PATENT ABSTRACT
A power sever, client and method cooperate to selectably supply power from a power server to a client in a format that is acceptable to the client. The client device is able to distinguish the power server from other power servers based on an identification of the power server transmitted to the client device. The client device is then able to specify, or select, from the specific power server the format of the energy to be conveyed to the client device for ultimate consumption by the client device. The conveyance of energy is provided over conductors or wirelessly.

PATENT DESCRIPTION
TECHNICAL FIELD 
       [0001]    The present invention relates to a power supply device, a power receiving device, and a power supply method. 
       BACKGROUND ART 
       [0002]    Many electronic devices such as personal computers and game machines use an AC adaptor, which inputs an alternating-current (AC) power from a commercial power supply and outputs electric power in a format compatible with the device, for the purpose of operating the device and charging the battery. Although the electronic device is usually operated by a direct current (DC), the voltage and current are different in each device. Thus, the AC adaptor outputting electric power matching each device is also different for each device. Thus, even if AC adaptors have similar shapes, they can be incompatible with each other, and there is an issue that the number of AC adaptors increases with increasing numbers of devices. 
         [0003]    In order to solve the above issue, there has been proposed a power bus system in which a power supply block supplying electric power to devices such as a battery and an AC adaptor and a power consumption block receiving electric power from the power supply block are connected to a common DC bus line (for example, Patent Literatures 1 and 2, listed below). In this power bus system, a DC current flows through a bus line. Further, in the power bus system, each block itself is described as an object, and the objects of the respective blocks mutually transmit and receive information (state data) through a bus line. The object of each block generates the information (state data) based on a request from the object of another block and transmits the information as reply data. The object of the block having received the reply data can control electric power supply and consumption based on the contents of the received reply data. 
       CITATION LIST 
     Patent Literature 
       [0004]    PTL 1: Japanese Patent Application Laid-Open No. 2001-306191 
         [0005]    PTL 2: Japanese Patent Application Laid-Open No. 2008-123051 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0006]    In the power bus systems disclosed in the Patent Literature references 1 and 2, for example, all communications between a server and a client are performed through a bus line. Meanwhile, as a mechanism for feeding electric power, there is wireless power transfer using a magnetic line and the like, and when the power feeding mechanism such as wireless power transfer is incorporated in the power bus system, it is inappropriate to support wire-based communication. The present inventors recognized that this conventional approach does not allow for client devices to distinguish between different power servers that may be able to provide different power formats for conveying power to the client devices wirelessly or directly. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0007]      FIG. 1  is an explanatory view showing a constitution of a power supply system according to a first embodiment. 
           [0008]      FIG. 2  is an explanatory view for explaining a power supply processing by a power supply system  1  according to the first embodiment. 
           [0009]      FIG. 3  is an explanatory view showing a constitution of a power supply server  100  according to the first embodiment. 
           [0010]      FIG. 4A  is an explanatory view showing a change of a voltage observed on a bus line  10 . 
           [0011]      FIG. 4B  is an explanatory view showing a change of a voltage observed on a bus line  10 . 
           [0012]      FIG. 5  is a flow chart showing a voltage detection processing in a server and a client, having received a synchronous packet, in the power supply system  1  according to the first embodiment. 
           [0013]      FIG. 6  is an explanatory view showing a power supply system  2  according to a second embodiment. 
           [0014]      FIG. 7  is a flow chart of a method for communicating between a power server and client, prior to the power server conveying power to the client for use in powering the client. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0015]    Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the appended drawings. Note that, in this specification and the appended drawings, structural elements that have substantially the same function and structure are denoted with the same reference numerals, and repeated explanation of these structural elements is omitted. 
         [0016]    Descriptions will be made in the following order: 
         [0017]    &lt;1. First embodiment&gt; 
         [0018]    (1-1. Constitution of power supply system) 
         [0019]    (1-2. Power supply processing by power supply system) 
         [0020]    (1-3. Constitution example of power supply server) 
         [0021]    (1-4. Operation example of power supply server) 
         [0022]    &lt;2. Second embodiment&gt; 
         [0023]    (2-1. Constitution of power supply system) 
         [0024]    (2-2. Operation of power supply system) 
         [0025]    &lt;3. Conclusion&gt; 
       1. First Embodiment 
     1-1. Constitution of Power Supply System 
       [0026]    First, a constitution of a power supply system according to a first embodiment of the present invention will be described.  FIG. 1  is an explanatory view showing the constitution of the power supply system according to the first embodiment. Hereinafter, the constitution of the power supply system according to the first embodiment will be described using  FIG. 1 . 
         [0027]    As shown in  FIG. 1 , a power supply system  1  is configured to include a power supply server  100  and a client  200 . The power supply server  100  and the client  200  are connected to each other through a bus line  10 , which, as shown, may include separate conductors. 
         [0028]    The power supply server  100  supplies DC power to the client  200 . The power supply server  100  further transmits and receives an information signal to and from the client  200 . In the present embodiment, the DC power supply and the transmission and reception of the information signal between the power supply server  100  and the client  200  are shared on the bus line  10 . 
