Power supply system

Abstract

To provide a power supply system capable of protecting a voltage conversion unit from a ground fault current with an inexpensive and simple configuration even when having the voltage conversion unit for stepping up / down the voltage of power supplied to a standby power supply.SOLUTION: The power supply system 1 includes a power supply 3 that supplies power to a second load 6 via a first wire 5, a storage battery 8 that stores power supplied from the power supply 3 via a second wire 31 connected to the first wire 5 and supplies power to the second load 6 when the power supply 3 cannot supply power to the second load 6, a first switch 7 provided between the power supply 3 and a contact point 29 with the second wire 31 on the first wire 5, a voltage conversion unit 9 that is provided to connect the second wire 31 and the storage battery 8 and steps up and down a voltage of power supplied from the power supply 3, a second switch 32 connected in parallel with the second wire 31 and the voltage conversion unit 9, and a first fuse 37 that is provided in an output unit 12 of the voltage conversion unit 9 and cuts off a current by being melted when a ground fault current flows therein.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a power supply system. [Background technology]

[0002] In a known power supply system, when power is supplied from a power supply to a load, power is also supplied to and charged in a backup power supply such as a storage battery, and when power supply to the load becomes unable to be supplied from the power supply to the load, power is supplied from the backup power supply to the load. In this power supply system, in order to increase the voltage of the backup power supply, the power supplied from the power supply may be boosted by a voltage conversion unit such as a DC / DC converter and then supplied to the backup power supply (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-7922 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the power supply system described in Patent Document 1 has a switch provided in the input / output section of the voltage conversion section to cut off current in order to protect the voltage conversion section from a ground fault current when the input / output section of the voltage conversion section has a ground fault, which requires a circuit to control the switch, which not only complicates the configuration but also increases the cost of the switch itself.

[0005] The present invention has been made to solve such problems, and its object is to provide a power supply system that can protect a voltage conversion unit that increases or decreases the voltage of the power supplied to the standby power supply from a ground fault current with an inexpensive and simple configuration. [Means for solving the problem]

[0006] The power supply system of the present invention includes a power supply that supplies power to a load via a first wiring, a storage battery that stores power supplied from the power supply via a second wiring connected to the first wiring and supplies power to the load when the power supply is unable to supply power to the load, a first switch that is provided on the first wiring between a connection portion with the second wiring and the power supply and that conducts when the power supply supplies power to the load, a voltage conversion portion that is provided to connect the second wiring and the storage battery and that increases or decreases the voltage of the power supplied from the power supply, a second switch that is connected in parallel with the second wiring and the voltage conversion portion and that conducts when the storage battery supplies power to the load, and a pair of circuit breakers that are provided at the input and output portions of the voltage conversion portion and that cut off the current when a ground fault current flows, wherein of the pair of circuit breakers, the first circuit breaker provided at the output portion is a first fuse that cuts off the current by melting when a ground fault current flows. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a power supply system that can protect a voltage conversion unit that increases or decreases the voltage of power supplied to a standby power supply from a ground fault current with an inexpensive and simple configuration. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a configuration diagram showing a power supply system according to a first embodiment. [Figure 2] 4 is a flowchart illustrating the operation of the power supply system. [Figure 3] FIG. 4 is a diagram illustrating the operation of the power supply system during normal driving. [Figure 4] FIG. 4 is a diagram illustrating the operation of the power supply system during evacuation travel. [Figure 5] 10A and 10B are diagrams illustrating a case where the input and output parts of the voltage conversion unit have a ground fault. [Figure 6] FIG. 10 is a configuration diagram showing a power supply system according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention will be described below in accordance with preferred embodiments. Note that the present invention is not limited to the embodiments shown below and can be modified as appropriate without departing from the spirit of the present invention. In addition, in the embodiments shown below, some components are omitted from illustration and description, but it goes without saying that publicly known or well-known technologies are applied as appropriate to the details of the omitted technologies within the scope of the content described below.

