Power supply system

Abstract

A power supply system (100) comprises: an electric load (34, 36); a first system (ES1) including a first power supply (10, 12, 14); a second system (ES2) including a second power supply (16); and an inter-system switch (SW1), wherein the first power supply outputs a power supply voltage and the second power supply includes a storage battery (16), the power supply system comprising: an abnormality determination unit for determining whether an abnormality has occurred in the first system; and a state control unit for disconnecting the inter-system switch when the abnormality determination unit determines that an abnormality has occurred, wherein a first path (LC1) and a second path (LC2) are provided in parallel between a connection point (PB) connected to the same connection path in the second system and the second power supply, a power converter (26) is provided in the first path, and in the second path, the battery voltage can be applied to the electric load by bypassing the power converter.

Description

[0001] Citation of related applications

[0002] This application is based on Japanese Patent Application No. 2020-083848 filed on May 12, 2020, the contents of which are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to a power supply system. Background Art

[0004] In recent years, power supply systems have become known, for example, for use in vehicles and for supplying power to various devices within the vehicle. In such power supply systems, while the vehicle is traveling, an abnormality may occur in the system supplying power to electrical loads required for vehicle operation, such as electric brakes or electric steering. Consequently, if this function is lost, the vehicle cannot continue traveling. To prevent this function from being lost even when an abnormality occurs while the vehicle is traveling, a system is known that includes a first power supply and a second power supply as power sources for supplying power to the electrical loads.

[0005] As a power supply system applied to this device, for example, in Patent Document 1, there is known a power supply system having a first system including a first power supply as a high-voltage power supply and a second system including a second power supply as a low-voltage power supply. In this power supply system, an inter-system switch is provided in the connection path connecting the systems. In addition, a DCDC converter (hereinafter referred to as the converter) is provided between the connection point of the path within the second system connected to the same connection path and the second power supply side, and the second power supply can be charged by the converter. Moreover, when the controller determines that an abnormality has occurred in the first system, the inter-system switch is closed, and power is supplied from the second power supply to the electrical load by discharging the second power supply through the converter. That is, by supplying power to the electrical load from the second power supply of the second system where no abnormality has occurred, the functions required for vehicle driving can be ensured, and the vehicle can continue driving.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Publication No. 2019-30116 Summary of the Invention

[0009] However, since the converter performs power conversion during discharge, discharge begins after preparatory processing for power conversion. Therefore, a predetermined period is required from the start of preparatory processing to the actual start of discharge, and during this predetermined period, appropriate power may not be supplied to the electrical load.

[0010] The present disclosure has been made to solve the above-mentioned technical problems, and an object of the present disclosure is to provide a power supply system that can appropriately supply power to an electric load in a power supply system having a plurality of power supply systems.

[0011] A first method for solving the above-mentioned technical problem is a power supply system, the power supply system comprising: an electric load; a first system, the first system including a first power supply connected to the electric load; a second system, the second system including a second power supply connected to the electric load; and an inter-system switch, the inter-system switch being provided in a connection path connecting the first system and the second system to each other, wherein the first power supply outputs a power supply voltage capable of driving the electric load, the second power supply includes a battery capable of being charged by the power supply voltage of the first power supply, and the power supply system comprises: an abnormality determination unit, the abnormality determination unit determining whether an abnormality has occurred in the first system and a state control unit, which disconnects the inter-system switch when the abnormality determination unit determines that an abnormality has occurred, wherein a first path and a second path are provided in parallel with each other between a connection point in the second system connected to the connection path and the second power supply, wherein a power converter is provided in the first path for performing power conversion when the battery is charged and when the battery is discharged by the power supply from the first power supply, wherein the battery is charged to a voltage higher than a lower limit value of a driving voltage of the electric load by the power converter, and wherein the voltage of the battery can be applied to the electric load in the second path while bypassing the power converter.

[0012] According to the above configuration, a first system including a first power supply and a second system including a second power supply are provided. Therefore, redundant power supply to the electrical load can be provided by the first and second power supplies. Furthermore, an intersystem switch is provided in the connection path connecting the first and second systems. Therefore, if an abnormality is determined to have occurred in either system, the intersystem switch can be opened, allowing the electrical load to continue operating using power supplied by the power supply of the other, unaffected system.

[0013] For example, if the intersystem switch is opened due to an abnormality in the first system, the power converter in the second system discharges the battery from the second power source. However, in the power converter that performs power conversion during discharge, discharge begins after the preparatory process for power conversion. Therefore, a predetermined period is required from the start of preparatory processing to the actual start of discharge, and during this predetermined period, it may be impossible to properly supply power to the electrical load.

[0014] In view of this, in the above-mentioned structure, a first path and a second path are provided in parallel between the connection point connected to the same connection path in the second system and the second power supply. In the first path, the battery is charged or discharged at a voltage higher than the lower limit of the driving voltage of the electric load through power conversion by the power converter. In addition, in the second path, the battery voltage can be applied to the electric load by bypassing the power converter. In this case, when the second system is used to supply power from the battery in response to an abnormality in the first system, the battery of the second power supply is charged to a voltage higher than the lower limit of the driving voltage of the electric load, and the voltage can be applied to the electric load by bypassing the power converter during the prescribed period required for power conversion by the power converter. As a result, appropriate power can be supplied to the electric load in a power supply system having multiple power supply systems.

[0015] In the second embodiment, a battery switch for opening or closing the second path is provided in the second path, and the power converter starts or stops charging and discharging the storage battery in accordance with a command from the state control unit. When the abnormality determination unit determines that an abnormality has occurred, the state control unit opens the inter-system switch and outputs a command to the power converter to discharge the storage battery, and closes the battery switch during a predetermined period that includes the period from output of the command to the start of discharge of the storage battery.

[0016] In the above configuration, a battery switch is provided in the second path. When an abnormality occurs in the first system, the battery switch is closed in conjunction with the output of a discharge command to the power converter. Specifically, the battery switch is closed during a predetermined period, including the period from the output of the command to the power converter to discharge the storage battery to the start of the discharge operation. This ensures that appropriate power is supplied to the electrical load when an abnormality occurs in the first system.

[0017] In a third aspect, the power converter performs a voltage boosting operation to boost the voltage of the battery when the battery is discharged, and the state control unit turns off the battery switch after the battery starts discharging.