         [0029]    The power supply server  100  is configured to include a communication modem for use in transmitting and receiving the information signal and a microprocessor for use in controlling an electric power supply, and a switch controlling a DC power output. However, the processor may also be a logic-based device such as an application specific integrated circuit (ASIC) or a programmable logic array (PLA). 
         [0030]    The client  200  receives the DC power supply from the power supply server  100 . The client  200  further transmits and receives the information signal to and from the power supply server  100 . In  FIG. 1 , the two clients  200  are illustrated. In the following description, for convenience&#39;s sake of explanation, the two clients  200  are distinguished respectively as CL 1  or CL 2 . 
         [0031]    The client  200  is configured to include a communication modem for use in transmitting and receiving the information signal and a microprocessor for use in controlling the electric power supply, and a switch controlling the DC power output. 
         [0032]    In the power supply system  1  shown in  FIG. 1 , the single power supply server  100  and the two clients  200  are illustrated. However, in the present invention, the number of the power supply servers and the number of the clients are not limited to the specific numbers shown in the example. 
         [0033]    Since a method of supplying electric power in the power supply systems  1  and  2  shown in  FIG. 1  is described in Japanese Patent Application Laid-Open No. 2008-123051, the entire contents each of Japanese Patent Application Laid-Open No. 2008-123051 is incorporated herein by reference. However, hereinafter, processing performed by the power supply system  1  according to the present embodiment will be briefly described. 
       1-2. Power Supply Processing By Power Supply System 
       [0034]      FIG. 2  is an explanatory view for explaining the power supply processing by the power supply system  1  according to the present embodiment. Hereinafter, the power supply processing by the power supply system  1  according to each of the above embodiments of the present invention will be described using  FIG. 2 . 
         [0035]    As shown in  FIG. 2 , the power supply server  100  periodically outputs synchronous packets A 1 , A 2 , A 3 , and . . . to the bus line  10 . The power supply server  100  further outputs information packets B 1 , B 2 , B 3 , and . . . and power packets C 1 , C 2 , C 3 , and . . . so as to supply electric power to the client  200 . The information packets B 1 , B 2 , B 3 , and . . . are the information signals transmitted and received to and from the client  200 , and the power packets C 1 , C 2 , C 3 , and . . . are obtained by packetizing an electric power energy. Meanwhile, the client  200  outputs information packets D 1 , D 2 , D 3 , and . . . that are the information signals transmitted and received to and from the power supply server  100  so as to receive electric power supply from the power supply server  100 . 
         [0036]    The power supply server  100  outputs the synchronous packets A 1 , A 2 , A 3 , and . . . at the start of a time slot of a predetermined interval (for example, every 1 second). The time slot includes an information slot through which the information packet is transmitted and a power slot through which the power packet is transmitted. Information slots IS 1 , IS 2 , IS 3 , and . . . are sections where the information packets are exchanged between the power supply server  100  and the client  200 . Power supply slots PS 1 , PS 2 , PS 3 , and . . . are sections where the power packets C 1 , C 2 , C 3 , and . . . supplied from the power supply server  100  to the client  200  are output. The information packet is a packet capable of performing output only in the sections of the information slots IS 1 , IS 2 , IS 3 , and . . . . Thus, when the transmission and reception of the information packet is not completed in one information slot, the information packet is transmitted over a plurality of information slots. Meanwhile, the power packet is a packet capable of performing output only in the sections of the power supply slots PS 1 , PS 2 , PS 3 , and . . . . 
         [0037]    The power supply server  100  has one or two or more server power supply profiles showing a power specification that can be supplied by itself. Exemplary power specifications may include parameters of voltage range, amperage, duty cycles, AC frequency or DC. The client  200  receives the electric power supply from the power supply server  100  which can supply electric power matching to its own specification. At this time, the client  200  obtains a server power supply profile from the power supply server  100  and determines the specification (server power supply profile) of the power supply server  100  for the client  200  itself. Specifically, the client  200  first detects a synchronous packet A 1  to be output to the power supply server  100  and obtains the address of the power supply server  100  included in the synchronous packet A 1 . The address may be a MAC address, for example. Next, the client  200  transmits to the power supply server  100  an information packet D 1  that requests transmission of the number of the server power supply profiles possessed by the power supply server  100 . 
         [0038]    The power supply server  100  having received the information packet D 1  transmits a server power supply profile number in the information packet B 1 . The server power supply profile number is the number of the server power supply profiles of the power supply server  100 . The client  200  having received the information packet B 1  obtains from the power supply server  100  the contents of the server power supply profile with the number equal to the number of the server power supply profiles of the power supply server  100 . For example when the power supply server  100  has two server power supply profiles, the client  200  first obtains one of the two server power supply profiles. The client  200  having received one of the two server power supply profiles transmits to the power supply server  100  the server power supply profile as the information packet D 2  requesting the use of the power supply. 
