident such as a short circuit has occurred in the load 3 based on the current detection signal CDS, and controls the switching element 11 to be turned off when it is determined that an accident has occurred in the load 3.

[0019] FIG. 2 is a block diagram of the control circuit 20. The control circuit 20 includes a comparator 21, a cutoff determination circuit 22, and a short circuit determination circuit 23.

[0020] The control circuit 20 receives gate commands from an external device. The gate command is asserted when energizing load 3 (driving load 3) and negated when stopping the energizing of load 3. Asserting is the same as activating, and negating is the same as deactivating. In basic operation, the control circuit 20 turns on the switching element 11 when the gate command is asserted (when energizing load 3) and turns off the switching element 11 when the gate command is negated (when stopping the energizing of load 3).

[0021] Comparator 21 compares the current value of the current detection signal CDS with the first threshold Vth1. Comparator 21 operates to output a high level when a current greater than the rated current of load 3 flows through it.

[0022] The interruption determination circuit 22 turns off the switching element 11 when the comparator 21 outputs a high level. After a predetermined time has elapsed, the interruption determination circuit 22 turns on the switching element 11.

[0023] The short-circuit detection circuit 23 determines whether the switching element 11 has repeatedly switched off and on for a predetermined period of time or longer. If the switching element 11 has repeatedly switched off and on for a predetermined period of time or longer, the short-circuit detection circuit 23 determines that an accident (including a short circuit) has occurred in the load 3. The short-circuit detection circuit 23 then turns off the switching element 11.

[0024] The control circuit 20 may be configured in hardware, in software, or both. If the control circuit 20 is configured in software, it is configured to include a processor (e.g., a CPU (Central Processing Unit)) and a memory unit.

[0025] [1-2] Operation Next, we will explain the operation of the circuit breaker 1 configured as described above. Figure 3 is a flowchart illustrating the operation of the circuit breaker 1.

[0026] The control circuit 20 receives a gate command from an external device (step S100). The gate command instructs the load 3 to be energized. In normal operation, if the gate command is negated, the control circuit 20 turns off the switching element 11.

[0027] Next, the short-circuit detection circuit 23 sends an ON signal to the switching element 11 (step S101). Specifically, the short-circuit detection circuit 23 supplies an ON signal to the gate terminal of the switching element 11. The ON signal is a voltage signal that can turn on the switching element 11. As a result, the switching element 11 (specifically, all of the switching elements 11) are turned on.

[0028] The current sensor 13 detects the current value of the positive electrode wire PL2. The control circuit 20 receives a current detection signal CDS from the current sensor 13 (step S102).

[0029] Next, the comparator 21 compares the current value of the current detection signal CDS with the first threshold Vth1 (step S103). The first threshold Vth1 is used to determine whether a current greater than the rated current of the load 3 has flowed through the load 3. The first threshold Vth1 is set appropriately according to the rated current of the load 3 and is set to a current value that is a certain value higher than the rated current of the load 3. If the current value of the current detection signal CDS exceeds the first threshold Vth1, the comparator 21 outputs, for example, a high level. The comparison result of the comparator 21 is sent to the interruption determination circuit 22.

[0030] If the current value of the current detection signal CDS is less than or equal to the first threshold Vth1 (step S104 = No), the control circuit 20 continues to supply power to the load 3.

[0031] If the current value of the current detection signal CDS exceeds the first threshold Vth1 (step S104 = Yes), the interruption determination circuit 22 sends an off signal to the switching element 11 (step S105). Specifically, the interruption determination circuit 22 supplies an off signal to the gate terminal of the switching element 11 via the short-circuit determination circuit 23. The off signal is a voltage signal capable of turning off the switching element 11. As a result, the switching element 11 (specifically, all of the switching elements 11) are turned off.

[0032] Next, the interruption determination circuit 22 monitors whether or not a first time has elapsed since the off signal was sent (step S106). After the first time has elapsed (step S106 = Yes), the interruption determination circuit 22 sends an on signal to the switching element 11 via the short-circuit determination circuit 23 (step S107). As a result, the switching element 11 turns on. The first time can be set arbitrarily.

