Wearable device

Abstract

An HMD (100) is provided with: a plurality of power receiving units (102a, b) on which a first battery and a second battery (200a, b) can be mounted and which receive power from the first battery and the second battery by wireless transmission; a power management unit (106) that monitors the states of the first battery and the second battery; a communication unit (108) that wirelessly communicates with the first battery and the second battery; and a plurality of restricting units (104a, b) that restrict the power received by the plurality of power receiving units. The control unit (101) restricts the power supplied to the load by the restriction unit in accordance with the power usage status of the load in the device, and the power management unit acquires information on the remaining power amounts of the first battery and the second battery via the communication unit, and displays the acquired information on the display (119). As a result, it is possible to supply electric power required for driving the device while the HMD is being worn, thereby enabling the HMD to be continuously used.

Description

[0001] This application is a divisional application of the invention patent application with application date of January 16, 2019, application number 201980007758.9, and titled “Wearable device and battery and power supply system used therefor” Technical Field

[0002] The present invention relates to a contactless power supply technology for powering wearable devices such as head-mounted displays (hereinafter referred to as HMDs). Background Art

[0003] As a contactless power supply technology for supplying power to a wearable device that a user wears on their body, the following technologies are known.

[0004] Patent Document 1 discloses a structure involving electronic glasses with variable-focus lenses and a charging device therefor. The charging device is placed on the leg cuff of the electronic glasses, and power is supplied from the charging device's power transmission coil to the electronic glasses' power receiving coil via electromagnetic induction, thereby charging the driving battery of the electronic glasses.

[0005] Patent document 2 discloses a structure for a wearable device, which has a heating portion for heating the front part of the eye arranged in front of the user's eyes. The front part of the eye is heated by heat generated by an electric wire wound around the front part of the eye, and the above-mentioned electric wire is a receiving coil that receives power supply from an external transmission coil in a non-contact manner.

[0006] Patent document 3 discloses a structure relating to a power supply system for supplying power from a secondary battery module to an electronic device (e.g., an eyeglass-type device), wherein a flexible secondary battery, a power transmission unit for performing contactless power transmission, and a flexible thermoelectric power generation device are housed in a strip-shaped portion of the secondary battery module, and power is transmitted from the power transmission unit of the secondary battery module to a power receiving unit of the electronic device through contactless power transmission.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Laid-Open No. 2009-251068

[0010] Patent Document 2: Japanese Patent Application Laid-Open No. 2016-032213

[0011] Patent Document 3: Japanese Patent Application Laid-Open No. 2016-073196 Summary of the Invention

[0012] Technical problem to be solved by the invention

[0013] In recent years, HMDs have become capable of performing functions similar to those of wearable computers, smartphones, and tablets. Furthermore, glass-type, see-through HMDs are gaining attention as core components for augmented reality (AR) technology, while immersive HMDs are gaining attention as core components for virtual reality (VR) technology. HMDs are also being used for watching movies and playing games.

[0014] However, as HMDs become more multifunctional, their power consumption increases. Current batteries offer limited battery life, making continuous use of the HMD impossible. To address this issue, users must reliably connect the HMD to an external power source via a cable for charging, or interrupt HMD use to recharge the battery, which is inconvenient for the user. To enable continuous use of the HMD, the battery capacity can be increased, but this also comes with increased weight. Especially for eyeglass-type HMDs, like regular glasses, the weight of the device rests on the user's ears and nose, so weight must be minimized to minimize any impact on the wearing experience. Furthermore, like mobile devices, HMDs are becoming increasingly smaller and thinner, but the need to connect cables during charging and use is cumbersome, leading to increasing user demand for simpler charging methods. Therefore, for wearable devices that are frequently worn on the body, ensuring continuous wear and eliminating the hassle of connecting cables are crucial.

[0015] In Patent Document 1, to charge the battery that drives the electronic glasses, the user must attach a portable charging device to the leg of the glasses. Attaching or removing the portable charging device causes the glasses to move or forces the user to temporarily remove the glasses from the head, temporarily interrupting their use. This makes it difficult for the user to continue using the glasses while still wearing them. Patent Document 1 also describes attaching a portable charger to the leg of the glasses and connecting it to an external power source for charging, but this still involves the hassle of connecting cables. Furthermore, the portable charging device connects to the charger via external terminals, leaving terminals exposed to the outside. This raises concerns about short circuits and terminal corrosion caused by sweat when worn on the head.

[0016] Patent Document 2 mentioned above describes a power receiving coil formed by a wire wound around the front of the eye of the wearable device, which receives power from an external power transmission coil in a non-contact manner. At this time, in order to receive the desired power supply from the external power transmission coil, the distance between the power transmission coil and the power receiving coil must be close. This is to suppress the radio waves leaking to the surroundings during power transmission to within the allowable value. As described in Patent Document 2, when the electronic glasses are placed on a charging stand, etc., so that the power transmission coil and the power receiving coil are close to each other, the desired power transmission can be performed. However, when the user is wearing and using the wearable device, the external power transmission coil must be close to the front of the eye (the location of the power receiving coil), which will obstruct the field of view of the user using the wearable device. In other words, it is expected that sufficient power cannot be supplied when the user is wearing the wearable device.

[0017] In Patent Document 3, an electronic device (glasses-type device) receives power contactlessly from a belt-shaped secondary battery module worn around the waist. Given the distance between the user's waist and head, it's foreseeable that power consumption by glasses-type devices like HMDs would be difficult to supply. Furthermore, Patent Document 3 describes the ability to charge the secondary battery via a cable from the terminal, but as mentioned above, charging via a cable is inconvenient for the user.

[0018] The object of the present invention is to provide a wearable device that can supply the power required to drive the device while the wearable device is worn and used, in view of the problems of the above-mentioned prior art, and is less troublesome for the user to use.

[0019] Technical means to solve the problem

[0020] An example of the present invention is as follows. A wearable device includes: a plurality of power receiving units capable of mounting at least a first battery and a second battery and receiving power from the first and second batteries via wireless transmission; a power management unit that monitors the status of the mounted first and second batteries; a communication unit that wirelessly communicates with the mounted first and second batteries; a display that provides information to the user; a plurality of limiting units that limit the power received by the plurality of power receiving units; and a control unit that controls the power receiving units, the power management unit, the communication unit, the display, and the limiting units. The control unit limits the power supplied to the load in the wearable device via the limiting units according to the power usage status of the load, and the power management unit obtains information on the remaining power of the mounted first and second batteries via the communication unit and displays the obtained remaining power information on the display.

