Abstract:
The disclosure features mobile electronic devices configured to be wirelessly charged, the devices featuring a receiver resonator configured to capture oscillating magnetic flux, the receiver resonator including: a conductive material layer defining an aperture and a slit extending from the aperture to an outer edge of the conductive material layer, where the conductive material layer forms a back cover of the mobile electronic device, and an inductor having first and second conductor traces, the first trace coupled to a first portion of the conductive material layer adjacent to a first side of the slit and the second trace coupled to a second portion of the conductive material layer adjacent to a second side of the slit.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application incorporates herein by reference and claims priority to U.S. Provisional Patent Application No. 62/204,760 filed Aug. 13, 2015 and entitled “Wireless power enabled enclosures for mobile devices”. 
     
    
     TECHNICAL FIELD 
       [0002]    The field of this invention relates to wireless power transfer. 
       BACKGROUND 
       [0003]    Energy can be transferred from a power source to receiving device using a variety of known techniques such as radiative (far-field) techniques. For example, radiative techniques using low-directionality antennas can transfer a small portion of the supplied radiated power, namely, that portion in the direction of, and overlapping with, the receiving device used for pick up. In this example, most of the energy is radiated away in all the other directions than the direction of the receiving device, and typically the transferred energy is insufficient to power or charge the receiving device. In another example of radiative techniques, directional antennas are used to confine and preferentially direct the radiated energy towards the receiving device. In this case, an uninterruptible line-of-sight and potentially complicated tracking and steering mechanisms are used. 
         [0004]    Another approach is to use non-radiative (near-field) techniques. For example, techniques known as traditional induction schemes do not (intentionally) radiate power, but uses an oscillating current passing through a primary coil, to generate an oscillating magnetic near-field that induces currents in a near-by receiving or secondary coil. Traditional induction schemes can transfer modest to large amounts of power over very short distances. In these schemes, the offset tolerance offset tolerances between the power source and the receiving device are very small. Electric transformers and proximity chargers are examples using the traditional induction schemes. 
       SUMMARY 
       [0005]    In a first aspect, the disclosure features mobile electronic devices configured to be wirelessly charged. The device can include a receiver resonator configured to capture oscillating magnetic flux. The receiver resonator can include a conductive material layer defining an aperture and a slit extending from the aperture to an outer edge of the conductive material layer. The conductive material layer forms a back cover of the mobile electronic device. The receiver resonator can include an inductor having first and second conductor traces. The first trace can be coupled to a first portion of the conductive material layer adjacent to a first side of the slit and the second trace can be coupled to a second portion of the conductive material layer adjacent to a second side of the slit. 
         [0006]    Embodiments of the modules can include any one or more of the following features. 
         [0007]    The conductive material layer can be substantially in a first plane and the inductor is substantially in a second plane and the first and second planes can be substantially parallel to one another. The inductor can be a coil printed on a circuit board. 
         [0008]    The device can include a magnetic material layer in a third plane parallel to the second plane. The magnetic material layer can be positioned opposite the conductive material layer with respect to the inductor. The first edge of the magnetic material layer can extend to a first portion of the outer edge of the conductive material layer. The magnetic material can be configured to cover the slit. The second edge of the magnetic material layer can extend to a second portion of the outer edge of the conductive material layer. 
         [0009]    The device can include a metallic material layer in a fourth plane parallel to the third plane. The metallic material layer can be configured to cover a battery of the mobile electronic device. 
         [0010]    Embodiments of the devices can also include any of the other features disclosed herein, including features disclosed in connection with different embodiments, in any combination as appropriate. 
         [0011]    In another aspect, the disclosure features methods including defining an aperture in a conductive material layer, defining a slit extending from the aperture to an outer edge of the conductive material layer, and coupling a first trace of an inductor to a first portion of the conductive material layer adjacent to a first side of the slit and a second trace to a second portion of the conductive material layer adjacent to a second side of the slit. 
         [0012]    Embodiments of the methods can also include any of the other features disclosed herein, including features disclosed in connection with different embodiments, in any combination as appropriate. 
         [0013]    In another aspect, the disclosure features wireless power systems includes a transmitter that includes a transmitter resonator coil in a first plane. When the resonator coil is driven with an oscillating current, the resonator coil generates an oscillating magnetic field with a dipole moment orthogonal to the first plane. The systems can include a receiver including a receiver resonator configured to capture oscillating magnetic flux. The receiver resonator can include a conductive material layer defining an aperture and a slit extending from the aperture to an outer edge of the conductive material layer. The conductive material layer can form a back cover of the mobile electronic device. The receiver resonator can include an inductor having first and second conductor traces. The first trace can be coupled to a first portion of the conductive material layer adjacent to a first side of the slit and the second trace can be coupled to a second portion of the conductive material layer adjacent to a second side of the slit. 
