Back-up power supply system and moving body

Abstract

An electricity storage unit (8) has a plurality of cells (81) connected in series. In a non-failure state in which a main power supply (2) is not failed, a charge / discharge unit (7) boosts the power supplied from the main power supply (2) and charges the electricity storage unit (8). An internal power supply (10) supplies power to a control unit (9). An auxiliary power supply path (6) has a first path (6A), a second path (6B), and a switch unit (12). The first path (6A) connects a first connection point (61), which is the connection point on the high potential side of the cell having the highest potential among the plurality of cells (81), and the internal power supply (10). The second path (6B) connects a second connection point (62), which is the connection point between two cells among the plurality of cells (81), and the internal power supply (10). In a failure state, the control unit (9) controls the switching of the switch unit (12) on the basis of a detection voltage detected by a voltage detection unit (11).

Description

Backup power system and mobile

[0001] The present disclosure generally relates to a backup power supply system and a mobile body, and more particularly to a backup power supply system including a power storage unit and a mobile body including the backup power supply system.

[0002] Patent Document 1 discloses a backup device. The backup device in Patent Document 1 includes a power supply unit, a backup circuit, and a power storage unit. The power storage unit serves as a power source when the power supply from the power supply unit is interrupted. The backup circuit includes a first voltage conversion unit, a second voltage conversion unit, and a control unit.

[0003] JP 2019-193493 A

[0004] A backup power supply system according to one aspect of the present disclosure includes a first terminal, a second terminal, a main power supply path, a power storage unit, a charge / discharge unit, a control unit, an internal power supply, a main power supply path, a sub-power supply path, and a voltage detection unit. The first terminal is connected to the main power supply. The second terminal is connected to a load. The main power supply path connects the first terminal and the second terminal. The power storage unit has a plurality of cells connected in series. The charge / discharge unit is connected between the main power supply path and the power storage unit. In a non-failure state in which the main power supply is not faulty, the charge / discharge unit boosts the power supplied from the main power supply to charge the power storage unit. In a failure state in which the main power supply is faulty, the charge / discharge unit receives power from the power storage unit and supplies power to the main power supply path. The control unit controls the charging and discharging operation of the charge / discharge unit. The internal power supply supplies power to the control unit. The main power supply path is a power supply path from the main power supply to the internal power supply. The auxiliary power supply path is a power supply path from the power storage unit to the internal power supply. The voltage detection unit detects the voltage of the auxiliary power supply path. The auxiliary power supply path has a first path, a second path, and a switch unit. The first path connects a first connection point, which is a connection point on the high-potential side of a cell having the highest potential among the plurality of cells, to the internal power supply. The second path connects a second connection point, which is a connection point between two of the plurality of cells, to the internal power supply. The switch unit switches either the first path or the second path to a conductive state. The control unit controls the switching of the switch unit based on the detected voltage detected by the voltage detection unit in the failure state.

[0005] A mobile object according to one aspect of the present disclosure includes the backup power supply system and a mobile object body, the mobile object body carrying the backup power supply system, the main power supply, and the load.

[0006] According to the present disclosure, it is possible to prevent the voltage of the power supplied from the power storage unit to the internal power supply from exceeding the allowable voltage of the internal power supply.

[0007] Fig. 1 is a schematic block diagram showing a backup power supply system according to an embodiment. Fig. 2 is a schematic diagram of a vehicle equipped with the backup power supply system. Fig. 3 is a schematic block diagram showing a backup power supply system according to a first modification. Fig. 4 is a schematic block diagram showing a backup power supply system according to a second modification. Fig. 5 is a schematic block diagram showing a backup power supply system according to a third modification.

[0008] In a backup device (backup power supply system) such as that described in Patent Document 1, when the power supply unit (main power supply) fails, power is supplied from the power storage unit to the control unit via the internal power supply. Depending on the voltage of the power storage unit, there is a possibility that the allowable voltage of the internal power supply will be exceeded.

[0009] The present disclosure has been made in view of the above-mentioned circumstances, and provides a backup power supply system and a mobile body that prevent the voltage of power supplied from a power storage unit to an internal power supply from exceeding the allowable voltage of the internal power supply.

[0010] Preferred embodiments of the present disclosure will be described in detail below with reference to the drawings. Common elements in the embodiments described below are designated by the same reference numerals, and redundant descriptions of the common elements may be omitted. The following embodiments and modifications are merely a portion of various embodiments of the present disclosure. Various modifications of the following embodiments and modifications may be made depending on the design, etc., as long as the object of the present disclosure can be achieved. The configurations of the embodiments and modifications may also be combined as appropriate.

[0011] The drawings described in this disclosure are schematic drawings, and the ratios of the sizes and thicknesses of the components in the drawings do not necessarily reflect the actual dimensional ratios.

[0012] (1) Overview First, an overview of a backup power supply system 1 according to this embodiment will be described with reference to FIG.

