Abstract:
A wireless power transmission device, a wireless power transmission control device, and a wireless power transmission method are provided. A coupling frequency between a source resonator and a target resonator is determined A transmission frequency is controlled such that power is transmitted from the source resonator to the target resonator at the coupling frequency. Therefore, it is possible to maintain a high power transmission efficiency without using an additional matching circuit even when a distance between the source resonator and the target resonator is changed.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
       [0001]    This application claims the benefit under 35 U.S.C. §119(a) of Korean Patent Application No. 10-2009-0098779, filed on Oct. 16, 2009, in the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference for all purposes. 
       BACKGROUND 
       [0002]    1. Field 
         [0003]    The following description relates to a wireless power transmission technology, and more particularly, the following description relates to a wireless power transmission technology that generates a high power transmission efficiency even when a distance between resonators changes. 
         [0004]    2. Description of Related Art 
         [0005]    Recently, a variety of portable electronic products have been released as the development of information technologies (IT) has increased. Battery performance of the portable electronic products is emerging as an important issue. Portable electronic products as well as household appliances can function to wirelessly transmit data, however, conventionally they can only receive power through wired power lines. 
         [0006]    Wireless power transmission technologies for supplying power in a wireless manner have been studied in recent years. In a wireless environment, a distance between a source resonator and a target resonator is likely to vary as time passes. Accordingly, the requirements to match the source resonator with the target resonator may also change over time. Therefore, there is a demand for a method to improve wireless power transmission efficiency and a wireless power transmission method that may adapt when the distance between the two resonators and/or the matching requirements change. 
       SUMMARY 
       [0007]    In one general aspect, there is provided a wireless power transmission device, comprising a determiner to determine a coupling frequency between a source resonator and a target resonator, and a controller to control a transmission frequency such that power is transmitted from the source resonator to the target resonator at the determined coupling frequency. 
         [0008]    The coupling frequency may be an odd mode frequency. 
         [0009]    The determiner may measure a reflected wave received from the target resonator that is in response to a transmission signal transmitted from the source resonator to the target resonator, and determine the coupling frequency to be a frequency where the reflected wave has a minimum amplitude. 
         [0010]    The determiner may measure a reflected wave received from the target resonator that is in response to a transmission signal transmitted from the source resonator to the target resonator, and determine the coupling frequency to be a frequency where a phase of the reflected wave is identical to a phase of the transmission signal. 
         [0011]    The determiner may measure a reflected wave received from the target resonator that is in response to a transmission signal transmitted from the source resonator to the target resonator, and determine the coupling frequency to be a frequency where the reflected wave has a minimum power. 
         [0012]    The determiner may comprise a power detector that detects the power of the reflected wave. 
         [0013]    The determiner may scan a band of frequencies lower than a center frequency of the transmission signal, and measure the reflected wave generated by the scanned band of frequencies. 
         [0014]    The wireless power transmission device may further comprise a distance measuring unit to measure a distance between the source resonator and the target resonator, wherein, when the distance between the source resonator and the target resonator decreases, the determiner may scan a band of frequencies lower than the transmission frequency and measures the reflected wave, and when the distance between the source resonator and the target resonator increases, the determiner may scan a band of frequencies higher than the transmission frequency and measures the reflected wave. 
         [0015]    The determiner may comprise a directional coupler to measure the reflected wave. 
         [0016]    The controller may comprise a phase locked loop (PLL) circuit to control the transmission frequency. 
         [0017]    In another aspect, there is provided a wireless power transmission method, comprising determining a coupling frequency between a source resonator and a target resonator, and controlling a transmission frequency such that power is transmitted from the source resonator to the target resonator at the determined coupling frequency. 
         [0018]    In another aspect, there is provided a wireless power transmission device, comprising an input unit to receive an input of a coupling frequency between a source resonator and a target resonator, and a controller to control a transmission frequency such that power is transmitted from the source resonator to the target resonator at the input coupling frequency. 
         [0019]    In another aspect, there is provided a wireless power transmission method, comprising receiving an input of a coupling frequency between a source resonator and a target resonator, and controlling a transmission frequency such that power is transmitted from the source resonator to the target resonator at the input coupling frequency. 
         [0020]    In another aspect, there is provided a wireless power transmission control device, comprising a determiner to determine a coupling frequency between a source resonator and a target resonator, and an output unit to transmit the coupling frequency to a wireless power transmission device. 
         [0021]    The coupling frequency may be an odd mode frequency. 
         [0022]    When an amount of a power transmitted by the wireless power transmission device is less than a predetermined value, the determiner may determine the coupling frequency. 
         [0023]    The wireless power transmission control device may further comprise an input unit to receive an input of the predetermined value. 
         [0024]    Other features and aspects may be apparent from the following description, the drawings, and the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]      FIG. 1  is a diagram illustrating an example in which a wireless power transmission device wirelessly transmits power to one or more terminals. 
           [0026]      FIG. 2  is a diagram illustrating an example of a wireless power transmission device. 
           [0027]      FIG. 3  is a diagram illustrating an example of a transmission signal and a reflected wave which are transmitted between a source resonator and a target resonator, respectively. 
           [0028]      FIG. 4  includes graphs illustrating examples of a change in a coupling frequency between a source resonator and a target resonator based on a distance between the source resonator and the target resonator. 
           [0029]      FIG. 5  is a flowchart illustrating an example of a wireless power transmission method. 
           [0030]      FIG. 6  is a diagram illustrating another example of a wireless power transmission device. 
           [0031]      FIG. 7  is a diagram illustrating an example of a wireless power transmission control device. 
       
