Abstract:
There are provided a coil for cordless charging, which may be formed as a thin coil in spite of the presence of a plurality of coils included therein, and a cordless charging apparatus using the same. The cordless charging apparatus includes: a coil unit including coil substrates having a coil pattern and a connection substrate having one end interposed between the coil substrates and electrically connected to the coil pattern and the other end electrically connected to the outside; and a case accommodating the coil unit therein.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the priority of Korean Patent Application No. 10-2012-0155770 filed on Dec. 28, 2012, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a coil for cordless charging and a cordless charging apparatus using the same, and more particularly, to a coil for cordless charging, which may be formed as a thin coil in spite of the presence of a plurality of coils included therein, and a cordless charging apparatus using the same. 
         [0004]    2. Description of the Related Art 
         [0005]    In general, portable electronic devices such as mobile communications terminals, personal digital assistants (PDAs), and the like, include a rechargeable secondary battery. 
         [0006]    In order to charge a battery of a portable electronic device, a charging apparatus is required to provide electrical energy to the battery by using commercially available household power. 
         [0007]    In general, a charging apparatus and a battery have a contact terminal, respectively, and when the two contact terminals thereof are connected, the charging apparatus and the battery are electrically connected. 
         [0008]    In this case, however, if the contact terminal is protruded outwardly, an appearance thereof may not be aesthetically pleasing, and the contact terminal may be contaminated by a foreign material to degrade a contact state. Also, when the battery is short-circuited or exposed to moisture due to inadvertent user actions, charged energy may be easily lost. 
         [0009]    As an alternative to the contact type charging method, a cordless charging apparatus (or a contactless power transmission apparatus) transmitting power to charge a battery in such a manner that contact terminals of the cordless charging apparatus and the battery are not in contact has been proposed. 
         [0010]    In general, a cordless charging apparatus refers to apparatus transmitting power to a contactless power reception apparatus (e.g., a portable device) having a battery, cordlessly. 
         [0011]    Such a cordless charging apparatus transmits power by using electromagnetic induction, and to this end, a coil is provided therein. 
         [0012]    However, in a related art cordless charging apparatus, connection portions connecting the coil and a driving circuit are formed by soldering. Thus, the related art coil has a thickness disadvantageously increased by as much as a solder ball formed due to soldering. 
         [0013]    In line with the recent tendency for ultra-thin electronic devices, an increase in thickness due to a solder ball has emerged as a problem to be tackled and, as a solution, a coil structure for cordless charging is required. 
       Related Art Document 
       [0014]    (Patent document 1) Korean Patent Laid Open Publication No. 2010-0092741 
       SUMMARY OF THE INVENTION 
       [0015]    An aspect of the present invention provides a coil for cordless charging, which has a structure without a solder ball, and a cordless charging apparatus having the same. 
         [0016]    Another aspect of the present invention provides a coil for cordless charging, which is formed to be thin in spite of a plurality of coils included therein, and a cordless charging apparatus having the same. 
         [0017]    According to an aspect of the present invention, there is provided a coil for cordless charging, including: coil substrates having a coil pattern; and a connection substrate having one end interposed between the coil substrates and electrically connected to the coil pattern and the other end electrically connected to the outside. 
         [0018]    The coil pattern may include coil strands formed on both surfaces of the respective coil substrates, and the coil strands may be connected in parallel. 
         [0019]    The coil substrates may include first and second coil substrates, and the connection substrate may be interposed between the first and second coil substrates and may be integrally formed with the first and second coil substrates. 
         [0020]    The coil substrates may be rigid substrates, and the connection substrate may be a flexible substrate. 
         [0021]    The coil pattern may include a plurality of coil strands formed on the coil substrates, and the plurality of coil strands may be uniformly or equally distributed based on the center of the connection substrate. 
         [0022]    According to another aspect of the present invention, there is provided a cordless charging apparatus including: a coil unit including coil substrates having a coil pattern and a connection substrate having one end interposed between the coil substrates and electrically connected to the coil pattern and the other end electrically connected to the outside; and a case accommodating the coil unit therein. 
         [0023]    The coil pattern may be formed by disposing a plurality of coil strands in line abreast within the coil substrates. 
         [0024]    The coil unit may include the coil pattern formed on at least one of both surfaces of the coil substrate, and a contact pad may be formed in both ends of the coil pattern and electrically connected to the connection substrate. 
