JP2024049746A - Vehicle Power System - Google Patents

Abstract

[Problem] To enable a miniaturized and cost-reduced power supply system that supplies power to functional units in a vehicle equipped with functional units that function to ensure traffic safety. [Solution] The vehicle power supply system has a main power supply system having a main low-voltage power supply and a normal load, a backup power supply system having a backup low-voltage power supply and an important emergency load, and a vehicle control device. When an operation to start the load is performed, the vehicle control device executes a normality determination process before the load is started, and if the current flowing through the secondary switch during the normality determination process is equal to or greater than a threshold value, the vehicle control device closes the main switch and cuts off the secondary switch, and if the current flowing through the secondary switch during the normality determination process is less than the threshold value, the vehicle control device closes the main switch and cuts off the secondary switch after the normality determination process is completed. [Selected Figure] Figure 1

Description

The present invention relates to a vehicle power supply system.

In recent years, efforts to provide access to sustainable transportation systems that take into consideration vulnerable transport participants have been gaining momentum. To achieve this, we are focusing on research and development to further improve road safety and convenience through research and development into preventive safety. We are also focusing on research and development into autonomous driving as one technology that contributes to preventive safety.

In vehicles equipped with functional parts that function to ensure road safety, such as autonomous driving, it is necessary to stabilize the power supply to these functional parts. For example, Patent Document 1 discloses a system that can supply power to a load that functions for autonomous driving from a first power source and a third power source that are the vehicle's power sources, and can also supply power from a second power source that can be charged and discharged.

JP 2021-142810 A

In order to reliably operate loads that function to ensure safety, it is desirable to maintain a state in which power can be supplied to these loads. For this reason, for example, the system disclosed in Patent Document 1 includes a plurality of switches to enable power supply from a first power source and a second power source to the loads. It is desirable to adopt switches with sufficient current capacity, but if a switch with a large current capacity is adopted, the volume of the circuit and device will be large, leading to increased manufacturing costs. For this reason, it has been an issue when mounting a functional unit for ensuring traffic safety on a vehicle.
In order to solve the above problems, the present application aims to make it possible to reduce the size and cost of a power supply system that supplies power to a functional unit in a vehicle equipped with a functional unit that functions to ensure traffic safety, such as an autonomous driving system, thereby contributing to the development of a sustainable transportation system.

One aspect for achieving the above object is a vehicle power supply system comprising a main power supply system having a main low-voltage power supply and a normal load, and a backup power supply system having a backup low-voltage power supply and an important load for emergency use and connected to the main power supply system, the backup power supply system being capable of supplying power from the backup low-voltage power supply to the main power supply system, a main switch capable of switching between connection and disconnection with the main power supply system, and a backup power supply control device for controlling the main switch, the main switch being disconnected when not being controlled, a secondary switch being disposed in parallel with the main switch between the main power supply system and the backup power supply system and being connected when the main switch is not being controlled, and a secondary switch being connected to at least one of the normal load and the important load for emergency use. The vehicle power supply system has a vehicle control device capable of controlling the main power supply system and the backup power supply system, and when an operation is performed to start at least one of the normal load and the important emergency load, the vehicle control device starts the backup power supply control device based on the operation, executes a normality determination process to determine whether the backup power supply system is normal or not, and when the current flowing through the secondary switch during the normality determination process is equal to or greater than a threshold, the vehicle control device connects the main switch and cuts off the secondary switch, and when the current flowing through the secondary switch during the normality determination process is less than the threshold, the vehicle control device connects the main switch and cuts off the secondary switch after the normality determination process is completed.

According to the above configuration, the vehicle power supply system that enables power supply from the main power supply system and the backup power supply system to important loads in an emergency is operated so that a large current does not continuously flow to the secondary switch. This makes it possible to reduce the current capacity required of the secondary switch. This makes it possible to reduce the size and cost of the secondary switch, which in turn makes it possible to reduce the size and cost of the backup power supply system.

1 is a schematic configuration diagram of a vehicle power supply system according to an embodiment; 2 is a diagram showing an example of the arrangement of a current detection unit in the vehicle power supply system according to the embodiment; 3 is a flowchart showing the operation of the vehicle power supply system according to the embodiment. 4 is a flowchart showing a normality determination process performed by the vehicle power supply system according to the embodiment. 4 is a flowchart showing a normality determination process performed by the vehicle power supply system according to the embodiment. 3 is a timing chart showing the operation of the vehicle power supply system according to the embodiment. 3 is a timing chart showing the operation of the vehicle power supply system according to the embodiment. 3 is a timing chart showing the operation of the vehicle power supply system according to the embodiment. 3 is a flowchart showing the operation of the vehicle power supply system according to the embodiment.

Below, one embodiment of the vehicle power supply system of the present invention will be described with reference to the attached drawings.

[1. Configuration of vehicle power supply system]
[1-1. Overall configuration of vehicle power supply system]
Fig. 1 is a schematic diagram of a vehicle power supply system 1. In Fig. 1, solid lines indicate power lines, and dashed lines indicate signal lines.

The vehicle power supply system 1 of the vehicle V in this embodiment includes a main power supply system 10, a backup power supply system 20 connected to the main power supply system 10, a high-voltage power supply system 30, and a step-down device 40. The high-voltage power supply system 30 is connected to the main power supply system 10 and the backup power supply system 20 via the step-down device 40. The step-down device 40 steps down the power flowing through the high-voltage power supply system 30 and outputs it to the main power supply system 10 and/or the backup power supply system 20. The step-down device 40 is, for example, a DC/DC converter.

In this embodiment, as an example, a case will be described in which the vehicle V is an electric vehicle equipped with a rotating electric machine MG as a power source for traveling. The rotating electric machine MG is, for example, a three-phase motor, and generates driving force using electric power supplied by an inverter unit (not shown) to travel the vehicle V. The vehicle V is equipped with a drive unit 321 equipped with a rotating electric machine MG, which will be described later. The vehicle V is equipped with a high-voltage power supply 31 that supplies driving electric power to the drive unit 321. The drive unit 321 is a load that receives a supply of high-voltage electric power output by the high-voltage power supply 31, and is included in a high-voltage load 32, which will be described later.

The vehicle V may be a vehicle equipped with an internal combustion engine. The internal combustion engine may function as a power source for driving the vehicle V. Alternatively, the internal combustion engine may function as a power source for driving a generator (not shown) and charge a high-voltage power supply 31 (described later). In other words, the vehicle V may be an electric vehicle without an internal combustion engine, a hybrid vehicle equipped with an internal combustion engine and a rotating electric machine MG for driving the vehicle, or a vehicle driven by an internal combustion engine. The vehicle V is, for example, a vehicle capable of autonomous driving or automatic driving. When the vehicle V is equipped with an internal combustion engine, the high-voltage load 32 supplied with power from the high-voltage power supply 31 includes, for example, a starter motor.

[1-2. Configuration of main power supply system]
The main power supply system 10 includes a main low-voltage power supply 11 and a normal load 12 .

The main low-voltage power supply 11 is a power supply with a lower voltage than the high-voltage power supply 31. The main low-voltage power supply 11 outputs, for example, a direct current of 12 V. The main low-voltage power supply 11 is, for example, a secondary battery that can be charged and discharged. Specifically, the main low-voltage power supply 11 may be a lead battery, a lithium-ion battery, a lithium polymer battery, a lithium iron phosphate battery, a metal hydride battery, or other batteries.

The main low-voltage power supply 11 is provided on the connection line L11. One end of the connection line L11 is connected to a contact C11 formed on the connection line L10, and the other end is connected to a ground line having a reference potential of the vehicle power supply system 1. The positive side of the main low-voltage power supply 11 is connected to the contact C11 side of the connection line L11, and the negative side is connected to the ground line side of the connection line L11.

