JP2012152037A - Charging system, electrical appliance having power reception device of charging system, and charge completion discrimination method for charging system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a charging system in which the completion of battery charge in a power reception device can be detected on a power supply device side by a simple and inexpensive structure capable of preventing noise generation.SOLUTION: A charging system (1) includes: a charger (2) (power supply device) having a power supply coil (21); and a charging unit (10) (power reception device) having a power reception coil (13) in which electric current flows by the magnetic field generated in the power supply coil (21). The charging unit (10) includes: a charging control part (16) (charging part); and an electric current magnification part (17) for magnifying the electric current flowing in the power reception coil (13) more than the case of the completion of change to a battery (12) when the charging of the battery (12) is completed. The charger (2) includes a CPU (26) (charge completion discrimination part) for discriminating the completion of charging the battery (12) by detecting the increase of the electric current flowing in the power reception coil (13) by the electric current magnification part (17) by means of the electric current flowing in the power supply coil (21).

Description

  The present invention relates to a power supply device capable of transmitting and receiving electric power via a coil, a charging system including the power receiving device, an electric device including the power receiving device of the charging system, and a charging completion determination method in the charging system.

  2. Description of the Related Art Conventionally, a power feeding device that can exchange power via a coil and a charging system including the power receiving device are known. As such a charging system, for example, as disclosed in Patent Document 1, a mobile phone (power receiving device) and a non-contact charger (power feeding device) each have a coil. In this configuration, the battery is charged using so-called electromagnetic induction in which a current is passed through the coil on the mobile phone side using a magnetic field generated when a current is passed through the coil on the non-contact charger side.

  Patent Document 1 discloses a configuration in which a state such as a full charge on the mobile phone side is transmitted to the non-contact charger side by a signal. Therefore, a control unit that generates a signal, a modulation unit that superimposes the signal on a carrier wave, and the like are provided on the mobile phone side.

Japanese Patent No. 4480048

  By the way, as described above, in the case of a configuration having a function of sending the battery charging completion of the power receiving device as a signal to the power feeding device side, if a control unit, a modulation unit, etc. are provided in the power receiving device, the circuit configuration is correspondingly increased. This increases the complexity and increases the mounting area, and hinders downsizing of the power receiving apparatus. Further, since components that constitute the circuit such as the control unit and the modulation unit are necessary, the manufacturing cost is increased correspondingly, and the power consumption is also increased by these circuits. Furthermore, there is a possibility that a signal transmitted / received becomes noise of the device.

  For this reason, in the present invention, in a charging system including a power receiving device and a power feeding device capable of transmitting and receiving power via a coil, a configuration in which charging completion of the battery in the power receiving device can be detected on the power feeding device side is generated. It is intended to be realized by a simple and inexpensive configuration that can be prevented.

  A charging system according to an embodiment of the present invention includes a power feeding device having a power feeding coil, and a power receiving device having a power receiving coil through which a current flows due to a magnetic field generated by energization of the power feeding coil. A charging unit that charges the battery with a current flowing through the power receiving coil; and a current increasing unit that increases the current flowing through the power receiving coil when the charging of the battery is completed, compared to when the charging of the battery is completed. The power supply device has a charge completion determination unit that determines that the battery has been fully charged when the current increase unit detects that the current flowing through the power receiving coil has increased by the current flowing through the power supply coil. (First configuration).

  With the above configuration, it is possible to detect that the charging of the battery in the power receiving device is completed by the current flowing through the power feeding coil on the power feeding device side. That is, since the current flowing through the power supply coil of the power supply device changes according to the current flowing through the power reception coil of the power reception device due to the mutual induction between the coils, the power reception coil when the battery is completely charged on the power reception device side By increasing the current flowing through the power supply, the current flowing through the power supply coil of the power supply apparatus can also be increased. Therefore, on the power feeding device side, it is possible to easily detect whether or not charging of the battery is completed by the power receiving device by detecting the current flowing through the power feeding coil.

