JP2013233007A - Battery charger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery charger capable of suppressing a decrease in a supply current into a load.SOLUTION: The battery charger includes: a feeding bus bar 11 connected between a load 20 and a battery 30; noise extracting means for extracting AC noise which is generated at the load 20 and runs through the feeding bus bar 11; and charging means for charging the battery 30 by AC noise.

Description

  The present invention relates to a battery charging device.

  A plurality of unit cells are connected in series, the output voltage of these unit cells is used as an input, and an ON / OFF type converter circuit is connected in which the output is connected in the direction of charging each unit cell. There is known a battery pack provided with a current control circuit that increases or decreases the primary current accordingly (Patent Document 1).

JP-A-11-176483

  However, since the current from a plurality of unit cells branches to the load current and the primary side current for charging the unit cells, the load current is greatly reduced when the branched primary side current is large. was there.

  The problem to be solved by the present invention is to provide a battery charger that suppresses a decrease in current supplied to a load.

  The present invention solves the above problem by including noise extraction means for extracting AC noise generated on the power supply bus and charging means for charging the battery with AC noise.

  According to the present invention, unnecessary AC noise is used for charging the battery, so that a decrease in current from the battery to the load can be prevented when the battery is charged.

1 is a circuit diagram of a battery charging device, a load, and a battery according to an embodiment of the present invention. FIG. 6 is a circuit diagram of a battery charging device, a load, and a battery according to another embodiment of the present invention. FIG. 6 is a circuit diagram of a battery charging device, a load, and a battery according to another embodiment of the present invention. FIG. 6 is a circuit diagram of a battery charging device, a load, and a battery according to another embodiment of the present invention. It is a circuit diagram of a battery charging device, a load and a battery according to a modification of the present invention. FIG. 6 is a circuit diagram of a battery charging device, a load, and a battery according to another embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<< First Embodiment >>
FIG. 1 is a circuit diagram of a battery charger according to an embodiment of the invention. The battery charging device of the present invention is a control device that is mounted on a vehicle such as an electric vehicle, for example, and charges a battery that is a power source of the vehicle. Further, the battery charging device 10 is connected between the battery 30 and a load 20 driven by the power of the battery 30. Hereinafter, the case where the battery charging device is mounted on a vehicle will be described. However, the battery charging device of the present example is not necessarily limited to the vehicle, but is a device other than the vehicle, such as a home power storage device. May be.

  The battery charging device 10 of this example is a charging device that charges the battery 30, and is electrically connected between the load 20 and the battery 30. The load 20 is a switching load including a switching element such as an inverter. The load 20 is supplied with power from the battery 30. The inverter included in the load 20 switches the switching element on and off by a control signal from a controller (not shown), converts power from the battery 30, and supplies power to a load (not shown). Further, when the switching element is switched on and off, AC noise is generated. Therefore, the load 20 is also a source of AC noise.

  The battery 30 is a chargeable / dischargeable battery configured by connecting a plurality of secondary batteries such as lithium ion batteries in series or in parallel. The battery 30 is a power source for driving the vehicle.

  The battery charging apparatus 10 includes a power supply bus 11, a capacitor 12, and a charging circuit 13. The power supply bus 11 is a pair of power lines connected to both electrodes of the battery 30. The power supply bus 11 is connected to the load 20 and the battery 30 in order to supply power from the battery 30 to the load 20, and AC noise generated in the load 20 flows through the power supply bus 11. The capacitor 12 is connected to the power supply bus 11 between the load 20 and the charging circuit 13. The capacitor 12 is connected in series with the load 20 in order to extract AC noise generated in the load 20 and flowing through the power supply bus 11. The frequency of AC noise generated in the load 20 is determined in advance by the drive frequency of the switching element of the load 20 or the like. And in order to extract alternating current noise with the capacitor | condenser 12, the capacitance of the capacitor | condenser 12 is set so that the alternating current component of the frequency of alternating current noise may be passed.

  The charging circuit 13 is a charging circuit for charging the battery 30 with the power of AC noise generated in the load 20, and includes a diode bridge 131 and a smoothing circuit 132. The diode bridge 131 is a bridge circuit in which four diodes are connected on the bridge, and the power supply bus 11 is connected to each connection point of the four diodes. The diode bridge 131 is connected to the load 20 side in the charging circuit 13. The diode bridge 131 is a conversion circuit that converts AC noise into DC.