[0010] First, the configuration of a power supply system according to the first embodiment will be described with reference to Fig. 1. Fig. 1 is a configuration diagram showing the power supply system according to the first embodiment. Here, the power supply system 1 is exemplified as a system that is mounted on a vehicle with an autonomous driving function and supplies power to a load of the vehicle. As shown in Fig. 1, the power supply system 1 includes a power supply 3, a lead-acid battery 4, a storage battery 8, a first switch 7, a voltage conversion unit 9, a second switch 32, and a breaker unit 11. The power supply system 1 also includes a control unit 43.

[0011] The power supply 3 is a device that supplies power to a load of the vehicle, and more specifically, a battery such as a lithium-ion battery that supplies power to a first load 13 and a second load 6 (load). The first load 13 is a load such as a device that consumes power in the vehicle and on-board equipment, and includes important loads and general loads. Important loads are loads necessary for the vehicle to run, such as a steering device, a braking device, and a sensor. General loads are loads such as on-board equipment that are not essential for the vehicle to run but are installed to keep vehicle occupants comfortable inside the vehicle, such as an air conditioner and audio equipment. The power supply 3 is connected to the first load 13 via a first wiring 5 and a first branch wiring 17. The first wiring 5 is a wiring that transmits power supplied from the power supply 3, and one end is connected to the power supply 3. In addition, a fuse 19 is provided at the connection point of the first wiring 5 with the power supply 3. The first branch wiring 17 is a wiring that connects the first wiring 5 and the first load 13, and one end is connected to a contact 15 located midway along the first wiring 5, and the other end is connected to the first load 13. The second load 6 is a device that consumes power in the vehicle, similar to the first load 13, and includes an important load. The other end of the first wiring 5 is connected to the second load 6, and power is supplied from the power supply 3. The reason why the power supply system 1 is configured to supply power to the vehicle loads separately as the first load 13 and the second load 6 is to provide redundancy in the power supply, specifically, to enable the vehicle to run even if power is supplied only to the second load 6, for example.

[0012] The lead-acid battery 4 is a battery that supplies dark current to the first load 13 and the second load 6, and is provided as needed. The lead-acid battery 4 is connected to the first wiring 5 via a second branch wiring 23. The second branch wiring 23 is a wiring that connects the lead-acid battery 4 and the first wiring 5, and has one end connected to the lead-acid battery 4 and the other end connected to a contact 21 that is provided in the first wiring 5 on the power source 3 side relative to the contact 15. In addition, a fuse 25 is provided at the connection portion of the second branch wiring 23 with the lead-acid battery 4.

[0013] The storage battery 8 is a battery such as a lithium-ion storage battery that stores power supplied from the power source 3 and supplies power to the second load 6 when the power source 3 is unable to supply power to the second load 6. Power is supplied from the power source 3 via the first wiring 5 and the second wiring 31. The second wiring 31 is a wiring that connects the power source 3 and the storage battery 8, and one end is connected to a contact 29 (connection portion) that is provided on the first wiring 5 closer to the second load 6 than the contact 15. The portion of the first wiring 5 that connects the contact 29 to the second load 6 is also referred to as the connection wiring 5a. The case where the power source 3 is unable to supply power to the second load 6 refers to a case where an abnormality such as a ground fault, a short to power, an overvoltage, or a disconnection occurs in the power source 3 or the first wiring 5, preventing the power source 3 from transmitting sufficient power to the second load 6 to drive the second load 6. Whether an abnormality has occurred can be determined from the current flowing through the power source 3 or the first wiring 5, etc. In addition, since the power supply 3 and the first wiring 5 are also used to supply power to the first load 13, if the power supply 3 cannot supply power to the second load 6, the power supply 3 will usually not be able to supply power to the first load 13 either.

[0014] The first switch 7 is a switch that is turned on when the power supply 3 supplies power to the second load 6 and that cuts off conduction when the power supply 3 cannot supply power to the second load 6, and is provided on the first wiring 5 between the power supply 3 and a connection portion (contact 29) with the second wiring 31. In FIG. 1, the first switch 7 is provided between contact 29 and contact 15. As shown in FIG. 1, the first switch 7 can be exemplified by N-channel MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) 27a and 27b. When the sources of the MOSFETs 27a and 27b are connected together as shown in FIG. 1, the rectification directions of the parasitic diodes are opposite to each other, and the conduction can be reliably cut off when the switch is turned off.