  In this way, it is possible to detect the completion of charging of the battery on the power feeding device side only by increasing the current flowing through the power receiving coil on the power receiving device side. Therefore, the state of charge of the battery on the power receiving device side can be transmitted to the power feeding device side with a simple and inexpensive configuration. In addition, since it is not necessary to transmit and receive signals in a state where signals are superimposed on a carrier wave as in the prior art, the generation of noise can be suppressed.

  In the first configuration, the current increasing unit of the power receiving device bypasses the charging unit and includes a bypass circuit having a smaller resistance than the charging unit, and the bypass circuit charges the battery. It is preferable to have a switch unit that is turned on when completed (second configuration).

  Thereby, the first configuration described above can be realized with a simple and inexpensive configuration. That is, a bypass circuit that bypasses the charging unit is provided, and a switch unit is provided in the bypass circuit that conducts the bypass circuit when the battery is completely charged. Current can flow. As a result, a large current can also flow through the power supply coil of the power supply apparatus, so that the completion of charging of the battery can be easily detected on the power supply apparatus side.

  In the first or second configuration, the current increasing unit of the power receiving device has a current value larger than a maximum value of a current flowing through the power receiving coil during charging of the battery when charging of the battery is completed. Is preferably configured to flow through the power receiving coil (third configuration).

  As a result, after the charging of the battery is completed, a current having a value larger than the maximum value of the current flowing through the power receiving coil during charging of the battery flows through the power receiving coil. Therefore, by detecting the current flowing through the power feeding coil corresponding to the current flowing through the power receiving coil, it is possible to more reliably detect the completion of battery charging on the power feeding device side.

  In the first or second configuration, the charging completion determination unit of the power feeding device has a current value flowing through the power feeding coil that is lower than a threshold value larger than a current value at the completion of charging of the battery during charging of the battery. After that, it is preferable to determine that charging is completed when it is detected that the threshold value has been reached again (fourth configuration).

  By doing so, it is possible to detect the completion of charging of the battery on the power feeding device side without flowing a current larger than the maximum current during charging of the battery through the power receiving coil. That is, when the battery is charged by the power receiving device, the current flowing through the power receiving coil decreases as the battery is fully charged. Then, by increasing the current flowing through the power receiving coil after the battery is completely charged as in the above-described configuration, the current flowing through the power feeding coil falls below the threshold and then reaches the threshold again. By detecting such a change in current, it is possible to easily detect that the battery has been fully charged.

  An electrical apparatus according to an embodiment of the present invention includes the power receiving device in the charging system according to any one of the first to fourth configurations (fifth configuration).

  In the charging completion determination method in the charging system according to the embodiment of the present invention, the battery connected to the power receiving device is charged by causing a current to flow through the power receiving coil of the power receiving device by the magnetic field generated in the power feeding coil of the power feeding device. A charging process, a charging completion detecting process for detecting on the power receiving device side that the charging of the battery is completed, and a charging completion of the battery when the charging completion of the battery is detected by the charging completion detecting process. A current increasing step for flowing a current larger than the current flowing through the power receiving coil and an increase in the current flowing through the power receiving coil based on the current flowing through the power feeding coil of the power feeding device; A charge completion determination step for determining that the battery has been fully charged (sixth method).

  With the above method, the completion of charging of the battery in the power receiving device can be easily detected on the power feeding device side. That is, when charging of the battery is completed in the power receiving device, the current flowing in the power receiving coil in the power receiving device increases, so the current flowing in the power feeding coil in the power feeding device also increases. By detecting this current, it is possible to easily detect completion of charging of the battery on the power feeding device side.

  Therefore, in the above method, since it is not necessary to send and receive a signal as in the prior art, it is possible to prevent the occurrence of noise and to detect the completion of charging of the battery on the power feeding device side with a simple and inexpensive configuration. .