  The smoothing circuit 132 is a filter circuit that rectifies the direct current converted by the diode bridge 131, and includes a coil 132a and a capacitor 132b. The coil 132 a is connected to the positive power supply line of the power supply bus 11, and the capacitor 132 b is connected between a pair of power supply lines that are the power supply bus 11. The smoothing circuit 132 is connected to the battery 30 side in the charging circuit 13. The diode bridge 131 and the smoothing circuit 132 are designed to convert the AC noise extracted by the capacitor 12 into DC power suitable for charging the battery 30.

  Next, charging control by the battery charging device 10 of FIG. 1 will be described. First, when AC noise is generated by the switching operation of the switching element included in the load 20, the AC noise flows through the power supply bus 11 and is extracted by the capacitor 12. The extracted AC noise is converted into DC power for charging the battery 30 by the diode bridge 131. The DC power converted by the diode bridge 131 is smoothed by the smoothing circuit 132 and supplied to the battery 30. Thereby, the battery 30 is charged.

  As described above, this example includes the capacitor 12 that extracts the AC noise generated by the load 20 and flows through the power supply bus 11, and the charging circuit 13 that charges the battery by the AC noise. Thereby, AC noise that is unnecessary as it may affect other electronic devices and the like can be used for charging the battery 30. As a result, the battery 30 can be charged while suppressing a decrease in the current supplied from the battery 30 to the load 20.

  In this example, the capacitor 12 is connected between the load 20 and the charging circuit 13. Thus, by setting the capacitance of the capacitor 12 so as to extract AC noise, the battery 30 can be charged by AC noise while preventing power other than AC noise used by the load 20 from being insufficient. it can.

  In this example, the charging circuit 13 includes a diode bridge 131 that converts AC noise into the charging power of the battery 30 and a smoothing circuit 132 that smoothes the charging power. Thereby, AC noise can be converted into electric power suitable for charging the battery 30.

  In this example, the capacitor 12 is used to extract AC noise, but a circuit element other than the capacitor 12 is connected to the power supply bus 11 between the load 20 and the charging circuit 13 to reduce AC noise. It may be extracted. In this example, the diode bridge 131 is used to convert AC noise into the charging power of the battery 30, but an AC-DC conversion circuit other than the diode bridge 131 may be used.

  The capacitor 11 corresponds to “noise extraction means” or “first capacitor” of the present invention, the charging circuit 30 corresponds to “charging means” of the present invention, and the diode bridge 131 corresponds to “power conversion circuit”.

<< Second Embodiment >>
FIG. 2 is a circuit diagram of a battery charger according to another embodiment of the invention. This example differs from the first embodiment described above in that a transformer 14 is provided. Since the configuration other than this is the same as that of the first embodiment described above, the description thereof is incorporated as appropriate.

  As shown in FIG. 2, the battery charging device 10 includes a power supply bus 11, a capacitor 12, a charging circuit 13, and a transformer 14. The transformer 14 is an amplifier circuit for amplifying AC noise, and is connected between the capacitor 12 and the charging circuit 13. A primary transformer 141 of the transformer 14 is connected to the load 20 side, and is connected between a pair of power sources of the power supply bus 11. The secondary transformer 142 of the transformer 14 is connected to the battery 30 side, and is connected between a pair of power sources of the power supply bus 11. The winding ratio of the transformer 14 is set according to the amplification factor that amplifies the AC noise and becomes power suitable for charging the battery 30.

  As described above, in the present invention, the transformer 14 that amplifies AC noise is connected between the capacitor 12 and the charging circuit 13. Thus, according to the present invention, AC noise can be amplified in accordance with the winding ratio of the transformer 14, so that the charging power of the battery 30 can be increased.

  In this example, the transformer 14 is used to amplify AC noise, but an amplifier circuit other than the transformer may be used.

  The transformer 14 corresponds to the “amplifying means” of the present invention.

<< Third Embodiment >>
FIG. 3 is a circuit diagram of a battery charger according to another embodiment of the invention. This example is mainly different from the first embodiment described above in that the switch unit 15 is provided. The other configuration is the same as that of the first embodiment described above, and the description of the first or second embodiment is incorporated as appropriate.