[0021] Furthermore, the plurality of limiting units have a function of preventing reverse current from flowing toward one side of the first battery and the second battery. When the power management unit determines that the remaining power of the first battery in use is less than a threshold value, the control unit controls the reverse current prevention function of the limiting unit, switches the power receiving system from the first battery in use to the second battery in standby, and displays a warning on the display to remind the user to replace the first battery in use.

[0022] The battery of the present invention can be installed on a wearable device to supply power and can be charged by a charger, and is characterized in that it includes: a battery unit for storing power; a power transmission and receiving unit, which can transmit power from the battery unit to the wearable device through wireless transmission, and can receive power from the charger in order to charge the battery unit; a conversion unit, which converts direct current and alternating current between the battery unit and the power transmission and receiving unit; a power storage state identification unit, which detects and saves the remaining power or power storage state information of the battery unit; a communication unit for wirelessly communicating with the wearable device and the charger; and a control unit that controls the power transmission and receiving unit, the power storage state identification unit and the communication unit, wherein the power storage state identification unit can send information about the remaining power of the battery unit to the wearable device through the communication unit, and can send the power storage state information of the battery unit to the charger, and when the control unit receives a control command from the wearable device through the communication unit, it stops transmitting power from the battery unit to the wearable device.

[0023] Furthermore, the power supply system of the present invention includes a wearable device, a battery for supplying power to the wearable device, and a charger for charging the battery. The wearable device is characterized in that it includes: a plurality of power receiving units capable of mounting at least a first battery and a second battery and receiving power from the first and second batteries via wireless transmission; a power management unit that monitors the status of the mounted first and second batteries, and a third battery being charged by the charger; a communication unit that wirelessly communicates with the mounted first and second batteries and the charger; and a display that provides information to the user. The first to third batteries include: a first storage battery unit that stores power; a power transmission and reception unit capable of wirelessly transmitting power from the first storage battery unit to the wearable device and receiving power from the charger to charge the first storage battery unit; a power storage status recognition unit that detects and stores information on the remaining charge of the first storage battery unit or the power storage status of the first storage battery unit during charging; and a communication unit that wirelessly communicates with the wearable device and the charger. The charger includes: a second storage battery unit for storing electricity; a power transmission unit for wirelessly transmitting electricity from the second storage battery unit to the third battery being charged; a charging battery monitoring unit for acquiring information on the charge state of the third battery being charged; and a communication unit for wirelessly communicating with the wearable device and the third battery. The wearable device displays on the display the remaining charge information acquired from the attached first and second batteries, and the charge state information of the third battery being charged acquired from the charger. If the remaining charge of the first battery being used is determined to be less than a threshold, the wearable device switches the power receiving system from the first battery being used to the second battery being on standby, and displays on the display a warning prompting the user to replace the first battery being used.

[0024] Effects of the Invention

[0025] According to the present invention, the required power can be supplied while the wearable device is being worn, allowing the device to be used continuously. For example, even when the user is watching a long movie, the wearing experience is not affected by the added battery. Furthermore, there is no need to connect a power supply cable from the terminals of the wearable device to an external power source, thus improving user convenience. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a diagram showing the overall configuration of a power supply system consisting of an HMD, a battery, and a charger (Example 1).

[0027] Figure 2 : is a block diagram showing the internal structure of HMD 100 .

[0028] Figure 3 It is a block diagram showing the internal structure of the battery 200 .

[0029] Figure 4 is a block diagram showing the internal structure of charger 300 .

[0030] Figure 5A 1 is a diagram showing power transmission between the HMD 100 and the batteries 200 a and b in use.

[0031] Figure 5B 1 is a diagram showing power transmission between the battery 200 c and the charger 300 during charging.

[0032] Figure 6A This diagram shows the communication between the HMD, the battery in use, and the charger.

[0033] Figure 6B This diagram shows the communication between the HMD, a battery being charged, and a charger.

[0034] Figure 7A FIG. 1 is a diagram showing an example of displaying various function menus of the HMD on the display.

[0035] Figure 7B This figure shows an example of displaying the battery status on the display.

[0036] Figure 8 This diagram shows data transmission between the power supply system and the cloud.

[0037] Figure 9 This is a diagram showing control of power transmission between the HMD and the battery (Example 2).

[0038] Figure 10 This is a flowchart showing a process of removing a battery in use from an HMD.

[0039] Figure 11 This is a flowchart showing the process of switching from the battery in use to the battery in standby.

[0040] Figure 12 This is a flowchart showing the process when the battery is detached from the HMD.

[0041] Figure 13 This is a diagram showing the operation of attaching a battery to the HMD and the charger (Example 3).

[0042] Figure 14 This is a diagram showing an example of an electric system circuit within a battery.

[0043] Figure 15 This is a diagram showing an example of the internal structure of a battery.

[0044] Figure 16 This figure shows the state when the battery is installed in the HMD.

[0045] Figure 17 This is a diagram showing another example of the internal structure of a battery.

[0046] Figure 18 Yes Figure 17 FIG. 1 is a diagram of a modified example of .

[0047] Figure 19 1 is a diagram showing the configuration of a charger 400 for charging a battery mounted on an HMD.

[0048] Figure 20A This is a diagram showing the configuration of a power supply system that supplies power not only from a battery but also from a charger 500 to an HMD (Example 4).

[0049] Figure 20B Yes Figure 20A FIG2 is a diagram showing a specific application example of a power supply system. DETAILED DESCRIPTION

[0050] The following drawings are used to describe the embodiments of the present invention in detail. However, the present invention should not be limited to the description of the following embodiments. It is easy for those skilled in the art to understand that the specific structure can be changed without departing from the scope of the ideas and key points of the present invention. In the structure of the invention described below, for the same part or part with the same function, the same figure number may be used in different figures and repeated descriptions may be omitted.

[0051] Example 1

[0052] In Example 1, the basic structure for supplying power to the wearable device of the present invention is described. Among them, a glasses-type head-mounted display (hereinafter referred to as HMD) is used as an example of a wearable device worn on the body by the user. A plurality of batteries are installed on the HMD. When the remaining power of the battery in use is insufficient, it is removed from the HMD and charged with a charger. When the battery is charging, the other batteries switched to standby supply power to the HMD, so that the user can continue to use the HMD. At this time, power is transmitted wirelessly (contactlessly) between the HMD and the battery, and between the battery and the charger, and information such as the remaining power and charge level of the battery is transmitted through mutual communication.

