Abstract:
This handheld-terminal charging device has a plurality of charging coils, a plurality of detection coils, and a control unit that is electrically connected to said charging coils and detection coils. The control unit drives the plurality of detection coils and watches for impedance changes that said detection coils detect when thus driven. If a detection coil detects an impedance change, a charging coil corresponding to said detection coil is selected from among the plurality of charging coils and a magnetic field is outputted from the selected charging coil. If a response signal that has been agreed upon with a handheld terminal is received in response to said magnetic field, the selected charging coil is used to charge said handheld terminal.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a handheld-terminal charging device which charges a handheld-terminal such as a cellular phone, and a vehicle in which the handheld-terminal charging device is mounted. 
       BACKGROUND ART 
       [0002]    Handheld-terminals such as cellular phones have very high functions and consume larger power accordingly. 
         [0003]    Hence, it is demanded that the handheld-terminals are charged everywhere including an inside of a vehicle. However, in recent years, handheld-terminal charging devices which enable so-called wireless charging without using cables tend to be gaining attention. 
         [0004]    That is, such a charging device includes a support plate whose front surface side is a handheld-terminal placement portion, and charging coils which are disposed at a back surface side of the support plate to face to the support plate. When a handheld-terminal is placed on the handheld-terminal placement portion, magnetic fluxes from the charging coils can charge the handheld-terminal (a similar device is disclosed in, for example, PTL 1). 
       CITATION LIST 
     Patent Literature 
       [0005]    PTL 1: Unexamined Japanese Patent Publication No. 2012-523814 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention provides a handheld-terminal charging device which reduces power loss and further suppresses a negative influence on other devices which use electromagnetic waves. 
         [0007]    A handheld-terminal charging device according to one aspect of the present invention includes a plurality of charging coils, a plurality of detecting coils, and a controller which is electrically connected to these charging coils and these detecting coils. The controller drives the plurality of detecting coils, and monitors a change in an impedance detected by the plurality of detecting coils when the plurality of detecting coils is driven. Further, the controller selects a charging coil associated with a detecting coil which has detected the change in the impedance, from the plurality of charging coils, and causes the selected charging coil to output a magnetic field. The controller charges the handheld-terminal by using the selected charging coil when the controller receives a response signal determined between the handheld-terminal charging device and the handheld-terminal in response to the magnetic field. 
         [0008]    Further, one aspect of the present invention is a vehicle in which the above handheld-terminal charging device is mounted. 
         [0009]    The handheld-terminal charging device according to the present invention can reduce a ping operation when detecting a position of a handheld-terminal and, consequently, can reduce power loss and suppress an influence on other devices which use electromagnetic waves. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0010]      FIG. 1  is a perspective view illustrating a state where a handheld-terminal charging device according to a first exemplary embodiment of the present invention is disposed inside a vehicle. 
           [0011]      FIG. 2  is a perspective view of the handheld-terminal charging device illustrated in  FIG. 1 . 
           [0012]      FIG. 3  is a perspective view illustrating a state where a handheld-terminal is placed on the mobile-terminal-charging device illustrated in  FIG. 2 . 
           [0013]      FIG. 4  is a perspective side view of the handheld-terminal charging device illustrated in  FIG. 2 . 
           [0014]      FIG. 5  is a view illustrating part of the handheld-terminal charging device illustrated in  FIG. 2 . 
           [0015]      FIG. 6  is a view illustrating another part of the handheld-terminal charging device illustrated in  FIG. 2 . 
           [0016]      FIG. 7  is a control block diagram of the handheld-terminal charging device illustrated in  FIG. 2 . 
           [0017]      FIG. 8  is an operation flowchart of the handheld-terminal charging device illustrated in  FIG. 2 . 
           [0018]      FIG. 9  is a view illustrating a structure and an operation example of the handheld-terminal charging device illustrated in  FIG. 2 . 
           [0019]      FIG. 10  is a view illustrating a structure and an operation example of a handheld-terminal charging device according to a second exemplary embodiment of the present invention. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0020]    Prior to description of exemplary embodiments of the present invention, a problem of a conventional handheld-terminal charging device (referred to as a charging device below) will be briefly described. A charging device described in PTL 1 adopts a multi-coil system. The multi-coil system uses only part of coils of a plurality of charging coils meeting positions at which the handheld-terminal is placed. 
