Abstract:
A non-contact power transmission apparatus that includes a power supply circuit that generates electrical power; a switch connected to an output of the power supply circuit; a first power transmission antenna connected to a first output of the switch; a second power transmission antenna connected to a second output of the switch; a communication interface that communicates with a device; and a control unit that controls the switch based on a state of the device obtained via the communication interface.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application claims the benefit of the earlier filing date of U.S. Provisional Patent Application Ser. No. 61/449,203 filed on Mar. 4, 2011, the entire contents of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE DISCLOSURE 
     1. Field of the Disclosure 
     The present disclosure relates to a non-contact power transmission apparatus that supplies electrical power to a secondary battery in an electronic apparatus. 
     2. Description of Related Art 
     In recent years, a power source has been provided that can charge a secondary battery in a terminal device in a non-contact state in which a terminal of another device, such as a charging device, that supplies power, or the like is not connected to the terminal device. 
     As a non-contact power transmission method that has hitherto been performed, an electromagnetic induction method is known. This is such that a power transmission coil is arranged in an apparatus on the side in which electrical power is transmitted, and a power receiving coil is arranged on the power-receiving-side terminal device. In this electromagnetic induction method, the power transmission coil of the power-transmission-side apparatus is brought into proximity of the power receiving coil of a power-receiving-side apparatus, both the coils are flux-coupled, and electrical power is supplied in a non-contact manner. 
     This electromagnetic induction method is a non-contact power transmission technology that has hitherto been known. The transmissible distance is approximately several mm, and electrical power can be transmitted only among devices that are very near. For this reason, currently, the electromagnetic induction method is used in some devices, such as water-proof terminal devices in which it is difficult to expose a charging terminal. 
     In comparison, in recent years, as a method for efficiently supplying electrical power in a non-contact manner to a terminal device at a long distance to a certain degree, a method called a magnetic-field resonance method has begun to be developed and put into the market. This is such that an LC circuit formed of a coil, a capacitor, and the like is provided in each of a power-transmission-side apparatus and a power-receiving-side apparatus, and magnetic fields are made to resonate between both the circuits, thereby transmitting electrical power in a wireless manner. In order to cause the magnetic fields to resonate between both the circuits, it is necessary to make the frequencies at which the resonance is performed equal to each other. 
     In the case of the magnetic-field resonance method, transmission at a short distance of approximately several cm to several m becomes possible. Furthermore, if there are a plurality of power-receiving-side apparatuses within the transmissible range, electrical power transmission can be performed simultaneously from one power-transmission-side apparatus to the plurality of power-receiving-side apparatuses. 
     A technology is described in Japanese Unexamined Patent Application Publication No. 2010-183812 in which, in order to improve the efficiency of non-contact power transmission, a plurality of primary side coils are arranged in one row in a horizontal direction on the power transmission side, and coils which are combined in which the electrical power transmission efficiency is high are selected when electrical power is to be transmitted to a secondary side coil. 
     As described above, in a case where a plurality of secondary side coils are arranged in one row in a horizontal direction, it is possible to deal with a position displacement of the power-receiving-side apparatus with respect to the direction in which the secondary side coils are arranged. However, in a case where the position is displaced in a direction different from the direction in which the secondary side coils are arranged, it is not possible to increase transmission efficiency even if any of the coils is used. Furthermore, if a large number of secondary side coils are to be arranged, the configuration of the power-transmission-side apparatus becomes complex as the number of coils arranged increases. 
     In addition, in the case of the magnetic-field resonance method, electrical power can be transmitted from a primary side coil to a plurality of power-receiving-side apparatuses. However, if a large primary side coil is arranged, which can efficiently transmit electrical power to a plurality of power-receiving-side apparatuses at the same time, efficiency is not good much when electrical power is transmitted to only one power-receiving-side apparatus by the one large primary side coil. 
     SUMMARY 
     The inventors of the present application have recognized necessity of performing efficient electrical power transmission with a simple configuration in a case where non-contact power transmission is to be performed from a charging device to a terminal device. 
     According to a first exemplary embodiment, the disclosure is directed to a non-contact power transmission apparatus that includes a power supply circuit that generates electrical power; a switch connected to an output of the power supply circuit; a first power transmission antenna connected to a first output of the switch; a second power transmission antenna connected to a second output of the switch; a communication interface that communicates with a device; and a control unit that controls the switch based on a state of the device obtained via the communication interface. 
     According to another exemplary embodiment, the disclosure is directed to a method performed by a non-contact power transmission apparatus. The method includes generating, by a power supply circuit, electrical power to be provided to one of a first power transmission antenna and a second power transmission antenna, which are each connected to an output of the power supply circuit via a switch; communicating, via a communication interface, with a device; and controlling, by a control unit, the switch based on a state of the device obtained from the device via the communicating. 
