Overdischarge prevention system, and overdischarge prevention method

Abstract

In the present invention, a first switch is provided on a path connecting a battery (10), which supplies power to a plurality of loads provided in a vehicle, and a first load from among the plurality of loads. A current sensor (400) detects the current value of a current flowing between the battery (10) and the first load. A first control circuit controls the first switch. The first control circuit temporarily turns off the first switch when the current value detected by the current sensor (400) when the first switch has been turned on exceeds a current threshold corresponding to a current vehicle state and the first load.

Description

Over-discharge suppression system and over-discharge suppression method

[0001] The present invention relates to an over-discharge suppression system and an over-discharge suppression method.

[0002] In recent years, with the increase in the functions of vehicles, the number of ECUs (Electronic Control Units) installed in vehicles has been increasing. An ECU is a load that operates by receiving power supply from a battery or a generator installed in a vehicle. The ECU operates within a range of power consumption according to the vehicle state. For example, many ECUs shift to a sleep state and operate with low power consumption when the ignition is off.

[0003] However, the ECU may fail to shift to the sleep state. In this case, since the current flowing from the battery to the ECU is large, the possibility of over-discharge of the battery increases. Currently, technologies for suppressing such over-discharge of the battery have been developed. For example, Patent Document 1 describes a technology for temporarily stopping the power supply to all ECUs when the current value of the dark current flowing from the battery is equal to or greater than a threshold value. The technology described in Patent Document 1 restarts the ECU that has failed to shift to the sleep state and shifts it to the sleep state.

[0004] Japanese Unexamined Patent Application Publication No. 2022 - 158108

[0005] However, in the technology described in Patent Document 1, since the power supply to all ECUs is stopped, the operation of the ECUs that have been operating normally is also interrupted. Therefore, in the technology described in Patent Document 1, some functions of the vehicle are impaired. For this reason, a technology for suppressing over-discharge of the battery installed in a vehicle without impairing the functions of the vehicle as much as possible is desired.

[0006] The present invention has been made in view of the above problems, and an object thereof is to provide an over-discharge suppression system and an over-discharge suppression method that suppress over-discharge of a battery installed in a vehicle without impairing the functions of the vehicle as much as possible.

[0007] To achieve the above objective, the over-discharge suppression system according to the present invention comprises a first switch, a current sensor, and a first control circuit. The first switch is provided on a path connecting a battery that supplies power to a plurality of loads in a vehicle and a first load among the plurality of loads. The current sensor detects the current value of the current flowing between the battery and the first load. The first control circuit controls the first switch. When the first switch is ON, if the current value detected by the current sensor exceeds a current threshold corresponding to the current vehicle state and the first load, the first control circuit temporarily turns off the first switch.

[0008] According to the present invention, it is possible to suppress over-discharge of a battery installed in a vehicle without impairing the vehicle's functions as much as possible.

[0009] This is a diagram of the in-vehicle system according to Embodiment 1. This is a diagram showing the current threshold information according to Embodiment 1. This is a flowchart showing the first switch control process executed by the microcomputer according to Embodiment 1. This is a flowchart showing the first load reset process shown in Figure 3. This is a flowchart showing the second switch control process executed by the microcomputer according to Embodiment 1. This is a diagram of the in-vehicle system according to Embodiment 2. This is a flowchart showing the first load reset process executed by the microcomputer according to Embodiment 2.

[0010] Embodiments of the present invention will be described in detail below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals.

[0011] (Embodiment 1) Figure 1 is a diagram of the configuration of an in-vehicle system 2000 according to Embodiment 1. The in-vehicle system 2000 is installed in vehicles such as gasoline cars, hybrid cars, and electric vehicles. The in-vehicle system 2000 comprises a battery 10, a generator 20, an ECU 601, an ECU 602, an ECU 603, and an over-discharge suppression system 1000. Hereinafter, ECU 601, ECU 602, and ECU 603 will be collectively referred to as ECU 600.

[0012] The battery 10 is a secondary battery mounted in the vehicle, which stores power supplied from the generator 20 and supplies the stored power to the load. In this embodiment, the load consists of three ECUs 600. The battery 10 is, for example, a lithium-ion secondary battery. The generator 20 is a generator mounted in the vehicle. The generator 20 supplies the power generated to the battery 10. The generator 20 is, for example, an alternator mounted in the vehicle.

