In-vehicle cutoff device

Abstract

An in-vehicle cutoff device (10) is included in an in-vehicle system (100) comprising: a power supply unit (90); a plurality of loads (70); a main path (80) to which power from the power supply unit (90) is supplied; and a branch path (81) that branches from the main path (80) toward each load (70). The in-vehicle cutoff device (10) comprises a cutoff unit (11) provided in each branch path (81) and a first cutoff control unit (12) for controlling the cutoff unit (11). The cutoff unit (11) switches between a permissive state permitting current flow through the branch path (81) via the cutoff unit (11), and a cutoff state cutting off current flow through the branch path (81) via the cutoff unit (11). The first cutoff control unit (12) switches the cutoff unit (11) to the cutoff state when the current flowing through the cutoff unit (11) exceeds a first overcurrent threshold value (Ith1) and the voltage of the main path (80) is less than or equal to a voltage threshold value (Vth).

Description

Vehicle-mounted circuit breaker

[0001] The present disclosure relates to an on-vehicle shutoff device.

[0002] Patent Document 1 discloses a technology for an intelligent power device (IPD) that uses a microcomputer to control the supply of power from a power supply to a load, and Patent Document 2 discloses a technology for controlling the supply of power from a battery to a load using an integrated circuit (IC).

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

[0004] The IPD disclosed in Patent Document 1 cuts off the current to the load when the current flowing through the load exceeds a second threshold (i.e., when the load is completely short-circuited) and limits the current to the load when the current flowing through the load exceeds a first threshold (i.e., when the load is incompletely short-circuited). For example, if the first threshold is lowered to a value closer to the normal current value in order to more accurately detect an incomplete short-circuited load, there is a concern that even a slight fluctuation in the current to the load may increase the chance of falsely detecting an incomplete short-circuited load. In this case, there is a concern that the shorted load may cause the output voltage of the power supply to drop, preventing power from being supplied to other loads. Furthermore, Patent Document 2 is configured to cut off the current supply to the load when the voltage on the power line from the battery is equal to or lower than a voltage threshold. However, in a configuration in which multiple loads are connected in parallel to the power line, even if one of the loads experiences an overcurrent state and the voltage on the power line drops, it is impossible to determine which load experienced the overcurrent state.

[0005] The present disclosure has been made based on the above-mentioned circumstances, and aims to provide an on-board circuit breaker that can continue to supply power to other loads even if the voltage of the power supply unit drops due to a load failure.

[0006] The vehicle-mounted circuit breaking device disclosed herein is an vehicle-mounted circuit breaking device included in an vehicle system having a power supply unit, a plurality of loads, a main path to which power is supplied from the power supply unit, and branch paths branching off from the main path toward each of the loads, and comprises: a circuit breaking unit provided in each of the branch paths; and a first circuit breaking control unit that controls the circuit breaking unit, wherein the circuit breaking unit switches between an allowable state in which it allows current to flow to the branch path through it, and a circuit breaking state in which it blocks current from flowing to the branch path through it, and the first circuit breaking control unit switches the circuit breaking unit to the circuit breaking state when the current flowing through the circuit breaking unit exceeds a first overcurrent threshold and the voltage of the main path is equal to or lower than a voltage threshold.

[0007] According to the present disclosure, even if the voltage of the power supply unit drops due to a failure of a load, it is possible to continue supplying power to other loads.

[0008] FIG. 1 is a circuit diagram schematically showing the configuration of an in-vehicle system of embodiment 1. FIG. 2 is a time chart showing an example of the operation of a first shutoff control unit in the in-vehicle circuit breaker of embodiment 1. FIG. 3 is a time chart showing an example of the operation of a second shutoff control unit in the in-vehicle circuit breaker of embodiment 1. FIG. 4 is a circuit diagram schematically showing the configuration of an in-vehicle system of embodiment 2. FIG. 5 is a circuit diagram schematically showing the configuration of an in-vehicle system of embodiment 3. FIG. 6 is a circuit diagram schematically showing the configuration of an in-vehicle system of embodiment 4.

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

[0010] (1) An on-board circuit breaker included in an on-board system having a power supply unit, a plurality of loads, a main path to which power is supplied from the power supply unit, and branch paths branching off from the main path toward each of the loads, the on-board circuit breaker comprising: a circuit breaker provided in each of the branch paths; and a first circuit breaker control unit that controls the circuit breaker; the circuit breaker switches between an allowable state in which it allows current to flow to the branch path through the circuit breaker, and a circuit breaker state in which it blocks current from flowing to the branch path through the circuit breaker; and the first circuit breaker control unit switches the circuit breaker to the circuit breaker state when the current flowing through the circuit breaker exceeds a first overcurrent threshold and the voltage of the main path is equal to or lower than a voltage threshold.