[0018] In a configuration where the voltage of the electrical load is higher than the voltage of the battery during battery discharge, if the battery switch is closed after battery discharge begins, the battery charging via the second path may delay the rise in the voltage of the electrical load or cause the voltage of the electrical load to become unstable. To address this issue, in the above configuration, the battery switch is opened after discharge begins, allowing the voltage of the electrical load to rise appropriately.

[0019] In a fourth embodiment, the power converter performs a step-down operation to step down the voltage of the battery when the battery is charged, and performs a step-up operation to step up the voltage of the battery when the battery is discharged, and a rectifying element is provided in the second path for restricting the flow of current from the connection point to the battery in the second path.

[0020] In a configuration designed to lower the battery voltage than the power supply voltage during battery charging, a rectifier element is provided in the second path. This rectifier restricts the flow of current from the connection point to the battery in the second path, enabling the power supply system to be constructed using batteries with a rated voltage lower than the power supply voltage. Furthermore, if an abnormality occurs in the first system, the battery is discharged in the second system as the voltage on the electrical load side decreases. During battery discharge, power can be supplied to the electrical load in an accelerated manner, without waiting for the predetermined period required for the power converter to step up the voltage.

[0021] In the fifth aspect, a semiconductor switching element having a parasitic diode is provided in the second path, the parasitic diode is the rectifying element, and the state control unit turns on the semiconductor switching element when the abnormality determination unit determines that an abnormality has occurred.

[0022] In a configuration using the parasitic diode of a semiconductor switching element as a rectifying element, power can be supplied from the battery to the electrical load via the parasitic diode when an abnormality occurs in the first system. However, this causes a voltage drop due to the forward voltage drop of the parasitic diode. Furthermore, the parasitic diode may generate heat due to the energization. To address this issue, in the above configuration, when an abnormality occurs in the first system, the semiconductor switching element is in the on state. This allows voltage to be output to the electrical load earlier, and the voltage drop caused by the forward voltage drop of the parasitic diode can be suppressed. Furthermore, the generation of heat in the parasitic diode can be suppressed.

[0023] In a sixth embodiment, the power supply system is installed in a vehicle, wherein the electric load is a load for implementing at least one function required for driving in the vehicle and is a load for implementing a driving assistance function of the vehicle, the vehicle is capable of driving in a first mode using the driving assistance function and in a second mode not using the driving assistance function, and the power supply system includes a mode control unit that allows the driving mode of the vehicle to be transferred from the second mode to the first mode on the condition that the storage state of the battery is a state in which the voltage of the battery is higher than a lower limit value of the driving voltage of the electric load.

[0024] A power supply system for a vehicle equipped with an electrical load that performs functions necessary for driving and implements a driving assistance function can switch between a first driving mode in which the driving assistance function is used and a second driving mode in which the driving assistance function is not used. In the above configuration, the vehicle's driving mode is allowed to shift from the second mode to the first mode when the battery voltage exceeds the lower limit of the driving voltage of the electrical load. Therefore, even if an abnormality occurs in the first system after the transition to the first mode, appropriate fail-safe procedures can be implemented. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The above objects, other objects, features and advantages of the present disclosure will become more apparent with reference to the accompanying drawings and the following detailed description.

[0026] Figure 1 It is an overall configuration diagram of the power supply system according to the first embodiment.

[0027] Figure 2 This is a flowchart showing the procedure of the control process of the first embodiment.

[0028] Figure 3 This is a sequence diagram showing an example of the control process according to the first embodiment.

[0029] Figure 4 It is an overall configuration diagram of a power supply system according to the second embodiment.

[0030] Figure 5 This is a flowchart showing the procedure of the control process of the second embodiment.

[0031] Figure 6 This is a sequence diagram showing an example of the control process according to the second embodiment.

[0032] Figure 7 This is an overall configuration diagram of a power supply system according to another embodiment. DETAILED DESCRIPTION

[0033] (First embodiment)

[0034] Hereinafter, an embodiment in which the power supply system of the present disclosure is embodied as a power supply system 100 mounted on a vehicle will be described with reference to the drawings.

[0035] like Figure 1 As shown, power supply system 100 is a system that supplies power to general loads 30 and specific loads 32. Power supply system 100 includes a high-voltage battery 10, a first DC-DC converter (hereinafter referred to as a first converter) 12, a first battery 14, a second battery 16, a switching unit 20, a second DC-DC converter (hereinafter referred to as a second converter) 26, and a control device 40.

[0036] The high-voltage battery 10 has a higher rated voltage (e.g., several hundred volts) than the first and second batteries 14, 16, and is, for example, a lithium-ion battery. The first converter 12 is a voltage generating unit that converts the power supplied from the high-voltage battery 10 into power at a power supply voltage VA, and supplies the power to the general load 30 and the specific load 32. In this embodiment, the power supply voltage VA is a voltage sufficient to drive the general load 30 and the specific load 32.

[0037] General load 30 is an electric load (hereinafter simply referred to as a load) not used for driving control in a vehicle as a moving object, and includes, for example, an air conditioner, an audio device, and power windows.

[0038] On the other hand, the specific load 32 is a load that implements at least one function for controlling the vehicle's travel, such as an electric power steering device 50 that controls the vehicle's steering, an electric brake device 51 that applies braking force to the wheels, a travel control device 52 that monitors the vehicle's surrounding conditions, etc. In this embodiment, the specific load 32 corresponds to an "electric load."

[0039] Therefore, if these specific loads 32 experience an abnormality and all their functions are lost, driving control becomes impossible. Therefore, to prevent all functions from being lost even in the event of an abnormality, the specific loads 32 include a first load 34 and a second load 36, redundantly provided for each function. Specifically, the electric power steering system 50 includes a first steering motor 50A and a second steering motor 50B. The electric brake system 51 includes a first brake system 51A and a second brake system 51B. The driving control system 52 includes a camera 52A and a laser radar 52B. The first steering motor 50A, the first brake system 51A, and the camera 52A correspond to the first load 34, while the second steering motor 50B, the second brake system 51B, and the laser radar 52B correspond to the second load 36.

[0040] The first load 34 and the second load 36 together perform a single function, but each can also perform a portion of that function when used independently. For example, in the electric power steering system 50, the first steering motor 50A and the second steering motor 50B can be used to steer the vehicle freely. However, when there are certain restrictions on steering speed, steering range, etc., the steering motors 50A and 50B can be used to steer the vehicle independently.