[0013] The backup power supply system 1 includes a first terminal 41, a second terminal 42, a main power supply path 4, a storage unit 8, a charge / discharge unit 7, a control unit 9, an internal power supply 10, a main power supply path 5, a secondary power supply path 6, and a voltage detection unit 11.

[0014] The first terminal 41 is connected to the main power supply 2 .

[0015] The second terminal 42 is connected to the load 3 .

[0016] The main power supply path 4 connects the first terminal 41 and the second terminal 42 .

[0017] The power storage unit 8 has a plurality of cells 81 connected in series.

[0018] The charge / discharge unit 7 is connected between the main power supply path 4 and the power storage unit 8. In a normal state where the main power supply 2 is not faulty, the charge / discharge unit 7 boosts the power supplied from the main power supply 2 to charge the power storage unit 8. In a fault state where the main power supply 2 is faulty, the charge / discharge unit 7 receives power from the power storage unit 8 and supplies the power to the main power supply path 4.

[0019] Here, the failure state of the main power supply 2 refers to a state in which the voltage input from the main power supply 2 to the first terminal 41 has dropped below a predetermined threshold due to a malfunction of the main power supply 2, a ground fault in the main power supply 2 or in the circuit connecting the main power supply 2 and the first terminal 41, or the like. The non-failure state of the main power supply 2 refers to a state in which the voltage input from the main power supply 2 to the first terminal 41 is equal to or higher than the threshold. The predetermined threshold is preferably set to a voltage lower than the rated voltage of the main power supply 2, for example, and higher than the minimum guaranteed voltage required for the load 3 to operate normally.

[0020] The internal power supply 10 supplies power to the control unit 9 .

[0021] The main power supply path 5 is a path for supplying power from the main power supply 2 to the internal power supply 10 .

[0022] The auxiliary power supply path 6 is a path for supplying power from the power storage unit 8 to the internal power supply 10. The auxiliary power supply path 6 has a first path 6A, a second path 6B, and a switch unit 12.

[0023] The first path 6A connects the first connection point 61 to the internal power supply 10. The first connection point 61 is a connection point on the high potential side of the cell 81A, which has the highest potential among the multiple cells 81.

[0024] The second path 6B connects the second connection point 62 to the internal power supply 10. The second connection point 62 is a connection point between two of the multiple cells 81 (cell 81B and cell 81C in the example of FIG. 1 ).

[0025] The switch section 12 places either the first path 6A or the second path 6B in a conductive state.

[0026] The voltage detector 11 detects the voltage of the auxiliary power supply path 6 .

[0027] The control unit 9 controls the charging and discharging operation of the charging and discharging unit 7. In addition, the control unit 9 controls the switching of the switch unit 12 based on the voltage detected by the voltage detection unit 11 in a failure state.

[0028] According to the backup power supply system 1 of this embodiment, when the main power supply 2 fails, power can be supplied from the power storage unit 8 to the internal power supply 10 via either the first path 6A or the second path 6B. For example, when the voltage at the first connection point 61 (or the first path 6A) exceeds the allowable voltage of the internal power supply 10, the control unit 9 switches the first path 6A to a cut-off state and the second path 6B to a conduction state. This prevents the voltage of the power supplied from the power storage unit 8 to the internal power supply 10 from exceeding the allowable voltage of the internal power supply 10.

[0029] (2) Details The detailed configuration of the backup power supply system 1 according to this embodiment will be described below with reference to FIGS. 1 and 2. FIG.

[0030] As shown in FIG. 2 , the backup power supply system 1 of this embodiment is mounted on a mobile object such as a vehicle 100. That is, the mobile object (vehicle 100) includes the backup power supply system 1 and a mobile object main body 101 (e.g., the body of the vehicle 100). The mobile object main body 101 is equipped with an ECU (Electronic Control Unit) 102, the backup power supply system 1, a main power supply 2, and a load 3. The backup power supply system 1 supplies power from a power storage unit 8 to the load 3 in a failure state in which the main power supply 2 (e.g., the battery of the vehicle 100) of the vehicle 100 fails. This allows the load 3 to continue operating using the power supply from the power storage unit 8 even in a failure state of the main power supply 2. Note that FIG. 2 is a conceptual diagram illustrating the state in which the backup power supply system 1 is mounted on the vehicle 100 and does not limit the mounting position of the backup power supply system 1. The backup power supply system 1 is generally mounted between the engine compartment and the console box at the front of the vehicle 100, but the mounting position of the backup power supply system 1 can be changed as appropriate.

[0031] In this embodiment, the backup power supply system 1 is mounted on a vehicle 100, but the mobile body is not limited to the vehicle 100 and may be an airplane, a ship, a train, etc. Furthermore, the backup power supply system 1 is not limited to being mounted on a mobile body and may be installed in a facility or the like for use.

[0032] As shown in FIG. 1 , the backup power supply system 1 of this embodiment includes a first terminal 41, a second terminal 42, a main power supply path 4, a main power supply path 5, a sub-power supply path 6, a charge / discharge unit 7, a power storage unit 8, a control unit 9, an internal power supply 10, and a voltage detection unit 11.