[0013] The ECU 600 is an electronic control unit mounted in the vehicle, and is a computer that implements a corresponding function among the multiple functions that the vehicle has. The ECU 600 is a load that operates on power supplied from the battery 10. Examples of ECU 600s include an engine ECU, a transmission ECU, an EPS (Electric Power Steering) ECU, a brake ECU, a door lock control ECU, a power window ECU, an anti-theft ECU, and an external communication ECU. The ECU 600 may include sensors that operate on power supplied from the ECU 600 itself. The power terminals (not shown) of the ECU 600 are grounded by pull-down resistors (not shown). When current stops flowing from the battery 10 to the ECU 600, the voltage at the power terminals of the ECU 600 drops and the ECU 600 stops operating. Subsequently, when current flows from the battery 10 to the ECU 600, the voltage at the power terminals of the ECU 600 rises and the ECU 600 performs an initialization process by power-on reset.

[0014] The over-discharge suppression system 1000 suppresses over-discharge of the battery 10. When the over-discharge suppression system 1000 detects an abnormal current value, it attempts to resolve the abnormal current value by restarting the ECU 600. An abnormal current value is a state in which a current exceeding a standard value flows from the battery 10 to the ECU 600. An abnormal current value occurs, for example, when the ECU 600, which should enter a sleep state, fails to enter a sleep state due to an accidental or temporary malfunction. If the abnormal current value continues, the likelihood of over-discharge of the battery 10 increases. Therefore, when the over-discharge suppression system 1000 detects an abnormal current value, it forcibly restarts the ECU 600 by temporarily interrupting the current flowing to the ECU 600. The ECU 600 enters a sleep state during the initialization process by power-on reset after restarting. As a result, the abnormal current value is resolved, and over-discharge of the battery 10 is suppressed.

[0015] The over-discharge suppression system 1000 includes a microcomputer 100, a microcomputer 200, a switch 301, a switch 302, a switch 303, a switch 310, a current sensor 401, a current sensor 402, a current sensor 403, a fuse 501, a fuse 502, and a fuse 503. Hereinafter, switches 301, 302, and 303 will be collectively referred to as switch 300, current sensors 401, 402, and 403 will be collectively referred to as current sensor 400, and fuses 501, 502, and 503 will be collectively referred to as fuse 500.

[0016] The microcomputer 100 is an integrated circuit that controls the switch 300. The microcomputer 100 comprises a control circuit 110, a memory circuit 120, and an input / output circuit 130. The control circuit 110 functions as a central processing unit that executes processing and calculations related to the control of the microcomputer 100. The control circuit 110 is, for example, a circuit that constitutes a CPU (Central Processing Unit). The memory circuit 120 is a circuit that stores programs and data used by the control circuit 110. The memory circuit 120 is composed of, for example, ROM (Read Only Memory), RAM (Random Access Memory), etc. The input / output circuit 130 inputs data from outside the microcomputer 100 and outputs data to outside the microcomputer 100. The input / output circuit 130 comprises, for example, a digital input port, a digital output port, an analog input port, an analog output port, etc. The input / output circuit 130 may also function as a communication circuit that communicates with the ECU 600 via an in-vehicle LAN (Local Area Network). The microcomputer 100 is an example of a first integrated circuit. Control circuit 110 is an example of a first control circuit.

[0017] The microcomputer 200 controls the switch 310. The microcomputer 200 has basically the same configuration as the microcomputer 100. The microcomputer 200 includes a control circuit 210, a memory circuit 220, and an input / output circuit 230. The control circuit 210, the memory circuit 220, and the input / output circuit 230 have the same configuration as the control circuit 110, the memory circuit 120, and the input / output circuit 130, respectively. The microcomputer 200 is an example of a second integrated circuit. The control circuit 210 is an example of a second control circuit.

