Patent Publication Number: US-2017353046-A1

Title: Modular and assemblable wireless charging system and device

Description:
BACKGROUND 
     Field 
     The present application relates generally to wireless power charging of chargeable devices, and more particularly, to modular and assemblable wireless charging systems, devices, and methods. 
     Background 
     An increasing number and variety of electronic devices are powered via rechargeable batteries. Such devices include mobile phones, electric vehicles, portable music players, laptop computers, tablet computers, computer peripheral devices, communication devices (e.g., Bluetooth devices), digital cameras, hearing aids, and the like. While battery technology has improved, battery-powered electronic devices increasingly require and consume larger amounts of power, thereby often requiring recharging. Wireless charging systems permit recharging such devices through coupling a magnetic or electrical field generated by a transmit coil, included in a transmitter, to a receiver coil. Wireless charging systems using multiple transmit coils, each fed by a separate power amplifier, or single transmit coils having numerous turns may have advantages such as being able to provide wireless energy over a larger area, where that energy may be used for charging multiple devices. Additionally, the use of multiple transmit coils or numerous turns may provide a more uniform wireless field and may improve efficiency. However, the transmit coils are typically fixed in size covering a large area as required by the transmit coils. Further, being of a fixed size, the transmit coils are capable of charging receivers of predetermined sizes or a range of predetermined sizes. Thus, there is a need for systems and methods for providing a wireless charging systems capable of providing adaptable and modular transmit coils that can be dynamically modified so as to alter the size, area, and shape of the magnetic or electric filed generated by the transmit coil. 
     SUMMARY 
     Various implementations of methods and apparatus within the scope of the appended claims each have several aspects, no single one of which is solely responsible for the desirable attributes described herein. Without limiting the scope of the appended claims, some prominent features are described herein. 
     Details of one or more implementations of the subject matter described in this specification are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages will become apparent from the description, the drawings, and the claims. 
     One aspect of the present disclosure provides a device for distributing power. The device includes multiple assemblable elements. Each assemblable element may be configured to permit interlocking between one or more of the multiple assemblable elements. The multiple assemblable elements include at least a first assemblable element including a first portion of a coil, and a second assemblable element including a second portion of the coil. The first and second portions of the coil are electrically interconnected and configured to provide wireless power. In some embodiments, the first assemblable element is configured to supply power from a power source to the other assemblable elements. In some embodiments, each assemblable element includes a portion of the coil, where the portions of the coil are electrically interconnected to form one or more coils. In some embodiments, the wireless power is provided based on the electrical interconnection of all portions of the coil. In some embodiments, the first and second portions of the coil are electrically interconnected through a coil in line and a coil out line. The assemblable elements may include an interlocking element, configured to permit the plurality of assemblable elements to be mechanically interconnected. 
     In some embodiments, the multiple assemblable elements are interconnected in an arrangement. In some embodiments, the multiple assemblable elements may include at least a third assemblable element. The third assemblable element may include a third portion of the coil, where the first, second and third portions of the coil are electrically interconnected and configured to provide wireless power. In one embodiment, the assemblable elements are arranged in a two-dimensional arrangement. In another embodiments, the assemblable elements are arranged in a three-dimensional arrangement. In some embodiments, the assemblable elements are tubular, where the assemblable elements are configured to interlock to form a tubular shaped coil. 
     In some embodiments, the coil includes multiple loops that may be based on the electrical interconnection of the plurality of assemblable elements. The multiple loops may include at least a first and second loop, where the first loop may be disposed on an outer most edge or periphery of the interlocking assemblable elements and the second loop may be disposed concentric to and nested within the first loop. In some embodiments, one of the assemblable elements may be a crossover assemblable element. The crossover assemblable element may include one or more switches configured to control the density of loops at the outer edge of the interlocked assemblable elements, and configured to periodically skip the second loop. In some embodiments, alternatively or in combination, the loops may include a passive loop. 
     Another aspect of the present disclosure provides a method for distributing power. The method includes providing multiple assemblable elements, where each assemblable element is configured to interlock between one or more of the assemblable elements and the each of the plurality of assemblable elements comprises a portion of a coil. The method also includes selectively interlocking the assemblable elements, where interlocking the assemblable elements electrically interconnects the portions of the coil. In some embodiments, selectively interlocking the assemblable elements further includes forming a coil comprising a plurality of loops based on electrically interconnecting the portions of the coil. In some embodiments, the loops may include a first loop and a second loop, the first loop disposed on the periphery of the interlocking assemblable elements and the second loop disposed concentric to and nested within the first loop. In one embodiment, the method also may include controlling the density of loops at the periphery based a crossover assemblable element comprising one or more switches. The method further includes providing wireless power by the coil. 
     In some embodiments, the method includes retrieving an arrangement for interlocking the assemblable elements stored in a database. The method may also include selectively interlock the assemblable elements is based on the arrangement of the plurality of assemblable elements. In some embodiments, the arrangement is two-dimensional. In other embodiments, the arrangement is three-dimensional. 
     In some implementations, the method may also include forming one or more coils by electrically interconnecting the portions of coil of the assemblable elements. In some embodiments, either in combination or alternatively, the method also includes supplying power from a power source to the assemblable elements via one of the assemblable elements. 
     Another aspect of the present disclosure provide another device for distributing power. The device includes a first means for creating a charging coil, the first means including a first portion of the charging coil. The device also includes a second means for creating a charging coil, the second means including a second portion of the charging coil. The first means for creating a charging coil is configured to interlock to the second means for creating a charging coil, and the first and second portions of the charging coil are electrically interconnected and configured to provide wireless power based on the interlocking of the first and second means for creating a charging coil. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above-mentioned aspects, as well as other features, aspects, and advantages of the present technology will now be described in connection with various embodiments, with reference to the accompanying drawings. The illustrated embodiments, however, are merely examples and are not intended to be limiting. Throughout the drawings, similar symbols typically identify similar components, unless context dictates otherwise. Note that the relative dimensions of the following figures may not be drawn to scale. 
         FIG. 1  is a functional block diagram of a wireless power transfer system, in accordance with an exemplary embodiment. 
         FIG. 2  is a functional block diagram of a wireless power transfer system, in accordance with an exemplary embodiment. 
         FIG. 3  is a schematic diagram of a portion of transmit circuitry or receive circuitry of  FIG. 2  including a transmit or receive coil, in accordance with an exemplary embodiment. 
         FIG. 4  is a functional block diagram of a transmitter that can be used in the wireless power transfer system of  FIG. 1 , in accordance with an exemplary embodiment. 
         FIG. 5  is a functional block diagram of a receiver that can be used in the wireless power transfer system of  FIG. 1 , in accordance with an exemplary embodiment. 
         FIG. 6  is a schematic diagram of a portion of transmit circuitry that can be used in the transmitter of  FIG. 4 . 
         FIGS. 7A and 7B  are perspective views of a modular transmit area, in accordance with an exemplary embodiment. 
         FIG. 8  is a perspective view of the modular transmit area of  FIGS. 7A and 7B  including an exemplary embodiment of a transmit coil, in accordance with an exemplary embodiment. 
         FIG. 9  is a perspective view of the modular transmit area of  FIGS. 7A and 7B  including another exemplary embodiment of a transmit coil, in accordance with an exemplary embodiment. 
         FIGS. 10A and 10B  are perspective views of another modular transmit area, in accordance with an exemplary embodiment. 
         FIG. 11A  is perspective views of a modular transmit area, in accordance with another exemplary embodiment. 
         FIGS. 11B-11E  are perspective views of various assemblable elements, in accordance with an exemplary embodiment. 
         FIGS. 12A and 12B  are perspective views of another modular transmit area and another embodiment of assemblable elements, in accordance with an exemplary embodiment. 
         FIGS. 13A through 13D  are perspective views of a three-dimensional modular transmit area and three-dimensional assemblable elements, in accordance with an exemplary embodiment. 
         FIGS. 14A and 14B  are perspective views of a tubular modular transmit area including tubular assemblable elements, in accordance with an exemplary embodiment. 
         FIGS. 15A and 15B  are perspective views of another modular transmit area including hexagonal assemblable elements, in accordance with an exemplary embodiment. 
         FIG. 16  is perspective view of a three-dimensional modular transmit area including two-dimensional assemblable elements, in accordance with an exemplary embodiment. 
         FIG. 17  is perspective views of another modular transmit area having a dynamically modifiable transmit area, in accordance with an exemplary embodiment. 
         FIG. 18  is a flowchart of an exemplary method of wireless power transfer, in accordance with an exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, reference is made to the accompanying drawings, which form a part of the present disclosure. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the Figures, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and form part of this disclosure. 
     Wireless power transfer may refer to transferring any form of energy associated with electric fields, magnetic fields, electromagnetic fields, or otherwise from a transmitter to a receiver without the use of physical electrical conductors (e.g., power may be transferred through free space). The power output into a wireless field (e.g., a magnetic field or an electromagnetic field) may be received, captured by, or coupled by a “receive coil” to achieve power transfer. The term “coil” may also be referred to as an “antenna,” “loop antenna,” “resonator,” etc. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. It will be understood by those within the art that if a specific number of a claim element is intended, such intent will be explicitly recited in the claim, and in the absence of such recitation, no such intent is present. For example, as used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. It will be further understood that the terms “comprises,” “comprising,” “includes,” and “including,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. 
       FIG. 1  is a functional block diagram of a wireless power transfer system  100 , in accordance with one example implementation. An input power  102  may be provided to a transmitter  104  from a power source (not shown in this figure) to generate a wireless (e.g., magnetic or electromagnetic) field  105  for performing energy transfer. A receiver  108  may couple to the wireless field  105  and generate an output power  110  for storing or consumption by a device (not shown in this figure) coupled to the output power  110 . Both the transmitter  104  and the receiver  108  are separated by a distance  112 . 