         [0025]    The connection substrate may include a connection pad formed in a position corresponding to the contact pad and electrically connected to the contact pad. 
         [0026]    The coil pattern may include coil strands formed to have the same shape on both surfaces of the respective coil substrates. 
         [0027]    The coil substrates may have conductive vias formed at positions in which ends of the coil pattern are disposed, and the coil strands formed on both surfaces of the respective coil substrates may be electrically connected by the conductive vias. 
         [0028]    The coil substrates may be rigid substrates, and the connection substrate may be a flexible substrate. 
         [0029]    The coil pattern may include coil strands formed on both surfaces of the respective coil substrates, and the coil strands may be connected in parallel. 
         [0030]    The coil substrates may include first and second coil substrates, and the connection substrate may be interposed between the first and second coil substrates and may be integrally formed with the first and second coil substrates. 
         [0031]    The cordless charging apparatus may further include a magnetic unit attached to one surface of the coil unit to form a magnetic path. 
         [0032]    The magnetic unit may be formed to have a flat plate-like shape, and may include at least any one of a ferrite sheet, a metal composite sheet, and an amorphous sheet. 
         [0033]    The cordless charging apparatus may further include an adhesive unit interposed between the magnetic unit and the coil unit and attaching the magnetic unit and the coil unit. 
         [0034]    The cordless charging apparatus may further include a voltage conversion unit converting AC power supplied from the outside into an AC voltage having a particular frequency, and providing the converted AC voltage to the coil unit. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0035]    The above and other aspects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
           [0036]      FIG. 1  is a perspective view schematically illustrating an electronic device and a cordless charging apparatus according to an embodiment of the present invention; 
           [0037]      FIG. 2  is a cross-sectional view taken along line A-A′ in  FIG. 1 ; 
           [0038]      FIG. 3  is an exploded perspective view schematically illustrating a contactless power transmission apparatus according to an embodiment of the present invention; 
           [0039]      FIG. 4  is a side view of the contactless power transmission apparatus of  FIG. 3 ; 
           [0040]      FIG. 5  is a side view of the contactless power transmission apparatus of  FIG. 4  in an assembled state; 
           [0041]      FIG. 6  is a cross-sectional view of a coil unit illustrated in  FIG. 3 , taken along line B-B′; 
           [0042]      FIG. 7  is a sectional view of the coil unit of  FIG. 6  in a disassembled state; 
           [0043]      FIG. 8  is an exploded perspective view of the coil unit illustrated in  FIG. 3 ; and 
           [0044]      FIG. 9  is a graph showing efficiency of the coil unit according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0045]    Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. The invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the shapes and dimensions of elements may be exaggerated for clarity, and the same reference numerals will be used throughout to designate the same or like components. 
         [0046]      FIG. 1  is a perspective view schematically illustrating an electronic device and a cordless charging apparatus according to an embodiment of the present invention, and  FIG. 2  is a cross-sectional view taken along line A-A′ in  FIG. 1 . 
         [0047]    Referring to  FIGS. 1 and 2 , an electronic device  10  according to an embodiment of the present invention may include a battery  12  and a contactless power reception apparatus  100  supplying power to the battery  12  to charge the battery  12 . 
         [0048]    The battery  12  may be a secondary battery that may be charged and discharged, and may be configured to be detachably attached to the electronic device  10 . 
         [0049]    The contactless power reception apparatus  100  may be accommodated in a case  11  of the electronic device  10  and may be directly attached to an inner surface of the case  11  or may be disposed as adjacently as possible thereto. 
         [0050]    A cordless charging apparatus  20  according to an embodiment of the present invention is provided to charge the battery  12  of the electronic device  10 . To this end, the cordless charging apparatus  20  may have a contactless power transmission apparatus  200  provided in a case  21  thereof. 
         [0051]    The cordless charging apparatus  20  may convert commercially available household AC power supplied from the outside into DC power, convert the DC power into an AC voltage having a particular frequency, and provide the same to the contactless power transmission apparatus  200 . To this end, the cordless charging apparatus  20  may include a voltage conversion unit  22  converting commercially available household AC power into an AC voltage having a particular frequency. 
         [0052]    When the AC voltage is applied to a coil of the contactless power transmission apparatus  200 , a magnetic field in the vicinity of the coil is changed. Then, according to the change in the magnetic field, a voltage is applied to the contactless power reception apparatus  100  of the electronic device  10  disposed to be adjacent to the contactless power transmission apparatus  200 , and thus, the battery  12  is charged. 