         [0039]    The power supply server  100  having received the information packet D 2  transmits a first server power supply profile as the information packet B 2  to the client  200 . The first server power supply profile is stored in a storage part (not shown) included in the power supply server  100 . The client  200  having received the information packet B 2  from the power supply server  100  transmits the information packet for use in obtaining a second server power supply profile. However, the information slot IS 1  terminates at this point, and the power supply slot PS 1  for use in transmitting the power supply packet starts. Thus, this information packet is transmitted in the next information slot IS 2 . In the power supply slot PS 1 , since the power specification that the client  200  receives electric power from the power supply server  100  is not determined, and the electric power supply is not performed. 
         [0040]    The power slot PS 1  terminates, and the synchronous packet A 2  showing the start of the next time slot is output from the power supply server  100 . Thereafter, the client  200  having received the information packet B 2  from the power supply server  100  transmits the information for use in obtaining the second server power supply profile as the information packet D 3 . 
         [0041]    The power supply server  100  having received the information packet D 3  transmits the second server power supply profile as the information packet B 3  to the client  200 . The second server power supply profile is stored in a storage part (e.g., a memory such as a semiconductor memory, not shown) included in the power supply server  100 . The client  200  having received the information packet B 3  to obtain the two server power supply profiles of the power supply server  100  selects the server power supply profile with a power specification matching to the client  200  itself. The client  200  then transmits to the power supply server  100  the information packet D 4  for use in determining the selected server power supply profile. 
         [0042]    The power supply server  100  having received the information packet D 4  transmits information, which serves as the information packet B 4  and represents such a response that the power specification is determined, to the client  200  so as to notify the completion of the determination of the first server power supply profile to the client  200 . Thereafter, when the information slot IS 2  terminates and the power slot PS 2  starts, the power supply server  100  outputs the power supply packet C 1  to the client  200  and performs power supply. With regard to the timing of transmission of the power packet, a power supply start time can be designated by the client  200  to the power supply server  100  by using the information representing a transmission start time setting request. 
         [0043]    Hereinbefore, the power supply processing by the power supply system  1  according to the above-described embodiments has been described. 
         [0044]    As described above, in the power supply system  1 , there is a synchronous server integrating the entire system. The synchronous server starts to output the synchronous packet to the bus line, and other server and client detecting the synchronous packet are registered as a member of the system. Then, the client and the server negotiate on the specification of the supplied power through the bus line. Hereinafter, the transmission of packets from the synchronous server and the execution of the negotiation between the client and the server by wireless communication will be described. 
         [0045]    In the system disclosed in the Patent Literature 2, for example, since a signal and electric power flow on the same bus line, the client and the server receive the synchronous packet from the synchronous server to thereby automatically understand that the synchronous packet is on a certain system. Moreover, there is no recognition of multiple power servers, and therefore a client could not discriminate between power servers if multiple power servers were present. Meanwhile, when the communication path is wireless, even if the client and the server receive the synchronous packet, it is not sure if the synchronous packet is transmitted from the synchronous server connected to the same power system supplying electric power. 
         [0046]    Thus, in the present embodiment, a method of detecting that each device is on the same power supply line using wireless communication will be described. The present  is based on the electric power being supplied through a wire. First, a constitution example of the power supply server according to the first embodiment of the present invention will be described. 
       1-3. Constitution Example of Power Supply Server 
       [0047]      FIG. 3  is an explanatory view showing a constitution of the power supply server  100  according to the first embodiment. Hereinafter, the constitution of the power supply server  100  according to the first embodiment will be described using  FIG. 3 . 
         [0048]    As shown in  FIG. 3 , the power supply server  100  according to the first embodiment is configured to include a connector  101 , connecting wires  102  and  106 , a main switch  103 , a modem  104 , a microprocessor  105 , a power supply source  107 , a fuse  109 , an antenna  110 , a sub switch  111 , a resistor  112 , and a sub voltage supply  113 . A subset or all of connection  101 , wires  102  and  106 , and antenna  110  may be a part of an electrical interface. 
         [0049]    The connector  101  connects a power supply server body and the bus line  10  (an example of a common medium) by connecting to the connector  11 . The connecting wire  102  is used for connecting the connector  101  and the power supply server body. The main switch  103  controls an electric power output. When the main switch  103  is turned on, the power supply server  100  can convey electric power from the power supply source  107  to the bus line  10 , which may be used to provide operational power to the client. By the way, the operational power needed not be used immediately by the client, but may be stored at the client and used at a later time. Meanwhile, when the main switch  103  is turned off, the power supply server  100  can stop the electric power supply from the power supply source  107 . 
         [0050]    The modem  104  is used for transmitting and receiving information to and from other power supply server and client via the common medium, which in this case is the bus line  10 . While the modem  104  transmits a communication signal to the antenna  110 , the modem  104  receives the communication signal wirelessly received by the antenna  110 . 
