WO2019051022A1

WO2019051022A1 - Wireless charging system and related metho

Info

Publication number: WO2019051022A1
Application number: PCT/US2018/049658
Authority: WO
Inventors: Joshua Duffy; Leslie G. FARKAS; Juan Perez
Original assignee: Zpower, Llc
Priority date: 2017-09-06
Filing date: 2018-09-06
Publication date: 2019-03-14
Also published as: WO2019051022A9

Abstract

A wireless charging system includes a first conductor and a second conductor. The first conductor forms a power transmitting coil including a plurality of first wraps of the first conductor. The plurality of first wraps includes an outermost first wrap defining an outer diameter and an innermost first wrap defining an inner diameter. The outer diameter is between ten millimeters and twelve millimeters. The second conductor forms a power receiving coil operable to receive power from the power transmitting coil. The power receiving coil includes a plurality of second wraps of the second conductor. The plurality of second wraps includes an outermost second wrap defining a stadium shape.

Description

WIRELESS CHARGING SYSTEM AND RELATED METHO

CROSS REFERENCE TO RELATED APPLICATION

[0001] This PCT application claims the benefit of U.S. provisional application no.

62/554,684, filed on September 6, 2017. This document is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

[0002] The present disclosure relates generally to a compact wireless power transmitter and related methods.

BACKGROUND

[0003] This section provides background information related to the present disclosure and is not necessarily prior art.

[0004] Traditional wireless charging systems use inductive coupling, where a primary coil (e.g., a power transmit unit) is electromagnetically coupled to a secondary coil (e.g., a power receiver unit). Such systems require that the primary coil be in close proximity and alignment with the secondary coil, such that the secondary coil intercepts the flux of the magnetic field generated, and radiated in all directions, by the primary coil. The amount of energy captured by the secondary coil is proportional to the cross-sectional area of the secondary coil. For example, the energy captured by the secondary coil may be maximized when the dimensions of the secondary coil are equal to the dimensions of the primary coil, and the secondary coil is aligned (e.g., parallel) with, and separated by a small distance from, the primary coil. In this regard, the separation, alignment, and relative sizes of the primary and secondary coils determine a coupling factor, which, in turn, impacts the efficiency of the transfer of energy from the primary coil to the secondary coil. Known inductive charging systems typically have a coupling factor between 0.3 and 0.6.

[0005] In a resonant inductive coupling system, the primary and secondary coil resonate at identical frequencies. The primary coil generates an oscillating magnetic field that allows for more efficient power transfer between the primary and secondary coils, even when the separation, alignment, and relative sizes of the primary and secondary coils are less than what would otherwise be required in a traditional inductively coupled system. Moreover, a resonant inductive coupling system allows for energy transfer from a single primary coil to multiple secondary coils. [0006] While known wireless charging systems have proven acceptable for their intended purposes, a continuous need for improvement in the relevant art remains.

SUMMARY

[0007] This section provides a general summary of the disclosure, and is not a

comprehensive disclosure of its full scope or all of its features.

[0008] One aspect of the disclosure provides a wireless charging system. The wireless charging system includes a first conductor and a second conductor. The first conductor forms a power transmitting coil including a plurality of first wraps of the first conductor. The plurality of first wraps includes an outermost first wrap defining an outer diameter and an innermost first wrap defining an inner diameter. The outer diameter is between ten millimeters and twelve millimeters. The second conductor forms a power receiving coil operable to receive power from the power transmitting coil. The power receiving coil includes a plurality of second wraps of the second conductor. The plurality of second wraps includes an outermost second wrap defining a stadium shape.

[0009] Implementations of the disclosure may include one or more of the following optional features. In some implementations, the plurality of first wraps is disposed about a first axis and defines a first area extending in a direction perpendicular to the first axis. The plurality of second wraps may be disposed about a second axis and define a second area extending in a direction perpendicular to the second axis. A ratio of the first area to the second area may be between 2.5: 1 and 5: 1.

[0010] In some implementations, the plurality of first wraps includes ten wraps of the first conductor.

[0011] In some implementations, the wireless charging system includes a ferrite and a printed circuit board assembly in communication with the power transmitting coil. The ferrite may be disposed between the power transmitting coil and the printed circuit board assembly. The printed circuit board assembly may include a processor operable to control a flow of current through the first conductor.

