Current breaker device

Abstract

This current breaker device (20) is included in an onboard system (1) comprising a power supply unit (for example, a first power supply unit (11), a second power supply unit (12)), a power path (13) over which power from the power supply unit is supplied, a plurality of branch paths (14) branching from the power path (13), and a load (15) connected to each branch path (14). The current breaker device (20) has a switch unit (for example, first switch units (21A, 21B, 21C)) provided in at least one of the branch paths (14), and a control unit (30) for switching the switch unit to the off state when the value of the current flowing through the switch unit exceeds an overcurrent threshold value. The control unit (30) sets an overcurrent threshold value on the basis of at least one of the voltage over the power path (13), the temperature of the switch unit, and the vehicle state.

Description

Current interrupter

[0001] The present disclosure relates to a current interruption device.

[0002] Patent Documents 1 and 2 disclose a configuration in which a switch is provided between a power supply and a load. For example, Patent Document 1 describes turning off a switch (semiconductor element) in response to a voltage drop. Patent Document 2 also describes cutting off the output current by an output transistor when the load is in a complete short-circuit state, and suppressing the output current by turning the output transistor on and off when the load is in an incomplete short-circuit state.

[0003] JP 2009-231969 A JP 2013-255117 A

[0004] In Patent Documents 1 and 2, the conditions for turning off the switch are always constant. However, there are cases where it is preferable to change the turning-off conditions depending on the situation.

[0005] An object of the present disclosure is to provide a technology that makes it possible to change the conditions for cutting off current supplied to a load depending on the situation.

[0006] The current interruption device of the present disclosure is a current interruption device included in an in-vehicle system having a power supply unit, a power path to which power is supplied from the power supply unit, a plurality of branch paths branching off from the power path, and a load connected to each of the branch paths, and has: a switch unit provided in at least one of the branch paths; and a control unit that switches the switch unit to an off state when the current value flowing through the switch unit exceeds an overcurrent threshold, and the control unit sets the overcurrent threshold based on at least one of the voltage of the power path, the temperature of the switch unit, and the vehicle state.

[0007] The technology according to the present disclosure can vary the conditions for cutting off the current supplied to the load depending on the situation.

[0008] Fig. 1 is a configuration diagram of an in-vehicle system including a current interruption device of a first embodiment. Fig. 2 is a graph showing a change in voltage of the power path 13 and a change in the value of the current flowing through the first switch unit 21A when a layer short occurs in the load 15A and the first switch unit 21A is switched to the OFF state. Fig. 3 is a configuration diagram of an in-vehicle system including a current interruption device of a second embodiment. Fig. 4 is a configuration diagram of an in-vehicle system including a current interruption device of a third embodiment.

[0009] [Description of Embodiments of the Present Disclosure] In the following, embodiments according to the present disclosure are listed and exemplified.

[0010] [1] A current interruption device included in an in-vehicle system having a power supply unit, a power path to which power is supplied from the power supply unit, a plurality of branch paths branching off from the power path, and a load connected to each of the branch paths, the current interruption device having: a switch unit provided in at least one of the branch paths; and a control unit that switches the switch unit to an off state when a current value flowing through the switch unit exceeds an overcurrent threshold, the control unit setting the overcurrent threshold based on at least one of the voltage of the power path, the temperature of the switch unit, and a vehicle state.

[0011] The above-mentioned current interruption device can vary the conditions for interrupting the current supplied to the load depending on the situation by setting an overcurrent threshold based on at least one of the voltage of the power path, the temperature of the switch unit, and the vehicle state.

[0012] [2] The current interruption device described in [1], wherein the control unit sets the overcurrent threshold to a smaller value when the voltage of the power path is equal to or lower than a threshold voltage compared to when the voltage of the power path is greater than the threshold voltage.

