Vehicle-mounted shutoff device
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Filing Date
- 2023-09-25
- Publication Date
- 2026-06-11
Abstract
Description
Vehicle-mounted circuit breaker
[0001] The present disclosure relates to an on-vehicle shutoff device.
[0002] Patent Literature 1 discloses a power supply system that prevents current from passing from a sub-power source to a main power source when power from the main power source is interrupted. This power supply system determines whether power from the main power source has been interrupted, for example, based on the current flowing to the main power source.
[0003] Japanese Patent Application Laid-Open No. 2020-182318
[0004] In the configuration of Patent Document 1, even when an attempt is made to supply power from the sub-power source to the main power source, the system may determine that there has been an interruption in power from the main power source, and the power supply to the main power source may be cut off. Therefore, when power is to be supplied from the sub-power source to the main power source, it may be possible to disable the cutoff function and allow the power supply to the main power source. However, disabling the cutoff function creates the problem of not being able to cut off the power even if an overcurrent flows.
[0005] The present disclosure aims to provide a technology that makes it easy to appropriately interrupt current.
[0006] The vehicle-mounted circuit breaking device disclosed herein is an vehicle-mounted circuit breaking device included in an vehicle system having: a first power supply unit; a second power supply unit; a conductive path provided between the first power supply unit and the second power supply unit; and a load electrically connected to the conductive path, the vehicle-mounted circuit breaking device having: a first circuit breaking unit provided between the first power supply unit and the conductive path; and a control unit that controls the first circuit breaking unit, wherein the first circuit breaking unit switches between a first permissive state that allows current to flow from the second power supply unit side to the first power supply unit side and a first blocked state that blocks current from flowing from the second power supply unit side to the first power supply unit side, and the control unit performs circuit breaking control to switch the first circuit breaking unit to the first blocked state when the vehicle is in a first state based on a current exceeding a first threshold value flowing from the second power supply unit side to the first power supply unit side, and when the vehicle is in a second state based on a current exceeding a second threshold value flowing from the second power supply unit side to the first power supply unit side.
[0007] The technology disclosed herein makes it easy to appropriately interrupt current.
[0008] FIG. 1 is a schematic diagram illustrating an in-vehicle system including an in-vehicle circuit breaker according to a first embodiment. FIG. 2 is an explanatory diagram illustrating the operation of the in-vehicle system according to the first embodiment during precharging. FIG. 3 is an explanatory diagram illustrating the operation of the in-vehicle system according to the first embodiment while the vehicle is traveling. FIG. 4 is an explanatory diagram illustrating a state in which a ground fault occurs in the second conduction path in the state shown in FIG. 2. FIG. 5 is an explanatory diagram illustrating a state in which the first circuit breaker has switched to the first circuit breaker state from the state shown in FIG. 4. FIG. 6 is an explanatory diagram illustrating a state in which a ground fault occurs in the second conduction path in the state shown in FIG. 3. FIG. 7 is an explanatory diagram illustrating a state in which the first circuit breaker has switched to the first circuit breaker state from the state shown in FIG. 6. FIG. 8 is a schematic diagram illustrating an in-vehicle system including an in-vehicle circuit breaker according to a second embodiment. FIG. 9 is an explanatory diagram illustrating the operation of the in-vehicle system according to the second embodiment during precharging. FIG. 10 is an explanatory diagram illustrating the operation of the in-vehicle system according to the second embodiment while the vehicle is traveling. FIG. 11 is an explanatory diagram illustrating a state in which a ground fault occurs in the second conduction path in the state shown in FIG. 9. Fig. 12 is an explanatory diagram showing a state in which the first interrupting unit has switched to the first interrupting state from the state shown in Fig. 11. Fig. 13 is an explanatory diagram showing a state in which a ground fault occurs in the second conductive path in the state shown in Fig. 10. Fig. 14 is an explanatory diagram showing a state in which the first interrupting unit has switched to the first interrupting state from the state shown in Fig. 13.
[0009] [Description of Embodiments of the Present Disclosure] In the following, embodiments according to the present disclosure are listed and exemplified.
[0010] [1] An on-board circuit breaker included in an on-board system having: a first power supply unit; a second power supply unit; a conductive path provided between the first power supply unit and the second power supply unit; and a load electrically connected to the conductive path, the on-board circuit breaker having: a first circuit breaker provided between the first power supply unit and the conductive path; and a control unit that controls the first circuit breaker, wherein the first circuit breaker switches between a first permissive state that allows current to flow from the second power supply unit side to the first power supply unit side and a first blocked state that blocks current from flowing from the second power supply unit side to the first power supply unit side, and the control unit performs circuit breaker control to switch the first circuit breaker to the first blocked state when the vehicle is in a first state based on a current that exceeds a first threshold value flowing from the second power supply unit side to the first power supply unit side, and when the vehicle is in a second state based on a current that exceeds a second threshold value that is larger than the first threshold value flowing from the second power supply unit side to the first power supply unit side.
[0011] When the vehicle is in a first state, the vehicle circuit breaker switches the first circuit breaker to the first circuit breaker state based on a current exceeding a first threshold value flowing from the second power supply unit to the first power supply unit. When the vehicle is in a second state, the vehicle circuit breaker switches the first circuit breaker to the first circuit breaker state based on a current exceeding a second threshold value that is greater than the first threshold value flowing from the second power supply unit to the first power supply unit. In other words, the vehicle circuit breaker can change the threshold value for switching the first circuit breaker to the first circuit breaker state based on the state of the vehicle, and can therefore appropriately interrupt current based on the state of the vehicle.
[0012] [2] The on-board circuit breaking device described in [1] has a second circuit breaking unit provided between the second power supply unit and the conductive path, the second circuit breaking unit is controlled by the control unit and switches between a second permissive state that allows current to flow from the first power supply unit side to the second power supply unit side and a second circuit breaking state that blocks current from flowing from the first power supply unit side to the second power supply unit side, and the control unit performs the circuit breaking control when the first circuit breaking unit is in the first permissive state and the second circuit breaking unit is in the second permissive state.