         [0053]    Hereinafter, the contactless power transmission apparatus  200  provided in the cordless charging apparatus  20  will be described in detail. 
         [0054]      FIG. 3  is an exploded perspective view schematically illustrating a contactless power transmission apparatus according to an embodiment of the present invention.  FIG. 4  is a side view of the contactless power transmission apparatus of  FIG. 3 .  FIG. 5  is a side view of the contactless power transmission apparatus of  FIG. 4  in an assembled state.  FIG. 6  is a cross-sectional view of a coil unit illustrated in  FIG. 3 , taken along line B-B′.  FIG. 7  is a sectional view of the coil unit of  FIG. 6  in a disassembled state;  FIG. 8  is an exploded perspective view of the coil unit illustrated in  FIG. 3 . 
         [0055]    Referring to  FIGS. 3 through 8 , the contactless power transmission apparatus  200  may include a coil unit  210  and a magnetic unit  220 . 
         [0056]    The magnetic unit  220 , having a flat plate-like shape (or a sheet-like shape), may be disposed on one surface of the coil unit  210  and fixedly attached to the coil unit  210 . The magnetic unit  220  is provided to effectively form a magnetic path of a magnetic field generated by a coil pattern  215 . To this end, the magnetic unit  220  may be made of a material allowing a magnetic path to be easily formed. In detail, a shielding sheet having magnetic permeability, such as a ferrite sheet, a metal composite sheet, an amorphous sheet, or the like, may be used. 
         [0057]    However, the magnetic unit  220  is not limited to the foregoing configuration and may be variously modified; ferrite powder or a magnetic substance solution may be applied to one surface of the coil unit  210 , or the like. 
         [0058]    Also, the magnetic unit  220  according to the present embodiment may be used as a shielding sheet for shielding electromagnetic waves or leakage flux on an outer surface thereof. In this case, a shielding sheet having magnetic permeability, such as a metal composite sheet, an amorphous sheet, or the like, may be used as the magnetic unit  220 . However, the present invention is not limited thereto. 
         [0059]    Also, various applications may be implemented. Namely, rather than using the magnetic unit  220  as a shielding sheet, a separate shielding sheet may be added to an outer surface of the magnetic unit  220 , or the magnetic unit  220  may be formed by using a plurality of sheets, rather than a single sheet. Namely, a ferrite sheet and a shielding sheet may be laminated to form the magnetic unit  220 . 
         [0060]    Also, in the contactless power transmission apparatus  200 , in order to firmly attach the coil unit  210  and the magnetic unit  220 , an adhesive unit  240  may be interposed therebetween. 
         [0061]    The adhesive unit  240  may be disposed between the coil unit  210  and the magnetic unit  220  to bind or glue them together. The adhesive unit  240  may be formed as an adhesive sheet or an adhesive tape. Alternatively, the adhesive unit  240  may be configured to contain ferrite powder. Namely, the adhesive unit  240  may be configured to have magnetism together with the magnetic unit  220 . 
         [0062]    The coil unit  210  may include at least one coil substrate  212  and a connection substrate  230 . 
         [0063]    The coil substrate  212  according to the present embodiment is an insulating substrate having rigidity. For example, the coil substrate  212  may be a printed circuit board (PCB), a ceramic substrate, a pre-molded substrate, a direct bonded copper (DBC) substrate, or an insulated metal substrate (IMS). 
         [0064]    However, the present invention is not limited thereto and a flexible PCB which is thin and has a wiring pattern, such as a film, a thin PCB, or the like, may also be used as necessary. 
         [0065]    As illustrated in  FIGS. 6 through 8 , the coil unit  210  according to the present embodiment may include two coil substrates (hereinafter, referred to as ‘a first coil substrate’ and ‘a second coil substrate’) and a single connection substrate  230 . However, the present invention is not limited thereto and the coil unit  210  may be variously modified as necessary; for example, the coil unit  210  may include three or more coil substrates. 
         [0066]    The coil pattern  215  may be a wiring pattern formed on at least one surface of the coil substrate  212 . The coil pattern  215  according to the present embodiment may be formed on both surfaces of the coil substrate  212  and have a vortex shape (or an eddy shape), and contact pads  218  may be formed on both ends of the coil pattern  215  in order to electrically connect the coil pattern  215  to a via  219  or the connection substrate  230 . 