[0011] (1) The on-board circuit breaker device switches the circuit breaker to a cut-off state when the current flowing through the circuit breaker exceeds the first overcurrent threshold and the voltage of the main path is below the voltage threshold, thereby preventing overcurrent from flowing into the faulty load and preventing the voltage of the main path from dropping too much, allowing power to continue to be supplied to other loads that are not faulty.

[0012] (2) The on-board circuit breaking device according to (1), further comprising a second circuit breaking control unit that controls the circuit breaking unit, wherein the second circuit breaking control unit switches the circuit breaking unit to the circuit breaking state when the current flowing through the circuit breaking unit exceeds a second overcurrent threshold.

[0013] The on-board circuit breaker (2) can cut off the current to the load even if low voltage cannot be detected in the main line.

[0014] (3) The vehicle-mounted circuit breaker according to (2), wherein the first overcurrent threshold is lower than the second overcurrent threshold.

[0015] (3) The on-board circuit breaker device can prevent the effects of the overcurrent from reaching the power supply unit, main path, circuit breaker, branch path, etc. by switching the circuit breaker to the cut-off state using the second circuit breaker control unit even in cases where the voltage in the main path does not become low and an overcurrent flows through the circuit breaker.

[0016] (4) An on-board cutoff device according to any one of (1) to (3), further comprising a third cutoff control unit that controls the cutoff unit, and the third cutoff control unit switches the cutoff unit to the cutoff state when the temperature of the cutoff unit exceeds a temperature threshold.

[0017] (4) The on-board circuit breaker device can switch the circuit breaker to the circuit breaker state taking into account temperature in addition to current and voltage, making it possible to more precisely control the switching of the circuit breaker to the circuit breaker state.

[0018] (5) The vehicle-mounted circuit breaker device according to any one of (1) to (4), wherein the first circuit breaker control unit sets the first overcurrent threshold based on a temperature of the circuit breaker unit.

[0019] The on-board circuit breaker device of (5) sets the first overcurrent threshold based on the temperature of the circuit breaker, which allows for more precise control of switching the circuit breaker to the circuit breaker state.

[0020] (6) The on-board circuit breaker device according to any one of (1) to (5), wherein at least one of the first overcurrent threshold and the voltage threshold is configurable.

[0021] The vehicle-mounted cutoff device (6) can be adapted to control the cutoff unit to switch to the cutoff state according to the specifications of the vehicle in which it is installed and the cutoff unit, etc., and is therefore highly versatile.

[0022] (7) The vehicle-mounted cutoff device according to any one of (1) to (6), wherein the first cutoff control unit includes: an overcurrent detection circuit that outputs an overcurrent signal when the current flowing through the cutoff unit exceeds the first overcurrent threshold; a low-voltage detection circuit that outputs a low-voltage signal when the voltage of the main path is equal to or lower than the voltage threshold; and a cutoff signal output circuit that outputs a cutoff signal when the overcurrent signal is output from the overcurrent detection circuit and the low-voltage signal is output from the low-voltage detection circuit; and the cutoff unit switches to the cutoff state when the cutoff signal is output from the cutoff signal output circuit, and further includes a control unit that stops operation of the cutoff signal output circuit.

[0023] (7) The on-board cutoff device can stop the operation of the cutoff signal output circuit using the control unit, so it can be operated flexibly, for example, by stopping the operation of the cutoff signal output circuit depending on the situation of the vehicle in which it is installed.

[0024] 1 is a system mounted on a vehicle. The vehicle system 100 includes a power supply unit 90, a plurality of loads 70, a main path 80, a plurality of branch paths 81, and an on-board circuit breaker 10. The vehicle system 100 supplies power from the power supply unit 90 to each of the loads 70.

[0025] The power supply unit 90 may be, for example, a lead-acid battery, a lithium-ion battery, a DC-DC converter, or the like. The power supply unit 90 supplies power to the main path 80.

[0026] Each load 70 is electrically connected to the main path 80 via a branch path 81. Each load 70 includes various electronic devices such as a power window, a light, a wiper deicer, a seat heater, a USB power supply, etc.

[0027] In the present disclosure, "electrically connected" preferably refers to a configuration in which the connection targets are connected in a mutually conductive state (a state in which a current can flow) so that the potentials of both connection targets are equal. However, this configuration is not limited to this. For example, "electrically connected" may also refer to a configuration in which the connection targets are connected in a state in which the two connection targets can be electrically connected with an electrical component interposed between them.

[0028] A power supply unit 90 is electrically connected to the main path 80. A plurality of branch paths 81 are provided between the main path 80 and each load 70. Specifically, one end of each branch path 81 is electrically connected to the main path 80. The other end of each branch path 81 is electrically connected to each load 70. In other words, each branch path 81 branches off from the main path 80 toward each load 70.

