Power supply device

Abstract

A power supply device (20) is included in an in-vehicle system (1). The in-vehicle system (1) comprises: an electricity storage unit (11); a power path (14) to which power from the electricity storage unit (11) is supplied; a voltage conversion unit (12) that converts an input voltage and outputs the converted input voltage to the power path (14); and a load (15) that is connected to the power path (14). The power supply device (20) is provided with: a first switch unit (21) provided further on the voltage conversion unit (12) side than the load (15) in the power path (14); and a control unit (40) for controlling the first switch unit (21). The first switch unit (21) switches between an on state in which a current is allowed to flow from the voltage conversion unit (12) side to the load (15) side via the first switch unit (21) and an off state in which the current flowing from the voltage conversion unit (12) side to the load (15) side via the first switch unit (21) is cut off. The control unit (40) switches the first switch unit (21) to the off state when it is determined that the output voltage of the voltage conversion unit (12) has become overvoltage.

Description

power supply device

[0001] The present disclosure relates to a power supply device.

[0002] The power supply system disclosed in Patent Document 1 includes a first system and a second system as power systems. The first system includes a first power output unit, and the second system includes a second power output unit. The power supply system includes a first path and a second path as main paths. The first path and the second path connect the first power output unit and the second power output unit. The second path is connected to the first path via an inter-system switch. When a ground fault occurs, the inter-system switch is turned off, and the first system and the second system are disconnected.

[0003] JP 2019-62727 A

[0004] Although Patent Document 1 describes measures to be taken in the event of a ground fault, it does not take into consideration measures to be taken in the event of an overvoltage.

[0005] The present disclosure aims to provide a technique capable of preventing an overvoltage from being applied to an object to be protected.

[0006] The power supply device of the present disclosure is a power supply device included in an in-vehicle system having a power storage unit, a power path to which power is supplied from the power storage unit, a voltage conversion unit that converts an input voltage and outputs it to the power path, and a load connected to the power path, and further comprising: a first switch unit provided on the power path closer to the voltage conversion unit than the load; and a control unit that controls the first switch unit, wherein the first switch unit switches between an on state that allows current to flow from the voltage conversion unit side to the power storage unit side and the load side through the first switch unit, and an off state that blocks current flowing from the voltage conversion unit side to the power storage unit side and the load side through the first switch unit, and the control unit switches the first switch unit to the off state when it determines that the output voltage of the voltage conversion unit has become an overvoltage.

[0007] The technology according to the present disclosure can prevent an overvoltage from being applied to an object to be protected.

[0008] FIG. 1 is a configuration diagram of an in-vehicle system including a power supply device according to a first embodiment. FIG. 2 is an explanatory diagram conceptually illustrating the operation of the power supply device according to the first embodiment during normal operation. FIG. 3 is an explanatory diagram conceptually illustrating the operation of the power supply device according to the first embodiment when the output voltage of the voltage conversion unit becomes an overvoltage. FIG. 4 is an explanatory diagram conceptually illustrating the operation of the power supply device according to the first embodiment when a ground fault occurs on the voltage conversion unit side. FIG. 5 is an explanatory diagram conceptually illustrating the operation of the power supply device according to the first embodiment when a ground fault occurs on the power storage unit side. FIG. 6 is an explanatory diagram conceptually illustrating the operation of the power supply device according to the second embodiment when a ground fault occurs on the voltage conversion unit side. FIG. 7 is an explanatory diagram conceptually illustrating the operation of the power supply device according to the second embodiment when a ground fault occurs on the power storage unit side.

[0009] [Description of Embodiments of the Present Disclosure] In the following, embodiments according to the present disclosure are listed and exemplified.

[0010] [1] A power supply device included in an in-vehicle system having a power storage unit, a power path to which power from the power storage unit is supplied, a voltage conversion unit that converts an input voltage and outputs the converted voltage to the power path, and a load connected to the power path, the power supply device comprising: a first switch unit provided on the power path closer to the voltage conversion unit than the load; and a control unit that controls the first switch unit, wherein the first switch unit switches between an ON state that allows current to flow from the voltage conversion unit side to the power storage unit side and the load side through the first switch unit, and an OFF state that blocks current flowing from the voltage conversion unit side to the power storage unit side and the load side through the first switch unit, and the control unit switches the first switch unit to the OFF state when it is determined that the output voltage of the voltage conversion unit has become an overvoltage.