[0013] The vehicle-mounted circuit breaker performs the circuit breaker control when the first circuit breaker is in the first permissive state and the second circuit breaker is in the second permissive state. Therefore, even when the first circuit breaker is switched to the first circuit breaker state, the vehicle-mounted circuit breaker can supply power from the second power supply unit to the load without interrupting the power supply to the load.
[0014] [3] An on-board circuit breaker according to [1] or [2], which has a current detection unit that detects the current flowing from the second power supply unit side to the first power supply unit side, the control unit includes a first cut-off circuit, and the first cut-off circuit switches the first cut-off unit to the first cut-off state when the detection value of the current detection unit exceeds the first threshold value in the first state, and switches the first cut-off unit to the first cut-off state when the detection value of the current detection unit exceeds the second threshold value in the second state.
[0015] The above-mentioned vehicle-mounted circuit breaker can quickly switch the first circuit breaker to the first circuit breaker state by the first circuit breaker circuit when the current flowing from the second power supply unit side to the first power supply unit side exceeds a first threshold value in the first state. Also, the above-mentioned vehicle-mounted circuit breaker can quickly switch the first circuit breaker to the first circuit breaker state by the first circuit breaker circuit when the current flowing from the second power supply unit side to the first power supply unit side exceeds a second threshold value in the second state.
[0016] [4] The vehicle-mounted cutoff device described in [3], wherein the first cutoff circuit includes a first comparator and a second comparator, the first comparator outputs a first cutoff signal when the detection value of the current detection unit exceeds the first threshold in the first state, the second comparator outputs a second cutoff signal when the detection value of the current detection unit exceeds the second threshold in the second state, the first cutoff unit switches to the first cutoff state when the first cutoff signal is output from the first comparator, and also switches to the first cutoff state when the second cutoff signal is output from the second comparator, and the first comparator is OFF in the second state.
[0017] This configuration makes it easy to simplify the configuration of the first shutoff circuit.
[0018] [5] The control unit includes a circuit control unit; the first shutoff circuit includes a comparator; the comparator outputs a shutoff signal when the detection value of the current detection unit exceeds an input value input from the circuit control unit; the circuit control unit inputs the first threshold value to the comparator in the first state and inputs the second threshold value to the comparator in the second state; and the first shutoff unit switches to the first shutoff state when the shutoff signal is output from the comparator.
[0019] The above-described on-vehicle cutoff device can output a cutoff signal according to the state of the vehicle using a single comparator.
[0020] [6] The first state is a state in which power is supplied from the first power supply unit to the conductive path side, and the second state is a state in which power is supplied from the second power supply unit to the first power supply unit. An on-board circuit breaker device described in any one of [1] to [5].
[0021] The above-mentioned vehicle-mounted circuit breaker can immediately switch the first circuit breaker to the first circuit breaker state when a backflow to the first power supply occurs in a state where power is supplied from the first power supply unit to the conductive path side, and can also immediately switch the first circuit breaker to the first circuit breaker state when an overcurrent occurs in a state where power is supplied from the second power supply unit to the first power supply unit.
[0022] [7] The in-vehicle system comprises a high-voltage battery, a system main relay, and a capacitor, wherein the second power supply unit is a low-voltage battery, and the first power supply unit is a voltage conversion unit provided between the high-voltage battery and the low-voltage battery, and the voltage conversion unit performs a first conversion operation of stepping up or stepping down a voltage input from the high-voltage battery side and outputting the voltage to the low-voltage battery side, and a second conversion operation of stepping up or stepping down a voltage input from the low-voltage battery side and outputting the voltage to the high-voltage battery side, the system main relay is provided between the high-voltage battery and the voltage conversion unit, and the capacitor is electrically connected to an electrical path between the system main relay and the voltage conversion unit, and when a start switch of the vehicle is switched on, the in-vehicle system causes the voltage conversion unit to perform the second conversion operation while the system main relay is off to pre-charge the capacitor, and switches the system main relay on after the capacitor has been pre-charged, The vehicle-mounted cutoff device according to [6], wherein the first state is a state in which the start switch is ON and the system main relay is ON, and the second state is a state in which the start switch is ON and the system main relay is OFF.
[0023] The above-mentioned on-board circuit breaker device can immediately switch the first circuit breaker unit to the first circuit breaker state when a backflow to the first power supply unit occurs while the vehicle is running. Also, the above-mentioned on-board circuit breaker device can switch the first circuit breaker unit to the first circuit breaker state when an overcurrent occurs during precharging of the capacitor.
[0024] [8] The control unit switches the first interrupting unit to the first interrupting state, and then returns the first interrupting unit to the first allowing state when a first return condition is satisfied. An on-board circuit breaking device described in any one of [1] to [7].
[0025] Even when the first interrupting unit is switched to the first interrupting state, the above-described vehicle-mounted circuit breaking device can return the first interrupting unit to the first allowing state if the first return condition is satisfied.
[0026] [Details of the embodiments of the present disclosure] 1. First embodiment 1-1. Overview of the on-vehicle system 100 Fig. 1 shows an on-vehicle system 100 including an on-vehicle circuit breaker 10. The on-vehicle system 100 is a system mounted on a vehicle. The on-vehicle system 100 includes a high-voltage battery 91, a low-voltage battery 92, a voltage conversion unit 93, a system main relay 94 (hereinafter also referred to as SMR 94), a capacitor 95, a load 96, a first conductive path 81, a second conductive path 82, and a third conductive path 83.