         [0051]    The microprocessor  105  controls the operation of the power supply server  100 . When negotiation between the power supply server  100  and the client (for example, the client  200  of  FIG. 1 ) is completed, the microprocessor  105  turns on the main switch  103  so that electric power is supplied from the power supply source  107 , whereby the electric power can be supplied to the bus line  10 . 
         [0052]    The connecting wire  106  is used for connecting the power supply server body and the power supply source  107 . The power supply source  107  can supply electric power including DC voltage. When the main switch  103  of the power supply server  100  is turned on, DC power can be supplied to the bus line  10 . The fuse  109  is used for protecting circuits from high current. If a current higher than a rated current flows, the fuse  109  cuts itself by its own generated heat to prevent flow of high current. 
         [0053]    The antenna  110  transmits and receives a signal wirelessly. The antenna  110  receives signals wirelessly transmitted from another server (the synchronous server or the power supply server) and client and wirelessly transmits signals to other server and client. When the antenna  110  wirelessly receives a signal from the other server and client, the signal is transmitted to the modem  104  to be subjected to demodulation processing in the modem  104 . The signal subjected to the modulation processing in the modem  104  is wirelessly transmitted from the antenna  110  to arrive at other server and client. 
         [0054]    The sub switch  111  switches connection between the connecting wire  102  and the resistor  112  and is constituted so as to be switched on and off by control of the micro-processor  105 . The resistor  112  and the sub voltage supply  113  are used for supplying a predetermined DC voltage V from the sub voltage supply  113  to the bus line  10  by the connection of the sub switch  111 . The predetermined voltage V may be fixed or varied. The resistor  112  is provided so as to prevent devices in the power supply server  100  from being broken by a short circuit occurring in the power supply server  100 . 
         [0055]    Hereinbefore, the constitution of the power supply server  100  according to the first embodiment of the present invention has been described using  FIG. 3 . Next, the operation of the power supply server  100  according to the first embodiment will be described. In the following description, the operation of the power supply server  100  in the case where the power supply server  100  is also operated as a synchronous server will be described. 
       1-4. Operation Example of Power Supply Server) 
       [0056]    In the power supply system  1 , when negotiation between the client and the server is completed, and the client knows which server it is communicating with and has set the specification for the power to be supplied, the power supply server starts electric power supply, and the client is in a state capable of receiving the electric power supply. Moreover, in the negotiation, information of a unique ID for use in uniquely specifying the power supply system may be shared between the server and the client. When the power supply server  100  is operated as the synchronous server, the microprocessor  105  wirelessly transmits a synchronous packet (message content) through the modem  104  and the antenna  110 . The microprocessor  105  then turns on the sub switch  111  for an appropriate time (for example, a guard time between power packets defined by the power supply system  1 ). The sub switch  111  is connected to the sub voltage supply  113  outputting a predetermined voltage V through a specified impedance (the resistor  112 ). Thus, during the above time, the predetermined voltage V from the sub voltage supply  113  appears on the bus line  10 . 
         [0057]    Thus, the connection to the power supply system  1  can be determined by whether or not the voltage V from the sub voltage supply  113  can be detected at the timing of wirelessly receiving the synchronous packet. The value of the voltage V is broadcasted as a parameter of the synchronous packet wirelessly transmitted from the antenna  110 . Further, the value of the voltage V may be changed at each timing of transmitting the synchronous packet. 
         [0058]    By virtue of the appearance of the voltage V from the sub voltage supply  113  on the bus line  10 , even if there are a plurality of wireless synchronous packets, each server and client connected to the bus line  10  can specify a power transmission and distribution system to which the server and client are connected or whether they are not connected thereto. The synchronous packet transmitted from the power supply server  100 , operated as the synchronous server, is transmitted including the unique ID of the power supply system  1  to which the power supply server  100  belongs. Thus, each server and client having received the synchronous packet from the power supply server  100  can uniquely specify the power transmission and distribution system. 
         [0059]      FIG. 4A  is an explanatory view showing a change of a voltage observed on the bus line  10 .  FIG. 4A  shows a change of a voltage on a bus line in the power supply system (in related art) free from the voltage V from the sub voltage supply  113 . As shown in  FIG. 4A , in the system disclosed in the Patent Literature 2, for example, a no-voltage section (a guard section) free from voltage exists between slots to which electric power from the power supply server is supplied. 
         [0060]      FIG. 4B  is an explanatory view showing a change of a voltage observed on the bus line  10 .  FIG. 4B  shows a change of a voltage observed on the bus line  10  in the power supply system  1  according to the first embodiment.  FIG. 4B  also shows the synchronous packet wirelessly transmitted from the synchronous server (the power supply server  100 ) on the same time axis. As shown in  FIG. 4B , in the power supply system  1  according to the first embodiment, the predetermined voltage V supplied from the synchronous server (the power supply server  100 ) is observed in the guard section. The synchronous packet wirelessly transmitted from the synchronous server (the power supply server  100 ) includes the information of the voltage V and the unique ID of the power supply system  1 . Thus, when the voltage value of the voltage V appearing on the bus line and the information of the voltage value included in the synchronous packet received at the timing when the voltage V appears on the bus line coincide with each other, the server and the client connected to the bus line on which the voltage shown in  FIG. 4B  is observed can specify the power transmission and distribution system to which they belong. 