     According to another exemplary embodiment, the disclosure is directed to a computer-readable medium including computer program instructions, which when executed by a non-contact power transmission apparatus, cause the non-contact power transmission apparatus to perform a method comprising: controlling a switch, which is connected between a power supply circuit that generates power and first and second power transmission antennas, based on a state of a device received via a communication interface of the non-contact power transmission apparatus. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view illustrating a non-contact power transmission apparatus according to a first embodiment of the present disclosure. 
         FIG. 2  is a block diagram illustrating the configuration of a charging device according to the first embodiment of the present disclosure. 
         FIG. 3  is an exploded perspective view illustrating an antenna arranged state according to the first embodiment of the present disclosure. 
         FIG. 4  is a plan view illustrating an antenna arranged state according to the first embodiment of the present disclosure. 
         FIG. 5  is a side view illustrating an antenna arranged state according to the first embodiment of the present disclosure. 
         FIG. 6  is a block diagram illustrating the configuration of a power-receiving-side terminal device according to the first embodiment of the present disclosure. 
         FIG. 7  is an illustration illustrating transmission efficiency according to the first embodiment of the present disclosure. 
         FIG. 8  is a flowchart illustrating the flow of a power transmission process according to the first embodiment of the present disclosure. 
         FIG. 9  is an illustration illustrating an example in which a terminal device is arranged according to the first embodiment of the present disclosure. 
         FIG. 10  is an illustration illustrating an example in which a terminal device is arranged according to the first embodiment of the present disclosure. 
         FIG. 11  is an illustration illustrating an example in which a terminal device is arranged according to the first embodiment of the present disclosure. 
         FIG. 12  is a perspective view illustrating a charging device according to a second embodiment of the present disclosure. 
         FIG. 13  is a side view illustrating the charging device according to the second embodiment of the present disclosure. 
         FIG. 14  is a perspective view illustrating a charging device according to a third embodiment of the present disclosure. 
         FIG. 15  is a side view illustrating the charging device according to the third embodiment of the present disclosure. 
         FIG. 16  is a perspective view illustrating a charging device according to a fourth embodiment of the present disclosure. 
         FIG. 17  is a side view illustrating the charging device according to the fourth embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, embodiments of the present disclosure will be described in the following order. 
     1. First Embodiment 
     1.1 Example of shapes of charging device and terminal device ( FIG. 1 ) 
     1.2 Example of configuration of charging device ( FIG. 2 ) 
     1.3 Antenna arrangement of charging device ( FIG. 3  to  FIG. 5 ) 
     1.4 Example of configuration of terminal device ( FIG. 6 ) 
     1.5 Transmission efficiency at the time of power transmission ( FIG. 7 ) 
     1.6 Flow of power transmission process ( FIG. 8 ) 
     1.7 Example of arrangement of terminal device ( FIG. 9  to  FIG. 11 ) 
     2. Second Embodiment ( FIG. 12 ,  FIG. 13 ) 
     3. Third Embodiment ( FIG. 14 ,  FIG. 15 ) 
     4. Fourth Embodiment ( FIG. 16 ,  FIG. 17 ) 
     5. Modifications 
     1. First Embodiment 
     A first embodiment of the present disclosure will be described with reference to  FIGS. 1 to 11 . The present embodiment is a system that is constituted by a charging device that is a non-contact power transmission apparatus and a terminal device in which an incorporated battery is charged by electrical power that is transmitted from the charging device. Electrical power transmission from the charging device to the terminal device is performed in a non-contact manner by using a magnetic-field resonance method. Furthermore, in the present embodiment, the terminal device is used as a mobile phone terminal device. 
     1.1 Example of Shapes of Charging Device and Terminal Device 
       FIG. 1  illustrates an example of the shapes of a charging device and a terminal device of the first embodiment. 
     A charging device  200  is made up of a housing having a planar part  211  on the top surface thereof. As shown in  FIG. 1 , as a result of mounting a terminal device  100  on the planar part  211  of the charging device  200 , electrical power that is transmitted from a first power transmission antenna  201  or a second power transmission antenna  202  arranged inside the planar part  211  is supplied to the terminal device  100 , causing the battery inside the terminal device  100  to be charged. The example of  FIG. 1  shows that only one terminal device  100  is mounted on the planar part  211 . However, as will be described later, it is possible that a plurality of terminal devices are mounted on the planar part  211 , and these are charged at the same time. 
     1.2 Example of Configuration of Charging Device 
     Referring to  FIG. 2 , the configuration of a charging device of the present embodiment will be described. 
     The charging device  200  includes a high-frequency power-supply circuit  206  serving as a power-supply unit. A DC power supply in which a commercial AC power supply is rectified, or a DC power supply from a car battery, is supplied to the high-frequency power-supply circuit  206 . Inside the high-frequency power-supply circuit  206 , a high-frequency power supply at a frequency corresponding to the resonance frequency for non-contact electrical power transmission is generated from the supplied DC power supply. Then, information on the electrical power of the high-frequency power supply that is generated by the high-frequency power-supply circuit  206 , or the like, is supplied to a control unit  207 . 