[0029] [Configuration of the Vehicle-Mounted Circuit Breaker] The vehicle-mounted circuit breaker 10 has a plurality of circuit breakers 11, a first circuit breaker control unit 12, and a second circuit breaker control unit 13. Note that, although the present embodiment discloses a configuration in which the vehicle-mounted circuit breaker 10 is provided for one load 70, a configuration in which the vehicle-mounted circuit breaker 10 is provided for each load 70 may also be adopted.

[0030] One interrupter 11 is provided for each branch path 81. For example, a switching element such as a field effect transistor (FET) is used for the interrupter 11. The interrupter 11 switches from a permissive state in which it allows current to flow through the branch path 81 to a blocking state in which it blocks current from flowing through the branch path 81.

[0031] The first shutoff control unit 12 controls the shutoff unit 11. The first shutoff control unit 12 includes a first overcurrent detection circuit 12A, a low-voltage detection circuit 12B, and a first shutoff signal output circuit 12C. The first overcurrent detection circuit 12A is configured, for example, as a comparator. For example, the first overcurrent detection circuit 12A is configured to receive a signal Cs corresponding to the current value flowing through the shutoff unit 11 from a current detection unit (not shown) electrically connected in series with the shutoff unit 11. The first overcurrent detection circuit 12A compares the magnitude of the signal Cs with the magnitude of a first overcurrent threshold Ith1. When the signal Cs exceeds the first overcurrent threshold Ith1, the first overcurrent detection circuit 12A outputs an overcurrent signal Oc1 indicating that the current flowing through the shutoff unit 11 is in an overcurrent state. The first overcurrent detection circuit 12A does not output the overcurrent signal Oc1 when the signal Cs is equal to or less than the first overcurrent threshold Ith1. For example, the first overcurrent threshold Ith1 is set to the maximum current value that can flow through the breaker 11.

[0032] The low-voltage detection circuit 12B is configured as, for example, a comparator. For example, the low-voltage detection circuit 12B is configured to receive a signal Es corresponding to the voltage value of the main path 80 from a voltage detection unit (not shown) provided in the main path 80. For example, the voltage detection unit is configured to output a signal Es corresponding to the potential difference between the main path 80 and a vehicle ground (not shown). The low-voltage detection circuit 12B compares the magnitude of the signal Es with the magnitude of a voltage threshold Vth. If the signal Es is equal to or less than the voltage threshold Vth, the low-voltage detection circuit 12B outputs a low-voltage signal Lv indicating that the voltage of the main path 80 is in a low-voltage state. If the signal Es exceeds the voltage threshold Vth, the low-voltage detection circuit 12B does not output the low-voltage signal Lv. For example, the voltage threshold Vth is set to a value slightly greater than the voltage value Vr (drive voltage of the load 70) required to operate the load 70 electrically connected to the main path 80 (see FIGS. 2 and 3 ). In other words, the voltage threshold Vth is a value that is greater than 0 V and greater than the drive voltage of the load 70. The voltage value Vr is the minimum level required to operate the load 70.

[0033] The first shutdown signal output circuit 12C receives an overcurrent signal Oc1 from the first overcurrent detection circuit 12A and a low voltage signal Lv from the low voltage detection circuit 12B. The first shutdown signal output circuit 12C is configured to output a shutdown signal Cut1 that switches the shutdown unit 11 to the shutdown state when the overcurrent signal Oc1 and the low voltage signal Lv are input. The first shutdown signal output circuit 12C may include, for example, a logic circuit. The first shutdown signal output circuit 12C does not output the shutdown signal Cut1 when only the overcurrent signal Oc1 or only the low voltage signal Lv is input, or when neither the overcurrent signal Oc1 nor the low voltage signal Lv is input.

[0034] The second shutoff control unit 13 controls the shutoff unit 11. The second shutoff control unit 13 includes a second overcurrent detection circuit 13A and a second shutoff signal output circuit 13B. The second overcurrent detection circuit 13A is configured to detect whether the current flowing through the shutoff unit 11 is in an overcurrent state. The second overcurrent detection circuit 13A is configured, for example, as a comparator. For example, the second overcurrent detection circuit 13A is configured to receive a signal Cs corresponding to the current value flowing through the shutoff unit 11 from a current detection unit (not shown) electrically connected in series with the shutoff unit 11. The second overcurrent detection circuit 13A compares the magnitude of the signal Cs with the magnitude of a second overcurrent threshold Ith2. When the signal Cs exceeds the second overcurrent threshold Ith2, the second overcurrent detection circuit 13A outputs an overcurrent signal Oc2 indicating that the current flowing through the shutoff unit 11 is in an overcurrent state. The second overcurrent detection circuit 13A does not output the overcurrent signal Oc2 when the signal Cs is equal to or less than the second overcurrent threshold Ith2. For example, the second overcurrent threshold Ith2 is set to a value greater than the maximum current that can flow through the circuit breaker 11 while the vehicle is running. In other words, the first overcurrent threshold Ith1 is set to a value lower than the second overcurrent threshold Ith2.