         [0021]    More specifically, according to PTL 1, each charging coil outputs a magnetic field (Ping) in a short time in order to detect that a secondary device (charging target) is placed on the charging device and detect a position of the secondary device. When the secondary device is placed on a charging surface, information of the secondary device is transmitted from the secondary device to the charging device in response to the ping. Further, communication is established when the charging device receives this information, and charging starts on a full scale. In this case, a coil having a high reception strength of the information transmitted from the secondary device is selected from a plurality of charging coils of the charging device, and is used to perform charging. Hence, only the charging coil meeting the position at which the secondary device is placed is used for full-scale charging. 
         [0022]    However, according to this system, each charging coil repeats the ping at all times even when the secondary device is not placed on the charging device. Therefore, this system produces a magnetic field in air, and causes significant power loss. 
         [0023]    Further, when it is assumed that the charging device is mounted in a vehicle, the magnetic field repeatedly produced by the ping is concerned to negatively influence other in-vehicle devices which use electromagnetic waves. For example, the magnetic field interferes a frequency band of an in-vehicle radio and deteriorates sound. 
         [0024]    A handheld-terminal charging device according to the exemplary embodiments of the present invention, and a case where the handheld-terminal charging device is mounted in a vehicle will be described as an example with reference to the drawings. 
       First Exemplary Embodiment 
       [0025]      FIG. 1  is a perspective view illustrating a state where handheld-terminal charging device  5  according to the first exemplary embodiment of the present invention is disposed inside vehicle interior  2  of a vehicle,  FIG. 2  is a perspective view of handheld-terminal charging device  5 , and  FIG. 3  is a perspective view illustrating a state where handheld-terminal  23  is placed on handheld-terminal charging device  5 . 
         [0026]    In  FIG. 1 , handle  3  is installed at a front side of vehicle interior  2  of vehicle  1 . Further, electronic device  4  which plays music or video images or shows car navigation video images is installed at a side of handle  3 . Furthermore, handheld-terminal charging device  5  is installed at a rear side of electronic device  4  in vehicle interior  2 . 
         [0027]    As illustrated in  FIG. 2 , handheld-terminal charging device  5  includes box-shaped main body case  7  with support plate  6  disposed on an upper portion. As illustrated in  FIG. 3 , by placing handheld-terminal  23  on an upper surface (handheld-terminal placement portion) of support plate  6 , it is possible to wirelessly charge handheld-terminal  23 . 
         [0028]    Next, an inside of main body case  7  will be described in detail.  FIG. 4  is a side view illustrating a perspective view of main body case  7 . Inside main body case  7 , charging coil substrate  8  on which a plurality of charging coils is formed, and detecting coil substrate  9  on which a plurality of detecting coils is formed are mounted. Further, controller  10  electrically connected to the charging coils and the detecting coils are mounted inside main body case  7 . 
         [0029]      FIGS. 5 and 6  are views illustrating charging coil substrate  8  and detecting coil substrate  9  which are part of handheld-terminal charging device  5 . 
         [0030]    As illustrated in  FIG. 5 , a plurality of charging coils  11  are formed on charging coil substrate  8 . In the present exemplary embodiment, five charging coils Lc 1  to Lc 5  are provided. Each charging coil is formed by spirally winding a metal wire. 
         [0031]    As illustrated in  FIG. 6 , a plurality of detecting coils  12  are formed on detecting coil substrate  9 . A plurality of detecting coils  12  include five detecting coils L 1 , L 3 , L 5 , L 7 , L 9  of a first set formed on a lower surface of detecting coil substrate  9  (a surface facing a bottom plate of main body case  7 ), and four detecting coils L 2 , L 4 , L 6 , L 8  of a second set formed on an upper surface of detecting coil substrate  9  (a surface facing support plate  6 ). A plurality of detecting coils  12  are disposed to overlap when seen from a plan view such that ends of the detecting coils of the first set in an alignment direction and centers of the detecting coils of the second set in the alignment direction are collinearly positioned. In addition, in  FIG. 6 , the detecting coils of the first set are shifted from the detecting coils of the second set in a lower direction in  FIG. 6  for ease of description. Actually, when seen from a plan view, midpoints of long sides of the detecting coils of the first set and midpoints of long sides of the detecting coils of the second set are collinearly disposed. 