[0013] Even if a ground fault does not occur, a voltage drop in the power path can occur if some loads experience a layer short. However, the voltage drop in the case of a layer short is smaller than in the case of a ground fault. Therefore, in order to detect a layer short, it is necessary to set the overcurrent threshold to a small value. However, setting the overcurrent threshold to a small value increases the likelihood of erroneous determination. Therefore, the current interruption device sets the overcurrent threshold to a small value when the voltage of the power path is equal to or lower than the threshold voltage. With this configuration, when the voltage of the power path exceeds the threshold voltage, a large value is set as the overcurrent threshold, making erroneous determination less likely. Furthermore, even if a layer short occurs, it can be considered unavoidable because the voltage of the power path exceeds the threshold voltage. On the other hand, the current interruption device sets the overcurrent threshold to a small value when the voltage of the power path falls below the threshold voltage. This makes it easier to interrupt the current to the load causing the voltage drop. As a result, if the current to the load causing the voltage drop is interrupted, the voltage of the power path is more likely to return to a state greater than the threshold voltage.

[0014] [3] The current interruption device according to [2], wherein the threshold voltage is a value greater than the minimum voltage at which each of the loads can operate.

[0015] The current interruption device sets the overcurrent threshold to a small value before the voltage of the power line falls below the minimum voltage at which each load can operate. This makes it easier to interrupt the current to the load that is causing the voltage drop before the voltage of the power line falls below the minimum voltage at which each load can operate. This makes it harder for the voltage of the power line to fall below the minimum voltage at which each load can operate.

[0016] [4] A current interruption device described in any of [1] to [3], wherein when the temperature of the switch unit exceeds a threshold temperature, the control unit sets the overcurrent threshold to a smaller value than when the temperature of the switch unit is below the threshold temperature.

[0017] The above current interruption device has a high overcurrent threshold when the temperature of the switch unit is below the threshold temperature, making it easy to prevent the switch unit from tripping accidentally. On the other hand, the above current interruption device sets the overcurrent threshold to a small value when the temperature of the switch unit exceeds the threshold temperature. This makes it easier for the switch unit to trip. As a result, if the switch unit trips, the temperature rise of the switch unit due to overcurrent is suppressed.

[0018] [5] A current interruption device described in any one of [1] to [4], wherein the control unit sets the overcurrent threshold to a smaller value when the vehicle is parked compared to when the vehicle is moving.

[0019] The current interruption device has a high overcurrent threshold when the vehicle is running, making it easy to prevent the switch unit from tripping accidentally. On the other hand, the current interruption device sets the overcurrent threshold to a small value when the vehicle is parked. This makes it easier for the switch unit to trip, making it easier to maintain the voltage of the power line at or above the threshold voltage.

[0020] [6] A current interruption device according to any one of [1] to [5], further comprising a current detection unit that detects the value of a current flowing through the switch unit, wherein the control unit includes an overcurrent detection circuit that outputs an off signal when it is determined that the current value detected by the current detection unit exceeds the overcurrent threshold, and wherein the switch unit switches to an off state in response to the off signal being output from the overcurrent detection circuit.

[0021] The current interruption device uses an overcurrent detection circuit, which allows it to quickly perform operations from detecting an overcurrent to switching the switch unit to the OFF state.

[0022] [7] The current interruption device described in [6], wherein the control unit sets the overcurrent threshold to a smaller value when the voltage of the power path is equal to or lower than a threshold voltage compared to when the voltage of the power path is higher than the threshold voltage, and further has a voltage detection unit that detects the voltage of the power path, and the control unit includes a threshold setting circuit that sets the overcurrent threshold based on the voltage detected by the voltage detection unit.

[0023] The current interruption device described above can quickly perform the operation of setting the overcurrent threshold based on the voltage of the power line by using the threshold setting circuit.

[0024] [8] The current interruption device described in [6] or [7], wherein the control unit sets the overcurrent threshold to a smaller value when the temperature of the switch unit exceeds a threshold temperature compared to when the temperature of the switch unit is equal to or lower than the threshold temperature, and further has a temperature detection unit that detects the temperature of the switch unit, and the control unit includes a threshold setting circuit that sets the overcurrent threshold based on the temperature detected by the temperature detection unit.

[0025] The current interruption device uses a threshold setting circuit, which allows the device to quickly set the overcurrent threshold based on the temperature of the switch unit.

