Vehicle-mounted power supply device

Abstract

This technology provides the ability to selectively supply power from a step-down converter to multiple loads while keeping the number of step-down converters to a minimum. [Solution] The in-vehicle power supply device 20 includes a step-down unit 22 and a plurality of diodes 17A, 17B. The step-down unit 22 has either a step-down function that steps down the voltage applied to the first conductive path 14 and applies it to the second conductive path 15, or a stop function that stops the output to the second conductive path 15, and either only the step-down function or both the step-down function and the stop function. Each diode 23A, 23B allows current to flow from the second conductive path 15 to the third conductive path 17A, 17B, and blocks current flow from the third conductive path 17A, 17B to the second conductive path 15. Furthermore, the in-vehicle power supply device 20 includes a voltage detection unit (for example, a first voltage detection unit 24) that detects the voltage of the second conductive path 15.

Description

Technical Field

[0001] This disclosure relates to an in-vehicle power supply device.

Background Art

[0002] Patent Document 1 discloses a failure detection device for a vehicle power supply device. In Patent Document 1, a step-down circuit steps down the output voltage of a capacitor to the operating voltage of a vehicle electrical load and outputs it. Also, a bypass relay is provided in parallel with the step-down circuit.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] According to the configuration of Patent Document 1, the output voltage stepped down by the step-down circuit and the output voltage via the bypass relay can be selectively output to a vehicle electrical load. When such a configuration in which the step-down circuit and the relay are provided in parallel is provided for each load, a step-down circuit is required for each load.

[0005] An object of this disclosure is to provide a technique capable of selectively supplying power from a step-down unit to a plurality of loads while suppressing an increase in the number of step-down units.

Means for Solving the Problems

[0006] The in-vehicle power supply device of this disclosure is An in-vehicle power supply device included in an in-vehicle system, comprising: a power supply unit; a common power path connected to the power supply unit; a plurality of branch paths branching from the common power path and connected to each load; a first conductive path branching from the common power path separately from the plurality of branch paths; a second conductive path provided between the first conductive path and the plurality of branch paths; and a plurality of individual switch units provided in each of the plurality of branch paths, A step-down section is provided between the first conductive path and the second conductive path, The branch path comprises a plurality of diodes individually provided between a third conductive path located on the load side of the individual switch section in each of the aforementioned branch paths and the second conductive path, The step-down unit has a step-down function that steps down the voltage applied to the first conductive path and applies it to the second conductive path, and a stop function that stops the output to the second conductive path, and either has only the step-down function, or has both the step-down function and the stop function. Each of the diodes allows current to flow from the second conductive path to the third conductive path, and blocks current flow from the third conductive path to the second conductive path. Furthermore, it includes a voltage detection unit for detecting the voltage of the second conductive path. [Effects of the Invention]

[0007] According to the technology disclosed herein, it is possible to selectively supply power from a step-down converter to multiple loads while suppressing an increase in the number of step-down converters. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic diagram showing the in-vehicle system of the first embodiment. [Figure 2] Figure 2 is a conceptual diagram illustrating the state in which power is supplied from the power supply unit to the load via a branch line in the first embodiment. [Figure 3] Figure 3 is a conceptual diagram illustrating the state in which power is supplied from the step-down unit to the load in the first embodiment. [Figure 4]Figure 4 is a conceptual diagram illustrating the current flow when some of the diodes short-circuit in the first embodiment. [Figure 5] Figure 5 is a flowchart showing the processing flow performed by the control unit of the first embodiment. [Figure 6] Figure 6 is a schematic diagram showing the in-vehicle system of the second embodiment. [Figure 7] Figure 7 is a flowchart showing the processing flow performed by the control unit of the second embodiment. [Modes for carrying out the invention]

[0009] [Description of Embodiments in this Disclosure] First, the embodiments of this disclosure will be listed and described.

[0010] [1] An in-vehicle power supply device included in an in-vehicle system comprising: a power supply unit; a common power line connected to the power supply unit; a plurality of branch lines branching from the common power line and connected to each load; a first conductive line branching from the common power line separately from the plurality of branch lines; a second conductive line provided between the first conductive line and the plurality of branch lines; and a plurality of individual switch units provided in each of the plurality of branch lines, A step-down section is provided between the first conductive path and the second conductive path, The branch path comprises a plurality of diodes individually provided between a third conductive path located on the load side of the individual switch section in each of the aforementioned branch paths and the second conductive path, The step-down unit has a step-down function that steps down the voltage applied to the first conductive path and applies it to the second conductive path, and a stop function that stops the output to the second conductive path, and either has only the step-down function, or has both the step-down function and the stop function. Each of the diodes allows current to flow from the second conductive path to the third conductive path, and blocks current flow from the third conductive path to the second conductive path. Furthermore, the vehicle power supply device includes a voltage detection unit for detecting the voltage of the second conductive path.