[0041] During manual driving, each specific load 32 performs a function to assist the driver's control. Furthermore, during automated driving, which automatically controls the vehicle's movement, such as when it moves or stops, each specific load 32 performs a function required for automated driving. Therefore, a specific load 32 can also be referred to as a load that implements at least one function required for vehicle driving.

[0042] A first load 34 is connected to the first converter 12 via a first intra-system path LA1. The first battery 14 and a general load 30 are also connected to this first intra-system path LA1. The first battery 14 is, for example, a lead-acid battery. In this embodiment, the first converter 12, the first battery 14, the general load 30, and the first load 34, connected via the first intra-system path LA1, constitute a first system ES1. In this embodiment, the high-voltage battery 10, the first converter 12, and the first battery 14 constitute a "first power source."

[0043] Furthermore, a second load 36 is connected to a second battery 16 via a second intra-system path LA2. Second battery 16 is, for example, a lithium-ion battery. The rated voltage of second battery 16 is set to a voltage lower than the power supply voltage VA of first converter 12. In the present embodiment, second battery 16 and second load 36 connected via second intra-system path LA2 constitute a second system ES2. In the present embodiment, second battery 16 corresponds to a "second power source / battery."

[0044] The switch unit 20 is provided in the connection path LB that connects the systems. One end of the connection path LB is connected to the first intra-system path LA1 at a connection point PA, and the other end of the connection path LB is connected to the second intra-system path LA2 at a connection point PB. The switch unit 20 includes a first switching element (hereinafter referred to as the first switch) SW1. In this embodiment, an N-channel MOSFET (hereinafter referred to as the MOSFET) is used as the first switch SW1. In this embodiment, the first switch SW1 functions as an "inter-system switch."

[0045] The connection path LB is provided with a current detection unit 28. The current detection unit 28 is provided in a portion of the connection path LB closer to the first system ES1 than the switch unit 20, and detects the magnitude and direction of the inter-system current IA flowing therethrough.

[0046] The second converter 26 is provided in the second intra-system path LA2. Specifically, the second converter 26 is provided in the second intra-system path LA2 between the connection point PB connected to the connection path LB and the second battery 16. The second converter 26 receives the power supplied from the first converter 12, steps it down to a voltage lower than the power supply voltage VA, and charges the second battery 16. Furthermore, when the second battery 16 is discharging, the second converter 26 steps up the voltage of the second battery 16 and applies it to the second load 36. In other words, the second converter 26 is capable of both stepping up and stepping down the voltage, and is a bidirectional power converter that converts power when the second battery 16 is charging and discharging. Furthermore, the second battery 16 can be charged using the power supply voltage VA from the first converter 12.

[0047] Based on the detection value of the current detection unit 28, the control device 40 generates a first switching signal SC1 to switch the first switch SW1 and outputs a command based on the first switching signal SC1 to the first switch SW1. Furthermore, the control device 40 generates a first control signal SD1 and a second control signal SD2 to control the operation of the first converter 12 and the second converter 26 and outputs commands based on the first control signal SD1 and the second control signal SD2 to the first converter 12 and the second converter 26. The first control signal SD1 and the second control signal SD2 switch the first converter 12 and the second converter 26 between an operating state and an operating stop state. The operating state of the second converter 26 includes a charging state for charging the second battery 16 and a discharging state for discharging the second battery 16.

[0048] The control device 40 is also connected to a notification unit 44, an in-vehicle start switch 45, and an input unit 46, and controls these. The notification unit 44 is a device that notifies the driver visually or audibly, and may be, for example, a display or speaker installed in the vehicle cabin. The in-vehicle start switch 45 is the vehicle start switch. The control device 40 monitors whether the in-vehicle start switch 45 is open or closed. The input unit 46 is a device that receives driver operations, and may be, for example, a steering wheel, lever, buttons, pedals, or a voice input device.

[0049] The control device 40 uses the specific load 32 to control manual and automatic driving of the vehicle. The control device 40 includes a well-known microcomputer composed of a CPU, ROM, RAM, flash memory, etc. The CPU references the calculation program and control data in the ROM to implement various functions for manual and automatic driving.

[0050] Manual driving refers to a state where the vehicle's travel is controlled by the driver's operation. Automatic driving refers to a state where the vehicle's travel is controlled by the control details of the control device 40 without the driver's operation. Specifically, automatic driving refers to automatic driving at or above Level 3, on the scale of Level 0 to Level 5 defined by the U.S. Department of Transportation's National Highway Traffic Safety Administration (NHTSA). Level 3 is a level where the control device 40 controls both steering wheel operation and acceleration and deceleration while monitoring the driving environment.

[0051] In addition, the control device 40 can use the above-mentioned specific load 32 to implement driving assistance functions such as LKA (Lane Keeping Assist: lane departure warning), LCA (Lane Change Assist: lane change reminder), PCS (Pre-Crash Safety: pre-collision protection). The control device 40 can switch the driving mode of the vehicle to a first mode that uses the driving assistance function and a second mode that does not use the driving assistance function, and the vehicle can achieve driving based on each driving mode. The control device 40 switches the first mode and the second mode according to the driver's switching instruction input through the input unit 46. Here, the first mode includes a mode in which the driver manually drives the vehicle using the driving assistance function and a mode in which the vehicle automatically drives. The second mode is a mode in which the driver manually drives the vehicle without using the driving assistance function.

[0052] In the first mode, the control device 40 determines whether an abnormality has occurred in the first system ES1 and the second system ES2. If it is determined that no abnormality has occurred in either system ES1 or ES2, the first load 34 and the second load 36 are used to automatically control and assist the vehicle. Thus, the first load 34 and the second load 36 cooperate to implement a function required for automatic control and driving assistance. In this embodiment, the abnormality is a power supply failure such as a ground fault or a disconnection.

[0053] On the other hand, if it is determined that an abnormality has occurred in either system ES1 or ES2, the first switch SW1 is opened to electrically isolate the first system ES1 from the second system ES2. Thus, even if an abnormality has occurred in either system ES1 or ES2, the loads 34 and 36 of the other system ES1 or ES2, which is not abnormal, can be driven.

[0054] When the first switch SW1 opens due to an abnormality in the first system ES1, power is supplied to the second load 36 in the second system ES2 by discharging the second storage battery 16 via the second converter 26. Since the second converter 26 performs power conversion during discharge, discharge begins after a preparatory process for power conversion. Here, preparatory processing refers to, for example, the process of flowing a specified current through the primary coil of a converter comprising an input primary coil and an output secondary coil. Therefore, a specified period TS is required from the start of preparatory processing to the actual start of discharge. During this period TS, there is a possibility that the second system ES2 may not be properly supplied with power.