[0053] Figure 1This diagram shows the overall configuration of the power supply system consisting of HMD 100, battery 200, and charger 300. First, the basic operation will be explained. In the glasses-type HMD 100, the bilaterally symmetrical "temples" (temple sections 114) of the glasses have power receiving units 102a and 102b, and two batteries 200a and 200b are installed. Power is supplied from batteries 200a and 200b to the power receiving units 102a and 102b via power transmission and reception coils. While two batteries are used here, a plurality of batteries may be used.

[0054] When the remaining charge of one battery 200a becomes low while using the HMD 100, a low-charge warning is displayed on the display 119 of the HMD 100. The user removes the battery 200a from the power receiving unit 102a and inserts it into the charging slots 311 (in this example, the four slots 311a to 311d) of the charger 300. During this time, the HMD 100 switches to the other battery 200b, which is on standby, and continues operation.

[0055] While the charger 300 is charging the battery 200a, power is also supplied via the power transmission and reception coils. When the battery 200a is fully charged, the display on the HMD 100 notifies the user of the completion of charging, and the user then removes the battery 200a and installs it in the power receiving unit 102a of the HMD 100. This allows the user to continuously use the HMD 100 by installing multiple batteries in the HMD 100 and switching between them. However, since replacing the battery 200 in the HMD 100 and inserting the battery into the charger 300 are performed while the user is wearing the HMD 100, the following improvements have been implemented.

[0056] On HMD 100, an infrared sensor 115a is located just behind the power receiving unit 102a, where the battery 200 is installed, facing the outer side of the temple. The power receiving unit 102b on the opposite side is also equipped with an infrared sensor 115b. To remove the battery 200a installed in the power receiving unit 102a, the user can insert their finger into the recessed area at the rear end of the power receiving unit 102a to easily remove the battery 200a. In this case, the infrared sensor 115a located near the rear end of the power receiving unit 102a detects the user's hand approaching to remove the battery 200a. If the user mistakenly attempts to remove the battery 200b on the opposite side (the right eye side) instead of the battery 200a on the left eye side, the infrared sensor 115b located near the power receiving unit 102b on the right eye side detects the user's hand approaching and issues a warning that the battery to be replaced is the left one, not the right one. This prevents user error.

[0057] Next, the user inserts and sets the removed battery 200a into one of the multiple charging slots 311a to 311d on the charger 300. Slot number sections 312a to 312d corresponding to each charging slot are raised in the shape of the number, allowing the user to touch them to identify the slot number and the charger's orientation. Furthermore, the slot number section 312 lights up a red LED when charging begins and a green LED when charging is complete. Similarly, for the battery 200 inserted in the charging slot 311, a red LED 215 lights up when charging begins and a green LED 215 lights up when charging is complete.

[0058] The glasses-type HMD 100 can be worn on and off the head by unfolding the temples. Strain sensors 116a and 116b are provided at the ends of the temples near the display unit. These sensors detect the unfolding of the HMD while it is being worn, thereby notifying when it has been removed from the head. If the detection signals from the strain sensors 116a and 116b remain unchanged for a specified period of time (e.g., one minute), the HMD 100 automatically switches to standby mode. When the detection signals change again, the HMD is activated. This reduces power consumption in the HMD 100. A camera 120 and an infrared sensor 115c are provided on the front of the HMD 100.

[0059] Next, the respective structures of the HMD 100 , the battery 200 , and the charger 300 will be described.

[0060] Figure 2 1 is a block diagram showing the internal structure of the HMD 100. The HMD 100 includes a control unit 101, a memory unit 105, a power management unit 106, a sensor unit 107, a communication unit 108, a data output unit 109, and a data input unit 110. The control unit 101 controls the overall operation of the HMD 100.

[0061] The memory unit 105 stores information about the internal state of the HMD 100 and the charge state of the battery 200, and also stores image data to be displayed on the HMD. The power management unit 106 includes a power receiving unit 102, a conversion unit 103, and a limiting unit 104 for receiving power from the battery 200 in use, and supplies power to various components within the HMD 100. The power receiving unit 102 includes a power receiving coil capable of wirelessly receiving power. Furthermore, the power management unit 106 monitors the status of the battery 200 in use in the HMD 100, the battery 200 being charged in the charger 300, and the internal battery. The frequency counter 121 detects whether the battery 200 in use has been removed (dropped). Details of these operations will be described later.

[0062] The sensor unit 107 includes an infrared sensor 115, a strain sensor 116, and, as needed, an acceleration sensor, a gyro sensor, a magnetic sensor, a temperature sensor, an electrostatic sensor, a tactile sensor, and the like. The communication unit 108 includes wireless LAN and Bluetooth (registered trademark) for wireless communication with the battery 200 and charger 300. It may also include a "One-Seg" mobile broadcast function and a GPS (Global Positioning System)-based position information acquisition function.

[0063] The data output unit 109 is composed of a display 119 that displays images and information provided to the user on the lens portion of the glasses, a speaker (earphones) that outputs sound, a light-emitting element, etc. The data input unit 110 is composed of a camera 120 that captures the scenery in front of the HMD 100, a microphone that inputs sound, and an operation input unit for inputting user operations.

[0064] Figure 3 2 is a block diagram showing the internal structure of the battery 200. The battery 200 is composed of a control unit 204, a communication unit 205, a memory unit 206, a charge state recognition unit 207, a power storage unit 208, and a display unit 209. The control unit 204 controls the overall operation of the battery 200.

[0065] The communication unit 205 includes a wireless LAN and Bluetooth (registered trademark) for wireless communication with the HMD 100 and the charger 300. The memory unit 206 stores information on the internal state of the battery 200 and can also store image data to be displayed on the HMD 100.

[0066] The battery state recognition unit 207 detects the remaining charge or charge level of the battery and stores this information. The battery storage unit 208 includes a power transmission and reception unit 203 that transmits and receives power between the battery unit 201 (composed of storage elements), the conversion unit 202, the HMD 100, and the charger 300. The power transmission and reception unit 203 includes a power transmission and reception coil for wirelessly transmitting and receiving power. The display unit 209 is an LED 215 that displays the battery charge level in different colors.