         [0032]      FIG. 7  is a control block diagram of handheld-terminal charging device  5 , and illustrates details of controller  10 . Controller  10  includes detecting coil driver  13  and charging coil driver  14 . Detecting coil driver  13  includes self-oscillation circuit  15 , detecting coil selection circuit  16  and impedance measurement circuit  17 . Impedance measurement circuit  17  monitors a change in an impedance of each of a plurality of detecting coils  12 . Detecting coil selection circuit  16  selectively connects each of a plurality of detecting coils  12 , and self-oscillation circuit  15  and impedance measurement circuit  17 . 
         [0033]    Meanwhile, charging coil driver  14  includes charging circuit  18  and charging coil selection circuit  19 . Charging coil selection circuit  19  selectively connects each of a plurality of charging coils  11  and charging circuit  18 . Charging circuit  18  converts direct-current power from an in-vehicle power supply (battery) into alternating-current power of an appropriate amplitude and frequency to supply to charging coils  11 . More specifically, charging circuit  18  includes DC-DC converter  20  and full-bridge inverter  21 . 
         [0034]    A threshold for determining changes in impedances of detecting coils  12  described below is stored in a memory (not illustrated) built in controller  10 . 
         [0035]    Next, an operation of the handheld-terminal charging device according to the present exemplary embodiment will be described with reference to  FIG. 8 . 
         [0036]    When power switch  22  illustrated in  FIG. 2  is pushed and the power supply is turned on, controller  10  detects whether or not handheld-terminal  23  has been placed on the upper surface (handheld-terminal placement portion) of support plate  6 , and detects a position at which handheld-terminal  23  has been placed (more precisely, a position of power receiving coil inside the handheld-terminal). More specifically, self-oscillation circuit  15  is turned on, and outputs pulse waves to a plurality of detecting coils  12  (S 1 ). In this case, impedance measurement circuit  17  sequentially measures an impedance of each of a plurality of detecting coils  12  (S 2 ). Further, impedance measurement circuit  17  monitors in which detecting coil of a plurality of detecting coils  12  the impedance has changed (S 3 ). In addition, a magnetic field transmitted from each detecting coil outputs a very small output voltage compared to a magnetic field output during a ping operation described below, and therefore has little influence on other in-vehicle devices which use electromagnetic waves. For example, an oscillation voltage of each detecting coil is 3.3 V, and an output voltage of the ping operation is 10 V or more. When the handheld-terminal is placed on the upper surface of support plate  6 , a value of an impedance measured by a detecting coil meeting a position of the power receiving coil increases compared to a case where handheld-terminal  23  is not placed on the upper surface. Hence, controller  10  can estimate the position at which handheld-terminal  23  has been placed according to in which detecting coil of a plurality of detecting coils  12  the impedance has changed. Controller  10  cannot actually determine at this point of time whether or not an object placed on the upper surface of support plate  6  is a chargeable handheld-terminal, and detects that some metal object has been placed and detects a position of this metal object. For a first time after communication with the object is established in S 7  described below, controller  10  determines that this object is the chargeable handheld-terminal, and starts a charging operation. When the communication is not established in S 7 , controller  10  determines that this object is not the handheld-terminal but a metal foreign object such as a coin, and does not start the charging operation. 
         [0037]    In S 3 , as an example of a method for monitoring a change in an impedance, impedance measurement circuit  17  measures a resonance frequency of each of detecting coils  12 , a resonance voltage or both of the resonance frequency and the resonance voltage to compare with the threshold stored in the memory. The threshold is set to a value of the resonance frequency or the resonance voltage at a normal level in a case where handheld-terminal  23  is not placed. When one or both of the resonance frequency and the resonance voltage change in one of a plurality of detecting coils  12 , a change in an impedance is detected. More specifically, a change in the resonance voltage reflects a resistance component (R component) of the change in the impedance, and the resonance frequency reflects a reactance component (L component) of the change in the impedance. When a metal object is placed on the upper surface of support plate  6 , the resonance frequency increases, and the resonance voltage lowers. 