[0027] The output voltage of the high-voltage battery 91 is higher than the output voltage of the low-voltage battery 92. The high-voltage battery 91 is, for example, a lithium-ion battery or a sodium-ion battery. The low-voltage battery 92 is, for example, a lithium-ion battery or a lead battery. The low-voltage battery 92 corresponds to an example of a second power supply unit.
[0028] The voltage conversion unit 93 corresponds to an example of a first power supply unit. The voltage conversion unit 93 is provided between the high-voltage battery 91 and the low-voltage battery 92. The voltage conversion unit 93 performs a first conversion operation of stepping up or stepping down the voltage input from the high-voltage battery 91 side and outputting the voltage to the low-voltage battery 92 side. The voltage conversion unit 93 also performs a second conversion operation of stepping up or stepping down the voltage input from the low-voltage battery 92 side and outputting the voltage to the high-voltage battery 91 side. The voltage conversion unit 93 is configured by, for example, a DC-DC converter.
[0029] The SMR 94 is provided between the high-voltage battery 91 and the voltage conversion unit 93 .
[0030] The capacitor 95 is electrically connected to the electrical path between the SMR 94 and the voltage conversion unit 93 .
[0031] The first conductive path 81 corresponds to an example of a conductive path. The first conductive path 81 is provided between the voltage conversion unit 93 and the low-voltage battery 92. A load 96 is electrically connected to the first conductive path 81. The second conductive path 82 is provided between the voltage conversion unit 93 and the first conductive path 81. The third conductive path 83 is provided between the low-voltage battery 92 and the first conductive path 81.
[0032] When the start switch of the vehicle is turned ON, the in-vehicle system 100 causes the voltage conversion unit 93 to perform the second conversion operation while keeping the SMR 94 OFF, thereby precharging the capacitor 95. Then, the in-vehicle system 100 turns ON the SMR 94 after precharging the capacitor 95. The start switch is an ignition switch if the vehicle is an engine-equipped vehicle, and is a power switch if the vehicle is an electric vehicle.
[0033] 1-2. Configuration of the Vehicle-Mounted Circuit Breaker 10 The vehicle-mounted circuit breaker 10 is, for example, a junction box. The vehicle-mounted circuit breaker 10 is electrically connected to a voltage conversion unit 93, a low-voltage battery 92, and a load 96.
[0034] The vehicle-mounted circuit breaker 10 includes a first circuit breaker 21 , a second circuit breaker 22 , a current detector 23 , and a controller 30 .
[0035] The first interrupter 21 is provided between the first conductive path 81 and the second conductive path 82. The first interrupter 21 is provided between the voltage converter 93 and the first conductive path 81. One end of the first interrupter 21 is electrically connected to the first conductive path 81. The other end of the first interrupter 21 is electrically connected to the voltage converter 93 via the second conductive path 82. The first interrupter 21 switches between a first permissive state in which it allows bidirectional current flow through itself, and a first blocked state in which it blocks current from flowing from the first conductive path 81 to the voltage converter 93. In this embodiment, when in the first blocked state, the first interrupter 21 allows current to flow from the voltage converter 93 to the first conductive path 81. The first interrupter 21 includes a MOSFET 21A. The first interrupter 21 enters the first permissive state when the MOSFET 21A is turned on. The first cutoff unit 21 is set to the first cutoff state when the MOSFET 21A is turned off. In this embodiment, the first cutoff unit 21 is configured by a normally-off switching element.
[0036] The second circuit breaker 22 is provided between the first conductive path 81 and the third conductive path 83. The second circuit breaker 22 is provided between the low-voltage battery 92 and the first conductive path 81. One end of the second circuit breaker 22 is electrically connected to the first conductive path 81. One end of the second circuit breaker 22 is electrically connected to one end of the first circuit breaker 21 via the first conductive path 81. The other end of the second circuit breaker 22 is electrically connected to the low-voltage battery 92 via the third conductive path 83. The second circuit breaker 22 switches between a second permissive state in which it allows bidirectional current flow through itself, and a second blocked state in which it blocks current from flowing from the first conductive path 81 to the low-voltage battery 92. In this embodiment, the second circuit breaker 22 allows current to flow from the low-voltage battery 92 to the first conductive path 81 when in the second blocked state. The second circuit breaker 22 includes a MOSFET 22A. The second cutoff unit 22 is in the second permissive state when the MOSFET 22A is turned ON. The second cutoff unit 22 is in the second cutoff state when the MOSFET 22A is turned OFF. In this embodiment, the second cutoff unit 22 is configured by a normally-off switching element.
[0037] The current detection unit 23 detects the current flowing from the first conductive path 81 to the voltage conversion unit 93, and also detects the current flowing from the voltage conversion unit 93 to the first conductive path 81. The current detection unit 23 is configured, for example, by a known current sensor. The current detection unit 23 outputs a detection value within a predetermined range (for example, a range of 0 to 5 V). For example, the current detection unit 23 outputs a reference voltage (for example, 2.5 V) when no current is flowing, outputs a voltage greater than the reference voltage when current is flowing from the first conductive path 81 to the voltage conversion unit 93, and outputs a voltage smaller than the reference voltage when current is flowing from the voltage conversion unit 93 to the first conductive path 81. For example, the current detection unit 23 outputs a higher voltage as the current flowing from the first conductive path 81 to the voltage conversion unit 93 increases, and outputs a lower voltage as the current flowing from the voltage conversion unit 93 to the first conductive path 81 increases.
[0038] The control unit 30 controls the first cutoff unit 21 and the second cutoff unit 22. The control unit 30 performs cutoff control. The cutoff control is a control that switches the first cutoff unit 21 to the first cutoff state when a current exceeding a first threshold value TH1 flows from the low-voltage battery 92 side to the voltage conversion unit 93 side when the vehicle is in the first state, and switches the first cutoff unit 21 to the first cutoff state when a current exceeding a second threshold value TH2 flows from the low-voltage battery 92 side to the voltage conversion unit 93 side when the vehicle is in the second state. The second threshold value TH2 is a value greater than the first threshold value TH1.