[0018] Switch 300 controls the flow of current from the battery 10 to the first load according to the control of the microcomputer 100. When switch 300 is turned on, the ends of switch 300 become conductive, allowing current to flow between the ends of switch 300. When switch 300 is turned off, the ends of switch 300 become insulated, and current no longer flows between the ends of switch 300. Switch 300 is provided on the path connecting the battery 10 and the first load. For example, switch 301 is provided on the path connecting the battery 10 and the ECU 601. The first load is one of several loads provided by the vehicle, and the power supply is controlled by the control circuit 110 that controls switch 300. The first load is assumed to be a load in which the abnormal current value condition is expected to be resolved by restarting the power supply. In this embodiment, ECU 601, ECU 602, and ECU 603 are all first loads. Switch 300 includes a semiconductor switch, such as a p-channel MOSFET (Metal Oxide Semiconductor Field Effect Transistor). Switches 300, 301, 302, and 303 are examples of the first switch.

[0019] Switch 310 controls the flow of current from the battery 10 to the first load according to the control of the microcomputer 200. Switch 310 is provided in parallel with the first switch in the path connecting the battery 10 and the first load. In this embodiment, switch 310 is provided in parallel with switch 303 in the path connecting the battery 10 and the ECU 603. Switch 310 includes a semiconductor switch, such as an n-channel MOSFET. Switch 310 is an example of a second switch.

[0020] The current sensor 400 comprises a shunt resistor 410 and a voltage sensor 420, and detects the current value of the current flowing from the battery 10 to the ECU 600. For example, the current sensor 401 comprises a shunt resistor 411 and a voltage sensor 421, and detects the current value of the current flowing from the battery 10 to the ECU 601. The shunt resistor 410 is provided on the path connecting the battery 10 and the ECU 600, and generates a voltage across the shunt resistor 410 that corresponds to the current value of the current flowing through the shunt resistor 410. The voltage sensor 420 detects the voltage across the shunt resistor 410. The voltage sensor 420 supplies digital voltage information indicating the voltage across the shunt resistor 410 to the microcomputer 100 as current value information indicating the current value of the current flowing through the shunt resistor 410. Current sensors 400, 401, 402, and 403 are examples of current sensors.

[0021] Fuse 500 is a component that prevents current exceeding the rated current from flowing through the ECU 600 and the wires in its path. Fuse 501 is provided on the path connecting the battery 10 and the ECU 601. Fuse 502 is provided on the path connecting the battery 10 and the ECU 602. Fuse 503 is provided on the path connecting the battery 10 and the ECU 603.

[0022] The control circuit 110 controls the switch 300 to be on or off. Normally, the control circuit 110 turns on the switch 300 to supply power to the first load. When the switch 300 is on, if the current value detected by the current sensor 400 exceeds the current threshold, the control circuit 110 temporarily turns off the switch 300. This current threshold is a threshold corresponding to the current vehicle state and the first load. The current threshold is set to a value greater than, for example, the upper limit of the current expected to flow to the first load in the current vehicle state. Current threshold information indicating the current threshold is stored, for example, in the memory circuit 120.

[0023] Figure 2 shows an example of current threshold information. Current threshold information indicates the current threshold for each combination of vehicle state and first load. Vehicle state is the state of the vehicle, and is defined by, for example, the ignition state, the state of the onboard LAN (Local Area Network), etc. Figure 2 shows three vehicle states: ignition ON, ignition OFF and onboard LAN not sleeping, and ignition OFF and onboard LAN sleeping. When the ignition is ON, the vehicle's electrical components are able to operate at full performance. When the ignition is ON, the onboard LAN does not sleep. When the ignition is OFF, only specific electrical components of the vehicle are able to operate. When the ignition is OFF and the onboard LAN is not sleeping, communication is possible between each ECU 600 via the onboard LAN. When the ignition is off and the vehicle's LAN is in sleep mode, communication between the ECUs 600 is not possible.

[0024] The methods for classifying vehicle states are not limited to the examples given above. For example, vehicle states may be classified by states such as ready to drive, standby, driving, and stopped. The ready to drive state is when the vehicle is accelerating with the accelerator pedal pressed, and includes both the driving state and the stopped state where the vehicle is drivable. The ready to drive state is also called the Ready ON state. The standby state is when the vehicle is not accelerating with the accelerator pedal pressed, and is a stopped state where the vehicle is not drivable. The standby state is also called the Ready OFF state.

[0025] When the control circuit 110 detects an abnormal current value in the ECU 601, it attempts to resolve this abnormal current value by resetting the ECU 601. For example, if the current value detected by the current sensor 401 exceeds 5mA while the in-vehicle LAN is in sleep mode, the control circuit 110 temporarily turns off the switch 301. In this case, the abnormal current value in the ECU 601 may be resolved by the initialization process performed after the ECU 601 is restarted. The control circuit 110 also attempts to resolve abnormal current value conditions in the ECUs 602 and 603 in a similar manner as appropriate.