[0011] In the above-described power supply device, there is a risk that the output voltage of the voltage conversion unit may become an overvoltage. If the output voltage of the voltage conversion unit becomes an overvoltage, there is a concern that an overvoltage may be applied to the power storage unit and the load via the power path. To address this problem, the above-described power supply device can prevent the overvoltage from being applied to the power storage unit and the load by switching the first switch unit to an off state when the output voltage of the voltage conversion unit becomes an overvoltage.

[0012] [2] A power supply comprising: a second switch unit provided on the power path closer to the voltage conversion unit than the load; and a third switch unit provided on the power path closer to the power storage unit than the load, wherein the second switch unit switches between an off state in which it cuts off current flowing from the power storage unit side and the load side to the voltage conversion unit side through itself and allows current to flow from the voltage conversion unit side to the power storage unit side and the load side through itself, and an on state in which it allows current to flow from the voltage conversion unit side to the power storage unit side and the load side through itself with a lower voltage drop than in the off state; and the third switch unit switches between an off state in which it cuts off current flowing from the voltage conversion unit side and the load side to the power storage unit side through itself and allows current to flow from the power storage unit side to the voltage conversion unit side and the load side through itself, and an on state in which it allows current to flow from the power storage unit side to the voltage conversion unit side and the load side through itself with a lower voltage drop than in the off state. The power supply device according to [1], wherein when the control unit determines that the voltage of the power path has become low while controlling the first switch unit, the second switch unit, and the third switch unit to be in an on state, the control unit switches the second switch unit and the third switch unit to an off state while maintaining the first switch unit in an on state.

[0013] The power supply device can interrupt current flowing from the power storage unit side and the load side to the voltage conversion unit side when the second switch unit is in an off state, and can interrupt current flowing from the voltage conversion unit side and the load side to the power storage unit side when the third switch unit is in an off state. Furthermore, the control unit controls the first switch unit, the second switch unit, and the third switch unit to an on state, thereby suppressing voltage drops at the second switch unit and the third switch unit and allowing current to flow from the voltage conversion unit and the power storage unit to the load. Furthermore, when the control unit determines that the voltage of the power path has become low in this state, it switches the second switch unit and the third switch unit to an off state while maintaining the first switch unit in an on state. With this configuration, if the voltage of the power path has become low due to the voltage conversion unit side, the second switch unit can interrupt the flow of current to the voltage conversion unit side and allow current to flow from the power storage unit to the load. Conversely, if the cause of the low voltage in the power path is the power storage unit side, the third switch unit can block the flow of current to the power storage unit side while allowing current to flow from the voltage conversion unit to the load. In other words, with this configuration, it is possible to continue power supply to the load without determining whether the cause of the low voltage in the power path is the voltage conversion unit side or the power storage unit side.

[0014] [3] A power supply comprising: a second switch unit provided on the power path closer to the voltage conversion unit than the load; and a third switch unit provided on the power path closer to the power storage unit than the load, wherein the second switch unit switches between an off state in which it cuts off current flowing from the power storage unit side and the load side to the voltage conversion unit side through itself and allows current to flow from the voltage conversion unit side to the power storage unit side and the load side through itself, and an on state in which it allows current to flow from the voltage conversion unit side to the power storage unit side and the load side through itself with a lower voltage drop than in the off state; and the third switch unit switches between an off state in which it cuts off current flowing from the voltage conversion unit side and the load side to the power storage unit side through itself and allows current to flow from the power storage unit side to the voltage conversion unit side and the load side through itself, and an on state in which it allows current to flow from the power storage unit side to the voltage conversion unit side and the load side through itself with a lower voltage drop than in the off state. The power supply device according to [1] or [2], wherein when the control unit determines that the output voltage of the voltage conversion unit has become an overvoltage while controlling the first switch unit, the second switch unit, and the third switch unit to be in an on state, the control unit switches the first switch unit to an off state while maintaining the second switch unit and the third switch unit in an on state.

