Power transmitting apparatus, control method of the same and storage medium

A power transmitting apparatus which can be driven by a battery and transmits power to one or more power receiving apparatuses acquires, from each of one or more power receiving apparatuses, information for identifying the power receiving apparatus, and decides the amount of transmission power for each of one or more power receiving apparatuses based on the remaining capacity of the battery and the sum of the allowable amounts of transmission power determined for each of one or more power receiving apparatuses based on the information. The power transmitting apparatus transmits power to one or more power receiving apparatuses in accordance with the decided power amount.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a wireless power transfer technique.

Description of the Related Art

Recently, the development of techniques of wireless power transfer systems is being extensively made. A power transfer system in which a power transmitting apparatus transmits power to a plurality of power receiving apparatuses is described in Japanese Patent Laid-Open No. 2011-019291. Japanese Patent Laid-Open No. 2011-019291 describes that charging is rapidly completed by prolonging the power transmission time for a power receiving apparatus having a high priority level based on priority level information of each power receiving apparatus.

When the power transmitting apparatus is driven by a battery, the battery remaining capacity of the power transmitting apparatus decreases in accordance with power transmission to the plurality of power receiving apparatuses, and a transmittable power amount also decreases. In this case, if the power transmitting apparatus keeps transmitting power to a given power receiving apparatus, it becomes impossible to transmit power to other power receiving apparatuses. If there is a power receiving apparatus for which power transmission is desirably preferentially performed, the battery remaining capacity is reduced by power transmission to other power receiving apparatuses, and this makes it impossible to transmit power to the preferential power receiving apparatus.

The present invention has been made in consideration of the above problem, and controls the amount of transmission power for each power receiving apparatus in accordance with the battery remaining capacity.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, there is provided a power transmitting apparatus drivable by a battery and including a power transmitting unit configured to transmit power to not less than one power receiving apparatus, comprising: an acquisition unit configured to acquire information for identifying each of the not less than one power receiving apparatus; and a decision unit configured to decide an amount of transmission power for each of the not less than one power receiving apparatus, based on a remaining capacity of the battery and an upper limit value of transmission power determined based on the information for each of the not less than one power receiving apparatus, wherein the power transmitting unit transmits power to the not less than one power receiving apparatus in accordance with the decided power amount.

DESCRIPTION OF THE EMBODIMENTS

First Embodiment

System Configuration

FIG. 1shows a configuration example of a wireless power transfer system according to this embodiment.FIG. 1shows a system in which one power transmitting apparatus100transmits power to three power receiving apparatuses101to103. Each of the power transmitting apparatus and power receiving apparatuses holds an apparatus ID as information for identifying the apparatus and user information of the apparatus. InFIG. 1, the power transmitting apparatus100has “1” as the apparatus ID, and “A” as the user information. Likewise, the power receiving apparatus101has apparatus ID “2” and user information “A”, the power receiving apparatus102has apparatus ID “3” and user information “B”, and the power receiving apparatus103has apparatus ID “4” and user information “A”. In the following description, the power receiving apparatuses101,102, and103will be expressed as apparatuses 2, 3, and 4, respectively. Note that in this embodiment, a case in which a plurality of power receiving apparatuses exist for one power transmitting apparatus100will be explained. However, the technique to be explained below can be applied to an arbitrary case in which one or more power receiving apparatuses exist for one power transmitting apparatus100.

(Arrangement of Power Transmitting Apparatus)

FIG. 2is a block diagram showing a functional arrangement example of the power transmitting apparatus100according to this embodiment. A classification unit200classifies the power receiving apparatuses based on the user information of the power receiving apparatuses. In this embodiment, the classification unit200classifies a power receiving apparatus having the same user information as that of the power transmitting apparatus as an apparatus represented by identifier “1”, and a power receiving apparatus having other user information as an apparatus represented by identifier “0”. In the example shown inFIG. 1, the classification unit200classifies the power receiving apparatuses having user information A (apparatuses 2 and 4) as apparatuses represented by identifier “1”. On the other hand, the classification unit200classifies the power receiving apparatus having user information B (apparatus 3) as an apparatus represented by identifier “0”.

Note that the classification unit200may also use another classification method such as a method of classifying a power receiving apparatus having preregistered predetermined user information as an apparatus represented by identifier “1”, and a power receiving apparatus having other user information as an apparatus represented by identifier “0”. Also, when the power transmitting apparatus is installed in a store, the user information may be information indicating whether registration pertaining to services provided by the store in which the power transmitting apparatus is installed or by a store management group has been performed. Note that the classification unit200may also classify a power receiving apparatus based on the apparatus ID of the power receiving apparatus. The apparatus ID may also be an information element by which the name of a standard with which the power receiving apparatus complies and version information of the standard can be recognized.

In the following explanation, after the power receiving apparatuses are classified, the amount of transmission power to each power receiving apparatus is decided based on the upper limit value of transmission power, which is decided in accordance with the classification, and the remaining capacity of a battery. However, this classification may also be omitted. That is, it is also possible to identify power receiving apparatuses, decide the upper limit value of transmission power for each power receiving apparatus, and decide the amount of transmission power to each power receiving apparatus in accordance with the upper limit value and the remaining capacity of the battery. Furthermore, the user may input information of a power receiving apparatus via an operation unit (not shown) of the power transmitting apparatus, and may also input the upper limit value of transmission power to the power receiving apparatus at the same time. In any case, the power transmitting apparatus sets the upper limit value of transmission power for each power receiving apparatus, and decides the amount of actual transmission power based on the upper limit value and the remaining capacity of the battery.

A transmission power amount storage unit201stores the upper limit values of transmission power amounts, which are based on the class classified by the classification unit200. A determination unit202first determines whether it is possible to perform power transmission using the transmission power amount upper limit values stored in the transmission power amount storage unit201, based on the transmission power amount upper limit values corresponding to the class and the remaining capacity of a battery208of the power transmitting apparatus. The determination unit202also determines whether the transmission power amount decided for each power receiving apparatus by each processing (to be described later) is appropriate, based on the sum of the transmission power amounts and the battery remaining capacity. Then, in accordance with this determination result, the determination unit202determines whether to increase or reduce the transmission power amount for each power receiving apparatus. A determination storage unit203stores information to be used in the above-described determination by the determination unit202. For example, the determination storage unit203stores information such as the total amount of power to be transmitted, the battery remaining capacity, and the expected remaining capacity of the battery, which remains after power transmission.

Based on the determination by the determination unit202, a distribution unit204increases or reduces the transmission power amounts to the power receiving apparatuses, and distributes the transmission power within the range of power transmittable to one or more power receiving apparatuses. A distribution storage unit205stores the increased/reduced amount of transmission power as a result of the distribution by the distribution unit204, for each power receiving apparatus, for each class classified by the classification unit200, and for the whole system. A power transmission management unit206manages the transmission power amount decided for each of one or more power receiving apparatuses, and the transmitted power amount.

A control storage unit207stores information functioning as triggers by which the determination unit202and distribution unit204start processing. The determination unit202and distribution unit204monitor the control storage unit207. The battery208functions as a power supply for driving the power transmitting apparatus100, and also supplies power to be transmitted to one or more power receiving apparatuses. A power transmitting unit209has, e.g., an interface for transmitting power to a power receiving apparatus, and the power transmitting apparatus transmits power to one or more power receiving apparatuses via the power transmitting unit209.

