In-vehicle power supply system

Abstract

The in-vehicle power supply system supplies power to a large-power load and a small-power load. The in-vehicle power supply system includes: a first power supply unit for outputting power having a first voltage that is higher than the total power supply voltage required by the large-power load and the small-power load; a zone management unit for managing a predetermined zone on the vehicle; a power main line unit that connects the first power supply unit to the zone management unit; and a step-down conversion unit that is provided in a zone of one of the zone management units and converts the power having the first voltage into power having a second voltage that is lower than the first voltage. The power main line unit includes a high-voltage power line to distribute the power having the first voltage.

Description

Technical Field

[0001] The subject matter of the present disclosure relates to a vehicle power supply system. Background Art

[0002] In the prior art, in the auxiliary system of an ordinary vehicle, power is supplied to various electrical components via a wiring harness laid in each part of the vehicle, and the power source includes an alternator (generator) and a vehicle-mounted battery capable of supplying power with a voltage of 12 volts.

[0003] In addition, for example, the power supply redundancy system in the prior art includes multiple power sources that handle two types of voltages, 12 volts and 48 volts. Further, since a DC / DC converter provided in the power source can be used to convert the power supply voltage, power can be supplied to the load even when a ground fault or short circuit occurs in one power supply system (for example, see Patent Document JP2019-193517A).

[0004] A large number of various types of electrical components are provided in the auxiliary system on the vehicle. Among these electrical components, large power loads that consume a very large amount of current and small power loads that consume a small amount of current are mixed. Examples of large power loads on the vehicle include an electric stabilizer device and an electric power steering device.

[0005] The power supply voltage required for small power loads is usually 12 volts, but the power supply voltage required for large power loads is usually higher than 12 volts. Therefore, in an ordinary vehicle having only a 12-volt power source, the required power supply voltage such as 48 volts is obtained by raising the 12-volt power supply voltage using a DC / DC converter installed on each device having a large power load. In addition, in order to avoid an increase in power loss caused by the influence of a large current flowing through each large power load, wires having a large cross-sectional area are used for the power supply wires of the wiring harness. Therefore, the power supply required for large power loads is a factor that increases the cost of the entire vehicle.

[0006] On the other hand, in the case where a vehicle in the prior art has two types of power supply systems, a voltage corresponding to the power supply voltage required for each electrical component can be supplied from a predetermined power supply system in a stable state. That is, power can be supplied from a 12-volt vehicle-mounted battery to electrical components that require a 12-volt power supply voltage, and power can be supplied from a 48-volt vehicle-mounted battery to electrical components that require a 48-volt power supply voltage.

[0007] However, in the system disclosed in the prior art, since it is necessary to install power supply units such as vehicle-mounted batteries for 12 volts and 48 volts respectively for the auxiliary system, the cost of the entire vehicle increases significantly.

[0008] In addition, there is a large power load that consumes a very large amount of power among electrical components that require a power supply voltage of 12 volts. To prevent a large power loss from occurring when power is supplied to such a large power load, a power supply line of a wire harness needs to be formed using thick wires. In addition, since there is a possibility that a large voltage fluctuation occurs in the power supply voltage due to the influence of a large current flowing through the large power load, it is necessary to provide a margin for the power supply voltage fluctuation to the load side circuit of the 12V system, which results in an increase in power loss. Summary of the Invention

[0009] The subject matter of the present disclosure provides a vehicle-mounted power supply system that can prevent an increase in the cost of the entire vehicle, reduce the diameter of the power supply line in the wire harness, and reduce power loss.

[0010] According to an exemplary aspect of the currently disclosed subject matter, a vehicle-mounted power supply system is configured to supply power to a large power load and a small power load, the large power load being configured to consume a first power, and the small power load being configured to consume a second power less than the first power. The vehicle-mounted power supply system includes: a first power supply unit configured to output power having a first voltage that is higher than the total power supply voltage required by the large power load and the small power load; a plurality of area management units configured to respectively manage predetermined areas on the vehicle; a power main line unit that connects the first power supply unit to the plurality of area management units; and a step-down conversion unit provided in an area of one of the plurality of area management units and configured to convert the power having the first voltage into power having a second voltage lower than the first voltage. The power main line unit includes a high-voltage power supply line configured to distribute the power having the first voltage.