     In one example implementation, the transmitter  104  and the receiver  108  are configured according to a mutual resonant relationship. When the resonant frequency of the receiver  108  and the resonant frequency of the transmitter  104  are substantially the same or very close, transmission losses between the transmitter  104  and the receiver  108  are minimal. As such, wireless power transfer may be provided over a larger distance in contrast to purely inductive solutions that may require large antenna coils which are very close (e.g., sometimes within millimeters). Resonant inductive coupling techniques may thus allow for improved efficiency and power transfer over various distances and with a variety of inductive coil configurations. 
     The receiver  108  may receive power when the receiver  108  is located in the wireless field  105  produced by the transmitter  104 . The wireless field  105  corresponds to a region where energy output by the transmitter  104  may be captured by the receiver  108 . The wireless field  105  may correspond to the “near-field” of the transmitter  104  as will be further described below. The transmitter  104  may include a transmit antenna or coil  114  for transmitting energy to the receiver  108 . The receiver  108  may include a receive antenna or coil  118  for receiving or capturing energy transmitted from the transmitter  104 . The near-field may correspond to a region in which there are strong reactive fields resulting from the currents and charges in the transmit coil  114  that minimally radiate power away from the transmit coil  114 . The near-field may correspond to a region that is within about one wavelength (or a fraction thereof) of the transmit coil  114 . 
     As described above, efficient energy transfer may occur by coupling a large portion of the energy in the wireless field  105  to the receive coil  118  rather than propagating most of the energy in an electromagnetic wave to the far field. When positioned within the wireless field  105 , a “coupling mode” may be developed between the transmit coil  114  and the receive coil  118 . The area around the transmit coil  114  and the receive coil  118  where this coupling may occur is referred to herein as a coupling-mode region. 
       FIG. 2  is a functional block diagram of a wireless power transfer system  200 , in accordance with another example implementation. The system  200  may be a wireless power transfer system of similar operation and functionality as the system  100  of  FIG. 1 . However, the system  200  provides additional details regarding the components of the wireless power transfer system  200  than  FIG. 1 . The system  200  includes a transmitter  204  and a receiver  208 . The transmitter  204  may include a transmit circuitry  206  that may include an oscillator  222 , a driver circuit  224 , and a filter and matching circuit  226 . The oscillator  222  may be configured to generate a signal at a desired frequency (e.g., a resonant frequency) that may be adjusted in response to a frequency control signal  223 . The oscillator  222  may provide the oscillator signal to the driver circuit  224 . The driver circuit  224  may be configured to drive the transmit coil  214  at, for example, a resonant frequency of the transmit coil  214  based on an input voltage signal (VD)  225 . The transmitter  204  can receive input voltage signal  225  through a number of power sources, such as, for example, an AC-DC converter (not shown) to convert conventional AC power present in a building, a DC-DC converter (not shown) to convert a conventional DC power source to a voltage suitable for the transmitter  204 , or directly from a conventional DC power source (not shown). In some embodiments, the driver circuit  224  may be a switching amplifier configured to receive a square wave from the oscillator  222  and output a sine wave. For example, the driver circuit  224  may be a class E amplifier. 
     The filter and matching circuit  226  may filter out harmonics or other unwanted frequencies and match the impedance of the transmitter  204  to the transmit coil  214 . As a result of driving the transmit coil  214 , the transmit coil  214  may generate a wireless field  205  to wirelessly output power at a level sufficient for charging a battery  236 , for example. 
     The receiver  208  may include a receive circuitry  210  that may include a matching circuit  232  and a rectifier circuit  234 . The matching circuit  232  may match the impedance of the receive circuitry  210  to a receive coil  218 . The rectifier circuit  234  may generate a direct current (DC) power output from an alternate current (AC) power input to charge the battery  236 , as shown in  FIG. 2 . The receiver  208  and the transmitter  204  may additionally communicate on a separate communication channel  219  (e.g., Bluetooth, Zigbee, cellular, etc.). The receiver  208  and the transmitter  204  may alternatively communicate via in-band signaling using characteristics of the wireless field  205 . 
     The receiver  208  may be configured to determine whether an amount of power transmitted by the transmitter  204  and received by the receiver  208  is appropriate for charging the battery  236 . Transmitter  204  may be configured to generate a predominantly non-radiative field with a direct field coupling coefficient (k) for providing energy transfer. Receiver  208  may directly couple to the wireless field  205  and may generate an output power for storing or consumption by a battery (or load)  236  coupled to the output or receive circuitry  210 . 
     As discussed above, both transmitter  204  and receiver  208  are separated by a distance and may be configured according to a mutual resonant relationship to minimize transmission losses between the transmitter  204  and the receiver  208 . When the transmit coil  214  and the receive coil  218  are mutually resonant and in close proximity, the wireless power transfer system  200  may be described as a strongly coupled regime where the coupling coefficient (coupling coefficient k) is typically above 0.3. In some embodiments, the coupling coefficient k between the transmitter  204  and receiver  208  may vary based on at least one of the distance between the two corresponding coils or the size of the corresponding coils, etc. 
       FIG. 3  is a schematic diagram of a portion of the transmit circuitry  206  or the receive circuitry  210  of  FIG. 2 , in accordance with some example implementations. As illustrated in  FIG. 3 , a transmit or receive circuitry  350  may include an coil  352 . The antenna  352  may also be referred to or be configured as a “loop” antenna  352  or a resonator. The coil  352  may also be referred to herein or be configured as a “magnetic” coil or an induction coil. The term “coil” generally refers to a component that may wirelessly output or receive energy for coupling to another “coil.” The coil may also be referred to as an antenna of a type that is configured to wirelessly output or receive power. As used herein, the coil  352  is an example of a “power transfer component” of a type that is configured to wirelessly output and/or receive power. 
     The coil  352  may include an air core or a physical core such as a ferrite core (not shown in this figure). Air core loop antennas may be more tolerable to extraneous physical devices placed in the vicinity of the core. Furthermore, an air core loop antenna  352  allows the placement of other components within the core area. In addition, an air core loop may more readily enable placement of the receive coil  218  ( FIG. 2 ) within a plane of the transmit coil  214  ( FIG. 2 ) where the coupled-mode region of the transmit coil  214  may be more powerful. For example, such that the receiver coil is partially or fully encompassed or surrounded by the transmit coil within the plane of the transmit coil, as will be described below in connection with  FIGS. 13A-16 . 
     As stated, efficient transfer of energy between the transmitter  104  (transmitter  204  as referenced in  FIG. 2 ) and the receiver  108  (receiver  208  as referenced in  FIG. 2 ) may occur during matched or nearly matched resonance between the transmitter  104  and the receiver  108 . However, even when resonance between the transmitter  104  and receiver  108  are not matched, energy may be transferred, although the efficiency may be affected. For example, the efficiency may be less when resonance is not matched. Transfer of energy occurs by coupling energy from the wireless field  105  (wireless field  205  as referenced in  FIG. 2 ) of the transmit coil  114  (transmit coil  214  as referenced in  FIG. 2 ) to the receive coil  118  (receive coil  218  as referenced in  FIG. 2 ), residing in the vicinity of the wireless field  105 , rather than propagating the energy from the transmit coil  114  into free space. 
     The resonant frequency of the loop or magnetic coils is based on the inductance and capacitance. Inductance may be simply the inductance created by the coil  352 , whereas, capacitance may be added to the coil&#39;s inductance to create a resonant structure at a desired resonant frequency. As a non-limiting example, a capacitor  354  and a capacitor  356  may be added to the transmit or a receive circuitry  350  to create a resonant circuit that selects a signal  358  at a resonant frequency. Accordingly, for larger diameter coils, the size of capacitance needed to sustain resonance may decrease as the diameter or inductance of the loop increases. 
     Furthermore, as the diameter of the coil increases, the efficient energy transfer area of the near-field may increase. Other resonant circuits formed using other components are also possible. As another non-limiting example, a capacitor may be placed in parallel between the two terminals of the circuitry  350 . For transmit coils, the signal  358 , with a frequency that substantially corresponds to the resonant frequency of the coil  352 , may be an input to the coil  352 . 
     In  FIG. 1 , the transmitter  104  may output a time varying magnetic (or electromagnetic) field with a frequency corresponding to the resonant frequency of the transmit coil  114 . When the receiver  108  is within the wireless field  105 , the time varying magnetic (or electromagnetic) field may induce a current in the receive coil  118 . As described above, if the receive coil  118  is configured to resonate at the frequency of the transmit coil  114 , energy may be efficiently transferred. The AC signal induced in the receive coil  118  may be rectified as described above to produce a DC signal that may be provided to charge or to power a load. 
       FIG. 4  is a functional block diagram of a transmitter  404  that can be used in the wireless power transfer system of  FIG. 1 , in accordance with exemplary embodiments of the present disclosure. The transmitter  404  can include transmit circuitry  406  and a transmit coil  414 . The transmit coil  414  can be the coil  352  as shown in  FIG. 3 . Transmit circuitry  406  can provide RF power to the transmit coil  414  by providing an oscillating signal resulting in generation of energy (e.g., magnetic flux) about the transmit coil  414 . Transmitter  404  can operate at any suitable frequency. By way of example, transmitter  404  can operate at the 13.56 MHz ISM band. 
     The transmit circuitry  406  can include a fixed impedance matching circuit  409  for presenting a load to the driver circuit  424  such that the efficiency of power transfer from DC to AC is increased or maximized. The transmit circuitry  406  can further include a low pass filter (LPF)  408  configured to reduce harmonic emissions to levels to prevent self-jamming of devices coupled to receivers  108  ( FIG. 1 ). Other exemplary embodiments can include different filter topologies, including but not limited to, notch filters that attenuate specific frequencies while passing others and can include an adaptive impedance match, that can be varied based on measurable transmit metrics, such as output power to the transmit coil  414  or DC current drawn by the driver circuit  424 . Transmit circuitry  406  further includes a driver circuit  424  configured to drive an RF signal as determined by an oscillator  423 . The transmit circuitry  406  can be comprised of discrete devices or circuits, or alternately, can be comprised of an integrated assembly. An exemplary RF power output from transmit coil  414  can be around 1 Watt-10 Watts, such as around 2.5 Watts. 
     Transmit circuitry  406  can further include a controller  415  for selectively enabling the oscillator  423  during transmit phases (or duty cycles) for specific receivers, for adjusting the frequency or phase of the oscillator  423 , and for adjusting the output power level for implementing a communication protocol for interacting with neighboring devices through their attached receivers. It is noted that the controller  415  can also be referred to herein as a processor  415 . Adjustment of oscillator phase and related circuitry in the transmission path can allow for reduction of out of band emissions, especially when transitioning from one frequency to another. 