  In the sixth method, the charging completion determination step reaches the threshold again after the current flowing through the power receiving coil of the power receiving apparatus falls below a threshold value larger than the current value at the time of completion of charging the battery. When this is detected on the power feeding device side, it is preferable to determine that charging of the battery is completed (seventh method).

  Also by such a method, it is possible to easily detect completion of charging of the battery in the power receiving device on the power feeding device side.

  According to the charging system of one embodiment of the present invention, since the power receiving device is provided with the current increasing unit that flows a current larger than the current that flows when the charging of the battery is completed when the charging of the battery is completed, the power feeding device The battery charging can be easily detected on the side. Therefore, a configuration that can detect the completion of charging of the battery on the power feeding device side can be realized with a simple and inexpensive configuration that can prevent noise generation.

FIG. 1 is a diagram illustrating a schematic configuration of a charging system according to the first embodiment. FIG. 2 is a circuit diagram showing a schematic configuration of the current increasing section. FIG. 3 is a diagram illustrating a relationship between a power receiving side load current flowing through the power receiving coil and a power feeding side driving current flowing through the power feeding coil. FIG. 4 is a diagram illustrating a change in the power receiving side load current flowing through the charging circuit when the battery is charged. FIG. 5 is a diagram corresponding to FIG. 4 in the charging system according to the second embodiment. FIG. 6 is a diagram corresponding to FIG. 3 in the charging system according to the second embodiment. FIG. 7 is a diagram illustrating a flow of determining whether the battery is completely charged on the charger side.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same or corresponding parts in the drawings are denoted by the same reference numerals and description thereof will not be repeated.

[Embodiment 1]
(overall structure)
FIG. 1 is a diagram showing a schematic configuration of a charging system 1 according to Embodiment 1 of the present invention. The charging system 1 includes a charger 2 (power feeding device) and a charging unit 10 (power receiving device) provided on the device 3 (electric device) side. The charging system 1 is used, for example, as a power supply system for a portable terminal such as a keyless entry system of an automobile or a PDA (Personal Digital Assistant), or a small device (device 3) such as a camera.

  The charging system 1 is configured to transmit and receive electric power in a contactless manner between the charger 2 and the charging unit 10 on the device 3 side. That is, the charger 2 has a power feeding coil 21 connected to a power source (not shown), while the charging unit 10 has a power receiving coil 13 constituting a part of the charging circuit 11 connected to the battery 12. ing. That is, the charging system 1 is configured to supply power from the charger 2 to the charging unit 10 using electromagnetic induction. Here, non-contact power transmission / reception means power transmission / reception between two devices without a terminal.

  The charger 2 includes a power supply coil 21 that is electrically connected to a power source (not shown), a drive circuit 22 that controls a current that flows through the power supply coil 21 to generate a predetermined magnetic field, and a power supply coil. And a current detection circuit 23 for detecting a current flowing through the circuit 21. The current detection circuit 23 includes a current amplifier 24 that detects a current, an A / D converter 25 that converts the current detected by the current amplifier 24 into a digital signal, and a CPU 26 (charge completion) that processes the digital signal. Determination unit). Thereby, the electric current detection circuit 23 can detect this electric current, when the electric current which flows into the electric power feeding coil 21 changes according to the electric current change of the receiving coil 13 in the charging unit 10 of the apparatus 3 so that it may mention later. . The outputs of the oscillators 27 and 28 are input to the drive circuit 22 and the CPU 26, respectively.

  The charging unit 10 has a charging circuit 11 for charging the battery 12. The charging circuit 11 includes a power receiving coil 13, a rectifying circuit 14, a voltage adjusting unit 15, a charging control unit 16 (charging unit), and a current increasing unit 17. The charging circuit 11 is configured such that a current flowing through the power receiving side coil 13 flows to the voltage adjusting unit 15 and the charging control unit 16 via the rectifying circuit 14. As a result, in the charging circuit 11, AC power generated by electromagnetic induction in the power receiving coil 13 is converted into DC power by the rectifier circuit 14, adjusted to a predetermined voltage by the voltage adjusting unit 15, and then the charging control unit 16. The battery 12 is charged via Here, the rectifier circuit 14 may have any configuration as long as it can convert AC power into DC, such as a bridge rectifier circuit. The voltage adjustment unit 15 may have any configuration as long as the voltage supplied to the battery 12 can be adjusted.