A normal load 12 is connected to one end of the connection line L10. The normal load 12 (EL in the figure) is an electric power load mounted on the vehicle V. The normal load 12 may be a single device or may include multiple devices. In this embodiment, the normal load 12 is a functional unit that performs functions related to the running of the vehicle V. The normal load 12 includes, for example, a load that performs functions related to the running operation, stopping operation, or driving control of the vehicle V. The normal load 12 operates at a lower voltage than the high-voltage load 32, and therefore can be called a low-voltage load in comparison with the high-voltage load 32. The normal load 12 may also include equipment in the vehicle V that is called an auxiliary device.

Specifically, the normal load 12 includes an ECU 50 (Electronic Control Unit) capable of executing driving control of the vehicle V. The ECU 50 shown in FIG. 1 may be composed of a single ECU, or may include multiple ECUs. For example, the normal load 12 may include some of the multiple ECUs equipped in the vehicle V. In addition, the normal load 12 may include a control unit (not shown) that is mounted on the vehicle V and is different from the ECU 50.

The normal load 12 may also include an auxiliary load used for braking the vehicle V, such as an automatic braking device. The normal load 12 may also include an auxiliary load used for steering the vehicle V, such as an automatic steering device. The normal load 12 may also include an auxiliary load used for acquiring external information about the vehicle V, such as LiDAR (Light Detection and Ranging). The normal load 12 may also include instruments, such as a wiper device, a power window device, and a meter panel.

[1-3. Configuration of backup power supply system]
The backup power supply system 20 includes a backup power supply unit 21 and an emergency important load 22 .

The backup power supply unit 21 includes a backup low-voltage power supply 23, a switching device 24, and a backup power supply control device 25 that controls the switching device 24.

The backup power supply unit 21 has a first external connection terminal T211, a second external connection terminal T212, and a ground terminal T213. The other end of the connection line L10 is connected to the first external connection terminal T211. The ground terminal T213 is connected to the ground line.

The emergency important load 22 (EL in the figure) is an electric power load mounted on the vehicle V. The emergency important load 22 may be a single device or may include multiple devices. The emergency important load 22 operates at a lower voltage than the high voltage load 32, and therefore can be called a low voltage load in comparison with the high voltage load 32.

The emergency important load 22 is connected to the second external connection terminal T212 of the backup power supply unit 21 by the connection line L21.

The switching device 24 has a first terminal T241, a second terminal T242, and a third terminal T243. The first terminal T241 is connected to a first external connection terminal T211 of the backup power supply unit 21 by a connection line L211. The second terminal T242 is connected to a second external connection terminal T212 of the backup power supply unit 21 by a connection line L212.

The switching device 24 includes a connection line L241 that connects the first terminal T241 and the second terminal T242. A first switch SW1 is provided on the connection line L241. In this embodiment, the first switch SW1 is a switch having a normally open type (N.O. type) contact. That is, the first switch SW1 is a contact that is maintained in an OFF state when no operation signal is applied to the first switch SW1, and maintains the connection line L241 in a disconnected state. When an operation signal is applied, the first switch SW1 is switched to an ON state, and connects the first terminal T241 and the second terminal T242.

For example, if the first switch SW1 is configured as an electromagnetic switch that opens and closes by electromagnetic force, the first switch SW1 is maintained in an off state when no electromagnetic force is generated by the operating current, and maintains the connection line L241 in an interrupted state.
The first switch SW1 may be an electromagnetic switch such as an electromagnetic contactor, an electromagnetic switch, or a relay, or may be a semiconductor switch element, or may be a circuit such as a DC/DC converter having a switching function.

The switching device 24 includes a connection line L242 that connects the connection line L241 and the third terminal T243. One end of the connection line L242 is connected to the connection line L241 at a contact C241 formed between the first switch SW1 and the second terminal T242 of the connection line L241, and the other end is connected to the third terminal T243.

A second switch SW2 is provided on the connection line L242. The second switch SW2 connects the connection line L242 in the on state and disconnects the connection line L242 in the off state.

The second switch SW2 may be an electromagnetic switch such as an electromagnetic contactor, an electromagnetic switch, or a relay, or may be a semiconductor switch element, or may be a circuit such as a DC/DC converter having a switching function. In this embodiment, the second switch SW2 is a DC/DC converter. Therefore, as described below, when the second switch SW2 is in the on state, the second switch SW2 is capable of increasing or decreasing the voltage output from the connection line L242 to the contact C241. In other words, the second switch SW2 in this embodiment has the function of connecting and disconnecting the connection line L242 and the function of converting the voltage output from the connection line L242 to the contact C241.

The switching device 24 includes a connection line L243 that is connected in parallel to the connection line L241. One end of the connection line L243 is connected to a contact C242 formed between the first terminal T241 of the connection line L241 and the first switch SW1. The other end of the connection line L243 is connected to a contact C243 formed between the contact C241 of the connection line L241 and the second terminal T242. A third switch SW3 is provided on the connection line L243.

In this embodiment, the third switch SW3 is a switch having a normally closed type (N.C. type) contact. That is, the third switch SW3 is a contact that is maintained in the on state when no operation signal is applied to the third switch SW3. When an operation signal is applied to the third switch SW3, the third switch SW3 switches to the off state, and the connection line L243 is in the connected state.

For example, if the third switch SW3 is configured as an electromagnetic switch that opens and closes by electromagnetic force, the third switch SW3 is maintained in an on state when no electromagnetic force is generated by the operating current, and maintains the connection line L243 in a connected state.
The third switch SW3 may be an electromagnetic switch such as an electromagnetic contactor, an electromagnetic switch, or a relay, or may be a semiconductor switch element, or may be a circuit such as a DC/DC converter having a switching function.

In this embodiment, the first switch SW1 and the third switch SW3 are modularized as a switch module 241. The specific configuration of the switch module 241 is not limited, and for example, the switch module 241 may be a single semiconductor device or a circuit including multiple devices.

The switching device 24 includes a connection line L244 that connects the connection line L241 to the ground line. One end of the connection line L244 is connected to a contact C244 formed between the first switch SW1 of the connection line L241 and the contact C241. The other end of the connection line L244 is connected to the ground line. A capacitor CP is provided on the connection line L244.

The backup low-voltage power supply 23 is a power supply with a lower voltage than the high-voltage power supply 31. The backup low-voltage power supply 23 outputs, for example, a direct current of 12 V. The backup low-voltage power supply 23 is, for example, a secondary battery that can be charged and discharged. Specifically, the backup low-voltage power supply 23 may be a lead battery, a lithium ion battery, a lithium polymer battery, a lithium iron phosphate battery, a metal hydride battery, or other batteries.

The backup low-voltage power supply 23 is provided on the connection line L213. One end of the connection line L213 is connected to the third terminal T243 of the switching device 24. The other end of the connection line L213 is connected to the ground line. The backup low-voltage power supply 23 is provided on the connection line L213 so that the positive side is on the third terminal T243 side of the switching device 24 and the negative side is on the ground line side.

When the second switch SW2 is in the on state, the backup low-voltage power supply 23 supplies power to the backup power supply system 20 through the connection line L213 and the connection line L242 of the switching device 24. The power output from the backup low-voltage power supply 23 is stepped up or down to the desired voltage by the second switch SW2 and supplied to the backup power supply system 20. When the second switch SW2 is in the off state, the connection line L242 of the switching device 24 is cut off, so that no power is supplied from the backup low-voltage power supply 23 to the backup power supply system 20.

As described above, in the backup power supply system 20, a first switch SW1 having a normally open contact and a third switch SW3 having a normally closed contact are connected in parallel between the first terminal T241 and the second terminal T242.

When at least one of the first switch SW1 and the third switch SW3 is in the on state, the backup power supply system 20 is connected to the main power supply system 10. In this state, it becomes possible to supply power from the backup low-voltage power supply 23 to the main power supply system 10 through the first external connection terminal T211, and it is also possible to supply power from the main low-voltage power supply 11 to the important load in an emergency 22.

On the other hand, when both the first switch SW1 and the third switch SW3 are in the off state, the connection between the backup power supply system 20 and the main power supply system 10 is cut off.