[0039] When the vehicle is in the first state, the control unit 30 may immediately switch the first cut-off unit 21 to the first cut-off state when a current exceeding the first threshold value TH1 flows from the low-voltage battery 92 side to the voltage conversion unit 93 side, or may switch the first cut-off unit 21 to the first cut-off state when a current exceeding the first threshold value TH1 flows for a predetermined period of time, or may switch the first cut-off unit 21 to the first cut-off state when the average value over a predetermined period of time exceeds the first threshold value TH1.
[0040] When the vehicle is in the second state, the control unit 30 may immediately switch the first cut-off unit 21 to the first cut-off state when a current exceeding the second threshold value TH2 flows from the low-voltage battery 92 side to the voltage conversion unit 93 side, or may switch the first cut-off unit 21 to the first cut-off state when a current exceeding the second threshold value TH2 flows for a predetermined period of time, or may switch the first cut-off unit 21 to the first cut-off state when the average value over a predetermined period of time exceeds the second threshold value TH2.
[0041] The first state is a state in which power is supplied from the voltage conversion unit 93 to the first conductive path 81. In this embodiment, the first state is a state in which the start switch is ON and the SMR 94 is ON. The second state is a state in which power is supplied from the low-voltage battery 92 to the voltage conversion unit 93. In this embodiment, the second state is a state in which the start switch is ON and the SMR 94 is OFF. In other words, the vehicle enters the second state when the start switch is switched ON, and enters the first state when pre-charging is complete.
[0042] The control unit 30 performs the above-described cutoff control when the first cutoff unit 21 is in the first permissive state and the second cutoff unit 22 is in the second permissive state. When the first cutoff unit 21 is in the first permissive state and the second cutoff unit 22 is in the second permissive state, power can be supplied to the load 96 from both the voltage conversion unit 93 and the low-voltage battery 92. When the first cutoff unit 21 is in the first permissive state and the second cutoff unit 22 is in the second permissive state, power is preferably supplied to the load 96 from the voltage conversion unit 93.
[0043] After switching the first blocking unit 21 to the first blocking state, the control unit 30 maintains the first blocking unit 21 in the first blocking state even if current no longer flows from the first conductive path 81 to the voltage conversion unit 93. After switching the first blocking unit 21 to the first blocking state, the control unit 30 restores the first blocking unit 21 to the first permissive state if a first restoration condition is satisfied. The first restoration condition may be, for example, a condition that is met every time a second time shorter than the first time elapses before the first time elapses. The first restoration condition may be that the output voltage of the voltage conversion unit 93 becomes equal to or greater than a first restoration voltage. The first restoration condition may be that the temperature of the first blocking unit 21 becomes equal to or greater than a first restoration temperature.
[0044] The control unit 30 switches the second cutoff unit 22 to the second cutoff state when a cutoff condition is met. The cutoff condition may be met, for example, when the voltage at one end or the other end of the second cutoff unit 22 becomes equal to or lower than a threshold voltage, when a current flows from the first conductive path 81 to the low-voltage battery 92, or another condition. After switching the second cutoff unit 22 to the second cutoff state, the control unit 30 maintains the second cutoff unit 22 in the second cutoff state even if the cutoff condition is no longer met. After switching the second cutoff unit 22 to the second cutoff state, the control unit 30 returns the second cutoff unit 22 to the second permissive state when a second return condition is met. The second return condition may be met, for example, every time a second time shorter than the first time elapses before the first time elapses. The second return condition may be met when the output voltage of the low-voltage battery 92 becomes equal to or higher than a second return voltage. The second return condition may be met when the temperature of the second cutoff unit 22 becomes equal to or higher than a second return temperature.
[0045] Control unit 30 includes a first shutoff circuit 31, a second shutoff circuit 32, and a circuit control unit 33. First shutoff circuit 31 and second shutoff circuit 32 are configured using discrete components. Circuit control unit 33 includes a microcomputer 33A. Microcomputer 33A controls first shutoff circuit 31 and second shutoff circuit 32.
[0046] The first blocking circuit 31 switches the first blocking unit 21 to the first blocking state based on the flow of current from the first conductive path 81 side to the voltage conversion unit 93 side when the first blocking unit 21 is in the first permissive state and the second blocking unit 22 is in the second permissive state.
[0047] First shutoff circuit 31 switches first shutoff unit 21 to the first shutoff state when the detection value of current detection unit 23 exceeds first threshold value TH1 in the first state. First shutoff circuit 31 switches first shutoff unit 21 to the first shutoff state when the detection value of current detection unit 23 exceeds second threshold value TH2 in the second state.
[0048] First shutoff circuit 31 includes a first comparator 31A, a second comparator 31B, a NOR circuit 31C, and a latch circuit 31D.
[0049] The first comparator 31A receives the detection value of the current detection unit 23 and a first threshold value TH1. The detection value of the current detection unit 23 is input to the non-inverting input terminal of the first comparator 31A. The first threshold value TH1 is input to the inverting input terminal of the first comparator 31A. The first comparator 31A outputs a first shutdown signal when the detection value of the current detection unit 23 exceeds the first threshold value TH1 in the first state. The first shutdown signal is a high-level signal. The first comparator 31A does not output the first shutdown signal when the detection value of the current detection unit 23 does not exceed the first threshold value TH1 in the first state. In other words, the first comparator 31A outputs a low-level signal. The first comparator 31A is ON in the first state and OFF in the second state. In other words, the first comparator 31A never outputs the first shutdown signal in the second state, regardless of the detection value of the current detection unit 23.