[0035] The second shutdown signal output circuit 13B receives the overcurrent signal Oc2 from the second overcurrent detection circuit 13A. When the overcurrent signal Oc2 is received, the second shutdown signal output circuit 13B outputs a shutdown signal Cut2 that switches the shutdown unit 11 to the shutdown state. The second shutdown signal output circuit 13B may include, for example, a logic circuit.

[0036] For example, when the start switch of the vehicle is in the on state and the cutoff signal Cut1 is not input from the first cutoff signal output circuit 12C and the cutoff signal Cut2 is not input from the second cutoff signal output circuit 13B, the cutoff unit 11 maintains the allowable state. When the cutoff signal Cut1 is input from the first cutoff signal output circuit 12C or the cutoff signal Cut2 is input from the second cutoff signal output circuit 13B, the cutoff unit 11 switches from the allowable state to the cutoff state.

[0037] [Example of Operation of the Vehicle Circuit Breaker] Next, an example of operation of the vehicle circuit breaker 10 will be described with reference to Figures 2 and 3. First, using Figure 2, the operation of the vehicle circuit breaker 10 when a minor ground fault occurs in the load 70 will be described. For example, a minor ground fault is a fault in which the potential of the main path 80 drops due to the load 70 in which the ground fault has occurred, and becomes higher than the potential of the ground section. In other words, the load 70 in which the minor ground fault has occurred has a resistance component of a predetermined magnitude, and the main path 80 and the ground section are electrically connected via this resistance component. Due to this resistance component, the potential of the main path 80 does not drop to the potential of the ground section, but drops to a value higher than the potential of the ground section by a predetermined amount.

[0038] When the start switch of the vehicle equipped with the in-vehicle system 100 is switched from an off state to an on state, each circuit breaker 11 is maintained in an open state (corresponding to the period from time T0 to time T1 in FIG. 2 ). As a result, power is supplied from the power supply unit 90 to each load 70 via the main path 80 and the branch path 81. At this time, a signal Es greater than the voltage threshold Vth is input to the low-voltage detection circuit 12B. Therefore, the low-voltage detection circuit 12B does not output a low-voltage signal Lv between time T0 and time T1. Furthermore, a signal Cs smaller than the first overcurrent threshold Ith1 is input to the first overcurrent detection circuit 12A. Therefore, the first overcurrent detection circuit 12A does not output an overcurrent signal Oc1 between time T0 and time T1. Furthermore, a signal Cs smaller than the first overcurrent threshold Ith1 is also input to the second overcurrent detection circuit 13A. Therefore, the second overcurrent detection circuit 13A does not output the overcurrent signal Oc2 between time T0 and time T1.

[0039] At time T1, a minor ground fault occurs in load 70. At this time, signal Cs begins to rise sharply. At the same time, signal Es begins to fall in a downward convex manner.

[0040] The signal Cs starts to rise and reaches the first overcurrent threshold Ith1 at time T2. After time T2, the signal Cs exceeds the first overcurrent threshold Ith1 and continues to rise, stopping at time T3. The signal Es continues to fall, forming a downward convex curve, even after times T2 and T3 have passed. The first overcurrent detection circuit 12A starts outputting the overcurrent signal Oc1 at time T2.

[0041] Then, signal Es becomes equal to or lower than voltage threshold Vth at time T4. At this time, low voltage detection circuit 12B starts outputting low voltage signal Lv at time T4. At time T4, signal Cs exceeds first overcurrent threshold Ith1, and signal Es becomes equal to or lower than voltage threshold Vth. Thus, at time T4, overcurrent signal Oc1 and low voltage signal Lv are input to first shutdown signal output circuit 12C. As a result, first shutdown signal output circuit 12C outputs shutdown signal Cut1 to cutoff unit 11 at time T4. Then, cutoff unit 11 switches from the permissive state to the shutdown state at time T4. After time T4, signal Cs drops sharply to 0. After time T4, signal Es rises sharply and stops rising when it reaches a predetermined value. In this way, the first cut-off control unit 12 switches the cut-off unit 11 from the permissive state to the cut-off state when the current flowing through the cut-off unit 11 exceeds the first overcurrent threshold Ith1 and the voltage of the main path 80 is below the voltage threshold Vth.