[0033] A main power supply 2 such as a battery of the vehicle 100 is connected to the first terminal 41 .

[0034] A load 3 such as an electric brake system is connected to the second terminal 42 .

[0035] The first terminal 41 and the second terminal 42 may be components (terminals) for connecting electric wires, etc., but may also be, for example, leads of electronic components or parts of conductors formed as wiring on a circuit board.

[0036] The main power supply path 4 connects the first terminal 41 and the second terminal 42. The main power supply path 4 is a path for supplying power from the main power supply 2 to the load 3 in a normal state where the main power supply 2 is not faulty.

[0037] The charge / discharge unit 7 is connected (or arranged) between the main power supply path 4 and the power storage unit 8. The charge / discharge unit 7 is, for example, a bidirectional DC-DC converter. The charge / discharge unit 7 has a step-up / step-down circuit including a switching element and the like. When the main power supply 2 is in a normal state, that is, when there is no failure in the main power supply 2, the charge / discharge unit 7 boosts the power supplied from the main power supply 2 to charge the power storage unit 8. For example, in this embodiment, the voltage of the main power supply 2 is 12 V, and the voltage of the power storage unit 8 in a fully charged state is 24 V. Furthermore, when there is a failure in the main power supply 2, the charge / discharge unit 7 receives power from the power storage unit 8 and supplies the power to the main power supply path 4.

[0038] The power storage unit 8 is disposed between the charge / discharge unit 7 and ground. A first end of the power storage unit 8 is connected to a first connection point 61, and a second end of the power storage unit 8 is connected to ground. The first connection point 61 is a connection point between the power storage unit 8 and the charge / discharge unit 7, and also a connection point between the power storage unit 8 and the first path 6A. The power storage unit 8 functions as an auxiliary power supply for supplying power to the load 3 and the internal power supply 10 in a failure state in which the main power supply 2 fails. The power storage unit 8 includes, for example, an electric double layer capacitor (EDLC) capable of rapid charging and discharging. That is, the power storage unit 8 includes an electric double layer capacitor.

[0039] The power storage unit 8 has a plurality of cells 81 (four in the example of FIG. 1 ) connected in series. In this embodiment, the plurality of cells 81 includes cells 81A, 81B, 81C, and 81D. The cells 81A, 81B, 81C, and 81D are connected in series such that they are arranged in the order of cell 81A, cell 81B, cell 81C, and cell 81D from the charging / discharging unit 7 side to the ground side. In other words, the cells 81A, 81B, 81C, and 81D are connected in series such that the potentials of the cells 81A, 81B, 81C, and 81D are higher in this order. In this embodiment, the capacitances of the plurality of cells 81 are equal. In other words, the voltages applied to the plurality of cells 81 are equal.

[0040] In this embodiment, the first connection point 61 is connected to the high-potential terminal of cell 81A, which is the uppermost cell 81 among the multiple cells 81. The second connection point 62 is a connection point between cell 81B and cell 81C. In other words, the first connection point 61 is a connection point that has a higher potential than the second connection point 62. In this embodiment, the first connection point 61 has a higher potential than the second connection point 62 by the voltage of cell 81A and cell 81B. In this embodiment, when the power storage unit 8 is fully charged, the potential of the first connection point 61 is 24 V, and the potential of the second connection point 62 is 12 V.

[0041] The main power supply path 5 is a power supply circuit from the main power supply 2 to the internal power supply 10. In other words, the main power supply path 5 connects the main power supply path 4 and the internal power supply 10. A diode D1 for preventing backflow is arranged in the main power supply path 5. More specifically, the diode D1 is arranged between a connection point 43 and a connection point 51. The connection point 43 is the connection point between the main power supply path 5 and the main power supply path 4. The connection point 51 is the connection point between the main power supply path 5 and the sub-power supply path 6. The cathode of the diode D1 is connected to the connection point 51, and the anode of the diode D1 is connected to the connection point 43.

[0042] The auxiliary power supply path 6 is a path for supplying power from the power storage unit 8 to the internal power supply 10. The auxiliary power supply path 6 connects the power storage unit 8 and the internal power supply 10. The auxiliary power supply path 6 of this embodiment has a first path 6A, a second path 6B, and a switch unit 12.

[0043] The first path 6A connects the first connection point 61 and the internal power supply 10. The first path 6A is a power supply path that has a higher potential than the second path 6B.

[0044] The second path 6B connects the second connection point 62 and the internal power supply 10. The second path 6B is a power supply path that has a lower potential than the first path 6A.

[0045] In this embodiment, the first path 6A and the second path 6B are connected at a connection point 64. The connection point 64 is connected to the connection point 51.