[0015] The voltage conversion unit 9 is a device that increases or decreases the voltage of the power supplied from the power source 3, and is provided to connect the second wiring 31 and the storage battery 8. More specifically, the input unit 10 side of the voltage conversion unit 9 is connected to the other end of the second wiring 31, and the output unit 12 side is connected to the storage battery 8 via a fourth wiring 35. The fourth wiring 35 is a wiring that connects the output unit 12 of the voltage conversion unit 9 and the storage battery 8. The voltage conversion unit 9 is, for example, a DC / DC converter, and operates when the vehicle is started. Specifically, when the vehicle is started, the voltage conversion unit 9 increases or decreases the voltage of the power supplied from the power source 3 and supplies it to the storage battery 8, and stops operating when the storage battery 8 has finished charging. Note that the storage battery 8 has finished charging when the remaining battery charge of the storage battery 8 becomes equal to or greater than a predetermined remaining charge threshold. The remaining charge threshold is, for example, the remaining charge when the storage battery is fully charged.

[0016] The second switch 32 is a switch that is turned on when the storage battery 8 supplies power to the second load 6 and is turned off when the storage battery 8 does not supply power, and is connected in parallel to the second wiring 31 and the voltage conversion unit 9. In FIG. 1, the second switch 32 is provided on the third wiring 33. The third wiring 33 is a wiring that connects the contact 29 and the fourth wiring 35, and one end is connected to the contact 29 and the other end is connected to a contact 41 provided on the fourth wiring 35. The contact 41 is also the part where the voltage conversion unit 9 and the fourth wiring 35 are connected. As with the first switch 7, the second switch 32 can be exemplified by N-channel MOSFETs 32a and 32b. As shown in FIG. 1, when the sources of the MOSFETs 32a and 32b are connected to each other, the rectification directions of the parasitic diodes are opposite to each other, and it is possible to reliably turn off the conduction when the switch is turned off.

[0017] The circuit breaker 11 is a means for interrupting current when a ground-fault current flows, and a pair of circuit breakers 11 are provided at the input section 10 and the output section 12 of the voltage conversion section 9. Of the pair of circuit breakers 11, the first circuit breaker 11a (circuit breaker) provided at the output section 12 is a first fuse 37 that cuts off the current by melting when a ground-fault current flows into it. The first fuse 37 can be a known fuse whose cutoff current is equal to or less than the ground-fault current and greater than the current flowing through the output section 12 when power is supplied to the storage battery 8. In this configuration, if a ground fault occurs at the output section 12 of the voltage conversion section 9, a ground-fault current flows from the storage battery 8 to the output section 12 of the voltage conversion section 9. This ground-fault current melts the first fuse 37, protecting the voltage conversion section 9. A ground fault at the output section 12 of the voltage conversion section 9 refers to, for example, a fault in a field-effect transistor (FET) or capacitor within the voltage conversion section 9, which causes the output section 12 to be grounded. In this way, in the power supply system 1, when a ground fault occurs in the output unit 12 of the voltage conversion unit 9, the first fuse 37 melts to cut off the ground-fault current, eliminating the need to provide the output unit 12 with a switch to cut off the ground-fault current or a control circuit to control the switch. Furthermore, a known fuse can be used for the first fuse 37, and a control circuit is not required, making it less expensive than a switch. Furthermore, the first fuse 37 has a simpler structure than a structure that cuts off ground-fault current using a switch and a circuit that controls the switch's operation. Therefore, the power supply system 1 can protect the voltage conversion unit 9 from ground-fault current flowing from the output unit 12 with a cheaper and simpler structure than conventional structures that use a switch and a control circuit to cut off ground-fault current, and can prevent smoke or fire from the voltage conversion unit 9 due to ground-fault current.