[0011] Other aspects and advantages of the currently disclosed subject matter will be apparent from the following description, drawings, and claims. Brief Description of the Drawings

[0012] Figure 1 is a block diagram showing a basic configuration of a vehicle-mounted power supply system according to an embodiment of the subject matter of the present disclosure;

[0013] Figure 2 is a block diagram showing a specific configuration example of a vehicle-mounted power supply system according to an embodiment of the present disclosure; and

[0014] Figure 3A and Figure 3B are block diagrams respectively showing configuration examples of the vehicle-mounted power supply system. Detailed Description of the Embodiment

[0015] Hereinafter, specific embodiments according to the present disclosure will be described with reference to the accompanying drawings.

[0016] Figure 1 is a block diagram showing a basic configuration of an in-vehicle power supply system 10 according to an embodiment of the present disclosure.

[0017] The in-vehicle power supply system 10 is installed in, for example, a hybrid vehicle, an electric vehicle, or an ordinary vehicle that uses only an engine as a drive source, and can be used to supply power to various electrical components of an auxiliary system on the vehicle.

[0018] Figure 1 The in-vehicle power supply system 10 in includes: a power main line 11, a DC / DC converter 12, an auxiliary system battery 13, a large power load 14, a regional electronic control unit (ECU) 15, a DC / DC converter 16, a power branch line 17, a small power load 18, and a ground line 19. The above-described components of the in-vehicle power supply system 10 are generally installed on the vehicle as an integrated state as a single wiring harness.

[0019] The input side of the DC / DC converter 12 is connected to the drive system high-voltage power line 12a. The drive system high-voltage power line 12a can output electric power with a DC high voltage of about several hundred volts in order to supply large power to the motor that drives the vehicle. In the case of an ordinary vehicle without the drive system high-voltage power line 12a, an alternator (ALT) instead of the DC / DC converter 12 is connected to the in-vehicle power supply system 10.

[0020] The DC / DC converter 12 reduces the voltage (several hundred volts) of the drive system high-voltage power line 12a by performing switching inside the DC / DC converter 12 to generate 48-volt DC power. Then, the 48-volt DC power output from the DC / DC converter 12 or the alternator is supplied to the power main line 11.

[0021] The auxiliary system battery 13 is a secondary battery that can supply power to various electrical components in an auxiliary system that does not belong to the vehicle drive system, and in Figure 1 In the example shown, it can charge and discharge DC power with a voltage of 48 volts. That is, the auxiliary system battery 13 can charge and accumulate the 48-volt DC power output from the DC / DC converter 12, and can discharge and supply the accumulated 48-volt DC power to the power main line 11. In fact, when a part of the large power consumed by the large power load 14 is temporarily taken out even when the vehicle is running or when the vehicle is parked, etc., the power accumulated in the auxiliary system battery 13 is used to supply power to various electrical components of the auxiliary system.

[0022] The large power load 14 is an electrical component that consumes a very large amount of power among various electrical components belonging to the auxiliary system. For example, when the electric stabilizer device and the electric power steering device are operating, the electric stabilizer device and the electric power steering device installed on a vehicle consume a very large amount of power and are thus regarded as the large power load 14.

[0023] In the case of an ordinary vehicle, even among large power loads, power with a voltage of 12 volts is usually supplied via a standard power line, and a large current flows through the large power load. Therefore, it is necessary to make the power line for supplying power to the large power load very thick.

[0024] On the other hand, in Figure 1 In the in-vehicle power supply system 10 shown, since power with a voltage of 48 volts is supplied from the power main line 11 to the large power load 14, the current flowing through the large power load 14 can be significantly reduced. Therefore, the diameter of the power line of the power main line 11 can be reduced. In addition, the large power load 14 does not need to include a booster circuit therein.

[0025] On the other hand, the small power load 18 corresponds to an electrical component with relatively low power consumption among various electrical components belonging to the auxiliary system. For example, electrical components such as various ECUs, various lighting devices, audio devices, and navigation devices are regarded as the small power load 18.

[0026] In Figure 1 In the configuration shown, the small power load 18 is connected to the power branch line 17 with a voltage of 12 volts for use. The power branch line 17 is connected to the downstream side of the area ECU 15.

[0027] The area ECU 15 is a device for managing the power supply to loads in a specific area on the vehicle and includes a DC / DC converter 16. The area managed by the area ECU 15 can represent a specific area in the space on the vehicle or can represent a specific group in the functional grouping. Therefore, multiple independent area ECUs 15 are usually installed on the vehicle.