[0046] The switch unit 12 switches either the first path 6A or the second path 6B to a conductive state. The switch unit 12 of this embodiment includes a first switch SW1 and a second switch SW2. The first switch SW1 is disposed on the first path 6A. The first switch SW1 is configured to be switchable between a conductive state and a cut-off state. The second switch SW2 is disposed on the second path 6B. The second switch SW2 is configured to be switchable between a conductive state and a cut-off state. The first switch SW1 and the second switch SW2 may be semiconductor switches such as insulated gate bipolar transistors (IGBTs) and MOSFETs, or thyristors, or may be contacts of a mechanical relay, etc.

[0047] The first switch SW1 is controlled to be in a cut-off state except when it is in a conductive state in response to a control signal S1 input from the control unit 9. The second switch SW2 is controlled to be in a cut-off state except when it is in a conductive state in response to a control signal S2 input from the control unit 9.

[0048] The voltage detection unit 11 detects the voltage of the sub-power supply path 6. In this embodiment, the voltage detection unit 11 detects the voltage of the first path 6A and the voltage of the second path 6B. Here, the voltage of the first path 6A is the voltage between the first path 6A and ground. Also, the voltage of the second path 6B is the voltage between the second path 6B and ground. In this embodiment, the voltage detection point of the first path 6A is between the first switch SW1 and the first connection point 61. Also, the voltage detection point of the second path 6B is between the second switch SW2 and the second connection point 62. The voltage detection unit 11 outputs the detection result to the control unit 9.

[0049] The internal power supply 10 converts the power supplied from the main power supply 2 or the power supplied from the power storage unit 8 into power of a predetermined voltage value (DC voltage) and outputs it to the control unit 9. In the internal power supply 10 of this embodiment, the allowable input voltage is lower than the voltage of the power storage unit 8 in a fully charged state (or the voltage at the first connection point 61). The allowable input voltage of the internal power supply 10 is, for example, 20 V. In the following description, the allowable input voltage of the internal power supply 10 may be simply referred to as the "allowable voltage."

[0050] The control unit 9 is configured, for example, by a microcomputer having a processor and memory. In other words, the control unit 9 is realized by a computer system having a processor and memory. The processor executes an appropriate program, causing the computer system to function as the control unit 9. The program may be pre-recorded in the memory, or may be provided via a telecommunications line such as the Internet, or recorded on a non-transitory recording medium such as a memory card. Note that the control unit is not limited to being realized by a computer system, and may also be realized by an analog circuit, a gate drive circuit, or the like.

[0051] The control unit 9 controls the charge and discharge operations of the charge and discharge unit 7. The control unit 9 compares the main voltage, which is the voltage of the main power supply 2, with a set voltage, and controls the step-up / step-down circuit so that a charging operation is performed if the main voltage is equal to or higher than the set voltage, and a discharging operation is performed if the main voltage is lower than the set voltage. As a result, if the main voltage is equal to or higher than the set voltage, the charge and discharge unit 7 boosts the power supplied from the main power supply 2 to charge the power storage unit 8. On the other hand, if the main voltage is lower than the set voltage, the charge and discharge unit 7 receives power from the power storage unit 8 and supplies the power to the main power supply path 4.

[0052] The control unit 9 of this embodiment also includes a determination unit 91. The determination unit 91 controls the switch unit 12. The determination unit 91 of this embodiment controls the switching of the first switch SW1 by outputting a control signal S1 to the first switch SW1 that controls the switching of the first switch SW1. The determination unit 91 also controls the switching of the second switch SW2 by outputting a control signal S2 to the second switch SW2 that controls the switching of the second switch SW2.

[0053] When the main power supply 2 fails, the determination unit 91 controls switching of either the first switch SW1 or the second switch SW2 to the conductive state based on the detected voltage detected by the voltage detection unit 11. In this embodiment, when the main power supply 2 fails, the determination unit 91 determines whether the voltage of the first path 6A (or the first connection point 61) is equal to or higher than the allowable voltage of the internal power supply 10. If the voltage of the first path 6A is equal to or higher than the allowable voltage of the internal power supply 10, the determination unit 91 turns the first switch SW1 to the non-conductive state and the second switch SW2 to the conductive state. This prevents the voltage of the power supplied from the power storage unit 8 to the internal power supply 10 from exceeding the allowable voltage of the internal power supply 10. On the other hand, if the voltage of the first path 6A is lower than the allowable voltage of the internal power supply 10, the determination unit 91 turns the first switch SW1 to the conductive state and the second switch SW2 to the non-conductive state. This makes it possible to prevent the voltage of the power supplied from the power storage unit 8 to the internal power supply 10 from becoming too low.

[0054] (3) Modifications Modifications of the above embodiment are listed below.

[0055] (3.1) Modification 1 A backup power supply system 1 according to Modification 1 will be described with reference to Fig. 3. In the backup power supply system 1 of Modification 1, the first switch SW1 is a transistor, and the second switch SW2 is a diode.

[0056] The first switch SW1 of the first modification is a transistor such as a MOSFET, etc. The diode D2 connected in antiparallel to the first switch SW1 is a parasitic diode.