[0042] Next, referring to FIG. 3 , the operation of the vehicle circuit breaker 10 when a severe ground fault occurs in the load 70 will be described. For example, a severe ground fault is a fault in which the potential of the main path 80, which has dropped due to the load 70 experiencing a ground fault, becomes approximately the same as the potential of the ground section. In other words, when a severe ground fault occurs in the load 70, the main path 80 and the ground section are electrically connected without any resistance component. As a result, the potential of the main path 80 drops until it becomes approximately the same as the potential of the ground section. The current flowing through the circuit breaker 11 increases more rapidly when a severe ground fault occurs in the load 70 than when a mild ground fault occurs.

[0043] When the start switch of the vehicle equipped with the in-vehicle system 100 is switched from an off state to an on state, each breaker 11 is maintained in an allowable state (corresponding to the period from time T10 to time T11 in FIG. 3 ). As a result, power is supplied from the power supply unit 90 to each load 70 via the main path 80 and the branch path 81. At this time, a signal Es greater than the voltage threshold Vth is input to the low-voltage detection circuit 12B, and a signal Cs smaller than the first overcurrent threshold Ith1 is input to the first overcurrent detection circuit 12A and the second overcurrent detection circuit 13A.

[0044] At time T11, a severe ground fault occurs in load 70. At this time, signal Cs begins to rise sharply. At the same time, signal Es begins to fall in a downward convex manner.

[0045] The signal Cs starts to rise and exceeds the first overcurrent threshold Ith1 at time T12. After time T12, the signal Cs continues to rise beyond the first overcurrent threshold Ith1 and exceeds the second overcurrent threshold Ith2 at time T13. The first overcurrent detection circuit 12A starts to output the overcurrent signal Oc1 at time T12, and the second overcurrent detection circuit 13A starts to output the overcurrent signal Oc2 at time T13, which is later than time T12.

[0046] At time T13, the overcurrent signal Oc2 is input to the second shutdown signal output circuit 13B. As a result, the second shutdown signal output circuit 13B outputs the shutdown signal Cut2 to the shutdown unit 11. Then, at time T13, the shutdown unit 11 switches from the permissive state to the shutdown state. After time T13, the signal Cs drops sharply to 0. After time T13, the signal Es rises sharply and stops rising when it reaches a predetermined value. In this way, the second shutdown control unit 13 switches the shutdown unit 11 from the permissive state to the shutdown state when the current flowing through the shutdown unit 11 exceeds the second overcurrent threshold Ith2.

[0047] Next, the effects of this configuration will be illustrated. The vehicle-mounted circuit breaking device 10 is included in an in-vehicle system 100 that includes a power supply unit 90, multiple loads 70, a main path 80 to which power is supplied from the power supply unit 90, and branch paths 81 branching from the main path 80 toward each of the loads 70. The vehicle-mounted circuit breaking device 10 includes a circuit breaking unit 11 provided in each branch path 81 and a first circuit breaking control unit 12 that controls the circuit breaking unit 11. The circuit breaking unit 11 switches between a permissive state in which it allows current to flow to the branch path 81 via the circuit breaking unit 11 and a circuit breaking state in which it blocks current from flowing to the branch path 81 via the circuit breaking unit 11. The first circuit breaking control unit 12 switches the circuit breaking unit 11 to the circuit breaking state when the current flowing through the circuit breaking unit 11 exceeds a first overcurrent threshold Ith1 and the voltage of the main path 80 is equal to or lower than a voltage threshold Vth.

[0048] According to this configuration, when the current flowing through the interrupter 11 exceeds the first overcurrent threshold Ith1 and the voltage of the main path 80 is equal to or lower than the voltage threshold Vth, the interrupter 11 is switched to the interrupted state, thereby preventing overcurrent from flowing into the faulty load 70 and preventing the voltage of the main path 80 from dropping too much, thereby allowing power to continue to be supplied to other loads 70 that are not faulty.

[0049] The vehicle-mounted circuit breaker 10 includes a second circuit breaker control unit 13 that controls the circuit breaker 11. The second circuit breaker control unit 13 switches the circuit breaker 11 to a circuit breaker state when the current flowing through the circuit breaker 11 exceeds a second overcurrent threshold Ith2. With this configuration, the current to the load 70 can be cut off even when a low voltage in the main path 80 cannot be detected.

[0050] The first overcurrent threshold Ith1 is lower than the second overcurrent threshold Ith2. With this configuration, even if the voltage in the main path 80 does not become low and an overcurrent flows through the circuit breaker 11, the second circuit breaker control unit 13 can switch the circuit breaker 11 to the cut-off state, thereby preventing the overcurrent from affecting the power supply unit 90, the main path 80, the circuit breaker 11, the branch path 81, etc.