     The transmit circuitry  406  can further include a load sensing circuit  416  for detecting the presence or absence of active receivers in the vicinity of the near-field generated by transmit coil  414 . By way of example, the load sensing circuit  416  monitors the current flowing to the driver circuit  424 , that can be affected by the presence or absence of active receivers in the vicinity of the field generated by transmit coil  414  as will be further described below. Detection of changes to the loading on the driver circuit  424  are monitored by controller  415  for use in determining whether to enable the oscillator  423  for transmitting energy and to communicate with an active receiver. As described more fully below, a current measured at the driver circuit  424  can be used to determine whether a receiving device is positioned within a wireless power transfer region of the transmitter  404 . 
     The transmit coil  414  can be implemented with a Litz wire or as an antenna strip with the thickness, width and metal type selected to keep resistive losses low. In one embodiment, the transmit coil  414  can generally be configured for association with a larger structure such as a table, mat, lamp or other less portable configuration. Accordingly, the transmit coil  414  generally may not need “turns” in order to be of a practical dimension. An exemplary embodiment of a transmit coil  414  can be “electrically small” (i.e., fraction of the wavelength) and tuned to resonate at lower usable frequencies by using capacitors to define the resonant frequency. 
     The transmitter  404  can gather and track information about the whereabouts and status of receiver devices that can be associated with the transmitter  404 . Thus, the transmit circuitry  406  can include a presence detector  480 , an enclosed detector  460 , or a combination thereof, connected to the controller  415  (also referred to as a processor herein). The controller  415  can adjust an amount of power delivered by the driver circuit  424  in response to presence signals from the presence detector  480  and the enclosed detector  460 . The transmitter  404  can receive power through a number of power sources, such as, for example, an AC-DC converter (not shown) to convert conventional AC power present in a building, a DC-DC converter (not shown) to convert a conventional DC power source to a voltage suitable for the transmitter  404 , or directly from a conventional DC power source (not shown). 
     As a non-limiting example, the presence detector  480  can be a motion detector utilized to sense the initial presence of a device to be charged that is inserted into the coverage area of the transmitter  404 . After detection, the transmitter  404  can be turned on and the RF power received by the device can be used to toggle a switch on the receive device in a pre-determined manner, which in turn results in changes to the driving point impedance of the transmitter  404 . 
     As a non-limiting example, the enclosed detector  460  (can also be referred to herein as an enclosed compartment detector or an enclosed space detector) can be a device such as a sense switch for determining when an enclosure is in a closed or open state. When a transmitter is in an enclosure that is in an enclosed state, a power level of the transmitter can be increased. 
     In exemplary embodiments, a method by which the transmitter  404  does not remain on indefinitely can be used. In this case, the transmitter  404  can be programmed to shut off after a user-determined amount of time. This feature prevents the transmitter  404 , notably the driver circuit  424 , from running long after the wireless devices in its perimeter area fully charged and/or no longer present in the wireless field. This event can be due to the failure of the circuit to detect the signal sent from either the repeater or the receive coil that a device is fully charged. To prevent the transmitter  404  from automatically shutting down if another device is placed in its perimeter, the transmitter  404  automatic shut off feature can be activated only after a set period of lack of motion detected in its perimeter. The user can be able to determine the inactivity time interval and change it as desired. As a non-limiting example, the time interval can be longer than that needed to fully charge a specific type of wireless device under the assumption of the device being initially fully discharged. 
       FIG. 5  is a functional block diagram of a receiver  508  that can be used in the wireless power transfer system of  FIG. 1 , in accordance with exemplary embodiments of the present disclosure. The receiver  508  includes receive circuitry  510  that can include a receive coil  518 . Receiver  508  further couples to device  550  for providing received power thereto. It should be noted that receiver  508  is illustrated as being external to device  550  but can be integrated into device  550 . Energy can be propagated wirelessly to receive coil  518  and then coupled through the rest of the receive circuitry  510  to device  550 . By way of example, the charging device can include devices such as mobile phones, portable music players, laptop computers, tablet computers, computer peripheral devices, communication devices (e.g., Bluetooth devices), digital cameras, hearing aids (and other medical devices), and the like. 
     Receive coil  518  can be tuned to resonate at the same frequency, or within a specified range of frequencies, as transmit coil  414  ( FIG. 4 ). Receive coil  518  can be similarly dimensioned with transmit coil  414  or can be differently sized based upon the dimensions of the associated device  550 . By way of example, device  550  can be a portable electronic device having diametric or length dimension smaller than the diameter or length of transmit coil  414 . In such an example, receive coil  518  can be implemented as a multi-turn coil in order to reduce the capacitance value of a tuning capacitor (not shown) and increase the receive coil&#39;s impedance. By way of example, receive coil  518  can be placed around the substantial circumference of device  550  in order to maximize the coil diameter and reduce the number of loop turns (e.g., windings) of the receive coil  518  and the inter-winding capacitance. 
     Receive circuitry  510  can provide an impedance match to the receive coil  518 . Receive circuitry  510  includes power conversion circuitry  506  for converting a received RF energy source into charging power for use by the device  550 . Power conversion circuitry  506  includes an RF-to-DC converter  520  and can also in include a DC-to-DC converter  522 . RF-to-DC converter  520  rectifies the RF energy signal received at receive coil  518  into a non-alternating power with an output voltage represented by Vrect. The DC-to-DC converter  522  (or other power regulator) converts the rectified RF energy signal into an energy potential (e.g., voltage) that is compatible with device  550  with an output voltage and output current represented by Vout and Iout. Various RF-to-DC converters are contemplated, including partial and full rectifiers, regulators, bridges, doublers, as well as linear and switching converters. 
     Receive circuitry  510  can further include switching circuitry  512  for connecting receive coil  518  to the power conversion circuitry  506  or alternatively for disconnecting the power conversion circuitry  506 . Disconnecting receive coil  518  from power conversion circuitry  506  not only suspends charging of device  550 , but also changes the “load” as “seen” by the transmitter  404  ( FIG. 2 ). 
     As disclosed above, transmitter  404  includes load sensing circuit  416  that can detect fluctuations in the bias current provided to transmitter driver circuit  424 . Accordingly, transmitter  404  has a mechanism for determining when receivers are present in the transmitter&#39;s near-field. 
     In some embodiments, a receiver  508  can be cloaked in order to eliminate coupling to other nearby receivers or to reduce loading on nearby transmitters. This “unloading” of a receiver is also known herein as a “cloaking.” Furthermore, this switching between unloading and loading controlled by receiver  508  and detected by transmitter  404  can provide a communication mechanism from receiver  508  to transmitter  404  as is explained more fully below. Additionally, a protocol can be associated with the switching that enables the sending of a message from receiver  508  to transmitter  404 . By way of example, a switching speed can be on the order of 100 μsec. 
     In an exemplary embodiment, communication between the transmitter  404  and the receiver  508  refers to a device sensing and charging control mechanism, rather than conventional two-way communication (i.e., in band signaling using the coupling field). In other words, the transmitter  404  can use on/off keying of the transmitted signal to adjust whether energy is available in the near-field. The receiver can interpret these changes in energy as a message from the transmitter  404 . From the receiver side, the receiver  508  can use tuning and de-tuning of the receive coil  518  to adjust how much power is being accepted from the field. In some cases, the tuning and de-tuning can be accomplished via the switching circuitry  512 . The transmitter  404  can detect this difference in power used from the field and interpret these changes as a message from the receiver  508 . It is noted that other forms of modulation of the transmit power and the load behavior can be utilized. 
     Receive circuitry  510  can further include signaling detector and beacon circuitry  514  used to identify received energy fluctuations, that can correspond to informational signaling from the transmitter to the receiver. Furthermore, signaling and beacon circuitry  514  can also be used to detect the transmission of a reduced RF signal energy (e.g., a beacon signal) and to rectify the reduced RF signal energy into a nominal power for awakening either un-powered or power-depleted circuits within receive circuitry  510  in order to configure receive circuitry  510  for wireless charging. 
     Receive circuitry  510  further includes processor  516  for coordinating the processes of receiver  508  described herein including the control of switching circuitry  512  described herein. Cloaking of receiver  508  can also occur upon the occurrence of other events including detection of an external wired charging source (e.g., wall/USB power) providing charging power to device  550 . Processor  516 , in addition to controlling the cloaking of the receiver, can also monitor signaling detector and beacon circuitry  514  to determine a beacon state and extract messages sent from the transmitter  404 . Processor  516  can also adjust the DC-to-DC converter  522  for improved performance. 
       FIG. 6  is a schematic diagram of a portion of transmit circuitry  600  that can be used in the transmit circuitry  406  of  FIG. 4 . The transmit circuitry  600  can include a driver circuit  624  as described above in  FIG. 4 . As described above, the driver circuit  624  can be a switching amplifier that can be configured to receive a square wave and output a sine wave to be provided to the transmit circuit  650 . In some cases, the driver circuit  624  can be referred to as an amplifier circuit. The driver circuit  624  is shown as a class E amplifier; however, any suitable driver circuit  624  can be used in accordance with embodiments of the present disclosure. The driver circuit  624  can be driven by an input signal  602  from an oscillator  423  as shown in  FIG. 4 . The driver circuit  624  can also be provided with a drive voltage VD that is configured to control the maximum power that can be delivered through a transmit circuit  650 . To eliminate or reduce harmonics, the transmit circuitry  600  can include a filter circuit  626 . In some embodiments, the filter circuit  626  can be a three pole (capacitor  634 , inductor  632 , and capacitor  636 ) low pass filter circuit  626 . 
     The signal output by the filter circuit  626  can be provided to a transmit circuit  650  comprising a coil  614 . The transmit circuit  650  can include a series resonant circuit having a capacitance  620  and inductance that can resonate at a frequency of the filtered signal provided by the driver circuit  624 . In various embodiments, the coil or an additional capacitor component can create the inductance or capacitance. The load of the transmit circuit  650  can be represented by the variable resistor  622 . The load can be a function of a wireless power receiver  508  that is positioned to receive power from the transmit circuit  650 . 