         [0038]    In a case where the change in the impedance has been detected in S 3 , processing moves to S 4 . In a case where the change in the impedance has not been detected, the processing returns to S 2  again to measure impedances of detecting coils  12  again. 
         [0039]    In S 4  to S 7 , controller  10  checks whether or not the object placed on the upper surface of support plate  6  is a chargeable handheld-terminal. More specifically, controller  10  selects a charging coil associated with a detecting coil which has detected the change in the impedance, from a plurality of charging coils  11  (S 4 ), and causes the selected charging coil to output an magnetic field (S 6 ). In addition, before the charging coil outputs the magnetic field, self-oscillation circuit  15  is turned off once (S 5 ). 
         [0040]    Next, controller  10  checks whether or not a response signal determined between the handheld-terminal charging device and the handheld-terminal has been obtained in response to the output of the magnetic field from the selected charging coil (S 7 ). In a case where the predetermined response signal has been obtained in S 7 , controller  10  determines that communication with handheld-terminal  23  has been established, and starts charging operation on a full scale (S 8 ). In a case where the predetermined response signal has not been obtained in S 7 , controller  10  determines that the communication is not established, and the processing returns to S 1  again. 
         [0041]    In this case, an operation of outputting a magnetic field in a short time until whether or not there is a response from handheld-terminal  23  is determined is referred to as a ping operation. 
         [0042]    In this regard, an operation performed by handheld-terminal  23  in a period during which handheld-terminal charging device  5  performs the operation in S 4  to S 7  will be described. Handheld-terminal  23  returns the predetermined response signal to handheld-terminal charging device  5  in response to reception of the magnetic field output from the charging coil of handheld-terminal charging device  5 . In this case, handheld-terminal  23  fluctuates a value of a load connected with the power receiving coil. When a signal reception circuit connected to the charging coil of handheld-terminal charging device  5  detects a reflected impedance of this load fluctuation, the response signal is received. Such a signal transmitting and receiving method will be referred to as load modulation. The response signal returned from handheld-terminal  23  may be a simple signal only indicating that communication has been established, or may include ID information indicating such as a type of handheld-terminal  23 . 
         [0043]    The operation of handheld-terminal charging device  5  will be described again. During the charging operation (S 8 ), controller  10  monitors whether or not the communication with handheld-terminal  23  continues, and continues charging if the communication continues. When the communication is cut off, the processing returns to S 1  to check again whether or not there is the handheld-terminal. Further, during the charging operation (S 8 ), controller  10  monitors whether or not a signal indicating that charging is finished has been transmitted from handheld-terminal  23 , continues the charging in a case where the charging has not been finished, and stops the charging in a case where the charging has been finished (S 9 ). 
         [0044]    Next, how the charging coil to be selected in S 4  is determined based on a result of the change in the impedance detected in above S 3  will be described. 
         [0045]      FIG. 9  is a view for describing an example of a positional relationship between charging coils  11  and detecting coils  12  in handheld-terminal charging device  5 , and a change in an impedance detected by each detecting coil when power receiving coil  24  is placed on detecting coil  12 . In  FIG. 9 , detecting coil substrate  9  is shifted from charging coil substrate  8  in a lower direction in  FIG. 9  for ease of description. Further, similar to  FIG. 6 , detecting coils L 1 , L 3 , L 5 , L 7 , L 9  are shifted from detecting coils L 2 , L 4 , L 6 , L 8  in the lower direction in  FIG. 9 . Actually, when seen from a plan view, midpoints of long sides of the charging coils and midpoints of long sides of the detecting coils are collinearly disposed. 
         [0046]    In the present exemplary embodiment, some detecting coils  12  are disposed substantially right above charging coils  11 , and some detecting coils  12  are disposed across the two neighboring charging coils. 