  The charging control unit 16 is for controlling the charging of the battery 12, and is configured to control the voltage and current of the battery 12 according to the charging state of the battery 12. Further, as will be described in detail later, the charging control unit 16 outputs a charging completion signal to the current increasing unit 17 so as to increase the current flowing through the charging circuit 11 when the charging of the battery 12 is completed.

  The current increasing unit 17 is provided so as to form a bypass circuit of the charging control unit 16. In other words, the current increasing unit 17 is provided between the voltage adjusting unit 15 and the charging control unit 16 so as to bypass the charging control unit 16. As will be described in detail later, the current increasing unit 17 includes a switching element 31 (switch unit) that forms a bypass circuit in the ON state, and a resistor 32 connected in series to the switching element 31.

  Although not particularly illustrated, the battery 12 has a case formed in a columnar shape by combining two members having a bottomed cylindrical shape, for example. In this case, an electrode body in which a plurality of flat positive electrodes and negative electrodes are alternately stacked is housed.

In the positive electrode, positive electrode active material layers containing a positive electrode active material are provided on both surfaces of a positive electrode current collector made of a metal foil such as aluminum. Specifically, the positive electrode is formed by applying a positive electrode mixture containing a positive electrode active material, a conductive auxiliary agent, a binder, and the like, which is a lithium-containing oxide capable of inserting and extracting lithium ions, onto a positive electrode current collector made of aluminum foil or the like. And dried. As the lithium-containing oxide as the positive electrode active material, for example, a lithium composite oxide such as lithium cobalt oxide such as LiCoO ₂ , lithium manganese oxide such as LiMn ₂ O ₄ , lithium nickel oxide such as LiNiO ₂ is used. Is preferred. Note that only one type of material may be used as the positive electrode active material, or two or more types of materials may be used. Further, the positive electrode active material is not limited to those described above.

  In the negative electrode, negative electrode active material layers containing a negative electrode active material are provided on both surfaces of a negative electrode current collector made of a metal foil such as copper. Specifically, the negative electrode is formed by applying and drying a negative electrode mixture containing a negative electrode active material capable of occluding and releasing lithium ions, a conductive additive and a binder on a negative electrode current collector made of copper foil or the like. Is done. As the negative electrode active material, for example, it is preferable to use a carbon material (such as graphite, pyrolytic carbon, coke, or glassy carbon) that can occlude and release lithium ions. The negative electrode active material is not limited to those described above.

  Therefore, the battery 12 in the present embodiment is a so-called lithium ion battery that performs charging and discharging by moving electrons between the positive electrode and the negative electrode by lithium ions.

  Each positive electrode is electrically connected to one member constituting the case of the battery 12. On the other hand, each negative electrode is electrically connected to the other member constituting the case of the battery 12. Thereby, the electrode body inside the battery 12 is electrically connected to the case of the battery 12.

(Current increasing part)
Next, the configuration of the current increasing unit 17 will be described in detail with reference to FIG.

  As described above, the current increasing unit 17 includes the switching element 31 that forms the bypass circuit of the charging control unit 16 in the ON state, and the resistor 32 that is connected in series to the switching element 31. The switching element 31 is composed of, for example, an NPN-type bipolar transistor, and is configured such that the output of the charge control unit 16 is input to the base. The switching element 31 has the above-described resistor 32 connected to the collector side of the switching element 31 and the emitter side connected to the wiring of the charging circuit 11. Note that the switching element 31 may be other than an NPN-type bipolar transistor as long as it can be switched.