    
    
       [0032]    Throughout the drawings and the description, unless otherwise described, the same drawing reference numerals should be understood to refer to the same elements, features, and structures. The relative size and depiction of these elements may be exaggerated for clarity, illustration, and convenience. 
       DESCRIPTION 
       [0033]    The following description is provided to assist the reader in gaining a comprehensive understanding of the methods, apparatuses, and/or systems described herein. Accordingly, various changes, modifications, and equivalents of the methods, apparatuses, and/or systems described herein may be suggested to those of ordinary skill in the art. Also, descriptions of well-known functions and constructions may be omitted for increased clarity and conciseness. 
         [0034]      FIG. 1  illustrates an example in which a wireless power transmission device wirelessly transmits a power to one or more terminals. 
         [0035]    Referring to  FIG. 1 , the wireless power transmission device  110  includes a source resonator  111 , and the terminal  120  includes a target resonator  121 . For example, the wireless power transmission device  110  may be installed as a module into a portable terminal. As described herein, the target resonator  121  may also act as a wireless transmission device, and vice versa. The target resonator may include, for example, a mobile terminal, a laptop computer, a personal digital assistant, and the like. The source resonator may include, for example, a resonator, a mobile terminal, a laptop computer, a personal digital assistant, and the like. 
         [0036]      FIG. 2  illustrates an example of a wireless power transmission device. 
         [0037]    Referring to  FIG. 2 , wireless power transmission device  200  includes a determiner  210 , a controller  220 , and a distance measuring unit  230 . 
         [0038]    The determiner  210  may determine a coupling frequency between a source resonator and a target resonator. For example, the coupling frequency may be an odd mode frequency which is further described with reference to  FIGS. 3 and 4 . 
         [0039]    The controller  220  may control a transmission frequency so that power may be transmitted at a coupling frequency. For example, the controller  220  may include a phase locked loop (PLL) circuit, and the controller  220  may control the transmission frequency using the PLL circuit. 
         [0040]    The wireless power transmission device may further include a distance measuring unit  230  to measure a distance between a source resonator and a target resonator, for example, the source resonator  110  and the target resonator  120 , as shown in  FIG. 1 . For example, when the distance between the source resonator and the target resonator decreases, the determiner  210  may scan a band of frequencies lower than the transmission frequency and may measure a wave reflected from the target resonator in response to the transmitted scanned frequency bands. As another example, when the distance between the source resonator and the target resonator increases, the determiner  210  may scan a band of frequencies higher than the transmission frequency and may measure the reflected wave in response to the transmitted scanned frequency bands. 
         [0041]    For example, the distance measuring unit may measure a distance between a source resonator and a target resonator using a distance sensor based on light, a distance sensor based on ultrasonic waves, and the like. 
         [0042]    In some embodiments, that is, the determiner  210  may determine a coupling frequency between a source resonator and a target resonator, based on the distance measured by the distance measuring unit  230 . The controller  220  controls the operation of the determiner  210  and the distance measuring unit  230 . 
         [0043]      FIG. 3  illustrates an example of a transmission signal and a reflected wave which are transmitted between a source resonator and a target resonator, respectively. 
         [0044]    Referring to  FIG. 3 , a source resonator  310  may transmit a transmission signal  330  to a target resonator  320  to wirelessly transmit power. In this example, a portion of the transmission signal  330  may be reflected and returned. This reflected signal is referred to as a reflected wave  340 . 
         [0045]    A determiner of a wireless power transmission device (i.e. the source resonator) may measure the reflected wave  340  of the transmission signal  330 , and may determine the coupling frequency based on the measured reflected wave  340 . For example, the determiner may determine the coupling frequency to be a frequency at which the reflected wave  340  has a minimum amplitude. As another example, the determiner may measure the reflected wave  340 , and may determine the coupling frequency to be a frequency at which a phase of the reflected wave  340  is the same as a phase of the transmission signal  330 . As another example, the determiner may measure the reflected wave  340 , and may determine the coupling frequency to be a frequency at which the reflected wave  340  has a minimum power. The determiner may include a power detector, and may detect the power of the reflected wave  340  using the power detector. 
         [0046]    Referring to  FIG. 3 , when the determiner scans frequency bands, the determiner transmits frequency bands, and then receives a reflected band in response. Based on this reflected band, the determiner determines whether the reflected band is, for example, at a minimum amplification, the same phase as the transmission signal, at a minimum power, and the like. That is, the scanning actually refers to the determiner transmitting various frequency bands to adjust the reflective band to become, for example, at least one of a minimum amplification, the same phase as the transmission signal, a minimum power, and the like. It is through this scanning that the determiner may test a number of frequency bands to determine, for example, which frequency band achieves a desired reflected band. 
         [0047]    In some embodiments, the determiner may include a directional coupler, and the determiner may measure the reflected wave  340  using the directional coupler. 
         [0048]    The determiner may scan a band of frequencies lower than a center frequency of the transmission signal  330 , and may measure the reflected wave  340 . Because an odd mode frequency is lower than the center frequency of the transmission signal  330 , the determiner may scan the odd mode frequency and measure the reflected wave  340 , in order to determine the odd mode frequency as a coupling frequency. This operation is further described with reference to  FIG. 4 . 
         [0049]    The wireless power transmission device may include a distance measuring unit  230  (shown in  FIG. 2 ) to measure a distance between the source resonator  310  and the target resonator  320 . For example, when the distance between the source resonator  310  and the target resonator  320  decreases, the determiner may scan a band of frequencies lower than the transmission frequency and may measure the reflected wave  340 . As another example, when the distance between the source resonator  310  and the target resonator  320  increases, the determiner may scan a band of frequencies higher than the transmission frequency and may measure the reflected wave  340 . This operation is further described with reference to  FIG. 4 . 
         [0050]      FIG. 4  includes graphs that illustrate examples of a change in a coupling frequency between a source resonator and a target resonator based on a distance between the source resonator and the target resonator. 
         [0051]    Referring to  FIG. 4 , the coupling frequency between the source resonator and the target resonator may be changed based on the distance between the source resonator and the target resonator. 
         [0052]    For example, the coupling frequency may be represented by the following Equation 1: 
         [0000]    
       