     In various embodiments, the efficiency of power transfer of a wireless power transfer system is proportional to how closely the transmit coil and receive coil can be aligned with one another. For example, how closely the wireless field radiating from the transmitter can be aligned with the receive coil of a receiver. Typically, a transmitter, including a transmit coil, and a receiver, including a receiver coil, are aligned by a user of the wireless power transfer system such that the receive coil is positioned within the wireless field produced by the transmit coil (e.g., the coupling mode). Conventionally, transmitters are fixed in size, and as such the transmit coils are capable of charging only one predetermined receiver size or a single range of receiver sizes. 
     Various embodiments disclosed herein relate to dynamic or modular transmit areas comprising one or more coils for use with wireless power transfer systems. Some embodiments disclosed herein relate to foldable transmit areas. Other embodiments, disclosed herein relate to assemblable transmit areas for use with wireless power transfer systems. For example, a plurality of assemblable transmit areas or elements, containing at least a portion of a coil therein, may be configured to interlock into various shapes and sizes. In various embodiments, the interlocking of the plurality of assemblable elements electrically interconnects the portions of the coil to provide wireless power transfer. In some embodiments, the assemblable elements may be interconnected or assembled into a two-dimensional shape, while in other embodiments, the shape may be three-dimensional. Other embodiments disclosed herein relate to methods for configuring transmit coils within and among the modular or assemblable elements, either in a specific or a random arrangement. For, example a transmit area may comprise multiple portions of a coil that may be configured into a plurality of coils for generating a wireless field, each coil may be dynamically reconfigurable (e.g., switched and reshaped) due to the multiple portions and based on the power receiving requirements of the receiver. As such, embodiments disclosed herein describe wireless power transfer systems that are modular and assemblable, for example, to provide flexibility in charging various sizes or shapes of receivers or to assist with storage. Such embodiments may be expanded or assembled to provide a variety of transmit areas that are capable of providing efficient wireless power transfer. 
     As used herein and throughout this disclosure, the term “assemblable elements” may refer to one or more transmitters, for example, such as transmitters  204  and/or  404  of  FIGS. 2 and 4 , respectively. In some embodiments, the assemblable elements may be a circuit board comprising a printed circuit board (PCB) containing the coil and other transmit circuitry of each assemblable elements. In some embodiments, an assemblable element may be a transmitter  204  or  404  comprising all the transmit circuitry described in connection with  FIGS. 1-6 . In other embodiments, the assemblable element may comprise some or none of the transmit circuitry described in connection with  FIGS. 1-6 . For example, an assemblable element may comprise a transmit coil  214  and a power amplifier such as drive circuit  224  or  424 . Accordingly, the assemblable element may include various communication or synchronization lines, configured to exchange control signal from one or more controllers (e.g., controller  415  of  FIG. 4 ). For example, a transmit area may comprise multiple assemblable elements where one assemblable element includes a controller. The controller may be configured to send control signals over a synchronization line to adjust frequency and phase of oscillators (e.g., oscillator  423  of  FIG. 4 ) included in the other assemblable elements. Other configurations are possible, as described herein. 
     In some implementations, a wireless power transfer system is provided for distributing power that may be foldable or modular. For example, the wireless power transfer system may include a transmit area comprising a plurality of rigid segments arranged in a first arrangement. The plurality of rigid segments may be connected by a plurality of hinges disposed between the plurality of rigid segments. The plurality of hinges may be configured to permit the rigid segments be arranged into a second arrangement (e.g., folded into various configurations, assembled or dissembled, etc.). In some embodiments, at least one coil configured to provide wireless power is disposed in at least one of the plurality of rigid segments. In some embodiments, the coil is a single coil having multiple turns that is disposed amongst the plurality of rigid segments and the plurality of hinges. In another embodiment, the coil comprises a plurality of individual coils or portions of a coil, where each of the plurality of coils is disposed in one of the rigid segments. 
       FIGS. 7A and 7B  are perspective views of an exemplary transmit area  700  in accordance with an exemplary embodiment.  FIG. 7A  illustrates transmit area  700 , including multiple rigid segments  710  configured in an expanded arrangement.  FIG. 7A  also illustrates multiple connection segments  720  disposed between the multiple rigid segments  710 .  FIG. 7B  illustrates a second arrangement of the multiple rigid segments  710  facilitated by use of the connection segments  720 . For example, as illustrated in  FIG. 7B , the second arrangement is a compact folded or stacked arrangement, where the expanded arrangement of  FIG. 7A  may be unfolded into a larger area suitable for charging several devices. 
     In some embodiments, the rigid segments  710  may be similar to assemblable elements of the transmit area, as described above and throughout this disclosure. For example, rigid segments  710  may be constructed a circuit board comprising a printed circuit board (PCB) containing the coil and other transmit for generating a wireless field for wireless power transfer. In some embodiments, rigid segments may collectively comprise a transmitter  204  or  404  including all the transmit circuitry described in connection with  FIGS. 1-6 . In other embodiments, rigid segments  710  may individually comprise a transmitter  204  and/or  404 . In other embodiments, the assemblable element may comprise some or none of the transmit circuitry described in connection with  FIGS. 1-6 . 
     In some embodiments, the transmit area  700  may be configured as a wireless power transfer system, as described above with respect to  FIGS. 1-6 , that may have multiple arrangements for wirelessly transferring power, storage, and/or compact mobility. The transmit area  700  may include a power input line  730  configured to provide input power to transmit area  700  from a power source (not shown) to generate a wireless field for performing energy transfer. 
     In some embodiments, switching between a first and second arrangement may be facilitated by the connection segments  720 . In some embodiments, the connection segments facilitate switching between the first and second arrangements illustrated in  FIGS. 7A and 7B . For example, connection segments  720  may be flexible material configured to bend or fold, such that transmit area  700  may be switched between a stacked or folded arrangement (as shown in  FIG. 7B ) and an expanded or planar arrangement (as shown in  FIG. 7A ). For example, connection segments  720  may be a thin flexible PCB that may be bent or rolled up. Portions of the transmit coil, included in the transmit area  700 , may be made of wires capable of bending without breaking the electrical connection. In other embodiments, connection segments  720  may be rigid hinges similar to a hinge of a doorway, which facilitates the switching between the first and second arrangements. In the above embodiments, the wireless power transfer system may be configured to operate in either the first or second arrangement. For example, the transmit area  700  may be configured to generate a wireless field for performing energy transfer in the folded state of  FIG. 7B  or unfolded state of  FIG. 7A  based on the wireless power transfer requirements of the receiver. 
       FIGS. 8 and 9  are perspective views of exemplary embodiment transmit coils included in transmit areas  800  and  900 , respectively. The transmit areas  800  and  900  may be substantially similar to transmit area  700  of  FIGS. 7A and 7B , however, the configuration of the rigid segments and transmit coils therein are different. 
     For example,  FIG. 8  illustrates an embodiment of transmit area  800  including one or more transmit coils  814  constructed between and throughout the multiple rigid segments  810  and connection segments  820 . The various components, aside from coil  814 , of a wireless power transfer system described above in  FIGS. 1-6  may be included in one or more rigid segments  810 . For example, while transmit coil  814  is dispersed among the various rigid segments  810  and connection segments  820 , the transmit circuitry (e.g., oscillator  222 , a driver circuit  224 , and a filter and matching circuit  226  of  FIG. 2 ) may be included in a single rigid segment  810  or dispersed among the rigid segments  810 . The transmit area  800  may also include electrical connections  802  connected to the positive and negative terminals of a power source (not shown) configured to provide input power to transmit area  800  to generate a wireless field for performing energy transfer. 
     In another embodiment depicted in  FIG. 9 , each rigid segment  910   a - c  may include a separate transmit coil  914   a - c . In some variations, each transmit coil  914   a - c  may be connected in parallel through connection lines  925 , as described below in  FIG. 9 . In some embodiments, connection lines  925  may be embedded in connection segment  920 . In other variations, each transmit coil  914   a - c  may be connected in series with each other (not shown). In some embodiments, each rigid segment  910   a - c  may be a single wireless power transfer system including the various components described above with reference to  FIGS. 1-6 . In other embodiments, one or more rigid segments  910   a - c  may include one or more of the various comments described above with reference to  FIGS. 1-6 . For example, rigid segment  910   b  may be a master rigid segment that is similar to the transmitters  204  or  404  of  FIGS. 2 and 4 , respectively. The transmit area  900  may also include electrical connections  902  connected to the positive and negative terminals of a power source (not shown) configured to provide input power to transmit area  900  to generate a wireless field for performing energy transfer. 
     While the embodiments described illustrate transmit areas having a rectangular shape that may be stacked or folded as described above, it will be understood that any arrangement is possible based on the wireless power transfer requirements, as described above, of the receiver. For example,  FIGS. 10A and 10B  depict a perspective view of another embodiment of a wireless power transfer system having a first and second arrangement. In this embodiment, transmit area  1000  may comprise a coil compacted about pivot point  1022 .  FIG. 10A  illustrates the embodiment in a first arrangement, for example, a folded or compacted state.  FIG. 10B  illustrates the embodiment in a second arrangement, for example, an unfolded or expanded state. As described above, transmit area  1000  may include a single coil throughout and among the rigid segments  1010  or comprise multiple coils contained within each rigid segment  1010 . In some embodiments, the rigid segments  1010  may have connection segments or edges  1020  comprising interlocking elements  1025 . Interlocking elements  1025  may be any means of mechanically connecting two adjacent rigid segments  1010 , such that the adjacent rigid segments do not move relative to each other. Some example interlocking elements may include magnets, latches, snaps, zippers. Velcro®, male/female connection section (e.g., similar to a puzzle piece), etc. Other interlocking elements are possible. 
     In some embodiments, a modular wireless power transfer system may comprise a plurality of assemblable elements configured to be interlocked to form wireless power transfer system. In some embodiments, assemblable elements can be re-used and re-assembled into various shapes and sizes, thereby permitting differently shaped wireless power systems from a collection of assemblable elements. In some embodiments, the modular wireless power transfer system may include a dynamically reconfigurable transmit coil made of the assemblable elements. 