  Here, the charge control unit 16 includes a charge control device 41 that performs charge control, and a resistor 42 provided between a terminal of the charge control device 41 and the wiring of the charging circuit 11. The charging control device 41 includes a switching element 43 connected to the terminal. The switching element 43 is controlled to be in an on state while the battery 12 is being charged, and to be in an off state when the battery 12 is completely charged.

  Accordingly, when the switching element 43 in the charge control device 41 is in an on state, that is, while the battery 12 is being charged, the switching element 43 is conductive, so that no signal is output from the charge control unit 16. On the other hand, when the switching element 43 in the charging control device 41 is in an off state, that is, when the charging of the battery 12 is completed, a signal is output from the charging control unit 16. Therefore, when charging of the battery 12 is completed, a signal is input from the charging control unit 16 to the base of the switching element 31 of the current increasing unit 17. This signal corresponds to the above-described charging completion signal.

  The resistor 42 in the charging control unit 16 has a larger resistance value than the resistor 32 of the current increasing unit 17. Thereby, when the charging of the battery 12 is completed and the switching element 31 of the current increasing unit 17 is turned on, a current larger than the current flowing through the charging control unit 16 flows through the current increasing unit 17.

  With the configuration as described above, when charging of the battery 12 is completed, in the charging circuit 11, a circuit that bypasses the charging control unit 16 is formed by the current increasing unit 17, and a larger current flows than when the battery 12 is charged. .

  In the case of the configuration shown in FIGS. 1 and 2 described above, when a current flows through the charging circuit 11 on the power receiving side, the power receiving coil 13 of the charging circuit 11 and the power feeding coil 21 of the charger 2 on the power feeding side. A current corresponding to the current flowing through the power receiving coil 13 flows through the feeding coil 21 due to the mutual induction action between the power receiving coil 13 and the power receiving coil 21. That is, there is a correlation as shown in FIG. 3, for example, between the power receiving side load current flowing in the power receiving coil 13 and the power feeding driving current flowing in the power feeding coil 21. For example, in FIG. 3, in the state of point A, if the power receiving side load current is A2, the power feeding side driving current is A1.

  By utilizing such a relationship, it is possible to detect a change in the current flowing in the power receiving coil 13 on the power receiving side as a change in the current flowing in the power feeding coil 21 on the power feeding side. Therefore, in the present embodiment, when charging completion is detected by the charging control unit 16 of the device 3 on the power receiving side, by increasing the current of the charging circuit 11 on the power receiving side, the charger 2 on the power feeding side also increases. Enabled to detect the completion of charging. Accordingly, it is possible to transmit the fact that the charging completion is detected on the power receiving side to the charger 2 on the power feeding side without providing a control unit, a modulation unit, or the like for transmitting / receiving a signal to / from the charging system 1. .

  Specifically, as shown in FIG. 4, when the charging of the battery 12 is completed, the current flowing to the power receiving side becomes small (power receiving side load current C2), so that the current corresponding to the power receiving side load current is generated on the charger 2 side. If detected, the charging completion of the battery 12 can be detected on the charger 2 side. However, when the charger 2 detects the power feeding side drive current corresponding to the power receiving side load current, there are variations in the current value (for example, C1 ′ to C1 ″ in FIG. 3) caused by the arrangement, length, shape, and the like of the coil. Because it exists, it is difficult to detect a slight difference in the receiving side load current. In particular, in the case of the present embodiment, as shown in FIG. 4, the power receiving side load current (low current before and after charging) flowing to drive each circuit before and after the completion of charging and the power receiving side load current C2 at the time of completion of charging. Since the difference is small, it is difficult to accurately determine whether or not the charging of the battery 12 is completed even if the current corresponding to the power receiving side load current is detected on the charger 2 side.