[0067] In the following description, the battery 200 is categorized as 200a to 200d according to its usage state (while being used in the HMD, while being charged in the charger) (the internal structure of the battery is also categorized similarly).

[0068] Figure 4300 is a block diagram showing the internal structure of the charger 300. The charger 300 is composed of a control unit 301, a communication unit 302, a memory unit 303, a charging battery monitoring unit 304, a display unit 305, and a power supply unit 306. The control unit 301 controls the overall operation of the charger 300.

[0069] The communication unit 302 includes a wireless LAN and Bluetooth (registered trademark) for wireless communication with the HMD 100 and the battery 200. Furthermore, the communication unit 302 may include a GPS-based position information acquisition function and a "One-Seg" function.

[0070] The memory unit 303 stores information on the internal state of the charger 300 and information on the state of charge of the battery 200 , and can also store image data to be displayed on the HMD 100 .

[0071] The charging battery monitoring unit 304 obtains information on the charge level of the charging battery 200. The display unit 305 is an LED that displays the start and completion of battery charging in different colors.

[0072] The power supply unit 306 includes a storage battery unit 307 that supplies power to the battery 200, a conversion unit 308, and a power transmission unit 309. The power transmission unit 309 includes a power transmission coil that wirelessly transmits power. The number of display units 305 and power supply units 306 corresponds to the number of charging slots 311.

[0073] Here, the battery unit 307 of the power supply unit 306 can be charged by an external power source. Furthermore, an external power source can be used in conjunction with the HMD 100 depending on how the HMD 100 is used. When using the HMD 100 while sitting in one place for an extended period of time, such as while watching a movie, the power supply unit 306 can be connected to an external power source such as mains electricity. On the other hand, when carrying the HMD 100, the HMD's battery 200 can be charged using the charged battery unit 307.

[0074] exist Figures 2 to 4 In the figure, the power transmission unit / power reception unit includes a power transmission coil / power reception coil, and the communication unit includes an antenna, but their illustration is omitted for simplicity.

[0075] Figure 5A and Figure 5B : is a diagram illustrating power transmission between the HMD 100, the battery 200, and the charger 300. Figure 5A Indicates the power transmission between the HMD 100 and the batteries 200a and b in use. Figure 5B It shows the power transmission between the battery 200 c being charged and the charger 300 .

[0076] exist Figure 5AThe HMD 100 can be equipped with multiple (here, two) batteries 200a and 200b, each of which can supply power. Direct current flows from the battery storage units 201a and 201b and is converted by the conversion units 202a and 202b into, for example, 150kHz alternating current. Power is then wirelessly transmitted to the HMD 100 from the power transmission units 203a and 203b (power transmission coils).

[0077] HMD 100 includes multiple power receiving units 102a and 102b (power receiving coils) that receive power wirelessly transmitted from batteries 200a and 200b at a frequency of, for example, 150 kHz. Converters 103a and 103b convert the received AC current into a specified DC current. Limiters 104a and 104b supply DC current to the control unit 101, limiting the supplied power based on the power usage of the load within HMD 100. Therefore, the control unit 101 sends a control signal to the limiter 104 to implement power limitation based on the power usage of the load, although this is not shown in the figure.

[0078] The use of the multiple batteries 200a, 200b in HMD 100 can be configured by selecting the control flow of control unit 101. For example, batteries with less remaining power can be prioritized. Furthermore, by configuring the power receiving units 102a, b and the conversion units 103a, b to enable bidirectional power transmission and conversion, one power receiving unit, such as 102a, can be configured to always have battery 200a installed, while the other power receiving unit 102b is used exclusively for battery replacement. This also enables a configuration in which battery 200b installed in power receiving unit 102b provides the power required for HMD 100 operation while simultaneously storing power in battery 200a. In this case, even if one hand becomes unusable for some reason, HMD 100 can still be worn for extended periods of time—exceeding the capacity of a single battery.

[0079] By having multiple batteries in this manner, when a battery is replaced, the remaining battery can be used as the power source for HMD 100, allowing the HMD to continue to be used even during battery replacement. Furthermore, the internal battery of HMD 100's power management unit 106 can also be utilized. While the internal battery has a smaller capacity than the installed batteries 200a and 200b, by ensuring that the battery capacity is sufficient to keep HMD 100 fully operational during battery replacement, the HMD can continue to be used even during battery replacement. However, if the battery cannot be replaced within the specified time, HMD 100 itself will be shut down to ensure data security, etc.

[0080] Figure 5BThis figure shows the power transfer (charging operation) from the charger 300 to the battery 200c. In the power supply unit 306 of the charger 300, the DC current generated by the storage battery unit 307 is converted to AC current by the conversion unit 308. This current is then wirelessly transmitted from the power transmission unit 309 (power transmission coil) to the charging battery 200c. In the storage unit 208 of the battery 200c, the power transmitted from the charger 300 is received by the power receiving unit 203c (power receiving coil). The power is then converted to DC by the conversion unit 202c and stored in the storage battery unit 201c.

[0081] Figure 6A and Figure 6B 1 is a diagram illustrating the communication between the HMD 100, the battery 200, and the charger 300. Figure 6A Indicates the communication regarding the battery 200a (200b) in use, Figure 6B Indicates communication regarding the battery 200c being charged.

[0082] exist Figure 6A The communication unit 108 of the HMD 100 wirelessly communicates with the communication unit 205a of the battery 200a (200b) in use, and the power management unit 106 of the HMD 100 obtains the remaining battery power information obtained by the charge state identification unit 207a of the battery 200a (200b) in use. Furthermore, the communication unit 108 of the HMD 100 wirelessly communicates with the communication unit 302 of the charger 300, transmitting the remaining battery power information obtained by the HMD 100. Furthermore, based on the power usage status of the load within the HMD 100, the communication unit 108 of the HMD 100 transmits a control command, such as a command to stop power transmission, to the battery 200a (200b) in use from the control unit 101.

[0083] exist Figure 6B The communication unit 302 of the charger 300 wirelessly communicates with the communication unit 205c of the battery 200c being charged, and the charging battery monitoring unit 304 of the charger 300 obtains information on the charge state of the battery 200c (charge level) obtained by the charge state identification unit 207 of the battery 200c. Furthermore, the communication unit 108 of the HMD 100 wirelessly communicates with the communication unit 302 of the charger 300, and the power management unit 106 of the HMD 100 obtains information on the charge state of the battery 200c being charged. Furthermore, the communication unit 108 of the HMD 100 transmits control commands such as charging start / stop from the control unit 101 to the charger 300 based on the remaining charge of the batteries 200a and b being used and the power usage status of the loads within the HMD 100. The charger 300 then controls the charging battery 200c according to these commands.