The backup power supply control device 25 (BMS in the figure) is connected to the first switch SW1, the second switch SW2, and the third switch SW3 by signal lines. The backup power supply control device 25 controls the switching of the first switch SW1, the second switch SW2, and the third switch SW3 according to the control of the ECU 50. The backup power supply control device 25 includes a processor such as a CPU (Central Processing Unit), and controls the backup power supply system 20 through cooperation between software and hardware by executing a program using the processor. In this case, the backup power supply control device 25 may include a storage unit that stores programs and data, and the storage unit is, for example, a ROM (Read Only Memory). The backup power supply control device 25 may be configured with programmed hardware.

The backup power supply control device 25 outputs an operation signal through a signal line to each of the first switch SW1, the second switch SW2, and the third switch SW3. The backup power supply control device 25 can switch between a state in which an operation signal is output and a state in which an operation signal is not output to each of the first switch SW1, the second switch SW2, and the third switch SW3.

The first switch SW1 is a normally open switch. The backup power supply control device 25 switches the first switch SW1 from an off state to an on state by outputting an operation signal to the first switch SW1. The third switch SW3 is a normally closed switch. The backup power supply control device 25 switches the third switch SW3 from an on state to an off state by outputting an operation signal to the third switch SW3.

The backup power supply control device 25 outputs an operation signal to the second switch SW2, thereby switching the second switch SW2 between an on state and an off state. The backup power supply control device 25 also outputs an operation signal to the second switch SW2, thereby controlling the step-up or step-down of the second switch SW2. In other words, the backup power supply control device 25 controls the output voltage of the second switch SW2.

The backup power supply control device 25 operates by receiving power from, for example, the high-voltage power supply unit 36 or the backup low-voltage power supply 23.

In this embodiment, the important emergency load 22 is a functional unit that performs functions related to the traveling of the vehicle V, and includes, for example, a load that performs functions related to the traveling operation, stopping operation, or driving control of the vehicle V. The important emergency load 22 includes a load that performs functions to respond to an emergency while the vehicle V is traveling. Specifically, the important emergency load 22 includes a load that performs functions related to the execution of a minimal risk maneuver (MRM) related to the traveling of the vehicle V. For example, the MRM includes an operation or control that corresponds to at least one of the minimum necessary traveling operation, stopping operation, and driving control to safely move the vehicle V to the shoulder of the road and stop it even if the driving force of the driving source is lost.

The emergency important load 22 may include a part or all of the aforementioned ECU 50 capable of executing driving control of the vehicle V. The emergency important load 22 may be a control unit mounted on the vehicle V and may include a control unit (not shown) different from the ECU 50.

The emergency important load 22 may include an auxiliary load used for braking the vehicle V, such as an automatic braking device. The emergency important load 22 may include an auxiliary load used for steering the vehicle V, such as an automatic steering device. The emergency important load 22 may include an auxiliary load used for acquiring external information of the vehicle V, such as LiDAR.

Some of the loads included in the emergency important load 22 may overlap with the loads included in the normal load 12 of the main power system 10. That is, some of the normal loads 12 may also be the emergency important load 22, and this load belongs to both the main power system 10 and the backup power system 20. With this configuration, the emergency important load 22 can be made redundant. In other words, the emergency important load 22 that overlaps with the normal load 12 of the main power system 10 can operate with the power supplied to the main power system 10 and can also operate with the power supplied to the backup power system 20. Therefore, the emergency important load 22 that overlaps with the normal load 12 of the main power system 10 can operate even if an abnormality occurs in the main power system 10, and can perform operation even if an abnormality occurs in the backup power system 20.

In the above configuration, the first switch SW1 corresponds to an example of a main switch, the second switch SW2 corresponds to an example of a backup power switch, and the third switch SW3 corresponds to an example of a secondary switch.
Here, the reason why the first switch SW1 is called a main switch and the third switch SW3 is called a secondary switch is because the current capacity of the third switch SW3 can be made smaller than that of the first switch SW1. The names main switch and secondary switch do not mean that the on/off state of the third switch SW3 is restricted by the on/off state of the first switch SW1. The backup power supply control device 25 can set the first switch SW1 and the third switch SW3 to an on state and an off state independently of each other.

[1-4. Configuration of high-voltage power supply system]
The high-voltage power supply system 30 includes a high-voltage power supply 31 and a high-voltage load 32 .

The high-voltage power supply 31 is a power supply that supplies power at a higher voltage than the main low-voltage power supply 11 and the backup low-voltage power supply 23. The high-voltage power supply 31 is, for example, a secondary battery that can be charged and discharged. Specifically, the high-voltage power supply 31 may be a lithium-ion battery, a lithium polymer battery, a lithium iron phosphate battery, a metal hydride battery, or other batteries. The high-voltage power supply 31 outputs, for example, a direct current of 200 V.

The high-voltage power supply 31 is connected to the connection line L31. One end of the connection line L31 is connected to the ground line, and the negative side of the high-voltage power supply 31 is connected to the ground line side of the connection line L31.

The high-voltage load 32 is an electric power load that operates at a higher voltage than the normal load 12 and the important emergency load 22, and is operated by electric power supplied from the high-voltage power source 31. In this embodiment, the high-voltage load 32 includes a drive unit 321 that drives the vehicle V, and an air conditioner 322 (A/C in the figure) that conditions the air in the passenger compartment of the vehicle V.

The drive unit 321 includes a rotating electric machine MG and a power control unit PCU that controls the rotating electric machine MG. The power control unit PCU includes a DC/DC converter (not shown) and an inverter (not shown), etc.

The drive unit 321 is connected to the other end of the connection line L31. The drive unit 321 converts the DC power supplied from the high-voltage power supply 31 into three-phase AC power using the power control unit PCU and supplies it to the rotating electric machine MG. As a result, the rotating electric machine MG generates power to drive the vehicle V using the power from the high-voltage power supply 31.

The drive unit 321 causes the rotating electric machine MG to function as a regenerative brake when braking the vehicle V. In this case, the drive unit 321 may convert the three-phase AC power generated by the rotating electric machine MG into DC power in the power control unit PCU and charge the high-voltage power supply 31.

The air conditioner 322 is connected to a connection line L32 that connects to the connection line L31 at a contact C31 formed between the high-voltage power supply 31 of the connection line L31 and the drive unit 321. The air conditioner 322 is operated by power from the high-voltage power supply 31.

[1-5. Configuration of step-down device]
The step-down device 40 is provided on the connection line L40. One end of the connection line L40 is connected to a contact C32, and the other end is connected to a contact C12. The contact C32 is a contact formed between the high-voltage power source 31 and the contact C31 of the connection line L31. The contact C12 is a contact formed between the contact C11 of the connection line L10 and the other end of the connection line L10. Here, the other end of the connection line L10 corresponds to the first external connection terminal T211 of the backup power supply system 20.

In this way, the high-voltage power supply system 30 is connected to the main power supply system 10 and the backup power supply system 20 via the step-down device 40.

The step-down device 40 reduces the power flowing through the high-voltage power supply system 30. The step-down device 40 is, for example, a DC/DC converter. The step-down device 40 reduces the voltage output by the high-voltage power supply system 30 and supplies it to the main power supply system 10 and the backup power supply system 20.

The step-down device 40 can be switched between a connected state and a disconnected state. When the step-down device 40 is in a connected state, the high-voltage power supply system 30 is connected to the main power supply system 10 and the backup power supply system 20 via the connection line L40 and the step-down device 40. When the step-down device 40 is in a disconnected state, the high-voltage power supply system 30 is disconnected from the main power supply system 10 and the backup power supply system 20.

The high-voltage power supply 31 and the step-down device 40 constitute the high-voltage power supply unit 36. The high-voltage power supply unit 36 is capable of outputting a voltage higher than the rated voltage of the backup power supply system 20. The high-voltage power supply unit 36 may also be capable of outputting a voltage higher than the rated voltage of the main low-voltage power supply 11.