[0051] <Embodiment 2> The vehicle-mounted cutoff device 20 of embodiment 2 is different from embodiment 1 in that it includes a third cutoff control unit 14 instead of the second cutoff control unit 13, but is otherwise the same as embodiment 1. In embodiment 2, the same components as embodiment 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0052] The on-board shutoff device 20 provided in the on-board system 200 shown in FIG. 4 does not include a second shutoff control unit 13, but instead includes a third shutoff control unit 14. The third shutoff control unit 14 switches the shutoff unit 11 to a shutoff state when the temperature of the shutoff unit 11 exceeds a temperature threshold value Tth. The third shutoff control unit 14 includes a temperature detection circuit 14A and a third shutoff signal output circuit 14B. The temperature detection circuit 14A is configured to detect whether the temperature of the shutoff unit 11 is in an overheated state. The temperature detection circuit 14A is configured, for example, as a comparator. For example, the temperature detection circuit 14A is configured to receive a signal Ts corresponding to the temperature of the shutoff unit 11 from a temperature detection unit (not shown) provided near the shutoff unit 11. The temperature detection circuit 14A compares the magnitude of the signal Ts with the magnitude of the temperature threshold value Tth. When the signal Ts exceeds a temperature threshold value Tth, the temperature detection circuit 14A outputs an overheat signal Oh indicating that the temperature of the cutoff unit 11 is in an overheated state. When the signal Ts is equal to or lower than the temperature threshold value Tth, the temperature detection circuit 14A does not output the overheat signal Oh. For example, the temperature threshold value Tth is set to the maximum temperature value that the cutoff unit 11 can withstand.

[0053] The third shutdown signal output circuit 14B receives the overheat signal Oh from the temperature detection circuit 14A. When the overheat signal Oh is received, the third shutdown signal output circuit 14B outputs a shutdown signal Cut3 that switches the shutdown unit 11 to the shutdown state. The third shutdown signal output circuit 14B may include, for example, a logic circuit.

[0054] For example, when the start switch of the vehicle is in the on state, and the cutoff signal Cut1 is not input from the first cutoff signal output circuit 12C and the cutoff signal Cut3 is not input from the third cutoff signal output circuit 14B, the cutoff unit 11 maintains the allowable state. Then, when the cutoff signal Cut1 is input from the first cutoff signal output circuit 12C or the cutoff signal Cut3 is input from the third cutoff signal output circuit 14B, the cutoff unit 11 switches from the allowable state to the cutoff state.

[0055] The vehicle-mounted circuit breaker device 20 includes a third circuit breaker control unit 14 that controls the circuit breaker unit 11. The third circuit breaker control unit 14 switches the circuit breaker unit 11 to the circuit breaker state when the temperature of the circuit breaker unit 11 exceeds a temperature threshold value Tth. With this configuration, the circuit breaker unit 11 can be switched to the circuit breaker state taking into consideration the temperature in addition to the current and voltage, thereby enabling more precise control of switching the circuit breaker unit 11 to the circuit breaker state.

[0056] <Embodiment 3> An on-board circuit breaker 30 of embodiment 3 differs from embodiments 1 and 2 in that it includes a temperature detection unit 15 that outputs a signal Ts corresponding to the temperature of the circuit breaker 11, and a threshold change unit 12D that inputs a first overcurrent threshold Ith1 changed by a first circuit breaker control unit 112 in response to the signal Ts to a first overcurrent detection circuit 12A. In embodiment 3, the same components as those of embodiment 1 or 2 are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0057] The in-vehicle circuit breaking device 30 provided in the in-vehicle system 300 shown in FIG. 5 includes a temperature detection unit 15 instead of the second circuit breaking control unit 13 and the third circuit breaking control unit 14. The first circuit breaking control unit 112 provided in the in-vehicle circuit breaking device 30 further includes a threshold value changing unit 12D. The first circuit breaking control unit 112 sets a first overcurrent threshold value Ith1 based on the temperature of the circuit breaking unit 11. The temperature detection unit 15 is provided near the circuit breaking unit 11. The temperature detection unit 15 may be configured as, for example, a thermistor or a resistance temperature detector. The temperature detection unit 15 outputs a signal Ts corresponding to the temperature of the circuit breaking unit 11.

[0058] The threshold value changing unit 12D is configured, for example, by an MCU (Micro Controller Unit). For example, the threshold value changing unit 12D stores a plurality of first overcurrent threshold values ​​Ith1 corresponding to the input signal Ts as table data. The threshold value changing unit 12D is configured to output the first overcurrent threshold value Ith1 corresponding to the input signal Ts to the first overcurrent detection circuit 12A. The threshold value changing unit 12D may be configured to calculate the first overcurrent threshold value Ith1 from the input signal Ts using an arithmetic expression such as a function. For example, the first overcurrent threshold value Ith1 may be set to decrease as the signal Ts increases (i.e., to be inversely proportional).

