Power supply system and control method for power supply system

Abstract

To provide a power supply system capable of suppressing reduction in a charging voltage of an additional battery.SOLUTION: A power supply system mounted on a vehicle having an automatic operation mode comprises: a first load circuit 1 connected with a load 12 operating with power from a lead battery 11; a second load circuit 2 connected with a load 25 operating with power from the lead battery 11 or a lithium-ion battery 21, the load 25 being needed for continuing an automatic operation mode; and a main relay 4 provided on a feeder line 3, making conductive or cutting off between the first load circuit 1 and the second load circuit 2. A current path of a downstream side of the main relay 4 includes a path for applying a current flowing from the first load circuit 1 to the main relay 4 from a branch point 27a located at the downstream side of the main relay 4 to the load 25, and a path for applying from the branch point 27a to the lithium-ion battery 21. A current value that can make conductive the path from the branch point 27a to the load 25 is higher than a current value that can make conductive the path from the branch point 27a to the lithium-ion battery 21.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a power supply system and a method for controlling a power supply system. [Background technology]

[0002] A control device for an autonomous vehicle power supply that has a circuit interruption mechanism between a first load circuit powered by the main battery and a second load circuit powered by an additional battery is known (Patent Document 1). A load required for the driver to continue normal driving mode is connected to the first load circuit, and an autonomous driving function load that is required for the autonomous driving mode to continue and requires voltage maintenance is connected to the second load circuit. In this method for controlling the autonomous vehicle power supply, when the circuit interruption mechanism is connected, if it is determined based on the load state detected on the second load circuit that power will be drawn from the additional battery to the first load circuit, the circuit interruption mechanism is shut off. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-177857 Summary of the Invention [Problem to be solved by the invention]

[0004] In the power supply device for an autonomous vehicle described in Patent Document 1, the second load circuit is configured to connect a load uniformly regardless of the amount of current consumed by the load, which results in a problem that sufficient voltage is not applied to the additional battery, resulting in an insufficient charge level in the additional battery.

[0005] The problem to be solved by the present invention is to provide a power supply system that suppresses a drop in the charging voltage of an additional battery. [Means for solving the problem]

[0006] The present invention provides a vehicle control system including a first load circuit to which a first load is connected, a second load circuit to which a second load necessary for continuing an automatic driving mode is connected, and a first circuit interrupting mechanism that establishes or interrupts conduction between the first load circuit and the second load circuit, On the other hand The current path on the side is for the current flowing from the first load circuit to the first circuit interrupter. On the other hand a first path from a branch point located on the side to a second load, and a second path from the branch point to an additional battery; The branch point is located on the wiring connecting the first circuit interrupter and the additional battery, closer to the first circuit interrupter than to the additional battery. This solves the above problem. [Effects of the Invention]

[0007] According to the present invention, it is possible to suppress a drop in the charging voltage of the additional battery. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram of the configuration of a power supply system according to this embodiment. [Figure 2] FIG. 2 is a conceptual diagram for explaining the connection configuration of the power supply system shown in FIG. [Figure 3] FIG. 3 is a conceptual diagram for explaining a connection configuration of a power supply system shown as a comparative example. [Figure 4] FIG. 4 is a schematic diagram of the configuration of a relay module provided in a power supply system according to a modified example of this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A power supply system and a control method for a power supply system according to embodiments of the present invention will be described below with reference to the accompanying drawings.

[0010] FIG. 1 is a schematic diagram of a power supply system 100 according to this embodiment. In this embodiment, a vehicle equipped with the power supply system 100 will be described as an example in which the drive source is an engine and the vehicle has an autonomous driving control function. A vehicle equipped with an autonomous driving control function has two driving modes: a normal driving mode and an autonomous driving mode. When set to the normal driving mode, the vehicle is driven by driving operations (steering, accelerator, brake, etc.) performed by the driver. On the other hand, when set to the autonomous driving mode, the vehicle is driven by driving operations performed by a driving assistance device (not shown) in addition to the driver.

[0011] In the autonomous driving mode, the content of the driving assistance provided by the autonomous driving control function may vary depending on the driving assistance level. The driving assistance level indicates the degree of intervention when the driving assistance device assists vehicle driving using the autonomous driving control function. The higher the driving assistance level, the lower the driver's contribution to vehicle driving. Specifically, the driving assistance level can be set using definitions based on SAE J3016 of the Society of Automotive Engineers (SAE). In this embodiment, the driving assistance level provided by the driving assistance device is described as driving assistance level 2. Furthermore, this embodiment describes an example of a vehicle having a mode in which the vehicle drives autonomously without the driver touching the steering wheel (also referred to as hands-off mode). In hands-off mode, the driving assistance device performs some driving tasks on behalf of the driver, but the driver must regain control of the vehicle and prepare to drive manually when requested by the driving assistance device. In addition, in hands-off mode, redundant functions are required to continue autonomous driving until the driver performs driving operations in response to a request from the driving assistance device. As an example of a redundant function, for example, a vehicle having an autonomous driving mode is provided with an additional battery that functions as a backup power supply for the load required for the autonomous driving control function.