         
           
             
               
                 
                   
                     w 
                     = 
                     
                       
                         
                           
                             w 
                              
                             
                                 
                             
                              
                             1 
                           
                           + 
                           
                             w 
                              
                             
                                 
                             
                              
                             2 
                           
                         
                         2 
                       
                       ± 
                       
                         
                           
                             
                               ( 
                               
                                 
                                   
                                     w 
                                      
                                     
                                         
                                     
                                      
                                     1 
                                   
                                   - 
                                   
                                     w 
                                      
                                     
                                         
                                     
                                      
                                     2 
                                   
                                 
                                 2 
                               
                               ) 
                             
                             2 
                           
                           + 
                           
                             k 
                             2 
                           
                         
                       
                     
                   
                   , 
                 
               
               
                 
                   [ 
                   
                     Equation 
                      
                     
                         
                     
                      
                     1 
                   
                   ] 
                 
               
             
           
         
       
     
         [0000]    where w denotes a coupling frequency, w1 denotes a resonant frequency of a source resonator, w2 denotes a resonant frequency of a target resonator, and k denotes a coupling coefficient. When the source resonator is disposed at a distance relatively far from the target resonator, the coupling coefficient k may have a smaller value. When the source resonator is disposed relatively close to the target resonator, the coupling coefficient k may have a larger value. 
         [0053]    In graph  410  of  FIG. 4 , when the distance between the source resonator and the target resonator is far enough away, the coupling coefficient k may have a value of ‘0,’ and the source resonator and the target resonator may be set in advance such that they both have the same resonant frequency (namely, w1=w2). In other words, the coupling frequency w may have a single value of ‘f o ’ denoting a center frequency  411 . Before coupling the source resonator to the target resonator, both the source resonator and the target resonator may have the center frequency  411  as a resonant frequency. 
         [0054]    In graph  420  of  FIG. 4 , when the distance between the source resonator and the target resonator is shorter, the coupling coefficient k may have values other than ‘0,’ and the coupling frequency w may have a value of ‘f odd ’ denoting an odd mode frequency  421  and a value of ‘f even ’ denoting an even mode frequency  422 . In this example, the odd mode frequency  421  is shown to the left of the center frequency  411 , and is lower in value than the center frequency  411 . In this example, the even mode frequency  422  is shown to the right of the center frequency  411  and is higher in value than the center frequency  411 . For example, the determiner of the wireless power transmission device may scan a band of frequencies lower than the center frequency  411  of the transmission signal, and may measure the reflected wave of the transmission signal, to determine the . odd mode frequency  421  as a coupling frequency. 
         [0055]    Referring to Equation 1, when the source resonator is disposed close to the target resonator according to a change in a location of the terminal, a value of k may be increased and a value of the odd mode frequency  421  may be reduced, as compared with before the change in the location of the terminal. The wireless power transmission device may further include a distance measuring unit to measure the distance between the source resonator and the target resonator. When the distance between the source resonator and the target resonator is reduced, the determiner may scan a band of frequencies lower than the transmission frequency and may measure the reflected wave of the transmission signal, to determine the odd mode frequency  421  as a coupling frequency. 