[0012] In some implementations, the wireless charging system includes a printed circuit board assembly and an insert. The printed circuit board assembly may be coupled to the power transmitting coil and define a first aperture and a second aperture. The insert may include a proximal end and a distal end opposite the proximal end. The proximal end may define a cavity configured to receive the power receiving coil. The distal end may include a first pin and a second pin and define a recess configured to receive the power transmitting coil. The recess may be disposed between the first pin and the second pin. The first pin may be disposed within the first aperture and the second pin may be disposed within the second aperture. The first pin may be secured to the printed circuit board assembly.

[0013] Another aspect of the disclosure provides a wireless charging system. The wireless charging system includes a first conductor and a second conductor. The first conductor forms a power transmitting coil including a plurality of first wraps of the first conductor. The plurality of first wraps is disposed about a first axis and define a first area extending in a direction perpendicular to the first axis. The second conductor forms a power receiving coil including a plurality of second wraps of the second conductor. The plurality of second wraps is disposed about a second axis and define a second area extending in a direction perpendicular to the second axis. A ratio of the first area to the second area is between 2.5: 1 and 5: 1.

[0014] This aspect may include one or more of the following optional features. In some implementations, the plurality of first wraps includes an outermost first wrap defining an outer diameter and an innermost first wrap defining an inner diameter. The outer diameter may be between ten millimeters and twelve millimeters.

[0015] In some implementations, the plurality of second wraps includes an outermost second wrap defining a stadium shape.

[0016] In some implementations, the first axis is parallel to the second axis.

[0017] In some implementations, the first area is parallel to the second area.

[0018] In some implementations, the first area defines a first shape and the second area defines a second shape that is the same as the first shape.

[0019] In some implementations, the wireless charging system includes a ferrite and a printed circuit board assembly in communication with the power transmitting coil. The ferrite may be disposed between the power transmitting coil and the printed circuit board assembly. In some implementations, the printed circuit board assembly includes a processor operable to control a flow of current through the first conductor.

[0020] In some implementations, the wireless charging system includes a printed circuit board assembly and an insert. The printed circuit board assembly may be coupled to the power transmitting coil and may define a first aperture and a second aperture. The insert may include a proximal end and a distal end opposite the proximal end. The proximal end may define a cavity configured to receive the power receiving coil. The distal end may include a first pin and a second pin and may define a recess configured to receive the power transmitting coil. The first pin may be secured to the printed circuit board assembly.

[0021] Yet another aspect of the disclosure provides a method of manufacturing a wireless charging system. The method includes providing an insert having a proximal end and a distal end opposite the proximal end. The proximal end defines a cavity configured to receive a power receiving coil. The distal end includes a first pin and a second pin and defines a recess configured to receive a power transmitting coil. The method also includes providing a power transmitter assembly having a printed circuit board assembly and a power transmitting coil. The power transmitting coil defines a first aperture and a second aperture. The power transmitting coil is coupled to, and in communication with, the printed circuit board assembly. The method further includes positioning the power transmitting coil within the recess. The method also includes heat staking the first pin within the first aperture and the second pin within the second aperture.

[0022] Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

DESCRIPTION OF DRAWINGS

[0023] FIG. 1 is a perspective view of wireless charging system according to the principles of the present disclosure.

[0024] FIG. 2A is an exploded top perspective view of a portion of the wireless charging system of FIG. 1.

[0025] FIG. 2B is an exploded bottom perspective view of a portion of the wireless charging system of FIG. 1.

[0026] FIG. 3 is an exploded view of a primary coil of the wireless charging system of FIG. 1.

[0027] FIG. 4 is a top view of the primary coil of FIG. 3.

[0028] FIG. 5 is a bottom view of a secondary coil of the wireless charging system of FIG. 1.

[0029] FIG. 6 is a cross-sectional view of the wireless charging system of FIG. 1.

[0030] FIG. 7 is a schematic view of a charging circuit according to the principles of the present disclosure.

[0031] Like reference symbols in the various drawings indicate like elements. [0032] These figures are provided as examples and are not intended to limit the scope of the claimed invention.