(Information to be Stored in Transmission Power Amount Storage Unit201)

FIG. 3shows examples of information to be stored in the transmission power amount storage unit201. A class300is a class identifier when the classification unit200classifies a power receiving apparatuses. A transmission power amount301is the upper limit value of the transmission power amount for each class. As will be described in detail later, when the battery remaining capacity is sufficient and presumably equal to or larger than a predetermined value even when power transmission is performed, power equal to this upper limit value is transmitted to a power receiving apparatus. On the other hand, if the battery remaining capacity is insufficient and an expected value of the battery remaining capacity perhaps become less than the predetermined value when power transmission is performed, power lower than this upper limit value is transmitted to a power receiving apparatus. Note that this transmission power amount is, for example, a value obtained by indicating the ratio to the battery capacity by a percentage. Note that numerical values indicating power to be stored inFIGS. 5A to 5C, 6A to 6C, 7A, and 7B(to be described later) are indicated by percentages based on the capacity of the battery208as shown inFIG. 3.

In this embodiment as described above, when the class identifier is “1” (to be referred to as “Class 1” hereinafter), the user information of the power receiving apparatus is the same as that of the power transmitting apparatus. When the class identifier is “0” (to be referred to as “Class 0” hereinafter), the user information of the power receiving apparatus is different from that of the power transmitting apparatus.FIG. 3shows that the transmission power amount301for a power receiving apparatus of Class 1 is “10%”, so a power amount which is maximally 10% of the battery capacity can be transmitted to this power receiving apparatus. Also, the transmission power amount301for a power receiving apparatus of Class 0 is “5%” inFIG. 3. By thus making the transmission power amount301of Class 1 larger than that of Class 0, a large amount of power can be transmitted to a power receiving apparatus having the same user information as that of the power transmitting apparatus100. A power transmission process corresponding to the apparatus status of each power receiving apparatus can be performed by thus setting a priority level to the transmission power amount by the class300. Note that the identification of a class may be given to indicate the priority level of power transmission to a power receiving apparatus belonging to the class. For example, the priority level may increase as the numerical value of the identifier increases.

(Information to be Stored in Control Storage Unit207)

FIG. 4shows examples of information to be stored in the control stage unit207. A determination flag400is set to “1” when the determination unit202must determine the appropriateness of the transmission power amount. A reduction flag401is set to “1” when the distribution unit204must reduce the transmission power amount for each of one or more power receiving apparatuses.

(Information to be Stored in Power Transmission Management Unit206)

FIGS. 5A to 5Cshow examples of information to be stored in the power transmission management unit206. Apparatus IDs501ato501cstore the identifiers of power receiving apparatuses. Classes502ato502cstore the class identifiers of the apparatus IDs. Transmission power amounts503ato503cstore power amounts scheduled to be transmitted to the power receiving apparatuses specified by the apparatus IDs. Transmitted power amounts504ato504cstore power amounts already transmitted to the power receiving apparatuses specified by the apparatus IDs.

FIG. 5Ashows that when this information is stored, apparatus 2 belongs to Class 1, power equivalent to 10% of the battery capacity is scheduled to be transmitted to apparatus 2, and a power amount already transmitted to apparatus 2 is 0%.FIG. 5Aalso shows that apparatus 3 belongs to Class 0, power equivalent to 5% of the battery capacity is scheduled to be transmitted to apparatus 3, and a power amount already transmitted to apparatus 3 is 0%.

The power transmission management unit206updates the stored information when, for example, the already transmitted power amount changes with the elapse of time, or power transmission is to be performed for a new power receiving apparatus. For example, the power transmission management unit206updates the stored information fromFIG. 5AtoFIG. 5B, orFIG. 5BtoFIG. 5C.

(Information to be Stored in Determination Storage Unit203)

FIGS. 6A to 6Care examples of information to be stored in the determination storage unit203. Classes600ato600care class identifiers. Classified transmission power amounts601ato601ceach indicate the sum total of transmission power amounts stored in the power transmission management unit206for each class. In the case shown inFIG. 5A, for example, only apparatus 2 is a power receiving apparatus of Class 1, and the transmission power amount of apparatus 2 is 10%, so the total value of the transmission power amounts of Class 1 is 10%. Likewise, the total value of the transmission power amounts of Class 0 is 5% (601a). On the other hand, in the case shown inFIG. 5B, apparatuses 2 and 4 are power receiving apparatuses of Class 1, and their transmission power amounts are respectively 7% and 10%, so the total value of the transmission power amounts of Class 1 is 17% (601b).

Total transmission power amounts602ato602care the total values of the classified transmission power amounts601ato601c. Accordingly, the total transmission power amount602ais “15” inFIG. 6A, and the total transmission power amount602bis “19” inFIG. 6B. Battery remaining capacities603ato603ceach indicate the remaining capacity of the battery208. The battery remaining capacities603ato603cgradually reduce when power transmission is performed. Expected remaining capacities604ato604care the expected values of the battery remaining capacities when power indicated by the total transmission power amounts602ato602cis transmitted, and are values obtained by subtracting the total transmission power amounts602ato602cfrom the battery remaining capacities603ato603c.

Thresholds605ato605care the reference values of the battery remaining capacities603ato603cwhen the determination unit202determines the necessity of increase/reduction of the transmission power amount. For example, the user may set the thresholds605ato605cfrom the viewpoint of the user-friendliness of the power transmitting apparatus100as an electronic apparatus. For example, when the power transmitting apparatus100is an electronic apparatus having a high frequency of use, the user can secure a sufficient battery remaining capacity after power transmission by setting the thresholds605ato605cat high values. Note that in this embodiment, the thresholds605ato605care set at a predetermined value of “40”, and are not changed. However, it is also possible to change the thresholds605ato605cduring power transmission or the like by, for example, user's setting.

Necessary reduction amounts606ato606care values obtained by subtracting the expected remaining capacities604ato604cfrom the thresholds605ato605c. When the sign of the necessary reduction amounts606ato606cis 0 or less, the expected remaining capacities604ato604cafter power transmission are equal to or larger than the thresholds605ato605c, so the transmission power amounts need not be reduced. On the other hand, if the values of the necessary reduction amounts606ato606care larger than 0, the expected remaining capacities604ato604cafter power transmission are smaller than the thresholds605ato605c, so the transmission power amounts need to be reduced.

(Information to be Stored in Distribution Storage Unit205)

FIGS. 7A and 7Bshow examples of information to be stored in the distribution storage unit205.FIGS. 7A and 7Bshow examples in which the distribution storage unit205stores only the reduction amounts when the transmission power is reduced. Apparatus IDs700aand700bindicate identifiers for identifying power receiving apparatuses. Classes701aand701bare class identifiers, and store classes corresponding to the power receiving apparatuses. Reduction amounts702aand702brepresent reduction amounts decided by the distribution unit204, and store the reduction amounts of the transmission power corresponding to the power receiving apparatuses.