[0055] In this embodiment, a first path LC1 and a second path LC2 are provided in parallel between a connection point PB connected to the connection path LB in the second system ES2 and the second storage battery 16. The second converter 26 is provided in the first path LC1. Through power conversion by the second converter 26, the second storage battery 16 is charged or discharged at a voltage higher than the threshold voltage Vth, which is the lower limit value of the drive voltage of the first and second loads 34 and 36.

[0056] Furthermore, in the second path LC2, the voltage of the second battery 16 can be applied to the first load 34 and the second load 36, bypassing the second converter 26. Specifically, a switch unit 24 is provided in the second path LC2. Hereinafter, for distinction, the switch unit 20 will be referred to as the first switch unit 20, and the switch unit 24 will be referred to as the second switch unit 24. The second switch unit 24 includes a second switching element (hereinafter referred to as the second switch) SW2 and a diode DA connected in series. In the second switch unit 24, the second switch SW2 is located closer to the connection path LB than the diode DA.

[0057] The second switch SW2 opens or closes the second system ES2. In this embodiment, a MOSFET is used as the second switch SW2. The control device 40 generates a second switching signal SC2 and outputs a command based on the second switching signal SC2 to the second switch SW2 to switch the second switch SW2. Furthermore, the diode DA is arranged with its cathode located on the connection point with the connection path LB and its anode located on the second battery 16 side. In this embodiment, the second switch SW2 functions as a "battery switch."

[0058] In this case, when power is supplied from the second storage battery 16 by the second system ES2 in response to an abnormality occurring in the first system ES1, the second storage battery 16 is charged to a voltage higher than the threshold voltage Vth, which is the lower limit of the drive voltage for the first load 34 and the second load 36. In this embodiment, during the predetermined period TS required for power conversion by the second converter 26 as the second storage battery 16 is discharged, a control process is performed to bypass the second converter 26 and apply the threshold voltage Vth to the second load 36. This allows for appropriate power supply to the loads 34 and 36 in the power supply system 100 having multiple power supply systems.

[0059] Figure 2 The flowchart of the restriction process of this embodiment is shown. When IG switch 45 is closed, control device 40 repeatedly performs the restriction process for each predetermined control cycle. Furthermore, at the beginning of IG switch 45 closing, the vehicle driving mode is set to the second mode. Furthermore, first switch SW1 is closed, second switch SW2 is open, first converter 12 is in operation, and second converter 26 is in charging operation.

[0060] When the restriction process begins, a determination is first made in step S10 as to whether the vehicle's driving mode is the second mode. If the determination in step S10 is affirmative, the remaining capacity SA of the second battery 16 is calculated in step S12. The remaining capacity SA is, for example, the SOC (State of Charge) indicating the state of charge of the second battery 16. When the second battery 16 is energized (charged or discharged), the remaining capacity SA is calculated using the current accumulation value, which is the time integral of the charge and discharge current of the second battery 16.

[0061] In step S14, a determination is made as to whether the remaining capacity SA calculated in step S12 is greater than a predetermined capacity threshold Sth. Here, capacity threshold Sth is the capacity at which the voltage of second storage battery 16 becomes higher than threshold voltage Vth. If the remaining capacity SA of second storage battery 16 is less than capacity threshold Sth, the prerequisite for executing the first mode is not met because the voltage of second storage battery 16 is not higher than threshold voltage Vth. Therefore, a negative determination is made in step S14, and the process proceeds to steps S50 and S52.

[0062] On the other hand, if the remaining capacity SA of the second battery 16 is greater than the capacity threshold Sth, the voltage of the second battery 16 is higher than the power supply voltage VA by a specified value or more, and the prerequisite for implementing the first mode is met, so a positive determination is made in step S14. In this case, in step S16, the second converter 26 is controlled to switch between the charging operation state and the operation stop state as appropriate based on the remaining capacity SA of the second battery 16. Next, in step S17, the second switch SW2 is closed. Next, in step S18, the vehicle's driving mode is allowed to switch from the second mode to the first mode, and the restriction process ends. The switch to the first mode is implemented when the driver inputs a switching instruction, such as an instruction to use a driving assistance function or an instruction to enable automatic driving, via the input unit 46. In this embodiment, the process of step S18 corresponds to the "mode control unit."

[0063] On the other hand, if a negative determination is made in step S10, a determination is made in step S20 as to whether the driver notification is in progress. Here, the driver notification notifies the driver of an abnormality occurring in either the first system ES1 or the second system ES2, notifies the driver of information to terminate the first mode, and prompts the driver to switch to the second mode.

[0064] If a negative determination is made in step S20, then steps S22 and S24 determine that an abnormality has occurred in either the first system ES1 or the second system ES2. Specifically, step S22 determines whether an abnormality has occurred in the first system ES1. If a negative determination is made in step S22, then step S24 determines whether an abnormality has occurred in the second system ES2. In this embodiment, the process of step S22 corresponds to the "abnormality determination unit."

[0065] Furthermore, the occurrence of an abnormality can be determined based on the magnitude and direction of the intersystem current IA detected by the current detection unit 28. For example, if a ground fault occurs in the first system ES1, the direction of the intersystem current IA detected by the current detection unit 28 is from the second system ES2 toward the first system ES1, and the magnitude of the intersystem current IA detected by the current detection unit 28 is greater than the specified current threshold Ith for ground fault determination. Therefore, the current flowing in the first system ES1 is greater than the current threshold Ith. Alternatively, if a ground fault occurs in the second system ES2, the direction of the intersystem current IA detected by the current detection unit 28 is from the first system ES1 toward the second system ES2, and the magnitude of the intersystem current IA detected by the current detection unit 28 is greater than the current threshold Ith. Therefore, the current flowing in the second system ES2 is greater than the current threshold Ith. Therefore, based on the magnitude and direction of the intersystem current IA detected by the current detection unit 28, it is possible to determine in which system ES1 or ES2 the abnormality has occurred.

[0066] If it is determined that no abnormality has occurred in either system ES1 or ES2, a negative determination is made in step S24. In this case, the restriction process is terminated.