DETAILED DESCRIPTION

[0033] Example configurations will now be described more fully with reference to the accompanying drawings. Example configurations are provided so that this disclosure will be thorough, and will fully convey the scope of the disclosure to those of ordinary skill in the art. Specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of configurations of the present disclosure. It will be apparent to those of ordinary skill in the art that specific details need not be employed, that example configurations may be embodied in many different forms, and that the specific details and the example configurations should not be construed to limit the scope of the disclosure.

[0034] With reference to FIG. 1, a wireless charging system 10 in accordance with the principles of the present disclosure is illustrated. The wireless charging system 10 may include a charger 12 and a battery-powered device 14. While the device 14 is shown and described herein as being a hearing aid, it will be appreciated that the device 14 may include other battery-powered devices within the scope of the present disclosure. For example, in some implementations, the device 14 includes a battery-powered phone, camera, watch, flashlight, hand-held radio, Bluetooth speaker, or toy.

[0035] The charger 12 may include a housing 16 and one or more charger subassemblies 18. For example, as illustrated in FIG. 1, in some implementations, the charger 12 includes two charger subassemblies 18. As will be explained in more detail below, each charger subassembly 18 may be configured to receive the device 14 in order to transfer electrical power from the charger subassembly 18 to the device 14. In this regard, the charger 12 may be electrically coupled to an external power source (not shown) by a cord or other suitable wired or wireless transmission means. The charger 12 may also include one or more visual alerts 500 (e.g., lights) that communicate with a printed circuit board assembly 40 and are activated when (i) the device 14 is in electrical communication with the charger 12, (ii) the device 14 is being charged by the charger 12, (iii) the charger 12 has completed its charging of the device 14, (iv) the charger 12 registers a charging error in the device 14, or any combination thereof. When activated, the visual alert 500 may display one or more colors indicating the type of activity being performed by the charger 12 or the device 14. For example, the visual alert 500 may display an orange light when the charger 12 is charging the device 14, the visual alert 500 may display a green light when the charger 12 has completed its charging of the device 14, the visual alert 500 may display a red light if the charger 12 registers a charging error in the device 14, or any combination thereof.

[0036] The housing 16 may include one or more chambers 20 sized and shaped to receive the one or more charger subassemblies 18. In some implementations, the number of chambers 20 equals the number of charger subassemblies 18 such that, in the assembled configuration, each charger subassembly 18 is located in one of the chambers 20.

[0037] The charger subassembly 18 may include an insert 24 and a power transmitter assembly 26. With reference to FIGS. 2A and 2B, the insert 24 may include a proximal end 28 and distal end 30 opposite the proximal end 28. The proximal end 28 may define a recess 32. The distal end 30 may define a cavity 34 and may include one or more pins 36. The recess 32 may be sized and shaped to receive the device 14. The cavity 34 may be sized and shaped to receive at least a portion of the power transmitter assembly 26. The pins 36 may be disposed at or proximate to one or more corners of the distal end 30 such that the cavity 34 is disposed between the pins 36. In some implementations, distal end 30 includes two pins 36 disposed proximate to opposite corners of the distal end 30.

[0038] With reference to FIG. 3, the power transmitter assembly 26 may include a printed circuit board assembly (PCBA) 40, a ferrite 42, an adhesive 44, a conductor 46, and a core 48. As illustrated in FIGS. 2A and 2B, the PCBA 40 may include a processor 50, a memory 52 connected to the processor 50 using various circuits, one or more apertures 54, and a pair of pins (e.g., bus wires) 56 in electrical communication with the processor 50 or the memory 52 via the various circuits. The processor 50 can process instructions for execution, including instructions stored in the memory 52. In other implementations, multiple processors and/or multiple buses may be used, as appropriate, along with multiple memories and types of memory. Also, multiple PCBAs 40 may be connected, with each device providing portions of the necessary operations.