[0012] However, installing an additional battery presents a problem in that the additional battery may be discharged due to the dark current of a load connected to the additional battery while the vehicle's ignition switch is off. If the additional battery discharges due to the dark current of the load, the remaining battery charge of the additional battery may decrease, and the additional battery may not be able to supply the load with the power necessary to continue autonomous driving in autonomous driving mode, and may not function as a backup power supply source. The power supply system and power supply system control method according to the present invention, using the configuration and method described below, can prevent the additional battery from discharging due to the dark current of the load and supply the load with the power necessary to continue autonomous driving in autonomous driving mode. Hereinafter, the above-mentioned driving assistance device will be described as a configuration included in an Advanced Driver Assistance System (ADAS).

[0013] As shown in FIG. 1, the power supply system 100 includes a first load circuit 1, a second load circuit 2, a power feeder 3, a main relay 4, an additional relay 5, and a controller 6.

[0014] The first load circuit 1 is a load circuit that operates using power from a lead battery 11 (main battery) or an alternator 14, and to which a first load necessary for continuing the normal operation mode is connected. In this embodiment, as shown in FIG. 1 , the first load circuit 1 includes the lead battery 11, a load actuator 12, a starter motor 13, and an alternator 14, all connected to a power supply line 3. Examples of the first load necessary for continuing the normal operation mode include the load actuator 12 and the starter motor 13.

[0015] The lead battery 11 is a secondary battery that has conventionally been installed in engine vehicles as a main battery. The lead battery 11 is charged by an alternator 14, which functions as a generator, so that the remaining battery charge does not decrease. The alternator 14 generates electricity using a rotation drive mechanism (not shown) driven by the engine, and charges the lead battery 11 so that the remaining battery charge is maintained at or above a predetermined remaining battery charge.

[0016] The load actuator 12 is an auxiliary device that operates using power from the lead battery 11 or power generated by the alternator 14. Examples of the load actuator 12 include an electric motor that drives a compressor of an air conditioner, a headlight, etc. When the ignition switch 68 of the vehicle is turned on (hereinafter also referred to as a state in which the vehicle is ready to run), power stored in the lead battery 11 or power generated by the alternator 14 is supplied to the load actuator 12. On the other hand, when the ignition switch 68 of the vehicle is turned off (hereinafter also referred to as a parked state in which the vehicle is ready to run), power stored in the lead battery 11 is supplied to the load actuator 12. The state in which the vehicle is ready to run indicates a state that is independent of the vehicle speed and includes a state in which the vehicle is running and a state in which the vehicle is stopped.

[0017] The starter motor 13 is a motor for starting the engine when the vehicle starts and restarts the engine when the vehicle is stopped at idle.

[0018] The second load circuit 2 is a load circuit that operates using power from the lead battery 11 or the lithium-ion battery 21 (additional battery) and to which a second load necessary for continuing the autonomous driving mode is connected. In this embodiment, as shown in FIG. 1 , the second load circuit 2 includes an EPS actuator 22, an ABS actuator 23, an ADAS actuator 24, a load 26, and a current sensor 61, all connected to a power supply line 3. Examples of the second load necessary for continuing the autonomous driving mode include the EPS actuator 22, the ABS actuator 23, and the ADAS actuator 24. The range of the input voltage to these actuators is determined according to the specifications of each actuator, and in order to continue operating the actuators according to the specifications, the input voltage to each actuator needs to be maintained within the input voltage range determined by the specifications.

[0019] The lithium-ion battery 21 is a secondary battery added as a new power source to the lead battery 11 to continue the autonomous driving control function of the vehicle. In other words, the lithium-ion battery 21 is a backup power supply that supplies power to each load included in the second load circuit 2 to continue autonomous driving in the autonomous driving mode. Charging and discharging of the lithium-ion battery 21 are controlled by a battery management system (BMS). In the example of FIG. 1 , when the main relay 4 and the additional relay 5 are in the on state, conduction is established between the lithium-ion battery 21 and the first load circuit 1, and the battery management system charges the lithium-ion battery 21 with power generated by the alternator 14 (generator). When the controller 6 determines that the vehicle's driving mode is the autonomous driving mode, if the circuit voltage of the second load circuit 2 falls outside a predetermined voltage range, the main relay 4 switches from on to off. However, because the additional relay 5 remains on, conduction is maintained between the additional battery and the second load circuit before and after the main relay 4 switches from on to off. The battery management system outputs the power charged in the lithium ion battery 21 to the second load, thereby discharging the lithium ion battery 21. Once the main relay 4 is switched from on to off in the autonomous driving mode, the main relay 4 remains in the off state until the autonomous driving mode is switched to the normal driving mode, and therefore the lithium ion battery 21 cannot be charged with the power generated by the alternator 14. For this reason, the capacity of the lithium ion battery 21 is set to an appropriate capacity so that the time during which driving in the autonomous driving mode continues is at least equal to or longer than the required time, for example.