[0026] [Details of the embodiment of the present disclosure] 1. First embodiment 1-1. Configuration of in-vehicle system 1 The in-vehicle system 1 of the first embodiment shown in FIG. 1 is a system mounted on a vehicle. The in-vehicle system 1 includes a first power supply unit 11, a second power supply unit 12, and a power path 13. The power path 13 is provided between the first power supply unit 11 and the second power supply unit 12. The first power supply unit 11 and the second power supply unit 12 each correspond to an example of a power supply unit.

[0027] The first power supply unit 11 has a power supply source 11A and a voltage conversion unit 11B. The power supply source 11A is configured by, for example, a battery or a generator. The voltage conversion unit 11B boosts or lowers the voltage input from the power supply source 11A and outputs the boosted or lowered voltage. The first power supply unit 11 applies the output voltage of the voltage conversion unit 11B to one end of the power path 13.

[0028] The second power supply unit 12 includes a battery 12A. The battery 12A is, for example, a lithium-ion battery. The second power supply unit 12 applies the output voltage of the battery 12A to the other end of the power path 13.

[0029] The in-vehicle system 1 includes a plurality of branch paths 14 branching off from a power path 13, and loads 15 connected to each of the branch paths 14. The plurality of branch paths 14 include branch paths 14A, 14B, and 14C. A load 15A is electrically connected to the branch path 14A. A load 15B is electrically connected to the branch path 14B. A load 15C is electrically connected to the branch path 14C.

[0030] The in-vehicle system 1 includes a current interruption device 20. The current interruption device 20 has first switch units 21A, 21B, and 21C, second switch units 22A and 22B, current detection units 23A, 23B, and 23C, a voltage detection unit 24, and a control unit 30.

[0031] The first switch units 21A, 21B, and 21C correspond to examples of switch units. The first switch unit 21A is provided in the branch path 14A. The first switch unit 21B is provided in the branch path 14B. The first switch unit 21C is provided in the branch path 14C. The first switch units 21A, 21B, and 21C each switch between an ON state that allows current to flow to the load 15 side and an OFF state that blocks current flowing to the load 15 side. The first switch units 21A, 21B, and 21C may be mechanical switches or semiconductor switches.

[0032] The second switch unit 22A is provided on the power path 13. The second switch unit 22A is provided closer to the first power supply unit 11 than any of the loads 15. The second switch unit 22A switches between an ON state, which allows current to flow to the first power supply unit 11 side, and an OFF state, which blocks current flowing to the first power supply unit 11 side. The second switch unit 22A may be a mechanical switch or a semiconductor switch.

[0033] The second switch unit 22B is provided on the power path 13. The second switch unit 22B is provided closer to the second power supply unit 12 than any of the loads 15. The second switch unit 22B switches between an ON state, which allows current to flow to the second power supply unit 12 side, and an OFF state, which blocks current flowing to the second power supply unit 12 side. The second switch unit 22B may be a mechanical switch or a semiconductor switch.

[0034] The current detection units 23A, 23B, and 23C are provided corresponding to the first switch units 21A, 21B, and 21C, respectively. Each of the current detection units 23A, 23B, and 23C detects the value of a current flowing through the corresponding first switch unit 21A, 21B, and 21C. The current detection units 23A, 23B, and 23C are configured by, for example, a known current sensor.

[0035] The voltage detection unit 24 detects the voltage of the power path 13. When the second switch units 22A and 22B are in the on state, the voltage detection unit 24 detects the output voltage of the first power supply unit 11 or the output voltage of the second power supply unit 12. The voltage detection unit 24 is configured by, for example, a known voltage detection circuit.

[0036] Signals indicating the detection results of current detection units 23A, 23B, and 23C are input to control unit 30. A signal indicating the detection result of voltage detection unit 24 is input to control unit 30. Control unit 30 controls first switch units 21A, 21B, and 21C and second switch units 22A and 22B.