As described above, when the vehicle V is a vehicle having an internal combustion engine, the vehicle V is equipped with a generator driven by the power of the internal combustion engine. This generator supplies the generated AC current to the high-voltage power supply 31 via a boost circuit or a rectifier circuit (not shown), thereby charging the high-voltage power supply 31. In addition, the AC current output by the generator may be supplied to the step-down device 40 directly or via a boost circuit or a rectifier circuit (not shown).

The vehicle power supply system 1 includes an ECU 50. As described above, the ECU 50 may include multiple ECUs, or may be a single device. The ECU 50 corresponds to an example of a vehicle control device.

The ECU 50 is connected to the normal load 12, the important emergency load 22, the backup power supply control device 25, and the high-voltage load 32 by signal lines. The devices to which the ECU 50 is connected are not limited to the above-mentioned components. The ECU 50 may be connected to devices installed in the vehicle V that are not shown in FIG. 1.

The ECU 50 includes a processor such as a CPU, and controls each part of the vehicle power supply system 1 through cooperation between software and hardware by executing a program using the processor. In this case, the ECU 50 may include a storage unit that stores programs and data, and the storage unit is, for example, a ROM. The ECU 50 may also be configured with programmed hardware.

An operation unit 55 is connected to the ECU 50. The operation unit 55 includes switches and the like operated by the user of the vehicle V. For example, the operation unit 55 includes a start stop switch (SSSW) 56 that the user operates to instruct the vehicle V to start and stop. The operation unit 55 also includes switches and the like with which the user instructs the vehicle V to perform autonomous driving. The operation unit 55 may be a wireless communication device that is wirelessly connected to a remote control device (not shown) and detects operations by the remote control device. Here, the user of the vehicle V is, for example, the driver of the vehicle V, but may also include a person other than the driver who uses the vehicle V.

When the vehicle V is stopped, the vehicle power supply system 1 is in an off state, which will be described later. When the vehicle power supply system 1 is in an off state, the ECU 50 maintains an operable state by using power supplied from the high-voltage power supply 31. This state may be a so-called sleep state or low power consumption state. In the sleep state or low power consumption state, the ECU 50 may be in a state in which power supply to some components of the ECU 50 is stopped, for example. In addition, in the sleep state or low power consumption state, the operating clock number of the ECU 50 and the sampling frequency at which the ECU 50 detects the state of the SSSW 56 and other sensors may be set to a longer period than when the vehicle V is operating.

When the vehicle power supply system 1 is in the off state, power is supplied to the normal load 12 and the emergency important load 22. This is to operate the emergency important load 22 and the normal load 12 when the vehicle power supply system 1 is in the off state. For example, the ECU 50 may monitor the detection value of a sensor included in the emergency important load 22 or a sensor connected to the emergency important load 22. In addition, for example, a function of monitoring the surroundings of the parked vehicle V may be executed by a camera included in the emergency important load 22. In such a case, power is supplied from the high-voltage power supply unit 36 to the emergency important load 22 in order to operate the emergency important load 22. Similarly, power is supplied from the high-voltage power supply unit 36 to the normal load 12. These powers are so-called dark currents. As described above, since the third switch SW3 is a normally closed type, power can be supplied from the main power supply system 10 to the emergency important load 22 via the third switch SW3 even when the backup power supply control device 25 is stopped.

When the ECU 50 detects an operation of the SSSW 56 while the vehicle V is stopped, the ECU 50 starts the normal load 12, the important emergency load 22, the high-voltage load 32, etc. The ECU 50 starts the backup power supply control device 25, and causes the backup power supply control device 25 to control the first switch SW1, the second switch SW2, and the third switch SW3. This starts the vehicle V from a stopped state. In the started state, the vehicle V can run according to the user's operation.

When the ECU 50 detects an operation of the SSSW 56 while the vehicle V is running, it stops the normal load 12, the important emergency load 22, the high voltage load 32, etc. This causes the vehicle V to transition to a stopped state. In this case, the ECU 50 may control the backup power supply control device 25 to execute control over the first switch SW1, the second switch SW2, and the third switch SW3 to stop the vehicle V.

In the vehicle power supply system 1, when the vehicle V is in a start-up state, power is supplied from the high-voltage power supply 31 to each part of the main power supply system 10. Furthermore, power is supplied from the high-voltage power supply unit 36 to the main power supply system 10 and the emergency important load 22. When the vehicle V is in a stopped state, a dark current flows from the high-voltage power supply unit 36 to the emergency important load 22 as described above.

However, if a short circuit or ground fault occurs in the main power supply system 10, the power supply from the high-voltage power supply unit 36 to the emergency important load 22 may be stopped in order to protect the vehicle power supply system 1. For example, fuses (not shown) are provided at multiple locations in the circuits that make up the vehicle power supply system 1. If a ground fault or short circuit occurs, the fuses provided in the connection lines L31, L32, L40, etc. will blow, and the power supply from the high-voltage power supply unit 36 to the emergency important load 22 will stop. In addition, the protection function may shut off the output of the step-down device 40.

Even in such a case, the vehicle power supply system 1 can supply power from the backup low-voltage power supply 23 to the emergency important load 22 so that the power supply to the emergency important load 22 is not interrupted. Specifically, when the second switch SW2 is switched on, the backup low-voltage power supply 23 is connected to the connection line L212, and power supply from the backup low-voltage power supply 23 to the emergency important load 22 is started. Alternatively, while the emergency important load 22 is operating during startup of the vehicle V, the second switch SW2 is in a state by the backup power supply control device 25, and a configuration may be used in which the power supply from the step-down device 40 to the backup power system 20 is interrupted. In this case, the output voltage of the second switch SW2 may be adjusted in response to the output voltage of the step-down device 40 so that no current flows from the second switch SW2 in the direction toward the step-down device 40.

The vehicle power supply system 1 may be configured to be capable of charging the main low-voltage power supply 11 and the backup low-voltage power supply 23 with power supplied by the high-voltage power supply unit 36. Specifically, when the charging capacity of the main low-voltage power supply 11 decreases, the main low-voltage power supply 11 may be charged with power output by the step-down device 40 under the control of the ECU 50 or the backup power supply control device 25. The same applies to the backup low-voltage power supply 23.

[1-6. Current detection unit]
The vehicle power supply system 1 includes a current detector 27 that detects a current flowing through the third switch SW3. The current detector 27 is disposed on the circuit of the backup power supply system 20 and is connected to the backup power supply control device 25.

Figure 2 is a diagram showing an example of the arrangement of the current detection unit 27 in the vehicle power supply system 1. Figure 2 shows current detection units 27a, 27b, and 27c as examples of the current detection unit 27.

The current detection units 27a and 27b are disposed between the emergency important load 22 and the switch module 241. The current detection unit 27a is located between the emergency important load 22 and a contact C241 connected to the backup low-voltage power supply 23. The current detection unit 27a detects the current flowing through the emergency important load 22 when power is supplied to the emergency important load 22 from at least one of the main low-voltage power supply 11, the emergency important load 22, and the high-voltage power supply unit 36.

The current detection unit 27b is located between the switch module 241 and the contact C241. When power is supplied to the emergency important load 22 from either the main low-voltage power supply 11 or the high-voltage power supply unit 36, the current detection unit 27b detects the current flowing to the emergency important load 22 through the switch module 241. The current flowing from the backup low-voltage power supply 23 to the emergency important load 22 is not detected by the current detection unit 27b.

The current detection unit 27c is disposed between the third switch SW3 and the emergency important load 22. The current detection unit 27c is connected to a contact C243 where the third switch SW3 is connected to the emergency important load 22 and to a contact of the third switch SW3 on the emergency important load 22 side. The current detection unit 27c detects the current flowing through the third switch SW3 when power is supplied to the emergency important load 22 from the main low voltage power supply 11 or the high voltage power supply unit 36. The current detection unit 27c is not suitable for the purpose of detecting the current flowing through the first switch SW1 and the current flowing from the backup low voltage power supply 23 to the emergency important load 22.