[0020] Furthermore, the lithium ion battery 21 has a characteristic that its internal resistance is smaller than that of the lead battery 11. Therefore, for example, even when the EPS actuator 22 operates and consumes a large current, the voltage can be maintained high.

[0021] The EPS actuator 22 is an EPS motor that generates an electric assist force and is a load that must operate in autonomous driving mode. The EPS actuator 22 is used in an electric power steering system (not shown) that electrically assists the force required for steering operation to reduce steering effort. Here, "EPS" is an abbreviation for "Electric Power Steering."

[0022] The ABS actuator 23 is a pump motor and electromagnetic valve that drive a hydraulic pump, and is a load that must operate in the automatic driving mode. The ABS actuator 23 has an electric hydraulic pump and is used in a brake fluid pressure control system (not shown) that independently controls the hydraulic pressure of each wheel cylinder based on hydraulic fluid from the master cylinder and hydraulic pump. Here, "ABS" is an abbreviation for "Antilock Brake System."

[0023] The ADAS actuator 24 is an actuator that performs various driving operation assistance functions to assist the driver in driving, and is a load that must operate in an autonomous driving mode. The ADAS actuator 24 is used in an advanced driver assistance system 70.

[0024] The EPS actuator 22, the ABS actuator 23, and the ADAS actuator 24 are loads necessary for driving in the autonomous driving mode. On the other hand, the load 26 is a load that is not necessary for driving in the autonomous driving mode. The current consumed by the load 26 is smaller than the current consumed by the loads necessary for driving in the autonomous driving mode, such as the EPS actuator 22. An example of the load 26 is an external communication device.

[0025] The power supply line 3 is a wire harness for supplying power and electrically connects the first load circuit 1 and the second load circuit 2. Power is supplied via the power supply line 3 to the load actuator 12 included in the first load circuit 1 and the EPS actuator 22, the ABS actuator 23, and the ADAS actuator 24 included in the second load circuit 2.

[0026] The main relay 4 (first circuit interrupter) is provided on the power supply line 3 between the first load circuit 1 and the second load circuit 2, and is a circuit interrupter for establishing or interrupting electrical continuity between the first load circuit 1 and the second load circuit 2. One terminal of the main relay 4 is connected to the power supply line 3 on the first load circuit 1 side, and the other terminal of the main relay 4 is connected to the power supply line 3 on the second load circuit 2 side. In this embodiment, a normally open type relay is used as the main relay 4. Examples of the main relay 4 include a mechanical relay (also called a mechanical relay) and a semiconductor relay. A mechanical relay has contacts and mechanically opens and closes the contacts by electromagnetic action to switch on and off. A semiconductor relay does not have contacts and is composed of semiconductors or electronic components such as a metal-oxide-semiconductor field-effect transistor (MOSFET), and switches on and off using an electrical signal. In this embodiment, the main relay 4 will be described as an example, which is a semiconductor relay having a self-shutdown / connection function that autonomously switches on and off for overvoltage protection and overcurrent protection.

[0027] The main relay 4 receives an open / close control signal from the controller 6, and the main relay 4 turns on or off in response to the open / close control signal. The controller 6 also receives a continuity maintenance command or a release command from the main relay 4, separate from the open / close control signal. Once the continuity maintenance command is received, the main relay 4 maintains its on state until a release command is received, regardless of whether the open / close control signal is received. When a release command is received after the continuity maintenance command, the main relay 4 releases its on state and turns on or off again in response to the open / close control signal. In the case where the main relay 4 is a semiconductor relay, as in this embodiment, the open / close control signal is, for example, a switching signal for switching a semiconductor, such as a switching element, from on to off or from off to on. The continuity maintenance command is, for example, a signal for disabling the self-shutdown / connection function and maintaining the on state to prevent the self-shutdown / connection function from switching from on to off. The release command is, for example, a signal for enabling the self-shutdown / connection function. An example of the self-shutdown / connection function is a protection function that switches the main relay 4 from on to off when an abnormal voltage is applied between the terminals of the main relay 4 (between the terminal connected to the first load circuit 1 and the terminal connected to the second load circuit 2). The abnormal voltage is, for example, a predetermined overvoltage defined in the specifications of the main relay 4. Another example of the self-shutdown / connection function is a protection function that switches the main relay 4 from on to off when an abnormal current flows through the main relay 4 (the current flowing from the first load circuit 1 side to the second load circuit 2 side). The abnormal current is, for example, a predetermined overcurrent defined in the specifications of the main relay 4. In the following description, "the main relay 4 is on (on state)" refers to a state in which the terminals of the main relay 4 are electrically connected, and "the main relay 4 is off (off state)" refers to a state in which the terminals of the main relay 4 are electrically isolated (disconnected).