[0057] The second switch SW2 of the first modification is a diode such as a Schottky barrier diode. The cathode of the second switch SW2 is connected to the main power supply path 5 (or the connection point 64), and the anode of the second switch SW2 is connected to the second connection point 62.

[0058] In the first modification, the voltage at the second connection point 62 is lower than the allowable voltage of the internal power supply 10 when the power storage unit 8 is fully charged.

[0059] When the main power supply 2 fails and the voltage of the first path 6A is equal to or higher than the allowable voltage of the internal power supply 10, the determination unit 91 turns off the first switch SW1. When the main power supply 2 fails and the first switch SW1 is turned off, the second switch SW2, which is a diode, turns on and power is supplied from the power storage unit 8 to the internal power supply 10 via the second path 6B. This makes it possible to prevent the voltage of the power supplied from the power storage unit 8 to the internal power supply 10 from exceeding the allowable voltage of the internal power supply 10.

[0060] Note that the determination unit 91 turns the first switch SW1 on when the voltage of the first path 6A is lower than the allowable voltage of the internal power supply 10. When the first switch SW1 is on and the failure state occurs, the second switch SW2, which is a diode, turns off and power is supplied from the power storage unit 8 to the internal power supply 10 via the first path 6A. This makes it possible to prevent the voltage of the power supplied from the power storage unit 8 to the internal power supply 10 from becoming too low.

[0061] Furthermore, according to the backup power supply system 1 of the first modification, the control of the second switch SW2 by the determination unit 91 (control unit 9) is not required, and therefore the processing load on the determination unit 91 can be reduced.

[0062] (3.2) Modification 2 A backup power supply system 1 according to Modification 2 will be described with reference to Fig. 4. In the backup power supply system 1 of Modification 2, the first switch SW1 and the second switch SW2 are transistors.

[0063] The first switch SW1 of the second modification is a transistor such as a MOSFET, etc. The diode D2 connected in antiparallel to the first switch SW1 is a parasitic diode.

[0064] The second switch SW2 of the second modification is a transistor such as a MOSFET. The diode D5 connected in antiparallel to the second switch SW2 is a parasitic diode.

[0065] In the backup power supply system 1 of the second modification, the secondary power supply path 6 further includes a first diode D3 and a second diode D4.

[0066] The first diode D3 is disposed in the first path 6A. The first diode D3 is a diode for preventing reverse current. The cathode of the first diode D3 is connected to the first switch SW1, and the anode of the first diode D3 is connected to the first connection point 61. This makes it possible to prevent reverse current from flowing toward the power storage unit 8. The first diode D3 may be disposed between the first switch SW1 and the connection point 64.

[0067] The second diode D4 is disposed in the second path 6B. The second diode D4 is a diode for preventing reverse current. The cathode of the second diode D4 is connected to the second switch SW2, and the anode of the second diode D4 is connected to the second connection point 62. This makes it possible to prevent reverse current from flowing toward the power storage unit 8. The second diode D4 may be disposed between the second switch SW2 and the connection point 64.

[0068] In the second modification, the voltage at the second connection point 62 is equal to or higher than the allowable voltage of the internal power supply 10 when the power storage unit 8 is fully charged.

[0069] When the voltage of the first path 6A is equal to or higher than the allowable voltage of the internal power supply 10 in a state where the main power supply 2 has failed, the determination unit 91 turns the first switch SW1 off and the second switch SW2 on. This causes power to be supplied from the power storage unit 8 to the internal power supply 10 via the second path 6B. This prevents the voltage of the power supplied from the power storage unit 8 to the internal power supply 10 from exceeding the allowable voltage of the internal power supply 10.

[0070] When the voltage of the first path 6A is lower than the allowable voltage of the internal power supply 10, the determination unit 91 turns the first switch SW1 on and turns the second switch SW2 off. This allows power to be supplied from the power storage unit 8 to the internal power supply 10 via the first path 6A. This prevents the voltage of the power supplied from the power storage unit 8 to the internal power supply 10 from becoming too low.

[0071] As described above, in the second modification, when the power storage unit 8 is fully charged, the voltage at the second connection point 62 is equal to or higher than the allowable voltage of the internal power supply 10. Here, when the main power supply 2 fails and the voltage of the second path 6B is equal to or higher than the allowable voltage of the internal power supply 10, the determination unit 91 turns off the first switch SW1 and the second switch SW2. This makes it possible to further prevent the voltage of the power supplied from the power storage unit 8 to the internal power supply 10 from exceeding the allowable voltage of the internal power supply 10.

[0072] When the voltage of the second path 6B is equal to or higher than the allowable voltage of the internal power supply 10, the determination unit 91 may control the second switch SW2 to be in a conductive state for, for example, a predetermined time. This makes it possible to supply power to the load 3 for the predetermined time in a state where the main power supply 2 has failed, while preventing the voltage of the power supplied from the power storage unit 8 to the internal power supply 10 from exceeding the allowable voltage of the internal power supply 10 for more than the predetermined time.