[0015] The power supply device can interrupt current flowing from the power storage unit side and the load side to the voltage conversion unit side when the second switch unit is in an off state, and can interrupt current flowing from the voltage conversion unit side and the load side to the power storage unit side when the third switch unit is in an off state. Furthermore, by controlling the first switch unit, the second switch unit, and the third switch unit to an on state, the control unit can allow current to flow from the voltage conversion unit and the power storage unit to the load while suppressing voltage drops at the second switch unit and the third switch unit. Furthermore, when the control unit determines that the output voltage of the voltage conversion unit has become an overvoltage in this state, it switches the first switch unit to an off state while maintaining the second switch unit and the third switch unit in an on state. This allows the control unit to minimize operations for interrupting the overvoltage. This facilitates simplification of control by the control unit.

[0016] [4] The power supply device according to any one of [1] to [3], further comprising a second switch unit provided on the voltage conversion unit side of the load in the power path, wherein the second switch unit switches between an off state in which the second switch unit cuts off current flowing from the storage unit side and the load side to the voltage conversion unit side through the second switch unit and allows current to flow from the voltage conversion unit side to the storage unit side and the load side through the second switch unit, and an on state in which current is allowed to flow from the voltage conversion unit side to the storage unit side and the load side through the second switch unit with a voltage drop lower than in the off state, and wherein the control unit controls the second switch unit to the off state when it determines that an overcurrent is flowing in the voltage conversion unit while controlling the second switch unit to the on state.

[0017] By controlling the second switch unit to the on state, the control unit can allow current to flow from the voltage conversion unit to the load while suppressing a voltage drop across the second switch unit. Furthermore, the control unit controls the second switch unit to the off state when it determines that an overcurrent is flowing through the voltage conversion unit. Therefore, even if a ground fault occurs on the voltage conversion unit side and an overcurrent flows through the voltage conversion unit, power is supplied from the power storage unit to the load by controlling the second switch unit to the off state.

[0018] [5] The power supply device according to any one of [1] to [4], further comprising: a third switch unit provided on the power path closer to the storage unit than the load; wherein the third switch unit switches between an off state in which it cuts off current flowing from the voltage conversion unit and the load to the storage unit through itself and allows current to flow from the storage unit to the voltage conversion unit and the load through itself, and an on state in which it allows current to flow from the storage unit to the voltage conversion unit and the load through itself with a voltage drop that is lower than in the off state; and wherein the control unit controls the third switch unit to the off state when it determines that an overcurrent is flowing in the storage unit while controlling the third switch unit to the on state.

[0019] By controlling the third switch unit to the on state, the control unit can allow current to flow from the power storage unit to the load while suppressing a voltage drop across the third switch unit. Furthermore, when the control unit determines that an overcurrent is flowing through the power storage unit, the control unit controls the third switch unit to the off state. Therefore, even if a ground fault occurs on the power storage unit side and an overcurrent flows through the power storage unit, power is supplied from the voltage conversion unit to the load by controlling the third switch unit to the off state.

[0020] [Details of the embodiment of the present disclosure] 1. First embodiment 1-1. Configuration of in-vehicle system 1 The in-vehicle system 1 of the first embodiment shown in Fig. 1 is a system mounted on a vehicle. The in-vehicle system 1 includes a power storage unit 11, a voltage conversion unit 12, a power supply source 13, a power path 14, and a load 15.

[0021] The power storage unit 11 is, for example, a battery or a capacitor. The battery is, for example, a lithium-ion battery. The capacitor is, for example, a lithium-ion capacitor. A power path 14 is provided between the power storage unit 11 and the voltage conversion unit 12. The power path 14 is electrically connected to the positive terminal of the power storage unit 11 and the voltage conversion unit 12. Power from the power storage unit 11 is supplied to the power path 14. The voltage conversion unit 12 performs a conversion operation of increasing or decreasing the input voltage input from the power supply source 13 and outputting it to the power path 14. The power supply source 13 is, for example, a battery or a generator. The load 15 is electrically connected to the power path 14 via a branch path 16.

[0022] The in-vehicle system 1 includes a power supply device 20. The power supply device 20 is a device mounted on a vehicle. The power supply device 20 includes a first switch unit 21, a second switch unit 22, a third switch unit 23, voltage detection units 31, 32, and 33, current detection units 34 and 35, and a control unit 40.