[0028] The additional relay 5 is electrically connected to the power supply line 3 on the second load circuit 2 side, and is a battery interrupter mechanism for establishing or interrupting conduction between the lithium ion battery 21 and the EPS actuator 22, the ABS actuator 23, and the ADAS actuator 24. One terminal of the additional relay 5 is connected to the lithium ion battery 21, and the other terminal of the additional relay 5 is connected to the power supply line 3 on the second load circuit 2 side via a current sensor 61. In this embodiment, a normally closed type relay is used as the additional relay 5. As with the main relay 4, examples of the additional relay 5 include a mechanical relay and a semiconductor relay. In this embodiment, a mechanical relay will be used as an example of the additional relay 5.

[0029] The additional relay 5 receives an open / close control signal from the controller 6, and turns on or off in response to the open / close control signal. The controller 6 also receives a continuity maintenance command or a release command from the additional relay 5, separate from the open / close control signal. Once a continuity maintenance command is input to the additional relay 5, the additional relay 5 maintains its on state until a release command is input, regardless of whether or not the open / close control signal is input. When a release command is input after the open / close command, the additional relay 5 releases its on state and turns on or off again in response to the open / close control signal. In the case where the additional relay 5 is a mechanical relay, as in this embodiment, the open / close control signal is, for example, a voltage application signal for generating a magnetic field to switch the relay from off to on, or a voltage stop signal for eliminating the magnetic field to switch the relay from on to off. The continuity maintenance command is, for example, a forced voltage application signal for maintaining the on state by continuing to generate a magnetic field. In the following description, "additional relay 5 on (on state)" refers to a state in which the terminals of additional relay 5 are electrically connected, and "additional relay 5 off (off state)" refers to a state in which the terminals of additional relay 5 are electrically insulated (cut off).

[0030] Furthermore, in this embodiment, the conduction or interruption of the additional relay 5 by the open / close control signal is described as an example, but the conduction or interruption between the lithium ion battery 21 and each load included in the second load circuit 2 may be performed by other methods. For example, the power supply system may be configured such that a DC-DC converter is provided between the lithium ion battery 21 and the additional relay 5, and the voltage of the lithium ion battery 21 is boosted and output by the DC-DC converter. In this configuration, the DC-DC converter alone can function as a relay, so the conduction or interruption between the lithium ion battery 21 and the additional relay 5 may be performed by controlling the DC-DC converter.

[0031] Next, the controller 6 will be described. The controller 6 is an electronic control unit (ECU) configured by a computer equipped with hardware and software, and having a memory storing programs and a CPU for executing the programs stored in the memory. Note that an MPU, DSP, ASIC, FPGA, etc. can be used as the operating circuit instead of or in addition to the CPU. The controller 6 realizes various functions by the CPU executing programs stored in the ROM. The functions realized by the controller 6 will be described later.

[0032] 1, various pieces of information are input to the controller 6 from a current sensor 61, an automatic driving mode switch 62, a first voltage sensor 63, a second voltage sensor 64, a battery voltage sensor 65, a brake switch 66, a torque sensor 67, an ignition switch 68, a vehicle speed sensor 69, and an advanced driver assistance system 70. The controller 6 also executes processing based on the input information, and outputs an open / close control signal, a maintain continuity command, or a release command to the main relay 4 and / or the additional relay 5 based on the execution result. The controller 6 also executes processing based on the input information, and outputs control commands to a display device 71 and a buzzer 72 based on the execution result.

[0033] The current sensor 61 is provided between the main relay 4 and the additional relay 5, and detects the direction of the current flowing to the lithium ion battery 21. The detection result by the current sensor 61 is output to the controller 6.

[0034] The autonomous driving mode switch 62 is a switch that can be operated by the driver and is a switch for starting the autonomous driving mode. When the vehicle's driving mode is the normal driving mode, the autonomous driving mode is started when the driver turns on the autonomous driving mode switch 62. When the vehicle's driving mode is the autonomous driving mode, the normal driving mode is started when the driver turns off the autonomous driving mode switch 62. There are no particular limitations on the form and installation position of the autonomous driving mode switch 62, but one example of the autonomous driving mode switch 62 is a button that is provided on the steering wheel and can be operated by the driver. Information on the driver's operation of the autonomous driving mode switch 62 is output to the controller 6 and the advanced driving assistance system 70.

[0035] The first voltage sensor 63 detects the circuit voltage of the first load circuit 1. The circuit voltage of the first load circuit 1 is the voltage of the power supply line 3 on the first load circuit 1 side. The first voltage sensor 63 is connected in parallel to each component included in the first load circuit 1, for example. The detection result by the first voltage sensor 63 is output to the controller 6. Furthermore, when a semiconductor relay having a self-shutoff / connection function is used as the main relay 4 as in this embodiment, the detection result by the first voltage sensor 63 is also output to the main relay 4.

[0036] The second voltage sensor 64 detects the circuit voltage of the second load circuit 2. The circuit voltage of the second load circuit 2 is the voltage of the power supply line 3 on the second load circuit 2 side. The second voltage sensor 64 is connected in parallel to, for example, each load included in the second load circuit 2. The detection result by the second voltage sensor 64 is output to the controller 6. Furthermore, when a semiconductor relay having a self-shutoff / connection function is used as the main relay 4 as in this embodiment, the detection result by the second voltage sensor 64 is also output to the main relay 4.