[0033] Next, the short-circuit detection circuit 23 determines, based on the determination result of the interruption detection circuit 22, whether or not the interruption / continuity has been repeated for two hours or more (step S108). Interruption has the same meaning as turning off the switching element 11, meaning that the DC power supply 2 and the load 3 are interrupted. Continuity has the same meaning as turning on the switching element 11, meaning that the DC power supply 2 and the load 3 are connected. "Interruption / continuity" refers to a set of operations: the switching element 11 is turned off, interrupting the DC power supply 2 and the load 3, and the switching element 11 is turned on, connecting the DC power supply 2 and the load 3.

[0034] The second time interval is set to separate a single-pulse inrush current from a short-circuit current. Alternatively, the second time interval is set to separate a single-pulse (or approximately two-pulse) noise from a short-circuit current. For example, the second time interval is set to the time it takes for one or two interruption / conduction cycles to repeat. The second time interval is set to be longer than the first time interval.

[0035] If the interruption / continuity is repeated for more than two hours (step S108 = Yes), the short-circuit detection circuit 23 determines that a fault (including a short circuit) has occurred in the load 3. When a short circuit occurs in the load 3, a large current flows to the load 3 each time the switching element 11 turns on. In other words, the interruption / continuity is repeated many times. On the other hand, when an inrush current flows to the load 3, the load 3 is energized after the interruption / continuity occurs about once. Therefore, by performing the operation in step S108, it is possible to determine whether or not a fault has occurred in the load 3. In other words, the control circuit 20 can distinguish whether an inrush current or noise has flowed to the load 3, or whether a fault has occurred in the load 3.

[0036] The short-circuit detection circuit 23 then sends an off signal to the switching element 11. This causes the switching element 11 to turn off. As a result, damage caused by a fault in load 3 can be suppressed.

[0037] If the circuit breaker / conduction has not been repeated for more than two hours (step S108 = No), the short-circuit detection circuit 23 determines that no fault has occurred in load 3. The short-circuit detection circuit 23 returns to step S103 and continues to monitor the current detection signal CDS.

[0038] [1-3] Effects of the first embodiment According to the first embodiment, the control circuit 20 determines that a fault (including a short circuit) has occurred in the load 3 if the circuit is repeatedly interrupted / conducted for two hours or more. If the control circuit 20 determines that a fault has occurred in the load 3, it keeps the switching element 11 continuously off. On the other hand, if the circuit is not repeatedly interrupted / conducted for two hours or more, the control circuit 20 determines that an inrush current or noise has flowed through the load 3. In this case, the control circuit 20 continues to energize the load 3. This prevents misidentification of inrush current or noise as a fault. It also makes it possible to more accurately determine a fault in the load 3.

[0039] Furthermore, in the event of a fault in load 3, the damage caused by the fault can be mitigated. Additionally, damage to DC power supply 2 due to a fault in load 3 can be mitigated.

[0040] Furthermore, the switching element 11 is composed of a semiconductor element consisting of an FET. Therefore, the interruption device 1 can interrupt the DC current at high speed.

[0041] [2] Second embodiment In the second embodiment, an upper and lower threshold value is set for the current value of the current sensor 13. The switching element 11 is turned off when the current value of the current sensor 13 exceeds the upper threshold value, and the switching element 11 is turned on when the current value of the current sensor 13 falls below the lower threshold value.

[0042] [2-1] Configuration of the circuit breaker 1 Figure 4 is a block diagram of the control circuit 20 according to the second embodiment. The control circuit 20 includes a first comparator 21-1, a second comparator 21-2, a circuit breaker detection circuit 22, and a short-circuit detection circuit 23.

[0043] The first comparator 21-1 compares the current value of the current detection signal CDS with the upper threshold (first threshold Vth1). The comparator 21-1 operates to output a high level when a current greater than the rated current of load 3 flows. The first comparator 21-1 operates in the same way as the comparator 21 of the first embodiment.

[0044] The second comparator 21-2 compares the current value of the current detection signal CDS with the lower threshold (second threshold Vth2). The second comparator 21-2 operates to output a high level when the current flowing through load 3 becomes sufficiently smaller than the rated current.

[0045] The interruption determination circuit 22 turns off the switching element 11 when the first comparator 21-1 outputs a high level. Subsequently, the interruption determination circuit 22 turns on the switching element 11 when the second comparator 21-2 outputs a high level.

[0046] The operation of the short-circuit detection circuit 23 is the same as in the first embodiment.

[0047] [2-2] Operation Next, the operation of the circuit breaker 1 configured as described above will be explained. Figure 5 is a flowchart illustrating the operation of the circuit breaker 1. The operation in steps S200 to S205 in Figure 5 is the same as the operation in steps S100 to S105 in Figure 3.