         [0061]      FIG. 5  is a flow chart showing a voltage detection processing in the server and the client having received the synchronous packet in the power supply system  1  according to the first embodiment. Hereinafter, the voltage detection processing in the server and the client having received the synchronous packet will be described using  FIG. 5 . In the following description, the server and the client wirelessly receiving the content from synchronous server are simply referred to as a “device”. 
         [0062]    The device under the power supply system  1  first receives the synchronous packet (e.g., message content) wirelessly transmitted from the synchronous server (step S 101 ). The device having received the synchronous packet demodulates the synchronous packet by the modem to decode the synchronous packet by the microprocessor, and, thus, to obtain information of a system ID (step S 102 ) and, at the same time, obtain voltage data included in the synchronous packet (step S 103 ). 
         [0063]    Then, the device measures the voltage appearing on the bus line  10  at the timing of receiving the synchronous packet (step S 104 ) to determine whether or not the measured result and the voltage data obtained in step S 103  coincide with each other (step S 105 ). As the result of the determination in step S 105 , if the measured result does not coincide with the voltage data obtained in step S 103 , the flow returns to step S 101 , and the device receives the synchronous packet wirelessly transmitted from the synchronous server. Meanwhile, as the result of the determination in step S 105 , when the measured result coincides with the voltage data obtained in step S 103 , the device confirms the ID of the power supply system obtained in step S 102  (step S 106 ). 
         [0064]    In the system disclosed in the Patent Literature 2 and the like, the power supply system does not have the ID for use in uniquely specifying the system. This is because, in the example of related art, information and electric power flow on the same bus line through a wire, and since only one power supply system exists on one bus line in principle, no information of uniquely specifying the system is necessary. Meanwhile, in the present embodiment, since the synchronous packet is wirelessly transmitted, the server and the client having received the synchronous packet specify that the synchronous packet has been transmitted from a particular one of the synchronous servers. 
         [0065]    Thus, in the present embodiment, an appropriate DC voltage output from the synchronous server (the power supply server  100 ) has a certain impedance (the resistor  112 ) to be output to the bus line  10  for a guard section. The server and the client detecting the DC voltage perform determination of the voltage having a high input impedance and existing on the bus line  10 . 
         [0066]    The voltage on the bus line  10  is monitored simultaneously by a plurality of devices, and the total impedance of the devices may cause slight reduction in voltage. Also in this case, since a voltage of a detected voltage pulse is described in the synchronous packet transmitted from the synchronous server, the voltage value can be easily determined from the transition of the voltage value described in the synchronous packet. In another server and client, by virtue of the provision of a voltage detector that detects the voltage level appearing on the bus line  10  in the guard section, even if the communication system is completely wireless, it is possible to determine whether each power supply server and client are connected to one power transmission and distribution system or whether they are not connected thereto. 
         [0067]    The above method enables each device to specify a group of a wired power connection using a wireless connection to allow the use of the method disclosed in the Patent Literature 2 and the like, such as the determination of the synchronous server, the specification of the power supply server and a power supply client existing on the system, the negotiation between the server and the client, and the transmission and reception of electric power. 
         [0068]    In the above description, in order to know that the server and the client exist on the same wired bus line, there has been shown the method in which the synchronous server sends an appropriate DC voltage for the guard section between power slots, and the DC voltage is detected in other servers and clients. In the following method, the output of the DC voltage in the guard period of time is not performed, only the ID uniquely distinguishing the power supply system is used, and the ID is transmitted and received in a wireless communication link. 
         [0069]    In the above method, an ID is provided in the power supply system, and a system to which the ID is broadcasted as a parameter by wireless transmission is assumed. The parameter is appropriately a parameter of a synchronous packet, and the server and the client receiving the synchronous packet can recognize the ID of the power bus system to which the server and the client belong. The ID may be set long enough so as to be uniquely identifiable over the world or may be set shorter, but still sufficiently large enough to prevent overlap in a particular vicinity. 
         [0070]    In the server and the client connected to the electric supply system having the ID, a human (for example, an administrator of the system) previously sets the ID in the construction of the system. Namely, when the power supply system having a plurality of wireless signal links exists, the system to which the server and the client will be connected is set manually. According to this constitution, even if actual electric power transfer is not performed between the server and the client, when the systems have the same ID, they can be confirmed as belonging to the same system. 
         [0071]    Thus, unlike with the system described in the Patent Literature 2, the ID of the power supply system is provided as a parameter in the wirelessly transmitted synchronous packet, and the ID can be set manually. 