     Furthermore, the high-frequency power-supply circuit  206  supplies the generated high-frequency power supply to only one of the first power transmission antenna  201  and the second power transmission antenna  202  through a switch  205 . The examples of the arrangement of the first power transmission antenna  201  and the second power transmission antenna  202  will be described later. The respective antennas  201  and  202  are each formed as a coil antenna in which a conductor is arranged in the form of a coil. 
     A matching circuit  203  is provided between the switch  205  and the first power transmission antenna  201 , and a matching circuit  204  is provided between the switch  205  and the second power transmission antenna  202 . Each of the matching circuits  203  and  204  is a circuit for performing adjustment of a frequency in a case where non-contact electrical power transmission is to be performed, and the like. 
     The selection of the antenna by the switching in the switch  205  is controlled by the control unit  207 . The control unit  207  performs a process for selecting an antenna in accordance with a predetermined processing procedure. The details of the processing procedure for selecting an antenna in the control unit  207  will be described later. 
     Furthermore, the charging device  200  includes a data communication processing unit  209  for performing wireless communication with adjacent terminal devices, and a data communication antenna  208  is connected to the data communication processing unit  209 . 
     The data communication processing unit  209  is a communication processing circuit acting as a short-distance wireless communication unit for performing wireless communication with terminal devices in proximity to the charging device  200 . For this data communication processing unit  209 , for example, a short-distance wireless method (near-field wireless method) called NFC (Near Field Communication) that is applied to wireless tags is used, and a data communication process with the other party in proximity (to a degree of approximately several cm) is performed. Alternatively, for the data communication processing unit  209 , a wireless LAN (Local Area Network) method, a Bluetooth (trademark) method, an infrared transmission method, or the like may be applied. 
     It is sufficient that the data communication processing unit  209  has a capability of performing wireless communication with a terminal device that is close to such a degree as to be in contact with the charging device  200 , and it is not necessary for the data communication processing unit  209  to perform wireless communication with a terminal device that is separated to such a degree as to not be able to perform non-contact power transmission. 
     Data communication by the data communication processing unit  209  is performed under the control of the control unit  207 . Since data communication is performed by the data communication processing unit  209 , the control unit  207  detects that a terminal device capable of receiving electrical power exists in the vicinity of the charging device  200 . Furthermore, when power transmission is to be started under the control of the control unit  207 , the control unit  207  causes the data communication processing unit  209  to perform data communication so as to perform an authentication process for a power-receiving-side terminal device, and also obtains information on the power receiving state from the terminal device. 
     1.3 Antenna Arrangement of Charging Device 
       FIGS. 3 to 5  illustrate a state in which the first power transmission antenna  201  and the second power transmission antenna  202  provided in the charging device  200  are arranged. 
     As shown in  FIG. 3 , the first power transmission antenna  201  and the second power transmission antenna  202  are formed as a conductor pattern formed in other printed boards  201   a  and  202   a , and the printed boards  201   a  and  202   a  are arranged in such a manner as to overlap each other inside the charging device  200 . 
     The power transmission antennas  201  and  202  are formed in such a manner that a conductor is wound a plurality of times in the form of a rectangle on the printed boards  201   a  and  202   a , respectively. The pattern of the conductor forming the first power transmission antenna  201  is arranged in a comparatively small area in almost the center on the printed board  201   a . That is, as shown in  FIG. 3 , the horizontal width W 1  and the vertical width H 1  at the place where the pattern of the conductor as the first power transmission antenna  201  is wound are set to comparatively small sizes. The horizontal width W 1  and the vertical width H 1  of this power transmission antenna  201  are sizes that are approximately equal to the horizontal width and the vertical width of a power receiving antenna provided in the power-receiving-side apparatus. 
     In contrast, a horizontal width W 2  and a vertical width H 2  at the place where the pattern of the conductor as the second power transmission antenna  202  is wound are set to be larger than the horizontal width W 1  and the vertical width H 1  of the first power transmission antenna  201 . For example, the horizontal width W 2  and the vertical width H 2  are set to a size that is almost equal to the size in a case where two terminal devices  100  are arranged side by side, or to a size larger than that. Furthermore, the conductor forming the second power transmission antenna  202  is arranged on the printed board  202   a  in a state in which a center unit  202   b  is formed. The center unit  202   b  in which this conductor is not arranged has a size larger than at least the horizontal width W 1  and the vertical width H 1  of the first power transmission antenna  201 . 
     In  FIG. 3 , the two printed boards  201   a  and  202   a  are set to the same size. However, for example, the printed board  201   a  on which the first power transmission antenna  201  is formed may be formed at a size smaller than the printed board  202   a . Furthermore, in the example of  FIG. 3 , the first power transmission antenna  201  is arranged above the second power transmission antenna  202 . Conversely, the second power transmission antenna  202  may be arranged above the first power transmission antenna  201 . In addition, as a configuration in which a multilayered conductor is arranged on one printed board, both the first power transmission antenna  201  and the second power transmission antenna  202  may be arranged on one printed board. 