[0023] The first switch unit 21 is provided on the power path 14 closer to the voltage conversion unit 12 than the load 15. That is, the first switch unit 21 is provided between the power storage unit 11 and the load 15 and the voltage conversion unit 12. When in an off state, the first switch unit 21 blocks current flowing from the voltage conversion unit 12 side to the power storage unit 11 and the load 15 side through itself, and allows current to flow from the power storage unit 11 and the load 15 side to the voltage conversion unit 12 side through itself. When in an on state, the first switch unit 21 allows current to flow from the voltage conversion unit 12 side to the power storage unit 11 and the load 15 side through itself, and allows current to flow from the power storage unit 11 and the load 15 side to the voltage conversion unit 12 side through itself.

[0024] The second switch unit 22 is provided on the power path 14 closer to the voltage conversion unit 12 than the load 15. That is, the second switch unit 22 is provided between the power storage unit 11 and the load 15 and the voltage conversion unit 12. When the second switch unit 22 is in an off state, it blocks current flowing from the power storage unit 11 and the load 15 to the voltage conversion unit 12 through itself, and allows current to flow from the voltage conversion unit 12 to the power storage unit 11 and the load 15 through itself. When the second switch unit 22 is in an on state, it allows current to flow from the voltage conversion unit 12 to the power storage unit 11 and the load 15 through itself with a lower voltage drop than when the second switch unit 22 is in an off state, and allows current to flow from the power storage unit 11 and the load 15 to the voltage conversion unit 12 through itself.

[0025] The third switch unit 23 is provided on the power path 14 closer to the power storage unit 11 than the load 15. That is, the third switch unit 23 is provided between the power storage unit 11 and the voltage conversion unit 12 and load 15. When in an off state, the third switch unit 23 blocks current flowing from the voltage conversion unit 12 and the load 15 to the power storage unit 11, and allows current to flow from the power storage unit 11 to the voltage conversion unit 12 and the load 15. When in an on state, the third switch unit 23 allows current to flow from the power storage unit 11 to the voltage conversion unit 12 and the load 15 with a lower voltage drop than when in an off state, and allows current to flow from the voltage conversion unit 12 and the load 15 to the power storage unit 11.

[0026] The first switch section 21, the second switch section 22, and the third switch section 23 are, for example, MOSFETs (Metal-Oxide-Semiconductor Field Effect Transistors).

[0027] The voltage detection units 31, 32, and 33 detect the voltage of the power path 14. The voltage detection unit 31 detects the voltage between the first switch unit 21 and the second switch unit 22 and the voltage conversion unit 12. The voltage detection unit 32 detects the voltage between the third switch unit 23 and the power storage unit 11. The voltage detection unit 33 detects the voltage between the first switch unit 21 and the second switch unit 22 and the third switch unit 23. Each of the voltage detection units 31, 32, and 33 is, for example, a known voltage detection circuit. Signals indicating the detection results of the voltage detection units 31, 32, and 33 are input to the control unit 40.

[0028] The current detection unit 34 detects the current flowing in the voltage conversion unit 12. The current detection unit 34 detects the current flowing in the power path 14 on the voltage conversion unit 12 side relative to the first switch unit 21 and the second switch unit 22. The current detection unit 35 detects the current flowing in the power storage unit 11. The current detection unit 35 detects the current flowing in the power path 14 on the power storage unit 11 side relative to the third switch unit 23. Each of the current detection units 34, 35 is, for example, a known current sensor. Signals indicating the detection results of the current detection units 34, 35 are input to the control unit 40.

[0029] The control unit 40 is configured, for example, by a microcomputer. The microcomputer has a memory, a CPU, etc. The control unit 40 is realized, for example, by the CPU executing a computer program stored in the memory. Note that the control unit 40 is not limited to being configured by software as described above, and may also be configured by hardware or a combination of software and hardware.