Classified reduction amounts703aand703beach store the sum total of the reduction amounts of each class. For example, in the case shown inFIG. 7A, the transmission power is reduced for only apparatus 3 of Class 0, and the reduction amount702aof apparatus 3 is 2%, so the classified reduction amount703ais 0% for Class 1 and 2% for Class 0. On the other hand, in the case shown inFIG. 7B, the transmission power is reduced not only for apparatus 3 but also for apparatuses 2 and 4. Consequently, the sum of the reduction amounts702bis (2.5%+2.5%=) 5% for Class 1 and 2% for Class 0, so the classified reduction amount703bis 5% for Class 1 and 2% for Class 0.

Total reduction amounts704aand704bare the sum totals of the classified reduction amounts703aand703b. Differences705aand705bare differences between the necessary reduction amounts606ato606cshown inFIGS. 6A to 6Cand the total reduction amounts704aand704b, and are values obtained by subtracting the total reduction amounts704aand704bfrom the necessary reduction amounts606ato606c. That is, it is necessary to further reduce the transmission power by power amounts indicated by the differences705aand705b.FIG. 7Ashows that the necessary reduction amount606ais larger by 5 than the total reduction amount704a, and it is necessary to further reduce the transmission power amount by 5%.

Next, a process executed in the wireless power transfer system according to this embodiment will be explained.FIG. 8is a sequence chart showing the procedure of a power transmission process of this embodiment.FIG. 9is a flowchart showing a procedure in the classification unit200.FIG. 9shows a process in which the classification unit200classifies a power receiving apparatus based on the apparatus ID of the power receiving apparatus, sets a transmission power amount corresponding to the class, and urges the determination unit to determine the appropriateness of this transmission power amount.FIG. 10is a flowchart showing a procedure in the determination unit202of this embodiment.FIG. 10shows a process in which the determination unit202determines the appropriateness of a transmission power amount decided based on the battery remaining capacity and each class.FIG. 11is a flowchart showing a procedure in the distribution unit204of this embodiment.FIG. 11shows a process in which the distribution unit204reduces a transmission power amount from a class having a low priority level in accordance with a priority level decided for each class.

When the process is started, the power transmitting apparatus100(the classification unit200) receives a notification of apparatus ID “2” from apparatus 2 via a communication unit (not shown) (F800and step S900). Upon receiving the notification of the apparatus ID, the classification unit200determines whether the apparatus ID is registered in the power transmission management unit206(step S901). Assume that at this point of time, the power transmitting apparatus100is not transmitting power to any power receiving apparatus, and the apparatus ID of any power receiving apparatus is not registered. Therefore, since apparatus ID “2” is not registered in the power transmission management unit206(YES in step S901), the classification unit200adds “apparatus 2” to the apparatus ID (501a) and updates the information stored in the power transmission management unit206(step S902).

Subsequently, the classification unit200receives a notification of the user information from apparatus 2 (F801and step S903). Note that the user information may also be notified together with the above-described apparatus ID. In this embodiment, the user information of apparatus 2 is “A”. The classification unit200compares the user information received in F801with the user information of the power transmitting apparatus100(step S904). In this embodiment, the user information of the power transmitting apparatus100is “A”, so the user information of apparatus 2 matches that of the power transmitting apparatus100(YES in step S904). Accordingly, the classification unit200updates the class of apparatus 2 to “1” in the information stored in the power transmission management unit206(step S905).

Note that a power receiving apparatus is classified in accordance with match or mismatch of the user information in this embodiment, but the present invention is not limited to this. For example, the classification may also be performed in accordance with the apparatus type of a power receiving apparatus, such as power required to drive the apparatus or the chargeability of the apparatus. Alternatively, the classification may be performed in accordance with the group information, apparatus types, apparatus manufacturer information, frequencies of use, or battery remaining amounts of a power transmitting apparatus and power receiving apparatuses, or a combination thereof.

After that, the classification unit200refers to the information stored in the transmission power amount storage unit201(step S906), and confirms upper limit value “10” of the transmission power amount corresponding to Class 1. Then, the classification unit200updates the transmission power amount for apparatus 2 to upper limit value “10” in the information stored in the power transmission management unit206(step S908). At this point of time, the update of the power transmission management unit206, which corresponds to apparatus 2, is complete (F802).

Then, the classification unit200determines whether the information stored in the power transmission management unit206is updated for all power receiving apparatuses whose apparatus IDs have been notified (step S909). In this example, a notification of the apparatus ID is received from apparatus 3 in F803, so the update of the information about all power receiving apparatuses is not complete (NO in step S909). Therefore, following the same procedure as described above, the classification unit200acquires the user information of apparatus 3 (F804), and updates the information of apparatus 3 stored in the power transmission management unit206(F805). Note that the user information of apparatus 3 is “B” and does not match the user information of the power transmitting apparatus100(NO in step S904), so “0” is stored as a class in the power transmission management unit206(step S910). Since the class of apparatus 3 is “0”, the transmission power amount for apparatus 3 in the information stored in the power transmission management unit206is updated by “5” as the upper limit value of the transmission power amount corresponding to Class 0 stored in the transmission power amount storage unit201. At this point of time, information stored in the power transmission management unit206is as shown inFIG. 5A.

After that, since the update of the information stored in the power transmission management unit206is complete for all the power receiving apparatuses whose apparatus IDs have been notified at this point of time (YES in step S909), the classification unit200sets the determination flag to “1” (step S911and F806), and terminates the process.

Note that in this embodiment, the classification unit200receives a notification of the apparatus ID from a power receiving apparatus and registers the apparatus ID before transmitting power. However, the present invention is not limited to this. For example, the user of the power transmitting apparatus100may input information for specifying the apparatus ID of a power receiving apparatus via an operation unit (not shown), and the classification unit200may acquire the apparatus ID and register the apparatus information in the power transmission management unit206. Note that continuous apparatus ID acquisition after the registration is performed via communication in this case as well.

After that, if the determination flag changes to “1” (YES in step S1000), the determination unit202starts the process shown inFIG. 10. The determination unit202first acquires the battery remaining capacity from, for example, the battery208(F807), and updates the item of the battery remaining capacity in the information stored in the determination storage unit203(step S1001). For example, when the acquired battery remaining capacity is 58%, the determination unit202sets the battery remaining capacity603aat “58%” as shown inFIG. 6A.

Then, the determination unit202determines whether the battery remaining capacity603ais equal to or larger than the threshold605a(step S1002). This determination is executed because no power transmission can be performed if the battery remaining capacity is not exceeding the threshold. Accordingly, if the battery remaining capacity is less than the threshold (NO in step S1002), the determination unit202determines that no power transmission can be performed (step S1012), and terminates the whole power transmission process executed by the power transmitting apparatus.

In this embodiment, as shown inFIG. 6A, the battery remaining capacity603ais 58% at this point of time, and hence is 40% or more of the threshold605a(YES in step S1002). Note that the power transmitting apparatus has a battery remaining capacity of 58% and has a surplus of 18% compared to 40% of the threshold at this point of time, and hence can transmit 18% of the battery capacity to one or more power receiving apparatuses. Accordingly, the determination unit202determines that power can be transmitted to apparatuses 2 and 3. In this stage, the determination unit202updates the determination flag400of the control storage unit207to 0 (step S1003).