[0039] The memory 52 stores information non-transitorily within the PCBA 40. For example, the memory 52 may contain instructions that, when executed by the processor 50, perform one or more methods, such as those described above. The memory 52 may be a computer-readable medium, a volatile memory unit(s), or non-volatile memory unit(s). The non-transitory memory 52 may be physical devices used to store programs (e.g., sequences of instructions) or data (e.g., program state information) on a temporary or permanent basis for use by the processor 50. Examples of non-volatile memory include, but are not limited to, flash memory and read-only memory (ROM) / programmable read-only memory (PROM) / erasable programmable read-only memory (EPROM) / electronically erasable programmable read-only memory (EEPROM) (e.g., typically used for firmware, such as boot programs). Examples of volatile memory include, but are not limited to, random access memory (RAM), dynamic random access memory (DRAM), static random access memory (SRAM), phase change memory (PCM), as well as disks or tapes.

[0040] The apertures 54 may be disposed at or proximate to one or more corners of the PCBA 40 such that the conductor 46 is disposed between the apertures 54. In some implementations, PCBA 40 defines two apertures 54 disposed proximate to opposite corners of the PCBA 40.

[0041] With further reference to FIG. 3, the ferrite 42 may include a non-conductive, ferrimagnetic material, such as a ceramic compound, for example. As illustrated, the ferrite 42 may define a substantially cylindrical construct having a diameter between ten millimeters and fifteen millimeters and a thickness Tl between 0.5 millimeters and 1.3 millimeters. In some implementations, the ferrite 42 has a diameter substantially equal to twelve millimeters and a thickness Tl substantially equal to 0.9 millimeters.

[0042] The adhesive 44 may include any material suitable to couple the conductor 46 to the ferrite 42. In some implementations, the adhesive 44 includes a flexible sheet of material (e.g., tape) coupling the conductor 46 to the ferrite 42. In this regard, the adhesive 44 may define a circular shape having a diameter between ten millimeters and fifteen millimeters. In some implementations, the adhesive 44 has a diameter substantially equal to the diameter of the ferrite 42.

[0043] The conductor 46 may include a metallic wire having a length extending from a proximal end 58 of the conductor 46 to a distal end 60 of the conductor 46 opposite the proximal end 58, and defining a thickness or diameter between 0.25 millimeters and

0.40 millimeters along the length of the conductor 46. For example, the conductor 46 may include a copper wire having a thickness or diameter between 0.25 millimeters and

0.40 millimeters. In some implementations, the conductor 46 includes a copper wire having a thickness or diameter substantially equal to 0.31 millimeters. In an assembled configuration, the proximal end 58 may be electrically coupled to a first of the pins 56 and the distal end 60 may be electrically coupled to a second of the pins 56, such that the conductor 46 carries electrical current from the first of the pins 56 to the second of the pins 56. [0044] As illustrated in FIG. 4, the conductor 46 may be flexed into, and define, a circular shape such that the proximal end 58 is disposed at an inner side 62 of the circular shape and the distal end 60 is disposed at an outer side 64 of the circular shape, and such that the conductor defines a surface area 65 extending between the inner and outer sides 62, 64 and surrounding an axis Al . In some implementations, the axis Al is centrally-disposed relative to the outer side 64 of the shape defined by the conductor 46, and the surface area 65 extends in a direction substantially perpendicular to the axis Al .

[0045] The conductor 46 may be flexed to form a spiral or coil having a plurality of wraps 66 disposed between the inner and outer sides 62, 64 and defining the circular shape having a thickness T2 (FIG. 3) between 1.6 millimeters and 1.8 millimeters. In this regard, the conductor 46 may be referred to herein as the "power transmitting coil 46." In some implementations, the circular shape has a thickness T2 substantially equal to 1.71

millimeters. The outer side 64 may define a diameter between eight millimeters and fifteen millimeters. In some implementations, the outer side 64 defines a diameter substantially equal to ten millimeters. In some implementations, the outer side 64 defines a diameter substantially equal to twelve millimeters. The circular spiral may include between eight and twelve wraps 66 of the conductor 46. In some implementations, the circular spiral includes ten wraps 66 of the conductor 46.

[0046] With further reference to FIG. 3, the core 48 may include a non-conductive, ferrimagnetic material, such as a ceramic compound, for example. As illustrated, the core 48 may define a substantially cylindrical construct having a diameter between one millimeter and five millimeters. For example, the core 48 defines a diameter substantially equal to three millimeters. In some implementations, the core 48 is integrally formed with the ferrite 42.