[0037] The battery voltage sensor 65 detects the battery voltage of the lithium ion battery 21. The detection result by the battery voltage sensor 65 is output to the controller 6. The brake switch 66 detects the braking operation by the driver. Information on the braking operation by the driver detected by the brake switch 66 is output to the controller 6. The torque sensor 67 detects the steering torque applied to the steering shaft due to the steering operation by the driver. Information on the steering operation by the driver detected by the torque sensor 67 is output to the controller 6.

[0038] The ignition switch 68 is a switch for turning the vehicle's drive source on and off. In the case of a vehicle with an engine as the drive source, as in this embodiment, when the ignition switch 68 is turned on, the engine starts and the vehicle is ready to run. On the other hand, when the ignition switch 68 is turned off, the engine stops and the vehicle is parked. Examples of the ignition switch 68 include an engine key type in which the occupant starts the vehicle by turning the vehicle key inserted into the keyhole, and a push-start type in which the occupant starts the vehicle by pressing a button. The ignition switch 68 may also be provided with an indicator (ON indicator) for starting the vehicle's drive source or an indicator (OFF indicator) for stopping the vehicle's drive source, as well as an indicator (ACC indicator) for energizing electrical systems unrelated to vehicle running, such as car navigation and audio, and an indicator (START indicator) for driving the starter motor 13 to start the air conditioning system. Information regarding the driver's operation of the ignition switch 68 is output to the controller 6. The vehicle speed sensor 69 detects the speed of the vehicle. The detection result by the vehicle speed sensor 69 is output to the controller 6.

[0039] The advanced driver assistance system 70 is a system that performs automatic brake control, auto-cruise control, lane keeping control, etc. to assist the driver in driving. The processing results of the advanced driver assistance system 70 are output to the controller 6. The display device 71 notifies the driver that some kind of abnormality has occurred in the autonomous driving mode and displays a warning display to urge the driver to perform driving operations. The buzzer 72 notifies the driver that some kind of abnormality has occurred in the autonomous driving mode and outputs a warning sound to urge the driver to perform driving operations.

[0040] The controller 8 switches the main relay 4 and the additional relay on and off depending on the state of the vehicle, the driving mode, or the circuit voltage of the second load circuit 2. For example, when the vehicle is in a parked state, the controller 8 keeps the main relay 4 in an on state and the additional relay 5 in an off state. Then, when the vehicle transitions from the parked state to a drivable state, the controller 8 switches the additional relay 5 from off to on while keeping the main relay 4 in an on state.

[0041] When the vehicle is in the normal driving mode, if the circuit voltage of the second load circuit 2 is within a predetermined voltage range, the controller 8 maintains the main relay 4 and the additional relay 5 in the ON state. On the other hand, if the circuit voltage of the second load circuit 2 is outside the predetermined voltage range, the controller 8 maintains the main relay 4 in the ON state and turns the additional relay 5 off.

[0042] Furthermore, when the vehicle's driving mode is the autonomous driving mode, if the circuit voltage of the second load circuit 2 is within a predetermined voltage range, the controller 8 turns on the main relay 4 and the additional relay 5. On the other hand, when the vehicle's driving mode is the autonomous driving mode, if the circuit voltage of the second load circuit 2 is outside the predetermined voltage range, the controller 8 turns off the main relay 4 and turns on the additional relay 5.

[0043] Here, there is a concern that in the autonomous driving mode, additional relay 5 may suddenly turn off for some reason, resulting in a disconnection between lithium ion battery 21, which is the backup power supply source, and the loads included in second load circuit 2. However, in the autonomous driving mode, additional relay 5 remains on, preventing a disconnection between lithium ion battery 21 and the loads included in second load circuit 2. In other words, according to power supply system 100 and the control method for power supply system 100 of the present embodiment, it is possible to prevent a decrease in the remaining battery capacity of lithium ion battery 21 due to dark current discharge, and to ensure backup operation by lithium ion battery 21.

[0044] Next, the connection configuration of the power supply system 100 will be described with reference to Figures 2 and 3. Figure 2 is a conceptual diagram for explaining the connection configuration of the power supply system 100 according to this embodiment. Figure 3 is a conceptual diagram for explaining the connection configuration of the power supply system 100 according to a comparative example. Note that part of the configuration of the power supply system 100 shown in Figure 1 is omitted in Figure 2. The first load circuit 1 is connected upstream of the main relay 4, and the second load circuit 2 is connected downstream of the main relay 4.

[0045] The first load circuit 1 includes a lead battery 11, a load 12, etc., as well as a DC-DC converter 15 and a wiring box 16. The DC-DC converter 15 boosts the voltage generated by the alternator 14 and outputs it to the lead battery 11 and the main relay 4. The wiring box 16 branches the wiring on the output side of the DC-DC converter 15 to the lead battery 11, the load 12, and the main relay 4.