         [0014]    Embodiments of the systems can also include any of the other features disclosed herein, including features disclosed in connection with different embodiments, in any combination as appropriate. 
         [0015]    In another aspect, the disclosure features receiver resonators configured to capture oscillating magnetic flux. The receiver resonator can include a conductive material layer defining an aperture and a slit extending from the aperture to an outer edge of the conductive material layer. The conductive material layer can form a back cover of the mobile electronic device. The receiver resonator can include an inductor having first and second conductor traces. The first trace can be coupled to a first portion of the conductive material layer adjacent to a first side of the slit and the second trace can be coupled to a second portion of the conductive material layer adjacent to a second side of the slit. 
         [0016]    Embodiments of the receiver resonators can also include any of the other features disclosed herein, including features disclosed in connection with different embodiments, in any combination as appropriate. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1  shows an exemplary embodiment of a wireless power source transferring power to a wirelessly chargeable mobile electronic device having a metallic cover via an oscillating magnetic field. 
           [0018]      FIG. 2  shows an exemplary embodiment of a wireless power transfer system. 
           [0019]      FIG. 3  shows an exploded view of an exemplary embodiment of a wirelessly chargeable device, such as a phone. 
           [0020]      FIGS. 4A-4B  show exemplary embodiments of coupled components to an enclosure for a wirelessly chargeable device, such as a phone. 
           [0021]      FIG. 5A  shows an exploded view of an exemplary embodiment of a wirelessly chargeable mobile device. 
           [0022]      FIG. 5B  shows a cross-sectional view of an exemplary embodiment of a wirelessly chargeable mobile device. 
           [0023]      FIG. 6A  shows an exemplary embodiment of an enclosure for a wirelessly chargeable mobile device, such as a laptop. 
           [0024]      FIGS. 6B and 6C  show exemplary embodiments of the enclosure of  FIG. 6A  coupled to an inductor. 
           [0025]      FIGS. 7A and 7B  show an exemplary embodiment of an enclosure having two or more pieces for the enclosure of a wirelessly chargeable mobile device. 
           [0026]      FIG. 8A  shows an exploded view of an exemplary embodiment of a wirelessly chargeable device, such as a laptop. 
           [0027]      FIG. 8B  shows cross-sectional view of an exemplary embodiment of a wirelessly chargeable mobile device 
           [0028]      FIGS. 9A-9C  show exemplary embodiments of a magnetic material layer positioned relative to the enclosure of  FIG. 6A . 
           [0029]      FIG. 10A  shows an exemplary embodiment of an enclosure for a wirelessly chargeable mobile device, such a laptop. 
           [0030]      FIG. 10B  shows an exemplary embodiment of the enclosure of  FIG. 10A  coupled to an inductor. 
           [0031]      FIG. 10C  shows an exemplary embodiment of a magnetic material layer positioned relative to the enclosure of  FIG. 10A . 
       
    
    
     DETAILED DESCRIPTION 
       [0032]    Enclosures for mobile electronic devices may utilize metallic materials for both mechanical durability and aesthetic quality. Some metallic materials such as aluminum have the advantage of being both strong and lightweight. For example, many smartphones, tablets, and laptops can be made both thin and ruggedized by including these materials in its construction. In practical implementations, an electronic device can be configured to receive wireless power by installing a wireless power receiver within the enclosure of the electronic device, such as within the back cover of a smartphone or bottom chassis of a laptop. However, a metallic enclosure architecture can make a difference in the efficiency of wireless power transfer. In some cases, little to no power can be received by a receiver that is entirely blocked by metallic or conductive materials. Described herein are exemplary systems and methods to enable electronic devices to successfully receive wireless power within acceptable efficiency ranges, such as greater than 50%, 60%, 70%, or more. 
         [0033]    Various aspects of wireless power systems are disclosed, for example, in commonly owned U.S. Patent Application Publication No. 2012/0119569 A1, U.S. Patent Application Publication No. 2013/0200721 A1, and U.S. Patent Application Publication 2013/0033118 A1, U.S. Patent Application Publication 2013/0057364 A1, the entire contents of which are incorporated by reference herein. 