The backup power supply control device 25 can detect the current flowing through the third switch SW3 by using the current detection units 27a, 27b, and 27c. For example, the backup power supply control device 25 can detect the current flowing through switch SW3 by using the current detection unit 27a with the first switch SW1 and the second switch SW2 turned off. Also, for example, the backup power supply control device 25 can detect the current flowing through switch SW3 by using the current detection unit 27b with the first switch SW1 turned off. Also, the backup power supply control device 25 can detect the current flowing through switch SW3 by using the current detection unit 27c, regardless of the state of the first switch SW1 and the second switch SW2.

If the vehicle power supply system 1 is configured to include at least one of the current detection units 27a, 27b, and 27c, the backup power supply control device 25 can detect the current flowing through the third switch SW3. The backup power supply control device 25 outputs the detected current value to the ECU 50. The current detection units 27a, 27b, and 27c are specific examples of the current detection unit 27, and the vehicle power supply system 1 only needs to include at least one of the current detection units 27a, 27b, and 27c, and the current detection unit 27 may be located in another position in the vehicle power supply system 1. In the following description, when there is no need to distinguish between the current detection units 27a, 27b, and 27c, they will be referred to as the current detection unit 27.

2. Vehicle Power System Operation
[2-1. Starting up the vehicle power supply system]
The operation of the vehicle power supply system 1 will now be described.
FIG. 3 is a flowchart showing the operation of vehicle power supply system 1, and illustrates the operation when vehicle power supply system 1 transitions from an off state to an on state.

The on state of the vehicle power supply system 1 refers to a state in which the drive source of the vehicle V is activated and the power required to drive the vehicle V is supplied to the auxiliary equipment required for driving. The drive source being activated means that the drive source can operate immediately to drive the vehicle V. The on state can be rephrased as a state in which the vehicle V is running, or a state in which the vehicle V can run immediately. In this embodiment, the on state of the vehicle power supply system 1 refers to a state in which the drive unit 321 is activated and the normal load 12 and the emergency important load 22 are activated.

The off state of the vehicle power supply system 1 is a state in which the drive source of the vehicle V is not activated, and the power required to drive the vehicle V is not supplied to the auxiliary equipment required for running. In this embodiment, the off state of the vehicle power supply system 1 refers to a state in which the high-voltage load 32 including the drive unit 321 is not activated, the normal load 12 and the important emergency load 22 are not activated, and standby power is supplied to the normal load 12 and the important emergency load 22. As described above, the current flowing from the main power supply system 10 to the normal load 12 and the important emergency load 22 when the vehicle power supply system 1 is off is called a dark current.

When the vehicle power supply system 1 is in the off state, it transitions to the on state when an on operation is performed, which is a trigger. The on operation refers to, for example, an on operation of an operation unit provided in the vehicle V by the user of the vehicle V. The operation unit is, for example, the SSSW 56.

When the vehicle power supply system 1 is in the on state, it transitions to the off state when an off operation is executed as a trigger. The off operation refers to, for example, an operation unit such as the SSSW 56 provided in the vehicle V being operated by the user of the vehicle V.

When the vehicle V has an internal combustion engine, the on state of the vehicle power supply system 1 can be said to be a state in which the internal combustion engine is running, and the normal load 12 and the emergency important load 22 are running. In this case, the off state is a state in which the internal combustion engine is not running, the normal load 12 and the emergency important load 22 are not running, and standby power is supplied to the normal load 12 and the emergency important load 22.

When the vehicle V has an internal combustion engine, the operation to turn on the vehicle power supply system 1 is, for example, an ignition operation of the vehicle V, specifically, an operation to turn on the ignition switch. Furthermore, the operation to turn off the vehicle power supply system 1 is an operation to turn off the ignition switch. The SSSW 56 can be said to be an example of an ignition switch.

The standby power of the normal loads 12 and the emergency important loads 22 is the dark current described above, and is supplied from the main power supply system 10 to the normal loads 12 and the emergency important loads 22.

The operation of the vehicle power supply system 1 described below is realized by executing a program pre-stored in the ECU 50 and the backup power supply control device 25 mounted on the vehicle V.

The operation shown in FIG. 3 may be executed by either the ECU 50 or the backup power supply control device 25. In this embodiment, an example in which the ECU 50 executes the operation shown in FIG. 3 will be described.

When the ECU 50 detects the operation of the SSSW 56 while the vehicle power supply system 1 is in the off state (step S11), it starts the backup power supply system 20 (step S12). In step S12, the ECU 50 starts the power supply to the backup power supply control device 25. Furthermore, the ECU 50 transitions the backup power supply control device 25 to a state in which the first switch SW1, the second switch SW2, and the third switch SW3 can be switched.

Then, the ECU 50 executes a normality determination process by controlling the backup power supply control device 25 (step S13). The normality determination process is a process for determining whether or not the backup power supply system 20 is normal. If the ECU 50 determines in the normality determination process that the backup power supply system 20 is normal, the ECU 50 proceeds to the next step S14. Details of the normality determination process will be described later with reference to Figures 4 and 5.

After the normality determination process, the backup power supply control device 25 switches the first switch SW1 on under the control of the ECU 50 (step S14). After the switching of the first switch SW1 is completed, the backup power supply control device 25 switches the third switch SW3 off under the control of the ECU 50 (step S15). After the third switch SW3 is switched off, the ECU 50 starts up the normal load 12 and the emergency important load 22 (step S16). This causes the vehicle power supply system 1 to transition to the on state.

[2-2. Normality Judgment Process]
4 and 5 are flowcharts showing the operation of the vehicle power supply system 1, and show in detail the normality determination process executed in step S13 in Fig. 3. The normality determination process is a process for determining whether the backup power supply system 20 is normal or not, and here, as an example, a process for determining whether a switch provided in the backup power supply unit 21 operates normally or not will be described.

The events in which the first switch SW1, the second switch SW2, and the third switch SW3 do not operate normally are specifically stuck on and stuck off. Stuck on and stuck off are a type of switch failure mode, and are events in which the switch contacts are fixed on or off. Here, the switches include the first switch SW1, the second switch SW2, and the third switch SW3. For example, in a mechanical switch having contacts, if an arc occurs due to opening and closing of the contacts, or if a current exceeding the rated value flows through the contacts, the contacts may melt. In this case, the switch is fixed in the on state, resulting in a stuck on failure. Stuck off occurs when the contacts are fixed in a non-connected state due to contact wear due to life or breakage. When a stuck on or off occurs in any of the first switch SW1, the second switch SW2, and the third switch SW3, the switch is fixed in the on state or the off state regardless of the control of the backup power control device 25. In such a case, the ECU 50 determines that the backup power supply unit 21 is not operating normally.

In the operation example shown in FIG. 4 and FIG. 5, it is determined whether each of the first switch SW1, the second switch SW2, and the third switch SW3 is stuck on or stuck off.
Steps S21-S24 in Fig. 4 are a process for determining whether or not the third switch SW3 is stuck off, and are referred to as a first determination process. Steps S25-S31 in Fig. 4 are a process for determining whether or not the first switch SW1 and the third switch SW3 are stuck on, and whether or not the second switch SW2 is stuck off, and are referred to as a second determination process. Steps S41-S44 in Fig. 5 are a process for determining whether or not the first switch SW1 is stuck off, and are referred to as a third determination process. Steps S45-S48 are a process for determining whether or not the second switch SW2 is stuck on, and are referred to as a fourth determination process.

In step S13, the ECU 50 may omit some of the processes shown in Figures 4 and 5. In other words, the ECU 50 may execute one or more of the first to fourth determination processes in step S13. In addition, the order in which the first to fourth determination processes are executed is not limited to the order shown in Figures 4 and 5, and the order may of course be changed as appropriate.

In this embodiment, an example will be described in which the ECU 50 executes the normality determination process. However, the backup power supply control device 25 may execute the normality determination process.
The ECU 50 executes a first determination process in steps S21 to S24. The ECU 50 turns the first switch SW1 off, turns the second switch SW2 off, and turns the third switch SW3 on (step S21).