         [0067]    Both ends of respective coil strands  215   a  and  215   b  formed on both surfaces of the coil pattern  215  may be electrically connected to form a parallel circuit as a whole. To this end, the conductive vias  219  may be formed on portions in which both ends of the coil strands  215   a  and  215   b  are disposed, in order to electrically connect the coil strands  215   a  and  215   b  on both surfaces of the coil substrate  212 . 
         [0068]    Also, the contact pad  218  may be formed on one end of the via  219  and electrically connected to the outside. 
         [0069]    Meanwhile, in the present embodiment, for example, the coil pattern  215  has a quadrangular vortex shape on the whole, but the present invention is not limited thereto and the coil pattern  215  may be variously modified; for example, it may have a circular vortex shape or a polygonal vortex shape. 
         [0070]    Also, an insulating protective layer (e.g., a resin insulating layer, not shown) for protecting the coil pattern  215  against the outside may be formed on an upper portion of the coil pattern  215  as necessary. 
         [0071]    The coil unit  210  may include the connection substrate  230  electrically connecting the voltage conversion unit ( 22  in  FIG. 1 ) applying power to the coil pattern  215  and the coil patterns  215  of the coil substrates  212 . 
         [0072]    The connection substrate  230  may be formed as a thin film circuit board (e.g., a flexible board) with a wiring pattern formed therein. 
         [0073]    The connection substrate  230  may be electrically connected to voltage conversion unit  22  of the cordless charging apparatus  20 , and may have connection pads  238  electrically connected to the contact pads  218  in portions in which the contact pads  238  face the contact pads  218 , and vias  239  connecting them. 
         [0074]    In particular, in the coil unit  210 , the coil substrates  212  may be disposed on both surfaces of the connection substrate  230  and integrally connected to the connection substrate  230 . 
         [0075]    The coil substrates  212  and the connection substrate  230  may be integrally fabricated during a fabrication process. Namely, during a process of fabricating the coil substrates  212 , the connection substrate  230  may be laminated to be interposed between the coil substrates  212 . However, the present invention is not limited thereto and the coil substrates  212  and the connection substrate  230  may be separately fabricated and may be integrally attached through a method such as bonding, compressing, or the like. 
         [0076]    Meanwhile, in the coil pattern  215  according to the present embodiment, since two coil substrates  212  are formed on both surfaces of the connection substrate  230 , a total of four coil strands  215   a  to  215   d  may be formed. Both ends of the four respective coil strands  215   a  to  215   d  are electrically connected to each other by the vias  219  and the connection substrate  230 . Namely, the four coil strands  215   a  to  215   d  may be connected in parallel to form a single coil pattern  215 . 
         [0077]    The contactless power transmission apparatus according to the present embodiment has a hybrid substrate structure in which the connection substrate  230  is interposed between the coil substrates  212  and integrally formed, and the coil is electrically connected to the outside through the connection substrate  230 . 
         [0078]    Thus, since an electric wire is not bonded to both ends of the coil as it is in the related art, a solder ball due to soldering, or the like, may be omitted. Thus, an increase in a thickness of the coil unit due to a solder ball is prevented, and the coil unit may be maintained to be very thin. 
         [0079]    Also, the contactless power transmission apparatus according to the present embodiment can provide efficiency higher than that of the case in which substrates are connected by solder balls. 
         [0080]      FIG. 9  is a graph showing efficiency of the coil unit according to an embodiment of the present invention, in which efficiency of the coil unit (hybrid type) according to the foregoing embodiment and that of the structure (connection through soldering) connecting a rigid substrate and a flexible substrate in a soldering manner are shown. 
         [0081]    Here, an output (W) indicates a final output of a portable device as a reception (Rx) end, and efficiency indicates a ratio of an output of the portable device as a reception end to an input of the cordless charging apparatus. 
         [0082]    Referring to  FIG. 9 , it can be seen that, when the coil unit is formed as a hybrid type coil unit, efficiency higher than that of the case of the soldering type connection is obtained within the entire power range. Namely, since resistance due to a solder ball is omitted, the coil unit has enhanced overall efficiency. 
         [0083]    Also, in the contactless power transmission apparatus according to the present embodiment, since the connection substrate and the coil substrates are integrally formed, although the connection substrate moves, such a movement is not transmitted to a connection portion between the connection substrate and the coil substrates, whereby high bonding reliability can be secured in comparison to the related art. 