[0026] The control circuit 210 controls switch 310, which is provided in parallel with switch 303, to turn on or off. More specifically, the control circuit 210 turns on switch 310 while the current vehicle state is one in which power should be maintained to the ECU 603. For example, while the vehicle is running, power needs to be supplied to the ECU for the EPS, which is responsible for power steering. Therefore, for example, if the ECU 603 is the EPS ECU and the current vehicle state is running, switch 310 is turned on so that power is supplied to the ECU 603 regardless of the state of switch 303. Thus, switch 310 is provided to ensure power is supplied to the ECU 603 when switch 303 is accidentally turned off.

[0027] The control circuit 210 can determine whether or not to maintain the power supply to each ECU 600 in each vehicle state by referring to the operation stop prohibition information stored in the memory circuit 220. The operation stop prohibition information is, for example, information indicating whether or not operation stoppage is prohibited for each combination of vehicle state and first load. For example, the operation stop prohibition information indicates that operation stoppage is prohibited for a combination of driving state and brake ECU.

[0028] Possible causes of the switch 303 being accidentally turned off include a malfunction in the microcomputer 100, a malfunction in the drive circuit (not shown) that drives the switch 300, etc. Possible malfunctions in the microcomputer 100 include a program bug, a surge voltage, or a malfunction due to overheating. Possible malfunctions in the drive circuit include an initial defect or an abnormal resistance value of an internal resistor due to aging. In addition, if a current exceeding the current threshold flows through the ECU 603, the microcomputer 100 will temporarily turn off the switch 303.

[0029] For an ECU 600 that is desired to maintain its function under specific vehicle conditions, it is preferable to provide a switch 310 in parallel with the switch 300. Examples of such ECUs include the EPS ECU mentioned above, as well as brake ECUs, anti-theft ECUs, door lock control ECUs, and external communication ECUs. For example, in a brake ECU, the switch 310 is provided so that the brake function is maintained at least while the vehicle is in motion. In an anti-theft ECU, the switch 310 is provided so that the anti-theft function is maintained at least while the vehicle is stopped. In an ECU for door lock control, the switch 310 is provided so that the door lock control function is maintained at least while the vehicle is stopped. In an external communication ECU, the switch 310 is provided so that the external communication function is maintained at least when the vehicle is in a collision.

[0030] The control circuit 110 is implemented on the microcomputer 100, and the control circuit 210 is implemented on a different microcomputer 200. This configuration reduces the probability of the power supply to the ECU 600 being accidentally cut off. For example, even if the microcomputer 100, which is experiencing thermal runaway, accidentally turns off switch 303, the microcomputer 200, which is not experiencing thermal runaway, keeps switch 310 on, thereby maintaining the power supply to the ECU 600.

[0031] If the current value detected by the current sensor 400 exceeds the current threshold even after the switch 300 has been temporarily turned off and then on again, the control circuit 110 will keep the switch 300 continuously off. In other words, if the abnormal current value condition is not resolved by resetting, the power supply to the ECU 600 will be continuously stopped. For example, an abnormal current value condition may occur due to a decrease in the insulation performance of components located on the path connecting the battery 10 and the ECU 600. In this case, a reduction in the current value by resetting the ECU 600 cannot be expected, so the power supply to the ECU 600 will be stopped. Thus, preventing over-discharge of the battery 10 takes precedence over maintaining the functionality of the ECU 600.

[0032] Next, the first switch control process performed by the microcomputer 100 will be described with reference to the flowchart in Figure 3. The first switch control process is the process of controlling the first switch, switch 300. The first switch control process is performed periodically, for example, while the power of the microcomputer 100 is turned on. Immediately after the power of the microcomputer 100 is turned on, all three first switches are set to the ON position.

[0033] First, the control circuit 110 of the microcomputer 100 selects one first switch (step S101). For example, the control circuit 110 selects one switch 300 from among three switches 300 in a predetermined order. The following description will focus on the case where the control circuit 110 selects switch 301 in step S101. Next, the control circuit 110 identifies the current vehicle state (step S102). For example, the control circuit 110 identifies the current vehicle state by obtaining vehicle state information indicating the current vehicle state from the ECU 600 via the in-vehicle LAN.