[0047] With reference to FIGS. 2A and 2B, in an assembled configuration, the conductor 46 may be disposed about the core 48, and the power transmitter assembly 26 may be coupled to the insert 24. For example, the inner side 62 of the conductor 46 surrounds the core 48, the conductor 46 is disposed within the cavity 34, and the pins 36 of the insert 24 are disposed within the apertures 54 of the PCBA 40 such that the PCBA 40 faces the distal end 30 of the insert 24. In some implementations, the pins 36 of the insert 24 are secured within the apertures 54 of the PCBA 40 using a friction-fit or heat staking process. It will be appreciated, however, that the pins 36 may be secured within the apertures 54 using other techniques (e.g., adhesive) within the scope of the present disclosure. [0048] With reference to FIGS. 1-2B, the device 14 may include a housing 70 and a power receiver assembly 72 disposed within the housing 70. As previously explained, the housing 70 may define a hearing aid or other battery-powered device configured to be received by the recess 32 of the insert 24

[0049] As illustrated in FIG. 5, the power receiver assembly 72 may include a power storage device (e.g., a rechargeable battery 74), a substrate 80, and a conductor 82. The substrate 80 may include a non-conductive, ferrimagnetic material, such as a ceramic compound, for example. As illustrated, in some implementations, the substrate 80 defines a substantially rectangular shape having a length LI (FIG. 5) between five millimeters and ten millimeters, a width Wl between two millimeters and four millimeters, and a thickness T3 (FIG. 2B) between 0.1 millimeters and 0.3 millimeters. In some implementations, the substrate 80 defines a substantially rectangular shape having a length LI substantially equal to 6.7 millimeters, a width Wl substantially equal to 3.1 millimeters, and a thickness T3 substantially equal to 0.2 millimeters. It will be appreciated, however, that the substrate 80 may define other shapes (e.g., oval, circle, stadium, etc.) within the scope of the present disclosure.

[0050] The conductor 82 may include a metallic wire having a length extending from a proximal end 84 of the conductor 82 to a distal end 86 of the conductor 82 opposite the proximal end 84, and defining a thickness or diameter between 0.10 millimeters and

0.20 millimeters along the length of the conductor 82. For example, the conductor 82 includes a copper wire having a thickness or diameter between 0.10 millimeters and

0.20 millimeters. In some implementations, the conductor 82 includes a copper wire having a thickness or diameter substantially equal to 0.15 millimeters. In an assembled configuration, the proximal end 84 is electrically coupled to a positive terminal (not shown) of the battery (e.g., rechargeable battery) 74 and the distal end 86 may be electrically coupled to a negative terminal (not shown) of the battery (e.g., rechargeable battery) 74, such that the conductor 82 carries electrical current to the battery (e.g., rechargeable battery) 74.

[0051] As illustrated in FIG. 5, in some implementations, the conductor 82 is flexed into, and defines, a stadium shape such that the proximal end 84 is disposed at an inner side 88 of the stadium shape and the distal end 86 is disposed at an outer side 90 of the stadium shape, and such that the conductor 82 defines a surface area 91 extending between the inner and outer sides 88, 90 and surrounding an axis A2. In some implementations, the axis A2 is centrally-disposed relative to the outer side 90 of the shape defined by the conductor 82, and the surface area 91 extends in a direction substantially perpendicular to the axis A2. A ratio of the surface area 65 of the conductor 46 relative to the surface area 91 of the conductor 82 may be between 2.5: 1 and 5: 1. While the conductor 82 is generally shown and described herein as defining a stadium shape, it will be appreciated that the conductor 82 may define other shapes (e.g., oval, circle, rectangle, etc.) within the scope of the present disclosure. In this regard, in some implementations, the shape of the substrate 80 or the conductor 82 may match the shape of the ferrite 42 or the conductor 46.

[0052] In some implementations, the conductor 82 is flexed to form a spiral having a plurality of wraps 92 disposed between the inner and outer sides 88, 90 and defining the stadium shape. In this regard, the conductor 82 may be referred to herein as the "power receiving coil 82." The outer side 90 may define a length L2 between five millimeters and ten millimeters and a width W2 between two millimeters and four millimeters. The inner side 88 may define a length L3 between three millimeters and six millimeters and a width W3 between 0.5 millimeters and two millimeters. In some implementations, the outer side 90 defines a length L2 substantially equal to 6.0 millimeters and a width W2 substantially equal to 2.8 millimeters, and the inner side 88 defines a length L3 substantially equal to

4.6 millimeters and a width W3 substantially equal to one millimeter. The stadium-shaped spiral may include between five and twelve wraps 92 of the conductor 82. In some implementations, the stadium-shaped spiral includes eight wraps 92 of the conductor 82.