Subsequently, the determination unit202determines the appropriateness of the transmission power amount503ain the information stored in the power transmission management unit206, which is updated by the classification unit200. First, the determination unit202updates information pertaining to the transmission power amount, battery remaining capacity, and necessary reduction amount, of the information stored in the determination storage unit203(steps S1004to S1007). According toFIG. 5A, only apparatus 2 is an apparatus for which the class502ais 1, and the transmission power amount503aof apparatus 2 is 10% of the battery capacity. Therefore, the determination unit202updates the classified transmission power amount601acorresponding to Class 1 to “10” in the information stored in the determination storage unit203(step S1004). Similarly, according toFIG. 5A, only apparatus 3 is an apparatus for which the class502ais 0, and the transmission power amount503aof apparatus 3 is 5% of the battery capacity. Therefore, the determination unit202updates the classified transmission power amount601acorresponding to Class 0 to “5” in the information stored in the determination storage unit203(step S1004). Then, the determination unit202adds “10” and “5” of the classified transmission power amount601a, and updates the total transmission power amount602aas the sum total of the transmission power amounts to be transmitted to the power receiving apparatuses to “15” (step S1005).

Subsequently, based on the battery remaining capacity603aand total transmission power amount602a, the determination unit202calculates the expected remaining capacity604aof the battery after power transmission. More specifically, since the battery remaining capacity603ais 58% and the total transmission power amount602ais 15% at present, the determination unit202subtracts 15 from 58 and updates the expected remaining capacity604aafter power transmission to 43 (step S1006).

Then, the determination unit202calculates the necessary reduction amount606abased on the threshold605aand expected remaining capacity604a. In this state, the threshold605ais 40%, and the expected remaining capacity604ais 43% at this point of time. Accordingly, the battery remaining capacity expected after power transmission has a surplus of 3% with respect to the threshold605a. The determination unit202updates the necessary reduction amount606aby “−3” as a result of subtraction of 43 from 40 (step S1007). These processes update the information stored in the determination storage unit203(F808).

According to the updated information, the necessary reduction amount606ais 0 or less (YES in step S1008). Therefore, the determination unit202determines that the reduction of the transmission power amount is unnecessary, and updates the reduction flag401of the control storage unit207to 0 (step S1009and F809). When the reduction flag401is 0, it is possible to directly transmit the transmission power amount stored in the power transmission management unit206. Based on the transmission power amount503astored in the power transmission management unit206, therefore, the determination unit202starts power transmission to apparatuses 2 and 3 via the power transmitting unit209(F810and F811, and step S1010).

Even after power transmission is started, apparatuses 2 and 3 can notify the power transmitting apparatus100of the apparatus IDs at a predetermined period. Upon receiving the apparatus IDs (step S900), the classification unit200determines whether the apparatus IDs are already registered (step S901). In this case, the apparatus IDs of apparatuses 2 and 3 are already registered, so the classification unit200updates the transmitted power amount504aof each apparatus in the information stored in the power transmission management unit206(step S907). Then, the classification unit200subtracts the transmitted power amount504afrom the transmission power amount decided before the start of power transmission, and updates the information of the transmission power amount503a(step S908).

Assume that apparatus 4 notifies the power transmitting apparatus100of the apparatus ID when power which is 3% of the battery capacity is transmitted to each of apparatuses 2 and 3 (F812and step S900). The classification unit200updates the information stored in the power transmission management unit206by including the information of apparatus 4 based on the flowchart shown inFIG. 9. In the information stored in the power transmission management unit206, the transmitted power amount504bof each of apparatuses 2 and 3 is updated to 3 as indicated by the information about apparatuses 2 and 3 shown inFIG. 5B. In addition, as indicated by the information about apparatuses 2 and 3 shown inFIG. 5B, the transmission power amounts503bare also updated to “7” and “2” obtained by subtracting the respective transmitted power amounts from “10” and “5” as the transmission power amounts decided before the start of power transmission. This demonstrates that power which is 7% of the battery capacity is scheduled to be transmitted to apparatus 2 hereafter, and power which is 2% of the battery capacity is scheduled to be transmitted to apparatus 3 hereafter.

In this state, when the apparatus ID of apparatus 4 is notified, a line indicating that the apparatus ID501bis “apparatus 4” is added to the information stored in the power transmission management unit206(step S902). The classification unit200acquires user information “A” of apparatus 4 (step S903). Since this user information matches that of the power transmitting apparatus100(YES in step S904), the classification unit200updates the class to “1” (step S905). After that, the classification unit200refers to the transmission power amount storage unit201(step S906), and updates the transmission power amount503bin the information stored in the power transmission management unit206by “10” as the upper limit value of the transmission power amount for apparatus 4 (step S908). After thus updating the information stored in the power transmission management unit206(F814), the classification unit200sets the determination flag to “1” (step S911and F815), and terminates the process. When the process is terminated, the information stored in the power transmission management unit206is as shown inFIG. 5B.

Note that the update of the information about apparatuses 2 and 3 stored in the power transmission management unit206may also be executed when the apparatus ID of apparatus 4 is notified. That is, it is unnecessary to periodically update the apparatus IDs of apparatuses 2 and 3. In this case, after the registration of the information about apparatus 4 is complete, the classification unit200may determine whether apparatuses 2 and 3 have been updated (step S909), and update information pertaining to a non-updated apparatus ID (NO in step S909).

Since the determination flag400is updated to 1, the determination unit202starts determining whether power transmission can be performed by the transmission power amount in the information stored in the power transmission management unit206(YES in step S1000). When starting the process, the determination unit202acquires the battery remaining capacity from the battery208(F816), and updates the battery remaining capacity in the information stored in the determination storage unit203(step S1001). At this point of time, the power transmitting apparatus100is transmitting power which is 3% of the battery capacity to each of apparatuses 2 and 3, so the battery remaining capacity has become 52% by reducing by 6% from 58% as the battery remaining capacity603abefore the start of power transmission. Accordingly, the determination unit202updates the battery remaining capacity603bto 52 (step S1001). Note that at this point of time, the battery remaining capacity is larger than the threshold (YES in step S1002), and has a surplus of 12% compared to 40% as the threshold.

Subsequently, the determination unit202refers to the information (FIG. 5B) stored in the power transmission management unit206, and determines whether it is really possible to transmit the transmission power amount503bupdated by the classification unit200. The determination unit202first clears the determination flag (step S1003), and then updates the information stored in the determination storage unit203(steps S1004to S1007).

According toFIG. 5B, power receiving apparatuses belonging to Class 1 are two apparatuses 2 and 4, the transmission power amount503bof apparatus 2 is 7%, and the transmission power amount503bof apparatus 4 is 10%, so the sum total is 17%. Accordingly, the determination unit202updates the classified transmission power amount601bcorresponding to Class 1 to “17” in the information stored in the determination storage unit203(step S1004). Also, according toFIG. 5B, only apparatus 3 is an apparatus belonging to Class 0, and the transmission power amount503bof apparatus 3 is 2%. Therefore, the determination unit202updates the classified transmission power amount601bcorresponding to Class 0 to “2” in the information stored in the determination storage unit203(step S1004). The determination unit202adds “17” and “2” of the classified transmission power amount601b, and updates the total transmission power amount602bto “19” (step S1005).