         [0056]    Additionally, in Equation 1, when the source resonator is disposed relatively far away from the target resonator according to a change in a location of the terminal, a value of k may be reduced and a value of the odd mode frequency  421  may be increased, as compared to before the change in the location of the terminal. In some embodiments, the wireless power transmission device may include a distance measuring unit to measure the distance between the source resonator and the target resonator. When the distance between the source resonator and the target resonator is increased, the determiner may scan a band of frequencies higher than the transmission frequency and may measure the reflected wave of the transmission signal, to determine the odd mode frequency  421  as a coupling frequency. 
         [0057]    For example, the determiner of the wireless power transmission device may scan a band of frequencies lower than the center frequency  411  of the transmission signal, and may measure the reflected wave of the transmission signal. Referring to Equation 1, the odd mode frequency is lower than the center frequency  411  of the transmission signal, and the determiner may scan the odd mode frequency and may measure the reflected wave of the transmission signal, to determine the odd mode frequency  421  as a coupling frequency. 
         [0058]      FIG. 5  illustrates an example of a wireless power transmission method. 
         [0059]    Referring to  FIG. 5 , a coupling frequency between a source resonator and a target resonator is determined in  510 . 
         [0060]    For example, a reflected wave of a transmission signal may be measured, and the coupling frequency may be determined based on the reflected wave, for example, the coupling frequency may be a frequency where the reflected wave has a minimum amplitude. As another example, the reflected wave may be measured, and the coupling frequency may be determined to be a frequency where a phase of the reflected wave is the same as a phase of the transmission signal. As another example, the reflected wave may be measured, and the coupling frequency may be determined to be a frequency where the reflected wave has a minimum power. 
         [0061]    As an example, a directional coupler may be used to measure the reflected wave. 
         [0062]    In some embodiments, a band of frequencies lower than a center frequency of the transmission signal may be scanned, and the reflected wave may be measured. 
         [0063]    The wireless power transmission method may include measuring a distance between the source resonator and the target resonator. For example, when the distance between the source resonator and the target resonator decreases, a band of frequencies lower than a transmission frequency may be scanned and the reflected wave may be measured. When the distance between the source resonator and the target resonator increases, a band of frequencies higher than the transmission frequency may be scanned and the reflected wave may be measured. Accordingly, the transmission frequency may be adjusted in real time as the distance between the target resonator and the source resonator changes in real time. 
         [0064]    Whether the coupling frequency is the same as the transmission frequency is determined in  520 . 
         [0065]    In this example, the transmission frequency is controlled such that power is transmitted at the coupling frequency in  530 . In this example, the transmission frequency may be controlled to be equal to the coupling frequency. In some embodiments, a PLL circuit may be used to control the transmission frequency. 
         [0066]    As another example, the wireless power transmission method may include determining an odd mode frequency as the coupling frequency between the source resonator and the target resonator, and controlling the transmission frequency such that the odd mode frequency is the same as the transmission frequency when the odd mode frequency is determined to differ from the transmission frequency. 
         [0067]      FIG. 6  illustrates another example of a wireless power transmission device.  FIG. 7  illustrates an example of a wireless power transmission control device. 
         [0068]    Referring to  FIG. 6 , a wireless power transmission device  600  includes an input unit  610  and a controller  620 . In some embodiments, the wireless power transmission device may also include a distance measuring unit (not shown). 
         [0069]    The input unit  610  may receive an input of a coupling frequency between a source resonator and a target resonator. 
         [0070]    For example, the input unit  610  may receive a coupling frequency from a terminal including the target resonator. The terminal may wirelessly receive power from the wireless power transmission device  600 . For example, the terminal may include a wireless power transmission control device enabling measurement of the coupling frequency, as shown in  FIG. 7 . 