[0067] On the other hand, when it is determined that an abnormality has occurred in either of the systems ES1 and ES2, a process is performed to stop the power supply to the system where the abnormality has occurred and to continue the power supply to the electrical loads of the system where the abnormality has not occurred.

[0068] Specifically, if a positive determination is made in step S22, then in step S26, a determination is first made as to whether the first switch SW1 is open. If a negative determination is made in step S26, the first switch SW1 is opened in step S28. Next, in step S30, a command is output to stop the operation of the first converter 12. This halts the power supply to the first system ES1 where the abnormality has occurred. In this embodiment, the processing in step S28 corresponds to the "state control unit."

[0069] Next, in step S32, a command is output to place second converter 26 in a discharge operation state to boost the voltage of second battery 16. Next, in step S34, after the command is output in step S32, second switch SW2 is closed, and the control process ends. The discharge of second battery 16 by second converter 26 ensures the power supply to second load 36.

[0070] On the other hand, if the determination in step S26 is affirmative, that is, if the processes of steps S28 to S34 have already been performed, a determination is made in step S36 as to whether the load voltage VD applied to the second load 36 is equal to or greater than the predetermined target voltage Vtg. The load voltage VD is increased to the target voltage Vtg by the discharge of the second battery 16 by the second converter 26.

[0071] If the load voltage VD is lower than the target voltage Vtg, a negative determination is made in step S36. In this case, the control process ends, and the boosting of the load voltage VD by the second converter 26 continues. On the other hand, if the load voltage VD is equal to or higher than the target voltage Vtg, an affirmative determination is made in step S36. In this case, the second switch SW2 is turned off in step S38.

[0072] If a positive determination is made in step S24, first, in step S40, the first switch SW1 is opened. As a result, power continues to be supplied from the first converter 12 in the first system ES1 to the first load 34. Next, in step S42, a command is output to stop the operation of the second converter 26.

[0073] Thereafter, in step S44 , the driver is notified of the suspension of the first mode via the notification unit 44 , and the control process is terminated.

[0074] If a positive determination is made in step S20, a determination is made in step S46 as to whether a driver has input an instruction to switch to the second mode via input unit 46. In other words, a determination is made as to whether the driver has responded to the notification. If a negative determination is made in step S46, the control process is terminated, and the vehicle continues traveling in the first mode using loads 34 and 36 on the system side where no abnormality has occurred.

[0075] On the other hand, if an affirmative determination is made in step S46 , the driving mode of the vehicle is switched from the first mode to the second mode in step S48 , and the control process is terminated.

[0076] In steps S50 and S52, that is, if the vehicle's driving mode is the second mode, it is determined that an abnormality has occurred in either the first system ES1 or the second system ES2. Specifically, in step S50, a determination is made as to whether an abnormality has occurred in the first system ES1. If a negative determination is made in step S50, a determination is made as to whether an abnormality has occurred in the second system ES2 in step S52.

[0077] If it is determined that no abnormality has occurred in any of the systems ES1 and ES2, a negative determination is made in step S52. In this case, the control process is terminated and the vehicle continues traveling in the second mode.

[0078] On the other hand, when it is determined that an abnormality has occurred in either of the systems ES1 and ES2, a process is performed to stop the power supply to the system where the abnormality has occurred and to continue the power supply to the electrical loads of the system where the abnormality has not occurred.

[0079] Specifically, if a positive determination is made in step S50, first, in step S54, the first switch SW1 is opened. Next, in step S56, a command is output to stop the operation of the first converter 12. Next, in step S34, the second switch SW2 is closed, and the process proceeds to step S66. In other words, in the second mode, when an abnormality occurs in the first system ES1, the second converter 26 is not switched on or off.

[0080] If a positive determination is made in step S52, the processing of steps S62 to S64 is executed. The processing of steps S62 to S64 is the same as the processing of steps S40 to S44, and therefore description thereof is omitted.

[0081] then, Figure 3 An example of control processing is shown. Figure 3 The figure shows changes in the power supply voltage VA and the load voltage VD when a ground fault abnormality (hereinafter simply referred to as a ground fault) occurs in the first system ES1 while the vehicle is traveling in the first mode.

[0082] exist Figure 3 In FIG. 1 , (A) indicates the change in the state of the IG switch 45, (B) indicates the change in the driving mode of the vehicle, (C) indicates the change in the open / close state of the first switch SW1, and (D) indicates the change in the open / close state of the second switch SW2. In addition, (E) indicates the change in the operating state of the second converter 26, (F) indicates the change in the power supply voltage VA in the first converter 12, and (G) indicates the change in the load voltage VD in the second load 36. In addition, (H) indicates the change in the inter-system current IA, and (I) indicates the change in the remaining capacity SA of the second battery 16. In addition, in Figure 3 In (H), the transition of the inter-system current IA is shown by assuming that the inter-system current IA flowing from the second system ES2 to the first system ES1 is in the positive direction.

[0083] like Figure 3As shown, during the IG switch 45 off period until time t1, i.e., during the idle state of the power supply system 100, the first switch SW1 and the second switch SW2 are turned off, and the first converter 12 and the second converter 26 are switched to a stopped state. Therefore, during the IG switch 45 off period, the load voltage VD and the inter-system current IA are zero.

[0084] When IG switch 45 is closed at time t1, first switch SW1 is closed and outputs a command to switch first converter 12 to the operating state and second converter 26 to the charging operating state. As a result, first converter 12 is switched to the operating state, and power supply voltage VA and load voltage VD rise to a predetermined operating voltage VM, enabling vehicle travel in the second mode. Operating voltage VM is within the drive voltage range of first load 34 and second load 36 and is equal to target voltage Vtg.

[0085] In addition, the second converter 26 is switched to the charging operation state, and the second battery 16 is charged by the power supply voltage VA of the first converter 12. As a result, the voltage of the second battery 16 rises to a predetermined step-down voltage VL (see Figure 3 (G)).

[0086] Furthermore, when the remaining capacity SA of second battery 16 increases and becomes greater than capacity threshold Sth, the vehicle's driving mode can be switched from the second mode to the first mode at time t2. Subsequently, in response to a driver's instruction to switch to the first mode, the vehicle switches to the first mode and closes second switch SW2. Furthermore, in this embodiment, even after switching to the first mode, second converter 26 remains in operation and continues charging second battery 16. In the first mode, as remaining capacity SA increases, the charging current of second battery 16 decreases, reducing the magnitude of inter-system current IA. Furthermore, when remaining capacity SA reaches full charge, charging of second battery 16 is temporarily suspended.