         [0034]      FIG. 1  shows a wireless power transfer system including a wireless power transmitter  102  configured to transfer energy to a wireless power receiver  104  via an oscillating magnetic field  106 . Note that in the exemplary use case shown, the receiver  104  may be placed on or over a transmitter pad  102  for charging. In embodiments, a transmitter pad may be mounted under a surface such as a table and the receiver may rest and charge wirelessly on top of the surface. The receiver  104  can receive power through parts and/or enclosures made of conductive material  108 , such as metal or alloys. In embodiments, some or all of the housing of the receiver can be made of conductive material. For example, the back cover and/or housing of a smartphone, tablet, or personal computer having a wireless power receiver may be primarily made of aluminum, aluminum alloy, magnesium, copper, or other alloy. 
         [0035]      FIG. 2  shows a schematic of an exemplary wireless power system. The transmitter side  102  can include a power supply  202  (such as AC mains, battery, solar panel, and the like), an AC/DC converter  203  (such as a buck, boost, buck-boost, etc.), an amplifier  204  (such an RF inverter), an impedance matching network (Tx IMN)  206 , a transmitter resonator  208 . The transmitter resonator  208  includes one or more transmitter resonator coils coupled, in parallel or in series, to one or more capacitors. The receiver side  104  can include a load  210  (such as a battery of a mobile electronic device), a DC/DC converter  211 , a rectifier  212 , an impedance matching network (Rx IMN)  214 , and a receiver resonator  216 . The receiver resonator  216  includes one or more receiver resonator coils coupled, in parallel or in series, to one or more capacitors. 
         [0036]    In exemplary embodiments, a coil of the receiver resonator  216  can be used as the enclosure of an electronic device, such as a smartphone or laptop. For example, the back enclosure of the electronic device can be shaped to capture magnetic flux from a wireless power transmitter.  FIG. 3  shows an exemplary embodiment of a wirelessly chargeable mobile device. The device includes the body  302  of the mobile electronic device (such as a smartphone) connected to a battery  304 , a layer of conductive material  306  (such as aluminum, copper, magnesium, and the like) to provide a shield between the body  302  and magnetic flux in the layer of magnetic material  308  (such as ferrite), and an outer layer  310  made of conductive material. The magnetic material  308  can act as a shield between the receiver resonator and the body  302  plus layer  306  and can act as a guide and/or return path for magnetic flux captured by the receiver resonator. The outer layer  310  of conductor forms both the back of the mobile device and the receiver resonator coil. The shape of the outer layer  310  can be formed as a “one-turn” inductor of the receiver resonator coil. The outer layer  310  includes a slit  312  from an outer edge of the outer layer  310  to an aperture  314  defined in the outer layer  310 . This shape allows for an oscillating magnetic field to be captured by the resonator coil. In embodiments, a module may include the outer layer  310 , magnetic material layer  308 , and shield  306 . This module may be manufactured separately and mounted onto the mobile device. 
         [0037]    As shown in  FIG. 4A , the two edges  402 ,  404  created by the slit  312  can be coupled to one or more capacitors  406  and/or, as shown in  FIG. 4B , a circuit board  408 . The views shown in  FIG. 4A  and  FIG. 4B  are on the inside of the outer layer (and therefore, opposite side of the view shown in  FIG. 3 ). In embodiments, the capacitor  406  can be connected to the two edges  402 ,  404  close to the slit  312 . For example, the capacitor  406  can be connected across the slit  312  as shown in  FIG. 4A , or can connect to the two edges  402 ,  404  adjacent to the slit  312  (via a circuit board  408 ) as shown in  FIG. 4B . The circuit board  408  can include the one or more capacitors, an impedance matching network  214 , a rectifier  212 , a DC-to-DC converter  211 , etc. The circuit board  408  can be coupled to the outer layer  310  by wires and can be positioned between the outer layer  310  and the body  302 , for example, by folding or positioning the circuit board  408  behind the outer layer  310 . In embodiments, the conductive layer  306  and magnetic material layer  308  can be positioned between the outer layer  310  and the electronics board  408 . In other embodiments, the conductive layer  306  and magnetic material layer  308  can be positioned between the circuit board  408  and the body  302 . 