  Therefore, in the present embodiment, as shown in FIG. 4, when charging of the battery 12 is completed, a bypass circuit is formed by the above-described current increasing unit 17 after a predetermined time has elapsed, and the power receiving side load current is charged. It is increased to B2, which is larger than A2, which is the maximum current at the time. Thereby, on the power feeding side, the current B1 corresponding to the power receiving side load current B2 can be easily detected, and the charging completion of the battery 12 can be easily determined. Note that the power receiving side load currents A2, B2, and C2 in FIG. 4 correspond to the power receiving side load currents A2, B2, and C2 shown on the horizontal axis of the graph of FIG. Further, in FIG. 3, point A is when the power-receiving-side load current during charging of the battery 12 is maximum, point B is when the current increasing unit 17 is operated after completion of charging, point C is when charging is completed, Each is shown.

  The charging completion determination operation of the battery 12 in this embodiment is summarized as follows. The charging completion determination operation will be described with reference to FIG.

  First, in the charging circuit 11 on the power receiving side, when charging of the battery 12 is completed, the charging control unit 16 detects completion of charging of the battery 12. After a predetermined time has elapsed, the charging control unit 16 turns off the internal switching element 43 and outputs a charging completion signal to the current increasing unit 17. Thereby, the switching element 31 of the current increasing unit 17 is turned on, and the power receiving side load current B <b> 2 flows through the power receiving coil 13 of the charging circuit 11. In the present embodiment, the charging control unit 16 outputs the charging completion signal after a predetermined time has elapsed from the completion of charging. However, the present invention is not limited to this, and the charging completion signal may be output simultaneously with the completion of charging.

  Here, when the charging control unit 16 detects that the power receiving side load current is 1/10 or less of the maximum value of the power receiving side load current during charging (A2 in FIG. 4), it determines that charging is complete. Is configured to do. In addition, the charging control unit 16 determines that the charging is completed when it continuously detects that the power-receiving-side load current has become 1/10 or less of A2 for about 1 second or more in order to avoid the influence of noise or the like. Is configured to do.

  In the charger 2 on the power feeding side, a power feeding side drive current B1 corresponding to the power receiving side load current B2 flows through the power feeding coil 21 due to the mutual induction action of the power receiving coil 13 and the power feeding coil 21 (see FIG. 3). When this B1 is detected by the current detection circuit 23, the CPU 26 in the current detection circuit 23 determines that the charging of the battery 12 has been completed.

  When it is determined that charging of the battery 12 is completed, the charger 2 stops energization of the power feeding coil 21. Thereby, it is possible to prevent useless power from being used in the charger 2 and useless heat generation in the charger 2.

  Here, the process of charging the battery 12 using the power receiving system 1 in FIG. 1 is the charging process, and the charging control unit 16 of the device 3 is the process of detecting the charging completion of the battery 12 is the charging completion detecting process. It corresponds. Further, when the charging completion of the battery 12 is detected, the step of operating the current increasing unit 17 to increase the power receiving side load current flowing through the power receiving coil 13 to B2 corresponds to the current increasing step, and corresponds to the power receiving side load current B2. Then, the process of detecting the power supply side drive current flowing through the power supply coil 21 and determining that the charging of the battery 12 has been completed corresponds to the charge completion determination process.

(Effect of Embodiment 1)
As described above, in this embodiment, the current increasing unit 17 is provided in the charging circuit 11 on the power receiving side so as to bypass the charging control unit 16. When the charging of the battery 12 is completed, the current increasing unit 17 is operated so that the current flowing through the power receiving coil 13 of the charging circuit 11 is larger than the maximum current when the battery 12 is charged. At this time, since the current B1 corresponding to the power receiving side load current B2 flowing in the power receiving coil 13 flows in the power feeding coil 21 in the charger 2 on the power feeding side, the current detection circuit 23 detects the current B1. The charging completion of the battery 12 can be determined on the charger 2 side.