[0048] Next, the second comparator 21-2 compares the current value of the current detection signal CDS with the second threshold Vth2 (step S206). Since the switching element 11 is turned off in step S205, the current value detected by the current sensor 13 decreases. The second threshold Vth2 is used to determine whether the current value has fallen sufficiently below the rated current of the load 3. The second threshold Vth2 is set appropriately according to the rated current of the load 3 and is set to a current value that is a certain value lower than the rated current of the load 3. The first threshold Vth1 and the second threshold Vth2 satisfy the relationship "Vth1 > Vth2". The comparator 21-2 outputs, for example, a high level when the current value of the current detection signal CDS falls below the second threshold Vth2. The comparison result of the comparator 21-2 is sent to the cutoff determination circuit 22.

[0049] If the current value of the current detection signal CDS is greater than or equal to the second threshold Vth2 (step S207=No), the control circuit 20 continues in the cutoff state.

[0050] If the current value of the current detection signal CDS falls below the second threshold Vth2 (step S207 = Yes), the cutoff determination circuit 22 sends an ON signal to the switching element 11 (step S208). As a result, the switching element 11 turns ON.

[0051] Next, the short-circuit detection circuit 23 determines, based on the determination result of the interruption detection circuit 22, whether or not interruption / continuity has been repeated for two hours or more (step S209). The second hour is set in the same way as in the first embodiment.

[0052] If the circuit is repeatedly interrupted / conducted for more than two hours (step S209 = Yes), the short-circuit detection circuit 23 determines that a fault (including a short circuit) has occurred in the load 3. The short-circuit detection circuit 23 then sends an off signal to the switching element 11. This causes the switching element 11 to turn off. As a result, damage caused by the fault in the load 3 can be suppressed.

[0053] If the circuit breaker / conduction has not been repeated for more than two hours (step S209 = No), the short-circuit detection circuit 23 determines that no fault has occurred in load 3. The short-circuit detection circuit 23 returns to step S203 and continues to monitor the current detection signal CDS.

[0054] [2-3] Effects of the second embodiment According to the second embodiment, when a large current flows through the load 3, the switching element 11 can more accurately determine whether to interrupt or conduct. Other effects are the same as in the first embodiment.

[0055] Furthermore, the first and second embodiments may be combined. That is, the determination in step S106 and the determination in step S207 may be performed in parallel or in series, and the switching element 11 may be turned on if either condition is met.

[0056] [3] Third embodiment The third embodiment calculates the period of repeated interruption / conduction and determines whether or not a fault has occurred in load 3 based on the frequency change of the repeated interruption / conduction.

[0057] [3-1] Configuration of the circuit breaker 1 Figure 6 is a block diagram of the control circuit 20 according to the third embodiment. The control circuit 20 includes a comparator 21, a cutoff determination circuit 22, a short-circuit determination circuit 23, and a counter 24.

[0058] The operation of the comparator 21 and the cutoff determination circuit 22 is the same as in the first embodiment.

[0059] The counter 24 increments its count value by 1 when the output of the comparator 21 becomes high level.

[0060] The short-circuit detection circuit 23 determines whether the interruption / conduction cycle has been repeated multiple times based on the count value of the counter 24. If the interruption / conduction cycle has been repeated multiple times, the short-circuit detection circuit 23 calculates the first period of interruption / conduction repetitions in the first period of the repetition period and the second period of interruption / conduction repetitions in the second period following the first period. If the first period and the second period are approximately the same, the short-circuit detection circuit 23 determines that a fault has occurred in the load 3 and turns off the switching element 11.

[0061] Load 3 consists of a device that includes a capacitive component. Load 3 consists of, for example, a storage battery.

[0062] [3-2] Operation Next, the operation of the circuit breaker 1 configured as described above will be explained. Figure 7 is a flowchart illustrating the operation of the circuit breaker 1. The operation in steps S300 to S305 in Figure 7 is the same as the operation in steps S100 to S105 in Figure 3.

[0063] Next, when the output of the comparator 21 becomes high level, the counter 24 increments by 1 (step S306). The count value of the counter 24 is sent to the short-circuit detection circuit 23.

[0064] Next, the interruption determination circuit 22 monitors whether or not a first time has elapsed since the off signal was sent (step S307). After the first time has elapsed (step S307 = Yes), the interruption determination circuit 22 sends an on signal to the switching element 11 via the short-circuit determination circuit 23 (step S308). This turns on the switching element 11. The first time can be set arbitrarily.