         [0038]    In embodiments, the voltage induced on the “one-turn resonator coil” may be too low to use to power a load or battery of the mobile electronic device. Additional inductor turns can be coupled to the one-turn coil to increase inductance, quality factor, and/or induced voltage.  FIG. 5A  shows an exemplary embodiment of a wirelessly chargeable mobile device. The device includes the body  302  connected to a battery  304 , a layer of conductive material  502 , a layer of magnetic material  504 , an inductor  506 , and an outer layer  310  made of conductive material. The inductor  506  can be coupled, inductively or directly by wire, to the “one-turn” coil created by the outer layer  310  of conductive material. Note that in some embodiments, the amount of conductive material  502  and magnetic material  504  can be reduced in area to cover the inductor  506  as compared to that shown in  FIG. 3 . In embodiments, the inductor  506  can be a coil on a printed circuit board or made of Litz wire. The outer layer  310  coupled to at least one capacitor may be used as a repeater resonator to a receiver resonator coil  506  positioned behind the outer layer  310 .  FIG. 5B  shows a cross-sectional view of an exemplary embodiment of a wirelessly chargeable mobile device. The mobile device includes the body  302  connected to a battery  304 , a layer of conductive material  502 , a layer of magnetic material  504 , an inductor  506 , and an outer layer  310  comprising conductive material. Further, a circuit board  508  is included between the outer layer  310  and the body of the mobile device  302 ; the circuit board  508  can include the one or more capacitors, an impedance matching network  214 , a rectifier  212 , a DC-to-DC converter  211 , etc. In embodiments, a module may include the outer layer  310 , inductor  506 , magnetic material layer  308 , and shield  306 . This module may be manufactured separately and mounted onto the mobile device. 
         [0039]      FIG. 6A  shows an exemplary embodiment of an outer layer  602  of conductive material for a mobile electronic device such as a tablet, laptop, and the like. This outer layer  602  can be attached to a back of a laptop and have a dual-role as both the enclosure and inductor for capturing magnetic flux from a wireless power transmitter. The outer layer  602  of conductive material has an aperture  604  in its approximate center. Additionally, a slit  606  runs from one edge of the outer layer  602  to the aperture  604 , which can create a “one-turn” coil as part of a receiver resonator.  FIG. 6B  shows an additional coil  608  coupled to the outer layer  602 . Leads  610  can then be connected to at least one capacitor. The “one-turn” coil  602  can be coupled to the inductor  608  such that the magnetic field from any one segment of the overall resonator coil (“one-turn” coil  602  plus inductor  608 ) does not cancel with another segment of the overall resonator coil. In other words, the current induced in the outer layer  602  and coil  608  flows in the same direction. Thus,  FIG. 6B  shows the “one-turn” coil  602  turn clockwise and connect with inductor  608  at solder point  612  and then continue clockwise through the inductor  608 .  FIG. 6C  shows an exemplary embodiment of coupling the “one-turn” coil  602  into the inductor  614  such that the “one-turn” coil is part of the inductor turn  616 . In embodiments, the coil  608  can be any size within the area of the outer layer  602 . However, the amount of magnetic flux that can be captured by the coil  608  can be limited by the size of aperture  604 . In embodiments, the size of the aperture  604  can be similarly sized to the innermost loop of the inductor. One advantage of a larger coil may be the ability to fit more turns, which may increase the quality factor of the overall resonator coil. In embodiments, the quality factor of the overall resonator coil can be greater than 20, 50, 75, 100, 200, etc. In embodiments, the “one-turn” coil  602  coupled to inductor  608  can increase coupling between the receiver resonator and the transmitter resonator. For example, coupling can be increased by at least 10%, 20%, 30% or more. Note that in both embodiments shown in  FIG. 6B  and  FIG. 6C , the current path created by the outer layer  602  is in series with the current path of the coil  608  and  614  respectively. Note also that in  FIG. 6C , a cross-over  618  in the connections to the outer layer is formed to maintain the directionality of the current path. 
         [0040]      FIG. 7A  shows an exemplary embodiment of an outer layer having two pieces  702 ,  704  of conductive material for a mobile device such as a tablet, laptop, and the like. These two pieces  702 ,  704  of conductive material may be created by two slits  706  and  708  running from the outer edges of the outer layer to the aperture  710 . The two pieces are coupled to the inductor  712  such that the current paths created by each piece  702 ,  704  are in series with current path of the inductor  712 . Note that the inductor  712  can be printed on a circuit board (PCB)  713 .  FIG. 7B  shows an exemplary embodiment of an outer layer having four pieces  714 ,  716 ,  718 , and  720  of conductive material. The four pieces can be defined by four slits  722 ,  724 ,  726 , and  728  running from the outer edges of the outer layer to the aperture  730 . The four pieces  714 ,  716 ,  718 , and  720  are coupled to the inductor  732  such that the current paths created by a piece plus a loop of the inductor coil  732  are in parallel with current paths of the other pieces plus turns of the inductor  732 . For example, current path A includes piece  718  connected to loop  732   a  of inductor  732 ; current path B includes piece  714  connected to loops  732   b  and  732   c ; current path C includes piece  716  connected to loops  732   d  and  732   e ; and current path D includes pieces  720  connected to loop  732   f . Each of these current paths are in parallel with each other. 