[0084] In this manner, the HMD 100 and the charger 300 communicate with each other to transmit information on the remaining power of the batteries 200 a and b in use and the state of charge of the battery 200 c being charged, and store the information in the respective memory units 105 and 303 .

[0085] Figure 7A and Figure 7B An example of a display of the battery status displayed on the display 119 of the HMD 100 is shown.

[0086] Figure 7A This is an example of displaying various function menus of the HMD on the display 119. The user selects a battery-related menu 701 from the menu panel. In order to check the battery status, the menu 701 is activated or kept activated.

[0087] Figure 7B This is an example of displaying the battery status on display 119. The left display 119a displays a warning prompting battery replacement, while the right display 119b shows information about the charge level of the batteries in each charging slot. When the remaining battery charge is low, a warning message "Left battery remaining low" prompting the user to replace the battery is automatically displayed on the left-eye display 119a of the HMD 100. To avoid user misunderstanding, the warning is displayed on the battery with the lowered remaining charge. When this display is displayed, the user replaces the left battery.

[0088] At this time, the right-eye display 119b on the opposite side displays the charge level of the batteries currently being charged in each slot using bar graphs. This display example shows that the battery in slot number 2 has the highest charge level, and the slot number and bar graph for slot 2 flash. Simultaneously, the charger 300 flashes the green LED for battery charging slot 311b (number 2), and the LED for battery 200 also flashes green. After this display, the user can remove the battery currently being charged in charging slot 311b and install it in the HMD.

[0089] According to the configuration of Example 1, the user can replenish power by replacing the battery while wearing the HMD 100, allowing continued use of the HMD without interruption. This ability to replace the battery while the device is in use is called "hot swapping." Furthermore, power transmission from the battery 200 to the HMD 100 and from the charger 300 to the battery 200 is performed wirelessly over short distances, making it easy to deliver the required power. Furthermore, because the battery 200 employs a structure in which the metal terminals are not exposed to the outside, even when the HMD is worn on the user's head, there are no issues with corrosion from sweat or short circuits between the terminals during battery replacement, ensuring safe use. For example, when the user is watching a long movie, the added battery does not affect the wearing experience, and there is no need to connect a power supply cable from the terminals of the wearable device to an external power source, thereby improving user convenience.

[0090] Here, as a modification of the first embodiment, a configuration for downloading large-volume data from the cloud using the power supply system of this embodiment will be described.

[0091] Figure 8 : is a diagram showing data transmission between the power supply system of this embodiment and the cloud 600. The power supply system is composed of the HMD 100, the battery 200a being used (worn) in the HMD, the charger 300, and the battery 200c being charged in the charger.

[0092] Data transmission between HMD 100 and cloud 600 includes downloading image data from cloud 600 for viewing on HMD 100 (reference numeral 601a) and uploading image data acquired by HMD 100's data input unit 110 (camera 120) to cloud 600 (reference numeral 601b). In either case, data is transmitted directly between HMD 100 and cloud 600, which can lead to time-consuming transmission of large amounts of data, such as movies, and potentially insufficient battery capacity. Therefore, in the configuration of this embodiment, data transmission is performed via the charging battery 200, utilizing its charging time.

[0093] The communication unit 302 of the charger 300 downloads data from the cloud 600 and stores it in the memory 206c of the battery 200c being charged. When the HMD 100 uses the fully charged battery 200c, it reads and views the data stored in the memory 206a of the battery 200a being used (path indicated by reference numeral 602a). Conversely, data generated by the HMD 100 is stored in the memory 206 of the battery 200a being used, using the memory unit 105 as a buffer. When the battery is being charged by the charger 300, the stored data is read from the memory 206c of the battery 200c and uploaded to the cloud 600 via the communication unit 302 of the charger 300 (path indicated by reference numeral 602b). In this way, the HMD 100 utilizes the memory of the battery 200 being charged to transfer data between the cloud 600 and the HMD 100, enabling efficient transmission of large amounts of data.

[0094] Example 2

[0095] Embodiment 2 describes a structure for realizing replacement of the battery of the HMD while the HMD is in use, that is, a hot swap function.

[0096] Figure 9 2 is a diagram showing the control of power transmission between the HMD and the battery. In the illustrated configuration, the HMD 100 is equipped with a plurality of batteries 200a and 200b, and switches between them.

[0097] In HMD 100, the limiting units 104a and 104b are provided with a backflow prevention diode D, a current detection resistor R, a MOS field effect transistor (MOSFET) M1, and a charge storage capacitor C on the power lines supplied from the respective batteries 200a and b. The control unit 101 controls the MOSFET (M1) on and off to cut off the power received from the battery 200.

[0098] Furthermore, the power management units 106a and 106b of the HMD 100 include amplifiers and frequency counters 121a and b, which detect whether the battery 200 has been removed from the HMD 100. When the battery 200 is removed (detached), the resonant frequency of the wireless power supply from the power receiving units 102a and b fluctuates. Therefore, the frequency counter 121 monitors the resonant frequency to detect battery removal.

[0099] Meanwhile, in batteries 200a and 200b, MOS field-effect transistors (MOSFETs) M2a and M2b are provided between the battery sections 201a and 200b within the power storage units 208a and 208b and the conversion units 202a and 202b. Control units 204a and 204b control MOSFETs (M2) to limit the current flowing from the battery sections 201a and 200b to the conversion units 202a and 202b. Furthermore, the remaining charge of battery 200 is determined by the charge state identification units 207a and 207b measuring the voltage VB between the terminals of the battery sections 201a and 200b.

[0100] The following describes the procedure for replacing the battery in an HMD.

[0101] Figure 10 This is a flowchart showing a process in which a battery in use is removed from the HMD due to insufficient remaining power.

[0102] The battery 200 in use has the voltage VB (remaining power) between the terminals of the battery unit 201 read by the charging state recognition unit 207, and is transmitted to the HMD 100 through communication with the HMD 100 (S101). The HMD 100 compares the received voltage VB with a pre-set first threshold value Vth1 (S102). If the voltage VB is greater than the threshold value Vth1, the battery can continue to be used, so the process returns to S101. However, if the voltage VB is less than the threshold value Vth1, a warning such as "low remaining battery power" is displayed on the display 119 of the HMD 100 (S103). Specifically, if Figure 7B As shown, a warning is displayed on the display 119a on the battery side where the remaining power is decreasing.