[0030] The control unit 40 controls the first switch unit 21, the second switch unit 22, and the third switch unit 23. The control unit 40 switches the first switch unit 21 to the OFF state when it determines that the output voltage of the voltage conversion unit 12 has become an overvoltage. More specifically, when the control unit 40 determines that the output voltage of the voltage conversion unit 12 has become an overvoltage while controlling the first switch unit 21, the second switch unit 22, and the third switch unit 23 to the ON state, the control unit 40 switches the first switch unit 21 to the OFF state while keeping the second switch unit 22 and the third switch unit 23 in the ON state. The control unit 40 determines, for example, whether the output voltage of the voltage conversion unit 12 has exceeded an overvoltage threshold, and when the output voltage of the voltage conversion unit 12 has exceeded the overvoltage threshold, it determines that the output voltage of the voltage conversion unit 12 has become an overvoltage. The control unit 40 may monitor all or only some of the voltage detection units 31, 32, and 33. When the control unit 40 monitors multiple voltage detection units (e.g., voltage detection units 31, 33), if the voltage detected by any of the monitored units exceeds the overvoltage threshold, it determines that the output voltage of the voltage conversion unit 12 has become an overvoltage.

[0031] When the control unit 40 determines that the voltage of the power path 14 has become low while controlling the first switch unit 21, the second switch unit 22, and the third switch unit 23 to the on state, the control unit 40 switches the second switch unit 22 and the third switch unit 23 to the off state while maintaining the first switch unit 21 in the on state. The control unit 40 determines whether the voltage of the power path 14 has become equal to or lower than the low-voltage threshold, and determines that the voltage of the power path 14 has become low when the voltage of the power path 14 has become equal to or lower than the low-voltage threshold. The control unit 40 may monitor all or only some of the voltage detection units 31, 32, and 33. When the control unit 40 monitors multiple voltage detection units (e.g., the voltage detection units 31, 32, and 33), the control unit 40 determines that the voltage of the power path 14 has become low when the voltage detected by any of the voltage detection units becomes equal to or lower than the low-voltage threshold.

[0032] 1-2. Example of Operation of In-Vehicle System 1 The control unit 40 controls the first switch unit 21, the second switch unit 22, and the third switch unit 23 to the ON state, for example, when a start condition is met. The start condition may be, for example, that the start switch of the vehicle is switched to the ON state, or may be another condition. The start switch may be, for example, an ignition switch or a power switch.

[0033] For example, when the start switch of the vehicle is switched to the ON state or while the vehicle is running, the voltage conversion unit 12 performs a conversion operation, thereby supplying power from the voltage conversion unit 12 to the power path 14. In this state, the first switch unit 21, the second switch unit 22, and the third switch unit 23 are turned ON, and as shown in FIG. 2 , power is supplied from the power storage unit 11 and the voltage conversion unit 12 to the load 15 in a state in which voltage drops at the second switch unit 22 and the third switch unit 23 are suppressed.

[0034] 2, when the output voltage of the voltage conversion unit 12 becomes an overvoltage, the control unit 40 switches the first switch unit 21 to the OFF state while keeping the second switch unit 22 and the third switch unit 23 in the ON state, as shown in Fig. 3. As a result, application of an overvoltage to the power storage unit 11 and the load 15 is prevented, and power supply from the power storage unit 11 to the load 15 continues.

[0035] In this way, by controlling the first switch unit 21, the second switch unit 22, and the third switch unit 23 to the on state, the power supply device 20 can suppress voltage drops at the second switch unit 22 and the third switch unit 23 while allowing current to flow from the voltage conversion unit 12 and the power storage unit 11 to the load 15. In this state, if the output voltage of the voltage conversion unit 12 becomes an overvoltage, the power supply device 20 can prevent the overvoltage from being applied to the power storage unit 11 and the load 15 by switching the first switch unit 21 to the off state.

[0036] In particular, when it is determined that the output voltage of the voltage conversion unit 12 has become an overvoltage, the power supply device 20 switches only the first switch unit 21 to the off state, thereby minimizing the operation for cutting off the overvoltage. Therefore, according to the power supply device 20, the control by the control unit 40 can be easily simplified.

[0037] 2 , if a ground fault occurs on the voltage conversion unit 12 side and the voltage of the power path 14 becomes low, the control unit 40 switches the second switch unit 22 and the third switch unit 23 to the OFF state while maintaining the first switch unit 21 in the ON state, as shown in FIG. 4 . As a result, power supply from the power storage unit 11 to the load 15 continues. The control unit 40 also performs a similar operation when a ground fault occurs on the power storage unit 11 side and the voltage of the power path 14 becomes low in the state shown in FIG. 2 . That is, as shown in FIG. 5 , the control unit 40 switches the second switch unit 22 and the third switch unit 23 to the OFF state while maintaining the first switch unit 21 in the ON state. As a result, power supply from the voltage conversion unit 12 to the load 15 continues. In other words, with this configuration, power supply to the load 15 can be continued without determining whether the low voltage of the power path 14 is caused by the voltage conversion unit 12 side or the power storage unit 11 side.