The ECU 50 measures or detects the potential P1 of the main power supply system 10 and the potential P2 of the backup power supply system 20 (step S22). The potential P1 is, for example, the potential at the contact C12 shown in FIG. 1 or at a position equipotential to the contact C12. The potential P2 is the potential at the second external connection terminal T212 or at a position equipotential to the second external connection terminal T212.

The ECU 50 compares the potential P1 with the potential P2 and determines whether the difference between the potential P1 and the potential P2 is equal to or less than a predetermined value (step S23). The predetermined value used for the determination in step S23 is a value that is set in advance in the ECU 50. The predetermined value in step S23 and the predetermined values in steps S27, S30, S44, and S48 described below are each values that are set in the ECU 50, and may be the same value or different values.

If the ECU 50 determines that the difference between the potentials P1 and P2 is not equal to or less than the predetermined value, i.e., is greater than the predetermined value (step S23; NO), the ECU 50 determines that the third switch SW3 is stuck off (step S24). In this case, the ECU 50 proceeds to step S29, which will be described later.

If it is determined that the difference between potential P1 and potential P2 is equal to or less than the predetermined value (step S23; YES), the ECU 50 executes the second determination process in steps S25-S31. The ECU 50 turns the first switch SW1 off, turns the second switch SW2 on, and turns the third switch SW3 off (step S25). The ECU 50 measures or detects the potentials P1 and P2 (step S26). The potentials P1 and P2 are the potentials at the above-mentioned positions. The ECU 50 determines whether the difference between potential P1 and potential P2 is equal to or less than the predetermined value (step S27).

When the ECU 50 determines that the difference between the potential P1 and the potential P2 is equal to or less than a predetermined value (step S27; YES), the ECU 50 determines that the first switch SW1 or the third switch SW3 is stuck on (step S28). In this case, the ECU 50 proceeds to step S29, performs an operation of outputting a switch abnormality (step S29), and ends the normality determination process. The output of step S29 is an output indicating that the backup power supply unit 21 is not normal. For example, the ECU 50 displays an error code corresponding to the switch abnormality or a warning on a display (not shown) mounted on the vehicle V. The ECU 50 also stores information related to the error indicating an abnormality in the switch of the backup power supply unit 21 in the built-in memory unit. After step S29, the ECU 50 may stop the process of FIG. 3 and maintain the vehicle power supply system 1 in the off state.

If the ECU 50 determines that the difference between the potentials P1 and P2 is greater than a predetermined value (step S27; NO), it determines whether the potential P2 is equal to or less than a preset predetermined value (step S30). If the potential P2 is equal to or less than the predetermined value (step S30; YES), the ECU 50 determines that the second switch SW2 is stuck off (step S31) and proceeds to step S29.

If it is determined that the potential P2 is higher than the predetermined value (step S30; NO), the ECU 50 executes the third determination process of FIG. 5. The ECU 50 turns on the first switch SW1, turns on the second switch SW2, and turns off the third switch SW3 (step S41). The ECU 50 measures or detects the potentials P1 and P2 (step S42). The potentials P1 and P2 are the potentials at the above-mentioned positions. The ECU 50 determines whether the difference between the potentials P1 and P2 is equal to or less than a predetermined value (step S43).

If the ECU 50 determines that the difference between potential P1 and potential P2 is greater than the predetermined value (step S43; NO), it determines that the first switch SW1 is stuck off (step S44) and proceeds to step S29.

When the ECU 50 determines that the difference between the potentials P1 and P2 is equal to or less than a predetermined value (step S43; YES), the ECU 50 executes a fourth determination process. The ECU 50 turns the first switch SW1 on, turns the second switch SW2 off, and turns the third switch SW3 off (step S45). The ECU 50 measures or detects the potential P2 and the output potential P3 of the backup low-voltage power supply 23 (step S46). The output potential P3 is, for example, the potential of the positive electrode of the backup low-voltage power supply 23, for example, the potential of the third terminal T243 in FIG. 1.

The ECU 50 determines whether the difference between the potential P2 and the output potential P3 is equal to or less than a predetermined value (step S47). If the ECU 50 determines that the difference between the potential P2 and the output potential P3 is equal to or less than the predetermined value (step S47; YES), it determines that the second switch SW2 is stuck on (step S48) and proceeds to step S29.

When the ECU 50 determines that the difference between the potential P2 and the output potential P3 is greater than a predetermined value (step S47; NO), it determines that the first switch SW1, the second switch SW2, and the third switch SW3 are normal (step S49). This means that it determines that the backup power supply unit 21 is operating normally. In this case, the ECU 50 normally completes the normality determination process (step S50) and proceeds to step S14 in FIG. 3.

[2-3. Changes in current when starting up a vehicle power supply system]
Fig. 6 is a timing chart showing the process in which the vehicle power supply system 1 transitions from an off state to an on state. In Fig. 6, (a) shows the operation state of the SSSW 56, and (b) shows the power consumption of the emergency important load 22. Fig. 6(c) shows the state of the third switch SW3, (d) shows the state of the first switch SW1, and (e) shows the state of the backup power supply unit 21. (f) shows the magnitude of the current I3 flowing through the third switch SW3.

In FIG. 6, the timing when the ECU 50 detects the operation of the SSSW 56 is designated as time T1. Since the vehicle power supply system 1 is in the off state at time T1, the third switch SW3 is in the on state and the first switch SW1 is in the off state as shown in FIGS. 6(c) and (d). Also, as shown in FIG. 6(b), the emergency important load 22 is in a sleep state and consumes little power. At time T1, a dark current I3 flows through the third switch SW3 from the main power supply system 10 to the emergency important load 22 as shown in FIG. 6(e).

When the ECU 50 detects the operation of the SSSW 56, it starts the backup power supply system 20 as shown in FIG. 6(e) and executes the normality determination process. In the normality determination process, as in the above example, the presence or absence of a failure in the first switch SW1, the second switch SW2, and the third switch SW3 is determined. During the normality determination process, the third switch SW3 is maintained in the ON state, and the first switch SW1 is maintained in the OFF state. In the above example, the operation of switching the first switch SW1 and the third switch SW3 to the ON state and the OFF state is executed several times during the normality determination process. Therefore, strictly speaking, during the normality determination process, there are periods during which the third switch SW3 is in the OFF state and periods during which the first switch SW1 is in the ON state, but these periods are relatively short, so the states of the first switch SW1 and the third switch SW3 can be regarded as shown in FIG. 6.

The timing when the normality determination process is completed is time T2. At time T2, the first switch SW1, the third switch SW3, and the emergency important load 22 maintain the off state of the vehicle power supply system 1. The ECU 50 switches the first switch SW1 on at time T2. At time T3, after this switching is completed, the ECU 50 switches the third switch SW3 off. As the first switch SW1 turns on at time T2, the current I3 flowing through the third switch SW3 decreases at time T2. Furthermore, as the third switch SW3 turns off at time T3, the current I3 becomes 0 [A] at time T3.

After the third switch SW3 is turned off at time T3, the ECU 50 starts the emergency important load 22 at time T4. Time T4 is the timing when the ignition is turned on in a vehicle V equipped with an internal combustion engine. Time T4 can be said to be the timing when the vehicle power supply system 1 is turned on.

At times T1 to T4, the current I3 flowing through the third switch SW3 is equivalent to or smaller than the dark current flowing through the emergency important load 22 when the vehicle power supply system 1 is in the off state. The value of the current I3 in this case is smaller than the current flowing from the main power supply system 10 to the emergency important load 22 when the vehicle power supply system 1 is in the on state. When the vehicle power supply system 1 is in the on state, the current flowing from the main power supply system 10 to the emergency important load 22 passes through the first switch SW1, so no large current flows through the third switch SW3.

In this way, the current flowing through the third switch SW3 is smaller than that through the first switch SW1, so a switch with a smaller current capacity than the first switch SW1 can be used as the third switch SW3. This allows a switch with a simple configuration to be used as the third switch SW3, making it possible to reduce the size and cost of the backup power supply unit 21.