[0028] As Figure 1 shown, since the area ECU 15 is connected to the power main line 11, the area ECU 15 can supply power with a voltage of 48 volts to the DC / DC converter 16 in the area ECU 15 as an input. The DC / DC converter 16 has the following function: based on the DC power with a voltage of 48 volts applied to the DC / DC converter 16 as an input to the DC / DC converter 16, it generates DC power with a voltage of 12 volts. Therefore, the area ECU 15 can supply DC power with a voltage of 12 volts to the power branch line 17 connected to the downstream side of the area ECU 15.

[0029] The regional ECU 15 is also capable of directly supplying downstream the power distributed from the DC power with a voltage of 48 V supplied as an input from the power main line 11. Although not shown in Figure 1 , the regional ECU 15 includes a control computer and a communication interface as in a general ECU.

[0030] Figure 2 is a block diagram showing a specific configuration example of the in-vehicle power supply system 10A according to an embodiment of the subject matter of the present disclosure. Figure 2 shows an outline of an arrangement example of main constituent components in a state of observing the vehicle from above.

[0031] Figure 2 The vehicle body 50 shown in includes an engine compartment 50a, a cabin instrument panel area 50b, and a trunk room 50c. In the engine compartment 50a, various electrical components in the auxiliary system are provided, such as a water pump 31, an oil pump 32, a cooling fan 33, an air conditioner (A / C) compressor 34, a brake actuator (ACT) 35, a catalyst heater 37, a defroster 38, an electric stabilizer 39, an electric power steering (EPS) actuator 40, and an air conditioner blower 41.

[0032] In addition, as an example, various electrical components in the auxiliary system, such as a positive temperature coefficient (PTC) heater 42, a seat heater 43, and an electric seat 44, are provided in the cabin. In addition, as an example, various electrical components in the auxiliary system, such as an electric power assisted braking (EPB) actuator 45, an electric stabilizer 46, and a defogger 47, are provided inside the trunk room 50c.

[0033] The in-vehicle power supply system 10A includes a regional ECU 15A in the engine compartment 50a for managing the area allocated to the engine compartment 50a. In addition, the in-vehicle power supply system 10A includes regional ECUs 15B and 15D for respectively managing the left and right regions of the cabin instrument panel area 50b at the left and right parts of the cabin instrument panel area 50b. The in-vehicle power supply system 10A includes a regional ECU 15C in the trunk room 50c for managing the area allocated to the trunk room 50c.

[0034] The regional ECUs 15A and 15B are connected to each other through a power main line 11C, the regional ECUs 15B and 15C are connected to each other through a power main line 11D, and the regional ECUs 15B and 15D are connected to each other through a power main line 11E.

[0035] The DC / DC converter 12 and the auxiliary system battery 13 are respectively connected to the regional ECU 15A via the power supply mains 11A and 11B. The input side of the DC / DC converter 12 is connected to the output side of the high-voltage battery 21. The high-voltage battery 21 is formed of a secondary battery such as a lithium-ion battery, capable of storing electric power with a high voltage of, for example, about several hundred volts, and capable of supplying the stored electric power to an electric motor for vehicle running and the like.

[0036] The DC / DC converter 12 converts the electric power of the direct-current high voltage with about several hundred volts output from the high-voltage battery 21 into direct-current electric power with a voltage of 48 volts, and supplies the direct-current electric power to the power supply main 11A. The auxiliary system battery 13 is charged with the direct-current electric power with a voltage of 48 volts supplied from the DC / DC converter 12, and is capable of outputting the direct-current electric power with a voltage of 48 volts accumulated by charging to the power supply main 11B.

[0037] The power supply mains 11A, 11B, 11C are electrically connected to each other inside the regional ECU 15A. The power supply mains 11C and 11D are electrically connected to each other inside the regional ECU 15B. Therefore, the direct-current electric power with a voltage of 48 volts output from the DC / DC converter 12 or the auxiliary system battery 13 is supplied to the power supply mains 11C, 11D. Each of the power supply mains 11C, 11D includes a power supply line for distributing the direct-current electric power with at least a voltage of 48 volts.