[0011] When each individual switch section is in the on state, the in-vehicle power supply device can supply the output voltage from the power supply section to each load without reducing the voltage by the voltage reduction section. Also, when each individual switch section is in the off state, the in-vehicle power supply device can reduce the output voltage from the power supply section by the voltage reduction section and supply it to each load via the second conductive path and each diode. That is, the in-vehicle power supply device can selectively supply the power from one voltage reduction section to a plurality of loads by switching the on / off state of each individual switch section.

[0012] Also, in the above configuration, there is a concern that when a diode fails, current may flow backward from the third conductive path side to the second conductive path side through the diode. For this reason, it is desirable to be able to detect this when a reverse flow occurs in the diode. When a reverse flow occurs in the diode, an abnormality should occur in the voltage of the second conductive path in a state where the voltage applied to the second conductive path by the voltage reduction section is reduced or in a state where the output to the second conductive path is stopped by the voltage reduction section. In this regard, since the in-vehicle power supply device includes a voltage detection section that detects the voltage of the second conductive path, it is possible to determine that a reverse flow has occurred in the diode based on the detection result of the voltage detection section.

[0013] 〔2〕The voltage reduction section has a configuration in which a resistance section and a switch section are connected in series, and includes a control section that controls the switch section, and the control section determines whether or not a reverse flow has occurred in the diode based on the detection result by the voltage detection section in a state where the switch section is controlled to be in the off state. The in-vehicle power supply device according to 〔1〕.

[0014] When the switch unit is in the off state, the voltage of the second conduction path should be lower than the voltage of the third conduction path when the individual switch unit is in the on state. On the other hand, when reverse current occurs due to the diode, even if the switch unit is in the off state, the voltage of the second conduction path becomes equal to the voltage of the third conduction path when the individual switch unit is in the on state. Utilizing this phenomenon, the in-vehicle power supply device can determine whether reverse current is occurring due to the diode based on the detection result by the voltage detection unit while controlling the switch unit to be in the off state.

[0015] 〔3〕The step-down unit has a voltage adjustment unit that performs a step-down operation of stepping down the voltage applied to the first conduction path so that the voltage applied to the second conduction path becomes the target voltage. The in-vehicle power supply device according to 〔1〕.

[0016] When the voltage adjustment unit is performing the step-down operation, the voltage of the second conduction path should be near the target voltage. On the other hand, when reverse current occurs due to the diode, even when the voltage adjustment unit is performing the step-down operation, the voltage of the second conduction path becomes equal to the voltage of the third conduction path when the individual switch unit is in the on state. Utilizing this phenomenon, the in-vehicle power supply device can determine whether reverse current is occurring due to the diode based on the detection result by the voltage detection unit while the voltage adjustment unit is performing the step-down operation.

[0017] 〔4〕It includes a control unit that controls the voltage adjustment unit. The control unit determines whether reverse current is occurring due to the diode based on the detection result by the voltage detection unit in a state where the voltage adjustment unit is performing the step-down operation. The in-vehicle power supply device according to 〔3〕.

[0018] The above in-vehicle power supply device can determine whether reverse current is occurring due to the diode without stopping the output from the step-down unit.

[0019] [Details of the Embodiment of the Present Disclosure] 1. First Embodiment 1-1. Configuration of In-Vehicle System 1 The in-vehicle system 1 shown in Figure 1 comprises a power supply unit 10, multiple loads 11A, 11B, a common power line 12, multiple branch lines 13A, 13B, a first conductive line 14, a second conductive line 15, a pull-down resistor 16, and an in-vehicle power supply device 20.

[0020] The power supply unit 10 is composed of, for example, a battery. The common power line 12 is electrically connected to the power supply unit 10 (for example, the positive terminal of the battery). The branch line 13A branches off from the common power line 12 and is connected to the load 11A. The branch line 13B branches off from the common power line 12 and is connected to the load 11B. In other words, each branch line 13A and 13B branches off from the common power line 12 and is connected to each load 11A and 11B.