[0037] The current interruption device 20 has an electrical junction box 40. The electrical junction box 40 is provided between the first power supply unit 11 and the second power supply unit 12. The electrical junction box 40 is provided between the first power supply unit 11 and the plurality of loads 15. The electrical junction box 40 is provided between the second power supply unit 12 and the plurality of loads 15. The electrical junction box 40 is electrically connected to the first power supply unit 11, the second power supply unit 12, and each of the loads 15. The electrical junction box 40 houses first switch units 21A, 21B, and 21C, second switch units 22A and 22B, current detection units 23A, 23B, and 23C, a voltage detection unit 24, and a control unit 30.

[0038] 1-2. Operation of the current interruption device 20 The control unit 30 controls the first switch units 21A, 21B, and 21C and the second switch units 22A and 22B to the on state, for example, to supply power from the first power supply unit 11 and the second power supply unit 12 to each load 15.

[0039] For example, when the control unit 30 determines that a ground fault has occurred in the first power supply unit 11, the control unit 30 switches the second switch unit 22A to the OFF state, so that the second power supply unit 12 continues to supply power to each load 15.

[0040] For example, when the control unit 30 determines that a ground fault has occurred in the second power supply unit 12, the control unit 30 switches the second switch unit 22B to the OFF state, so that the first power supply unit 11 continues to supply power to each load 15.

[0041] The control unit 30 switches the first switch unit 21A to the OFF state when the value of the current flowing through the first switch unit 21A exceeds the overcurrent threshold. The control unit 30 switches the first switch unit 21B to the OFF state when the value of the current flowing through the first switch unit 21B exceeds the overcurrent threshold. The control unit 30 switches the first switch unit 21C to the OFF state when the value of the current flowing through the first switch unit 21C exceeds the overcurrent threshold. The control unit 30 sets the overcurrent threshold based on the voltage of the power path 13. In other words, the control unit 30 sets the overcurrent threshold based on the output voltage of the first power supply unit 11 or the second power supply unit 12.

[0042] Specifically, the control unit 30 includes overcurrent detection circuits 31A, 31B, and 31C and a threshold setting circuit 32. The overcurrent detection circuits 31A, 31B, and 31C and the threshold setting circuit 32 are configured by hardware circuits.

[0043] The overcurrent detection circuits 31A, 31B, and 31C are provided corresponding to the first switch units 21A, 21B, and 21C, respectively. Each overcurrent detection circuit 31A, 31B, and 31C determines whether the value of the current flowing through the corresponding first switch unit 21A, 21B, and 21C exceeds the overcurrent threshold. Each overcurrent detection circuit 31A, 31B, and 31C outputs an ON signal to the corresponding first switch unit 21A, 21B, and 21C when the value of the current flowing through the corresponding first switch unit 21A, 21B, and 21C does not exceed the overcurrent threshold. Each first switch unit 21A, 21B, and 21C is maintained in an ON state while the ON signal is being output from the corresponding overcurrent detection circuit 31A, 31B, and 31C. When each of the overcurrent detection circuits 31A, 31B, and 31C determines that the value of the current flowing through the corresponding first switch unit 21A, 21B, and 21C exceeds the overcurrent threshold, it outputs an OFF signal to the corresponding first switch unit 21A, 21B, and 21C. When the OFF signal is output from the corresponding overcurrent detection circuit 31A, 31B, and 31C, the first switch unit 21A, 21B, and 21C switches to the OFF state.

[0044] A signal indicating the detection result by the voltage detection unit 24 is input to the threshold setting circuit 32. The threshold setting circuit 32 sets an overcurrent threshold to be input to each overcurrent detection circuit 31A, 31B, 31C based on the voltage detected by the voltage detection unit 24. When the voltage of the power path 13 is equal to or lower than the threshold voltage Vth, the threshold setting circuit 32 sets the overcurrent threshold to a smaller value than when the voltage of the power path 13 is greater than the threshold voltage Vth. For example, when the voltage of the power path 13 exceeds the threshold voltage Vth, the threshold setting circuit 32 sets a first threshold Ith1 as the overcurrent threshold, and when the voltage of the power path 13 is equal to or lower than the threshold voltage Vth, the threshold setting circuit 32 sets a second threshold Ith2, which is smaller than the first threshold Ith1, as the overcurrent threshold. The threshold voltage Vth is, for example, a value greater than the minimum voltage VL at which each load 15 can operate.