Some of the important emergency loads 22 start up and consume power in a short time after the ECU 50 accepts the operation of the SSSW 56. The important emergency loads 22 mounted on the vehicle V have various functions and types, and there are important emergency loads 22 that start up before the ignition of the vehicle V is turned on at time T4. In a vehicle V equipped with this type of important emergency load 22, the state of the vehicle power supply system 1 at startup changes, for example, as shown in FIG. 7.

Figure 7 is a timing chart showing another example of the process in which the vehicle power supply system 1 transitions from the off state to the on state. (a) to (f) in Figure 7 and times T1 to T4 are the same as those in Figure 6.

In the example of FIG. 7, some of the emergency important loads 22 start up before time T2 when the normality determination process of the backup power supply system 20 is completed. The timing of this start-up is time T11. At time T11, the power consumption of the emergency important loads 22 rises as indicated by the symbol PO. At time T11, the third switch SW3 is on and the first switch SW1 is off, so the power consumed by the emergency important loads 22 is supplied through the third switch SW3. Therefore, the current I3 of the third switch SW3 rises at time T11 in FIG. 7(f). This rise in current I3 is called the peak current PC1.

In order to configure the third switch SW3 so that it can also handle the operation example of FIG. 7, the current capacity of the third switch SW3 needs to be greater than the current value of the peak current PC1. For example, the third switch SW3 needs to have a current capacity equivalent to that of the first switch SW1. Such a configuration may result in an increase in size and cost of the switch module 241.

As an example, in the vehicle power supply system 1 of this embodiment, when a rising edge PO of power consumption of the important emergency load 22 occurs, the first switch SW1 is switched on even during execution of the normality determination process, thereby preventing a large current from flowing only through the third switch SW3. This makes it possible to realize the vehicle power supply system 1 without giving the third switch SW3 a large current capacity. This operation example will be described with reference to Figures 8 and 9.

Figure 8 is a timing chart showing another example of the process in which the vehicle power supply system 1 transitions from the off state to the on state. (a) to (f) in Figure 8 and times T1 to T4 and T11 are the same as those in Figure 7.

The ECU 50 monitors the current I3 flowing through the third switch SW3 while the backup power supply system 20 is executing the normality determination process. For example, the ECU 50 can monitor the current I3 by acquiring the current value detected by the current detection unit 27 of the backup power supply control device 25 at a predetermined sampling period.

As described above, when a rise PO in the power consumption of the emergency important load 22 occurs at time T11 before the normality determination process is completed, the current value of the current I3 rises. This rise in the current I3 is called the peak current PC2.

Here, the ECU 50 switches the first switch SW1 on at time T12, using the value of the current I3 being equal to or greater than the threshold value TH as a trigger TG, and suspends the normality determination process. By turning on the first switch SW1, the current flowing through the third switch SW3, which is among the currents supplied to the important load 22 in an emergency through the switch module 241, is reduced. Furthermore, the ECU 50 switches off the third switch SW3. As a result, the current I3 flowing through the third switch SW3 becomes approximately 0 [A]. The timing at which the ECU 50 switches off the third switch SW3 may be the same as the timing at which the first switch SW1 is turned on, that is, at time T12. The ECU 50 may also switch off the third switch SW3 after time T12. The value of the threshold value TH is stored in advance in the ECU 50 or the backup power supply control device 25.

At time T12, the normality determination process is interrupted and the first switch SW1 is turned on, which eliminates the state in which the current flowing through the emergency important load 22 through the switch module 241 is concentrated on the third switch SW3, and the current value of the peak current PC2 can be suppressed. Therefore, even if the current capacity of the third switch SW3 is relatively small, the failure or damage of the third switch SW3 can be prevented. In addition, the time during which the peak current PC2 flows is short, for example, as shown by the time T11-T12 in FIG. 8. Therefore, even if the current value of the peak current PC2 exceeds the rated capacity of the third switch SW3, the heat generated by the third switch SW3 is within the range of the heat capacity of the third switch SW3. Therefore, the possibility of causing failure or damage to the third switch SW3 is extremely small. As a result, the current capacity of the third switch SW3 can be configured to be smaller than, for example, the rated consumption current of the emergency important load 22. In addition, the current capacity of the third switch SW3 can be configured to be smaller than the current capacity of the first switch SW1.

Figure 9 is a flowchart showing the operation of the vehicle power supply system 1, and is an example of an operation that realizes the operation shown in Figure 8. Steps S61-S67 in Figure 9 may be executed by either the ECU 50 or the backup power supply control device 25. In this embodiment, an example in which the ECU 50 executes the operation of Figure 3 will be described.

The operation in FIG. 9 is started when the normality determination process is started in step S13 (FIG. 3) or when the ECU 50 receives an operation of the SSSW 56. Therefore, the operation in FIG. 9 is executed in parallel with the operation shown in FIG. 3.

The ECU 50 starts monitoring the current I3 flowing through the third switch SW3 (step S61). The current I3 is monitored, for example, by the ECU 50 acquiring the current value detected by the backup power supply control device 25 using the current detection unit 27 at predetermined time intervals. The ECU 50 compares the current value of the current I3 with a threshold value TH to determine whether the current value of the current I3 is equal to or greater than the threshold value TH (step S62).

If it is determined that the current value of current I3 is not equal to or greater than threshold value TH, i.e., that the current value of current I3 is smaller than threshold value TH (step S62; NO), ECU 50 determines whether or not the normality determination process has ended (step S63). If the normality determination process is being executed (step S63; NO), ECU 50 executes step S62 at a predetermined interval. If the normality determination process has ended (step S63; YES), ECU 50 ends this process.

If it is determined that the current value of the current I3 is equal to or greater than the threshold value TH (step S62; YES), the ECU 50 suspends the normality determination process (step S64) and switches the first switch SW1 on (step S65). After suspending the normality determination process in step S64, the ECU 50 does not execute steps S14 and onward in the operation of FIG. 3.

In steps S64 and S65, the ECU 50 controls the backup power supply control device 25 to interrupt the normality determination process and to switch the first switch SW1. The controls in steps S64 and S65 may be performed simultaneously or in parallel, or step S65 may be performed before step S64.

The ECU 50 further controls the backup power supply control device 25 to switch the third switch SW3 off (step S66). The switching of the third switch SW3 may be performed simultaneously or in parallel with the interruption of the normality determination process in step S64 and the switching of the first switch SW1 in step S65. It is preferable that the switching of the third switch SW3 in step S66 is performed simultaneously with or after the switching of the first switch SW1 in step S65. By switching the third switch SW3 off after the first switch SW1 is switched on, the power supply from the main low-voltage power supply 11 or the high-voltage power supply unit 36 to the emergency important load 22 is not interrupted, which has the advantage of not interfering with the operation of the emergency important load 22.

The ECU 50 may also control the backup power supply control device 25 to switch the second switch SW2 on and then switch the third switch SW3 off. Specifically, the ECU 50 switches the second switch SW2 on in parallel with or after the control to interrupt the normality determination process in step S64. As a result, the second switch SW2 is switched on before the timing at which the third switch SW3 is switched off. In this case, power can be supplied from the backup low-voltage power supply 23 to the emergency important load 22. Therefore, even if a state occurs in which both the third switch SW3 and the first switch SW1 are switched off, it is possible to avoid interruption of the power supply to the emergency important load 22, and the emergency important load 22 can continue to operate.

After steps S65-S66, the ECU 50 starts the emergency important load 22 and the normal load 12 (step S67). After the power consumption of the emergency important load 22 starts up, a part of the emergency important load 22 is already running, but in step S67, the ECU 50 transitions the entire emergency important load 22 and the normal load 12 to an operable state, similar to step S16 (FIG. 3). This transitions the vehicle power supply system 1 to an ON state.

In this way, when the current value of the current I3 flowing through the third switch SW3 becomes equal to or greater than the threshold value TH, the ECU 50 interrupts the normality determination process and switches on the first switch SW1. This makes it possible to avoid failure or damage to the third switch SW3 even if the emergency important load 22 starts up before the normality determination process ends and a current I3 exceeding the rated capacity flows through the third switch SW3. Therefore, since the current capacity of the third switch SW3 can be made smaller than that of the first switch SW1, for example, the third switch SW3 and the switch module 241 can be made smaller and less expensive.