[0065] Next, the short-circuit detection circuit 23 determines whether the interruption / conduction has been repeated multiple times (a predetermined number of times) based on the count value of the counter 24 (step S309). One interruption / conduction can be determined by the counter 24's count value increasing by 1. The short-circuit detection circuit 23 determines that the interruption / conduction has been repeated multiple times when the counter 24's count value increases continuously, and further determines whether the interruption / conduction has been repeated a predetermined number of times. The predetermined number of times is, for example, 5 to 15 times.

[0066] If the interruption / conduction cycle is repeated a predetermined number of times (step S309 = Yes), the short-circuit detection circuit 23 determines the period of the interruption / conduction cycle (step S310). The period of the interruption / conduction cycle can be calculated by calculating the period during which the count value of the counter 24 is incremented. Specifically, the short-circuit detection circuit 23 calculates the period of the interruption / conduction cycle for the first (or second) time since the interruption / conduction cycle began (first period) and the period of the interruption / conduction cycle for any of the 5th to 15th times (second period). Of the repeating period during which the interruption / conduction cycle is repeated multiple times, the period up to the first (or second) time is called the first period, and the period from the 5th to the 15th time is called the second period. Next, the short-circuit detection circuit 23 compares the first period and the second period (step S311).

[0067] If the first and second periods are approximately the same, that is, if there is no change in the period (step S311 = Yes), the short-circuit detection circuit 23 determines that a fault (including a short circuit) has occurred in the load 3. When a short circuit occurs in the load 3, the large current flowing through the load 3 is approximately constant, so interruption / conduction is repeated at a constant period. On the other hand, when the load 3 is being charged under normal operation, the charging current flowing through the load 3 changes over time, so the interruption / conduction period changes. Therefore, by performing the operation in step S310, it is possible to determine whether or not a fault has occurred in the load 3.

[0068] The short-circuit detection circuit 23 then sends an off signal to the switching element 11. This causes the switching element 11 to turn off. As a result, damage caused by a fault in load 3 can be suppressed.

[0069] If there is a change in the period (step S311 = No), the short-circuit detection circuit 23 determines that no fault has occurred in load 3. The short-circuit detection circuit 23 returns to step S303 and continues monitoring the current detection signal CDS.

[0070] In step S311, the short-circuit detection circuit 23 may determine that a fault has occurred if the rate of change between the first and second cycles is less than 20%.

[0071] [3-3] Effects of the third embodiment According to the third embodiment, it is possible to more accurately determine whether load 3 is being charged under normal operation or whether a malfunction has occurred in load 3. Other effects are the same as in the first embodiment.

[0072] [4] Fourth Embodiment The fourth embodiment is an example in which the third embodiment is applied to the second embodiment.

[0073] [4-1] Configuration of the circuit breaker 1 Figure 8 is a block diagram of the control circuit 20 according to the fourth embodiment. The control circuit 20 includes a first comparator 21-1, a second comparator 21-2, a cutoff determination circuit 22, a short-circuit determination circuit 23, and a counter 24.

[0074] The operation of the first comparator 21-1, the second comparator 21-2, and the cutoff determination circuit 22 is the same as in the second embodiment.

[0075] The operation of the counter 24 and the short-circuit detection circuit 23 is the same as in the third embodiment.

[0076] Load 3 consists of a device that includes a capacitive component. Load 3 consists of, for example, a storage battery.

[0077] [4-2] Operation Next, the operation of the circuit breaker 1 configured as described above will be explained. Figure 9 is a flowchart illustrating the operation of the circuit breaker 1. The operation in steps S400 to S405 in Figure 9 is the same as the operation in steps S200 to S205 in Figure 5.

[0078] Next, when the output of the first comparator 21-1 becomes high level, the counter 24 increments by 1 (step S406). The count value of the counter 24 is sent to the short-circuit detection circuit 23.

[0079] Next, the second comparator 21-2 compares the current value of the current detection signal CDS with the second threshold Vth2 (step S407). Since the switching element 11 is turned off in step S405, the current value detected by the current sensor 13 decreases. The conditions for the first threshold Vth1 and the second threshold Vth2 are the same as in the second embodiment. The comparison result from the comparator 21-2 is sent to the cutoff determination circuit 22.