  The battery 30 includes a plurality of batteries in which n (n = 1 or more natural numbers) secondary batteries (BA) are connected in series. In FIG. 3, for ease of explanation, each secondary battery (BA) is illustrated as not connected, but in the actual battery 30, each secondary battery (BA) is It is connected. In addition, n charging circuits 13 and n transformers 14 are provided so as to correspond to a plurality of secondary batteries (BA) constituting the battery 30. The secondary-side transformer 142 of the n transformers 14 is connected to the power supply bus 11 and the charging circuit 13 which are a pair of power supply lines, and n secondary batteries (BA) are connected between each pair of power supply lines. ) Are connected to each other.

  The primary side of the n number of transformers 14 is connected to the first-stage primary-side transformer 141 and the second-stage primary-side transformer 141, and the second-stage primary-side transformer 141 and the third-stage transformer are connected to the primary-side transformer 141. The primary side transformer 141 is connected, and the (n-1) th stage primary side transformer 141 and the nth stage primary side transformer 141 are sequentially connected. The high-potential-side terminal of the first-stage primary transformer 141 is connected to the load 20 via the capacitor 12, and the low-potential-side terminal of the n-stage primary-side transformer 141 is connected to the load 20. Has been.

  The switch unit 15 is a part of a charging circuit by the battery charging device, and has 2n pairs of switches (SW). Each switch (SW) constituting the switch unit 15 is connected between the secondary transformer 142 of each transformer 14 and the diode bridge 131 of each charging circuit 13. In the switch unit 15, the first-stage switches (SW1, SW2) are connected to the pair of power supply lines of the first-stage power supply bus 11, respectively, and the second-stage switches (SW3, SW4) are connected to the second-stage power line 11. The n-th stage switches (SW2n-1) and SW (2n)) are connected to the n-th stage power supply bus 11 respectively.

  That is, the first stage switches (SW1, SW2) are connected to correspond to the first stage secondary battery (BA1), and the second stage switches (SW3, SW4) are connected to the second stage secondary battery (BA2). ) And the n-th stage switches (SW (2n−1), SW (2n)) are connected to the n-th stage secondary battery (BAn). Thereby, each switch (SW) constituting the switch unit 15 is connected so as to correspond to each secondary battery (BA) of the battery 30. Similarly, each charging circuit 13 and transformer 14 are connected so as to correspond to each secondary battery (BA).

  The controller 19 is a control unit that controls the charging of the battery 30 while managing the charging state of the battery 30 by a sensor (not shown) connected to each battery of the battery 30. Further, the controller 19 switches each switch (SW1, SW2,..., SW (2n-1), SW (2n)) of the switch unit 15 on and off, so that each secondary battery (BA) of the battery 30 is switched. ) Control charging.

  When the secondary battery (BAn) of the nth stage among the secondary batteries (BA) of the battery 30 is charged with AC noise, the nth stage of the switches (SW) of the switch unit 15 is charged. The switches (SW (2n-1), SW (2n)) connected corresponding to the secondary battery (BAn) are turned on, and the other switches (SW1, SW2,..., SW (2n-3)) , SW (2n-2)) is turned off. In addition, when the n-2 stage secondary battery (BA (n-2)) and the n stage secondary battery (BAn) are charged by AC noise, each switch (SW) of the switch unit 15 is used. Among them, the switches (SW (2n-5), SW (2n-4)) connected to the n-2 stage secondary battery (BA (n-2)) are turned on, and the n stage Switch (SW (2n-1), SW (2n)) connected corresponding to the secondary battery (BAn) of the other switch (SW1, SW2,..., SW (2n-7) ), SW (2n-6), SW (2n-3), SW (2n-2)) are turned off.

  Thus, the controller 19 turns on the switch (SW) corresponding to the secondary battery (BA) to be charged among the secondary batteries (BA) of the battery 30 and turns on the other switches (SW). By turning off, the secondary battery (BA) to be charged is electrically connected to the charging circuit 13 and the secondary transformer 142 corresponding to the secondary battery (BA) to be charged, and becomes the target to be charged. The secondary battery (BA) that is not charged and the secondary battery (BA) that is not the object of charging are disconnected from the charging circuit 13 and the secondary-side transformer 142.

  As the battery 30 is used, the capacity of each secondary battery varies. The controller 19 identifies the secondary battery with the smallest capacity among the plurality of secondary batteries, turns on the corresponding switch (SW), and turns off the non-corresponding switch (SW) with the secondary battery as a charging target. Then, the secondary battery with the smallest capacity is charged. Thereby, the dispersion | variation in the capacity | capacitance of each secondary battery is eliminated.