[0021] The first conductive path 14 branches off from the common power path 12, separate from the branch paths 13A and 13B. The second conductive path 15 is located between the first conductive path 14 and the branch paths 13A and 13B. One end of the pull-down resistor 16 is electrically connected to the second conductive path 15. The other end of the pull-down resistor 16 is electrically connected to the ground 90. The second conductive path 15 is electrically connected to the ground 90 via the pull-down resistor 16.

[0022] The in-vehicle power supply device 20 is a device that distributes the power supplied from the power supply unit 10 to each load 11A, 11B. The in-vehicle power supply device 20 comprises a plurality of individual switch units 21A, 21B, a step-down unit 22, a plurality of diodes 23A, 23B, a first voltage detection unit 24, a second voltage detection unit 25, and a control unit 26.

[0023] Individual switch unit 21A is provided on branch line 13A. Individual switch unit 21B is provided on branch line 13B. In other words, each individual switch unit 21A, 21B is provided on each branch line 13A, 13B. Individual switch unit 21A allows power supply from power supply unit 10 to load 11A when it is ON, and cuts off power supply from power supply unit 10 to load 11A when it is OFF. Individual switch unit 21B allows power supply from power supply unit 10 to load 11B when it is ON, and cuts off power supply from power supply unit 10 to load 11B when it is OFF. In other words, each individual switch unit 21A, 21B allows power supply from power supply unit 10 to its corresponding loads 11A, 11B when it is ON, and cuts off power supply from power supply unit 10 to its corresponding loads 11A, 11B when it is OFF. Furthermore, each individual switch unit 21A, 21B, when in the off state, cuts off the power supply from the load 11A, 11B side to the power supply unit 10 side. The individual switch units 21A, 21B may be composed of mechanical switches with contacts, or they may be composed of semiconductor switching elements.

[0024] The step-down unit 22 is provided between the first conductive path 14 and the second conductive path 15. The step-down unit 22 has a resistor 22A and a switch 22B. The step-down unit 22 is configured by connecting the resistor 22A and the switch 22B in series between the first conductive path 14 and the second conductive path 15. The switch 22B may be a mechanical switch with contacts or a semiconductor switching element. When the switch 22B is ON, a voltage is applied to the second conductive path 15 that is a voltage drop from the voltage of the first conductive path 14 by the resistor 22A. In other words, the step-down unit 22 steps down the voltage applied to the first conductive path 14 and applies it to the second conductive path 15. When the switch 22B is OFF, the output of the step-down unit 22 to the second conductive path 15 stops. Therefore, the voltage of the second conductive path 15 becomes the voltage of ground 90. In this specification, voltage refers to the voltage relative to the potential of ground 90.

[0025] Diode 23A is installed between the third conductive path 17A and the second conductive path 15, which are located on the load 11A side of the individual switch section 21A in the branch path 13A. Diode 23A allows current to flow from the second conductive path 15 to the third conductive path 17A, and blocks the current flowing from the third conductive path 17A to the second conductive path 15.

[0026] Diode 23B is provided between the third conductive path 17B and the second conductive path 15, which are located on the load 11B side of the individual switch section 21B in the branch path 13B. Diode 23B allows current to flow from the second conductive path 15 to the third conductive path 17B, and blocks current flow from the third conductive path 17B to the second conductive path 15.

[0027] In other words, each diode 23A, 23B is placed between each third conductive path 17A, 17B and the second conductive path 15. Each diode 23A, 23B allows current to flow from the second conductive path 15 to the third conductive path 17B corresponding to it, and blocks the current flowing from the third conductive path 17B corresponding to it to the second conductive path 15.

[0028] When the individual switch unit 21A is ON, the output voltage of the power supply unit 10 is supplied to the load 11A via the individual switch unit 21A, as shown by the arrow in Figure 2. When the individual switch unit 21A is OFF and the switch unit 22B is ON, the voltage dropped across the resistor unit 22A is supplied to the load 11A via the second conductive path 15 and the diode 23A, as shown by the arrow in Figure 3.

[0029] When the individual switch unit 21B is ON, the output voltage of the power supply unit 10 is supplied to the load 11B via the individual switch unit 21B, as shown by the arrow in Figure 2. When the individual switch unit 21B is OFF and the switch unit 22B is ON, the voltage dropped across the resistor unit 22A is supplied to the load 11B via the second conductive path 15 and the diode 23B, as shown by the arrow in Figure 3.