Then, the determination unit202calculates the expected remaining capacity604bafter power transmission based on the battery remaining capacity603band total transmission power amount602b. Since the battery remaining capacity603bis 52% and the total transmission power amount602bis 19% at present, the determination unit202updates the expected remaining capacity604bafter power transmission to “33” as a value obtained by subtracting 19 from 52 (step S1006). After that, the determination unit202calculates the necessary reduction amount606bbased on the threshold605band expected remaining capacity604b. Since the threshold605bis 40% and the expected remaining capacity604bis 33%, the determination unit202subtracts 33 from 40 and updates the necessary reduction amount606bto 7 (step S1007). This reveals that the expected battery remaining capacity after power transmission is less than the threshold605aby 7%. At this point of time, the determination unit202terminates the update of the determination storage unit (F817).

In this state, the necessary reduction amount606bis “7”, that is, larger than 0 (NO in step S1008), so the determination unit202determines that the reduction of the transmission power amount is necessary, and updates the reduction flag401to “1” in the information stored in the control storage unit207(step S1011and F818). After that, the determination unit202terminates the determination process.

Since the reduction flag401is set to “1”, the distribution unit204starts the process shown inFIG. 11(YES in step S1100). The distribution unit204performs a process of reducing the transmission power amount503b, in order to reduce the power amount stored in the necessary reduction amount606bof the determination storage unit203.

First, the distribution unit204selects a class as a target of power reduction. For example, the distribution unit204selects a class having the lowest priority level from the viewpoint of power distribution during power transmission. This priority level is a value which is low when the transmission power amount can be small, and is high when a large transmission power amount must be secured. For example, when the priority level increases as the value of the class identifier increases, the distribution unit204refers to the information (FIG. 3) stored in the transmission power amount storage unit201, and selects Class 0 as a minimum value of the class identifier (step S1101). Subsequently, the distribution unit204determines whether the necessary reduction amount606bcan be reduced if all transmission power amounts to apparatuses belonging to the selected class are reduced. For this determination, the distribution unit204first acquires the value “7” of the necessary reduction amount606bin the information stored in the determination storage unit203, and updates the difference to “7” in the information stored in the distribution storage unit205(step S1102).

Then, the distribution unit204acquires the value “2” of the classified transmission power amount601bof Class 0 in the information stored in the determination storage unit203(step S1103), and compares this value with the value “7” as the difference stored in the distribution storage unit205(step S1104). In this case, the difference “7” is larger than the value “2” of the classified transmission power amount601b(NO in step S1104). This shows that even when the transmission power amount is reduced to 0 for all apparatuses of Class 0, it is necessary to reduce the transmission power amount for another class (in this case, Class 1). In this case, the distribution unit204first updates the information of the transmission power amount for Class 0.

As shown inFIG. 5C, the distribution unit204updates the transmission power amount503ccorresponding to apparatus 3 in the information stored in the power transmission management unit206from “2” of the transmission power amount503bshown inFIG. 5Bto “0” as shown inFIG. 5C(step S1105). Then, as shown inFIG. 6C, the distribution unit204updates the classified transmission power amount601ccorresponding to Class 0 in the information stored in the determination storage unit203to “0” (step S1106).

In this case, the transmission power amount to apparatus 3 is reduced by 2 from “2” to “0”. As shown inFIG. 7A, therefore, the distribution unit204updates the reduction amount702acorresponding to apparatus 3 to “2” in the information stored in the distribution storage unit205(step S1107). Also, in accordance with this update of the reduction amount702a, the distribution unit204updates the classified reduction amount703aof Class 0 to “2” in the information stored in the distribution storage unit205(step S1108), and updates the total reduction amount704ato “2” as the sum total of the classified reduction amounts703a(step S1109). After that, the distribution unit204updates the difference705ato “5” as a result of the subtraction of “2” of the total reduction amount704afrom “7” stored in step S1102(step S1110).

At this point of time, the information stored in the distribution storage unit205is as shown inFIG. 7A. According toFIG. 7A, the transmission power amount of apparatus 3 belonging to Class 0 is reduced by 2%, and the difference705ais 5. Accordingly, transmission power equivalent to 5% of the battery capacity, which is indicated by the difference705a, must be reduced from the transmission power for Class 1. Therefore, the distribution unit204increments the class identifier from 0 to 1 (step S1111), and subsequently acquires the value “17” of the classified transmission power amount601bof Class 1 in the information stored in the determination storage unit203(step S1103). Since “17” as the classified transmission power amount601bof Class 1 is larger than “5” as the difference705a(YES in step S1104), the process advances to step S1112.

The distribution unit204divides the difference705aby the number of apparatuses belonging to Class 1 (step S1112). According toFIG. 7A, apparatuses belonging to Class 1 are two apparatuses 2 and 4. Therefore, the distribution unit204divides “5” as the difference705aby “2”, thereby obtaining “2.5”. In accordance with this result, the distribution unit204updates the reduction amounts702bof apparatuses 2 and 4 to “2.5” as shown inFIG. 7B(step S1113). In accordance with this update of the reduction amounts702b, the distribution unit204updates the classified reduction amount703bof Class 1 to “5” as the sum total of the reduction amounts702bof the apparatuses of Class 1 as shown inFIG. 7B(step S1114). Also, the distribution unit204updates the total reduction amount704bto “7” as the sum total of the classified reduction amounts703b(step S1115). Then, the distribution unit204updates the difference705bto “0” as a result of the subtraction of “7” of the total reduction amount704bfrom “7” stored in step S1102(step S1116).

Subsequently, as shown inFIG. 5C, the distribution unit204updates the transmission power amounts for apparatuses 2 and 4 to values obtained by subtracting the reduction amounts702bshown inFIG. 7B, in the information stored in the power transmission management unit206from the transmission power amount before reduction (the transmission power amount503bshown inFIG. 5B) (step S1117). At this point of time, the information stored in the power transmission management unit206is as shown inFIG. 5C.FIG. 5Cshows that the transmission power amount503cfor apparatus 2 is 4.5%, and the transmission power amount503cfor apparatus 4 is 7.5%. After updating the transmission power amounts, the distribution unit204updates the reduction flag401to “0” (step S1118), and the determination flag400to “1” (step S1119), and terminates the process.

Note that the transmission power amount for a class having a low priority level is reduced to 0 in this embodiment, but this transmission power amount may also be reduced to a predetermined amount. That is, it is also possible to set the lowest power amount of power transmission as a predetermined amount, and, if the reduction amount is insufficient even when the transmission power is reduced to this predetermined amount for a class having a low priority level, reduce the transmission power amount for another class. For example, when the predetermined amount is 0.5%, the transmission power amount of Class 0 may be reduced by 1.5% as a value obtained by subtracting this predetermined amount from the value “2” of the classified transmission power amount of Class 0. For 5.5% as the remainder, the transmission power for Class 1 may be reduced within the range in which the transmission power is 0.5% or more.

In response to the update of the determination flag400to “1” (YES in step S1000), the determination unit202executes the process shown inFIG. 10again. First, the determination unit202acquires the battery remaining capacity (F820), and updates the value of the battery remaining capacity603cin the information stored in the determination storage unit203(step S1001). Note that if it is detected that the reduction flag401is set to “1” and subsequently the determination flag400is set to “1”, the determination unit202need not acquire nor update the battery remaining capacity. This is so because after setting the reduction flag401to “1”, the distribution unit204always sets the determination flag400to “1” before actual power transmission, and no large fluctuation probably occurs in the battery remaining capacity during the processing of the distribution unit204.