[0103] If the battery 200 is further used, the battery 200 reads the inter-terminal voltage VB and communicates this voltage (S104). The HMD 100 compares the received voltage VB with a pre-set second threshold value Vth2 (where Vth2 < Vth1) (S105). While the voltage VB is greater than the threshold value Vth2, the battery can continue to be used, so the process returns to S104. However, if the voltage VB is less than the threshold value Vth2, the battery is removed.

[0104] HMD 100 turns off MOSFET (M1) of limiting unit 104 (S106) to prevent reverse current from flowing to battery 200. Furthermore, it instructs the battery 200 in use to turn off MOSFET (M2), stopping the flow of current from storage unit 201 (S107). At this stage, a warning message "Please replace battery" is displayed on the display 119 of HMD 100 on the side of the battery with low remaining power (S108).

[0105] The user removes the battery 200 from the HMD 100 ( S109 ), and the communication between the battery 200 and the HMD 100 is disconnected ( S110 ).

[0106] For safety reasons, a third threshold value Vth3 may be set instead of the two threshold values ​​Vth1 and Vth2 to maintain a power reserve of approximately 10%, so that the user can replace the battery when the battery still has a sufficient power reserve.

[0107] Figure 11 This is a flowchart showing a process of switching from the battery in use to the battery in standby mode when the remaining power of the battery in use is insufficient. Here, an example of switching from the left battery 200a to the right battery 200b is described.

[0108] The voltage VB (remaining capacity) between the terminals of the battery unit 201a of the battery 200a in use is read and compared with the first threshold value Vth1 and the second threshold value Vth2 (S201 to S205). The process so far is the same as that of Figure 10 Then, if the voltage VB is lower than the threshold value Vth2 ("Yes" in S205), the battery 200a is switched to the battery 200b.

[0109] First, the control unit 101 of the HMD 100 turns off the MOSFET (M1a) of the limiting unit 104a on the active battery 200a side, and further turns off the MOSFET (M2a) of the active battery 200a, stopping the flow of current from the storage battery unit 201a (S206). Next, the control unit 101 turns on the MOSFET (M1b) of the limiting unit 104b on the standby battery 200b side, and further turns on the MOSFET (M2b) of the standby battery 200b, restarting the flow of current from the storage battery unit 201b (S207). This switches the power receiving system from the battery 200a to the battery 200b. During this switching period, power for the HMD 100 is supplied by the power stored in the capacitor Ca of the limiting unit 104a and the internal battery of the HMD 100. This prevents interruption of HMD 100 operation due to battery switching.

[0110] Thereafter, a warning message "Please replace the battery" is displayed on the display 119a on the left side of the HMD 100 (S208). The user removes the battery 200a (S209), and the communication between the battery 200a and the HMD 100 is disconnected (S210).

[0111] Figure 12 This is a flowchart showing the process of cutting off the power supply when the battery is detached from the HMD. It describes not only the process of replacing the battery, but also the process of cutting off the power supply when the battery is detached for some reason.

[0112] HMD 100 monitors the resonant frequency FR of the power receiving unit 102 (power receiving coil) using the frequency counter 121 of the power management unit 106 (S301). When the battery 200 in use is removed from the power receiving unit 102 or deviates from a predetermined position, the resonant frequency FR fluctuates. If the frequency counter 121 detects this frequency fluctuation ("Yes" in S302), the control unit 101 of HMD 100 turns off the MOSFET (M1) of the limiting unit 104 (S303). Furthermore, the communication unit 108 of HMD 100 communicates with the battery 200 to turn off the MOSFET (M2) of the battery 200, thereby stopping the flow of current from the battery unit 201 (S304). At this stage, a "Battery Disconnected" warning is displayed on the display 119 of HMD 100, located on the side of the disconnected battery (S305).

[0113] According to the second embodiment, when the battery of the HMD 100 is replaced, the user can continue to use the HMD 100 without interrupting its operation, and a hot swap function can be realized.

[0114] Example 3

[0115] In the third embodiment, a structure of the battery 200 suitable for being mounted on the HMD 100 or the charger 300 will be described.

[0116] Figure 13 This diagram shows the process of installing the battery 200 in the HMD 100 and charger 300. Multiple magnets 111a, 111b, and 111c are mounted on the battery mounting surface of the power receiving unit 102 of the HMD 100. Multiple magnets are mounted here, but a single magnet is also acceptable. Furthermore, ferrites of the same shape are mounted on the battery 200. These magnets and ferrites are used to align the power transmission and reception coils between the HMD 100 and the battery 200, and to reduce magnetic field leakage. Meanwhile, the charger 300 is also equipped with magnets of the same shape to align the power transmission and reception coils between the charger 300 and the battery 200, and to reduce magnetic field leakage.

[0117] Figure 14 This diagram shows an example of the power system circuit within battery 200. Battery 200 consists of a storage battery unit 201, a conversion unit 202, and a power transmission and reception unit 203. Conversion unit 202 is a bidirectional converter for DC / AC conversion, and coil 203L of power transmission and reception unit 203 can be used for both power transmission and power reception. The battery structure is described in detail below.

[0118] Figure 15The figures show an example of the internal structure of the battery 200. (a) shows a perspective view of the battery cover on the upper side of the outer casing 214, and (b) shows a cross-sectional view taken along the line α-α'. As shown in (b), the battery unit 201, the circuit board 213, and the ferrite plate 211 are mounted in the outer casing 214, which is made of, for example, resin. Ferrite cylinders 212a, 212b, and 212c, and the coil 203L are mounted on the ferrite plate 211.

[0119] Figure 16 The figures show the battery 200 installed in the HMD 100. (a) shows the battery installed in the HMD, and (b) and (c) are β-β' cross-sectional views. In (b), the temple portion 114 of the HMD 100 completely covers the upper and lower surfaces of the battery housing 214, while in (c), the temple portion 114 partially retains the battery housing 214 at its lower portion. In (c), the ferrites 212 and 211 of the battery 200 are attracted by the magnet 111 of the HMD 100, thereby securing the battery 200.