[0050] The second comparator 31B receives the detection value of the current detection unit 23 and a second threshold value TH2. The detection value of the current detection unit 23 is input to the non-inverting input terminal of the second comparator 31B. The second threshold value TH2 is input to the inverting input terminal of the second comparator 31B. The second comparator 31B outputs a second shutdown signal when the detection value of the current detection unit 23 exceeds the second threshold value TH2 in the second state. The second shutdown signal is a high-level signal. The second comparator 31B does not output the second shutdown signal when the detection value of the current detection unit 23 does not exceed the second threshold value TH2 in the second state. In other words, the second comparator 31B outputs a low-level signal. The second comparator 31B is OFF in the first state and ON in the second state. In other words, the second comparator 31B never outputs the second shutdown signal in the first state, regardless of the detection value of the current detection unit 23.
[0051] The NOR circuit 31C receives the signal output from the first comparator 31A and the signal output from the second comparator 31B. The NOR circuit 31C outputs a high-level signal when the first comparator 31A does not output the first shutdown signal and the second comparator 31B does not output the second shutdown signal. The NOR circuit 31C outputs a low-level signal when the first comparator 31A outputs the first shutdown signal and the second comparator 31B outputs the second shutdown signal.
[0052] The latch circuit 31D receives the signal output from the NOR circuit 31C. The latch circuit 31D outputs a high-level signal (ON signal) until it receives a low-level signal from the NOR circuit 31C, thereby maintaining the first cutoff unit 21 in the first permissive state. When it receives a high-level signal from the NOR circuit 31C, the latch circuit 31D outputs a low-level signal (OFF signal) and switches the first cutoff unit 21 to the first cutoff state. After switching the first cutoff unit 21 to the first cutoff state, the latch circuit 31D maintains the first cutoff unit 21 in the first cutoff state even if the signal input from the NOR circuit 31C returns to a high-level signal. In other words, the latch circuit 31D maintains the first cutoff unit 21 in the first permissive state until the first comparator 31A outputs a first cutoff signal or the second comparator 31B outputs a second cutoff signal. Then, the latch circuit 31D switches the first cutoff unit 21 to the first cutoff state when the first comparator 31A outputs a first cutoff signal or the second comparator 31B outputs a second cutoff signal.
[0053] As a result, the first cut-off unit 21 switches to the first cut-off state when a first cut-off signal is output from the first comparator 31A, and also switches to the first cut-off state when a second cut-off signal is output from the second comparator 31B.
[0054] When the shutoff condition is met, the second shutoff circuit 32 switches the second shutoff unit 22 to the second shutoff state. After switching the second shutoff unit 22 to the second shutoff state, the second shutoff circuit 32 maintains the second shutoff unit 22 in the second shutoff state even if the shutoff condition is no longer met.
[0055] When the first shutoff unit 21 switches to the first shutoff state, the microcomputer 33A determines whether the first return condition is satisfied. For example, when the microcomputer 33A receives a low-level signal output from the NOR circuit 31C, the microcomputer 33A starts determining whether the first return condition is satisfied. When the microcomputer 33A determines that the first return condition is satisfied, the microcomputer 33A controls the first shutoff circuit 31 to return the first shutoff unit 21 to the first permissive state. Specifically, the microcomputer 33A releases the latched state of the latch circuit 31D and causes the latch circuit 31D to output an ON signal.
[0056] When the second interrupting unit 22 is switched to the second interrupted state, the microcomputer 33A determines whether the second return condition is met. If the microcomputer 33A determines that the second return condition is met, the microcomputer 33A controls the second interrupting circuit 32 to return the second interrupting unit 22 to the second permissive state.
[0057] 1-3. Operation Example of the In-Vehicle System 100 When the vehicle start switch is switched ON, the SMR 94 remains OFF, the first shutoff unit 21 enters the first permissive state, the second shutoff unit 22 enters the second permissive state, and the voltage conversion unit 93 performs the second conversion operation. As a result, as shown in FIG. 2, power from the low-voltage battery 92 is precharged to the capacitor 95. When the voltage of the capacitor 95 reaches the target voltage, precharge is completed and the SMR 94 is switched ON. Furthermore, as shown in FIG. 3, the voltage conversion unit 93 performs the first conversion operation, thereby enabling power from the high-voltage battery 91 and power from the low-voltage battery 92 to be supplied to the load 96. As a result, while the vehicle is running, power from the high-voltage battery 91 and power from the low-voltage battery 92 can be supplied to the load 96.
[0058] During precharge, it is necessary to allow current to flow from the low-voltage battery 92 to the voltage conversion unit 93. For this reason, as shown in FIG. 2, the first comparator 31A is turned OFF. However, if an overcurrent flows, the second comparator 31B is turned ON so that the current can be cut off. In this state, if a ground fault occurs in the second conductive path 82 as shown in FIG. 4, for example, current from the low-voltage battery 92 flows to the ground-fault location in the second conductive path 82. Then, when an overcurrent flows in the first conductive path 82, the second comparator 31B outputs a second cutoff signal, and the first cutoff unit 21 is switched to the first cutoff state as shown in FIG. 5. This suppresses the overcurrent.
[0059] Furthermore, while the vehicle is traveling, it is necessary to maintain a state in which power can be supplied to the load 96 from both the voltage conversion unit 93 and the low-voltage battery 92, while quickly interrupting the reverse current flow from the first conduction path 81 to the voltage conversion unit 93. Therefore, as shown in FIG. 3 , the first comparator 31A is turned ON and the second comparator 31B is turned OFF. In this state, if a ground fault occurs in the second conduction path 82, as shown in FIG. 6 , for example, current from the low-voltage battery 92 flows to the ground-fault location in the second conduction path 82. When the current flowing from the first conduction path 81 to the voltage conversion unit 93 exceeds a first threshold value TH1, the first comparator 31A outputs a first interruption signal, and the first interruption unit 21 is switched to the first interruption state as shown in FIG. 7 . This allows the power supply source to be switched from the voltage conversion unit 93 to the low-voltage battery 92 so that the power supply to the load 96 is not interrupted.