[0038] 2. Second Embodiment In the first embodiment, an example in which a ground fault is detected by detecting a low voltage is described. In contrast, in the second embodiment, an example in which a ground fault is detected by detecting an overcurrent is described. Note that the configuration of the second embodiment is the same as the configuration shown in FIG. 1 , and therefore the description will be made with reference to FIG. 1 .

[0039] The control unit 40 of the power supply device 20 of the second embodiment controls the second switch unit 22 to the off state when it determines that an overcurrent is flowing through the voltage conversion unit 12. The control unit 40 identifies the current flowing through the voltage conversion unit 12 based on a signal indicating the detection result of the current detection unit 34. The control unit 40 determines whether the current flowing through the voltage conversion unit 12 exceeds a first threshold current, and when the current flowing through the voltage conversion unit 12 exceeds the first threshold current, it determines that an overcurrent is flowing through the voltage conversion unit 12.

[0040] The control unit 40 controls the third switch unit 23 to the OFF state when it determines that an overcurrent is flowing through the power storage unit 11. The control unit 40 identifies the current flowing through the power storage unit 11 based on a signal indicating the detection result of the current detection unit 35. The control unit 40 determines whether the current flowing through the power storage unit 11 has exceeded a second threshold current, and determines that an overcurrent is flowing through the power storage unit 11 when the current flowing through the power storage unit 11 has exceeded the second threshold current.

[0041] In the state shown in Fig. 2 , if a ground fault occurs on the voltage conversion unit 12 side, a current flows backward from the load 15 side to the voltage conversion unit 12 side, causing an overcurrent to flow through the voltage conversion unit 12. Therefore, the control unit 40 determines that an overcurrent is flowing through the voltage conversion unit 12, and switches the second switch unit 22 to the OFF state while keeping the first switch unit 21 and the third switch unit 23 in the ON state. As a result, as shown in Fig. 6 , power supply from the power storage unit 11 to the load 15 continues. In other words, even if a ground fault occurs on the voltage conversion unit 12 side, the power supply device 20 can continue power supply from the power storage unit 11 to the load 15 by controlling the second switch unit 22 to the OFF state.

[0042] In the state shown in Fig. 2 , if a ground fault occurs on the side of the power storage unit 11, a current flows backward from the side of the load 15 to the side of the power storage unit 11, causing an overcurrent to flow through the power storage unit 11. Therefore, the control unit 40 determines that an overcurrent is flowing through the power storage unit 11, and switches the third switch unit 23 to the OFF state while keeping the first switch unit 21 and the second switch unit 22 in the ON state. As a result, as shown in Fig. 7 , power supply from the voltage conversion unit 12 to the load 15 continues. In other words, even if a ground fault occurs on the side of the power storage unit 11, the power supply device 20 can continue power supply from the voltage conversion unit 12 to the load 15 by controlling the third switch unit 23 to the OFF state.

[0043] <Other Embodiments> The present disclosure is not limited to the embodiments described above and in the drawings. For example, any combination of features of the above-described or below-described embodiments is possible within a range that does not contradict. Furthermore, any feature of the above-described or below-described embodiments may be omitted unless explicitly stated as essential. Furthermore, the above-described embodiments may be modified as follows.

[0044] The configuration for determining a low voltage in the power line 14 described in the first embodiment and the configuration for determining an overcurrent described in the second embodiment may be combined.

[0045] Only two or one of the voltage detection units 31, 32, and 33 may be provided.

[0046] It should be noted that the embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is not limited to the embodiments disclosed herein, and is intended to include all modifications within the scope indicated by the claims or within the scope equivalent to the claims.