       FIG. 11A  is a schematic perspective view of an exemplary transmit area  1100  in accordance with an exemplary embodiment. Transmit area  1100  may be a transmitter or may be part of a transmitter of wireless power transfer system  100  of  FIG. 1 , the transmit area  1100  being configured to generate a wireless field for providing energy transfer to a receiver. The transmit area  700  may comprise a plurality of assemblable elements  1110   a - e . Each assemblable element  1110   a - e  can be configured to interlock to one or more neighboring assemblable elements  1110   a - e  via an interlocking element (not shown). For example, the assemblable elements  1110  may be interconnected in a manner similar to Legos®, puzzle pieces (e.g., as shown in  FIGS. 12A and 12B ), or any interlocking device as described above, such that the plurality of assemblable elements  1110  connected to create a single transmit area  1100 . In other embodiments, the assemblable elements may include male and female connection portions that mate to connect the assemblable elements  1110 . In some embodiments, the edges  1120  of the assemblable elements  1110  may be constructed so that each piece may be fit together or interconnect with neighboring assemblable elements through compatible connections, both mechanical and electrical, such that power and electrical signals may be passed between each tile. 
     In some embodiments, the assemblable elements  1110  may be tiles (as illustrated in  FIG. 11A-11E ), however it will be understood that the concepts and embodiments disclosed herein are not to be limited as such. For example, the assemblable elements  1110  may be blocks (as illustrated in  FIG. 13A-13D ). Assemblable elements  1110  can be of various geometries (e.g., square, hexagonal, pentagonal, circular, etc.), allowing a wide variety of configurations. Furthermore, the assemblable elements  1110  may be two-dimensional with minimal thickness or three-dimensional (e.g., a block or cube, pyramid, tetrahedron, dodecahedron, etc.) such that the assemblable elements may be assembled into various shapes (e.g., 2D or 3D), sizes, and arrangements. For example, charging elements may be interconnected to form a flat continuous surface using square or hexagonal blocks, a bowl shape using hexagonal and pentagonal blocks together as illustrated in  FIGS. 15A-16 , etc. One non-limiting advantage of the different shapes or arrangements of assemblable elements allows for a plurality of arrangements of transmit area  1100  to optimally and efficiently charge differently shaped devices, space constraints with the location of the transmit area within a user&#39;s personal space, and personal aesthetics of a user. For example, a desk or table may be constructed out of assemblable elements to allow such a structure to support wireless charging. Other configurations are possible, such that the assemblable elements  1110  may be interlocked with one or more neighboring assemblable elements  1110  to form single transmit area  1100  from the plurality of assemblable elements  1110 . 
     Each assemblable element  1110  includes at least a portion of the coil  1114 . Each assemblable element  1110  may include a portion of a coil or transmit coil  1114   a - d . In various embodiments, when the assemblable elements  1110  are interlocked, the plurality of portions of the coil  1114  may be electrically interconnected. For example, the coil may comprise wires or conductors and the transmit circuitry as described above in  FIGS. 1-6  can be brought into contact to facilitate the exchange of electrical signals amongst the portions of the coil  1114 . By applying input power via power input  1102  connected to a power source, and in accordance with the description above in connection with  FIGS. 1-6 , the plurality of portions form one or more transmit coils configured to generate a wireless field to provide energy transfer. In some embodiments, a single assemblable element  1110  may comprise a transmit coil capable of generating a wireless field on its own. 
       FIGS. 11B-11E  illustrate various embodiments of assemblable elements  1110 , that may be assembled in various configuration to form a transmit area  1100  of  FIG. 11A . As described above, assemblable elements  1110   a - d  may include a portion of transmit coil  1114 , where each portion of transmit coil  1114  is illustrated as transmit coil portion  1114   a - d . In some embodiments, each assemblable element  1110   a - d  may comprise some, all, or none of the transmit circuitry of  FIGS. 1-6 . For example, each assemblable element may include only a portion of a coil. Or each assemblable element may be a complete transmitter (e.g., transmitter  204  or  404  of  FIGS. 2 and 4  respectively). The transmit coil portions  1114   a - e  may be arranged via interlocking components (not shown) disposed relative to connecting edge  1120   a - c  to form a complete transmit coil  1114  as shown in  FIG. 11A . The interlocking components, as described above, may be a mechanical means to connect the tiles together (e.g., magnets, latches, snaps, etc.).  FIGS. 11A-11E  are schematic illustrations of some embodiments of assemblable elements, however the descriptions of features or aspects throughout the present disclosure are to be considered applicable for similar features or aspects in any of the various embodiment described in the present disclosure. 
       FIG. 11B  illustrates a schematic perspective view of an embodiment of a turn assemblable element  1110   a  in accordance with an exemplary embodiment. Turn assemblable element  1110   a  comprises at least a portion of transmit coil  1114 , for example turn coil portion  1114   a . Turn assemblable element  1110   a  may also comprise interlocking edges  1120   a  which may comprise interlocking components  1125   a  (shown schematically) configured to facilitate interlocking of the plurality of assemblable elements. Turn coil portion  1114   a  may comprise wires, conductors, or other elements (e.g., conductors  1115   a ) configured to conduct or transmit an electrical circuit. The conductors  1115   a  may include an interconnection region, whereby the conductors of turn coil portion  1114   a  may be electrically interconnected to form a coil between the plurality of assemblable elements. For example, turn assemblable element  1110   a  may provide a turn or corner portion of the transmit coil  1114  of  FIG. 11A . The curve of the conductors of the turn coil portion  1114   a  may be 90° turn, as illustrated in  FIG. 11B . However, the turn may be any degree of turn as desired by the sought after arrangement for the transmit coil, for example, 5°, 10°, 50°, etc. 
       FIG. 11C  illustrates a schematic perspective view of an embodiment of a straight assemblable element  1110   b  in accordance with an exemplary embodiment. Straight assemblable element  1110   b  comprises at least a portion of transmit coil  1114 , for example straight coil portion  1114   b . Straight assemblable element  1110   b  may also comprise interlocking edges  1120   b , which may comprise interlocking components  1125   b  (shown schematically) configured to facilitate interlocking of the plurality of assemblable elements. Straight coil portion  1114   b  may also comprise conductors  1115   b  or other elements configured to transmit an electrical circuit. The conductors  1115   b  may include an interconnection region, whereby the straight coil portion  1114   b  may be electrically interconnected to form a coil between the plurality of assemblable elements. 
       FIG. 11D  illustrates a schematic perspective view of an embodiment of power assemblable element  1110   c  in accordance with an exemplary embodiment. Power assemblable element  1110   c  comprises at least a portion of transmit coil  1114 , for example power coil portion  1102  connected to a power source, such as for example, a DC to AC inverter. Power assemblable element  1110   c  may also comprise other coil portions, for example a cross over coil portion  1114   c  as depicted in  FIG. 11C . However, the power assemblable element  1110   c  may also comprise a straight coil portion or a turn coil portion. In some embodiments, the power assemblable element  1110   c  may also include a cross-over coil portion such that that the outermost loop is not shorted. Power coil portion  1102  may be a power-in line configured to electrically connect to a power amplifier (e.g., power amplifier  424  of  FIG. 4 ) either as part of power assemblable element  1110   c  or separate. In another embodiment, the power amplifier may be included in power assemblable element  1110   c . Power assemblable element  1110   c  may also comprise interlocking edges  1120   c  which may comprise interlocking components  1125   c  (shown schematically) configured to facilitate interlocking of the plurality of assemblable elements. Power assemblable element  1110   c  may also comprise conductors  1115   c  or other elements configured to transmit an electrical circuit. The conductors  1115   c  may include an interconnection region, whereby the power assemblable element  1110   c  may be electrically interconnected to form a coil between the plurality of assemblable elements. 
       FIG. 11E  illustrates a schematic perspective view of an embodiment of cross-over assemblable element  1110   d  in accordance with an exemplary embodiment. Cross-over assemblable element  1110   d  comprises at least a portion of transmit coil  1114 , for example cross-over coil portion  1114   d . Cross-over coil portion  1114   d  may be configured to provide a cross-over between loops of the transmit coil  1114 . Cross-over assemblable element  1110   d  may also comprise interlocking edges  1120   d  which may comprise interlocking components  1125   d  (shown schematically) configured to facilitate interlocking of the plurality of assemblable elements. Cross-over coil portion  1114   d  may also comprise conductors  1115   d  or other elements configured to transmit an electrical circuit. The conductors  1115   d  may include an interconnection region, whereby the cross-over coil portion  1114   d  may be electrically interconnected to form a coil between the plurality of assemblable elements. 
     In some embodiments, the cross-over coil portion  1114   d  may include a plurality of switches  1117  configured to control cross-over of the coil portion  1114 .  FIG. 11C  illustrates six switches  1117 , one for each conductor  1115   d , however, it will be understood that the number of switches  1117  need not be related to the number of conductors  1115   d . For example, cross-over assemblable element  1110   d  may include a straight coil portion and/or a curved coil portion. Accordingly, cross-over assemblable element  1110   d  may be one means for dynamically reconfiguring the transmit coil based on the power transfer requirements of the receiver. For example, one or more switches  1117  of cross-over assemblable element  1110   d  may be operated to form one or more loops within the coil portion  1114 . In some embodiments, the switches  1117  may be operated to form one or more transmit coils  1114  having one or more loops comprising one or more parallel turns. For example, a single transmit coil  1114  may contain a multiple loops where the turns for each loop are parallel. In another embodiment, in the alternative or in combination, switches  1117  may be configured to form passive parasitic loops that are not electrically connected to the other loops or the transmit circuitry. 
     In some implementations, the cross-over assemblable element  1110   d  may be configured to permit control over the turn density of the transmit coil  1114 . In some embodiments, where one or more cross-over assemblable elements  1110   d  comprising one or more switches  1117  are used in a transmit area  1100  of  FIG. 11A , switches  1117  may be configured to connect and disconnect one or more conductors  1115 . For example, as described above in connection with  FIGS. 1-6 , the uniformity of a wireless field generated by the transmitter of a wireless power system is related to the turn density of the coil. In some implementations, turn density is increased near the outer edge of a transmitter to improve field uniformity. 
     Accordingly, with reference to  FIG. 11A , a transmit area  1110  may comprise an outer region  1130  positioned near the outer edge of transmit area  1110 . The transmit area  1110  may also comprise an inner region  1140  located near the center of the transmit area  1110 . The transmit coil  1114  may be distributed throughout the inner and outer regions  1130  and  1140 . For example, a first grouping of loops of transmit coil  1114  may constitute a first region  1130 . This first grouping or subset of loops may have a loop density is related to the number of loops therein. Similarly, the inner region  1140  may comprise a second grouping or subset of loops of transmit coil  1114  having a second loop density. While  FIG. 11A  illustrates a select number of loops constituting a first or second region  1130  and  1140 , it will be understood that the number of loops therein is not so restricted. The number of loops illustrated in  FIG. 11A  is for illustration purposes only, and may be greater or fewer as required to achieve the desired wireless field uniformity and power transfer efficiency. 