[0046] The second load circuit 2 includes wiring boxes 27 and 28 in addition to the lithium-ion battery 21 and the load 26. The load 25 (second load) includes an EPS actuator 22, an ABS actuator 23, and an ADAS actuator 24, and is a load necessary for the vehicle to travel in autonomous driving mode. In addition to the EPS actuator 22, the load 25 also includes a steering wheel, sensors for detecting the conditions around the vehicle, and the like. The wiring box 27 branches the current path downstream of the main relay 4 into a path for passing current to the load 25 and a path for passing current to the lithium-ion battery 21 via the additional relay 5. The wiring box 27 has a branch point 27a. The power supply line 3 branches from the branch point 27a into a branch wiring, and includes a wiring 31 connecting the branch point 27a and the load 25 and a wiring 32 connecting the branch point 27a and the lithium-ion battery 21. The wiring box 27 is located close to the main relay 4. That is, the branch point 27 a is located on the wiring connecting the main relay 4 and the lithium ion battery 21 closer to the main relay 4 than the lithium ion battery 21 .

[0047] The wiring box 28 is provided between the wiring box 27 and the lithium ion battery 21, and between the wiring box 27 and the load 26. The wiring box 28 is connected to the wiring 32 and has a branch point 28a, which branches into a path for flowing current from the branch point 28a to the load 26 and a path for flowing current from the branch point 28a to the lithium ion battery 21.

[0048] The first load circuit 1, main relay 4, load 25, and wiring box 27 are provided in the front of the vehicle. Meanwhile, the additional relay 5, lithium ion battery 21, load 26, and wiring box 28a are provided in the rear of the vehicle. In particular, the lithium ion battery 21 is provided in the rear of the vehicle to reduce the risk of leakage from the lithium ion battery 21 when the vehicle is subjected to an external impact. Meanwhile, the alternator 14, which generates power to charge the lithium ion battery 21, the main relay 4, and the load 25 are also provided in the front of the vehicle. Therefore, a long harness is used to make up the wiring 32 in order to supply the power generated by the alternator 14, which is located in the front of the vehicle, to the lithium ion battery 21, which is located in the rear of the vehicle.

[0049] Here, the relationship between the connection topology of the power supply system 100 and the charging voltage of the lithium ion battery 21 will be explained. Due to battery performance, the lithium ion battery 21 can be charged at a higher voltage than the lead battery 11. Furthermore, since the cost of the lithium ion battery 21 is high, it is desirable to charge the lithium ion battery 21 at as high a voltage as possible, increase the charging capacity of the lithium ion battery 21, and minimize the number of cells installed in the vehicle. For this reason, it is desirable to configure the connection topology of the power supply system 100 so that as high a voltage as possible is applied to the lithium ion battery 21 during charging. On the other hand, it is necessary to charge the lead battery 11 so that the charging voltage of the lead battery does not exceed the upper limit voltage of the lead battery.

[0050] 2, in the power supply system 100, the DC-DC converter 15 that increases the voltage generated by the alternator 14 and the lead battery 11 are located at the front of the vehicle and upstream of the main relay 4. On the other hand, the lithium ion battery 21 is located at the rear of the vehicle and downstream of the main relay 4. Therefore, in order to apply as high a voltage as possible to the lithium ion battery 21 while keeping the charging voltage of the lead battery 11 below an upper limit voltage during battery charging, it is necessary to suppress the voltage drop in the wiring between the main relay 4 and the lithium ion battery 21.

[0051] Furthermore, load 25 included in second load circuit 2 is a load necessary for the vehicle to travel in an autonomous driving mode and consumes a large amount of current. For example, to operate load 25 using power supplied from first load circuit 1 to second load circuit 2 via main relay 4, there is also a connection configuration (a connection configuration of a comparative example) in which load 25 is connected to branch point 28a of wiring box 28 instead of branch point 27a of wiring box 27, as shown in Fig. 3. That is, in the connection configuration of Fig. 3, the loads included in second load circuit 2 are uniformly connected to power feeder 3 regardless of the magnitude of their current consumption.

[0052] In the connection configuration of the comparative example, load 25 operates with a large current, so a large current needs to flow in the wiring from the downstream side of relay 4 to wiring box 28. As a result, the voltage drop in the wiring from the downstream side of relay 4 to wiring box 28 is large. Furthermore, as described above, a long harness is connected from the downstream side of relay 4 to wiring box 28, so the voltage drop becomes even larger. If the voltage drop between relay 4 and lithium ion battery 21 becomes large, the charging voltage of lithium ion battery 21 becomes small, and lithium ion battery 21 cannot be charged to a sufficient amount.