[0018] Furthermore, of the pair of circuit breakers 11, the second circuit breaker 11b (circuit breaker) provided in the input unit 10 is a second fuse 39 that melts when a ground-fault current flows in. The second fuse 39 can be a known fuse whose breaking current is equal to or less than the ground-fault current and greater than the current flowing through the input unit 10 when power is supplied to the storage battery 8. In this configuration, if a ground fault occurs in the input unit 10 of the voltage conversion unit 9, a ground-fault current flows from the lead-acid battery 4 to the input unit 10 of the voltage conversion unit 9. This ground-fault current melts the second fuse 39, protecting the voltage conversion unit 9. A ground fault in the input unit 10 occurs, for example, when the input unit 10 is grounded due to a fault such as a short circuit in an FET or capacitor within the voltage conversion unit 9. In this way, the power supply system 1 melts the second fuse 39 to shut off the ground-fault current when a ground fault occurs in the input unit 10 of the voltage conversion unit 9, eliminating the need to provide a switch for shutting off the ground-fault current and a control circuit for controlling the switch in the input unit 10. Therefore, power supply system 1 can protect voltage conversion unit 9 not only from output unit 12 but also from ground fault current flowing from input unit 10 with a configuration that is cheaper and simpler than conventional systems.

[0019] The control unit 43 is a device that controls the connection and disconnection of the first switch 7 and the second switch 32. It is connected to the gates of the MOSFETs 27a and 27b and the MOSFETs 32a and 32b and controls the gate voltage to connect and disconnect the first switch 7 and the second switch 32. The control unit 43 also controls the operation of the voltage conversion unit 9. The control unit 43 is also connected to an ignition (IG) switch 49, which is the vehicle's startup switch, and receives either an ON signal indicating that the startup switch is ON or an OFF signal indicating that the startup switch is OFF. The control unit 43 is also connected to an input device 50. The input device 50 includes a switching device that transmits mode information indicating the vehicle's driving mode to the control unit 43. Examples of vehicle driving modes include an automatic driving mode in which the vehicle is automatically driven and a manual driving mode in which the vehicle is manually driven. Here, manual driving refers to driving in which the control unit 43 controls the vehicle's driving based on the driver's operation. Furthermore, automatic driving refers to driving in which the control unit 43 controls the vehicle's driving regardless of the driver's operation. Furthermore, the input device 50 also includes an acquisition device that acquires the remaining battery capacity of the storage battery 8 and transmits the acquired information to the control unit 43. The above is the description of the configuration of the power supply system 1 according to the first embodiment.

[0020] Next, the operation of power supply system 1 will be described with reference to Figs. 2 to 5. Fig. 2 is a flowchart showing the operation of power supply system 1. Fig. 3 is a diagram showing the operation of power supply system 1 during normal driving. Fig. 4 is a diagram showing the operation of power supply system 1 during evacuation driving. Fig. 5 is a diagram showing a case where a ground fault occurs in input unit 10 and output unit 12 of voltage conversion unit 9. Note that the operation of power supply system 1 described below is the operation when the vehicle is mainly driven autonomously.

[0021] First, when an ON signal is input from the IG switch 49, the control unit 43 refers to the information indicating the remaining battery capacity of the storage battery 8 input from the input device 50, and determines whether the remaining battery capacity of the storage battery 8 is equal to or greater than a predetermined remaining capacity threshold. If it is determined that the remaining capacity is equal to or greater than the remaining capacity threshold, the process proceeds to S2, and if it is determined that the remaining capacity is not equal to or greater than the remaining capacity threshold, the process proceeds to S3 (S1 in FIG. 2).

[0022] If it is determined in S1 that the remaining battery charge of the storage battery 8 is equal to or greater than the remaining charge threshold, the control unit 43 does not supply power to the storage battery 8 and does not charge the storage battery 8 (S2 in FIG. 2). Specifically, the control unit 43 turns on the first switch 7 shown in FIG. 1 to establish conduction, turns off the second switch 32 to interrupt conduction, stops the operation of the voltage conversion unit 9, and proceeds to S4. If it is determined in S1 that the remaining battery charge of the storage battery 8 is not equal to or greater than the remaining charge threshold, the control unit 43 supplies power to the storage battery 8 to charge it, and returns to S1 (S3 in FIG. 2). Specifically, the control unit 43 turns on the first switch 7 to establish conduction, turns off the second switch 32 to interrupt conduction, and operates the voltage conversion unit 9. As a result, as shown by arrow A in Figure 3, power is supplied from the power source 3 to the voltage conversion unit 9 via the first wiring 5, contact 29, and second wiring 31, and the voltage is increased or decreased, and the increased or decreased power is supplied to the storage battery 8 via the fourth wiring 35.