[0034] Next, the control circuit 110 identifies a current threshold (step S103). For example, the control circuit 110 refers to the current threshold information stored in the memory circuit 120 to identify a current threshold corresponding to the combination of the current vehicle state and the ECU 601 corresponding to the selected switch 301. Next, the control circuit 110 acquires the current value of the current flowing to the first load (step S104). For example, the control circuit 110 acquires the current value indicated by the current value information output by the current sensor 401.

[0035] Next, the control circuit 110 determines whether the current value exceeds the current threshold (step S105). If the control circuit 110 determines that the current value does not exceed the current threshold (step S105: NO), it maintains the state of the first switch in its current state (step S106). Basically, since the first switch is ON, the control circuit 110 maintains the first switch ON. However, if the current value abnormality condition has not been resolved and the first switch was OFF, the control circuit 110 maintains the first switch OFF. If the control circuit 110 determines that the current value exceeds the current threshold (step S105: YES), it executes the first load reset process (step S107).

[0036] Referring to Figure 4, the first load reset process will be explained. The first load reset process is a process that resets the first load by temporarily stopping the power supply to the first load. The control circuit 110 turns off the first switch (step S201). After completing the process in step S201, the control circuit 110 determines whether or not the first load has lost power (step S202).

[0037] For example, the control circuit 110 determines whether a specified time has elapsed since the switch 301 was turned off. The specified time is the time required for the power stored in the internal battery, capacitor, etc., of the ECU 601 to be consumed. The control circuit 110 can measure the specified time using an internal timer (not shown). Alternatively, the control circuit 110 determines whether the power supply voltage of the ECU 601 has fallen below a reference voltage. The control circuit 110 can determine the power supply voltage of the ECU 601 by obtaining information from a voltage sensor (not shown) that detects the power supply voltage of the ECU 601. If the control circuit 110 determines that the first load has not lost power (step S202: NO), it returns to step S202.

[0038] When the control circuit 110 determines that the first load has lost power (step S202: YES), it turns on the first switch (step S203). Next, the control circuit 110 obtains the current value of the current flowing through the first load (step S204) and determines whether the current value exceeds the current threshold (step S205). When the control circuit 110 determines that the current value does not exceed the current threshold (step S205: NO), it completes the first load reset process. When the control circuit 110 determines that the current value exceeds the current threshold (step S205: YES), it turns off the first switch (step S206) and completes the first load reset process. At this time, the control circuit 110 may issue a warning that the abnormal current value condition has not been resolved by audio output, image display, etc.

[0039] After completing the first load reset process in step S107, the control circuit 110 determines whether or not there is an unselected first switch (step S108). If the control circuit 110 determines that there is an unselected first switch (step S108: YES), it returns to step S101. If the control circuit 110 determines that there is no unselected first switch (step S108: NO), it completes the first switch control process.

[0040] Next, the second switch control process performed by the microcomputer 200 will be described with reference to the flowchart in Figure 5. The second switch control process is the process of controlling the switch 310, which is the second switch. The second switch control process is performed periodically, for example, while the power to the microcomputer 200 is turned on.

[0041] First, the control circuit 210 of the microcomputer 200 selects the second switch (step S301). In this embodiment, the second switch is only switch 310, so the control circuit 110 selects switch 310 as the second switch. After completing the process in step S301, the control circuit 210 identifies the current vehicle state (step S302). After completing the process in step S302, the control circuit 210 determines whether or not stopping the operation of the first load is prohibited (step S303). For example, the control circuit 210 refers to the operation stop prohibition information stored in the memory circuit 220 to determine whether or not stopping the operation of the ECU 603 is prohibited in the current vehicle state.

[0042] If the control circuit 210 determines that stopping the operation of the first load is prohibited (step S303: YES), it turns on the second switch (step S304). If the control circuit 210 determines that stopping the operation of the first load is not prohibited (step S303: NO), it turns off the second switch (step S305). After completing the processing in step S304 or step S305, the control circuit 210 determines whether or not there is an unselected second switch (step S306). If the control circuit 210 determines that there is an unselected second switch (step S306: YES), it returns to step S301. If the control circuit 210 determines that there is no unselected second switch (step S306: NO), it completes the second switch control processing.