[0060] 1-4. Example of Effects of the Vehicle Circuit Breaker 10 When the vehicle is in the first state, the vehicle circuit breaker 10 switches the first circuit breaker 21 to the first circuit breaker state based on a current exceeding a first threshold value TH1 flowing from the low-voltage battery 92 to the voltage converter 93. When the vehicle is in the second state, the vehicle circuit breaker 10 switches the first circuit breaker 21 to the first circuit breaker state based on a current exceeding a second threshold value TH2, which is greater than the first threshold value TH1, flowing from the low-voltage battery 92 to the voltage converter 93. In other words, the vehicle circuit breaker 10 can change the threshold value for switching the first circuit breaker 21 to the first circuit breaker state depending on the state of the vehicle, and can therefore appropriately interrupt the current depending on the state of the vehicle.
[0061] The vehicle-mounted circuit breaking device 10 performs circuit breaking control when the first circuit breaking unit 21 is in the first permissive state and the second circuit breaking unit 22 is in the second permissive state. Therefore, even when the first circuit breaking unit 21 switches to the first circuit breaking state, the vehicle-mounted circuit breaking device 10 can supply power from the low-voltage battery 92 to the load 96 without interrupting the power supply to the load 96.
[0062] When the current flowing from the low-voltage battery 92 side to the voltage conversion unit 93 side exceeds a first threshold value TH1 in the first state, the vehicle shutoff device 10 can quickly switch the first shutoff unit 21 to the first shutoff state by the first shutoff circuit 31. Furthermore, when the current flowing from the low-voltage battery 92 side to the voltage conversion unit 93 side exceeds a second threshold value TH2 in the second state, the vehicle shutoff device 10 can also quickly switch the first shutoff unit 21 to the first shutoff state by the first shutoff circuit 31.
[0063] The first shutoff circuit 31 includes a first comparator 31A and a second comparator 31B. In the vehicle shutoff device 10, the first comparator 31A outputs a first shutoff signal when the detection value of the current detection unit 23 exceeds a first threshold value TH1 in the first state. The second comparator 31B outputs a second shutoff signal when the detection value of the current detection unit 23 exceeds a second threshold value TH2 in the second state. The first shutoff unit 21 switches to the first shutoff state when the first comparator 31A outputs the first shutoff signal, and also switches to the first shutoff state when the second comparator 31B outputs the second shutoff signal. The first comparator 31A is OFF in the second state. This configuration makes it easy to simplify the configuration of the first shutoff circuit 31.
[0064] In a state where power is supplied from the voltage conversion unit 93 to the first conductive path 81, the vehicle circuit breaker 10 can immediately switch the first circuit breaker 21 to the first circuit breaker state if a backflow occurs to the voltage conversion unit 93. In addition, in a state where power is supplied from the low-voltage battery 92 to the voltage conversion unit 93, the vehicle circuit breaker 10 can immediately switch the first circuit breaker 21 to the first circuit breaker state if an overcurrent occurs.
[0065] The on-board circuit breaker 10 can immediately switch the first circuit breaker 21 to the first circuit break state when a backflow to the voltage conversion unit 93 occurs while the vehicle is running. Also, the on-board circuit breaker 10 can switch the first circuit breaker 21 to the first circuit break state when an overcurrent occurs during precharging of the capacitor 95.
[0066] Even when the first interrupting unit 21 is switched to the first interrupting state, the vehicle-mounted circuit breaking device 10 can return the first interrupting unit 21 to the first allowing state if the first return condition is satisfied.
[0067] 2. Second Embodiment In the first embodiment, a configuration including a first comparator 31A to which a first threshold value TH1 is input and a second comparator 31B to which a second threshold value TH2 is input will be described. In the second embodiment, a configuration in which the threshold value input to the comparator 231A is changed will be described. Note that the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.
[0068] 2-1. Overview of the In-Vehicle System 200 As shown in FIG. 8 , the in-vehicle system 200 of the second embodiment includes a high-voltage battery 91, a low-voltage battery 92, a voltage conversion unit 93, an SMR 94, a capacitor 95, a load 96, a first conductive path 81, a second conductive path 82, and a third conductive path 83.
[0069] 2-2. Configuration of on-board shutoff device 210 On-board system 200 includes on-board shutoff device 210. On-board shutoff device 210 has first shutoff unit 21, second shutoff unit 22, current detection unit 23, and control unit 230. Control unit 230 includes first shutoff circuit 231, second shutoff circuit 232, and circuit control unit 233.
[0070] The first shutoff circuit 231 is configured with discrete components. The circuit control unit 233 includes a microcomputer 233A and a threshold value changing circuit 233B. The microcomputer 233A controls the first shutoff circuit 231 and the second shutoff circuit 232. The threshold value changing circuit 233B is configured with discrete components. The threshold value changing circuit 233B selectively outputs a first threshold value TH1 and a second threshold value TH2 in response to an instruction from the microcomputer 233A. The threshold value changing circuit 233B outputs the first threshold value TH1 in the first state and the second threshold value TH2 in the second state. The value output from the threshold value changing circuit 233B is input to the first shutoff circuit 231. The first shutoff circuit 231 switches the first shutoff unit 21 to the first shutoff state when the detection value of the current detection unit 23 exceeds the value input from the threshold value changing circuit 233B.
[0071] The first blocking circuit 231 switches the first blocking unit 21 to the first blocking state based on the flow of current from the first conductive path 81 side to the voltage conversion unit 93 side when the first blocking unit 21 is in the first permissive state and the second blocking unit 22 is in the second permissive state.
[0072] First shutoff circuit 231 switches first shutoff unit 21 to the first shutoff state when the detection value of current detection unit 23 exceeds first threshold value TH1 in the first state. First shutoff circuit 231 switches first shutoff unit 21 to the first shutoff state when the detection value of current detection unit 23 exceeds second threshold value TH2 in the second state.