[0087] While the vehicle is traveling in the first mode, a ground fault is determined to have occurred in either the first system ES1 or the second system ES2. If a ground fault is determined not to have occurred in either system ES1 or ES2, the first switch SW1 remains closed. This allows power to be supplied to the first load 34 and the second load 36 from the first converter 12 and the first and second batteries 14 and 16, respectively. Power supply from the first converter 12 allows for continuous power supply even during extended periods of autonomous driving, while power supply from the first and second batteries 14 and 16 allows for power supply with minimal voltage fluctuations. As a result, autonomous driving and driving assistance using the first and second loads 34 and 36 are performed from time t2 to time t3.

[0088] When it is determined that a ground fault has occurred in either of the systems ES1 and ES2, the first switch SW1 is closed. Figure 3 In the example, at time t3, a ground fault occurs in the first system ES1. As a result, the power supply voltage VA and the load voltage VD decrease. Furthermore, due to the inductance component of the connection path LB, the load voltage VD decreases more slowly than the power supply voltage VA.

[0089] Furthermore, the intersystem current IA increases, and at time t4, it exceeds the current threshold Ith. This indicates that a ground fault has occurred in the first system ES1. In this case, at time t4, the first switch SW1 is opened, and the first converter 12 is switched to a stopped state. This causes the intersystem current IA to decrease.

[0090] At time t4, a command is output to switch the second converter 26 to a discharge mode, which boosts the voltage of the second battery 26. Consequently, at time t6, battery discharge via the second converter 26 begins, increasing the load voltage VD. Furthermore, the second switch SW2 is closed for at least a portion of the predetermined period TS from time t4 to time t6. Consequently, during this predetermined period TS, a stepped-down voltage VL, representing the voltage of the second battery 16, is applied to the second load 36, bypassing the second converter 26.

[0091] like Figure 3As shown by the dashed line in (G), if the stepped-down voltage VL is not applied during the predetermined period TS, the load voltage VD falls below the threshold voltage Vth at time t5, between time t4 and time t6. Then, at time t7, after the battery begins discharging, the load voltage VD rises above the threshold voltage Vth. Specifically, during the voltage step-down period TD from time t5 to time t7, the load voltage VD falls below the threshold voltage Vth, temporarily shutting off the power supply to the second load 36.

[0092] In this embodiment, the stepped-down voltage VL is applied to the second load 36 during the predetermined period TS. Since the stepped-down voltage VL is set higher than the threshold voltage Vth, the load voltage VD can be prevented from falling below the threshold voltage Vth when an abnormality occurs in the first system ES1.

[0093] In particular, in the present embodiment, the second switch SW2 is maintained in the closed state in the first mode. Therefore, as the load voltage VD decreases, the second battery 16 is discharged via the second path LC2, and power can be supplied to the second load 36 at an early stage.

[0094] At time t8 after a predetermined period TS has elapsed, that is, after discharge of the second battery 16 has started, when the load voltage VD rises to the target voltage Vtg, the second switch SW2 is turned off. This prevents the second battery 16 from being charged by the load voltage VD.

[0095] Thereafter, when the driver inputs an instruction to switch to the second mode via the input unit 46 , the driving mode of the vehicle is switched from the first mode to the second mode at time t9 .

[0096] According to the present embodiment described in detail above, the following effects can be obtained.

[0097] In this embodiment, a first path LC1 and a second path LC2 are provided in parallel between a connection point PB connected to the connection path LB in the second system ES2 and the second storage battery 16. In the first path LC1, power conversion by the second converter 26 allows the second storage battery 16 to be charged or discharged at a voltage higher than the threshold voltage Vth, which is the lower limit of the drive voltage for the first and second loads 34, 36. Furthermore, in the second path LC2, the voltage of the second battery 16 can be applied to the first and second loads 34, 36, bypassing the second converter 26.

[0098] In this case, when power is supplied from second storage battery 16 by second system ES2 following an abnormality in first system ES1, second storage battery 16 is charged to a voltage higher than threshold voltage Vth, the lower limit of the drive voltage for first load 34 and second load 36. During a predetermined period TS required for power conversion by second converter 26, second converter 26 can be bypassed and threshold voltage Vth can be applied to second load 36. This allows appropriate power supply to loads 34 and 36 in power supply system 100 having multiple power supply systems.

[0099] In this embodiment, a second switch SW2 is provided in the second path LC2. When an abnormality occurs in the first system ES1, the second switch SW2 is closed in conjunction with the output of a discharge command to the second converter 26. Specifically, the second switch SW2 is closed during a predetermined period TS between the output of the command to the second converter 26 to discharge the second storage battery 16 and the start of the discharge operation. This allows for appropriate power supply to the second load 36 even when an abnormality occurs in the first system ES1.

[0100] In a configuration where the load voltage VD is higher than the voltage of the second battery 16 during discharge of the second battery 16, if the second switch SW2 is closed after the discharge of the second battery 16 begins, the charging of the second battery 16 via the second path LC2 may delay the rise of the load voltage VD or cause the load voltage VD to become unstable. To address this issue, in this embodiment, the second switch SW2 is opened after the discharge operation begins, thereby allowing the load voltage VD to rise appropriately.

[0101] The first and second loads 34 and 36 implement functions necessary for vehicle driving and also implement driving assistance functions. Furthermore, the vehicle can switch between a first driving mode in which the driving assistance functions are used and a second driving mode in which the driving assistance functions are not used. In this embodiment, the vehicle's driving mode can be switched from the second mode to the first mode, provided that the remaining capacity SA of the second battery 16 is such that the voltage of the second battery 16 exceeds the lower limit of the driving voltage of the first and second loads 34 and 36. Therefore, even if an abnormality occurs in the first system ES1 after the vehicle switches to the first mode, appropriate fail-safe processing can be implemented.

[0102] (Second embodiment)

[0103] Below, refer to Figure 4 、 Figure 5 , the second embodiment will be described focusing on the differences from the first embodiment.

[0104] In this embodiment, if Figure 4 As shown, the second switch section 24 is different from the first embodiment in that it includes a third switch SW3 and a fourth switch SW4 connected in series. In the second switch section 24, the third switch SW3 is provided closer to the connection path LB than the fourth switch SW4.