[0043] In this embodiment, if the current value detected by the current sensor 400 exceeds the current threshold, the first switch is temporarily turned off. As a result, the first load is reset, and the abnormal current value state of the first load may be resolved. Furthermore, since the power supply to other loads is not stopped, the functions of other loads are not impaired. According to this embodiment, it is possible to suppress over-discharge of the battery 10 mounted on the vehicle without impairing the functions of the vehicle as much as possible.

[0044] In this embodiment, for each of a plurality of first loads, a process of temporarily stopping the power supply is appropriately executed. That is, in this embodiment, the plurality of first loads can be individually reset. According to this embodiment, over-discharge of the battery 10 mounted on the vehicle can be further suppressed without significantly impairing the functions of the vehicle.

[0045] In this embodiment, while the current vehicle state is a vehicle state in which the power supply to the first load should be maintained, the second switch is maintained in the on state. In this case, even if the first switch is accidentally turned off, current flows to the first load through the second switch. According to this embodiment, it is possible to prevent the functions of the vehicle from being accidentally impaired.

[0046] In this embodiment, the control circuit 110 is implemented in the microcomputer 100, and the control circuit 210 is implemented in a different microcomputer 200 from the microcomputer 100. According to this embodiment, the probability that both the first switch and the second switch are accidentally turned off can be reduced.

[0047] In this embodiment, when the abnormal current value state of the first load is not eliminated during the reset of the first load, the power supply to the first load is stopped. According to this embodiment, over-discharge of the battery 10 mounted on the vehicle can be further suppressed.

[0048] (Embodiment 2) In Embodiment 1, an example in which only the first load is reset when an abnormal current value state of the first load is detected has been described. In this embodiment, an example in which the first load and a first load related to this first load are reset when an abnormal current value state of the first load is detected will be described. Regarding the same configurations and functions as those in Embodiment 1, the description will be omitted or simplified as appropriate.

[0049] Figure 6 is a configuration diagram of the in-vehicle system 2000A according to Embodiment 2. The in-vehicle system 2000A has the same configuration as the in-vehicle system 2000, except that it includes a heater 610 and a switch 700 instead of the ECU 601. The heater 610 is a device that generates heat by receiving power from the battery 10. A switch 301 and a shunt resistor 411 provided by the current sensor 401 are provided on the path connecting the battery 10 and the heater 610. The heater 610 is the first load. The switch 700 controls the supply of power from the battery 10 to the heater 610 according to the control by the ECU 602. The switch 700 is provided on the path connecting the battery 10 and the heater 610. The switch 700 is, for example, a mechanical relay.

[0050] The excessive current flowing from battery 10 to heater 610 could be due to a malfunction in heater 610, a malfunction in ECU 602, or a malfunction in switch 700. A malfunction in heater 610 could be a malfunction of heater 610 itself. A malfunction in ECU 602 could be thermal runaway or a program bug. For example, ECU 602 may mistakenly turn on switch 700 due to thermal runaway or a program bug. A malfunction in switch 700 could be, for example, a mechanical relay getting stuck in the ON position.

[0051] If an abnormal current value condition is detected in heater 610, simply resetting heater 610 may only resolve the malfunction of heater 610, and the abnormal current value condition of heater 610 may not be resolved. Therefore, in this embodiment, when an abnormal current value condition of heater 610 is detected, in addition to resetting heater 610, ECU 602 is also reset. With this configuration, in addition to the malfunction of heater 610, malfunctions of ECU 602, malfunctions of switch 700, etc., may be resolved, and the abnormal current value condition of heater 610 may be resolved.

[0052] In this embodiment, the memory circuit 120 stores load correspondence information that indicates the correspondence between first loads. For example, the load correspondence information is information that indicates, for each of the multiple first loads, other first loads that are associated with that first load. For example, the load correspondence information indicates that the first load associated with the heater 610 is the ECU 602, and that there are no first loads associated with the ECU 602.

[0053] In this embodiment, the plurality of first loads include a second load and a third load. The second load is the first load among the plurality of first loads that is in a current value abnormal state. The third load is the first load among the plurality of first loads that is associated with the second load. When the control circuit 110 detects the second load, it identifies the third load based on the load correspondence information stored in the memory circuit 120. In this embodiment, the second load is the heater 610, and the third load is the ECU 602 associated with the heater 610.