       FIG. 4  is an illustration of the arrangement of the first power transmission antenna  201  and the second power transmission antenna  202  when viewed from the top surface of the charging device  200 .  FIG. 4  illustrates an antenna arrangement inside the device, and in practice, the power transmission antennas  201  and  202  cannot be seen from the surface of the charging device  200 . 
     As shown in  FIG. 4 , the first power transmission antenna  201  is arranged in the inner portion of the center of the planar part  211  of the charging device  200 , and the second power transmission antenna  202  is arranged in the surroundings of the first power transmission antenna  201 . The conductors forming the power transmission antennas  201  and  202  are connected to a circuit substrate (not shown) arranged in the circuit arrangement unit  212  adjacent to the planar part  211 . 
       FIG. 5  is an illustration of the arrangement of the power transmission antennas  201  and  202 , shown in  FIG. 4 , when viewed from the side surface of the charging device  200 . 
     As shown in  FIG. 5 , the printed board  201   a  on which the first power transmission antenna  201  is formed, and the printed board  202   a  on which the second power transmission antenna  202  is formed, are arranged in such a manner as to overlap one another inside the charging device  200 . 
     1.4 Example of Configuration of Terminal Device 
       FIG. 6  illustrates the internal configuration of a terminal device of the present embodiment. The terminal device  100  of the present embodiment is a mobile phone terminal device that performs wireless telephone communication, which is formed at a small size so as to be carried. 
     Referring to  FIG. 6 , the configuration of the terminal device  100  (see  FIG. 1 ) will be described. A communication processing unit  102  to which an antenna  101  for wireless telephone communication is connected is a processing unit that performs wireless communication with a base station for wireless telephones under the control of the control unit  110 . 
     At the time of a voice call, voice data contained in the data received by the communication processing unit  102  is supplied to an audio processing unit  103 . Then, a process for decoding the voice data is performed in the audio processing unit  103 , and an analog voice signal is obtained. The voice signal obtained by the audio processing unit  103  is supplied to a speaker  104 , whereby an output is made. 
     Furthermore, the audio signal that is picked up and obtained by a microphone  105  is supplied to the audio processing unit  103 , whereby the audio signal is coded to predetermined voice data by the audio processing unit  103 . Then, the obtained voice data is supplied to the communication processing unit  102 , whereby the voice data is wirelessly transmitted. 
     The processing units, such as the communication processing unit  102  and the audio processing unit  103 , perform transmission and reception of control data with the control unit  110  through a control line  121 , and also perform data transmission of voice data through a data line  122 . Data transmission other than this is also performed among the units inside the terminal device  100  through the control line  121  and the data line  122 . 
     Operation data from the operation unit  106  made up of keys, a touch panel, and the like, the operation unit  106  being operated by a user, is supplied to the control unit  120 , and a process indicated by the operation data is performed by the control unit  110 . 
     Furthermore, the terminal device  100  includes a display unit  107  made up of an image display panel, a driving circuit thereof, and the like. The display on this display unit  107  is controlled by the control unit  110 . Examples of displays on the display unit  107  include, in addition to a display necessary for a wireless telephone terminal device at the time of call origination and call reception, a display of electronic mail text for performing reception and transmission, a display of images obtained as a result of the connection to the Internet, and furthermore, a display as a consequence of execution of various functions provided in the terminal device  100 . 
     A memory  108  is connected to the control unit  110  through the control line  121  and the data line  122 , with various data necessary for a communication terminal device  100  being stored in the memory  108 . Furthermore, a program for performing an authentication process, which will be described later, or the like is also stored in the memory  108  when non-contact power transmission starts. 
     Furthermore, the terminal device  100  includes a data communication processing unit  151  that performs short-distance wireless communication, and a data communication antenna  150  is connected to the data communication processing unit  151 . The data communication processing unit  151  is a processing unit that performs wireless communication with the other party nearby. For short-distance wireless communication, for example, a short distance (near field) wireless method called an NFC method, a wireless LAN (Local Area Network) method, a Bluetooth (trademark) method, an infrared transmission method, or the like can be applied. 
     In the present embodiment, when the terminal device  100  performs power reception from the charging device  200 , the short-distance wireless communication unit  151  of the terminal device  100  performs wireless communication with the charging device  200 . 
     Furthermore, the terminal device  100  includes a processing unit for performing power reception in non-contact power transmission in a magnetic-field resonance method. That is, the terminal device  100 , which includes a power receiving antenna  130  that is a coil antenna, rectifies the electrical power received by the power receiving antenna  130  by using a rectifying circuit  132  after the electrical power passes through a matching circuit  131 , and thereafter supplies the electrical power to a charging unit  140 . The power receiving antenna  130  is arranged inside the rear surface of the configuration forming the terminal device  100 . The power receiving antenna  130  is formed so as to be nearly the same size as the first power transmission antenna  201  of the charging device  200 . By using the electrical power obtained from the rectifying circuit  132 , the charging unit  140  performs a process for charging a main battery  141  that is a secondary battery. 