[0105] In this embodiment, MOSFETs, which are semiconductor switching elements, are used as the third switch SW3 and the fourth switch SW4. A third parasitic diode DA3 is connected in parallel with the third switch SW3, and a fourth parasitic diode DA4 is connected in parallel with the fourth switch SW4. In this embodiment, the third switch SW3 and the fourth switch SW4 are connected in series so that the directions of the third parasitic diode DA3 and the fourth parasitic diode DA4 are opposite to each other.

[0106] Specifically, the third parasitic diode DA3 is configured with its anode on the second battery 16 side and its cathode on the connection path LB side. The fourth parasitic diode DA4 is configured with its anode on the connection path LB side and its cathode on the second battery 16 side. Therefore, the third parasitic diode DA3 restricts the flow of current from the connection point PB to the second battery 16 along the second path LC2, while the fourth parasitic diode DA4 restricts the flow of current from the second battery 16 to the connection point PB along the second path LC2. In this embodiment, the third parasitic diode DA3 functions as a "rectifier element."

[0107] The control device 40 generates third and fourth switching signals SC3 and SC4 in the control process, and outputs instructions based on the third and fourth switching signals SC3 to the third and fourth switches SW3 and SW4 to perform switching operations on the third and fourth switches SW3 and SW4.

[0108] Figure 5 FIG. 4 is a flowchart showing the control process of this embodiment. Figure 5 For convenience, Figure 2 The same processes as those shown are denoted by the same step numbers and their descriptions are omitted. In addition, at the beginning of closing of the IG switch 45, the third switch SW3 is opened and the fourth switch SW4 is closed.

[0109] In the control process of this embodiment, if the determination in step S22 is affirmative, then in step S70, it is determined whether second converter 26 is in the discharging operation state. If the determination in step S70 is negative, the processes of steps S28 to S32 are executed, and the control process ends. On the other hand, if the determination in step S70 is affirmative, that is, if the processes of steps S28 to S32 have already been executed, then in step S72, it is determined whether load voltage VD is higher than stepped-down voltage VL of second battery 16.

[0110] If the discharge operation of the second converter 26 has not yet started and the load voltage VD is lower than the step-down voltage VL, a negative determination is made in step S72. In this case, the control process ends, and the discharge of the second battery 16 continues in the second path LC2 via the fourth switch SW4 and the third parasitic diode DA3. On the other hand, if the discharge operation of the second converter 26 has started and the load voltage VD is higher than the step-down voltage VL, a positive determination is made in step S72. In this case, a determination is made in step S74 whether the load voltage VD has reached or exceeded the target voltage Vtg.

[0111] If the load voltage VD is lower than the target voltage Vtg, a negative determination is made in step S74. In this case, the third switch SW3 is closed, i.e., turned on, in step S76, and the control process ends. Consequently, the second battery 16 is discharged in the second path LC2 via the fourth switch SW4 and the third switch SW3. On the other hand, if the load voltage VD is higher than the target voltage Vtg, a positive determination is made in step S74. In this case, the third switch SW3 and the fourth switch SW4 are opened in step S78, and the process proceeds to step S44.

[0112] If an affirmative determination is made in step S24 , the first switch SW1 and the fourth switch SW4 are turned off in step S80 , and the process proceeds to step S64 .

[0113] On the other hand, if the determination in step S50 is positive, after executing steps S54 and S56, the fourth switch SW4 is turned off in step S82, and the process proceeds to step S60. Furthermore, if the determination in step S52 is positive, the first switch SW1 and the fourth switch SW4 are turned off in step S84, and the process proceeds to step S64.

[0114] Figure 6 FIG. 2 shows the transition of the power supply voltage VA and the load voltage VD when a ground fault occurs in the first system ES1 while the vehicle is traveling in the first mode. Figure 6In FIG. 1 , (D) shows the transition of the open / close state of the third switch SW3, and (E) shows the transition of the open / close state of the fourth switch SW4. Figure 6 (A)~(C), (F)~(J) and Figure 3 (A) to (C) and (E) to (I) are the same, so the description is omitted.

[0115] like Figure 3 As shown, during the period until time t1 when IG switch 45 is off, third switch SW3 and fourth switch SW4 are open. At time t1, when IG switch 45 is closed, fourth switch SW4 is closed. Even if the vehicle's driving mode is switched to the first mode at time t2 and a ground fault is determined to have occurred in first system ES1 at time t4, the open and closed states of third switch SW3 and fourth switch SW4 are maintained. Furthermore, at time t4, fourth switch SW4 is closed, enabling discharge from second battery 16 via third parasitic diode DA3. Consequently, discharge from second battery 16 proceeds as load voltage VD decreases.

[0116] Then, at time t6 , the discharge of the battery via the second converter 26 is started, and when the load voltage VD is higher than the stepped-down voltage VL of the second battery 16 , the third switch SW3 is closed.

[0117] At a subsequent time t8 , when the load voltage VD rises to the target voltage Vtg, the third switch SW3 and the fourth switch SW4 are turned off.

[0118] According to the present embodiment described in detail above, the following effects can be obtained.

[0119] In this embodiment, a third switch SW3 having a third parasitic diode DA3 is provided in the second path LC2. When the second battery 16 is discharged, and the load voltage VD is higher than the voltage of the second battery 16, the third parasitic diode DA3 restricts the flow of current from the connection point PB to the second battery 16 in the second path LC2. This allows the power supply system 100 to be configured using a second battery 16 with a rated voltage lower than the power supply voltage VA. Furthermore, if an abnormality occurs in the first system ES1, the second system ES2 discharges the second battery 16 as the load voltage VD decreases. This allows power to be supplied to the second load 36 in an earlier stage, without waiting for the predetermined period TS required for the voltage boosting operation of the second converter 26.

[0120] When the third parasitic diode DA3 of the third switch SW3 is used as a rectifying element, there is a possibility of voltage drop due to the forward voltage drop of the third parasitic diode DA3 or heat generation in the third parasitic diode DA3 due to current flow. To address this issue, in this embodiment, when an abnormality occurs in the first system ES1, closing the third switch SW3 can suppress the voltage drop due to the forward voltage drop of the third parasitic diode DA3 and can also suppress the heat generation in the third parasitic diode DA3.

[0121] In this embodiment, a fourth switch SW4 is provided in series with the third switch SW3 in the second path LC2. The direction of the third parasitic diode DA3 of the third switch SW3 in the second path LC2 is opposite to the direction of the fourth parasitic diode DA4 of the fourth switch SW4. Thus, in a configuration using the third parasitic diode DA3 as a rectifying element, overdischarge of the second storage battery 16 can be suppressed when an abnormality occurs in the second system ES2.