[0053] On the other hand, in this embodiment, the load 25 is connected to a branch point 27a located near the main relay 4. The current flowing from the first load circuit 1 to the main relay 4 branches at the branch point 27a, with a large current flowing through the load 25, which consumes a large current, and a small current flowing through the lithium-ion battery 21. In other words, the current value that can be conducted through the current path of the wiring 31 is higher than the current value that can be conducted through the current path of the wiring 32. In other words, the current path downstream of the main relay 4 is configured so that the current flowing from the branch point 27a to the load 25 is higher than the current flowing from the branch point 27a to the lithium-ion battery 21. This makes it possible to reduce the voltage drop in the wiring from the branch point 27a to the lithium-ion battery 21. As a result, the charging voltage of the lead battery 11 can be kept below the upper limit voltage, while suppressing a drop in the charging voltage of the lithium-ion battery 21.

[0054] As described above, this embodiment includes a first load circuit 1 connected to a load 12 powered by a lead battery 11; a second load circuit 2 connected to a load 25 powered by the lead battery 11 or the lithium-ion battery 21 and required for maintaining the autonomous driving mode; and a main relay 4 provided on a power supply line 3 for establishing or interrupting conduction between the first load circuit 1 and the second load circuit 2. The current path downstream of the main relay 4 includes a path (corresponding to the "first path" of the present invention) for directing current flowing from the first load circuit 1 to the main relay 4 from a branch point 27a located downstream of the main relay 4 to the load 25, and a path (corresponding to the "second path" of the present invention) for directing current flowing from the branch point 27a to the lithium-ion battery 21. The current value that can be conducted through the path from the branch point 27a to the load 25 is higher than the current value that can be conducted through the path from the branch point 27a to the lithium-ion battery 21. This suppresses a decrease in the charging voltage of the lithium-ion battery 21. As a result, the charging capacity of the lithium-ion battery 21 can be increased.

[0055] Furthermore, in this embodiment, the branch point 27a is located on the wiring connecting the main relay 4 and the lithium ion battery 21, closer to the main relay 4 than the lithium ion battery 21. This makes it possible to shorten the path through which a large current flows between the main relay 4 and the lithium ion battery 21 as much as possible, and to suppress a voltage drop from the branch point 27a to the lithium ion battery 21.

[0056] In this embodiment, the load 25 connected to the branch point 27a is a load required for traveling in the autonomous driving mode. By connecting the load 25 consuming a large current to the branch point 27a, the current flowing through the wiring from the branch point 27a to the lithium-ion battery 21 can be reduced, and the voltage drop from the branch point 27a to the lithium-ion battery 21 can be suppressed.

[0057] In this embodiment, the second load circuit 2 has a load 25 that consumes a large current and a load 26 that consumes a small current (corresponding to a "small-current-consuming load" of the present invention), and the load 26 is connected to a path from the branch point 27a to the lithium-ion battery 21. This separates the connection destination of the load 25 that consumes a large current from the connection destination of the load 26 that consumes a small current, so that a voltage necessary for the operation of the loads 25 and 26 can be ensured while suppressing a drop in the charging voltage of the lithium-ion battery 21.

[0058] As a modification of this embodiment, the branch wiring of the wiring box 27 and the circuit interrupting mechanism using the main relay 4 may be modularized. FIG. 4 is a schematic diagram of a relay module 40. As shown in FIG. 4, the relay module 40 is a device in which the branch wiring of the wiring box 27 and the circuit interrupting mechanism using the main relay 4 are modularized, and includes a relay 4, a branch point 27a, a diode 41, and a switch 42. The relay module 40 is connected between the first load circuit 1 and the lithium ion battery 21.

[0059] The relay 4 is connected to the upstream side within the relay module 40. The branch point 27a is provided downstream of the relay 4 within the relay module 40. Of the branch wirings from the branch point 27a, one wire 31 is connected to the load 25, and the other wire 32 is connected to the lithium-ion battery 21. The diode 41 is connected to the wire 32, with the direction in which current flows from the branch point 27a to the lithium-ion battery 21 as the forward direction. The relay module 40 also has a bypass wiring 33 that bypasses between the wire 31 and the wire 32, and a switch 42 is connected to the bypass wiring 33. The switch 42 is linked to the on / off of the relay 4; when the relay 4 is on, the switch 42 is off, and when the relay 4 is off, the switch 42 is on. When power is supplied from the first load circuit 1 to the second load circuit 2 via the relay 4, the relay 4 is on and the switch 42 is off. Furthermore, for example, if an abnormality occurs in the first load circuit 1 when the driving mode is the automatic driving mode, the relay 4 is turned off and the switch 42 is turned on, and power from the lithium ion battery 21 is supplied to the load 25. This causes the lithium ion battery 21 to function as a backup power source.

[0060] Here, a connection configuration (reference example 1) will be described in which the relay module 40 does not have the bypass wiring 33, the diode 41, and the switch 42. In the connection configuration of reference example 1, when the relay 4 is turned off and the lithium ion battery 21 is made to function as a backup power supply, the current of the lithium ion battery 21 flows to the load 25 in the order of the wiring 32, the branch point 27a, and the wiring 31. In this connection configuration, the current of the lithium ion battery 21 flows via the branch point 27a, and therefore the voltage drop is larger compared to the modified example.