     The power reception using the power receiving antenna  130  and the charging of the main battery  141  are performed under the control of a power-supply control unit  133 . 
     When the control of the power reception is to be performed by the power-supply control unit  133 , the power-supply control unit  133  judges the amount of received electrical power and the like, and transmits information, such as the judged amount of received electrical power, to the charging device  200  side through wireless communication using the data communication processing unit  151 . 
     1.5 Transmission Efficiency at the Time of Power Transmission 
     As a result of mounting the terminal device  100  on the planar part  211  of the charging device  200  as shown in  FIG. 1 , the electrical power transmitted from the first power transmission antenna  201  of the charging device  200  or from the second power transmission antenna  202  thereof is received by the power receiving antenna  130  of the terminal device  100 , and non-contact power transmission is performed. When the state in which the power transmission antenna and the power receiving antenna are arranged is changed at the time of this non-contact power transmission, the transmission efficiency is also greatly changed. 
       FIG. 7  illustrates inter-antenna efficiency at the time of non-contact power transmission. The transmission efficiency at the time of non-contact power transmission is determined on the basis of primary side circuit efficiency (circuit efficiency on the power transmission side), the inter-antenna efficiency, and secondary side circuit efficiency (circuit efficiency on the power reception side). 
     The inter-antenna efficiency is determined on the basis of the product of the coupling coefficient k of the antenna and the Q value of the resonance coil forming the antenna. 
     The coupling coefficient k is a ratio of a magnetic flux φ 1  that is generated by the coil forming the power transmission antenna to a magnetic flux φ 2  that links the coil forming the power receiving antenna, and is represented by the following expression.
 
coupling coefficient  k=φ 2/φ1
 
where k is a value greater than 0 and less than 1.
 
     As can be seen from the expression of the above-mentioned coupling coefficient, the state in which the coupling coefficient is high is a case in which the shape of the power transmission antenna is the same as that of the power receiving antenna, and both the antennas have been aligned. The coupling coefficient is changed on the basis of the positional relationship between the power transmission antenna and the power receiving antenna. On the other hand, in a case where power transmission is to be performed from one charging device to a plurality of terminal devices at the same time, it is preferable that the power transmission antenna has a size at which a plurality of terminal devices can be mounted. However, even if the power transmission antenna is made large, since the coupling coefficient is resultingly decreased, the efficiency of non-contact power transmission is decreased to less than in the case where power transmission is performed to only one terminal device. 
     1.6 Flow of Power Transmission Process 
     Next, a description will be given, with reference to the flowchart of  FIG. 8 , of an example of a processing procedure in which non-contact power transmission is performed from the charging device  200  to the terminal device  100  so as to charge the main battery  141  inside the terminal device  100 . The process of this flowchart of  FIG. 8  is performed under the control of the control unit  207  of the charging device  200 . 
     First, the control unit  207  of the charging device  200  intermittently transmits a terminal device detection signal from a data communication antenna  150  by using a data communication processing unit  209  (step S 11 ). Then, the control unit  207  judges whether or not a response signal for the intermittently transmitted terminal device detection signal is detected (step S 12 ), and waits until a response signal is detected. 
     When it is determined in step S 12  that a response signal is detected, a process for authenticating a terminal identification number (ID) for non-contact charging is performed with the terminal device  100  from which the response signal has been transmitted (step S 13 ). This authentication process is also performed through wireless communication using the data communication processing unit  209 . During this authentication process, the remaining charging level of the main battery  141  on the terminal device  100  side may be obtained by the charging device  200 , and it may be determined whether or not charging to the terminal device  100  is necessary. 
     After that, on the basis of the result of the authentication process in step S 13 , the control unit  207  determines whether the authentication process has been completed (that is, non-contact charging is possible) or the authentication process has failed (that is, non-contact charging is not possible) (step S 14 ). 
     When it is determined in step S 14  that the authentication process has been completed and the terminal device  100  capable of being charged without contact has come nearby, the control unit  207  determines whether or not the number of terminal devices  100  in which the authentication process has been performed is one (step S 15 ). When it is determined in step S 15  that the number of terminal devices  100  is not one (that is, plural), the second power transmission antenna  202  is selected as a power transmission antenna by the switch  205 , and electrical power transmission is started (step S 21 ). 
     When it is determined in step S 15  that the number of terminal devices  100  is one, the control unit  207  causes the switch  205  to select the second power transmission antenna  202  as a power transmission antenna, and performs electrical power transmission for a short time period. While the electrical power transmission is being performed, the received electrical power is measured by a power-supply control unit  133  of the terminal device  100 , and the data of the measured received electrical power value is transmitted to the charging device  200  in the data transmission process using the data communication processing unit  151 . In the charging device  200 , a process for receiving the data of the received electrical power value transmitted by the data communication processing unit  209  is performed, and the transmission efficiency is detected on the basis of the ratio of the transmitted electrical power value to the actually received electrical power value (step S 16 ). The transmission efficiency that is detected in this step S 16  will be referred to as transmission efficiency A. 