[0023] When S2 is executed, the control unit 43 determines whether the driving mode is the automatic driving mode based on the mode information input from the input device 50. As a result, if it is determined that the driving mode is the automatic driving mode, the process proceeds to S5. If it is determined that the driving mode is not the automatic driving mode (the driving mode is the manual driving mode), the process ends (S4 in FIG. 2). If it is determined that the driving mode is the automatic driving mode in S4, the control unit 43 determines whether power can be supplied from the power source 3 to the first load 13 and the second load 6. As a result, if it is determined that power supply is possible, the process proceeds to S6. If it is determined that power supply is not possible, the process proceeds to S7 (S5 in FIG. 2). If it is determined that power can be supplied from the power source 3 to the first load 13 and the second load 6 in S5, the control unit 43 supplies power from the power source 3 to the first load 13 and the second load 6 and then proceeds to S8 (S6 in FIG. 2). Specifically, the control unit 43 supplies power from the power source 3 to the second load 6 via the first wiring 5, as indicated by arrow B in FIG. 3. At this time, the control unit 43 also supplies power from the power source 3 to the first load 13 via the first wiring 5, the contact 15, and the first branch wiring 17, as indicated by the arrow C in Fig. 3. Note that the vehicle running performed by supplying power to the second load 6 and the first load 13 via the paths indicated by the arrows B and C in Fig. 3 is referred to as normal running.

[0024] When S6 is executed, the control unit 43 determines whether an OFF signal has been input from the IG switch 49, and if it determines that an OFF signal has been input, proceeds to S9, and if it determines that an OFF signal has not been input, returns to S4 (S8 in FIG. 2). If it determines in S8 that an OFF signal has been input, the control unit 43 stops the power supply system 1 and ends operation (S9 in FIG. 2).

[0025] If it is determined in S5 that power cannot be supplied from the power source 3 to the first load 13 and the second load 6, the control unit 43 turns off the first switch 7 to interrupt conduction, turns on the second switch 32 to enable conduction, and proceeds to S10 (S7 in FIG. 2). As a result, the control unit 43 supplies power from the storage battery 8 to the second load 6 via the fourth wiring 35, the third wiring 33, the contact 29, and the connecting wiring 5a of the first wiring 5, as shown by arrow D in FIG. 4. The second load 6, to which power has been supplied, drives the vehicle to a safe location and stops the vehicle upon reaching the safe location. This vehicle travel, which is performed by supplying power via the path shown by arrow D in FIG. 4, is referred to as evacuation travel. Note that even if an OFF signal is input from the IG switch 49 to the control unit 43 during evacuation travel, the control unit 43 does not accept the OFF signal and does not stop the supply of power to the second load 6, as shown in S7 in FIG. 2. This is because if the OFF signal is received and the supply of power to the second load 6 is stopped, the second load 6 will be disconnected from the storage battery 8. When S7 is executed, the control unit 43 determines whether the evacuation traveling has ended. If it is determined that the evacuation traveling has ended, the operation ends. If it is determined that the evacuation traveling has not ended, the process returns to S7 (S10 in FIG. 2). An example of the evacuation traveling ending is when the output voltage of the storage battery 8 reaches a predetermined lower limit voltage, that is, when the storage battery 8 runs out of power. Another example of the evacuation traveling ending is when the control unit 43 receives a signal from the input device 50 indicating that the evacuation traveling has ended. Note that, when the evacuation traveling has ended, the control unit 43 may stop supplying power from the storage battery 8 to the second load 6. Alternatively, the control unit 43 may continue supplying power from the storage battery 8 to the second load 6 even after the evacuation traveling has ended if it is necessary to operate devices constituting the second load 6, such as hazard lights, a horn, and an emergency call, even after the evacuation traveling has ended.