[0045] For example, Figure 2 shows a graph illustrating the voltage change in the power path 13 and the change in the current value flowing through the first switch unit 21A when a layer short occurs in the load 15A and the first switch unit 21A switches to the OFF state. At timing T0, the voltage of the power path 13 is normal and exceeds the threshold voltage Vth. The threshold setting circuit 32 sets the first threshold Ith1 as the overcurrent threshold. The current value flowing through the first switch unit 21A is equal to or less than the first threshold Ith1. Therefore, the first switch unit 21A is in the ON state.

[0046] Then, at timing T1, when a layer short occurs in load 15A, the voltage of power path 13 drops, and the value of the current flowing through first switch unit 21A gradually increases. Then, at timing T2, when the voltage of power path 13 falls below threshold voltage Vth, threshold setting circuit 32 sets second threshold value Ith2 as the overcurrent threshold. Then, at timing T3, when the value of the current flowing through first switch unit 21A exceeds second threshold value Ith2, overcurrent detection circuit 31A outputs an OFF signal. As a result, first switch unit 21A switches to the OFF state, and the current flowing through first switch unit 21A is cut off. This causes the voltage of power path 13 to return to a state exceeding threshold voltage Vth.

[0047] 1-3. Effect Even if a ground fault does not occur, a voltage drop in the power path 13 occurs when some of the loads 15 experience a layer short circuit. However, the voltage drop is smaller in the case of a layer short circuit than in the case of a ground fault. Therefore, to detect a layer short circuit, the overcurrent threshold must be set to a small value. However, setting the overcurrent threshold to a small value increases the likelihood of erroneous determination. Therefore, the current interruption device 20 sets the overcurrent threshold to a small value when the voltage of the power path 13 is equal to or lower than the threshold voltage Vth. With this configuration, when the voltage of the power path 13 exceeds the threshold voltage Vth, a large value is set as the overcurrent threshold, making erroneous determination less likely. Furthermore, even if a layer short circuit occurs, it can be considered negligible because the voltage of the power path 13 exceeds the threshold voltage Vth. On the other hand, when the voltage of the power path 13 falls below the threshold voltage Vth, the current interruption device 20 sets the overcurrent threshold to a small value. This makes it easier to interrupt the current to the load 15 causing the voltage drop. As a result, if the current to the load 15 that is causing the voltage drop is cut off, the voltage of the power path 13 is likely to return to a state where it is greater than the threshold voltage Vth.

[0048] The current interruption device 20 sets the overcurrent threshold to a small value before the voltage of the power path 13 falls below the minimum voltage VL at which each load 15 can operate. Therefore, the current to the load 15 that is causing the voltage drop is likely to be interrupted before the voltage of the power path 13 falls below the minimum voltage at which each load 15 can operate. Therefore, the voltage of the power path 13 is unlikely to fall below the minimum voltage VL at which each load 15 can operate.

[0049] By using the overcurrent detection circuits 31A, 31B, and 31C, the current interruption device 20 can quickly perform operations from detecting an overcurrent to switching the first switch units 21A, 21B, and 21C to the OFF state.

[0050] By using the threshold setting circuit 32 , the current interruption device 20 can quickly perform the operation of setting the overcurrent threshold based on the voltage of the power line 13 .

[0051] 2. Second Embodiment In the second embodiment, a configuration will be described in which an overcurrent threshold is set based on the temperatures of the first switch units 21A, 21B, and 21C. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0052] 2-1. Configuration of the in-vehicle system 201 The in-vehicle system 201 of the second embodiment shown in Fig. 3 includes a current interruption device 220 instead of the current interruption device 20 described in the first embodiment. In other respects, the in-vehicle system 201 is common to the in-vehicle system 1 described in the first embodiment.