         [0041]      FIG. 8A  shows an exemplary embodiment of a wirelessly chargeable mobile device. The device includes the body  802 , a layer of conductive material  804 , a layer of magnetic material  806 , an inductor  808 , and an outer layer  602  made of conductive material.  FIG. 8B  shows cross-sectional view of an exemplary embodiment of a wirelessly chargeable mobile device including the materials described above for  FIG. 8A . The device also includes a circuit board  810  connected to the inductor  808 . 
         [0042]      FIGS. 9A-9C  show exemplary embodiments of a layer of magnetic material  902  positioned over inductor  608  on the outer layer  602 . In  FIG. 9A , the layer of magnetic material is positioned over the inductor  608  and aperture  604  and extended to an outer edge  904 . This position of the magnetic material  902  provides a return or “escape” path for the magnetic field lines from the transmitter. Providing a return path for the field lines decreases losses in the metallic surfaces in the mobile device, thus preventing a decrease in efficiency. For example, losses in the metallic surfaces can be due to induced eddy currents.  FIG. 9B  shows a layer of magnetic material  906  positioned over the inductor  608  and aperture  604  and extended over the slit  606 . This has the similar effect of providing a return path for the magnetic field lines. In embodiments, the magnetic material can be ferrite, for example, having an approximate thickness of 0.3 mm, 0.5 mm, 0.8 mm, 1.1 mm, or more.  FIG. 9C  shows a layer of magnetic material  908  positioned over the inductor  608  and extending two outer edges  910 ,  912  of the outer layer  602 . Because the layer of magnetic material  908  extends to two outer edges  910 ,  912 , there is an increased area for a return path for magnetic field lines. 
         [0043]      FIG. 10A  shows an exemplary embodiment of an outer layer  1002  of conductive material for a mobile electronic device such as a tablet, laptop, and the like. The outer layer  1002  includes an aperture near a corner. Slit  1006  extends from the outer edge of the outer layer  1002  to the aperture. This effectively creates a “one-turn” coil. In embodiments, placing the aperture and slit in a corner of the outer layer  1002  can change the inductance of the “one-turn” coil as compared to an aperture and slit placed as shown in  FIG. 6A .  FIG. 10B  shows an exemplary embodiment of an outer layer  1002  coupled to an inductor  1008  positioned over aperture  1004 .  FIG. 10C  shows an exemplary embodiment of a layer of magnetic material  1012  positioned over inductor  1008  on the outer layer  1002 . This position of the magnetic material  1012  provides a return path for magnetic field lines from the source. Because magnetic material  1012  is positioned in a corner, it can provide that return path on more than one outer edge of the outer layer  1002 . Furthermore, this position may allow the use of less magnetic material  1012  because of its close proximity to the edges at the corner. Less magnetic material can mean decreased overall weight and cost. 
         [0044]    In exemplary embodiments, the receiver resonator coil, while thin, can be maximized in the area of the back of the mobile device, keeping in mind that certain areas such as a camera lens or speaker should not be covered. 
         [0045]    In exemplary embodiments, a logo can be etched into the outer layer of conductive material. 
         [0046]    In exemplary embodiments, the outer layer only covers a portion of the back surface of the mobile electronic device. Other materials, such as glass, plastics, wood/plant materials, and leather may be used together with the metal back enclosure to form the back cover of the mobile electronic device. 
         [0047]    In exemplary embodiments, the resonator coil under the outer layer can be used as a dual use antenna. For example, the same coil can be used as a wireless power transfer coil at 6.78 MHz and as a coil for communication at 13.56 MHz. In embodiments, the wireless power transfer coil can transfer power at other frequencies such as 100 kHz-250 kHz. 
         [0048]    While the disclosed techniques have been described in connection with certain preferred embodiments, other embodiments will be understood by one of ordinary skill in the art and are intended to fall within the scope of this disclosure. For example, designs, methods, configurations of components, etc. related to transmitting wireless power have been described above along with various specific applications and examples thereof. Those skilled in the art will appreciate where the designs, components, configurations or components described herein can be used in combination, or interchangeably, and that the above description does not limit such interchangeability or combination of components to only that which is described herein. 
         [0049]    All documents referenced herein are hereby incorporated by reference.