[0054] The control circuit 110 turns on the first switch corresponding to the second load in order to supply power to the second load. If the current value detected by the current sensor 400 corresponding to the second load exceeds the current threshold corresponding to the current vehicle state and the second load, the control circuit 110 temporarily turns off the first switch corresponding to the second load and the first switch corresponding to the third load. In this embodiment, if the current value detected by the current sensor 401 exceeds the current threshold corresponding to the current vehicle state and the heater 610, the control circuit 110 temporarily turns off the switch 301 corresponding to the heater 610 and the switch 302 corresponding to the ECU 602.

[0055] Referring to Figure 7, the first load reset process according to this embodiment will be described. The first load reset process according to this embodiment is a process that resets the second load, which is the first load, and the third load, which is the first load. The first load reset process is executed in place of the process in step S107 in the first switch control process shown in Figure 3.

[0056] First, the control circuit 110 turns off the first switch corresponding to the second load (step S401) and determines whether the second load has lost power (step S402). The first switch corresponding to the second load is a first switch located on the path connecting the battery 10 and the second load. In other words, the control circuit 110 turns off the switch 301 corresponding to the heater 610 and determines whether the heater 610 has lost power. If the control circuit 110 determines that the second load has not lost power (step S402: NO), it returns to step S402.

[0057] When the control circuit 110 determines that the second load has lost power (step S402: YES), it turns on the first switch corresponding to the second load (step S403) and determines whether or not there is a third load associated with the second load (step S404). In other words, when the control circuit 110 determines that the heater 610 has lost power, it turns on the switch 301 corresponding to the heater 610 and determines whether or not there is an ECU 602 associated with the heater 610. For example, the control circuit 110 refers to the load correspondence information stored in the memory circuit 120 to determine whether or not there is a third load associated with the second load.

[0058] If the control circuit 110 determines that there is a third load associated with the second load (step S404: YES), it turns off the first switch associated with the third load (step S405) and determines whether the third load has lost power (step S406). In other words, if the control circuit 110 determines that there is an ECU 602 associated with the heater 610, it turns off the switch 302 associated with the ECU 602 and determines whether the ECU 602 has lost power. If the control circuit 110 determines that the third load has not lost power (step S406: NO), it returns to step S406.

[0059] When the control circuit 110 determines that the third load has lost power (step S406: YES), it turns on the first switch corresponding to the third load (step S407). In other words, when the control circuit 110 determines that the ECU 602 has lost power, it turns on the switch 302 corresponding to the ECU 602. When the control circuit 110 determines that there is no third load associated with the second load (step S404: NO), or when it has completed the process in step S407, it obtains the current value of the current flowing to the second load (step S408). For example, the control circuit 110 obtains current value information from the current sensor 401 and obtains the current value of the current flowing from the battery 10 to the heater 610.

[0060] After completing the process in step S408, the control circuit 110 determines whether the current value exceeds the current threshold (step S409). If the control circuit 110 determines that the current value does not exceed the current threshold (step S409: NO), it completes the first load reset process. If the control circuit 110 determines that the current value exceeds the current threshold (step S409: YES), it turns off the second switch (step S410) and completes the first load reset process.

[0061] In this embodiment, if the current value detected by the current sensor 400 corresponding to the second load exceeds the current threshold corresponding to the current vehicle state and the second load, the first switch corresponding to the second load and the first switch corresponding to the third load are temporarily turned off. In this embodiment, there is a high probability that the abnormal current value state of the second load will be resolved. Therefore, according to this embodiment, it is possible to further suppress over-discharge of the battery 10 mounted on the vehicle without impairing the functions of the vehicle as much as possible.

[0062] (Modifications) Although embodiments have been described above, various modifications and applications are possible. It is arbitrary which parts of the configuration, function, and operation described in the above embodiments are adopted. In addition to the configuration, function, and operation described above, further configurations, functions, and operations may be adopted. Furthermore, the configurations, functions, and operations described in the above embodiments can be freely combined.