[0030] For example, if diode 23A short-circuits in the state shown in Figure 2, current will flow in reverse from the third conductive path 17A to the second conductive path 15 through diode 23A, as shown in Figure 4. Similarly, if diode 23B short-circuits, reverse current will occur through diode 23B. The following configuration is employed to detect such reverse current.

[0031] The first voltage detection unit 24 is an example of a voltage detection unit. The first voltage detection unit 24 detects the voltage of the second conductive path 15. The signal indicating the detection result of the first voltage detection unit 24 is input to the control unit 26. The second voltage detection unit 25 detects the voltage of the third conductive path 17A. The signal indicating the detection result of the second voltage detection unit 25 is input to the control unit 26. The first voltage detection unit 24 and the second voltage detection unit 25 are configured, for example, by known voltage detection circuits. The voltage detection circuit may or may not include a voltage divider circuit.

[0032] The control unit 26 controls the individual switch units 21A and 21B and the step-down unit 22 (specifically, the switch unit 22B). The control unit 26 is configured, for example, by a microcomputer. With at least some (for example, all) of the individual switch units 21A and 21B in the ON state and the switch unit 22B in the OFF state, the control unit 26 determines whether or not reverse current is occurring in the diodes 23A and 23B based on the detection result from the first voltage detection unit 24.

[0033] When the switch unit 22B is in the off state, if no reverse current occurs in either diode 23A or 23B, the voltage across the second conductive path 15 will be equal to the voltage of ground 90. Conversely, if reverse current occurs in either diode 23A or 23B, the voltage across the second conductive path 15 will be equal to the voltage across the third conductive path 17A when the individual switch unit 21A is in the on state (i.e., the output voltage of the power supply unit 10). Therefore, a threshold voltage is set that is 0V or greater and smaller than the voltage across the third conductive path 17A when the individual switch unit 21A is in the on state (i.e., the output voltage of the power supply unit 10). The control unit 26 then determines that reverse current has occurred in at least one of the diodes 23A and 23B if the voltage across the second conductive path 15 exceeds the threshold, and determines that all diodes 23A and 23B are normal if the voltage across the second conductive path 15 does not exceed the threshold.

[0034] For example, the control unit 26 performs the processing shown in Figure 5 when a predetermined determination condition is met. The determination condition may be, for example, a condition in which power supply from the power supply unit 10 to each load 11A, 11B is started, a condition that is met each predetermined time interval, or any other condition.

[0035] In step S11, the control unit 26 controls at least some (for example, all) of the multiple individual switch units 21A and 21B to be in the ON state, while switching the switch unit 22B to the OFF state. At this time, if there are individual switch units that are in the OFF state, the control unit 26 may switch some or all of the individual switch units that are in the ON state to be in the ON state. After that, in step S12, the control unit 26 determines whether the voltage of the second conductive path 15 exceeds a threshold. If the control unit 26 determines that the voltage of the second conductive path 15 exceeds a threshold (if Yes in step S12), in step S13, it determines that reverse current is occurring in at least one of the multiple diodes 23A and 23B. Then, in step S15, the control unit 26 notifies an external source (for example, a higher-level ECU) that reverse current is occurring in at least one of the multiple diodes 23A and 23B. If the control unit 26 determines that the voltage of the second conductive path 15 does not exceed a threshold (if the answer is No in step S12), it determines in step S14 that the diode corresponding to the ON individual switch section is normal. The diode corresponding to the individual switch section is the diode provided between the third conductive path and the second conductive path where the individual switch section is located. For example, diode 23A corresponds to individual switch section 21A, and diode 23B corresponds to individual switch section 21B. After step S14, in step S15, the control unit 26 notifies an external source (e.g., a higher-level ECU) that no reverse current was detected in diodes 23A and 23B.

[0036] 1-2. Effects of the First Embodiment The in-vehicle power supply device 20 can supply the output voltage from the power supply unit 10 to each load 11A and 11B without stepping down the voltage using the step-down unit 22 when each individual switch unit 21A and 21B is ON. Furthermore, when each individual switch unit 21A and 21B is OFF, the in-vehicle power supply device 20 can step down the output voltage from the power supply unit 10 using the step-down unit 22 and supply it to each load 11A and 11B via the second conductive path 15 and each diode 23A and 23B. In other words, the in-vehicle power supply device 20 can selectively supply power from one step-down unit 22 to multiple loads 11A and 11B by switching the ON / OFF states of each individual switch unit 21A and 21B.