     A cross-over assemblable element  1110   d  may be included in the transmitter  1100  of  FIG. 11A . Switches  1117  included in cross-over assemblable element  1110   d  may be configured to control the loop density of the first and second regions  1130  and  1140 . For example, switches  1117  may disconnect and connect the various conductors  1115  of the portions of the transmit coil  1114 . In some embodiments, the switches  1117  may be controlled to increase the number of loops making up the first grouping of loops. For example, transmit coil  1114  may have a plurality of conductors in the first region  1130 , some of which may be active while others are inactive (e.g., the conductors making a loop are not electrically connected to the active regions of the transmit coil  1114 ). The switches  1117  may be configured to then connect the inactive conductors as to include the inactive loops in the active regions, thereby increasing the number of loops in the first region  1130 . The loop density of the second region  1140  may be similarly controlled. Thus, the switches may be configured to periodically skip the one or more loops of the second region  1140 . In this way, the loop density of the first region  1130  may be altered relative to the density of the second region  1140 , thus the uniformity of the wireless field may be maintained. 
     In some implementations, switches  1117  may be controlled by a controller (not shown) similar to controller  415  of  FIG. 4 . As will be described below, the controller may be disposed in one or more assemblable elements, for example, in the cross-over assemblable element  1110   d  comprising the switches  1117 , in a master assemblable element configured to control the operation of the transmit area  1100 , or in any other assemblable element in electrical communication with the switches  1117 . The controller may be configured to send a control signal to the cross-over assemblable element  1110   d  configured to cause one or more switches to complete a circuit or deactivate a current circuit. Accordingly, the switches  1117  may be electrically controlled or mechanically controlled. 
     In some embodiments, the arrangement of assemblable elements  1110   a - d  may be determined by the user. In other embodiments, the arrangement of assemblable elements  1110   a - d  may be determined based on energy transfer requirements of the receiver. For example, some arrangements may be less suitable for efficiently transferring power to a given receiver, e.g., the generated wireless field is not efficiently coupled to the receiver coil or is not uniform across the receive coil. In some embodiments, the arrangement of the assemblable elements  1110   a - d  may be found on a look up table, where the arrangement is defined based on the requirements of a receiver. In some embodiments, the look up table may be stored in a database included in either the transmitter or an external or remote storage circuit. For example, in a case where the transmit area  1110  is configured to charge a single receiving device, the turns of the transmit coil  1114  may be evenly spaced to reduce losses, for example, due to capacitive coupling or other sources of loss. In another example, the transmit area  1114  may be configured to charge multiple receiving devices, the turns of the transmit coil  1114  may be concentrated near the periphery or edge of the transmit area  1114  to improve field uniformity. In some embodiments, software comprising instructions executed by a processor to retrieve said arrangements from the database may be configured to provide one or more arrangements of assemblable elements based on user inputs related to the receiver. For example, the user may input a receiver into a mobile device, which may access a database of known arrangements based on receiver requirements, and the mobile device may then display the appropriate known arrangements. In another embodiment, the transmitter may detect a size or type of receiver (as described below in connection with  FIG. 17 ), and then execute instructions via a processor to retrieve appropriate arrangements and configure the coils therein accordingly. In some embodiments, the software may be an application on a mobile device, a computer, or a reference listing that is accessible by the user, for example, on the internet. 
     In some embodiments, the one or more appropriate arrangements of assemblable elements  1110   a - d  for efficient power transfer may be unknown to the user. Due to the complexity of design for such arrangements, the processor executing the software can be configured to execute instructions to present to the user regarding one or more appropriate interlocking arrangements of the assemblable elements  1110   a - d  so as to construct a transmitter for a particular receiver. In some cases the processor may be operatively coupled to a controller (e.g., controller  415  of  FIG. 4 ) and configured to control switches  1117  in a cross-over assemblable element  1110   d . For example, the user may enter a desired size and shape, and the processor may provide instructions for configuring the assemblable elements, configuring the switches  1117 , and/or the timing of connecting/disconnecting the switches  1117 , such that the transmit coil is electrically interconnected to provide efficient and uniform transfer of wireless power. In another embodiment, a controller (e.g., controller  415  of  FIG. 4 ) included in one or more of the assemblable elements can configure a subset arrangement of assemblable elements, for example, a subset of the assemblable elements that make up a transmitter. The subset of assemblable elements may be configured to provide energy transfer based on determining the presence or lack of presence of a receiver within the near-field of the topology of the subset assemblable elements. For example, as described below with reference to  FIG. 17 . 
       FIGS. 12A and 12B  schematically illustrate a perspective view of an exemplary transmit area  1200  in accordance with an exemplary embodiment. Transmit area  1200  may be similar to transmit area  1100  of  FIG. 11 , the transmit area  1200  being configured to generate a wireless field for providing energy transfer to a receiver. The transmit area  1200  may comprise a plurality of assemblable elements illustrated as assemblable elements  1210   a - b  in  FIG. 12A . While assemblable elements  1210   a  and  1210   b  are illustrated as turn and straight assemblable elements, it will be understood that the assemblable elements may be substantially similar to any assemblable element  1110   a - d  of  FIG. 11B-E . 
       FIGS. 12A and 12B  illustrate one configuration for interlocking the assemblable elements of transmit area  1200 . For example, assemblable elements  1210   a  and  1210   b  comprise interlocking edges  1220   a  and  1220   b , respectively, each having an interlocking component  1225   a  and  1225   b  thereon. In the embodiment illustrated in  FIG. 12A , the interlocking component  1225   a  may be a male interlocking component configured to mechanically interlock with a female interlocking component  1225   b  (e.g., similar to a puzzle piece being fitted together). By fitting the male and female interlocking components  1225   a  and  1225   b  together the coil portions  1214   a  and  1214   b  may be electrically interconnected as illustrated in  FIG. 12B . 
     Assemblable elements  1210   a  and  1210   b  are illustrated as square or rectangular. However, this need not be the case, and any shape may be used and any arrangement is possible. In one embodiment, the interlocking components need only facilitate the electrical connection of the coil portions  1214  and  1214   b  to construct a complete coil  1214 . The interlocking edges  1220   a  and  1220   b  need not meet or interlock, so long as interlocking components securely facilitate the electrical connection of the coil portions. 
       FIGS. 13A-13D  schematically illustrate a perspective view of an exemplary transmit area  1300  in accordance with an exemplary embodiment. Transmit area  1300  may similar to transmit area  1100  of  FIG. 11 , but transmit area  1300  is a three-dimensional transmit area configured to generate a wireless field for providing energy transfer to a receiver. The transmit area  1300  may comprise a plurality of assemblable elements illustrated as assemblable elements  1310   a - c  in  FIG. 13A . Assemblable elements  1310   a - c  may be any assemblable elements, for example, substantially similar to any assemblable element  1110   a - d  of  FIGS. 11B-11E . 
       FIG. 13A  depicts assemblable elements  1310   a - c  comprising interlocking edges  1320   a - c , respectively, each having an interlocking component  1325   a - c  thereon. In the embodiment illustrated in  FIG. 13A , the interlocking components  1325   a  and  1325   b  may be a fitted together either mechanically, electrically, magnetically, etc. to form transmit area  1300 . Assemblable elements  1310   a - c  are illustrated as cube assemblable charging elements that may be assembled into the three-dimensional transmit area  1300 . However, assemblable elements  1310   a - c  may be two-dimensional elements stacked or connected into a three-dimensional structure. 
       FIGS. 14A and 14B  are a perspective view of another exemplary transmit area  1400  in accordance with an exemplary embodiment.  FIG. 14B  illustrates a tubular formed transmit area  1400  that may be configured to transfer power to a cylindrically shaped receiver  1408 . Transmit area  1400  may be substantially similar to transmit area  1100  of  FIG. 11A  and transmit area  1300  of  FIG. 13  (e.g., a three-dimensional transmit area). 
     Transmit area  1400  may also comprise a plurality of assemblable elements (e.g., assemblable elements  1410   a  and  1410   b ). The assemblable elements may similar to and include any of the assemblable elements  1110   a - d  of  FIGS. 11B-11E , comprising coil portions  1414   a  and  1414   b  and interlocking edges  1425   a  and  1425   b  with interlocking components (not shown). Assemblable elements  1410   a  and  1410   b  may also be tubular in shape or may be cylindrical, however assemblable elements  1410   a  and  1410   b  need not be so limited. Assemblable elements  1410   a  and  1410   b  may also be flexible and/or malleable to facilitate bending to form the tubular transmit area  1400 . In another embodiment, the assemblable elements  1410   a  and  1410   b  may be rigid but of a small enough size to approximate a tubular transmit area  1410  by placing the plurality of assemblable elements together. As illustrated in  FIG. 14A , the coil portions  1414   a  and  1414   b  may comprise of conductors distributed throughout the surface area of the assemblable elements  1410   a  and  1410   b . In other embodiments, the conductors may be disposed on a select region or portion of the assemblable elements or may be controlled by a cross-over assemblable element, as described above. 
       FIGS. 15A-15C  schematically illustrate a perspective view of an exemplary transmit area  1500  in accordance with an exemplary embodiment. Transmit area  1500  may be similar to transmit area  1100  of  FIG. 11 , however, the assemblable elements  1510  may be hexagonally shaped and comprise at least one coil portion  1514   a . The assemblable elements  1510  may be similar to assemblable elements  1110   a - d  of  FIGS. 11B-11E . 
       FIG. 16  schematically illustrate a perspective view of an exemplary transmit area  1600  in accordance with an exemplary embodiment. Transmit area  1600  may be similar to transmit area  1100  of  FIG. 11 , however, the assemblable elements  1610  may have one or more different shapes capable of forming either a two-dimensional or a three-dimensional transmit area. For example,  FIG. 16  illustrates a spherical transmit area  1600  comprising a plurality assemblable elements  1610   a , each comprising at least one coil portion  1614   a . The plurality of assemblable elements may be a combination of hexagonal assemblable elements  1610   a  and pentagonal assemblable elements  1610   b . As such the transmit area  1600  may be a full sphere (e.g., having a pattern similar to a soccer ball) or a partial sphere (e.g., similar to a bowl). The assemblable elements  1610   a  and  1610   b  may be similar to assemblable elements  1110   a - d  of  FIGS. 11B-11E . While a specific transmit area and assemblable elements are illustrated herein, it will be understood that any shaped transmit area and/or assemblable elements are possible. 
     In some implementations, a wireless power transfer system is provided comprising a transmit area. The transmit area may be made of a plurality of assemblable elements, where each assemblable element may be configured to permit interlocking between one or more of the plurality of assemblable elements. The plurality of assemblable elements may each include a portion of a coil configured to generate a wireless field for providing wireless power transfer. In some embodiments, as described above, the plurality of assemblable elements may be interlocked such that the coil portions are electrically interconnected and configured to provide wireless power. In some embodiments a control unit (e.g., in one or more of the assemblable elements) is provided. The control unit may be configured to instruct one or more coil portions to provide wireless power (e.g., an active area) and instruct the one or more other coil portions to not provide wireless power (e.g., an inactive area). The controller unit may be configured to determine which coil portion to instruct to provide wireless power based, in part, on power transfer or charging requirements of a receive coil relative to the coil portions. 