[0061] Next, a connection configuration (reference example 2) will be described in which the relay module 40 does not have the diode 41 and the switch 42. In the connection configuration of reference example 2, when the relay 4 is turned on to supply power from the first load circuit 1 to the second load circuit 2, a path is formed between the relay 4 and the load 25 that bypasses the bypass wiring 33 in addition to the original path of the wiring 31. As a result, the current flowing from the relay 4 to the lithium ion battery 21 becomes small.

[0062] In the connection configuration of the modified example, when lithium ion battery 21 functions as a backup power supply, switch 42 is turned on, and current from lithium ion battery 21 flows through bypass wiring 33, but does not flow to branch point 27a. This makes it possible to suppress a drop in voltage applied to load 25 when lithium ion battery 21 functions as a backup power supply. Furthermore, in the connection configuration of the modified example, when power is supplied from first load circuit 1 to second load circuit 2, switch 42 is turned off, and current from relay 4 flows through wiring 31 and 32, but does not flow to bypass wiring 33. This makes it possible to prevent the current flowing from relay 4 to lithium ion battery 21 from decreasing.

[0063] As described above, the power supply system 100 according to the modified example includes a relay module that modularizes the branch wiring including the branch point 27a and the main relay 4. This modularizes the branch wiring and the circuit interrupting mechanism using the main relay 4, thereby increasing the versatility of the product.

[0064] Furthermore, the power supply system 100 according to the modified example has a switch 42 connected between the wiring 31 and the wiring 32. This allows the current path to be switched between when power is supplied from the first load circuit 1 to the second load circuit 2 and when the lithium ion battery 21 is functioning as a backup power supply.

[0065] As a modification of this embodiment, the DC-DC converter may be used as the circuit interrupter (corresponding to the "second circuit interrupter" of the present invention) instead of the additional relay 5. This allows both the battery interrupter and the voltage boost during charging of the lithium ion battery 21 to be achieved.

[0066] Although the embodiments of the present invention have been described above, these embodiments are described to facilitate understanding of the present invention and are not described to limit the present invention. Therefore, each element disclosed in the above embodiments is intended to include all design modifications and equivalents that fall within the technical scope of the present invention. [Explanation of symbols]

[0067] 1...1st load circuit 11...Lead battery 12...Load actuator 13...Starter motor 14...Alternator 2…Second load circuit 21...Lithium-ion battery 22...EPS actuator 23...ABS actuator 24...ADAS actuator 3...Power line 4...Main relay 5...Additional relay 6...Controller 100...Power supply system

Claims

1. A power supply system mounted on a vehicle having an autonomous driving mode, a first load circuit connected to a first load that operates using power from the main battery; a second load circuit that operates using power from the main battery or the additional battery and to which a second load necessary for continuing the automatic driving mode is connected; a first circuit interrupter provided in a power supply line electrically connecting the first load and the second load, for establishing or interrupting conduction between the first load circuit and the second load circuit; Additional relays and a controller that controls opening and closing of the first circuit interrupting mechanism and the additional relay, the first load circuit is located on one side of the first circuit interrupter; the current path on the other side of the first circuit interrupter includes a first path that causes the current flowing from the first load circuit to the first circuit interrupter to flow from a branch point located on the other side of the first circuit interrupter to the second load, and a second path that causes the current to flow from the branch point to the additional battery; the additional battery has a lower internal resistance than the main battery; a small current consuming load that consumes a small current is connected to the second path; the second load is a large current consuming load that consumes a large current, the branch point is located on a wiring connecting the first circuit interrupter and the additional battery, the branch point being closer to the first circuit interrupter than the additional battery; the additional relay is connected to the second path; a current flowing from the first load circuit to the first circuit interrupter is branched at the branch point, a large current flows through the first path to the second load, and a small current flows through the second path to the additional battery; The controller determining whether the driving mode of the vehicle is an automatic driving mode or a normal driving mode; transmitting a continuity maintaining command to the additional relay to maintain the on state regardless of whether or not an open / close control signal is input; When the driving mode of the vehicle is determined to be the autonomous driving mode, if the circuit voltage of the second load circuit falls outside a predetermined voltage range, the first circuit interrupter switches from on to off, and the additional relay to which the continuity maintenance command has been input maintains its on state.

2. 2. The power supply system according to claim 1, A power supply system including a relay module in which the branch wiring including the branch point and the first circuit interrupter mechanism are modularized.

3. 3. The power supply system according to claim 2, The relay module includes a switch connected between the first path and the second path.

4. The power supply system according to any one of claims 1 to 3, The second load is a power supply system that is a load necessary for the vehicle to travel in the autonomous driving mode.

5. The power supply system according to any one of claims 1 to 4, a second circuit interrupting mechanism for establishing or interrupting conduction between the additional battery and the second load; The second circuit interrupting mechanism is a power supply system having a DC-DC converter.

Images