         [0047]    In the present exemplary embodiment, the center of each detecting coil of detecting coils L 1 , L 3 , L 5 , L 7 , L 9  in the alignment direction, and the center of each charging coil in the alignment direction are substantially collinearly positioned. Hence, each of detecting coils L 1 , L 3 , L 5 , L 7 , L 9  is disposed substantially right above each of the associated charging coils. Meanwhile, the center of each detecting coil of detecting coils L 2 , L 4 , L 6 , L 8  in the alignment direction, and the end of each charging coil in the alignment direction overlap. Hence, detecting coils L 2 , L 4 , L 6 , L 8  are disposed across the two neighboring charging coils. 
         [0048]    In addition, in case of such a layout, a width of each detecting coil is preferably half or more of a width of each charging coil. When the width of each detecting coil is smaller than the half of the width of each charging coil, gaps are generated between the detecting coils. Further, a length of each detecting coil is preferably substantially the same as a length of each charging coil. According to this configuration, the detecting coils can uniformly cover a roughly entire area of the charging coils. In addition, in the above description, the “width” means the length of each coil in the alignment direction, and the “length” means the length in a direction vertical to the “width”. 
         [0049]    Impedance measurement circuit  17  determines which detecting coil of a plurality of detecting coils  12  has detected a maximum change in an impedance. In a case where one of above detecting coils L 1 , L 3 , L 5 , L 7 , L 9  has detected the maximum change in the impedance, controller  10  selects a charging coil right below the detecting coil which has detected the maximum change in the impedance as the associated charging coil. 
         [0050]    Meanwhile, in a case where one of detecting coils L 2 , L 4 , L 6 , L 8  has detected the maximum change in the impedance, controller  10  determines that power receiving coil  24  of handheld-terminal  23  has been placed across the two charging coils. Further, controller  10  refers to changes in impedances of both left and right neighboring detecting coils of the detecting coil (both sides of the detecting coil in the alignment direction) which has detected the maximum change in the impedance, too. Next, controller  10  compares the changes of levels in the impedances detected by these both left and right detecting coils. In an example in  FIG. 9 , detecting coil L 4  has detected the maximum change in the impedance, and therefore controller  10  refers to changes in impedances of left and right detecting coils L 3  and L 5 . In the example in  FIG. 9 , the change in the impedance detected by right detecting coil L 5  is larger. Based on this result, controller  10  determines that power receiving coil  24  of handheld-terminal  23  is displaced to a right side (close to detecting coil L 5 ) from the center of detecting coil L 4 , and selects charging coil Lc 3  on the right side (close to detecting coil L 5 ) from two charging coils Lc 2  and Lc 3  across which detecting coil L 4  is disposed. 
         [0051]    Thus, an optimal charging coil meeting a position of placed power receiving coil  24  is selected. 
       Second Exemplary Embodiment 
       [0052]      FIG. 10  is a view for describing an example of a positional relationship between charging coils  11  and detecting coils  12  in handheld-terminal charging device according to the second exemplary embodiment of the present invention, and a change in an impedance detected by each detecting coil when power receiving coil  24  is placed on detecting coil  12 . 
         [0053]    The present exemplary embodiment differs from the first exemplary embodiment in a number of detecting coils  12  and the positional relationship between charging coils  11  and detecting coils  12 . In the first exemplary embodiment, each of detecting coils to which an odd number is assigned, i.e., each detecting coil which is formed on a lower surface of detecting coil substrate  9  (a surface facing a bottom plate of main body case  7 ) is disposed right above each of charging coils  11  to configure the detecting coils of a first set. Meanwhile, each of detecting coils to which an even number is assigned, i.e., each detecting coil which is formed on an upper surface of detecting coil substrate  9  (a surface facing support plate  6 ) is disposed across two neighboring charging coils to configure the detecting coils of a second set. The present exemplary embodiment differs from the first exemplary embodiment in a layout of charging coils  11  and detecting coils  12 . The other configurations are the same as configurations in the first exemplary embodiment. 