[0038] The regional ECUs 15A, 15B, 15C respectively include DC / DC converters 16. Since there is no load consuming a large amount of electric power in the area managed by the regional ECU 15D, the regional ECU 15D does not include a DC / DC converter 16. The power supply main 11E connecting the regional ECUs 15B, 15D includes a power supply line for distributing the direct-current electric power with a voltage of 12 volts.

[0039] As Figure 2 shown, the power supply branch line 17A connected to the downstream side of the regional ECU 15A includes a 48V power supply line 22 and a 12V power supply line 23. The 48V power supply line 22 is a power supply line for outputting the electric power (48 volts) obtained by distributing or branching the direct-current electric power with a voltage of 48 volts supplied from the power supply main 11A or 11B, and the 12V power supply line 23 is a power supply line for outputting the electric power (12 volts) output from the DC / DC converter 16 in the regional ECU 15A. The DC / DC converter 16 generates 12-volt electric power by performing a step-down conversion on the 48-volt electric power.

[0040] In Figure 2In the illustrated example, a water pump 31, an oil pump 32, a cooling fan 33, an air-conditioning compressor 34, a brake actuator 35, a catalyst heater 37, a de-icer 38, an electric stabilizer 39, an EPS actuator 40, and an air-conditioning blower 41 are connected to a 48V power line 22.

[0041] In particular, since the electric stabilizer 39 and the EPS actuator 40 consume a very large amount of power, it is effective to reduce the diameter of wires such as the 48V power line 22 and the main line when the electric stabilizer 39 and the EPS actuator 40 are connected to the 48V power line 22 supplied with 48 volts. Various small power loads that require a 12V power supply voltage are connected to a 12V power line 23.

[0042] On the other hand, a PTC heater 42, a seat heater 43, and an electric seat 44 installed in the passenger compartment are connected to the downstream side of the area ECU 15B via a power supply branch line 17B. The power supply branch line 17B includes a power line that distributes 48 volts of power, and the 48 volts of power distributed by the power line is obtained by distributing or branching the 48 volts of power supplied to the power supply main line 11C in the area ECU 15B.

[0043] 12 volts of power generated by the DC / DC converter 16 in the area ECU 15B performing step-down conversion on 48 volts of power is supplied to a 12V power line included in the power supply main line 11E. The power supply branch line 17D connected to the downstream side of the area ECU 15D is supplied with 12 volts of power obtained by distributing or branching the power of the 12V power line of the power supply main line 11E.

[0044] Meanwhile, the power supply branch line 17C of the area ECU 15C installed in the trunk room 50c includes a 48V power line 24 and a 12V power line 25. The 48V power line 24 can output 48 volts of power obtained by distributing or branching the 48 volts of power supplied from the power supply main line 11D in the area ECU 15C. The 12V power line 25 can output 12 volts of power obtained by the DC / DC converter 16 in the area ECU 15C performing step-down conversion on the 48 volts of power supplied from the power supply main line 11D.

[0045] An EPB actuator 45, an electric stabilizer 46, and a defroster 47 installed in the trunk room 50c are connected to the 48V power line 24. In particular, since the electric stabilizer 46 consumes a very large amount of power, it is effective to reduce the diameter of wires such as the 48V power line 24 and the main line when the electric stabilizer 46 is connected to the 48V power line 24 supplied with 48 volts. Various small power loads that require a 12V power supply voltage can be connected to the 12V power line 25.

[0046] In Figure 2In the in-vehicle power supply system 10A, since the right region of the instrument panel in the vehicle compartment managed by the regional ECU 15D has fewer large power loads, the following regional ECU 15D is installed: It includes a 12-volt power line in the power main line 11E and does not include a DC / DC converter 16. It is desired that the power main line 11E also includes a 48-volt power line so that large power loads can also be connected to the downstream side of the regional ECU 15D.

[0047] Figure 3A and Figure 3B are block diagrams each showing a configuration example of an in-vehicle power supply system. Figure 3A The in-vehicle power supply system 60 shown in is configured to supply 12-volt power to the power main line 66 as in the case of a normal vehicle. In the in-vehicle power supply system 60, the large power load 63 includes a DC / DC converter 64, and the DC / DC converter 64 boosts 12-volt power to 48-volt power therein and then supplies the power to the load side.