  Next, control of capacity adjustment of the battery 30 by the controller 19 will be described. The controller 19 detects the state of charge (SOC) of each secondary battery (BA) from a voltage sensor (not shown) connected to each secondary battery (BA). The controller 19 compares the state of charge of each secondary battery (BA), identifies the secondary battery with the highest SOC among the secondary batteries (BA), and the secondary battery (BA) with the highest SOC. The difference in SOC with other secondary batteries is calculated.

  The controller 19 compares the calculated SOC difference with a preset determination threshold. The determination threshold value is a threshold value defined by the SOC, and is set in advance to determine the variation of each secondary battery. Then, the controller 19 specifies a secondary battery whose SOC is higher than the determination threshold value as a battery with a large variation, and sets it as a target battery for capacity adjustment.

  When the secondary battery subject to capacity adjustment is identified, the controller 19 turns on the switch (SW) connected corresponding to the secondary battery (BA) subject to capacity adjustment, and causes AC noise to occur. The secondary battery to be adjusted is charged. The controller 19 manages the SOC of the secondary battery to be adjusted during capacity adjustment (during charge control). When the SOC of the secondary battery to be adjusted reaches the highest SOC among the secondary batteries (BA), the controller 19 turns off the switch (SW) that is in the on state and ends the capacity adjustment. In addition, when there is another battery whose capacity is to be adjusted, the secondary battery (BA) is charged with AC noise in the same manner as described above, and the capacity is adjusted. Accordingly, in this example, the capacity of the secondary battery (BA) included in the battery 30 is adjusted using AC noise, and variations between the secondary batteries (BA) are suppressed.

  As described above, this example includes a plurality of switches (SW) connected to a plurality of secondary batteries (BA), respectively. Thus, by controlling on / off of the switch, charging power due to AC noise is supplied to a specific secondary battery (BA) among a plurality of secondary batteries (BA), and other secondary batteries (BA) Since it is possible to control the battery (BA) so as not to supply charging power due to AC noise, capacity adjustment using AC noise can be performed.

  In this example, the switch (SW) corresponding to the secondary battery (BA) to be charged is turned on, the switch (SW) not corresponding is turned off, the secondary battery (BA) is charged, and the capacity adjustment is performed. Do. Thereby, since capacity adjustment can be performed without discharging a secondary battery having a high voltage, heat generation from the battery 30 during capacity adjustment can be suppressed.

  Note that the capacity adjustment control method of this example is not limited to the above, and other methods may be used.

  The charging circuit 13 and the switch unit 15 described above correspond to the “charging unit” of the present invention.

<< 4th Embodiment >>
FIG. 4 is a circuit diagram of a battery charger according to another embodiment of the invention. This example is different from the third embodiment described above in that the transformer 14 and the charging circuit 13 are combined into one, and the switch unit 16 is provided instead of the switch unit 15. Other configurations are the same as those of the third embodiment described above, and the descriptions of the first to third embodiments are incorporated as appropriate.

  The battery charging device 10 includes a switch unit 16 in addition to the power supply bus 11, the capacitor 12, the charging circuit 13, the transformer 14, and the controller 19. The power supply bus 11 includes a pair of power lines connected to both electrodes of the battery 11. Of the pair of power supplies, the power supply line on the positive electrode side is branched into a plurality of wires and connected to the positive electrode side of each secondary battery. In addition, among the pair of power supplies, the power supply line on the negative electrode side is branched into a plurality of wirings and connected to the negative electrode side of each secondary battery. The switch part 16 is a part of the charging circuit by the battery charging device, and has 2n pairs of switches (SW). Each switch (SW) constituting the switch unit 16 is connected between the charging circuit 13 and each secondary battery (BA) constituting the battery 30.

  That is, the first stage switches (SW1, SW2) are connected to correspond to the first stage secondary battery (BA1), and the second stage switches (SW3, SW4) are connected to the second stage secondary battery (BA2). ) And the n-th stage switches (SW (2n−1), SW (2n)) are connected to the n-th stage secondary battery (BAn). Thereby, each switch (SW) constituting the switch unit 15 is connected so as to correspond to each secondary battery (BA) of the battery 30.

  Of the switches (extraordinary switches) in each set, the upper switches (SW1, SW3, SW5,... SW2n-1) are the positive-side power supply bus 11 and the positive-side terminal of each secondary battery. The lower switches (SW2, SW4, SW6... SW2n) are respectively connected between the negative power supply bus 11 and the negative terminal of each secondary battery. .