[0080] If the current value of the current detection signal CDS is greater than or equal to the second threshold Vth2 (step S408=No), the control circuit 20 continues to cut off power to the load 3.

[0081] If the current value of the current detection signal CDS falls below the second threshold Vth2 (step S408 = Yes), the cutoff determination circuit 22 sends an ON signal to the switching element 11 (step S409). As a result, the switching element 11 turns ON.

[0082] Next, the short-circuit detection circuit 23 determines whether the interruption / conduction has been repeated multiple times (a predetermined number of times) based on the count value of the counter 24 (step S410). The operation of steps S410 to S413 in Figure 9 is the same as the operation of steps S309 to S312 in Figure 7.

[0083] In step S412, the short-circuit detection circuit 23 may determine that a fault has occurred if the rate of change between the first and second cycles is less than 20%.

[0084] [4-3] Effects of the fourth embodiment According to the fourth embodiment, when a large current flows through the load 3, the switching element 11 can more accurately determine whether it is interrupted or conducting. It can also more accurately determine whether the load 3 is being charged under normal operation or whether a fault has occurred in the load 3. Other effects are the same as in the first embodiment.

[0085] [5] Fifth embodiment The fifth embodiment is an embodiment that further includes a protection circuit.

[0086] Figure 10 is a circuit diagram of the circuit breaker 1 according to the fifth embodiment. The circuit breaker 1 further comprises a snubber circuit 30 and a return circuit 40.

[0087] The snubber circuit 30 is connected between the positive electrode wire PL1 and the negative electrode wire NL. The snubber circuit 30 comprises a capacitor 31 and a resistor 32. One electrode of the capacitor 31 is connected to the positive electrode wire PL1, and the other electrode of the capacitor 31 is connected to one end of the resistor 32. The other end of the resistor 32 is connected to the negative electrode wire NL.

[0088] The snubber circuit 30 has the function of suppressing the surge voltage generated when the interruption device 1 is interrupted, thereby protecting the switching element 11. The capacitor 31 included in the snubber circuit 30 has the function of suppressing the surge voltage generated when the DC power supply 2 is interrupted due to the parasitic inductance L1. The resistor element 32 included in the snubber circuit 30 has the function of suppressing resonance between the parasitic inductance L1 and the capacitor 31.

[0089] The freewheel circuit 40 is connected between the positive electrode line PL2 and the negative electrode line NL. The freewheel circuit 40 comprises one or more diodes 41 and one or more Zener diodes 42. Figure 10 shows an example with two diodes 41 and two Zener diodes 42.

[0090] Two diodes 41 are connected in series, and two Zener diodes 42 are also connected in series. The anode of one diode 41 is connected to the negative terminal line NL, and the cathode of the other diode 41 is connected to the cathode of the other Zener diode 42. The anode of the other Zener diode 42 is connected to the positive terminal line PL2.

[0091] When the circuit breaker 1 is tripped, current flows to the load 3 due to the energy stored in the parasitic inductance L2 on the load 3 side. The diode 41 has the function of returning the current generated due to the parasitic inductance L2 to the load 3. The number of diodes 41 is set according to the magnitude of the return current. By connecting multiple diodes 41 in series, the withstand voltage of the diode group can be increased.

[0092] The Zener diode 42 has the function of reducing and dissipating the freewheeling current flowing to the load 3. When a voltage is applied, the Zener diode 42 acts like a resistor. The Zener diode 42 is also called a TVS (transient-voltage-suppression) diode. By providing the Zener diode 42, the energy accumulated in the wiring on the load 3 side can be dissipated more quickly. In particular, when the wiring on the load 3 side becomes long, the energy accumulated in the parasitic inductance L2 becomes large. Even in this case, the Zener diode 42 can dissipate the freewheeling current generated by the energy accumulated in the parasitic inductance L2 more quickly. The number of Zener diodes 42 is set according to the magnitude of the freewheeling current.

[0093] The other configurations are the same as in the first embodiment. The fifth embodiment is also applicable to the second to fourth embodiments.

[0094] In each of the above embodiments, "connected" means electrically connected, and does not exclude the presence of electrical circuit elements (including passive elements) in between.