Subsequently, the determination unit202determines whether power transmission can be performed by the transmission power amount503cin the information stored in the power transmission management unit206, which is updated by the classification unit200. In this case, apparatuses of Class 1 are apparatuses 2 and 4, and, as shown inFIG. 5C, the transmission power amount503cfor apparatus 2 is 4.5%, and the transmission power amount503cfor apparatus 4 is 7.5%, in the information stored in the power transmission management unit206. As shown inFIG. 6C, therefore, the determination unit202updates the classified transmission power amount601ccorresponding to Class 1 to “12” as the sum total of the transmission power amounts503cof apparatuses 2 and 4, in the information stored in the determination storage unit203(step S1004). Also, only apparatus 3 is an apparatus of Class 0, and, as shown inFIG. 5C, the transmission power amount503cfor apparatus 3 is 0% in the information stored in the power transmission management unit206. As shown inFIG. 6C, therefore, the determination unit202updates the classified transmission power amount601ccorresponding to Class 0 to “0” in the information stored in the determination storage unit203(step S1004). Then, as shown in FIG.6C, the determination unit202adds “12” and “0” of the classified transmission power amount601c, and updates the total transmission power amount602cto “12”, in the information stored in the determination storage unit203(step S1005).

In addition, the determination unit202calculates the expected remaining capacity604cof the battery after power transmission based on the battery remaining capacity603cand total transmission power amount602c. In this case, the battery remaining capacity603cis 52% and the total transmission power amount602cis 12% at present, so the determination unit202updates the expected remaining capacity604cafter power transmission to “40” (step S1006). Then, the determination unit202calculates the necessary reduction amount606cbased on the threshold605cand expected remaining capacity604c. Since the threshold605cis 40% and the expected remaining capacity604cis 40%, the determination unit202updates the necessary reduction amount606cto “0” (step S1007), and terminates the update of the information stored in the determination storage unit203(F821).

Since the necessary reduction amount606cis 0 or less (YES in step S1008), the determination unit202determines that the reduction of the transmission power amount is unnecessary, and sets the reduction flag to “0” (step S1009and F822). Then, based on the transmission power amount503cof the power transmission management unit206, the determination unit202starts power transmission to apparatuses 2 and 4 via the power transmitting unit209(F823and F824).

As described above, the power transmitting apparatus100according to this embodiment classifies one or more power receiving apparatuses based on the user information of the power receiving apparatuses. Then, based on the upper limit value of the transmission power amount determined based on this class and the battery remaining capacity which changes due to power transmission, the power transmitting apparatus100decides power amounts to be transmitted to one or more power receiving apparatuses, and distributes the transmission power. In a wireless power transfer system for transmitting power to one or more power receiving apparatuses, therefore, it is possible to control the transmission power amount for each power receiving apparatus while preventing out-of-battery of the power transmitting apparatus.

Note that the case in which a plurality of power receiving apparatuses exist have been explained above. Even when there is only one power receiving apparatus, however, it is also possible to decide the transmission power amount in accordance with the upper limit value of the transmission power amount to be transmitted to the power receiving apparatus, and the battery remaining capacity. Assume that the class of one power receiving apparatus is 1, the upper limit value of the transmission power amount is 10, the battery remaining capacity of the power transmitting apparatus is 48, and the threshold is 40. In this case, if the power transmitting apparatus transmits a power amount equal to the upper limit value to the power receiving apparatus, the expected value of the battery remaining capacity becomes 38, that is, smaller than the threshold. In this case, therefore, it is possible to decide a transmission power amount so as to transmit a power amount of 8 to the power receiving apparatus.

Second Embodiment

In this embodiment, a case in which apparatus 2 has left the wireless power transfer system shown inFIG. 1because, for example, apparatus 2 is removed by the user will be explained.

FIG. 12is a view showing examples of information to be stored in a control storage unit207. In this embodiment, the controls storage unit207stores an increase flag1200for increasing a reduced transmission power in accordance with the leaving of a power receiving apparatus from the system, in addition to a determination flag400and reduction flag401. When a power receiving apparatus currently receiving power has left the system, a determination unit202writes “1” in the increase flag1200in a case in which power scheduled to be transmitted to the power receiving apparatus having left the system is distributed to another power receiving apparatus, and writes “0” in the increase flag1200in other cases.

FIGS. 13A to 13Care views showing examples of information to be stored in a power transmission management unit206in this embodiment.FIGS. 14A and 14Bare views showing examples of information to be stored in a determination storage unit203in this embodiment.FIGS. 15A to 15Care views showing examples of information to be stored in a distribution storage unit205in this embodiment. The distribution storage unit205stores total increase amounts1503aand1503bin addition to each information stored in the first embodiment. When a distribution unit204has reduced a total reduction amount1502a, the same value as the reduction of the total reduction amount1502ais added to the total increase amount1503a. A difference1504ais a value obtained by adding the total increase amount1503ato necessary reduction amounts (1406aand1406bshown inFIGS. 14A and 14B) of transmission power. The pieces of information shown inFIGS. 13A to 13C, 14A and 14B, and 15A to 15Care updated with the elapse of time, or in accordance with a change in state of the system, as in the first embodiment.

In this embodiment, it is assumed that the system is set in a state after the processes in the first embodiment are performed, and a power transmitting apparatus100is transmitting power to apparatuses 2 and 4 based onFIG. 13A.FIG. 13Ashows that a transmission power amount1303afor apparatus 2 is 3.5%, and apparatus 2 is scheduled to receive power transmission which is 3.5% of the battery capacity hereafter.FIG. 13Aalso shows that the transmission power amount1303afor apparatus 4 is 7.5%, and apparatus 4 is scheduled to receive power transmission which is 7.5% of the battery capacity hereafter.

Next, each process to be executed in this embodiment will be explained.FIG. 16is a flowchart showing a procedure in a classification unit200of this embodiment.FIG. 17is a flowchart showing a procedure in the determination unit202of this embodiment.FIG. 18is a flowchart showing a procedure in the distribution storage unit205of this embodiment. Note that the same reference numerals as in the first embodiment denote the same portions explained in the first embodiment, and an explanation thereof will be omitted.

First, the processing of the classification unit200will be explained. When detecting the leaving of a power receiving apparatus, the classification unit200of this embodiment updates the information about the power receiving apparatus stored in the power transmission management unit206and distribution storage unit205. Assume, as described above, that apparatus 2 is removed by the user and hence does not receive power transmitted by the power transmitting apparatus100any longer.

The classification unit200detects that the apparatus ID of apparatus 2 is no longer received (NO in step S1600), and determines that apparatus 2 has left the system (step S1601). Accordingly, as shown inFIG. 13B, the classification unit200updates the transmitted power amount for apparatus 2 in the information stored in the power transmission management unit206(step S1602). In this case, a transmitted amount1304bfor apparatus 2 is 4%. The classification unit200updates a transmission power amount1303bfor apparatus 2 from “3.5” (1303a) as the transmission power amount before the leaving to “0”, in the information stored in the power transmission management unit206(step S1603). Then, the classification unit200updates the transmitted amounts1304bof other power receiving apparatuses in the information stored in the power transmission management unit206(step S1004).FIG. 13Bshows the information stored in the power transmission management unit206at this point of time. As shown inFIG. 13B, at this point of time, the power transmitting apparatus100is scheduled to transmit power which is 6.5% of the battery capacity to only apparatus 4. Thus, the classification unit200completes the update of the information stored in the power transmission management unit206.