[0053] The current interruption device 220 has first switch units 21A, 21B, and 21C, second switch units 22A and 22B, current detection units 23A, 23B, and 23C, temperature detection units 25A, 25B, and 25C, a control unit 230, and an electrical connection box 40.

[0054] The temperature detection units 25A, 25B, and 25C are provided corresponding to the first switch units 21A, 21B, and 21C, respectively. Each of the temperature detection units 25A, 25B, and 25C detects the temperature of the corresponding first switch unit 21A, 21B, and 21C. The temperature detection units 25A, 25B, and 25C are configured by known temperature sensors such as thermistors.

[0055] Signals indicating the detection results of current detection units 23A, 23B, and 23C are input to control unit 230. Signals indicating the detection results of temperature detection units 25A, 25B, and 25C are input to control unit 230. Control unit 230 controls first switch units 21A, 21B, and 21C and second switch units 22A and 22B.

[0056] The electrical connection box 40 houses the first switch units 21A, 21B, and 21C, the second switch units 22A and 22B, the current detection units 23A, 23B, and 23C, the temperature detection units 25A, 25B, and 25C, and the control unit 230.

[0057] 2-2. Operation of the current interruption device 220 The control unit 230 sets an overcurrent threshold value used to determine whether or not to switch each of the first switch units 21A, 21B, and 21C to the OFF state, based on the temperatures of the first switch units 21A, 21B, and 21C.

[0058] Specifically, the control unit 230 includes overcurrent detection circuits 31A, 31B, and 31C and threshold setting circuits 232A, 232B, and 232C. The overcurrent detection circuits 31A, 31B, and 31C and the threshold setting circuits 232A, 232B, and 232C are configured by hardware circuits.

[0059] The threshold setting circuits 232A, 232B, and 232C are provided corresponding to the first switch units 21A, 21B, and 21C, respectively. Each threshold setting circuit 232A, 232B, and 232C sets an overcurrent threshold used to determine whether or not to switch the corresponding first switch unit 21A, 21B, or 21C to the OFF state.

[0060] Specifically, a signal indicating the detection result by the temperature detection unit 25A is input to the threshold setting circuit 232A. The threshold setting circuit 232A sets an overcurrent threshold to be input to the overcurrent detection circuit 31A based on the temperature detected by the temperature detection unit 25A. When the temperature of the first switch unit 21A exceeds the threshold temperature, the threshold setting circuit 232A sets the overcurrent threshold to a smaller value than when the temperature of the first switch unit 21A is equal to or lower than the threshold temperature. For example, when the temperature of the first switch unit 21A is equal to or lower than the threshold temperature, the threshold setting circuit 232A sets a first threshold as the overcurrent threshold, and when the temperature of the first switch unit 21A exceeds the threshold temperature, the threshold setting circuit 232A sets a second threshold lower than the first threshold as the overcurrent threshold.

[0061] Similarly, threshold setting circuit 232B sets an overcurrent threshold to be input to overcurrent detection circuit 31B based on the temperature detected by temperature detection unit 25B. Threshold setting circuit 232C sets an overcurrent threshold to be input to overcurrent detection circuit 31C based on the temperature detected by temperature detection unit 25C. Threshold setting circuits 232A, 232B, and 232C input the set overcurrent thresholds to their corresponding overcurrent detection circuits 31A, 31B, and 31C.

[0062] Each overcurrent detection circuit 31A, 31B, 31C switches the corresponding first switch unit 21A, 21B, 21C to the off state when the current value flowing through the corresponding first switch unit 21A, 21B, 21C exceeds the overcurrent threshold.

[0063] 2-3. Effects When the temperatures of the first switches 21A, 21B, and 21C are equal to or lower than the threshold temperature, the current interruption device 220 has a high overcurrent threshold, which makes it easy to prevent erroneous interruption of the first switches 21A, 21B, and 21C. On the other hand, when the temperatures of the first switches 21A, 21B, and 21C exceed the threshold temperature, the current interruption device 220 sets a small overcurrent threshold used to determine whether to switch the first switches 21A, 21B, and 21C that have exceeded the threshold temperature to the off state. This makes it easier for the first switches 21A, 21B, and 21C to be interrupted. As a result, if the first switches 21A, 21B, and 21C are interrupted, the temperature rise of the first switches 21A, 21B, and 21C due to overcurrent is suppressed.