[0026] If the storage battery 8 is electrically connected to the voltage conversion unit 9 and a ground fault occurs at the output unit 12 of the voltage conversion unit 9, a ground-fault current flows from the storage battery 8 toward the output unit 12 of the voltage conversion unit 9, as shown by arrow E in FIG. 5. However, this ground-fault current blows the first fuse 37, thereby protecting the voltage conversion unit 9. Furthermore, when the power supply system 1 turns on the power supply, for example, at time S2 or S3 in FIG. 2, the first switch 7 is ON. Therefore, if a ground fault occurs at the input unit 10 of the voltage conversion unit 9, a ground-fault current flows from the lead-acid battery 4 toward the input unit 10 of the voltage conversion unit 9, as shown by arrow F in FIG. 5. However, this ground-fault current blows the second fuse 39, thereby protecting the voltage conversion unit 9. This completes the description of the operation of the power supply system 1.

[0027] As described above, the power supply system 1 of the first embodiment includes a power supply 3, a storage battery 8, a voltage conversion unit 9, and a pair of circuit breakers 11, and of the pair of circuit breakers 11, the first circuit breaker 11a provided at the output unit 12 of the voltage conversion unit 9 is the first fuse 37. In this configuration, when a ground fault occurs at the output unit 12 of the voltage conversion unit 9, the first fuse 37 is blown by the ground-fault current flowing toward the output unit 12 of the voltage conversion unit 9, thereby protecting the voltage conversion unit 9. Therefore, the power supply system 1 can protect the voltage conversion unit 9 from the ground-fault current with a structure that is less expensive and simpler than conventional structures.

[0028] Furthermore, of the pair of circuit breakers 11 in the power supply system 1 of the first embodiment, the second circuit breaker 11b provided at the input unit 10 of the voltage conversion unit 9 is a second fuse 39 that melts down when a ground-fault current flows in. In this configuration, when a ground fault occurs at the input unit 10 of the voltage conversion unit 9, the second fuse 39 melts down due to the ground-fault current flowing toward the input unit 10 of the voltage conversion unit 9, thereby protecting the voltage conversion unit 9. Therefore, the power supply system 1 can protect the voltage conversion unit 9 not only from the output unit 12 of the voltage conversion unit 9 but also from the ground-fault current flowing from the input unit 10.

[0029] Next, a second embodiment will be described with reference to Fig. 6. In the second embodiment, the second cutoff unit 11b in the first embodiment is replaced with an inrush current prevention circuit. Elements in the second embodiment that perform the same functions as those in the first embodiment are assigned the same numbers, and differences from the first embodiment will be mainly described.

[0030] Fig. 6 is a configuration diagram showing a power supply system according to a second embodiment. As shown in Fig. 6, in a power supply system 1a according to the second embodiment, a second cutoff unit 11b is an inrush current prevention circuit 42 that prevents an inrush current from flowing from the power supply 3 into the voltage conversion unit 9. In this configuration, the inrush current prevention circuit 42 can also prevent an inrush current from flowing into the voltage conversion unit 9 immediately after the power supply 3 is started up.

[0031] The inrush current prevention circuit 42 shown in FIG. 6 includes a series circuit 55 and a resistor 57. The series circuit 55 supplies power from the power source 3 to the voltage conversion unit 9 when there is no possibility of an inrush current flowing, and is provided to connect the second wiring 31 and the input unit 10 of the voltage conversion unit 9. The series circuit 55 shown in FIG. 6 also includes a third fuse 59 and a third switch 61. The third fuse 59 is an element that protects the third switch 61 and the voltage conversion unit 9 from a ground-fault current that flows toward the input unit 10 when a ground fault occurs in the input unit 10 of the voltage conversion unit 9, and is a fuse that melts down due to the ground-fault current. Like the first fuse 37, the third fuse 59 can be a known fuse whose breaking current is equal to or less than the ground-fault current and is greater than the current that flows when power is supplied to the storage battery 8. The third switch 61 is a switch that is turned off when there is a possibility of an inrush current flowing and is turned on when there is no possibility of an inrush current flowing, and is connected in series with the terminal of the third fuse 59 on the voltage conversion unit 9 side. An example of the third switch 61 is a MOSFET. The control unit 43 may control the connection and disconnection of the third switch 61. The resistor 57 is an element through which a current flows immediately after the power supply 3 is started up, and is connected in parallel to the series circuit 55. The resistance value of the resistor 57 is set to a level that allows a desired amount of power to be consumed when a ground fault current or a peak current that occurs immediately after the power supply 3 is started up flows in. The rated power of the resistor 57 is set to a level that allows the resistor 57 to operate with the peak current that flows in immediately after the power supply 3 is started up. Because the current value of the peak current is approximately the same as the current value of the ground fault current, if the rated power is set to a level that allows the resistor 57 to operate with the peak current, the resistor 57 will not burn out even if a ground fault current flows through the resistor 57.