         [0072]    In the power supply system using the method of wirelessly transmitting and receiving only ID, if a setting error of ID occurs for the server and client, the electric power transfer may not be impossible to be performed between the server and the client. In the server or client for which the setting error of ID occurs, it is determined that there is no system in a protocol shown in the power supply system disclosed in the Patent Literature 2 and the like, whereby the relevant server or client is automatically separated from the system. Thus, in this case, the relevant server or client displays that “it is not connected to the system” to notify to a user, whereby the user can know the trouble. 
       2. Second Embodiment of the Present Invention  
       [0073]    In the above description, there has been described the power supply system in which, although electric power is supplied through a wire, information is transmitted and received wirelessly. Next, there will be described a power supply system in which both the electric power supply and the transmission and reception of information are performed wirelessly. The following description assumes that the ID of the power supply system is set manually, although other automated methods of setting the ID may be used. 
         [0074]    Since a power transfer line is not a bus line but a space (e.g., an air gap or other propagation medium), transferable electric power is not DC but AC. Nevertheless, this space is a type of medium for conveying information and electromagnetic energy. In the present embodiment, the form in which the energy is conveyed is not limited, and so the form of electric energy may be AC, which may be used to excite an antenna and produce or receive electromagnetic energy (which includes electric or magnetic energy). However, even if electric power is DC, mere existence of one bus line and another bus line through which one wants to transmit and receive electric power makes a difference in construction of a mechanism of efficient power transfer between the bus lines. Thus, in the present embodiment, there will be described a case where the electric power supply and the transmission and reception of information can be performed wirelessly using a power coupler (a type of interface) in the exchange of electric power. 
       2-1. Constitution of Power Supply System 
       [0075]      FIG. 6  is an explanatory view showing a power supply system  2  according to a second embodiment. Hereinafter, the constitution of the power supply system  2  according to the second embodiment will be described using  FIG. 6 . 
         [0076]    As shown in  FIG. 6 , the power supply system  2  according to the second embodiment is configured to include a power supply server  300  and a client  400 . 
         [0077]    The power supply server  300  is configured to include a connector  301 , connecting wires  302  and  306 , a main switch  303 , a modem  304 , a microprocessor  305 , a power supply source  307 , a driver  309 , an antenna  310 , a coupling coil  311 , and a wireless transmitting/receiving circuit  312 . 
         [0078]    The client  400  is configured to include a connector  401 , connecting wires  402  and  406 , a main switch  403 , a modem  404 , a microprocessor  405 , a load  407 , an AC/DC converter  408 , a battery  409 , an antenna  410 , a coupling coil  411 , and a wireless transmitting/receiving circuit  412 . 
         [0079]    First, the constitution of each component of the power supply server  300  will be described. The connector  301  is used for connecting a power supply server body and a bus line  30 . The connecting wire  302  is used for connecting the connector  301  and the power supply server body. The main switch  303  controls electric power output. When the main switch  303  is located at an “a” position, electric power can be supplied to the bus line  30  through a wire. When the main switch  303  is located at a “c” position, electric power can be wirelessly supplied through a power coupler. When the main switch  303  is located at a “b” position, the wired and wireless electric power supply is stopped. As the main switch  303 , a mechanical switch may be used. 
         [0080]    The modem  304  is used for transmitting and receiving information between other power supply server and client through a wire. The wireless transmitting/receiving circuit  312  is used for wirelessly transmitting and receiving information between other power supply server and client through the antenna  310 . The wireless transmitting/receiving circuit  312  transmits the communication signal to the antenna  310  and receives the communication signal wirelessly received by the antenna  310 . 
         [0081]    The microprocessor  305  is used for controlling the operation of the power supply server  300 . For example, when negotiation between the power supply server  300  and the client  400  is completed, the microprocessor  305  sets the main switch  303  to the “c” position so that electric power is supplied from the power supply source  307 , whereby electric power can be supplied to the client  400  through the coupling coils  311  and  411 . 
         [0082]    The connecting wire  306  is used for connecting the power supply server body and the power supply source  307 . The power supply source  307  can supply electric power including AC voltage. When the main switch  403  of the power supply server  300  is set to the “a” position or the “c” position, electric power can be supplied through a wire or wirelessly. 
         [0083]    The driver  309  drives electric power from the power supply source  307  with a frequency optimized for the coupling coil  311 . The AC power with the frequency optimized for the coupling coil  311  is output to the coupling coil  311  by the driver  309 . 
         [0084]    The antenna  310  transmits and receives signals wirelessly. The antenna  310  receives signals wirelessly transmitted from other server (the synchronous server and the power supply server) and client and wirelessly transmits signals to other server and client. When the antenna  310  wirelessly receives signals from other server and client, the signal is transmitted to the wireless transmitting/receiving circuit  312  to be subjected to the demodulation processing in the wireless transmitting/receiving circuit  312 . The signal subjected to the demodulation processing in the wireless transmitting/receiving circuit  312  is wirelessly transmitted from the antenna  310  to arrive at other server and client. 