[0037] Furthermore, since the in-vehicle power supply device 20 is equipped with a first voltage detection unit 24 that detects the voltage of the second conductive path 15, it is possible to determine that reverse current has occurred in the diodes 23A and 23B based on the detection result of the first voltage detection unit 24.

[0038] The in-vehicle power supply device 20 can determine whether or not reverse current is occurring in at least one of the diodes 23A and 23B based on the detection result from the first voltage detection unit 24, while controlling at least some (for example, all) of the multiple individual switch units 21A and 21B to the ON state and controlling switch unit 22B to the OFF state.

[0039] 2. Second Embodiment In the second embodiment, a configuration in which the step-down unit has a voltage adjustment unit will be described. In the second embodiment, the same reference numerals are used for components that are the same as in the first embodiment, and detailed explanations are omitted.

[0040] The in-vehicle system 201 of the second embodiment includes an in-vehicle power supply device 220 instead of the in-vehicle power supply device 20 of the first embodiment. The in-vehicle power supply device 220 includes a step-down unit 222 instead of the step-down unit 22 of the first embodiment.

[0041] The step-down unit 222 is provided between the first conductive path 14 and the second conductive path 15. The step-down unit 222 has a voltage adjustment unit 222A. The voltage adjustment unit 222A performs a step-down operation to reduce the voltage applied to the first conductive path 14 so that the voltage applied to the second conductive path 15 becomes the target voltage. The target voltage is a value greater than 0V and less than the voltage of the first conductive path 14 (i.e., the output voltage of the power supply unit 10). The voltage adjustment unit 222A is, for example, a DC-DC converter or an LDO.

[0042] The control unit 26 controls the voltage adjustment unit 222A. When the control unit 26 controls at least some (for example, all) of the multiple individual switch units 21A and 21B to be in the ON state and causes the voltage adjustment unit 222A to perform a step-down operation, it determines whether or not reverse current is occurring in the diodes 23A and 23B based on the detection result from the first voltage detection unit 24.

[0043] When the voltage adjustment unit 222A is performing a step-down operation, if no reverse current occurs in either diode 23A or 23B, the voltage across the second conductive path 15 will be equal to the target voltage. Conversely, if reverse current occurs in either diode 23A or 23B, the voltage across the second conductive path 15 will be equal to the voltage across the third conductive path 17A when the individual switch unit 21A is ON (i.e., the output voltage of the power supply unit 10). Therefore, a threshold voltage is set that is greater than the target voltage and less than the voltage across the first conductive path 14 (i.e., the output voltage of the power supply unit 10). The control unit 26 then determines that reverse current has occurred in at least one of the diodes 23A and 23B if the voltage across the second conductive path 15 exceeds the threshold, and determines that all diodes 23A and 23B are normal if the voltage across the second conductive path 15 does not exceed the threshold.

[0044] The control unit 26 performs the processing shown in Figure 5 when a predetermined start condition is met. The start condition may be, for example, a condition for starting the supply of power from the power supply unit 10 to each load 11A, 11B, or it may be any other condition.

[0045] In step S21, the control unit 26 controls at least some (for example, all) of the multiple individual switch units 21A and 21B to be in the ON state, while simultaneously initiating a step-down operation on the voltage adjustment unit 222A. Then, in step S22, the control unit 26 determines whether or not the determination condition has been met. The determination condition may be, for example, a condition that is met every predetermined amount of time, or it may be any other condition. If the control unit 26 determines that the determination condition has not been met (i.e., No in step S22), it returns to step S22. In other words, the control unit 26 repeats the process in step S22 until the determination condition is met.

[0046] If the control unit 26 determines that the determination condition is met (Yes in step S22), it determines in step S23 whether the voltage of the second conductive path 15 exceeds a threshold. If the control unit 26 determines that the voltage of the second conductive path 15 exceeds a threshold (Yes in step S23), it determines in step S24 that reverse current is occurring in at least one of the diodes 23A and 23B. Then, in step S26, the control unit 26 notifies an external source (e.g., a higher-level ECU) that reverse current is occurring in at least one of the diodes 23A and 23B. If the control unit 26 determines that the voltage of the second conductive path 15 does not exceed a threshold (No in step S23), it determines in step S25 that the diode corresponding to the ON state individual switch is normal. After step S25, in step S26, the control unit 26 notifies an external source (e.g., a higher-level ECU) that no reverse current was detected in the diodes 23A and 23B.