     After that, the control unit  207  causes the switch  205  to select the first antenna  201  as a power transmission antenna, and performs electrical power transmission for a short time period. Then, while the electrical power transmission is being performed, the received electrical power is measured by the power-supply control unit  133  of the terminal device  100 , and the data of the measured received electrical power value is transmitted to the charging device  200  in the data transmission process using the data communication processing unit  151 . In the charging device  200 , a process for receiving the data of the received electrical power value transmitted by the data communication processing unit  209  is performed, and the transmission efficiency is detected on the basis of the ratio of the transmission electrical power value to the actually received electrical power value (step S 17 ). The transmission efficiency that is detected in this step S 17  will be referred to as transmission efficiency B. 
     When the transmission efficiencies A and B are obtained, in the control unit  207 , the transmission efficiency A is compared with the transmission efficiency B (step S 18 ). When the transmission efficiency A is determined to be higher at the comparison in step S 18 , the control unit  207  causes the switch  205  to select the second power transmission antenna  202 , and starts electrical power transmission for battery charging (step S 19 ). The case in which the transmission efficiency A is higher than the transmission efficiency B corresponds to a state in which the position of the first power transmission antenna  201  does not match the position of the power receiving antenna  130 . 
     When it is determined in the comparison of step S 18  that the transmission efficiency B is higher, the control unit  207  selects the first power transmission antenna  201  by using the switch  205 , and starts electrical power transmission for battery charging (step S 20 ). The case in which the transmission efficiency B is higher than the transmission efficiency A corresponds to a state in which the position of the first power transmission antenna  201  almost matches the position of the power receiving antenna  130 . 
     When the electrical power transmission in steps S 19 , S 20 , and S 21  starts, the control unit  207  of the charging device  200  monitors the increase/decrease in the number of terminal devices  100  (step S 22 ). The monitoring of this increase/decrease is performed, for example, in such a way that the intermittent transmission of a terminal device detection signal is performed in the same manner as at the time of the process in step S 11  so as to monitor the presence or absence of a response from a new terminal device and also to monitor whether or not the response from the terminal device  100  in which the electrical power transmission is being performed is continued. 
     Then, on the basis of the monitoring result in step S 22 , it is determined whether or not all the terminal devices  100  have separated from the charging device  200  (step S 23 ). When it is determined in step S 23  that all the terminal devices  100  have separated from the charging device  200 , the control unit  207  stops the power transmission from the charging device  200  (step S 24 ). Then, after the power transmission is stopped, the control unit  207  returns to the determination process in step S 11 . 
     Also, when it is determined in step S 23  that the terminal device  100  exists in the vicinity of the charging device  200 , the control unit  207  determines whether or not the number of terminal devices  100  has increased/decreased (step S 25 ). When it is determined in step S 25  that there is an increase/decrease in the number of terminal devices, the process returns to the determination process of step S 15 . 
     When it is determined in step S 25  that there is no increase/decrease, the control unit  207  checks whether the charging to the main battery  141  inside the terminal device  100  is to be continued (step S 26 ), and determines whether or not the charging for all the terminal device  100   s  has been completed (step S 27 ). When it is determined in step S 27  that the charging for all the terminal devices  100  has not been completed (that is, there is a terminal device in which charging is being continued), the process returns to the determination process of this. 
     When it is determined in step S 27  that the charging for all the terminal devices  100  has been completed, the control unit  207  stops the power transmission (step S 28 ), and detects the remaining level of the main battery  141  inside the terminal device  100  (step S 29 ). After the detection in step S 29  is performed, it is determined whether or not the detected remaining level of the battery has decreased to the remaining level of the battery at which recharging is started (step S 30 ). When it is determined in step S 30  that there is no terminal device  100  whose remaining level of the battery has reached the remaining level of the battery at which the recharging is started, the process returns to the determination of step S 29 . 
     When it is determined in step S 30  that even one terminal device  100  that has reached the remaining level of the battery at which recharging is started is detected, the process returns to the determination process of step S 15 . 
     Furthermore, when it is determined in step S 14  that an authentication process with a nearby terminal device has failed, error handling in which power transmission to the corresponding terminal device is not performed is performed (step S 31 ). In addition, a process for detecting whether or not the terminal device in which the error handling has been performed continues to exist nearby is performed (step S 32 ). Then, on the basis of the detection process in step S 32 , it is determined whether or not the corresponding terminal device has separated from the charging device  200  (step S 33 ). When the terminal device has not separated from the charging device  200 , the existence detection of step S 32  is continued. When it is determined in step S 33  that the corresponding terminal device has separated from the charging device  200 , the process returns to the process of step S 11 . 