         [0085]    Hereinbefore, the constitution of each component of the power supply server  300  has been described. Next, the constitution of the client  400  will be described. The connector  401  connects client body and a bus line  40 . The connecting wire  402  is used for connecting the connector  401  and the client body. The main switch  403  controls electric power input. When the main switch  403  is located at the “a” position, it becomes possible to receive the electric power supply from the bus line  40  through a wire, and if the main switch  403  is located at the “c” position, it becomes possible to wirelessly receive the electric power supply through a power coupler. When the main switch  403  is located at the “b” position, the wired or wireless electric power supply through a wire or wirelessly is stopped. As the main switch  403 , a mechanical switch may be used. 
         [0086]    The modem  404  is used for transmitting and receiving information between other power supply server and client. The wireless transmitting/receiving circuit  412  is used for wirelessly transmitting and receiving information between other power supply server and client through the antenna  410 . The wireless transmitting/receiving circuit  412  transmits the communication signal to the antenna  410  and receives the communication signal wirelessly received by the antenna  410 . 
         [0087]    The microprocessor  405  controls the operation of the client  400 . For example, when negotiation between the power supply server  300  and the client  400  is completed, the microprocessor  405  sets the main switch  403  to the “c” position so as to receive electric power supplied from the power supply server  300 , whereby it becomes possible to receive electric power supplied from the power supply server  300  through the coupling coils  311  and  411 . 
         [0088]    The connecting wire  406  is used for connecting the client body and the load  407 . The load  407  is a block consuming electric power supplied from the power supply server. The AC/DC converter  408  is a rectification circuit for use in converting AC current supplied from the power supply server  300  through the coupling coils  311  and  411  to DC current with different voltage. The battery  409  stores electric power supplied from the power supply server. Although not illustrated in  FIG. 6 , the client  400  may include a charge control circuit controlling charge and discharge of the battery  409 . 
         [0089]    The antenna  410  transmits and receives signals wirelessly. The antenna  410  receives signals wirelessly transmitted from other server (the synchronous server and the power supply server) and client wirelessly transmits signals to other server and client. When the antenna  410  wirelessly receives a signal from other server and client, the signal is transmitted to the wireless transmitting/receiving circuit  412  to be subjected to the demodulation processing in the wireless transmitting/receiving circuit  412 . The signal subjected to the demodulation processing in the wireless transmitting/receiving circuit  412  is wirelessly transmitted from the antenna  410  to arrive at other server and client. 
         [0090]    The coupling coil  411  is provided so as to pair with the coupling coil  311 . The coupling coils  311  and  411  constitute the power coupler. 
         [0091]    Hereinbefore, the constitution of the client  400  has been described. Next, the operation of the power supply server  300  and the client  400  having the above constitution shown in  FIG. 6  will be described. In this example, the client  400  is already assigned an appropriate address and is in a state capable of receiving electric power from the power supply server  300 . 
         [0092]      FIG. 7  is a flow chart showing the exchange of the power server ID, and return data prior to the power server conveying power to the client. The process begins in step S 1000  where the server prepares a message and then transmits the message in step S 1001  with the power server ID. The process then proceeds to step S 1002  where the client transmits return data. This return data may indicate the requested power profile for the particular client device. The process then proceeds to step S 1003  where the power server conveys the power to the client in the requested format. The process then proceeds to step S 1004  where the client uses the power conveyed from the power server to operate the client. 
       2-2. Operation of Power Supply System 
       [0093]    When the power supply server  300  starts operation, the power supply server  300  receives the synchronous packet through a wireless signal link (for example, the antenna  310 ) to register itself as the power supply server on the synchronous server existing on the bus line  20  side. Namely, the power supply server  300  transmits a registration packet for the synchronous server from the antenna  310 , and the client  400  having received the registration packet from the power supply server  300  through the antenna  410  transmits the registration packet, received from the power supply server  300 , to the synchronous server through the modem  404  and the microprocessor  405 . 
         [0094]    The power supply server  300  is assigned an address, and such information that the new power supply server  300  is connected to the bus line  20  is broadcasted from the synchronous server to the server and the client connected to the bus line  20 . Although the information is notified to the power supply server  300  as well through the antenna  310 , the power supply server  300  does not respond to the information. Consequently, the client  400  can know the addition of the new power supply server  300 . Since the client  400  has not been received the supply of electric power, the client  400  starts negotiations with the registered power supply server  300 . 
         [0095]    When negotiation between the power supply server  300  and the client  400  is successfully performed, the power supply server  300  and the client  400  respectively set the main switches  303  and  403  on the c side so that electric power can be wirelessly supplied by the power coupler. Then, electric power is transmitted between the power supply server  300  and the client  400  through the coupling coils  311  and  411 . Since the timing of transmitting and receiving electric power is controlled by the synchronous server (not shown) connected to the bus line  20 , the power slot of the bus line  20  is allocated, and the time of the power slot is used. 