[0047] As described above, the in-vehicle power supply device 220 can determine whether or not reverse current is occurring in the diodes 23A and 23B without stopping the output from the step-down unit 222.

[0048] <Other Embodiments> This disclosure is not limited to the embodiments described above and in the drawings. For example, any combination of the features of the embodiments described above or below is possible as long as it does not contradict each other. Furthermore, any feature of the embodiments described above or below may be omitted unless explicitly stated as essential. In addition, the embodiments described above may be modified as follows.

[0049] In the embodiments described above, the configuration determined whether reverse current was occurring in the diode based on whether the voltage of the second conductive path exceeded a threshold. In contrast, a configuration may be used to determine whether reverse current was occurring in the diode based on the voltage of the second conductive path and the voltage of the third conductive path. For example, a configuration may be used to determine whether reverse current was occurring in the diode based on whether the voltage of the second conductive path exceeded a predetermined value less than the voltage of the third conductive path.

[0050] In each of the above embodiments, if there are individual switches that are in the OFF state when determining the reverse current of the diode, at least some (for example, all) of the individual switches that are in the OFF state may be switched to the ON state. With this configuration, a reverse current is more reliably generated when the diode is short-circuited, and therefore the short-circuit failure of the diode can be detected more reliably.

[0051] In each of the above embodiments, there were two loads, two branch lines, two individual switch sections, and two diodes, but there may also be configurations with three or more of each.

[0052] The diode may also be the body diode of a MOSFET.

[0053] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is not limited to the embodiments disclosed herein, but is indicated by the claims, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of symbols]

[0054] 1…In-vehicle systems 10...Power supply section 11A...Load 11B...Load 12…Common power path 13A... Branch road 13B...Branch 14…First conductive path 15…Second conductive circuit 16…Pull-down resistor 17A...Third conductive path 17B...Third conductive path 20…In-vehicle power supply device 21A... Individual switch section 21B... Individual switch section 22... Step-down section 22A...Resistance section 22B... Switch section 23A…diode 23B…Diode 24…First voltage detection unit (voltage detection unit) 25...Second voltage detection unit 26... Control Unit 90... Ground 201... In-vehicle systems 220…In-vehicle power supply device 222... Step-down section 222A...Voltage adjustment section

Claims

1. An in-vehicle power supply device included in an in-vehicle system, comprising: a power supply unit; a common power line connected to the power supply unit; a plurality of branch lines branching from the common power line and connected to each load; a first conductive line branching from the common power line separately from the plurality of branch lines; a second conductive line provided between the first conductive line and the plurality of branch lines; and a plurality of individual switch units provided in each of the plurality of branch lines, A step-down section is provided between the first conductive path and the second conductive path, The branch path comprises a plurality of diodes individually provided between a third conductive path located on the load side of the individual switch section in each of the aforementioned branch paths and the second conductive path, The step-down unit has a step-down function that steps down the voltage applied to the first conductive path and applies it to the second conductive path, and a stop function that stops the output to the second conductive path, and either has only the step-down function, or has both the step-down function and the stop function. Each of the diodes allows current to flow from the second conductive path to the third conductive path, and blocks current flow from the third conductive path to the second conductive path. Furthermore, it includes a voltage detection unit for detecting the voltage of the second conductive path. In-vehicle power supply device.

2. The step-down section has a configuration in which a resistor and a switch are connected in series. The system includes a control unit that controls the aforementioned switch section, The control unit, with the switch unit controlled to the OFF state, determines whether or not reverse current is occurring in the diode based on the detection result from the voltage detection unit. The vehicle-mounted power supply device according to claim 1.

3. The step-down unit includes a voltage adjustment unit that performs a step-down operation to reduce the voltage applied to the first conductive path so that the voltage applied to the second conductive path becomes the target voltage. The vehicle-mounted power supply device according to claim 1.

4. The system includes a control unit that controls the voltage adjustment unit, The control unit, while the voltage adjustment unit is performing the step-down operation, determines whether or not reverse current is occurring in the diode based on the detection result from the voltage detection unit. The vehicle-mounted power supply device according to claim 3.

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