     With such a processing procedure, non-contact transmission is performed from the charging device  200  to the terminal device  100 , and the main battery  141  inside the terminal device  100  is charged. Consequently, it is possible to satisfactorily perform non-contact power transmission from the charging device  200  to the terminal device  100 . That is, for example, as shown in  FIG. 1 , in a case where the terminal device  100  is mounted in nearly the center of the planar part  211  of the charging device  200 , the power receiving antenna  130  on the terminal device  100  side almost matches the position of the first power transmission antenna  201 , and comparatively high transmission efficiency is obtained. In the case of the arranged state shown in  FIG. 1 , at the time of determination in step S 18  of the flowchart of  FIG. 8 , it is determined that the efficiency B is higher, and the first power transmission antenna  201  is used for power transmission. 
     1.7 Example of Arrangement of Terminal Device 
     Next, examples of states in which terminal devices are arranged, which differ from the state in which the terminal device of  FIG. 1  is arranged, will be described with reference to  FIGS. 9 to 11 . 
     An example of the arrangement shown in  FIG. 9  is a case in which one terminal device  100  is arranged offset greatly from the center at which the first power transmission antenna  201  is arranged. 
     In the case of this example of  FIG. 9 , the power receiving antenna  130  of the terminal device  100  comes into proximity to the conductor forming the second power transmission antenna  202 , and the case in which the second power transmission antenna  202  is used causes the transmission efficiency to become higher. Therefore, in the case of this example of  FIG. 9 , it is determined in step S 18  of the flowchart of  FIG. 8  that the efficiency A is higher, and the second power transmission antenna  202  is used for power transmission. 
     In the case of this example of  FIG. 9 , the transmission efficiency becomes poorer than in the example of  FIG. 1 . However, since the large power transmission antenna  202  is used to perform a power transmission process, non-contact power transmission is more satisfactory than in a case in which the small power transmission antenna  201  is used and electrical power transmission is performed. 
     The example of the arrangement shown in  FIG. 10  is an example of a case in which one terminal device  100  is arranged at a position that is slightly offset from the center at which the first power transmission antenna  201  is arranged. 
     The case of this example of  FIG. 10  is a state in which a portion of the first power transmission antenna  201  overlaps a portion of the power receiving antenna  130 , and there is a high probability that the first power transmission antenna  201  is used for power transmission. However, in the case of the arranged state of this example of  FIG. 10 , the transmission efficiency becomes slightly poorer than in the example of  FIG. 1 . 
     The example of the arrangement shown in  FIG. 11  is a case in which two terminal devices  100  are prepared, and are arranged side by side on the planar part  211  of the charging device  200 . 
     In this case, regardless of the positional relationship between the terminal devices  100 , the second power transmission antenna  202  that is a large antenna is used to perform power transmission, and electrical power transmission can be performed comparatively satisfactorily to two terminal devices  100 . As described above, in the case where two terminal devices  100  are mounted, “NO” is set in the determination process of step S 15  in the flowchart of  FIG. 8 . Consequently, the second power transmission antenna  202  is always used as indicated in step S 21 . For this reason, a certain level of transmission efficiency is obtained. 
     2. Second Embodiment 
     Next, a second embodiment of the present disclosure will be described with reference to  FIGS. 12 and 13 . 
     The second embodiment is such that the shape of the charging device and the arrangement of the power transmission antenna have been changed compared to the first embodiment. For the block configuration inside the charging device, the configuration shown in  FIG. 2  can be applied, and thus, the description thereof is omitted herein. 
     A charging device  300  shown in  FIGS. 12 and 13  will be described. The charging device  300  is configured in such a manner that a housing having a first planar part  311  and a housing having a second planar part  312  are rotatably joined using a hinge unit  303 . In the example of  FIGS. 12 and 13 , the first planar part  311  is arranged in such a manner as to be slightly inclined. 
     Then, a first power transmission antenna  301  is arranged in the inside of nearly the center of the first planar part  311 , and a second power transmission antenna  302  is arranged in the second planar part  312 . The first power transmission antenna  301  is an antenna of nearly the same size as the power receiving antenna  130  provided in the terminal device  100 , and the second power transmission antenna  302  is an antenna in a shape larger than that of the terminal device  100 . In the perspective view of  FIG. 12 , the antennas  301  and  302  are indicated using dashed lines, and in the side view of  FIG. 13 , the state in which the antennas  301  and  302  are arranged inside the housing is indicated using a solid line. 
     As shown in  FIG. 12 , one terminal device  100  can be mounted on the first planar part  311  side. Furthermore, one or more terminal devices  100  can be mounted on the second planar part  312  side. 
     Also, in the case of the configurations shown in  FIGS. 12 and 13 , for example, by using a process for selecting a power transmission antenna, which is indicated in the flowchart of  FIG. 8 , selection of an appropriate power transmission antenna can be made, and advantageous effects that are the same as those in the case of the first embodiment are obtained. 
     3. Third Embodiment 
     Next, a third embodiment of the present disclosure will be described with reference to  FIGS. 14 and 15 . 