         [0096]    Depending on the connection conditions between the coupling coils  311  and  411 , the electric power having a similar specification to that obtained by the negotiation between the power supply server  300  and the client  400  is not obtained. Thus, the client  400  may check the contents of electric power received from the power supply server  300  (by means of the microprocessor  405 , for example). As a result of the check, when electric power is adjusted, the client  400  negotiates with the power supply server  300  again, and if the power supply server  300  has a mechanism for adjusting electric power, the power specification may be changed on the power supply server  300  side so that electric power is optimal at a power receiving end. Of course, if the power supply server  300  does not have the mechanism for adjusting electric power, the client  400  receives some electric power and thereafter may abandon the reception of electric power from the power supply server  300 . However, in the power supply server which can supply electric power wirelessly, in order to correspond to a variation of the power conditions due to a wireless link, adjustable electric power capability is preferably provided. When referring to supplying (or conveying) electric “power” wirelessly, this description covers the conveyance of energy from one device to another that is later used to provide operational power to the receiving device. 
         [0097]    Hereinbefore, the operation of the power supply server  300  and the client  400  has been described. In the power supply server  300  and the client  400  having the constitution shown in  FIG. 6 , the switching of the main switches  303  and  403  allows transmission and reception of electric power through a wire, and the power supply server  300  and the client  400  can be connected as they are to an existing power supply system. 
         [0098]    In the second embodiment, the time slot used by the power link is under the complete control of the power supply system around the bus line  20 . However, the power link by the coupling coils  311  and  411  can operate completely independently from the power supply system around the bus line  20 . Thus, in a pair of server and client having a wireless power link, there can be realized such a usage that, after agreements are obtained by negotiation between the server and the client, connection by a power coupler of the power link is maintained. 
         [0099]    In order to correspond to the above usage, in the present embodiment, parameters being “wireless power link” and “the number of connectable links” are provided in a profile of the server and the client. Then, the conditions of negotiation between a pair of the server and the client having the wireless power link are extended to include conditions such as “always-on connection” and “connection and disconnection by the agreements between the server and the client”. The “always-on connection” in this case is performed just under the control of the microprocessors  305  and  405 , and electric power lines are not permanently connected. Namely, the “always-on connection” means that although the power link can be cut at any time as intended by the micro-processors  305  and  405 , the usage is continued for a time. 
         [0100]    In the second embodiment, a pair of the wireless power links is provided, and there is a one-to-one wireless power link. However, in the power link using a magnetic field, if the efficiency is somewhat compromised, one-to-many and many-to-many links can be constituted. When the wireless power link is one-to-many (the power transmitting side: 1 and the power receiving side: many), the time slot is provided, and electric power can be transmitted time-divisionally or simultaneously to a plurality of clients. When electric power is transmitted time-divisionally, by virtue of the use of a protocol executing the operation as describe above, the power specification agreed between the server and the client can be used. Meanwhile, in the simultaneous power transmission to a plurality of clients, although optimization for each client may not be impossible to be performed, it is possible to use such a power specification usable by all clients. Further, it is possible to prevent the client that is not matching the power specification from receiving electric power on the client side. 
       3. Conclusion 
       [0101]    According to each embodiment as described above, it is possible to constitute a server, a client, and a power supply system including the server and the client, in which communication is performed separately from electric power transfer and the communication is performed wirelessly. Further, electric power can be transferred not only through a wire, but also wirelessly. 
         [0102]    It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof. 
         [0103]    The present application contains subject matter related to that disclosed in Japanese Priority Patent Application JP 2009-244424 filed in the Japan Patent Office on Oct. 23, 2009, the entire content of which is hereby incorporated by reference. 
         [0104]    The present invention can be applicable to a power supply device, a power receiving device, a power supply system, and a power supply method. 
       ELEMENT NUMBER LISTING 
       [0105]      1 , 2  power supply system 
         [0106]      100  power supply server 
         [0107]      101  connector 
         [0108]      102  connecting wire 
         [0109]      103  main switch 
         [0110]      104  modem 
         [0111]      105  microprocessor 
         [0112]      106  connecting wire 
         [0113]      107  power supply source 
         [0114]      109  fuse 
         [0115]      110  antenna 
         [0116]      111  sub switch 
         [0117]      112  resistor 
         [0118]      113  sub voltage supply 
         [0119]      200  client 
         [0120]      300  power supply server 
         [0121]      301  connector 
         [0122]      302 , 306  connecting wire 
         [0123]      303  main switch 
         [0124]      304  modem 
         [0125]      305  microprocessor 
         [0126]      307  power supply source 
         [0127]      309  driver 
         [0128]      310  antenna 
         [0129]      311  coupling coil 
         [0130]      312  wireless transmitting/receiving circuit 
         [0131]      400  client 
         [0132]      401  connector 
         [0133]      402 , 406  connecting wire 
         [0134]      403  main switch 
         [0135]      404  modem 
         [0136]      405  microprocessor 
         [0137]      407  load 
         [0138]      408  AC/DC converter 
         [0139]      409  battery 
         [0140]      410  antenna 
         [0141]      411  coupling coil 
         [0142]      412  wireless transmitting/receiving circuit