[0073] Furthermore, for example, if the auxiliary power supply path 6 has another voltage supply path with a lower voltage than the second path 6B, the determination unit 91 may turn off the second switch SW2 and turn on the other voltage supply path during the period when the voltage of the second path 6B is equal to or higher than the allowable voltage of the internal power supply 10.

[0074] (3.3) Modification 3 A backup power supply system 1 according to Modification 3 will be described with reference to Fig. 5. In the backup power supply system 1 of Modification 3, the auxiliary power supply path 6 further includes a third path 6C.

[0075] The power storage unit 8 includes two or more cells 81 arranged between the first connection point 61 and the second connection point 62. In the example of Fig. 5, the two or more cells 81 are a cell 81A and a cell 81B.

[0076] The third path 6C connects the third connection point 63 and the internal power supply 10. The third connection point 63 is a connection point between two of the two or more cells 81 (i.e., cell 81A and cell 81B). The third connection point 63 is a connection point that has a lower potential than the first connection point 61 and a higher potential than the second connection point 62. In other words, the third path 6C is a power supply path that has a lower potential than the first path 6A and a higher potential than the second path 6B. Note that, as in the second modification, a diode for preventing backflow may be disposed in each of the first path 6A to the third path 6C.

[0077] In the third modification, the third path 6C and the second path 6B are connected at a connection point 65. The connection point 65 is connected to the connection point 64.

[0078] The switch unit 12 of the third modification performs switching to place any one of the first path 6A, the second path 6B, and the third path 6C in a conductive state. The switch unit 12 of the third modification includes a third switch SW3 in addition to the first switch SW1 and the second switch SW2. The third switch SW3 is arranged on the third path 6C. The third switch SW3 is configured to be able to switch between a conductive state and a cut-off state. The third switch SW3 may be a transistor such as an insulated gate bipolar transistor (IGBT) or a MOSFET, or a semiconductor switch such as a thyristor, or may be the contacts of a mechanical relay, etc.

[0079] The third switch SW3 is controlled to be in a cut-off state except when it is in a conductive state in response to a control signal S3 input from the control unit 9.

[0080] Here, when the main power supply 2 fails, power is supplied from the power storage unit 8 to the internal power supply 10, and as time passes, the voltages at the first connection point 61, the second connection point 62, and the third connection point 63 decrease. When the main power supply 2 fails, the determination unit 91 of the third modification controls the switch unit 12 to switch the second path 6B to a cutoff state and the third path 6C to a conduction state, or to switch the third path 6C to a cutoff state and the first path 6A to a conduction state, in response to a decrease in the detected voltage.

[0081] More specifically, when the main power supply 2 fails, the determination unit 91 controls switching of any one of the first switch SW1, the second switch SW2, and the third switch SW3 to a conductive state based on the detected voltage detected by the voltage detection unit 11. When the main power supply 2 fails, the determination unit 91 brings one of the first to third paths 6A to 6C, whose voltage is the highest and is lower than the allowable voltage of the internal power supply 10, into a conductive state, and brings the other paths into a cut-off state.

[0082] When the second path 6B is in the conductive state, the determination unit 91 determines whether the detected voltage of the third path 6C is equal to or greater than the allowable voltage of the internal power supply 10. If the detected voltage of the third path 6C falls below the allowable voltage over time, the determination unit 91 brings the second path 6B into the interrupted state and the third path 6C into the conductive state.

[0083] When the third path 6C is in the conductive state, the determination unit 91 determines whether the detected voltage of the first path 6A is equal to or greater than the allowable voltage of the internal power supply 10. If the detected voltage of the first path 6A falls below the allowable voltage over time, the determination unit 91 brings the third path 6C into the interrupted state and brings the first path 6A into the conductive state.

[0084] This prevents the voltage of the power supplied from the power storage unit 8 to the internal power supply 10 from exceeding the allowable voltage of the internal power supply 10, while also preventing the voltage of the power supplied to the internal power supply 10 from dropping too low.

[0085] (3.4) Other Modifications In the above embodiment, the case where the power storage unit 8 has four cells 81 has been exemplified. However, the number of cells 81 included in the power storage unit 8 is not limited to four. The power storage unit 8 may have two or three cells 81, or may have five or more cells 81.

[0086] In the above embodiment, the second connection point 62 is the connection point between the cell 81B and the cell 81C. However, the second connection point 62 may be the connection point between the cell 81A and the cell 81B, or the connection point between the cell 81C and the cell 81D. Furthermore, the third connection point 63 in the third modification may be the connection point between two cells 81 arranged between the first connection point 61 and the second connection point 62.

[0087] In the above embodiment, the control unit 9 includes the determination unit 91. However, it is not essential that the control unit 9 includes the determination unit 91. In other words, the control unit 9 that controls the charge / discharge unit 7 and the determination unit 91 (control unit) that controls the switch unit 12 may be separate control units.