[0048] Figure 3B The in-vehicle power supply system 70 shown in is configured to supply 48-volt power to the power main line 76, similar to the in-vehicle power supply systems 10 and 10A of the above embodiments. In addition, the in-vehicle power supply system 70 is configured to step down the power of the power main line 76 from 48 volts to 12 volts through the DC / DC converter 74 and then supply the stepped-down power to the small power load 75, and supply the 48-volt power of the power main line 76 as it is to the large power load 73.

[0049] By comparing Figure 3A the in-vehicle power supply system 60 in and Figure 3B the in-vehicle power supply system 70 in, when the power consumption of the large power loads 63 and 73 is the same, the ratio of the magnitudes of the load currents i60 and i70 flowing from the power main lines 66 and 76 to the large power loads 63 and 73 is approximately 1:4.

[0050] Therefore, in the case of the in-vehicle power supply system 60, the power main line 66 needs to be formed of thick wires. In addition, since it is expected that the voltage fluctuations generated in the power main line 66 become larger due to the large power load 63, the margin of the actually supplied power voltage needs to be increased with respect to the stable power supply voltage required for the small power load 65, and the power loss generated inside the small power load 65 side increases. That is, since the 12-volt voltage supplied from the power main line 66 is unstable, for example, a converter that reduces 12 volts to generate a stable power supply voltage of 9 volts needs to be provided on the small power load 65 side, and power loss occurs due to this converter. In addition, when another small power load 65 or the like is added, the voltage drop of the power main line 66 increases significantly due to the current consumed by the added load. Therefore, since the margin of the load that can be added is small, it is necessary to determine the system specifications to limit the load to be added.

[0051] In the case of the in-vehicle power supply system 70, since the load current i70 is small, the diameter of the wire of the power main line 76 can be reduced. In addition, since the voltage fluctuations generated in the power main line 76 are small, when supplying the stable power supply voltage required for the small power load 75 as an output from the DC / DC converter 74, the margin of the voltage can be reduced, and the power loss generated on the small power load 75 side can be reduced. In addition, when a new small power load 75 is to be added, there is almost no limit to the small power load 75 to be added.

[0052] In addition, when the conversion efficiency in the DC / DC converter 64 of the in-vehicle power supply system 60 is the same as the conversion efficiency in the DC / DC converter 74 of the in-vehicle power supply system 70, comparing the power losses occurring inside the two, the DC / DC converter 74 has a smaller power loss than the DC / DC converter 64. That is, since the input current of the DC / DC converter 74 is smaller than the input current of the DC / DC converter 64, the power loss is reduced.

[0053] That is, as in the in-vehicle power supply system 10 in Figure 1 and the in-vehicle power supply system 10A in Figure 2 the power supply voltage of the power main lines 11, 11C, 11D, etc. is increased to 48 volts, and the power supply voltage is stepped down by the DC / DC converters 16 in the area ECUs 15, 15A, 15B, 15C to generate 12-volt power, so that the diameter of the power supply lines of the power main lines 11, 11C, 11D, etc. can be reduced as described above. In addition, terminals, connectors, housings, etc. at the positions where the power supply lines are connected can be miniaturized. As a result, the costs of all the area ECUs 15 and the entire wiring harness can be reduced.

[0054] Although the DC / DC converter 16 in each area can be connected to the outside of the area ECU 15, the configuration of the wiring harness can be simplified by incorporating the DC / DC converter 16 into the area ECU 15.

[0055] Although the present disclosure has been described with reference to certain exemplary embodiments of the present disclosure, the scope of the present disclosure is not limited to the above exemplary embodiments, and those skilled in the art will understand that various changes and modifications can be made therein without departing from the scope of the present disclosure defined by the appended claims.

[0056] According to one aspect of the above embodiment, the in-vehicle power supply system (10, 10A) is configured to supply power to a large power load (14) and a small power load (18), the large power load (14) being configured to consume a first power, and the small power load (18) being configured to consume a second power less than the first power. The in-vehicle power supply system includes: a first power supply unit (e.g., the DC / DC converter 12), which is configured to output power having a first voltage (e.g., 48 volts), the first voltage being higher than the total power supply voltage required by the large power load and the small power load; a plurality of area management units (e.g., area ECUs 15, 15A, 15B, 15C), which are configured to respectively manage predetermined areas on the vehicle; a power supply main line unit (e.g., power supply main lines 11, 1A to 11E), which connects the first power supply unit to the plurality of area management units; and a step-down conversion unit (e.g., the DC / DC converter 16), which is provided in the area of one of the plurality of area management units and is configured to convert the power having the first voltage into power having a second voltage (e.g., 12 volts) lower than the first voltage. The power supply main line unit includes high-voltage power lines (e.g., power supply main lines 11C, 11D), which are configured to distribute the power having the first voltage.