[0073] First shutoff circuit 231 includes a comparator 231A, a NOT circuit 231C, and a latch circuit 231D.
[0074] The comparator 231A receives the detection value of the current detection unit 23 and the output value of the threshold change circuit 233B. The detection value of the current detection unit 23 is input to the non-inverting input terminal of the comparator 231A. The output value of the threshold change circuit 233B is input to the inverting input terminal of the comparator 231A. In the first state, a first threshold TH1 is input to the inverting input terminal of the comparator 231A. In the second state, a second threshold TH2 is input to the inverting input terminal of the comparator 231A.
[0075] The comparator 231A outputs a cutoff signal when the detection value of the current detection unit 23 exceeds the input value from the threshold value changing circuit 233B. The cutoff signal is a high-level signal. The comparator 231A does not output a cutoff signal when the detection value of the current detection unit 23 does not exceed the input value from the threshold value changing circuit 233B. In other words, the comparator 231A outputs a low-level signal.
[0076] The NOT circuit 231C receives the signal output from the comparator 231A. If the comparator 231A does not output a cutoff signal, the NOT circuit 231C outputs a high-level signal. If the comparator 231A outputs a cutoff signal, the NOT circuit 231C outputs a low-level signal.
[0077] The latch circuit 31D receives the signal output from the NOT circuit 231C. The latch circuit 31D outputs a high-level signal (ON signal) until it receives a low-level signal from the NOT circuit 231C, thereby maintaining the first cutoff unit 21 in the first permissive state. When it receives a low-level signal from the NOT circuit 231C, the latch circuit 31D outputs a low-level signal (OFF signal) and switches the first cutoff unit 21 to the first cutoff state. After switching the first cutoff unit 21 to the first cutoff state, the latch circuit 31D maintains the first cutoff unit 21 in the first cutoff state even if the signal input from the NOT circuit 231C returns to a high-level signal. In other words, the latch circuit 31D maintains the first cutoff unit 21 in the first permissive state until it receives a cutoff signal from the comparator 231A. When the comparator 231A outputs a cutoff signal, the latch circuit 31D switches the first cutoff unit 21 to the first cutoff state.
[0078] As a result, the first cutoff unit 21 switches to the first cutoff state when a cutoff signal is output from the comparator 231A.
[0079] When the first shutoff unit 21 switches to the first shutoff state, the microcomputer 233A determines whether the first return condition is satisfied. For example, when the microcomputer 233A receives a low-level signal output from the NOT circuit 231C, the microcomputer 233A starts determining whether the first return condition is satisfied. When the microcomputer 233A determines that the first return condition is satisfied, the microcomputer 233A controls the first shutoff circuit 231 to return the first shutoff unit 21 to the first permissive state. Specifically, the microcomputer 233A releases the latched state of the latch circuit 31D and causes the latch circuit 31D to output an ON signal.
[0080] 2-3. Operation Example of the In-Vehicle System 200 When the start switch is switched ON, the SMR 94 remains OFF, the first shutoff unit 21 enters the first permissive state, the second shutoff unit 22 enters the second permissive state, and the voltage conversion unit 93 performs the second conversion operation. As a result, as shown in FIG. 9 , power from the low-voltage battery 92 is precharged to the capacitor 95. When the voltage of the capacitor 95 reaches the target voltage, precharge is completed and the SMR 94 is switched ON. Furthermore, as shown in FIG. 10 , the voltage conversion unit 93 performs the first conversion operation, and power from the high-voltage battery 91 and the low-voltage battery 92 is able to be supplied to the load 96. As a result, power from the high-voltage battery 91 and the low-voltage battery 92 is able to be supplied to the load 96 while the vehicle is running.
[0081] During precharge, it is necessary to allow current to flow from the low-voltage battery 92 to the voltage conversion unit 93. For this reason, as shown in FIG. 9 , a second threshold value TH2 is input to the comparator 231A. In this state, if a ground fault occurs in the second conductive path 82, as shown in FIG. 11 , for example, current from the low-voltage battery 92 flows to the ground-fault location in the second conductive path 82. When an overcurrent flows in the first conductive path 81, the comparator 231A outputs a cutoff signal, and the first cutoff unit 21 is switched to the first cutoff state as shown in FIG. 12 . This suppresses the overcurrent.
[0082] Furthermore, while the vehicle is traveling, it is necessary to maintain a state in which power can be supplied to the load 96 from both the voltage conversion unit 93 and the low-voltage battery 92, while quickly interrupting any backflow from the first conduction path 81 to the voltage conversion unit 93. For this reason, as shown in FIG. 10 , a first threshold value TH1 is input to the comparator 231A. In this state, if a ground fault occurs in the second conduction path 82, as shown in FIG. 13 , for example, current from the low-voltage battery 92 flows to the ground-fault location in the second conduction path 82. When the current flowing from the first conduction path 81 to the voltage conversion unit 93 exceeds the first threshold value TH1, the comparator 231A outputs an interruption signal, and the first interrupter 21 is switched to the first interruption state, as shown in FIG. 14 . This allows the power supply source to be switched from the voltage conversion unit 93 to the low-voltage battery 92 so that the power supply to the load 96 is not interrupted.
[0083] 2-4. Example of Effects of the Vehicle-Mounted Cutoff Device 210 The vehicle-mounted cutoff device 210 can output a cutoff signal according to the state of the vehicle using a single comparator 231A.
[0084] <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.
[0085] In each of the above embodiments, the first cutoff unit 21 is configured only by the MOSFET 21A. However, the first cutoff unit 21 may be configured by a pair of MOSFETs connected in opposite directions. In this case, the first cutoff unit 21 cuts off the flow of current in both directions through itself when in the first cutoff state. Furthermore, the first cutoff unit 21 may be configured by a switch other than a MOSFET.