[0064] By using the threshold setting circuits 232A, 232B, and 232C, the current interruption device 220 can quickly perform the operation of setting the overcurrent threshold based on the temperatures of the first switch units 21A, 21B, and 21C.

[0065] 3. Third Embodiment In the third embodiment, a configuration will be described in which an overcurrent threshold is set based on whether the vehicle is in a driving state or a parked state. In the third embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0066] 4 includes a current interruption device 320 instead of the current interruption device 20 described in the first embodiment. In other respects, the in-vehicle system 301 is common to the in-vehicle system 1 described in the first embodiment.

[0067] The current interruption device 320 includes first switch units 21A, 21B, and 21C, second switch units 22A and 22B, current detection units 23A, 23B, and 23C, a control unit 330, and an electric junction box 40.

[0068] Signals indicating the detection results of the current detection units 23A, 23B, and 23C are input to the control unit 330. The control unit 330 controls the first switch units 21A, 21B, and 21C and the second switch units 22A and 22B.

[0069] The electrical connection box 40 accommodates the first switches 21A, 21B, and 21C, the second switches 22A and 22B, the current detectors 23A, 23B, and 23C, and the controller 330.

[0070] 3-2. Operation of Current Interrupter Device 320 The control unit 330 sets the overcurrent threshold based on whether the vehicle is in a driving state or a parked state. Specifically, the control unit 330 includes overcurrent detection circuits 31A, 31B, and 31C, a threshold setting circuit 332, and a state determination unit 333. The overcurrent detection circuits 31A, 31B, and 31C and the threshold setting circuit 332 are configured as hardware circuits. The state determination unit 333 is configured to include a microcomputer.

[0071] The state determination unit 333 determines whether the vehicle is in a running state or a parked state. A start signal indicating the on / off state of the vehicle's start switch is input to the state determination unit 333 from an external device. The start switch is, for example, an ignition switch or a power switch. For example, the state determination unit 333 determines that the vehicle is in a running state when the start switch is in an on state, and determines that the vehicle is in a parked state when the start switch is in an off state. The state determination unit 333 outputs the determination result to the threshold setting circuit 332.

[0072] When the vehicle is parked, the threshold setting circuit 332 sets the overcurrent threshold to a smaller value than when the vehicle is moving. For example, when the vehicle is moving, the threshold setting circuit 332 sets a first threshold as the overcurrent threshold, and when the vehicle is parked, the threshold setting circuit 332 sets a second threshold that is smaller than the first threshold as the overcurrent threshold. The threshold setting circuit 332 inputs the set overcurrent threshold to each of the overcurrent detection circuits 31A, 31B, and 31C.

[0073] 3-3. Effects When the vehicle is running, the current interruption device 320 has a large overcurrent threshold, which makes it easier to prevent erroneous interruption of the first switches 21A, 21B, and 21C. On the other hand, when the vehicle is parked, the current interruption device 320 sets the overcurrent threshold to a small value. This makes it easier for the first switches 21A, 21B, and 21C to be interrupted, making it easier to maintain the voltage of the power path 13 at or above the threshold voltage.

[0074] <Other Embodiments> The present disclosure is not limited to the embodiments described above and in the drawings. For example, any combination of features of the above-described or below-described embodiments is possible within a range that does not contradict. Furthermore, any feature of the above-described or below-described embodiments may be omitted unless explicitly stated as essential. Furthermore, the above-described embodiments may be modified as follows.

[0075] In each of the above embodiments, the setting of the threshold and the detection of overcurrent are performed by a hardware circuit, but the setting of the threshold and the detection of overcurrent may be performed by software.

[0076] In each of the above embodiments, the overcurrent threshold has two stages, but it may have three or more stages.

[0077] In each of the above embodiments, a switch unit is provided in every branch path, but a switch unit may be provided only in some of the branch paths.