     The third embodiment is such that the shape of the charging device and the arrangement of the power transmission antenna are changed when compared to the first embodiment. The block configuration inside the charging device is the same as the configuration shown in  FIG. 2 , and thus, the description thereof is omitted herein. 
     A charging device  400  shown in  FIGS. 14 and 15  will be described. The charging device  400  is configured in such a way that a first planar part  411  and a second planar part  412  are arranged with a step difference therebetween. In the examples of  FIGS. 14 and 15 , the first planar part  411  is arranged at a position slightly higher than that of the second planar part  412 . 
     Then, a first power transmission antenna  401  is arranged in the inside of nearly the center of the first planar part  411 , and a second power transmission antenna  402  is arranged in the second planar part  412 . The first power transmission antenna  401  is an antenna of nearly the same size as the power receiving antenna  130  provided in the terminal device  100 , and the second power transmission antenna  402  is an antenna in a shape larger than that of the terminal device  100 . In the perspective view of  FIG. 14 , the antennas  401  and  402  are indicated using dashed lines, and in the side view of  FIG. 15 , the position of the arrangement of each of the antennas  401  and  402  inside the housing is indicated using a solid line. 
     As shown in  FIG. 14 , one terminal device  100  can be mounted on the first planar part  411  side, and one or more terminal devices  100  can be mounted on the second planar part  312  side. 
     Also, in the configurations shown in  FIGS. 14 and 15 , for example, by using a process for selecting a power transmission antenna, which is shown in the flowchart of  FIG. 8 , it is possible to select an appropriate power transmission antenna, and advantageous effects that are same as those in the case of the first embodiment are obtained. 
     4. Fourth Embodiment 
     Next, a fourth embodiment of the present disclosure will be described with reference to  FIGS. 16 and 17 . The fourth embodiment is also such that the shape of the charging device and the arrangement of the power transmission antenna are changed when compared to the first embodiment. The block configuration inside the charging device is the same as the configuration shown in  FIG. 2 , and thus, the description thereof is omitted herein. 
     A charging device  500  shown in  FIGS. 16 and 17  will be described. The charging device  500  is configured in such a way that a pocket part  511  and a planar part  512  are arranged side by side. The pocket part  511  is configured in such a way that, for example, an openable/closable lid is provided, and one terminal device  100  can be housed in the inside. 
     Then, the first power transmission antenna  501  is arranged in the inside of nearly the center of the pocket part  511 , and the second power transmission antenna  502  is arranged in the planar part  512 . The first power transmission antenna  501  is an antenna of nearly the same size as the power receiving antenna  130  provided in the terminal device  100 , and the second power transmission antenna  502  is an antenna in a shape larger than that of the terminal device  100 . In the perspective view of  FIG. 16 , the antennas  501  and  502  are indicated using dashed lines, and in the side view of  FIG. 17 , the positions of the antennas  501  and  502  inside the housing are indicated using solid lines. 
     As shown in  FIG. 16 , one or more terminal devices  100  can be mounted on the planar part  512 . 
     Also, in the case of the configurations shown in  FIGS. 16 and 17 , for example, a process for selecting a power transmission antenna, which is shown in  FIG. 8 , is applied. Consequently, it is possible to select an appropriate power transmission antenna, and advantageous effects that are the same as those of the first embodiment are obtained. 
     5. Modifications 
     In each of the above-mentioned embodiments, no particular description has been given regarding the setting in a charging device when power transmission is performed from the first power transmission antenna that is a comparatively small antenna and when power transmission is performed from the second power transmission antenna that is a comparatively large antenna. The electrical powers to be transmitted when power transmission is performed from both the power transmission antennas may be set to be the same. For example, in a case where the second power transmission antenna is used to transmit electrical power, the electrical power to be transmitted may be set to be larger than that when the first power transmission antenna is used to transmit electrical power. 
     Furthermore, at the time of the determination process in step S 18  of the flowchart of  FIG. 8 , transmission efficiencies based on the two antennas are compared, and the higher of the transmission efficiencies is selected. Alternatively, the received electrical powers themselves may be compared, and the larger of the received electrical powers may be selected. 
     Furthermore, in the above-mentioned embodiments, as a power receiving device for receiving electrical power from the charging device, a mobile phone terminal device is used. Needless to say, other power receiving devices can be used when electrical power is supplied thereto in a non-contact manner. Examples of a usable apparatus for which electrical power supply is necessary for the purpose of charging include a music reproduction device, a video game device, a remote control device, and a personal computer device. 
     Furthermore, in the above-described embodiments, the power receiving device is used in non-contact power transmission employing a magnetic-field resonance method. However, the power receiving device can be used in non-contact power transmission based on another method as long as the method is a method of transmitting electrical power in a non-contact manner by using an antenna (coil). 
     Furthermore, the configurations and the processes described in the claims of the present disclosure are not limited to the above-described embodiments. It should be understood, of course, by those skilled in the art that various modifications, combinations, and other embodiments may be made according to the design or other elements insofar as they come within the scope of the claims, or the equivalence thereof.