[0095] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of symbols]

[0096] 1... Circuit breaker, 2... DC power supply, 3... Load, 10... Switching element group, 11... Switching element, 12... Diode, 13... Current sensor, 20... Control circuit, 21... Comparator, 21-1... First comparator, 21-2... Second comparator, 22... Circuit breaker detection circuit, 23... Short circuit detection circuit, 24... Counter, 30... Snubber circuit, 31... Capacitor, 32... Resistor element, 40... Freewheeling circuit, 41... Diode, 42... Zener diode, L1... Parasitic inductance, L2... Parasitic inductance, PL1, PL2... Positive side power supply line, NL... Negative side power supply line.

Claims

1. A circuit breaker connected between a DC power supply and a load, A switching element is connected between a first power line connected to the positive terminal of the DC power supply and a second power line connected to the positive terminal of the load. A current sensor that detects the current value flowing through the second power line, A control circuit that controls the gate signal of the switching element based on a gate command, It is equipped with, The aforementioned control circuit is A first determination circuit that, when the current value of the current sensor exceeds a first threshold, sends an off signal to the switching element to turn it off, and after a first time has elapsed since the off signal was sent, sends an on signal to the switching element to turn it on. The system includes a second determination circuit that determines that an accident has occurred in the load if the switching element repeatedly interrupts / conducts the load for two hours or more. Circuit breaker.

2. A circuit breaker connected between a DC power supply and a load, A switching element is connected between a first power line connected to the positive terminal of the DC power supply and a second power line connected to the positive terminal of the load. A current sensor that detects the current value flowing through the second power line, A control circuit that controls the gate signal of the switching element based on a gate command, It is equipped with, The aforementioned control circuit is A first determination circuit sends an off signal to the switching element to turn it off when the current value of the current sensor exceeds a first threshold, and sends an on signal to the switching element to turn it on when the current value of the current sensor falls below a second threshold that is lower than the first threshold. The system includes a second determination circuit that determines that an accident has occurred in the load if the switching element repeatedly interrupts / conducts the load for two hours or more. Circuit breaker.

3. A circuit breaker connected between a DC power supply and a load, A switching element is connected between a first power line connected to the positive terminal of the DC power supply and a second power line connected to the positive terminal of the load. A current sensor that detects the current value flowing through the second power line, A control circuit that controls the gate signal of the switching element based on a gate command, It is equipped with, The aforementioned control circuit is A first determination circuit that, when the current value of the current sensor exceeds a first threshold, sends an off signal to the switching element to turn it off, and after a first time has elapsed since the off signal was sent, sends an on signal to the switching element to turn it on. The system includes a second determination circuit that, when the switching element repeatedly switches between on and off multiple times, calculates the first period of repeated switching between on and off in a first period and the second period of repeated switching between on and off in a second period following the first period, and determines that a fault has occurred in the load if the first period and the second period are the same. Circuit breaker.

4. A circuit breaker connected between a DC power supply and a load, A switching element is connected between a first power line connected to the positive terminal of the DC power supply and a second power line connected to the positive terminal of the load. A current sensor that detects the current value flowing through the second power line, A control circuit that controls the gate signal of the switching element based on a gate command, It is equipped with, The aforementioned control circuit is A first determination circuit sends an off signal to the switching element to turn it off when the current value of the current sensor exceeds a first threshold, and sends an on signal to the switching element to turn it on when the current value of the current sensor falls below a second threshold that is lower than the first threshold. The system includes a second determination circuit that, when the switching element repeatedly switches between on and off multiple times, calculates the first period of repeated switching between on and off in a first period and the second period of repeated switching between on and off in a second period following the first period, and determines that a fault has occurred in the load if the first period and the second period are the same. Circuit breaker.

5. The control circuit further includes a counter that counts the number of times the current value of the current sensor exceeds the first threshold, The second determination circuit calculates the period of repeated interruption / conduction based on the count value of the counter. The circuit breaker according to claim 3 or 4.

6. The second determination circuit sends an off signal to the switching element when it determines that a fault has occurred in the load. The circuit breaker according to any one of claims 1 to 4.

7. The system further comprises a snubber circuit connected between the first power line and the negative terminal of the DC power supply, The snubber circuit includes a capacitor and a resistor connected in series. The circuit breaker according to any one of claims 1 to 4.

8. The system further comprises a recirculation circuit connected between the second power line and the negative terminal of the load, The aforementioned freewheeling circuit includes a Zener diode and a diode connected in series. The circuit breaker according to any one of claims 1 to 4.

9. The switching element is composed of an FET (Field Effect Transistor). The circuit breaker according to any one of claims 1 to 4.

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