Then, the classification unit200updates the information stored in the distribution storage unit205. Since the information obtained when the processes in the first embodiment are completed is stored in the distribution storage unit205at this point of time, this information is as shown inFIG. 7B. The classification unit200updates this information in accordance with the leaving of apparatus 2.

The classification unit200updates a reduction amount1500aof apparatus 2 to 0 (step S1605), and updates a classified reduction amount1501acorresponding to Class 1 to 2.5 as the sum total of the reduction amounts1500aof apparatuses 2 and 4 (step S1606). Subsequently, the classification unit200updates a total reduction amount1502ato 4.5 as the sum total of the classified reduction amounts1501a(step S1607). After that, the classification unit200updates a determination flag400of the control storage unit207to “1” (step S911), and terminates the process.

Since the determination flag is updated to “1” (YES in step S1000), the determination unit202starts the process shown inFIG. 17. First, the determination unit202acquires the battery remaining capacity from a battery208, and updates the information (FIG. 14A) stored in the determination storage unit203(step S1001). Note that the battery remaining capacity is 50% of the battery capacity as indicated by a battery remaining capacity1403ashown inFIG. 14A. Subsequently, the determination unit202acquires a Class1302band the transmission power amount1303bfrom the information (FIG. 13B) stored in the power transmission management unit206, and updates the information stored in the determination storage unit203.

According toFIG. 13B, the transmission power amount1303bfor apparatus 4 belonging to Class 1 is 6.5, and the transmission power amount1303bfor apparatus 3 belonging to Class 0 is 0. As shown inFIG. 14A, therefore, the determination unit202updates a classified transmission power amount1401aof Class 1 to “6.5”, and the classified transmission power amount1401aof Class 0 to “0” (step S1004). Then, the determination unit202updates a total transmission power amount1402ato “6.5” as the sum total of the classified transmission power amounts1401a(step S1005). After that, the determination unit202subtracts the total transmission power amount1402afrom the battery remaining capacity1403a, and updates an expected remaining capacity1404ato “43.5” as the subtraction result (step S1006). The determination unit202subtracts 43.5 of the expected remaining capacity1404afrom 40 as a threshold1405a, and updates the necessary reduction amount1406ato “−3.5” (step S1007).FIG. 14Ashows the information stored in the determination storage unit203at this point of time. The necessary reduction amount1406ashown inFIG. 14Ademonstrates that it is expected that there is a surplus of 3.5% with respect to the threshold when power transmission is complete.

Then, the determination unit202determines, by a subsequent flow, whether this power of 3.5% needs to be distributed to another apparatus. First, the determination unit202determines whether there is leaving of a power receiving apparatus from the system (step S1700). Since apparatus 2 has left the system (YES in step S1700), the determination unit202determines whether the total reduction amount1502ais larger than 0 (step S1701). That is, the determination unit202determines whether there is an apparatus for which the transmission power amount is reduced at this point of time. If the total reduction amount is larger than 0, the above-described surplus power can be distributed to an apparatus for which the transmission power amount is reduced.

If the total reduction amount is larger than 0 (YES in step S1701), the determination unit202determines whether the necessary reduction amount is 0 (step S1702). If the necessary reduction amount is 0 (YES in step S1702), there is no surplus power described above, so the determination unit202starts power transmission without performing any power redistribution (step S1010). On the other hand, if the necessary reduction amount is not 0 (NO in step S1702), there is a surplus power, so the determination unit202sets the increase flag1200to “1” (step S1703), and terminates the process.

In this example, the total reduction amount1502ais 4.5 (YES in step S1701), and the necessary reduction amount1406ais “−3.5” (NO in step S1702). Accordingly, the determination unit202sets the increase flag1200to 1 (step S1703), and terminates the process.

If the reduction flag401is 0 (NO in step S1800) and the increase flag1200is 1 (YES in step S1801), the distribution unit204starts the process shown inFIG. 18. The distribution unit204of this embodiment preferentially distributes surplus power to an apparatus belonging to a high-priority-level class, that is, Class 1 as a class having a large class ID.

First, the distribution unit204selects apparatus 4 of Class 1 having a maximum value indicating class701afrom the information (FIG. 15A) stored in the distribution storage unit205(step S1802).

Also, in the information stored in the distribution storage unit205, the distribution unit204updates the difference1504ato “−3.5” of the necessary reduction amount1406ain the information stored in the determination storage unit203(step S1803). At this point of time, the information stored in the distribution storage unit205is as shown inFIG. 15A.

The distribution unit204acquires 2.5 as the classified reduction amount1501aof Class 1 (step S1804), and compares this value with 3.5 as the absolute value of the difference1504a(step S1805). The absolute value of the difference1504arepresents a surplus of the power. The classified reduction amount1501aof Class 1 is 2.5, that is, smaller than 3.5 as the absolute value of the difference1504a(NO in step S1805). Therefore, the distribution204updates the reduction amount of apparatus 4 corresponding to Class 1 from “2.5” to “0” (step S1806), and updates the classified reduction amount corresponding to Class 1 to 0 by reducing the value by 2.5 (step S1807).

When the reduction amount of apparatus 4 is reduced by 2.5 by the processing in step S1806, this means that the transmission power amount of apparatus 4 is increased by 2.5. Accordingly, the distribution unit204updates the total increase amount by increasing it from 0 by 2.5 as the reduction amount reduced by the processing in step S1806, and updates the total reduction amount by reducing it from 4.5 to 2 as the sum total of the classified reduction amounts (step S1808). At this point of time, the information stored in the distribution storage unit205is as shown inFIG. 15B.

Subsequently, in the information stored in the power transmission management unit206, the distribution unit204updates the transmission power amount of apparatus 4 to “9” as a result of the addition of 6.5 as a preceding value and 2.5 as the reduction amount reduced in step S1806(step S1809). Then, in the information stored in the determination storage unit203, the distribution unit204updates the classified transmission power amount to “9” as a result of the addition of 6.5 as a preceding value and 2.5 as the reduction amount reduced in step S1806(step S1809). After that, the distribution unit204updates the total transmission power amount to “9” as the sum total of the classified transmission power amounts. Note that the transmission power amount for Class 0 is 0 at this point of time, so “9” as a result of the addition of 0 and 9 is stored as the total transmission power amount.

Then, in the information stored in the determination storage unit203, the distribution unit204updates the value of the difference to “−1” as a result of the addition of “2.5” as the total increase amount1503bto “−3.5” as a preceding value of the necessary reduction amount1406a(step S1810). After that, the distribution unit204decrements the class from Class 1 to Class 0 (step S1811).

Subsequently, the distribution unit204acquires “2” as the classified reduction amount1501bof Class 0 (step S1804), and compares this value with “1” as the absolute value of the difference1504b(step S1805). Since the absolute value of the difference1504bis smaller than the classified reduction amount1501bof Class 0 (NO in step S1805), the distribution unit204divides “1” as the absolute value of the difference1504bby the number of apparatuses belonging to Class 0 (in this case, the number is “1” because there is only one apparatus 3) (step S1812). This division result in step S1812corresponds to the power amount to be added to the transmission power amount of an apparatus belonging to Class 0.