3. Other embodiments
The above embodiment shows a specific example to which the present invention is applied, and does not limit the form to which the invention is applied.

4 and 5 are merely examples, and any process may be used to determine whether the backup power supply system 20 operates normally. For example, in the normality determination process, the ECU 50 may supply power from the main power supply system 10. Specifically, the ECU 50 turns off the first switch SW1 and the third switch SW3, and causes the step-down device 40 to output a voltage higher than the output voltage of the second switch SW2. In this case, if the difference in voltage across the first switch SW1 is equal to or less than a predetermined value, it can be determined that the first switch SW1 and/or the third switch SW3 are stuck on.

In addition, the timing charts shown in Figures 6 to 8 are merely examples of operation, and the operation of the vehicle power supply system 1 can be modified as appropriate.

4. Configurations supported by the above embodiment
The above embodiment supports the following configurations.

(Configuration 1) A vehicle power supply system comprising: a main power supply system having a main low-voltage power supply and a normal load; and a backup power supply system having a backup low-voltage power supply and an emergency important load and connected to the main power supply system, the backup power supply system being capable of supplying power from the backup low-voltage power supply to the main power supply system, the backup power supply system having a main switch capable of switching between connection and disconnection with the main power supply system, and a backup power supply control device for controlling the main switch, the main switch being disconnected when not controlled, a sub switch being arranged in parallel with the main switch between the main power supply system and the backup power supply system and being connected when the main switch is not controlled, and a sub switch being connected to at least one of the normal load and the emergency important load, and a vehicle control device capable of controlling the main power supply system and the backup power supply system, wherein when an operation is performed to start up at least one of the normal load and the emergency important load, the vehicle control device starts up the backup power supply control device based on the operation, executes a normality determination process to determine whether or not the backup power supply system is normal, and if a current flowing through the secondary switch during execution of the normality determination process is equal to or greater than a threshold value, closes the main switch and cuts off the secondary switch, and if a current flowing through the secondary switch during execution of the normality determination process is smaller than the threshold value, closes the main switch and cuts off the secondary switch after completion of the normality determination process.
According to configuration 1, the vehicle power supply system that enables power supply from the main power supply system and the backup power supply system to important loads in an emergency is operated so that a large current does not continuously flow to the secondary switch. This makes it possible to reduce the current capacity required for the secondary switch. This makes it possible to reduce the size and cost of the secondary switch, which in turn makes it possible to reduce the size and cost of the backup power supply system.

(Configuration 2) The vehicle power supply system according to configuration 1, wherein a current capacity of the sub switch is smaller than a current capacity of the main switch.
According to configuration 2, by using a switch having a smaller current capacity than the main switch as the secondary switch, it is possible to realize a reduction in size and cost of the backup power supply system.

(Configuration 3) The vehicle power supply system according to Configuration 1 or 2, wherein, when the vehicle control device determines that the backup power supply system is normal in the normality determination process, the vehicle control device closes the main switch and then shuts off the secondary switch.
According to configuration 3, the secondary switch is turned off after the backup low-voltage power supply and the main power supply system are connected by the main switch. As a result, the secondary switch is turned off after it becomes possible to supply power from the main power supply system via the main switch to the important load in an emergency of the backup power supply system. Therefore, a state in which power can be supplied from the main power supply system to the important load in an emergency can be maintained while the main switch and the secondary switch are being disconnected. Therefore, the power supply to the important load in an emergency can be secured, and the important load in an emergency can be operated stably.

(Configuration 4) A vehicle power supply system according to any one of Configurations 1 to 3, wherein when the vehicle control device determines that the backup power supply system is normal in the normality determination process, the vehicle control device executes an operation of controlling the main switch to connect and an operation of controlling the sub switch to cut off, thereby enabling power supply from the main power supply system to the emergency important load, and then starts up the emergency important load.
According to configuration 4, power can be supplied from the main power supply system to the important load in an emergency via the main switch, and the important load in an emergency is started after the secondary switch is shut off. This reliably prevents a large current from flowing through the secondary switch, thereby enabling the secondary switch to be made smaller and less expensive.

(Configuration 5) The vehicle power supply system according to any one of configurations 1 to 4, wherein the normality determination process includes a process for determining whether the main switch operates normally.
According to configuration 5, it is possible to prevent a state in which a large current flows through the sub switch due to a malfunction of the main switch, thereby making it possible to reduce the size and cost of the sub switch.

(Configuration 6) The vehicle power supply system according to any one of configurations 1 to 5, wherein the backup power supply system includes a backup power supply switch that switches between on and off the power supply from the backup low-voltage power supply in accordance with control of the backup power supply control device, and the normality determination process includes determining that the backup power supply switch is operating normally.
According to configuration 6, when it is determined that the backup power supply switch operates normally, the emergency important load is started. Therefore, the emergency important load is started after it is determined that the backup low-voltage power supply can supply power to the emergency important load. Therefore, the power supply to the emergency important load can be reliably secured.

1...vehicle power supply system, 10...power supply system, 11...main low voltage power supply, 12...normal load, 20...backup power supply system, 21...backup power supply unit, 22...important load in emergency, 23...backup low voltage power supply, 24...switching device, 25...backup power supply control device, 27, 27a, 27b, 27c...current detection unit, 30...high voltage power supply system, 31...high voltage power supply, 32...high voltage load, 40...step-down device, 50...ECU (vehicle control device), 55...operation unit, 56...SSSW, 241...switch module, 321...drive unit, 322...air conditioner, CP...capacitor, MG...rotating electric machine, PCU...power control unit, SW1...first switch (main switch), SW2...second switch (backup power supply switch), SW3...third switch (secondary switch), V...vehicle.

Claims (6)

a main power system having a main low voltage power source and a normal load;
a backup power supply system having a backup low-voltage power supply and an important load in an emergency and connected to the main power supply system;
The backup power supply system is capable of supplying power from the backup low-voltage power supply to the main power supply system, and the backup power supply system has a main switch that can switch between connection and disconnection with the main power supply system, and a backup power supply control device that controls the main switch,
The main switch is disconnected when not controlled,
a secondary switch that is arranged in parallel with the main switch between the main power supply system and the backup power supply system and that is connected when the main switch is not being controlled;
a vehicle control device capable of controlling at least one of the normal load and the emergency important load, the main power supply system, and the backup power supply system;
The vehicle control device includes:
When an operation for starting at least one of the normal load and the emergency important load is performed, the backup power supply control device is started based on the operation, and a normality determination process is executed to determine whether or not the backup power supply system is normal;
When the current flowing through the secondary switch during execution of the normality determination process is equal to or greater than a threshold value, the main switch is turned on and the secondary switch is turned off;
When the current flowing through the secondary switch during execution of the normality determination process is smaller than the threshold value, the main switch is connected and the secondary switch is disconnected after the normality determination process is completed. The vehicle power supply system of claim 1, wherein the current capacity of the secondary switch is smaller than the current capacity of the primary switch. The vehicle power supply system according to claim 2, wherein the vehicle control device, when determining that the backup power supply system is normal in the normality determination process, turns off the secondary switch after the main switch is connected. The vehicle power supply system according to claim 3, wherein, when the vehicle control device determines that the backup power supply system is normal in the normality determination process, the vehicle control device executes an operation of controlling the main switch to connect and an operation of controlling the sub switch to disconnect, thereby enabling power supply from the main power supply system to the emergency important load, and then starts up the emergency important load. The vehicle power supply system according to any one of claims 1 to 4, wherein the normality determination process includes a process for determining that the main switch operates normally. the backup power supply system includes a backup power supply switch that switches between on and off the supply of power from the backup low-voltage power supply in accordance with control of the backup power supply control device;
The vehicle power supply system according to claim 5 , wherein the normality determination process includes determining whether the backup power switch operates normally.

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