[0078] It should be noted that the embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is not limited to the embodiments disclosed herein, and is intended to include all modifications within the scope indicated by the claims or within the scope equivalent to the claims.

[0079] DESCRIPTION OF SYMBOLS 1...In-vehicle system 11...First power supply unit (power supply unit) 11A...Power supply source 11B...Voltage conversion unit 12...Second power supply unit (power supply unit) 12A...Battery 13...Power path 14...Branch path 14A...Branch path 14B...Branch path 14C...Branch path 15...Load 15A...Load 15B...Load 15C...Load 20...Current interruption device 21A...First switch unit (switch unit) 21B...First switch unit (switch unit) 21C...First switch unit (switch unit) 22A...Second switch unit 22B...Second switch unit 23A...Current detection unit 23B...Current detection unit 23C...Current detection unit 24...Voltage detection unit 25A...Temperature detection unit 25B...Temperature detection unit 25C...Temperature detection unit 30...Control unit 31A...Overcurrent detection circuit 31B...Overcurrent detection circuit 31C...Overcurrent detection circuit 32...Threshold value setting circuit 40...Electrical connection box 201...In-vehicle system 220...Current interruption device 230...Control unit 232A...Threshold value setting circuit 232B...Threshold value setting circuit 232C...Threshold value setting circuit 301...In-vehicle system 320...Current interruption device 330...Control unit 332...Threshold value setting circuit 333...State determination unit Ith1...First threshold value Ith2...Second threshold value VL...Minimum voltage at which the load can operate Vth...Threshold value voltage

Claims

1. A current interruption device included in an in-vehicle system having a power supply unit, a power path to which power is supplied from the power supply unit, a plurality of branch paths branching off from the power path, and a load connected to each of the branch paths, the current interruption device having: a switch unit provided in at least one of the branch paths; and a control unit that switches the switch unit to an off state when the value of current flowing through the switch unit exceeds an overcurrent threshold, the control unit setting the overcurrent threshold based on at least one of the voltage of the power path, the temperature of the switch unit, and the vehicle state.

2. The current interruption device according to claim 1, wherein the control unit sets the overcurrent threshold to a smaller value when the voltage of the power line is equal to or lower than a threshold voltage compared to when the voltage of the power line is higher than the threshold voltage.

3. The current interruption device according to claim 2, wherein the threshold voltage is greater than the lowest voltage at which each of the loads can operate.

4. The current interruption device according to claim 1, wherein the control unit sets the overcurrent threshold to a smaller value when the temperature of the switch unit exceeds a threshold temperature compared to when the temperature of the switch unit is equal to or lower than the threshold temperature.

5. The current interruption device according to claim 1, wherein the control unit sets the overcurrent threshold to a smaller value when the vehicle is parked compared to when the vehicle is moving.

6. A current interruption device according to any one of claims 1 to 5, further comprising a current detection unit that detects the value of a current flowing through the switch unit, wherein the control unit includes an overcurrent detection circuit that outputs an OFF signal when it is determined that the current value detected by the current detection unit exceeds the overcurrent threshold, and wherein the switch unit switches to an OFF state in response to the OFF signal being output from the overcurrent detection circuit.

7. The current interruption device according to claim 6, wherein the control unit sets the overcurrent threshold to a smaller value when the voltage of the power path is equal to or lower than a threshold voltage compared to when the voltage of the power path is higher than the threshold voltage, and further comprises a voltage detection unit that detects the voltage of the power path, and the control unit includes a threshold setting circuit that sets the overcurrent threshold based on the voltage detected by the voltage detection unit.

8. The current interruption device according to claim 6, wherein the control unit sets the overcurrent threshold to a smaller value when the temperature of the switch unit exceeds a threshold temperature compared to when the temperature of the switch unit is equal to or lower than the threshold temperature, and further comprises a temperature detection unit that detects the temperature of the switch unit, and the control unit includes a threshold setting circuit that sets the overcurrent threshold based on the temperature detected by the temperature detection unit.

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