[0057] According to the in-vehicle power supply system having the above configuration, since the power supply main line unit distributes the power having the first voltage as a relatively high voltage, the current flowing through the wiring harness can be reduced at the portion connecting the first power supply unit and the plurality of area management units. Therefore, the diameter of the high-voltage power line can be reduced. In addition, by using the step-down conversion unit, a power supply voltage having the second voltage required by the small power load or the like can be generated. In addition, since the first voltage can be directly supplied to the large power load, there is no need to increase the power supply voltage, and an increase in power loss is prevented. Since the input current of the step-down conversion unit is relatively small, the power loss of the step-down conversion unit for stepping down the power supply voltage is smaller than that in the case of stepping up the power supply voltage.

[0058] The step-down conversion unit (DC / DC converter 16) can be built into one of the plurality of area management units (area ECUs 15, 15A, 15B, 15C).

[0059] With this configuration, since there is no need to connect the power supply line required for using the step-down conversion unit to the outside of the area management unit, the configuration of the wiring harness can be simplified.

[0060] A part of the power supply main line unit may include a low-voltage power supply line (for example, power supply main line 11E), which is configured to distribute power having a second voltage.

[0061] With this configuration, since the power having the second voltage can be directly obtained from the power supply main line unit at the position including the low-voltage power supply line, the power having the second voltage can also be used for small power loads in areas where there is no step-down conversion unit. Therefore, it is not necessary to provide a step-down conversion unit in all of the plurality of area management units, and the configuration of the entire system can be simplified.

[0062] Each of the plurality of area management units can be configured to supply power having a first voltage to a large power load in the managed area and supply power having a second voltage to a small power load in the managed area.

[0063] With this configuration, since the power having the second voltage output from the step-down conversion unit is only consumed by the small power loads in the corresponding area, the step-down conversion unit can be miniaturized. In addition, the current flowing to the large power loads in the corresponding area can be reduced.

[0064] The in-vehicle power supply system may also include a second step-down conversion unit (DC / DC converter 12) on the input side of the first power supply unit, which is configured to step down the vehicle drive system high voltage (for example, several hundred volts) higher than the first voltage to power having the first voltage.

[0065] With this configuration, in the case of a vehicle equipped with a high-voltage power supply of approximately several hundred volts for driving the vehicle, such as a hybrid vehicle or an electric vehicle, the power from the high-voltage power supply can be supplied to the first power supply unit as an input via the second step-down conversion unit.

Claims

1. A vehicle power supply system configured to supply power to a large power load and a small power load, the large power load being configured to consume a first power, the small power load being configured to consume a second power, the second power consumed by the small power load being less than the first power consumed by the large power load, the vehicle power supply system comprising: A first power supply unit configured to output power having a first voltage, the first voltage being higher than the total power supply voltage required by the large power load and the small power load; A plurality of area management units configured to respectively manage predetermined areas on the vehicle; A power trunk unit connecting the first power supply unit and the plurality of area management units; And A first step-down conversion unit provided in an area of one of the plurality of area management units and configured to convert power having the first voltage into power having a second voltage lower than the first voltage, wherein the power trunk unit includes a high-voltage power line configured to distribute power having the first voltage, and wherein the first step-down conversion unit is built in one of the plurality of area management units.

2. The vehicle power supply system according to claim 1, wherein, A part of the power trunk unit includes a low-voltage power line configured to distribute power having the second voltage.

3. The vehicle power supply system according to claim 1 or 2, wherein, Each of the plurality of area management units is configured to supply power having the first voltage to the large power load in the management area and supply power having the second voltage to the small power load in the management area.

4. The vehicle power supply system according to claim 1 or 2, further comprising a second buck conversion unit on the input side of the first power supply unit, the second buck conversion unit being configured to step down the high vehicle drive system voltage higher than the first voltage to a power having the first voltage.

5. The vehicle power supply system according to claim 3, further comprising a second buck conversion unit on the input side of the first power supply unit, the second buck conversion unit being configured to step down the high vehicle drive system voltage higher than the first voltage to a power having the first voltage.

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