     In one implementation, the wireless power transfer system described above with respect to  FIGS. 7-16 , may be configured to vary a wireless power transfer based on a detection of a nearby receiver. In some embodiments, each assemblable element may comprise a power amplifier and the transmit circuitry (e.g., as described in  FIGS. 1-6 ) configured to generate a wireless field to provide power transfer independently of the other assemblable elements. For example, a receiver may be positioned within the near-field of the wireless field generated by one or more of the assemblable elements. The wireless power transfer system may be configured to detect the presence of the receiver (or receive coil) relative to the subset of one or more assemblable elements, and then cause the subset of assemblable elements to generate a wireless field for providing wireless power transfer to the receiver. The remaining assemblable elements may remain inactive, thereby conserving power and reducing overall field exposure and radiation. 
     For example, as discussed above with respect to  FIG. 4 , a transmitter  404  can include the presence detector  480 , which can detect the presence, distance, orientation, and/or location of a nearby object. In various other embodiments, the presence detector  480  can be located in another location such as, for example, on the receiver  508 , or elsewhere. In another embodiment, the presence detector  480  may be included in one assemblable element of a transmitter  404 , or each assemblable element may include a presence detector  480 . Similarly, the transmitter  404  may include the load sensing circuit  416  which can detect the absence or presence of active receives in the transmitter  404 &#39;s near-field. For example, load sensing circuit  416  can monitor the current flowing to driver  424  which can be affected by the presence or absence of active receivers. The controller  415  can increase transmission power or activate one or more assemblable elements when a receiver is detected within the near-field of the one or more assemblable elements. In some embodiments, the controller  415  may be included in each assemblable element and being operatively coupled there to facilitate the exchange of communication signals. In other embodiments, the controller  415  may be included in a single master assemblable element operatively coupled to other transmit circuitry included in each of the assemblable elements. 
     Referring back to  FIG. 2 , in certain embodiments, the wireless power transfer system  200  can include receivers  208  of various sizes. In one embodiment, the size of the transmit coil  214  is fixed. Accordingly, the transmit area of a transmitter  204  may not be well matched to different sized receive coils  218 . For a variety of reasons, it can be desirable for the transmitter  204  to use a plurality of transmit coils  214  or one or more transmit coils  214  having a dynamically adjusted size and shape. In some embodiments, as described above, the transmit coils  214  can be arranged based an arrangement of the assemblable elements as described above with respect to  FIGS. 11A-E . Similarly, the transmit coils  214  may be dynamically controlled via one or more switches (e.g., switches  1117 ) where the transmit area includes a cross-over assemblable element (e.g., cross-over assemblable element  1110   d ). In some embodiments, the transmit coils  214  can be modular, whereby each assemblable element comprises a complete transmit coil  214 . In some embodiments, the array can include transmit coils  214  of the same, or substantially the same, size. 
     In various embodiments, each transmit coil  214  can be independently activated, based on detecting the presence or absence of receivers  208  and/or the size of their receive coils  218 . For example, a single transmit coil  214  can provide wireless power to nearby receivers  208  having relatively small receive coils  218 . On the other hand, multiple transmit coils  214  can be provide wireless power to nearby receivers having relatively large receive coils  218 . Transmit coils  214  that are not near receive coils  218  can be deactivated. 
     In another embodiment, portions of transmit coil  214  can be connected and/or skipped in accordance with the above description of  FIGS. 11A-11E , based on detecting the presence or absence of receivers  208  and/or the size of receive coils  218 . For example, one or more loops of transmit coil  214  may be connected or disconnected via switches, such as switches  1117  to modify and adjust loop density of the coil  214 . Accordingly, switches  1117  may be controlled by a controller, for example, controller  415  of  FIG. 4 , based on the presence or absence of a receiver  208 . 
     In some embodiments, the plurality of transmit coils  214  can form a large transmit area. The transmit area can be scalable, covering a larger area using additional transmit coils  214 . The transmit coils  214  can allow for free positioning of devices over a large area. Moreover, they can be configured to simultaneously charge a plurality of receivers  208 . In some embodiments, individual transmit coils  214  can be coupled to each other via communication and synchronization lines configured to exchange control signals. 
       FIG. 17  is a perspective view of an exemplary transmit area  1700  in accordance with an exemplary embodiment. As shown, the transmit area  1700  includes a plurality of assemblable elements  1710   a  and at least one power source assemblable element  1710   b . Power source assemblable element  1710   b  may comprise a power in line  1702  connected to a power source, such as for example, an AC-DC converter, a DC-DC converter, or directly from a conventional DC power source. The assemblable elements  1710   a  and  1710   b  may each comprise some, none, or all transmit circuitry described above in relation to  FIGS. 1-6 , each comprising components (e.g., coils, amplifiers, resonant components) described above. 
     For example, as described above in relation to  FIG. 4 , the assemblable elements may include a presence sensor  480  and/or load sensing circuit  416  configured to detect the presence or absence of a receiver. The presence sensor  480  and load sensing circuit  416  may be some means for detecting the presence or absence of a receiver. For example, transmit area  1700 , which may include one or more active regions  1730  (comprising one or more assemblable elements) may be controlled to generate a wireless field based on detecting the presence of a receiver. Similarly, transmit area  1700  may also comprise inactive regions  1720  comprising one or more assemblable elements that are inactive due to detecting the absence (e.g., actively monitoring surroundings) of a receiver or not detecting that a receiver is present (e.g., passively reacting to the presence of a receiver). In some embodiments, a plurality of the assemblable element  1710   a  and  1710   b  (e.g., all or a subset of the assemblable elements) may include a means for detecting a receiver. Or, in another embodiment, a single assemblable element may include a means for detecting the receiver, the means for detecting a receiver being operatively coupled to one or more controllers and configured to control the transmit coils to generate one or more wireless fields. 
     The assemblable elements  1710   a  and  1710   b  are shown as being hexagonal; however, in some embodiments, the transmit coils may be of any other shape (e.g., triangular, circular, hexagonal, etc.). The transmit coils  1714  are shown as being circular; however, the transmit coils may be of any other shape. In some embodiments, the transmit coils may form an array of transmit coils, wherein each transmit coil is positioned substantially adjacent to the other transmit coils of the transmit area  1700 . In some embodiments, the transmit coils may be positioned in an overlapping manner, wherein each of the transmit coils may overlap with one or more other transmit coils in the transmit area  1700 . In another embodiment, the transmit coils may be portions of one or more dynamically reconfigurable transmit coils configured into a plurality of transmit coils disposed throughout the assemblable elements  1710   a  and  1710   b . For example, as described above in accordance with  FIG. 11A , each assemblable element may comprise a portion of one or more transmit coils, which may be electrically interconnected due to interlocking the assemblable elements  1710   a  and  1710   b . Additionally, the transmit coils depicted in  FIG. 17  may be multi-turn coils. However, in other embodiments, the transmit coils may be single turn coils and may be either single- or multi-layer coils. In some embodiments, the transmit coils may have inductances of 2000nH. In other embodiments, the transmit coils may have inductances greater than or less than 2000 nH. In other embodiments, each of the transmit coils may have inductances of different values, or various combinations of transmit coils may share inductances of different values. 
     In some embodiments, assemblable element  1710   b  may be a main or master assemblable element. Assemblable element  1710   b  may comprise power in line  1702  connected to a power source. Remaining assemblable elements  1710   a  may include electrical connections or lines (not shown) operatively coupled between neighboring assemblable elements and configured to distribute power (e.g., AC or DC power) from assemblable element  1710   b  to active region  1730  to generate a desired wireless field based on the detected receiver. 
     In some embodiments, the assemblable elements  1710   a  and  1710   b  may include a synchronization line (not shown) configured to facilitate synchronization and control of the phase of the transmit coils  1714 . For example, synchronization line may be disposed between oscillators (e.g., oscillator  423  of  FIG. 4 ) of various assemblable elements so that a controller (e.g., controller  415  of  FIG. 4 ) may adjust the frequency or phase of the oscillators of each assemblable element, thereby adjusting the output power and phase synchronization of the multiple transmit coils. 
     In some embodiments, alternatively or in combination, the assemblable elements  1710   a  and  1710   b  may comprise a communication line (not shown) configured to permit the exchange of communication and control signals between the plurality of assemblable elements  1710   a  and  1710   b . The communication line may permit an exchange of information concerning characteristics of the wireless power transfer (e.g., information pertaining charging power levels, presence or absence of a receiver, defining the active and/or inactive regions, etc.). In some embodiments, the communication line may be a means for coordinating the wireless power transfer of the transmit area  1700  based on the exchanged information. For example, the transmit circuits may each be configured to generate a wireless field by the associated transmit coils based on a signal generated by the power amplifiers in response to the exchanged information, as discussed above in relation to  FIG. 4 . 
     As described above, the assemblable elements  1710   a  and  1710   b  may each comprise some or all of the transmit circuitry described above in relation to  FIGS. 1-6 . Such circuitry need not be included for each assemblable element  1710   a . For example, each assemblable element may comprise one or more components of the transmit circuitry. In some embodiments, the assemblable elements comprise at least a power amplifier (not shown), for example, power amplifier  424  of  FIG. 4 , and a transmit coil  1714 . 
     In one embodiment, each assemblable element  1710   a  and  1710   b  may be substantially similar to the transmitters described in connection with  FIGS. 1-6 . Thus, each assemblable element  1710   a  and  1710   b  comprises all the transmit circuitry described above, including, for example, an AC-DC converter (not shown), controller  415 , oscillator  222 , driver circuit  224 , etc. of  FIGS. 2-6 . Each assemblable element  1710   a  and  1710   b  may receive AC power directly from the power source via power in/out lines (not shown). The transmit coils  1714  are interconnected via the power in/out lines that extend throughout and between the assemblable elements  1710   a  and  1710   b . In some embodiments, the interlocking of the assemblable elements  1710   a  and  1710   b  facilitates the electrical interconnection of the transmit coils  1714  through the power in/out lines. Assemblable elements  1710   a  and  1710   b  may comprise two power lines, for example, an AC power in or AC power out line, as shown in Table 1 below. 
     