[0059] The first overcurrent detection circuit 12A compares the magnitude of the signal Cs with the magnitude of the first overcurrent threshold Ith1 input from the threshold change unit 12D, and when the signal Cs exceeds the first overcurrent threshold Ith1, outputs an overcurrent signal Oc1 indicating that the current flowing through the circuit breaker 11 is in an overcurrent state. In this way, the first shutoff control unit 112 sets the first overcurrent threshold Ith1 based on the signal Ts indicating the temperature of the circuit breaker 11. With this configuration, the first overcurrent threshold Ith1 is set based on the temperature of the circuit breaker 11, enabling more precise control of switching the circuit breaker 11 to the shutoff state.

[0060] Fourth Embodiment The on-board circuit breaker 40 of the fourth embodiment differs from the first embodiment in that it outputs the first overcurrent threshold Ith1 and the voltage threshold Vth that have been changed to desired values, and includes a control unit 16 that controls the operation of the first circuit breaker signal output circuit 12C. In the fourth embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0061] The on-board shutoff device 40 provided in the on-board system 400 shown in Fig. 6 further includes a control unit 16. The control unit 16 is configured, for example, by an MCU or the like. For example, the control unit 16 is configured to be able to operate in response to an instruction signal Is from an external ECU (not shown).

[0062] For example, the control unit 16 may be configured to output a first overcurrent threshold Ith1 corresponding to the instruction signal Is to the first overcurrent detection circuit 12A and a voltage threshold Vth corresponding to the instruction signal Is to the low-voltage detection circuit 12B. Alternatively, the control unit 16 may be configured to output the instruction signal Is directly to the first overcurrent detection circuit 12A as the first overcurrent threshold Ith1, or to output the instruction signal Is directly to the low-voltage detection circuit 12B as the voltage threshold Vth. In other words, the first overcurrent threshold Ith1 and the voltage threshold Vth can be set or changed in response to the instruction signal Is from the external ECU. This configuration allows the control of switching the circuit breaker 11 to the cut-off state to be adapted to the specifications of the vehicle in which the circuit breaker 11 is installed and the specifications of the circuit breaker 11, etc., and is therefore highly versatile.

[0063] For example, the control unit 16 is configured to stop outputting the first overcurrent threshold Ith1 to the first overcurrent detection circuit 12A in response to the instruction signal Is. The control unit 16 is also configured to stop outputting the voltage threshold Vth to the low-voltage detection circuit 12B in response to the instruction signal Is. That is, the control unit 16 included in the in-vehicle circuit breaker 40 can perform at least one of the following operations: outputting the first overcurrent threshold Ith1 to the first overcurrent detection circuit 12A and outputting the voltage threshold Vth to the low-voltage detection circuit 12B. This configuration allows the control for switching the breaker 11 to the cutoff state to be varied depending on the state of the vehicle in which the breaker is installed, making it easy to perform precise control tailored to the state of the vehicle.

[0064] The control unit 16 is also configured to output a drive signal Ds or a stop signal Ss to the first shutdown signal output circuit 12C in response to an instruction signal Is from an external ECU. For example, when the drive signal Ds is input, the first shutdown signal output circuit 12C outputs a shutdown signal Cut1 when the overcurrent signal Oc1 and the low voltage signal Lv are input, but does not output the shutdown signal Cut1 when only the overcurrent signal Oc1 or only the low voltage signal Lv is input, or when neither the overcurrent signal Oc1 nor the low voltage signal Lv is input. When the stop signal Ss is input, the first shutdown signal output circuit 12C does not output the shutdown signal Cut1 regardless of whether the overcurrent signal Oc1 or the low voltage signal Lv is input. In other words, the control unit 16 stops the operation of the first shutdown signal output circuit 12C by outputting the stop signal Ss. The cutoff unit 11 switches from the permitting state to the cutoff state when the cutoff signal Cut1 is output from the first cutoff signal output circuit 12C.

[0065] The first shutoff control unit 12 includes a first overcurrent detection circuit 12A that outputs an overcurrent signal Oc1 when the current flowing through the shutoff unit 11 exceeds a first overcurrent threshold Ith1, a low-voltage detection circuit 12B that outputs a low-voltage signal Lv when the voltage of the main path 80 is equal to or lower than a voltage threshold Vth, and a first shutoff signal output circuit 12C that outputs a shutoff signal Cut1 when the overcurrent signal Oc1 is output from the first overcurrent detection circuit 12A and the low-voltage detection circuit 12B outputs the low-voltage signal Lv. The shutoff unit 11 switches to a shutoff state when the shutoff signal Cut1 is output from the first shutoff signal output circuit 12C. The on-board shutoff device 40 further includes a control unit 16 that stops the operation of the first shutoff signal output circuit 12C. According to this configuration, the operation of the first shutdown signal output circuit 12C can be stopped by the control unit 16, which allows for flexible operation, for example, by stopping the operation of the first shutdown signal output circuit 12C depending on the situation of the vehicle in which it is installed.