[0088] The power storage unit 8 is not limited to an electric double layer capacitor, but may be a secondary battery such as a lithium ion capacitor (LIC). In a lithium ion capacitor, the positive electrode is formed of a material similar to that of an EDLC (e.g., activated carbon), and the negative electrode is formed of a material similar to that of an LIB (e.g., a carbon material such as graphite).

[0089] Furthermore, the power storage unit 8 is not limited to an electric double layer capacitor, and may be, for example, an electrochemical device having the configuration described below. The electrochemical device here includes a positive electrode member, a negative electrode member, and a nonaqueous electrolyte. The positive electrode member includes a positive electrode current collector and a positive electrode material layer supported on the positive electrode current collector and containing a positive electrode active material. The positive electrode material layer includes a conductive polymer as a positive electrode active material that dopes and dedopes anions (dopants). The negative electrode member includes a negative electrode material layer containing a negative electrode active material. The negative electrode active material is, for example, a substance that undergoes an oxidation-reduction reaction involving the absorption and desorption of lithium ions, specifically, a carbon material, a metal compound, an alloy, or a ceramic material. The nonaqueous electrolyte, for example, has lithium ion conductivity. This type of nonaqueous electrolyte includes a lithium salt and a nonaqueous solution that dissolves the lithium salt. An electrochemical device configured in this manner has a higher energy density than an electric double layer capacitor or the like.

[0090] (Summary) As is clear from the above-described embodiment and modified examples, the backup power supply system (1) according to the first aspect includes a first terminal (41), a second terminal (42), a main power supply path (4), a power storage unit (8), a charge / discharge unit (7), a control unit (9), an internal power supply (10), a main power supply path (5), a secondary power supply path (6), and a voltage detection unit (11). The first terminal (41) is connected to the main power supply (2). The second terminal (42) is connected to the load (3). The main power supply path (4) connects the first terminal (41) and the second terminal (42). The power storage unit (8) has a plurality of cells (81) connected in series. The charge / discharge unit (7) is connected between the main power supply path (4) and the power storage unit (8). The charging / discharging unit (7) charges the storage unit (8) by boosting the power supplied from the main power supply (2) when the main power supply (2) is in a normal state. When the main power supply (2) is in a failure state, the charging / discharging unit (7) receives power from the storage unit (8) and supplies the power to the main power supply path (4). The control unit (9) controls the charging / discharging operation of the charging / discharging unit (7). The internal power supply (10) supplies power to the control unit (9). The main power supply path (5) is a power supply path from the main power supply (2) to the internal power supply (10). The auxiliary power supply path (6) is a power supply path from the storage unit (8) to the internal power supply (10). The voltage detection unit (11) detects the voltage of the auxiliary power supply path (6). The auxiliary power supply path (6) has a first path (6A), a second path (6B), and a switch unit (12). The first path (6A) connects a first connection point (61), which is a connection point on the high-potential side of the cell (81) having the highest potential among the plurality of cells (81), to the internal power supply (10). The second path (6B) connects a second connection point (62), which is a connection point between two of the plurality of cells (81), to the internal power supply (10). The switch unit (12) switches either the first path (6A) or the second path (6B) to a conductive state. The control unit (9) controls the switching of the switch unit (12) based on the detected voltage detected by the voltage detection unit (11) in a failure state.

[0091] According to this aspect, it is possible to prevent the voltage of the power supplied from the power storage unit (8) to the internal power supply (10) from exceeding the allowable voltage of the internal power supply (10).

[0092] In the backup power supply system (1) according to the second aspect, in the first aspect, the switch section (12) has a first switch (SW1) and a second switch (SW2). The first switch (SW1) is arranged on the first path (6A). The second switch (SW2) is arranged on the second path (6B).

[0093] In the backup power supply system (1) according to the third aspect, in the second aspect, the first switch (SW1) is a transistor, the second switch (SW2) is a diode, and the voltage at the second connection point (62) is less than the allowable voltage of the internal power supply (10) when the power storage unit (8) is fully charged.

[0094] According to this aspect, the control of the second switch (SW2) by the control unit (9) is not required, and therefore the processing load on the control unit (9) can be reduced.

[0095] In the backup power supply system (1) according to the fourth aspect, the first switch (SW1) and the second switch (SW2) are transistors in the second aspect, and the voltage at the second connection point (62) is equal to or higher than the allowable voltage of the internal power supply (10) when the power storage unit (8) is fully charged.

[0096] According to this aspect, it is possible to further prevent the voltage of the power supplied from the power storage unit (8) to the internal power supply (10) from exceeding the allowable voltage of the internal power supply (10).

[0097] In a backup power supply system (1) according to a fifth aspect, the auxiliary power supply path (6) in the third aspect further includes a diode (first diode D3) arranged in the first path (6A).

[0098] According to this aspect, it is possible to prevent a reverse current from flowing to the electricity storage unit (8).