       
         
           
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Number 
                 Signal name 
               
               
                   
               
             
            
               
                 1 
                 AC power 
               
               
                   
                 out 
               
               
                 2 
                 AC power in 
               
               
                   
               
            
           
         
       
     
     In another embodiment, each assemblable element  1710   a  comprises some of the transmit circuit described in above, including, for example, an AC-DC converter (not shown), controller  415 , oscillator  222 , driver circuit  224 , etc. of  FIGS. 2-6 . Thus, each of assemblable elements  1710   a  and  1710   b  may be substantially similar in function and can be independently driven by the transmit circuitry therein. However, in one embodiment, each assemblable element  1710   a  and  1710   b  does not include oscillators (e.g., oscillators  222  of  FIG. 2 ). Thus, at least one assemblable element may include an oscillator configured to maintain a phase of the wireless field (e.g., at 6.78 MHz phase, however other phases and frequencies are possible). The remaining assemblable elements comprise a synchronization line configured to control the phase across the coils  1714 . Thus, the transmit coils  1714  may be interconnected through power lines (not shown), as described above, and the phase may be controlled via at least one synchronization line operatively coupling each assemblable element. In some embodiments, the interlocking of the assemblable elements  1710   a  and  1710   b  facilitates the electrical interconnection of the transmit coils  1714  through the power lines and the interconnection of the synchronization line. Assemblable elements  1710   a  and  1710   b  may comprise three electrically interconnected lines, for example, a AC power in (e.g., AC hot), AC power out (e.g., AC neutral), and a synchronization line, as shown in Table 2 below. 
     
       
         
           
               
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 Number 
                 Signal name 
                 Description 
                 Notes 
               
               
                   
               
             
            
               
                 1 
                 AC hot 
                   
                   
               
               
                 2 
                 AC neutral 
               
               
                 3 
                 Sync 
                 6.78 MHz 
                 Configured to sync 
               
               
                   
                   
                 phase-accurate 
                 one or more assemblable 
               
               
                   
                   
                 signal 
                 elements 
               
               
                   
               
            
           
         
       
     
     In another embodiment, main assemblable element  1710   b  may be a power assemblable element having power input line  1702  connected to a power source, such as for example, an AC-DC converter. Remaining assemblable elements  1710   a  may not include such a converter, while still comprising, at least, power amplifiers  424  and controllers  415  of  FIG. 4 . Thus, main assemblable element  1710   b  may be configured to distribute DC power amongst the plurality of assemblable elements  1710   a  via the AC-DC converter. In some embodiments, the main assemblable element  1710   b  may be configured, for example, to convert an AC power source to DC power to generate a fixed DC power level (e.g., 12 volts) or vary the DC voltage level based on the demands of the rest of the system. For example, in the case of a charger intended to charge multiple devices, the voltage may be increased as more devices are added, to ensure enough power is available (given a relatively constant coil current) to charge all devices that are placed on the charger. Similar to previously described embodiments and as shown in Table 3, the assemblable elements  1710   a  may comprise a single synchronization line along with the power in and power out lines (e.g., DC+ and/or DC-lines) configured to supply power amongst the assemblable elements. In some embodiments, an optional communication line may be interconnected between the assemblable elements  1710   a  and  1710   b  configured to coordinate DC power levels in the event that the system requires varying DC power. 
     
       
         
           
               
               
               
               
             
               
                 TABLE 3 
               
               
                   
               
               
                 Number 
                 Signal name 
                 Description 
                 Notes 
               
               
                   
               
             
            
               
                 1 
                 DC+ 
                 Power 
                   
               
               
                 2 
                 DC− 
                 Power 
               
               
                 3 
                 Sync 
                 6.78 MHz 
                 Configured to sync one or 
               
               
                   
                   
                 phase-accurate 
                 more assemblable 
               
               
                   
                   
                 signal 
                 elements 
               
               
                 4 (opt) 
                 Comm 
                 Communications 
                 Optional 
               
               
                   
                   
                 line 
               
               
                   
               
            
           
         
       
     
     In another embodiment, assemblable element  1710   b  may be a master assemblable element  1710   b  configured to control and monitor the functions of the assemblable elements  1710   a  (e.g., slave assemblable elements). In this embodiment, assemblable element  1710   b  may comprise a AC-DC converter configured to supply DC power, as described above, to the remaining assemblable elements  1710   a ; provide a master clock for controlling synchronization of the phase of the assemblable elements  1710   a  (e.g., a master oscillator  222 ); and a controller  415  of  FIG. 4  configured to control the power transfer and wireless fields generated by each transmit coil  1714 . The assemblable elements  1714  may comprise only power amplifiers  424  of  FIG. 4  and transmit coils  1714  for generating the wireless field. Thus, as shown in Table 4, each assemblable element may comprise four lines for managing and controlling the wireless power transfer, e.g., a power in line, a power out line, a master clock line, and a control communications line. 
     
       
         
           
               
               
               
               
             
               
                 TABLE 4 
               
               
                   
               
               
                 Number 
                 Signal name 
                 Description 
                 Notes 
               
               
                   
               
             
            
               
                 1 
                 DC+ 
                 Power 
                   
               
               
                 2 
                 DC− 
                 Power 
               
               
                 3 
                 Clock 
                 Master clock 
                 Used by all pads 
               
               
                 4 
                 Comm 
                 Control line 
                 Control signals to other pads 
               
               
                   
               
            
           
         
       
     
       FIG. 18  is a flowchart  1800  of an exemplary method of wireless power transfer in accordance with an exemplary embodiment. Although the method of flowchart  1800  is described herein with reference to the wireless power transfer system  100  discussed above with respect to  FIGS. 1-2 , the transmitter discussed above with respect to  FIG. 4 , and the transmit areas discussed above with respect to  FIGS. 10-17 , in some embodiments, the method of flowchart may be implemented by another device described herein, or any other suitable device. In some embodiments, the blocks in flowchart  1800  may be performed by a processor or controller, such as, for example, the controller  415  (referenced in  FIG. 4 ), and/or the processor-signaling controller  516  (referenced in  FIG. 5 ). In other embodiments, the blocks in flowchart  1800  may be performed based on or in conjunction with a smart application as described herein. Although the method of flow chart  1800  is described herein with reference to a particular order, in various embodiments, blocks herein can be performed in a different order, or omitted, and additional blocks may be added. 
     At block  1810 , a plurality of assemblable elements are provided. For example, the assemblable elements may be similar to assemblable elements  1110   a - d  of  FIGS. 11A-11E . The assemblable elements may be configured to interlock, as described above, between one or more of the neighboring assemblable elements. The assemblable elements may also comprise a transmit coil or a portion of a transmit coil. In some embodiments, any one assemblable element may not be able to generate a wireless field on its own, but a plurality of assemblable elements may be configured to generate a wireless field. The assemblable elements may individually or collectively comprise one or more components of transmit circuitry of  FIG. 1-6 , as described above. 
     At block  1820 , the plurality assemblable elements may be interlocked to form a single structure or arrangement of elements. The structure may form a transmit area having one or more transmit coils. In some embodiments, the assemblable elements may be selectively interlocked based on the wireless power transfer requirements of the transmitter and/or receiver. For example, the assemblable elements may be interlocked as described above in  FIGS. 11A-11D . In some embodiments, the assemblable elements may be interlocked or arranged to generate wireless field based on the shape, size, etc. of the receiver as detected by a means for detecting the presence or absence of the receiver. In some embodiments, the arrangement of assemblable elements may be predetermined based on the power transfer requirements, shape, size, etc., of the receiver. The predetermined arrangement may be retrieved from a database of arrangements. The interlocking of the assemblable elements may also facilitate the electrical interconnection of one or more portions of the transmit coil, thereby forming one or more dynamically reconfigurable transmit coils as described herein. Further, the interlocking of assemblable elements may electrically connect synchronization lines, communication lines, and other transmit circuitry configured to permit the control of one or more regions of the transmit area. 
     At block  1830 , the plurality of assemblable elements may be configured to provide wireless power transfer. In some embodiments, the assemblable elements may be driven by transmit circuitry to generate a wireless field based on the transmit coils formed through electrically interconnecting the portions of transmit coils. The wireless field may be used to wirelessly transfer power to or wirelessly communicate with another device (e.g., a receiver). 
     The various operations of methods described above can be performed by any suitable means capable of performing the operations, such as various hardware and/or software component(s), circuits, and/or module(s). Generally, any operations illustrated in the Figures can be performed by corresponding functional means capable of performing the operations. 
     Information and signals can be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that can be referenced throughout the above description can be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof. 
     The various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein can be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. The described functionality can be implemented in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the embodiments of the present disclosure. 
     The various illustrative blocks, modules, and circuits described in connection with the embodiments disclosed herein can be implemented or performed with a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor can be a microprocessor, but in the alternative, the processor can be any conventional processor, controller, microcontroller, or state machine. A processor can also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. 
     The steps of a method or algorithm and functions described in connection with the embodiments disclosed herein can be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. If implemented in software, the functions can be stored on or transmitted over as one or more instructions or code on a tangible, non-transitory computer-readable medium. A software module can reside in Random Access Memory (RAM), flash memory, Read Only Memory (ROM), Electrically Programmable ROM (EPROM), Electrically Erasable Programmable ROM (EEPROM), registers, hard disk, a removable disk, a CD ROM, or any other form of storage medium known in the art. A storage medium is coupled to the processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium can be integral to the processor. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk, and blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer readable media. The processor and the storage medium can reside in an ASIC. The ASIC can reside in a user terminal. In the alternative, the processor and the storage medium can reside as discrete components in a user terminal. 
     For purposes of summarizing the disclosure, certain aspects, advantages and novel features of the present disclosure have been described herein. It is to be understood that not necessarily all such advantages can be achieved in accordance with any particular embodiment of the present disclosure. Thus, the present disclosure can be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other advantages as can be taught or suggested herein. 
     Various modifications of the above described embodiments will be readily apparent, and the generic principles defined herein can be applied to other embodiments without departing from the spirit or scope of the present disclosure. Thus, the present disclosure is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.