[0120] In (b) and (c), magnet 111 is placed on ferrite plate 113 at power receiving unit 102 of HMD 100, along with coil 102L. Magnet 111 and ferrite cylinder 212 of battery 200 enable alignment of coil 102L of HMD 100 with coil 203L of battery 200. Furthermore, during power transmission, the magnetic field generated by coil 203L passes through ferrite plates 211 and 113, magnet 111, and ferrite cylinder 212, thereby reducing magnetic field leakage.

[0121] Figure 17 Figures 200 and 201 illustrate another example of the internal structure of the battery 200. (a) shows the battery cover on the upper side of the outer casing 214 through a perspective view, and (b) shows a cross-sectional view taken along the line α-α'. In this example, two sets of coils 203L and ferrites 211 and 212 are located on either side of the outer casing 214 of the battery 200. After the battery 200 is installed, the coil 203L and ferrites 211 and 212 located closer to the power receiving unit 102 of the HMD 100 can be used. This eliminates the need for the user to determine which side is the correct installation side when installing the battery 200.

[0122] Figure 18 Yes Figure 17 FIG2 shows a modified example of a battery 200. In this example, the ends of two coils 203L arranged on either side of the housing 214 are connected to form a single coil. In other words, a single coil is folded approximately in the middle and arranged on both sides of the housing 214. In this case, the battery 200 also has a symmetrical structure, making it easier to attach to the HMD 100 and install it in the charger 300.

[0123] Figure 19 This figure shows the structure of the charger 400 that charges the battery 200 mounted on the HMD 100. The operation of the charger 400 is the same as that of the charger 300 in the first embodiment. However, this figure is used to illustrate the structure of the charging unit and other structures such as the circuit board in the charger are omitted. Here, the battery 200 adopts Figure 17 The structure of FIG. 1 shows a state where the HMD 100 with the battery 200 mounted thereon is placed on the charger 400. The cross-sectional shape of the temple portion 114 of the HMD 100 is Figure 16 The shape shown in (b) in the figure. (a) is a view from above, (b) is a γ-γ' cross-sectional view, and (c) is a partially enlarged view.

[0124] The charger 400 has a central raised portion 401 and two raised charging sections 402a and 402b on either side. The temples 114 of the HMD 100 are housed between 401 and 402a and b. As shown in the enlarged view (c), a power transmission coil 403L and a magnet 411 for battery charging are located on the inner wall of the charging section 402a, on a ferrite plate 413.

[0125] In the battery 200 mounted on the temple portion 114 of the HMD 100, the coil 203L on the left side of the figure is opposite to the coil 403L of the charger 400. The coil 203L of the battery 200 is a coil used for both power transmission and power reception, and can charge the battery 200 from the coil 403L of the charger 400. In addition, through the attraction between the magnet 411 of the charger 400 and the ferrite cylinder 212 of the battery 200, the coil 403L of the charger 400 and the coil 203L of the battery 200 are automatically aligned, and sufficient power transmission efficiency can always be obtained. In addition, during power transmission, the magnetic field generated by the coil 403L passes through the ferrite plates 413, 211, the ferrite cylinder 212, and the magnet 411, so that the magnetic field leakage is small. For example, the battery 200 can be fully charged by simply leaving the HMD 100 on the charger 400 overnight. In addition, using Figure 8 The structure can download the required movie and other data from the cloud 600.

[0126] According to the structure of the third embodiment, it is easy to attach the battery 200 to the HMD 100 and the charger 300, and the power transmission efficiency is improved. Figure 19 With the structure, the battery 200 can be easily charged while being mounted on the HMD 100.

[0127] Example 4

[0128] In the fourth embodiment, a configuration is described in which power can be supplied directly to the HMD not only from a battery but also from a charger.

[0129] Figure 20A This diagram shows the configuration of a power supply system in Example 4, capable of supplying power to the HMD from both batteries and chargers. This example illustrates the flow of power when power is supplied to the HMD 100 from two batteries 200a and 200b, and also from two chargers 500a and 500b in addition to the batteries. While two chargers are used here, any number is possible, and a configuration in which multiple chargers are integrated can also be employed.

[0130] In the batteries 200a and 200b, direct current flows from the battery unit 201, is converted into alternating current by the conversion unit 202, and is wirelessly transmitted from the power transmission unit 203 to the HMD 100 at a frequency of, for example, 150 kHz. Figure 5A On the other hand, the chargers 500c and 500d also include a battery unit 501, a conversion unit 502, and a power transmission unit 503, and similarly, the power transmission unit 503 transmits power to the HMD 100 wirelessly.

[0131] HMD 100 has four power receiving units 102a, 102b, 102c, and 102d. When power is supplied from batteries 200a and 200b, the power receiving system of power receiving units 102a and 102b is used. When power is supplied from charger 500, the power receiving system of power receiving units 102c and 102d is used. In each power receiving system, after receiving power from power receiving unit 102, conversion unit 103 converts the power into a specified DC current. Limiting unit 104 limits the amount of power received based on the power usage of loads such as communication unit 108, which is controlled by control unit 101. Furthermore, by enabling bidirectional power conversion and transmission between conversion unit 103 and power receiving unit 102, batteries 200a and 200b can be charged using power supplied from chargers 500c and 500d.

[0132] Figure 20B Yes Figure 20A FIG1 is a diagram showing a specific application example of the power supply system. This is an example of a driver using an HMD. Batteries 200a and 200b are installed on the temples of the HMD. On the other hand, the power transmission units 503c and 503d of the chargers 500c and 500d are arranged, for example, on the headrest of the seat. The power receiving units 102c and 102d of the HMD 100, which receive power from the power transmission units 503c and 503d, are arranged in a bilaterally symmetrical manner on the temples near the headrest, such as the leg covers. When the driver is sitting in the seat, the charger 500 is used for power supply first, and the battery 200 can also be charged. Once the driver leaves the seat, power is switched to the battery 200.

[0133] According to the structure of the fourth embodiment, it is possible to continuously use the HMD for a long time (exceeding the battery capacity) using a single battery while the HMD is being worn.

[0134] In the above-described embodiments, the power supply structure is described by taking a glasses-type head-mounted display (HMD) as an example, but the present invention is of course not limited to this and can be similarly applied to other wearable devices.