  Therefore, with the above-described configuration, the charging completion of the battery 12 detected on the power receiving side is transmitted to the charger 2 on the power feeding side without providing a control unit, a modulation unit, or the like for transmitting and receiving signals to the charging system 1. Can do. Therefore, the completion of charging of the battery 12 can be easily detected on the side of the charger 2 with a simple and inexpensive configuration that can prevent the generation of noise.

[Embodiment 2]
Next, the charging completion determination operation of the charging system according to the second embodiment will be described. In the charging completion determination operation in this embodiment, after the charging of the battery 12 is completed, the power receiving side load current flowing through the power receiving coil 13 is set to a value that is larger than the current at the time of charging and smaller than the maximum current at the time of charging. Hereinafter, the charging completion operation of the present embodiment will be described with reference to FIGS. In the present embodiment, each configuration of the charging system is the same as the configuration of the first embodiment described above, and thus description and illustration are omitted.

  In the present embodiment, as shown in FIG. 5, the power receiving side load current flowing through the charging circuit 11 on the power receiving side after the charging of the battery 12 is completed is D2. That is, after a predetermined time has elapsed after the charging of the battery 12 is completed, the charging control unit 16 operates the current increasing unit 17 to set the power receiving side load current to D2. This D2 is larger than the power receiving side load current C2 when the battery 12 is fully charged and smaller than the maximum value A2 of the power receiving side load current when the battery 12 is charged.

  Then, as shown in FIG. 6, a power supply side drive current D1 flows through the power supply coil 21 of the charger 2 on the power supply side. In FIG. 6, a point D indicates a case where the power receiving side load current D <b> 2 flows in the charging circuit 11.

  In the case of the present embodiment, as shown in FIG. 5, there is a case where the power receiving side load current becomes D2 even during charging of the battery 12 (such as T1 in the figure), so the power receiving side load current simply corresponds to D2. In the configuration in which the power supply side drive current to be detected is detected on the charger 2 side, there is a possibility that the charge completion is erroneously detected.

  Therefore, in this embodiment, the charger 2 determines the completion of charging of the battery 12 based on a flow as shown in FIG. The flow of FIG. 7 will be described below.

  The flow in FIG. 7 starts when the battery 12 starts to be charged. When the flow shown in FIG. 7 starts (start), in step S1, it is determined whether or not the power supply side drive current has reached D1 (threshold value) corresponding to the power reception side load current D2. If it is determined in step S1 that the power supply side drive current has become D1 (in the case of YES), it is determined in subsequent step S2 whether the power supply side drive current has become smaller than D1 by α. On the other hand, when it is determined in step S1 that the power supply side drive current is not D1 (in the case of NO), the determination in step S1 is repeated until the power supply side drive current becomes D1.

  If it is determined in step S2 that the power supply side drive current has become smaller than D1 by α (in the case of YES in step S2), the process proceeds to step S3 to determine whether or not the power supply side drive current has become D1. To do. On the other hand, if it is not determined in step S2 that the power feeding side drive current has become smaller than D1 by α (NO), the determination in step S2 is repeated.

  When it is determined in step S3 that the power supply side drive current has again become D1 (in the case of YES), the process proceeds to step S4, where it is determined that charging of the battery 12 is completed, and the flow of FIG. (End). On the other hand, if it is not determined in step S3 that the power supply side drive current has reached D1 (NO), the determination in step S3 is repeated.

  That is, in step S3, the case where the power supply side drive current decreases from D1 corresponding to the power reception side load current and then becomes D1 again (point T2 in FIG. 5) is detected.

  Here, the steps S1 to S4 correspond to a charging completion determination step for determining completion of charging of the battery 12 on the charger 2 side.

(Effect of Embodiment 2)
As described above, according to this embodiment, after the charging of the battery 12 is completed, the power receiving side load current flowing through the power receiving side charging circuit 11 is larger than the power receiving load current C2 at the time of charging completion and the power receiving load current at the time of charging. It was smaller than the maximum value A2. Even with such a configuration, it is possible to detect the completion of charging of the battery 12 in the charger 2 on the power supply side, as in the first embodiment.