[0066] <Other Embodiments> 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, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0067] Unlike the above-described embodiments, a mechanical switch, a pyrotechnic circuit breaker, or the like may be used as the circuit breaker.

[0068] Unlike the above-described embodiments, the second cutoff control unit and the cutoff unit may be integrated into one component, for example, an IPD.

[0069] Unlike embodiment 4, the control unit may be configured to output only the first overcurrent threshold value corresponding to the instruction signal to the first overcurrent detection circuit, or may be configured to output only the voltage threshold value corresponding to the instruction signal to the low voltage detection circuit.

[0070] Unlike the fourth embodiment, the control unit may be configured to stop the operation of the second shutdown signal output circuit, or the control unit may be configured to output the second overcurrent threshold value corresponding to the instruction signal to the second overcurrent detection circuit.

[0071] Unlike the first embodiment, the first overcurrent threshold may be the same as or greater than the second overcurrent threshold.

[0072] The third shutoff control unit of the second embodiment or the temperature detection unit of the third embodiment may be added to the first or fourth embodiment.

[0073] 10, 20, 30, 40: Vehicle circuit breaker 11: Breaker section 12, 112: First breaker control section 12A: First overcurrent detection circuit (overcurrent detection circuit) 12B: Low voltage detection circuit 12C: First breaker signal output circuit (breaker signal output circuit) 12D: Threshold value changing section 13: Second breaker control section 13A: Second overcurrent detection circuit 13B: Second breaker signal output circuit 14: Third breaker control section 14A: Temperature detection circuit 14B: Third breaker signal output circuit 15: Temperature detection section 16: Control section 70: Load 80: Main path 81: Branch path 90: Power supply section 100, 200, 300, 400: Vehicle system Cs, Es, Ts: Signal Cut1, Cut2, Cut3: Breakdown signal Ds: Drive signal Is: Indication signal Ith1: First overcurrent threshold Ith2: Second overcurrent threshold Lv: Low voltage signal Oc1, Oc2: Overcurrent signal Oh: Overheat signal Ss: Stop signal Tth: Temperature threshold Vr: Voltage value (load drive voltage) Vth: Voltage threshold

Claims

1. An in-vehicle cutoff device included in an in-vehicle system comprising a power supply unit, a plurality of loads, a main path through which power from the power supply unit is supplied, and a branch path that branches from the main path toward each of the loads, the in-vehicle cutoff device comprising: a cutoff unit provided in each of the branch paths; and a first cutoff control unit that controls the cutoff unit, wherein the cutoff unit switches between a permitted state in which current is permitted to flow through the branch path via itself and a cutoff state in which current flow through the branch path via itself is blocked, and the first cutoff control unit switches the cutoff unit to the cutoff state when the current flowing through the cutoff unit exceeds a first overcurrent threshold value and the voltage of the main path is equal to or lower than a voltage threshold value.

2. The in-vehicle cutoff device according to claim 1, further comprising a second cutoff control unit that controls the cutoff unit, wherein the second cutoff control unit switches the cutoff unit to the cutoff state when the current flowing through the cutoff unit exceeds a second overcurrent threshold value.

3. The in-vehicle cutoff device according to claim 2, wherein the first overcurrent threshold value is lower than the second overcurrent threshold value.

4. The in-vehicle cutoff device according to claim 1, further comprising a third cutoff control unit that controls the cutoff unit, wherein the third cutoff control unit switches the cutoff unit to the cutoff state when the temperature of the cutoff unit exceeds a temperature threshold value.

5. The in-vehicle cutoff device according to claim 1, wherein the first cutoff control unit sets the first overcurrent threshold value based on the temperature of the cutoff unit.

6. The in-vehicle cutoff device according to claim 1, wherein at least one of the first overcurrent threshold value and the voltage threshold value is changeable.

7. The first cutoff control unit includes an overcurrent detection circuit that outputs an overcurrent signal when the current flowing through the cutoff unit exceeds the first overcurrent threshold value, a low-voltage detection circuit that outputs a low-voltage signal when the voltage of the main path is equal to or lower than the voltage threshold value, and a cutoff signal output circuit that outputs a cutoff signal when the overcurrent signal is output from the overcurrent detection circuit and the low-voltage signal is output from the low-voltage detection circuit, the cutoff unit switches to the cutoff state when the cutoff signal is output from the cutoff signal output circuit, and further includes a control unit that stops the operation of the cutoff signal output circuit.

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