[0135] Description of Reference Signs

[0136] 100: Head-mounted display (HMD), 101: Control unit, 102: Power receiving unit, 102L: Coil, 103: Converter, 104: Limiter, 105: Memory, 106: Power management unit, 107: Sensor, 108: Communication, 109: Data output, 110: Data input, 111: Magnet, 113: Ferrite plate, 114: Temple, 115: Infrared sensor, 116: Strain sensor, 119: Display, 120: Camera, 121: Frequency counter,

[0137] 200: Battery, 201: Storage battery unit, 202: Conversion unit, 203: Power transmission and reception unit, 203L: Coil, 204: Control unit, 205: Communication unit, 206: Memory unit, 207: Battery state recognition unit, 208: Storage unit, 209: Display unit, 211: Ferrite plate, 212: Ferrite cylinder, 213: Circuit board, 214: Housing, 215: LED,

[0138] 300: Charger, 301: Control unit, 302: Communication unit, 303: Memory unit, 304: Battery monitoring unit during charging, 305: Display unit, 306: Power supply unit, 307: Storage battery unit, 308: Conversion unit, 309: Power transmission unit, 311: Battery charging slot, 312: Battery slot number,

[0139] 400: charger, 401: raised portion, 402: charging portion, 403L: coil, 411: magnet, 413: ferrite plate, 500: charger, 600: cloud.

Claims

1. A wearable device that can be worn by a user, characterized in that: include: a plurality of power receiving units capable of mounting at least a first battery and a second battery and receiving power from the first battery and the second battery by wireless transmission; a power management unit that monitors the status of the first and second batteries installed; a communication unit for wirelessly communicating with the first battery and the second battery installed; displays that provide information to users; a plurality of limiting units for limiting the electric power received by the plurality of power receiving units; and a control unit that controls the power receiving unit, the power management unit, the communication unit, the display, and the restriction unit, wherein: The power management unit obtains information about the remaining power of the first battery and the second battery installed through the communication unit, and displays the obtained information about the remaining power on the display. The control unit limits the supplied power through the limiting unit according to the power usage status of the load in the wearable device or the information on the remaining power of the first battery and the second battery.

2. The wearable device according to claim 1, wherein: When the power management unit determines that the remaining power of the first battery in use is less than a threshold, the power receiving system is switched from the first battery in use to the second battery in standby mode, and A warning is displayed on the display to remind the user to replace the first battery in use.

3. The wearable device according to claim 1 or 2, wherein: The power management unit includes a frequency counter that monitors the resonance frequency between the coils between the power receiving unit and the first battery in use. When the resonant frequency monitored by the frequency counter fluctuates, the control unit determines that the first battery in use is detached from the power receiving unit, and displays a warning on the display to inform a user that the first battery in use is detached.

4. The wearable device according to claim 3, wherein: When the control unit determines that the remaining power of the first battery in use is less than a threshold value, or when the control unit determines that the first battery in use has been disconnected from the power receiving unit, the control unit sends a control command to the first battery in use through the communication unit to stop power transmission to the wearable device.

5. The wearable device according to claim 1, wherein: The communication unit can also wirelessly communicate with a charger that is charging a third battery, obtain the charging state information of the third battery from the charger, and display the obtained charging state information on the display. The control unit transmits a control command for a charging operation of the third battery being charged to the charger via the communication unit.

6. The wearable device according to claim 1, wherein: The power management unit compares the remaining power levels of the first battery and the second battery, and limits the power supplied by the limiting unit to the battery with the larger remaining power level.

7. The wearable device according to claim 2, wherein: include: a first sensor configured to detect an object approaching the vicinity of the first battery; and a second sensor for detecting an object approaching the vicinity of the second battery, When the second sensor detects an approach of an object, the control unit displays a warning on the display to remind the user not to remove the second battery in standby mode.

8. The wearable device according to claim 1, wherein: The wearable device includes an external power receiving unit that receives power from an external charger via wireless transmission. The first and second batteries mounted thereon are charged using the electric power received by the external power receiving unit.

9. A wearable device that can be worn by a user, characterized in that: include: a display for providing information to said user; A plurality of power receiving units capable of mounting a first battery and a second battery on the left and right sides of the display, respectively, as viewed from a user wearing the wearable device, and receiving power from the first battery and the second battery by wireless transmission; a power management unit that monitors the status of the first and second batteries installed; a communication unit for wirelessly communicating with the first battery and the second battery installed; a plurality of limiting units for limiting the electric power received by the plurality of power receiving units; and a control unit that controls the power receiving unit, the power management unit, the communication unit, the display, and the restriction unit, wherein: The power management unit obtains information about the remaining power of the first battery and the second battery installed through the communication unit. When the control unit determines that the remaining power of the first battery in use is less than a threshold value, the control unit switches the power receiving system from the first battery in use to the second battery in standby, and displays a warning on the left side of the display to remind the user to replace the first battery in use.

10. The wearable device according to claim 9, wherein: When the control unit determines that the remaining power of the second battery in use is less than a threshold value, the control unit switches the power receiving system from the second battery in use to the first battery in standby mode, and displays a warning on the right side of the display to remind the user to replace the second battery in use.

11. A wearable device that can be worn by a user, characterized in that: include: a display for providing information to said user; A plurality of power receiving units capable of mounting a first battery and a second battery on the left and right sides of the display, respectively, as viewed from a user wearing the wearable device, and receiving power from the first battery and the second battery by wireless transmission; a power management unit that monitors the status of the first and second batteries installed; a communication unit for wirelessly communicating with the first battery and the second battery installed; a plurality of limiting units for limiting the electric power received by the plurality of power receiving units; and a control unit that controls the power receiving unit, the power management unit, the communication unit, the display, and the restriction unit, wherein: The power management unit obtains information about the remaining power of the first battery and the second battery installed through the communication unit. When the control unit determines that the remaining power of the second battery in use is less than a threshold value, the control unit switches the power receiving system from the second battery in use to the first battery in standby mode, and displays a warning on the right side of the display to remind the user to replace the second battery in use.

12. The wearable device according to any one of claims 9 to 11, wherein: The communication unit further wirelessly communicates with a third battery or a charger that is charging the third battery, and obtains the charge state information of the third battery being charged from the third battery or the charger. The control unit displays information indicating a charge amount of the third battery on the display based on the charge state information.

13. The wearable device according to any one of claims 9 to 11, wherein: The communication unit further wirelessly communicates with a third battery or a charger that is charging the third battery, and obtains the charge state information of the third battery being charged from the third battery or the charger. The control unit displays information on the display that allows identification of the third battery having the largest charge capacity based on the charge state information.

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