         [0071]    Referring to  FIG. 7 , wireless power transmission control device  700  includes a determiner  710  and an output unit  720 . In some embodiments, the wireless power transmission control device may also include a distance measuring unit (not shown). 
         [0072]    The determiner  710  may determine a coupling frequency between a source resonator and a target resonator. As described above, for example, the coupling frequency may be an odd mode frequency. For example, when an amount of power transmitted by the wireless power transmission device is less than a predetermined value, the determiner  710  may determine the coupling frequency. The operation of the determiner  710  is described above, thus, further description thereof is omitted herein. 
         [0073]    The output unit  720  may transmit the coupling frequency to a wireless power transmission device. The wireless power transmission device may control a transmission frequency such that power may be transmitted at the coupling frequency received from the output unit  720 . 
         [0074]    Additionally, the input unit  610  may receive a coupling frequency from an external device enabling determination of a coupling frequency between a source resonator and a target resonator. For example, the external device may include a wireless power transmission control device as described above with reference to  FIG. 7 . 
         [0075]    The controller  620  may control the transmission frequency such that power may be transmitted at a coupling frequency. For example, the controller  620  may include a PLL circuit, and control the transmission frequency using the PLL circuit. 
         [0076]    For example, the wireless power transmission device  600  may be included in a terminal, and may wirelessly transmit a power to other terminals. The wireless power transmission control device  700  may be included in a terminal. 
         [0077]    The processes, functions, methods, and/or software described above may be recorded, stored, or fixed in one or more computer-readable storage media that includes program instructions to be implemented by a computer to cause a processor to execute or perform the program instructions. The media may also include, alone or in combination with the program instructions, data files, data structures, and the Examples of computer-readable storage media include magnetic media, such as hard disks, floppy disks, and magnetic tape; optical media such as CD ROM disks and DVDs; magneto-optical media, such as optical disks; and hardware devices that are specially configured to store and perform program instructions, such as read-only memory (ROM), random access memory (RAM), flash memory, and the like. Examples of program instructions include machine code, such as produced by a compiler, and files containing higher level code that may be executed by the computer using an interpreter. The described hardware devices may be configured to act as one or more software modules in order to perform the operations and methods described above, or vice versa. In addition, a computer-readable storage medium may be distributed among computer systems connected through a network and computer-readable codes or program instructions may be stored and executed in a decentralized manner. 
         [0078]    As a non-exhaustive illustration only, the terminal device described herein may refer to mobile devices such as a cellular phone, a personal digital assistant (PDA), a digital camera, a portable game console, an MP3 player, a portable/personal multimedia player (PMP), a handheld e-book, a portable lab-top personal computer (PC), a global positioning system (GPS) navigation, and devices such as a desktop PC, a high definition television (HDTV), an optical disc player, a setup box, and the like, capable of wireless communication or network communication consistent with that disclosed herein. 
         [0079]    A computing system or a computer may include a microprocessor that is electrically connected with a bus, a user interface, and a memory controller. It may further include a flash memory device. The flash memory device may store N-bit data via the memory controller. The N-bit data is processed or will be processed by the microprocessor and N may be 1 or an integer greater than 1. Where the computing system or computer is a mobile apparatus, a battery may be additionally provided to supply operation voltage of the computing system or computer. 
         [0080]    It should be apparent to those of ordinary skill in the art that the computing system or computer may further include an application chipset, a camera image processor (CIS), a mobile Dynamic Random Access Memory (DRAM), and the like. The memory controller and the flash memory device may constitute a solid state drive/disk (SSD) that uses a non-volatile memory to store data. 
         [0081]    A number of examples have been described above. Nevertheless, it should be understood that various modifications may be made. For example, suitable results may be achieved if the described techniques are performed in a different order and/or if components in a described system, architecture, device, or circuit are combined in a different manner and/or replaced or supplemented by other components or their equivalents. Accordingly, other implementations are within the scope of the following claims.