         [0054]    In the present exemplary embodiment, a center of each detecting coil of detecting coils L 1 , L 3 , L 6 , L 8  in the alignment direction, and a center of each associated charging coil in the alignment direction are substantially collinearly positioned. That is, each of detecting coils L 1 , L 3 , L 6 , L 8  is disposed substantially right above each of the associated charging coils. These four detecting coils are detecting coils of the first set. Meanwhile, a center of each detecting coil of detecting coils L 2 , L 4 , L 5 , L 7  in the alignment direction overlaps with an end of each associated charging coil in the alignment direction. That is, detecting coils L 2 , L 4 , L 5 , L 7  are disposed across the two neighboring charging coils. These four detecting coils are detecting coils of the second set. In addition, there is no detecting coil positioned right above charging coil Lc 3 . 
         [0055]    An operation in the second exemplary embodiment is as follows. First, in a case where one of the detecting coils (L 1 , L 3 , L 6 , L 8 ) of the first set has detected a maximum change in an impedance, a charging coil right below the detecting coil which has detected the maximum change in the impedance is selected as the associated charging coil. 
         [0056]    Meanwhile, in a case where one of the detecting coils (L 2 , L 4 , L 5 , L 7 ) of the second set has detected the maximum change in the impedance, controller  10  determines that power receiving coil  24  of handheld-terminal  23  has been placed across the two charging coils. Further, controller  10  refers to changes in impedances of both left and right neighboring detecting coils of the detecting coil (both sides of the detecting coil in the alignment direction) which has detected the maximum change in the impedance, too. Next, controller  10  compares the changes in the impedances detected by these both left and right detecting coils. In an example in  FIG. 10 , detecting coil L 4  has detected the maximum change in the impedance, and therefore controller  10  refers to changes in impedances of left and right detecting coils L 3  and L 5 . In the example in  FIG. 10 , the change in the impedance detected by right detecting coil L 5  is larger. Based on this result, controller  10  determines that power receiving coil  24  of handheld-terminal  23  is displaced to a right side (close to detecting coil L 5 ) from the center of detecting coil L 4 , and selects charging coil Lc 3  on the right side (close to detecting coil L 5 ) from two charging coils Lc 2  and Lc 3  across which detecting coil L 4  is disposed. 
         [0057]    Thus, an optimal charging coil meeting a position of placed power receiving coil  24  is selected. 
         [0058]    As described above, the detecting coils disposed substantially right above the charging coils are the detecting coils of the first set. Further, the detecting coils disposed across the two neighboring charging coils are the detecting coils of the second set. According to such an association, i.e., in which set of a detecting coil detects a maximum change in an impedance, an operation of controller  10  is determined. As in the present exemplary embodiment, the detecting coils belonging to the same set may be formed separately on a front surface and a back surface of detecting coil substrate  9 . 
       INDUSTRIAL APPLICABILITY 
       [0059]    As described above, the handheld-terminal charging device according to the present invention can reduce power loss and suppress an influence on other devices which use electromagnetic waves. Consequently, it is possible to reduce an influence on an in-vehicle radio particularly when the handheld-terminal charging device is disposed in a vehicle interior of a vehicle. The handheld-terminal charging device is useful as an in-vehicle charging device. 
       REFERENCE MARKS IN THE DRAWINGS 
       [0000]    
       
           1  vehicle 
           2  vehicle interior 
           3  handle 
           4  electronic device 
           5  handheld-terminal charging device 
           6  support plate 
           7  main body case 
           8  charging coil substrate 
           9  detecting coil substrate 
           10  controller 
           11 , Lc 1 , Lc 2 , Lc 3 , Lc 4 , Lc 5  charging coil 
           12 , L 1 , L 2 , L 3 , L 4 , L 5 , L 6 , L 7 , L 8 , L 9  detecting coil 
           13  detecting coil driver 
           14  charging coil driver 
           15  self-oscillation circuit 
           16  detecting coil selection circuit 
           17  impedance measurement circuit 
           18  charging circuit 
           19  charging coil selection circuit 
           20  DC-DC converter 
           21  full-bridge inverter 
           22  power switch 
           23  handheld-terminal 
           24  power receiving coil