[0063] Embodiments 1 and 2 described examples where the first load on which the first switch is provided is an ECU, a heater, etc. The first load may be a load other than an ECU or a heater. For example, various sensors such as a vehicle speed sensor, an acceleration sensor, and a temperature sensor can be assumed as the first load. Embodiment 1 described an example where there is one first load on which the second switch is provided. There may be no first load on which the second switch is provided, or there may be two or more.

[0064] Embodiment 1 describes an example in which the first switch is a p-channel MOSFET and the second switch is an n-channel MOSFET. The first and second switches may be other semiconductor switches or mechanical relays. Embodiment 2 describes an example in which switch 700 is a mechanical relay. Switch 700 may be a semiconductor switch. Embodiment 2 describes an example in which the first load that controls the supply of power to the second load is set to a third load. Various first loads that may affect the current flowing from the battery 10 to the second load may be set to the third load.

[0065] In Embodiment 1, an example was described in which the first integrated circuit on which the first control circuit is mounted and the second integrated circuit on which the second control circuit is mounted are microcomputers in which the processor executes a program and performs each process. The first integrated circuit and the second integrated circuit are not limited to microcomputers. For example, the first integrated circuit and the second integrated circuit may be ASICs (Application Specific Integrated Circuits), FPGAs (Field-Programmable Gate Arrays), etc.

[0066] This invention allows for various embodiments and modifications without departing from the broad spirit and scope of the invention. Furthermore, the embodiments described above are for illustrative purposes only and do not limit the scope of the invention. In other words, the scope of the invention is indicated not by the embodiments, but by the claims. Various modifications made within the scope of the claims and the equivalent scope of the meaning of the invention are considered to be within the scope of the invention.

[0067] 10 Batteries, 20 Generators, 100, 200 Microcomputers, 110, 210 Control circuits, 120, 220 Memory circuits, 130, 230 Input / Output circuits, 300, 301, 302, 303, 310, 700 Switches, 400, 401, 402, 403 Current sensors, 410, 411, 412, 413 Shunt resistors, 420, 421, 422, 423 Voltage sensors, 500, 501, 502, 503 Fuses, 600, 601, 602, 603 ECUs, 610 Heaters, 1000 Over-discharge suppression systems, 2000, 2000A In-vehicle systems.

Claims

1. An over-discharge suppression system comprising: a first switch provided on a path connecting a battery that supplies power to multiple loads on a vehicle to a first load among the multiple loads; a current sensor that detects the current value of the current flowing between the battery and the first load; and a first control circuit that controls the first switch and temporarily turns off the first switch if the current value detected by the current sensor when the first switch is ON exceeds a current threshold corresponding to the current state of the vehicle and the first load.

2. The over-discharge suppression system according to claim 1, wherein the plurality of loads includes a plurality of first loads, and each of the plurality of first loads is provided with a first switch and a current sensor, and the first control circuit performs a process to temporarily turn off the first switch for each of the plurality of first loads when the current value exceeds the current threshold when the first switch is turned on.

3. The over-discharge suppression system according to claim 2, wherein the plurality of first loads include a second load and a third load associated with the second load, and the first control circuit temporarily turns off the first switch corresponding to the second load and the first switch corresponding to the third load when the current value detected by the current sensor corresponding to the second load exceeds a current threshold corresponding to the current vehicle state and the second load while the first switch corresponding to the second load is turned on.

4. An over-discharge suppression system according to any one of claims 1 to 3, comprising: a second switch provided in parallel with the first switch in the aforementioned path; and a second control circuit that controls the second switch and turns on the second switch while the current vehicle state is a vehicle state in which power should be supplied to the first load.

5. The over-discharge suppression system according to claim 4, wherein the first control circuit is mounted on a first integrated circuit, and the second control circuit is mounted on a second integrated circuit different from the first integrated circuit.

6. The over-discharge suppression system according to any one of claims 1 to 5, wherein the first control circuit continuously turns off the first switch if the current value detected by the current sensor exceeds the current threshold even after the first switch has been temporarily turned off and then turned on again.

7. An over-discharge suppression method comprising: a first control circuit controlling a first switch provided on a path connecting a battery that supplies power to a plurality of loads provided by a vehicle to a first load among the plurality of loads; and when the first control circuit is turned on, if the current value of the current flowing between the battery and the first load exceeds a current threshold corresponding to the current state of the vehicle and the first load, the first control circuit temporarily turns off the first switch.

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