[0086] In each of the above embodiments, the second cutoff unit 22 is configured only by the MOSFET 22A. However, the second cutoff unit 22 may be configured by a pair of MOSFETs connected in opposite directions. In this case, the second cutoff unit 22 cuts off the flow of current in both directions through itself when in the second cutoff state. Furthermore, the second cutoff unit 22 may be configured by a switch other than a MOSFET.
[0087] 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.
[0088] DESCRIPTION OF SYMBOLS 10...In-vehicle circuit breaking device 21...First breaking section 21A...MOSFET 22...Second breaking section 22A...MOSFET 23...Current detection section 30...Control section 31...First breaking circuit 31A...First comparator 31B...Second comparator 31C...NOR circuit 31D...Latch circuit 32...Second breaking circuit 33...Circuit control section 33A...Microcomputer 81...First conductive path (conductive path) 82...Second conductive path 83...Third conductive path 91...High voltage battery 92...Low voltage battery (second power supply section) 93...Voltage conversion section (first power supply section) 94...System main relay 95...Capacitor 96...Load 100...In-vehicle system 200...In-vehicle system 210...In-vehicle circuit breaking device 230...Control section 231...First breaking circuit 231A...Comparator 231C... NOT circuit 233... Circuit control section 233A... Microcomputer 233B... Threshold value changing circuit TH1... First threshold value TH2... Second threshold value
Claims
1. An on-board circuit breaker included in an on-board system having: a first power supply unit; a second power supply unit; a conductive path provided between the first power supply unit and the second power supply unit; and a load electrically connected to the conductive path, the on-board circuit breaker having a first circuit breaker provided between the first power supply unit and the conductive path; and a control unit that controls the first circuit breaker, the first circuit breaker switching between a first permissive state that allows current to flow from the second power supply unit side to the first power supply unit side and a first circuit breaker state that blocks current from flowing from the second power supply unit side to the first power supply unit side, the control unit performing circuit breaker control to switch the first circuit breaker to the first circuit breaker state based on a current exceeding a first threshold value flowing from the second power supply unit side to the first power supply unit side when the vehicle is in a first state, and to switch the first circuit breaker to the first circuit breaker state based on a current exceeding a second threshold value larger than the first threshold value flowing from the second power supply unit side to the first power supply unit side when the vehicle is in a second state.
2. An on-board circuit breaker as described in claim 1, further comprising a second circuit breaker provided between the second power supply unit and the conductive path, the second circuit breaker being controlled by the control unit and switching between a second permissive state that allows current to flow from the first power supply unit side to the second power supply unit side and a second circuit breaker state that blocks current from flowing from the first power supply unit side to the second power supply unit side, and the control unit performing the circuit breaker control when the first circuit breaker is in the first permissive state and the second circuit breaker is in the second permissive state.
3. An on-board circuit breaker as described in claim 1 or claim 2, further comprising a current detection unit which detects the current flowing from the second power supply unit to the first power supply unit, wherein the control unit includes a first circuit breaker, wherein the first circuit breaker switches the first circuit breaker to the first circuit breaker state when the detection value of the current detection unit exceeds the first threshold value in the first state, and switches the first circuit breaker to the first circuit breaker state when the detection value of the current detection unit exceeds the second threshold value in the second state.
4. The vehicle-mounted cut-off device according to claim 3, wherein the first cut-off circuit includes a first comparator and a second comparator, the first comparator outputs a first cut-off signal when the detection value of the current detection unit exceeds the first threshold in the first state, the second comparator outputs a second cut-off signal when the detection value of the current detection unit exceeds the second threshold in the second state, the first cut-off unit switches to the first cut-off state when the first cut-off signal is output from the first comparator, and also switches to the first cut-off state when the second cut-off signal is output from the second comparator, and the first comparator is OFF in the second state.
5. The vehicle-mounted cut-off device according to claim 3, wherein the control unit includes a circuit control unit; the first cut-off circuit includes a comparator; the comparator outputs a cut-off signal when the detection value of the current detection unit exceeds an input value input from the circuit control unit; the circuit control unit inputs the first threshold value to the comparator in the first state and inputs the second threshold value to the comparator in the second state; and the first cut-off unit switches to the first cut-off state when the cut-off signal is output from the comparator.
6. An on-board circuit breaker device as described in claim 1 or claim 2, wherein the first state is a state in which power is supplied from the first power supply unit to the conductive path side, and the second state is a state in which power is supplied from the second power supply unit to the first power supply unit.
7. The vehicle-mounted system includes a high-voltage battery, a system main relay, and a capacitor, the second power supply unit is a low-voltage battery, the first power supply unit is a voltage conversion unit provided between the high-voltage battery and the low-voltage battery, the voltage conversion unit performs a first conversion operation of stepping up or stepping down a voltage input from the high-voltage battery side and outputting the voltage to the low-voltage battery side, and a second conversion operation of stepping up or stepping down a voltage input from the low-voltage battery side and outputting the voltage to the high-voltage battery side, the system main relay is provided between the high-voltage battery and the voltage conversion unit, and the capacitor is electrically connected to an electric path between the system main relay and the voltage conversion unit, and when a start switch of the vehicle is switched ON, the vehicle-mounted system causes the voltage conversion unit to perform the second conversion operation while keeping the system main relay OFF to pre-charge the capacitor, and switches the system main relay ON after pre-charging the capacitor, 7. The vehicle-mounted cutoff device according to claim 6, wherein the first state is a state in which the starter switch is ON and the system main relay is ON, and the second state is a state in which the starter switch is ON and the system main relay is OFF.
8. An on-board cutoff device as described in claim 1 or claim 2, wherein the control unit, after switching the first cutoff unit to the first cutoff state, returns the first cutoff unit to the first permissive state when a first return condition is satisfied.