[0122] (Other embodiments)

[0123] The present disclosure is not limited to the description of the above-mentioned embodiment, and can also be implemented in the following forms.

[0124] Each load 34 or 36 may be, for example, the following device.

[0125] Alternatively, the first load 34 and the second load 36 may be a three-phase permanent magnet synchronous motor and a three-phase inverter device, respectively.

[0126] It can also be an anti-lock brake device that prevents the wheels from locking during braking. In this case, the first load 34 and the second load 36 are, for example, ABS actuators that can independently adjust the brake oil pressure during braking.

[0127] Alternatively, a cruise control system may be provided that detects a preceding vehicle traveling ahead of the host vehicle, maintains a constant distance between the preceding vehicle and the preceding vehicle when the preceding vehicle is detected, and controls the host vehicle to travel at a preset speed when the preceding vehicle is not detected. In this case, the first load 34 and the second load 36 are each, for example, a millimeter-wave radar.

[0128] The loads 34 and 36 do not necessarily need to be identical in configuration; they may be different types of devices that perform the same function. Furthermore, the first load 34 and the second load 36 may be the same load rather than separate loads. In other words, the first load 34 and the second load 36 may be the same load that receives power from both the first intra-system path LA1 and the second intra-system path LA2.

[0129] The voltage generating unit of the first power supply is not limited to a converter, and may be an AC generator. In addition, the first power supply may not have a voltage generating unit, but may have only the first battery 14, for example.

[0130] In the above embodiment, the predetermined period TS is exemplified as the period from time t4 to time t6, that is, the period from the output of the command to the second converter 26 to discharge the second storage battery 16 to the start of discharge of the second storage battery 16. However, the present invention is not limited thereto. The period from time t4 to time t6 can be predetermined based on, for example, the internal resistance of the second storage battery 16 or the wiring resistance of the first path LC1. However, it is expected that this period will vary depending on, for example, the temperature environment of the power supply system 100. Therefore, to account for this variation, the predetermined period TS may be set to include the period from time t4 to time t6, that is, to a period longer than the period from time t4 to time t6.

[0131] In the second embodiment described above, an example is shown in which the rectifying element provided in the second path LC2 is the third parasitic diode DA3 of the third switch SW3 , but the present invention is not limited thereto.

[0132] For example, Figure 7 As shown in FIG, the rectifier element can also be a single diode element. Figure 7 As shown in FIG, in this embodiment, the second switch unit 24 includes only a diode DA as a single diode element. Note that this diode DA is equivalent to the diode DA of the first embodiment, and therefore its description is omitted.

[0133] In addition, the rectifying element is not limited to a diode, and may be a thyristor.

[0134] In the above embodiment, the power supply system 100 is applied to a vehicle capable of both manual and automatic driving. However, the present invention is not limited thereto. The power supply system 100 can be applied to vehicles capable of driving only by automatic driving, such as fully autonomous vehicles, or vehicles capable of driving only by manual driving.

[0135] For example, in the case of a vehicle that can only be driven by automatic driving, when an abnormality occurs in either system ES1 or ES2, the following processing can be implemented: the loads 34 and 36 of the other system ES1 or ES2 in which no abnormality occurs can be used to stop the vehicle's driving by automatic driving, or to stop the vehicle after moving to a safe place.

[0136] Although the present disclosure is described based on embodiments, it should be understood that the present disclosure is not limited to the above-described embodiments and structures. The present disclosure also includes various modifications and variations within the scope of equivalents. In addition, various combinations and methods, including other combinations and methods including only one element, more than one element, or less than one element, also fall within the scope and scope of the present disclosure.

Claims

1. A power supply system, comprising: electrical loads; a first system comprising a first power source connected to the electrical load; a second system comprising a second power source connected to the electrical load; as well as an inter-system switch provided in a connection path connecting the first system and the second system to each other, The first power supply outputs a power supply voltage capable of driving the electric load, The second power supply includes a battery that can be charged by the power supply voltage of the first power supply, The power supply system comprises: an abnormality determination unit configured to determine whether an abnormality has occurred in the first system; as well as a state control unit that turns off the inter-system switch when the abnormality determination unit determines that an abnormality has occurred, A first path and a second path are provided in parallel with each other between a connection point connected to the connection path in the second system and the second power supply. A power converter is provided in the first path, and performs power conversion when the battery is charged and when the battery is discharged by the power supply from the first power source. The battery is charged by the power converter to a voltage higher than a lower limit value of a drive voltage of the electric load. In the second path, the voltage of the battery can be applied to the electric load while bypassing the power converter.

2. The power supply system according to claim 1, wherein: A battery switch for opening or closing the second path is provided in the second path. The power converter starts or stops charging or discharging the battery according to the instruction from the state control unit. When the abnormality determination unit determines that an abnormality has occurred, the state control unit opens the inter-system switch, outputs a command to the power converter to discharge the storage battery, and closes the battery switch during a predetermined period including a period from output of the command to start of discharge of the storage battery.

3. The power supply system according to claim 2, wherein: The power converter performs a voltage boosting operation to boost the voltage of the battery when the battery is being discharged, and the state control unit turns off the battery switch after the battery starts being discharged.

4. The power supply system according to claim 1, wherein: The power converter performs a step-down operation to step down the voltage of the battery when the battery is charged, and performs a step-up operation to step up the voltage of the battery when the battery is discharged. The second path is provided with a rectifying element that restricts the flow of current from the connection point to the battery in the second path.

5. The power supply system according to claim 4, wherein: A semiconductor switch element having a parasitic diode is provided in the second path. The parasitic diode is the rectifying element, and the state control unit turns on the semiconductor switching element when the abnormality determination unit determines that an abnormality has occurred.

6. The power supply system according to any one of claims 1 to 5, wherein: The power supply system is a power supply system installed in a vehicle. The electric load is a load that implements at least one function required for driving of the vehicle and is a load that implements a driving assistance function of the vehicle. The vehicle is capable of traveling in a first mode using the driving assistance function and in a second mode not using the driving assistance function. The power supply system includes a mode control unit that allows the vehicle's travel mode to shift from the second mode to the first mode under the condition that the battery's state of charge is such that the battery's voltage is higher than a lower limit value of a drive voltage of the electric load.

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