The controller 19 switches each switch (SW1, SW2,..., SW (2n-1), SW (2n)) of the switch unit 15 on and off, so that each secondary battery (BA) of the battery 30 is switched. Control the charging.

  As described above, this example includes a plurality of switches (SW) connected to a plurality of secondary batteries (BA), respectively. Thus, by controlling on / off of the switch, charging power due to AC noise is supplied to a specific secondary battery (BA) among a plurality of secondary batteries (BA), and other secondary batteries (BA) Since it is possible to control the battery (BA) so as not to supply charging power due to AC noise, capacity adjustment using AC noise can be performed.

  Further, in this example, from the output side of the charging circuit 13, the power supply bus 11 is branched and connected to each secondary battery (BA) of the battery 30, and a switch (SW) is connected to each branched wiring. Each switch (SW) is connected corresponding to a plurality of secondary batteries. Thereby, the number of charging circuits 13 and transformers 14 can be reduced.

  In addition, the battery charging apparatus 10 of this example may be configured by a circuit illustrated in FIG. FIG. 5 is a circuit diagram of a battery charger according to a modification of the present invention. In the battery charging device shown in the modification, the switch unit 15 is connected between each transformer 14 and the charging circuit 13 with respect to the battery charging device according to the third embodiment, and each charging circuit 13 and each secondary battery ( Each switch (SW) of the switch unit 16 is connected to (BA). Thereby, each switch (SW) of switch part 15 and 16 is connected corresponding to a plurality of secondary batteries (BA), respectively.

  The charging circuit 13 and the switch parts 15 and 16 correspond to the “charging means” of the present invention.

<< 5th Embodiment >>
FIG. 6 is a circuit diagram of a battery charger according to another embodiment of the invention. In the present example, the smoothing circuit 132 is omitted, the switch unit 17 and the capacitor 18 are provided, and the connection position of the switch unit 15 is different from the third embodiment described above. The other configuration is the same as that of the third embodiment described above, and the description of the first to fourth embodiments is incorporated as appropriate.

  A plurality of capacitors 18 are provided so as to correspond to each secondary battery (BA) of the battery 30. The plurality of capacitors 18 are respectively connected between a pair of power supply lines of the power supply bus 11 connected to each secondary battery (BA). In other words, one end of the capacitor 18 is connected to one wiring of the pair of power supply lines, and the other end is connected to the other wiring of the pair of power supply lines.

  The switch unit 15 is a part of a charging circuit by the battery charging device, and has 2n pairs of switches (SW). Each switch (SW) constituting the switch unit 15 is connected between the diode bridge 131 and the capacitor 18 of each charging circuit 13. In the switch unit 15, the first-stage switches (SW1, SW2) are connected to the pair of power supply lines of the first-stage power supply bus 11, respectively, and the second-stage switches (SW5, SW6) are connected to the second-stage power supply bus 11. The n-th stage switches (SW (4n-3) and SW (4n-2)) are connected to the pair of power supply lines of the power feeding bus 11, respectively, and are connected to the n-th stage power feeding bus 11, respectively.

  The switch unit 17 is a part of a charging circuit by the battery charging device, and has 2n pairs of switches (SW). Each switch (SW) constituting the switch unit 17 is connected between each capacitor 18 and each secondary battery (BA). In the switch unit 17, the first-stage switches (SW3, SW4) are connected to a pair of power supply lines of the first-stage power supply bus 11, respectively, and the second-stage switches (SW7, SW8) are connected to the second-stage power supply line 11. The n-th stage switches (SW (4n−1), SW (4n)) are respectively connected to the n-th stage power supply buses 11.

  That is, the first-stage switch (SW1 to SW4) and the capacitor 18 are connected to correspond to the first-stage secondary battery (BA1), and the second-stage switch (SW5 to 8) and the capacitor 18 are connected to the second stage. The nth stage switches (SW4n-3 to SW4n) and the capacitor 18 are connected to the nth stage secondary battery (BAn). Thereby, each switch (SW) which comprises a capacitor | condenser and the switch parts 15 and 17 is connected so that it may correspond to each secondary battery (BA) of the battery 30. FIG.

  The controller 19 manages the charging state of the battery 30 with sensors (not shown) connected to the respective secondary batteries of the battery 30, while the switches (SW1, SW2,... The charging of each secondary battery (BA) of the battery 30 is controlled by switching on and off of the SW (4n-1) and SW (4n).