[0099] In a backup power supply system (1) according to a sixth aspect, in the fourth aspect, the auxiliary power supply path (6) further includes a first diode (D3) and a second diode (D4). The first diode (D3) is arranged in the first path (6A). The second diode (D4) is arranged in the second path (6B).

[0100] According to this aspect, it is possible to prevent a reverse current from flowing to the electricity storage unit (8).

[0101] In a backup power supply system (1) according to a seventh aspect, in any one of the first to sixth aspects, the plurality of cells (81) includes two or more cells (81) arranged between a first connection point (61) and a second connection point (62). The auxiliary power supply path (6) further has a third path (6C) connecting a third connection point (63) and an internal power supply (10). The third connection point (63) is a connection point between two of the two or more cells (81). The switch unit (12) switches any one of the first path (6A), the second path (6B), and the third path (6C) to a conductive state. In a fault state, the control unit (9) controls the switch unit (12) to switch between a disconnected state for the second path (6B) and a conductive state for the third path (6C), or to switch between a disconnected state for the third path (6C) and a conductive state for the first path (6A), depending on a drop in the detected voltage.

[0102] According to this aspect, it is possible to prevent the voltage of the power supplied from the storage unit (8) to the internal power supply (10) from exceeding the allowable voltage of the internal power supply (10), while also preventing the voltage of the power supplied to the internal power supply (10) from dropping too low.

[0103] The configurations other than the first aspect are not essential for the backup power supply system (1) and can be omitted as appropriate.

[0104] A mobile body (vehicle 100) according to an eighth aspect includes the backup power supply system (1) according to any one of the first to seventh aspects and a mobile body (101). The mobile body (101) is equipped with the backup power supply system (1), a main power supply (2), and a load (3).

[0105] According to this aspect, it is possible to prevent the voltage of the power supplied from the power storage unit (8) to the internal power supply (10) from exceeding the allowable voltage of the internal power supply (10).

[0106] REFERENCE SIGNS LIST 1 Backup power supply system 2 Main power supply 3 Load 4 Main power supply path 41 First terminal 42 Second terminal 5 Main power supply path 6 Sub-power supply path 61 First connection point 62 Second connection point 63 Third connection point 6A First path 6B Second path 6C Third path 7 Charging / discharging section 8 Power storage section 81 Cell 9 Control section 10 Internal power supply 11 Voltage detection section 12 Switch section 100 Vehicle (mobile body) 101 Mobile body D3 First diode D4 Second diode SW1 First switch SW2 Second switch

Claims

a charge / discharge unit connected between the main power supply path and the power storage unit, for charging the power storage unit by boosting the power supplied from the main power supply in a normal state where the main power supply is not faulty, and for supplying power to the main power supply path from the power storage unit in a fault state where the main power supply is faulty; a control unit for controlling the charge / discharge operation of the charge / discharge unit; an internal power supply for supplying power to the control unit; a main power supply path which is a power supply path from the main power supply to the internal power supply; a sub-power supply path which is a power supply path from the power storage unit to the internal power supply; and a voltage detection unit for detecting a voltage of the sub-power supply path, wherein the sub-power supply path comprises: a first path connecting a first connection point which is a connection point on the high potential side of a cell having the highest potential among the plurality of cells to the internal power supply; a second path connecting a second connection point, which is a connection point between two cells of the plurality of cells, and the internal power supply; and a switch unit that switches either the first path or the second path to a conductive state, wherein the control unit controls the switching of the switch unit based on a detected voltage detected by the voltage detection unit in the failure state.

2. The backup power supply system according to claim 1, wherein the switch section comprises: a first switch arranged in the first path; and a second switch arranged in the second path.

3. The backup power supply system according to claim 2, wherein the first switch is a transistor, the second switch is a diode, and the voltage at the second connection point is less than the allowable voltage of the internal power supply when the storage unit is fully charged.

4. The backup power supply system according to claim 2, wherein the first switch and the second switch are transistors, and the voltage at the second connection point is equal to or greater than the allowable voltage of the internal power supply when the power storage unit is fully charged.

5. The backup power system according to claim 3, wherein the auxiliary power supply path further includes a diode disposed in the first path.

6. The backup power supply system according to claim 4, wherein the auxiliary power supply path further includes: a first diode disposed in the first path; and a second diode disposed in the second path.

7. The backup power supply system of claim 1, wherein the plurality of cells includes two or more cells arranged between the first connection point and the second connection point, the auxiliary power supply path further has a third path connecting a third connection point that is a connection point between two of the two or more cells and the internal power supply, the switch unit switches any one of the first path, the second path, and the third path to a conductive state, and the control unit controls the switch unit to switch the second path to a cutoff state and the third path to a conductive state, or to switch the third path to a cutoff state and the first path to a conductive state, in accordance with a drop in the detected voltage, in the failure state.

8. A mobile body comprising: the backup power supply system according to claim 1; and a mobile body body carrying said backup power supply system, said main power supply, and a load.

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