[0032] In the inrush current prevention circuit 42 shown in FIG. 6 , immediately after the power supply 3 is started, the control unit 43 turns off the third switch 61 to interrupt conduction and causes the current supplied from the power supply 3 to flow to the resistor 57, thereby preventing the inrush current from flowing into the voltage conversion unit 9. Furthermore, in the inrush current prevention circuit 42, once a predetermined time has passed since the power supply 3 was started and there is no longer any possibility of an inrush current flowing, the third switch 61 is turned on to allow conduction, causing the current to flow to the voltage conversion unit 9 without passing through the resistor 57, thereby suppressing power loss. Furthermore, if a ground fault occurs at the input unit 10 of the voltage conversion unit 9 while the third switch 61 is turned on, the ground-fault current flowing from the lead-acid battery 4 toward the input unit 10 of the voltage conversion unit 9 melts the third fuse 59, and the ground-fault current flows into the resistor 57, consuming power. Therefore, the inrush current prevention circuit 42 can prevent the ground-fault current from flowing directly into the input unit 10 while suppressing the inrush current from flowing into the voltage conversion unit 9. This concludes the description of the power supply system 1a according to the second embodiment.

[0033] Although the present invention has been described above based on the embodiments, the present invention is not limited to the above embodiments, and modifications may be made without departing from the spirit of the present invention, and other techniques may be appropriately combined to the extent possible. Furthermore, publicly known or well-known techniques may be combined to the extent possible.

[0034] For example, in the second embodiment, a fuse is not connected in series with the resistor 57. However, in order to protect the resistor 57 in the event that a ground fault occurs in the input unit 10, the third switch 61 breaks down and turns OFF, and current continues to flow through the resistor 57, a fuse may be connected in series with the terminal of the resistor 57 on the second wiring 31 side. [Explanation of symbols]

[0035] 1, 1a: Power supply system 3: Power supply 5: 1st wiring 6:Second load (load) 7: First switch 8: Storage battery 9: Voltage conversion section 10: Input section 11: Breaker 11a: First interrupting section (interrupting section) 11b: Second interrupting section (interrupting section) 12: Output section 29: Contact (connection part) 31: 2nd wiring 32: Second switch 37: First fuse 39: Second fuse 42: Inrush current prevention circuit 55: Series circuit 57: Resistance 59: Third fuse 61: Third switch

Claims

1. a power supply system comprising: a power supply that supplies power to a load via a first wiring; a storage battery that stores power supplied from the power supply via a second wiring connected to the first wiring and supplies power to the load when the power supply cannot supply power to the load; a first switch that is provided on the first wiring between a connection portion with the second wiring and the power supply and that is turned on when the power supply supplies power to the load; a voltage conversion portion that is provided to connect the second wiring and the storage battery and that increases or decreases the voltage of the power supplied from the power supply; a second switch that is connected in parallel with the second wiring and the voltage conversion portion and that is turned on when the storage battery supplies power to the load; and a pair of cut-off portions that are provided at an input portion and an output portion of the voltage conversion portion and that cut off current when a ground fault current flows, Of the pair of cutoff units, the first cutoff unit provided in the output unit is a first fuse that cuts off current by melting when a ground fault current flows in. A power supply system characterized by:

2. Of the pair of interrupting units, the second interrupting unit provided in the input unit is a second fuse that melts when a ground fault current flows in.

2. The power supply system according to claim 1 .

3. Of the pair of cutoff units, the second cutoff unit provided in the input unit is an inrush current prevention circuit that prevents an inrush current from flowing from the power supply into the voltage conversion unit.

2. The power supply system according to claim 1 .

4. The inrush current prevention circuit includes: a series circuit including a third fuse that melts down when a ground fault current flows in, and a third switch that is connected in series to a terminal of the third fuse on the side of the voltage conversion unit; a resistor connected in parallel to the series circuit; Equipped with 4. The power supply system according to claim 3.

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