  In the case where the secondary battery (BAn) of the n-th stage among the secondary batteries (BA) of the battery 30 is charged by AC noise, the controller 19 includes the switches (SW) of the switch unit 15. The switches (SW (4n-3), SW (4n-2)) connected to the n-th stage secondary battery (BAn) are turned on, and n of the switches (SW) of the switch unit 17 is n. The switches (SW (4n-1), SW (4n)) connected corresponding to the secondary battery (BAn) at the stage are turned off. In addition, the controller 100 turns off the switch that is not connected to the secondary battery (BAn).

  The AC noise extracted by the capacitor 12 is amplified by the n-th transformer, converted to DC power by the diode bridge 131, and passed through the n-th switch (SW4n-3, SW4n-2) of the switch unit 15. And supplied to the capacitor 18. Thereby, the capacitor | condenser 18 is charged with the electric power converted from alternating current noise.

  The controller 19 manages the voltage of the capacitor 18 by a sensor (not shown) connected to the capacitor 18. When the controller 19 determines from the detection voltage of the sensor that the capacitor 18 has been charged, the controller 19 turns off the switches (SW (4n-3), SW (4n-2)) and switches (SW (4n-1), SW (4n)) is turned on. Then, the electric charge accumulated in the capacitor 18 is supplied to the secondary battery (BAn) to be charged via the switches (SW (4n-1), SW (4n)). As a result, the electric power due to the AC noise is once charged in the capacitor 18, and after charging the capacitor 18, the secondary battery (BAn) to be charged is charged.

  As described above, in this example, the switch unit 15 connected between the diode bridge 131 and the capacitor 18 is turned on, the switch unit 17 connected between the capacitor 18 and the battery 30 is turned off, and the AC The capacitor 18 is charged with power converted from noise, and after charging the capacitor 18, the switch unit 15 is turned off and the switch unit 17 is turned on to charge the battery 30. Thereby, since the filter (smoothing circuit 132) can be omitted, the battery charger can be miniaturized.

  The charging circuit 13 and the switch units 15 and 17 described above correspond to the “charging means” of the present invention, the switch unit 15 is the “first switch unit” of the present invention, and the switch unit 17 is the “second switch unit” of the present invention. Is equivalent to.

DESCRIPTION OF SYMBOLS 10 ... Battery charger 11 ... Power feeding bus 12 ... Capacitor 13 ... Charging circuit 131 ... Diode bridge 132 ... Smoothing circuit 132a ... Coil 132b ... Capacitor 14 ... Transformer 141 ... Primary side transformer 142 ... Secondary side transformer 15, 16, 17 ... Switch unit SW ... Switch 18 ... Capacitor 19 ... Controller 20 ... Load 30 ... Battery BA ... Secondary battery

Claims (6)

A power supply bus connected between the load and the battery;
Noise extraction means for extracting AC noise generated at the load and flowing through the power supply bus;
A battery charging device comprising: charging means for charging the battery with the AC noise. The noise extraction means includes
The battery charging device according to claim 1, further comprising a first capacitor connected between the load and the charging unit. The charging means includes
A power conversion circuit for converting the AC noise into power,
The battery charging device according to claim 1, further comprising a smoothing circuit that smoothes the electric power converted by the power conversion circuit. The battery charging apparatus according to claim 1, further comprising an amplifying unit that amplifies the AC noise between the noise extracting unit and the charging unit. The battery has a plurality of secondary batteries,
The feeding bus is connected to both electrodes of the plurality of secondary batteries,
The charging means includes
5. The battery charging device according to claim 1, further comprising a plurality of switches connected to the power supply bus and respectively connected to the plurality of secondary batteries. A control means for controlling charging of the battery;
The feeding bus is a pair of power lines connected to both electrodes of the battery,
The charging means includes
A power conversion circuit for converting the AC noise into power,
A second capacitor connected between the pair of power supply lines between the power conversion circuit and the battery;
A first switch connected between the power conversion circuit and the second capacitor;
A second switch unit connected between the second capacitor and the battery;
The control means includes
Turning on the first switch unit and turning off the second switch unit to charge the second capacitor with the power converted by the power conversion circuit;
6. The battery according to claim 1, wherein after charging the second capacitor, the first switch unit is turned off and the second switch unit is turned on to charge the battery. 6. Battery charger.

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