         [0084]    In addition, since the process of soldering an electric wire such as in the related art is omitted, a fabrication process and fabrication time can be reduced. 
         [0085]    In addition, in the coil unit according to the present embodiment, a single coil pattern is formed by a plurality of coil strands connected in parallel. Thus, although the coil pattern according to the present embodiment is formed as a pattern on the coil substrate, an effect of using a stranded type coil (e.g., a Litz wire) formed by twisting several electric wires can be obtained. The use of such a stranded type coil minimizes a loss (e.g., an AC resistance value, or the like) made due to a skin effect and an eddy current in a low frequency. 
         [0086]    In this manner, in the contactless power transmission apparatus, since the coil pattern is formed in a stranded type and a thickness of the coil unit is prevented from being increased due to a solder ball, or the like, an overall thickness of the contactless power transmission apparatus can be reduced. 
         [0087]    The configuration of the contactless power transmission apparatus described above may also be applied in the same manner to the contactless power reception apparatus  100  provided in the portable device ( 10  in  FIG. 1 ). Thus, a detailed description of the contactless power reception apparatus will be omitted. 
         [0088]    Meanwhile, in the above embodiment, the case in which only a single coil strand is formed on one surface of the coil substrate is described as an example, but the present invention is not limited thereto. 
         [0089]    Namely, in a case in which the coil substrate is formed to have a large size, a plurality of coil strands may be formed on one surface thereof, and in a case in which the coil substrate is formed to have a small size, only a single coil may be formed on one surface thereof, as in the present embodiment. 
         [0090]    Also, in the present embodiment, the coil strands formed on the respective surfaces of the coil substrate are formed in positions in which the coil strands are projected on each other (namely, the coil strands are formed in positions in which the coil strands correspond to each other in a vertical direction), but the present invention is not limited thereto. Namely, the coil strands formed on the respective surfaces of the coil substrate may be formed in positions deviating from one another, rather than in positions corresponding to one another. Namely, various modifications may be implemented as necessary. 
         [0091]    In addition, in the present embodiment, the coil substrates and the connection substrate are separately fabricated and laminated to form the coil unit, but the present invention is not limited thereto. Namely, various modifications may be implemented. For example, the coil substrate with the coil pattern formed thereon and the connection substrate with the wiring pattern formed thereon are first laminated and vias penetrating both the coil substrate and the connection substrate may be subsequently formed to electrically connect the coil pattern of the coil substrate and the wiring pattern of the connection substrate. 
         [0092]    Also, in the foregoing embodiments, the contactless power transmission apparatus employed in a cordless charging apparatus has been described as an example, but the present invention is not limited thereto and may be extensively applied to any electronic device that may be used upon being charged with power and any power transmission device that may transmit power. 
         [0093]    As set forth above, according to embodiments of the invention, the coil for cordless charging has a hybrid substrate structure in which the connection substrate is interposed between the coil substrates and integrally formed, and the coil is electrically connected to the outside through the connection substrate. 
         [0094]    Thus, since an electric wire is not bonded to both ends of the coil as it is in the related art, a solder ball due to soldering, or the like, may be omitted. Thus, an increase in a thickness of the coil for cordless charging due to a solder ball, or the like, can be prevented, and the cordless charging apparatus may be maintained to be very thin. 
         [0095]    Also, since the connection substrate and the coil substrates are integrally formed, although the connection substrate moves, such a movement is not transmitted to a connection portion between the connection substrate and the coil substrates, whereby high bonding reliability can be secured in comparison to the related art. 
         [0096]    In addition, since the process of soldering an electric wire such as in the related art is omitted, a fabrication process and fabrication time can be reduced. 
         [0097]    In addition, in the coil for cordless charging according to the present embodiment, a single coil pattern is formed by a plurality of coil strands connected in parallel. Thus, although the coil pattern according to the present embodiment is formed as a pattern on the coil substrate, an effect of using a stranded type coil (e.g., a Litz wire) formed by twisting several electric wires can be obtained. The use of such a stranded type coil minimizes a loss (e.g., an AC resistance value, or the like) made due to a skin effect and an eddy current in a low frequency. 
         [0098]    While the present invention has been shown and described in connection with the embodiments, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the spirit and scope of the invention as defined by the appended claims.