Subsequently, the distribution unit204subtracts “1” as the division result in step S1812from “2” as the reduction amount1500bof apparatus 3 corresponding to Class 0, and updates the reduction amount by “1” as a result of the subtraction in the information stored in the distribution storage unit205(step S1813). After that, the distribution unit204updates the classified reduction amount corresponding to Class 0 (step S1814) in accordance with the update of the reduction amount. Then, the distribution unit204updates the total reduction amount to “1” as the sum total of the classified reduction amounts, and updates the total increase amount to “3.5” as a result of the addition of “1” obtained by the subtraction in step S1813and “2.5” as a preceding value of the total increase amount1503b(step S1815). Also, the distribution unit204updates the difference to “0” obtained by adding “3.5” as the total increase amount updated in step S1815to “−3.5” as the necessary reduction amount1406ain the information stored in the determination storage unit203(step S1816). At this point of time, the information stored in the distribution storage unit205is as shown inFIG. 15C.

Then, in the information stored in the power transmission management unit206, the distribution unit204updates the transmission power amount of apparatus 3 to “1” obtained by adding “1” as a result in step S1812to “0” as a preceding value of the transmission power amount1303b(step S1817). At this point of time, the information stored in the power transmission management unit206is as shown inFIG. 13C.

After that, the distribution unit204clears the increase flag to 0 (step S1818), and updates the determination flag to 1 (step S1819).

In response to the update of the determination flag400to 1, the determination unit202executes the process shown inFIG. 17again, and updates the information stored in the determination storage unit203(steps S1003to S1007). First, the determination unit202refers to the information stored in the power transmission management unit206shown inFIG. 13C, and updates the classified transmission power amount to “9” for Class 1, and “1” for Class 0 (step S1004). Then, the determination unit202updates the total transmission power amount by “10” as the total sum of these classified transmission power amounts (step S1005). The determination unit202subtracts “10” as the updated total transmission power amount from “50” as the battery remaining capacity1403bwhich is confirmed beforehand, and updates the expected remaining capacity after the completion of power transmission to “40” as a result of the subtraction (step S1006). Furthermore, the determination unit202subtracts “40” as the updated expected remaining capacity from “40” as a predetermined threshold, and updates the necessary reduction amount to “0” (step S1007). At this point of time, the information stored in the determination storage unit203is as shown inFIG. 14B.

In this state, the necessary reduction amount1406bis “0” in the information shown inFIG. 14B(YES in step S1008and YES in step S1702), apparatus 2 has left the system (YES in step S1700), and the total reduction amount1502cis “1” in the information shown inFIG. 15C(YES in step S1701). Therefore, the determination unit202starts power transmission based on the transmission power amount for each apparatus stored in the power transmission management unit206.

In this embodiment as described above, a surplus power produced when the number of power receiving apparatuses decreases is distributed to another power receiving apparatus for which the transmission power amount is reduced. This makes it possible to transmit power as much as possible within the range not exceeding the upper limit value for each terminal. Also, when the transmission power is increased in order from a power receiving apparatus having a high priority level, it is possible to preferentially transmit sufficient power to a power receiving apparatus to which more power is to be transmitted.

Third Embodiment

In this embodiment, a case in which a power transmitting apparatus includes a power receiving unit (not shown) in addition to the configuration of the first or second embodiment will be explained. This power receiving unit receives, from a power supply source (not shown), the supply of power for the power transmitting apparatus to operate and power to be transmitted to power receiving apparatuses. In this embodiment, a case in which the power supply source is an adapter (external power supply) which converts the commercial AC voltage into a DC voltage will be explained. However, another power transmitting apparatus of a wireless power transfer system may also be a power source.

A procedure in the power transmitting apparatus according to this embodiment will be explained.FIG. 19shows a procedure in the power receiving unit, andFIG. 20shows a procedure in a determination unit. Note that in the following explanation, the procedures are performed by adding them to the arrangement of the second embodiment. However, the processes may also be performed by adding them to the arrangement of the first embodiment.

The power receiving unit monitors whether the power receiving unit is receiving power (step S1900). If the power receiving unit is receiving power (YES in step S1900), the power receiving unit sets a power reception flag to 1 (step S1901). On the other hand, if the power receiving unit is not receiving power (NO in step S1900), the power receiving unit sets the power reception flag to 0 (step S1902). For example, when power transmission is performed by using the power of a battery (step S1010inFIG. 17), the power receiving unit determines NO in step S1900. When the adapter is connected and the power receiving unit starts receiving power supply, the power receiving unit determines YES in step S1900. After that, the power transmitting apparatus advances to the processing in step S1601again, and a classification unit updates the transmission power amounts for all power receiving apparatuses.

When the processing of the classification unit is complete, the determination unit determines whether the power reception flag is 1 (step S2000). If the power reception flag is 1 (YES in step S2000), that is, if the power receiving unit is receiving power, the determination unit executes steps S1004and S1005described previously, and compares the total transmission power amount with the power transmittability of a power transmitting unit (step S2002). If the power transmittability is equal to or larger than the total transmission power amount (YES in step S2002), the determination unit switches the supply sources of power to be supplied to the power transmitting unit from the battery to the power receiving unit by operating a switch (not shown), and performs power transmission.

On the other hand, if the power transmittability is smaller than the total transmission power amount (NO in step S2002), the determination unit updates the necessary reduction amount (step S2003). This necessary reduction amount has a value obtained by subtracting the power transmittability from the total transmission power amount. Subsequently, the determination unit updates the reduction flag to 1 and terminates the process, and the process of a distribution unit shown inFIG. 11is executed after that. When the process of the distribution unit shown inFIG. 11is complete, the procedure advances to the process shown inFIG. 20again, and the determination unit performs the operation. Note that the process shown inFIG. 19performed by the power receiving unit may be executed periodically or continuously, and may also be executed before the operation of the determination unit.

In this embodiment as described above, when the power transmitting apparatus is receiving the supply of power, the supply sources of power to be supplied to the power transmitting unit are switched from the battery to the power receiving unit. In this case, the necessary reduction amount is calculated not from the battery remaining capacity and total transmission power amount but from the power transmittability and total transmission power amount. By thus receiving the supply of power, the power transmitting apparatus can transmit power to power receiving apparatuses without reducing the battery remaining capacity. In addition, the power transmitting apparatus can perform power transmission by using the power transmittability as the upper limit, without taking account of the battery remaining capacity.

Next, a case in which the power receiving unit changes from a power-receiving state to a non-power-receiving state will be explained. Due to this change, the power receiving unit determines NO in step S1900, and sets the power reception flag to 0 (step S1902). Since the power reception flag is not 1, the determination unit determines NO in step S2000, and performs power transmission by switching the supply sources of power to the power transmitting unit from the power receiving unit to the battery by using the switch (not shown). Then, the procedure advances to the process shown inFIG. 17(step S2001). In the arrangement of this embodiment as described above, the supply sources of power to the power transmitting unit are switched between the battery and power receiving unit in accordance with whether the power receiving unit is receiving power. This makes it possible to appropriately transmit power to power receiving apparatuses.

The present invention can control the amount of transmission power for each power receiving apparatus in accordance with the battery remaining capacity in wireless power transfer.

Other Embodiments

This application claims the benefit of Japanese Patent Application Nos. 2013-212353, filed Oct. 9, 2013 and 2014-163941, filed Aug. 11, 2014, which are hereby incorporated by reference herein in their entirety.