(Other embodiments)
While the embodiments of the present invention have been described above, the above-described embodiments are merely examples for carrying out the present invention. Therefore, the present invention is not limited to the above-described embodiment, and the above-described embodiment can be appropriately modified and implemented without departing from the spirit of the invention.

  In each of the embodiments described above, the power receiving side load current flowing through the power receiving coil 13 after the battery 12 is completely charged is increased by the current increasing unit 17 including the switching element 31 and the resistor 32 provided in the charging circuit 11. However, the configuration of the current increasing unit is not limited to the configuration shown in each of the above embodiments, and any configuration may be used as long as it can increase the power receiving side load current in the charging circuit 11.

  In the above embodiments, each battery is configured as a lithium ion battery. However, each battery may be a battery other than a lithium ion battery as long as the battery is configured to perform charge control. Further, the shape of each battery is not limited to a coin shape, and may be any shape such as a cylindrical shape or a rectangular parallelepiped shape.

  The charging system according to the present invention includes a power feeding device having a power feeding coil and a power receiving device having a power receiving coil, and can be used in a configuration in which charging is performed in a non-contact manner.

DESCRIPTION OF SYMBOLS 1 Charging system, 2 Charger (power supply device), 3 Device (electrical device), 10 Charging unit (power receiving device), 11 Charging circuit, 12 Battery, 13 Power receiving coil, 16 Charging control unit (charging unit), 17 Current increase Part, 21 feeding coil, 26 CPU (charge completion determination part), 31 switching element (switch part)

Claims (7)

A power supply device having a power supply coil;
A power receiving device having a power receiving coil through which a current flows by a magnetic field generated by energizing the power feeding coil;
The power receiving device is:
A charging unit that charges the battery with a current flowing through the power receiving coil; and
A current increasing portion that increases the current flowing through the power receiving coil when the battery is fully charged compared to when the battery is fully charged;
The power supply device includes a charge completion determination unit that determines that charging of the battery is completed when the current increase unit detects that the current flowing through the power receiving coil has increased due to the current flowing through the power supply coil. system. The charging system according to claim 1,
The current increasing unit of the power receiving device bypasses the charging unit and includes a bypass circuit having a smaller resistance than the charging unit,
The bypass circuit includes a switch unit that is turned on when charging of the battery is completed. The charging system according to claim 1 or 2,
The current increasing unit of the power receiving device is configured to flow a current having a value larger than a maximum value of a current flowing through the power receiving coil during charging of the battery when the battery is completely charged. The charging system. The charging system according to claim 1 or 2,
The charging completion determination unit of the power supply apparatus reaches the threshold again after the current value flowing through the power supply coil falls below a threshold value larger than the current value at the completion of charging of the battery during charging of the battery. A charging system configured to determine that charging is complete when it is detected.   The electric equipment provided with the power receiving apparatus in the charging system as described in any one of Claim 1 to 4. A charging step of charging a battery connected to the power receiving device by passing a current through the power receiving coil of the power receiving device by a magnetic field generated in the power feeding coil of the power feeding device;
A charging completion detection step for detecting on the power receiving device side that the charging of the battery is completed;
A current increasing step of flowing a current larger than a current flowing at the completion of charging of the battery to the power receiving coil when the charging completion of the battery is detected by the charging completion detecting step;
A charging completion determination step of determining that the battery is completely charged on the power supply device side when an increase in current flowing in the power reception coil is detected based on a current flowing in the power supply coil of the power supply device. Charging completion determination method. In the charging completion determination method according to claim 6,
In the charging completion determination step, after the current flowing in the power receiving coil of the power receiving device falls below a threshold value larger than the current value at the time of completion of charging of the battery, the power supply device side indicates that the threshold value is reached again. A charging completion determination method in a charging system, which, when detected, determines that charging of the battery is completed.

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