[0047] REFERENCE SIGNS LIST 1... In-vehicle system 11... Power storage unit 12... Voltage conversion unit 13... Power supply source 14... Power path 15... Load 16... Branch path 20... Power supply device 21... First switch unit 22... Second switch unit 23... Third switch unit 31... Voltage detection unit 32... Voltage detection unit 33... Voltage detection unit 34... Current detection unit 35... Current detection unit 40... Control unit

Claims

1. A power supply device included in an in-vehicle system having a power storage unit, a power path to which power from the power storage unit is supplied, a voltage conversion unit that converts input voltage and outputs it to the power path, and a load connected to the power path, the power supply device comprising: a first switch unit provided on the power path closer to the voltage conversion unit than the load; and a control unit that controls the first switch unit, wherein the first switch unit switches between an ON state that allows current to flow from the voltage conversion unit side to the power storage unit side and the load side through the first switch unit, and an OFF state that blocks current flowing from the voltage conversion unit side to the power storage unit side and the load side through the first switch unit, and the control unit switches the first switch unit to the OFF state when it is determined that the output voltage of the voltage conversion unit has become an overvoltage.

2. A power supply comprising: a second switch unit provided on the power path closer to the voltage conversion unit than the load; and a third switch unit provided on the power path closer to the power storage unit than the load, wherein the second switch unit switches between an off state in which it cuts off current flowing from the power storage unit side and the load side to the voltage conversion unit side through itself and allows current to flow from the voltage conversion unit side to the power storage unit side and the load side through itself, and an on state in which it allows current to flow from the voltage conversion unit side to the power storage unit side and the load side through itself with a lower voltage drop than in the off state; and the third switch unit switches between an off state in which it cuts off current flowing from the voltage conversion unit side and the load side to the power storage unit side through itself and allows current to flow from the power storage unit side to the voltage conversion unit side and the load side through itself, and an on state in which it allows current to flow from the power storage unit side to the voltage conversion unit side and the load side through itself with a lower voltage drop than in the off state.

2. The power supply device according to claim 1, wherein, when the control unit determines that the voltage of the power path has become low while controlling the first switch unit, the second switch unit, and the third switch unit to be in an on state, the control unit switches the second switch unit and the third switch unit to an off state while maintaining the first switch unit in an on state.

3. A power supply comprising: a second switch unit provided on the power path closer to the voltage conversion unit than the load; and a third switch unit provided on the power path closer to the power storage unit than the load, wherein the second switch unit switches between an off state in which it cuts off current flowing from the power storage unit side and the load side to the voltage conversion unit side through itself and allows current to flow from the voltage conversion unit side to the power storage unit side and the load side through itself, and an on state in which it allows current to flow from the voltage conversion unit side to the power storage unit side and the load side through itself with a lower voltage drop than in the off state; and the third switch unit switches between an off state in which it cuts off current flowing from the voltage conversion unit side and the load side to the power storage unit side through itself and allows current to flow from the power storage unit side to the voltage conversion unit side and the load side through itself, and an on state in which it allows current to flow from the power storage unit side to the voltage conversion unit side and the load side through itself with a lower voltage drop than in the off state.

3. The power supply device according to claim 1, wherein when the control unit determines that the output voltage of the voltage conversion unit has become an overvoltage while controlling the first switch unit, the second switch unit, and the third switch unit to be in an on state, the control unit switches the first switch unit to an off state while maintaining the second switch unit and the third switch unit in an on state.

4. The power supply device according to claim 1 or claim 2, further comprising a second switch unit provided on the voltage conversion unit side of the load in the power path, wherein the second switch unit switches between an off state in which it cuts off current flowing from the power storage unit side and the load side to the voltage conversion unit side through itself and allows current to flow from the voltage conversion unit side to the power storage unit side and the load side through itself, and an on state in which it allows current to flow from the voltage conversion unit side to the power storage unit side and the load side through itself with a voltage drop that is lower than in the off state, and wherein the control unit controls the second switch unit to the off state when it determines that an overcurrent is flowing in the voltage conversion unit while controlling the second switch unit to the on state.

5. The power supply device according to claim 1 or claim 2, further comprising: a third switch unit provided on the power path closer to the storage unit than the load, wherein the third switch unit switches between an off state in which it cuts off current flowing from the voltage conversion unit and the load to the storage unit through itself and allows current to flow from the storage unit to the voltage conversion unit and the load through itself, and an on state in which it allows current to flow from the storage unit to the voltage conversion unit and the load through itself with a voltage drop that is lower than in the off state, and wherein the control unit controls the third switch unit to the off state when it determines that an overcurrent is flowing in the storage unit while controlling the third switch unit to the on state.

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