[0053] With reference to FIG. 1, in an assembled configuration, the device 14 may be disposed within the recess 32 of the charger 12 such that the axis Al of the shape defined by the conductor 46 is parallel to the axis A2 of the shape defined by the conductor 82. For example, the axis Al is aligned with (e.g., collinear with) the axis A2 of the conductor 82, such that the surface area 65 defined by the conductor 46 is substantially parallel to the surface area 91 defined by the conductor 82. As illustrated in FIG. 6, in some

implementations, the conductor 46 and the conductor 82 define a gap or void 96

therebetween. The void 96 may define a height between one millimeter and three millimeters extending in a direction substantially parallel to the axes Al, A2. In some implementations, the void 96 defines a height substantially equal to two millimeters measured in a direction extending substantially parallel to the axes Al, A2.

[0054] A method of manufacturing the wireless charging system 10 may include providing the insert 24, the PCB A 40, and the power transmitting coil 46. The method may include placing, or otherwise positioning, the power transmitting coil 46 within the recess 32 of the insert 24 and placing first and second pins of the plurality of pins 36 within first and second apertures, respectively, of the apertures 54. The method may also include heat staking the first of the pins 36 within the first of the apertures 54 and heat staking the second of the pins 36 within the second of the apertures 54.

[0055] With reference to FIG. 7, a charging circuit 100 for transferring, and regulating the transfer of, electrical power from the conductor 46 to the conductor 82 and to the battery 74 is illustrated. In this regard, the charging circuit 100 may include a transmission portion 100-1 and a receiver portion 100-2. The transmission portion 100-1 of the charging circuit 100 may be implemented within the charger 12, and the receiver portion 100-2 of the charging circuit 100 may be implemented within the device 14. In some implementations, the transmission portion 100-1 of the charging circuit 100 is implemented within the power transmitter assembly 26. For example, the charging circuit 100 may be implemented within the PCBA 40 (e.g., the processor 50) of the power transmitter assembly 26.

[0056] The transmission portion 100-1 of the charging circuit 100 may include a power source (e.g., supply voltage Vi), the conductor 46, and an input capacitor Ci, and may define a source impedance Rs. The power source (e.g., supply voltage Vi) may include an external power source for transmitting current (e.g., supply current Ii) through a cord or other suitable wired or wireless transmission means and through the conductor 46 of the transmission portion 100-1. The conductor 46 may define a series resistance Ri_ac and an inductance Li.

[0057] The receiver portion 100-2 of the charging circuit 100 may include an energy storage device, the conductor 82, and an output capacitor C₂, and may define a load resistance RL. The energy storage device (not shown) may include a battery for transmitting current (e.g., receiver current I₂) through a cord or other suitable wired or wireless transmission means and through the conductor 82 of the receiver portion 100-2. The conductor 82 may define a series resistance R_2ac and an inductance L₂.

[0058] The loop equation of the charging circuit 100 may be expressed by the following equations (1) and (2)

V = Z_x\_x - ]ωΜΙ₂ (1)

where equivalent impedances of the conductor 46 and the conductor 82 are represented by Z_x and Z₂, respectively, and mutual coupling between the conductor 46 and the conductor 82 is represented by M. The mutual coupling M between the conductor 46 and the conductor 82 may be expressed by the following equation (3)

where a coupling coefficient between the self inductance L_x of the transmission portion 100-1 (e.g., of the conductor 46) and the self inductance L₂ of the receiver portion 100-2 (e.g., of the conductor 82) is represented by k and calculated by the following equation (4)

[0059] The equivalent impedances Z_x and Z₂ of the conductor 46 and the conductor 82, respectively, at the resonant frequency can be approximated by the following equations (5) and (6)

Z_S = R_L + R₂ac (6)

[0060] A resonant frequency of the charging circuit 100 is represented by ω and calculated by the following equation (7)

ω— ¹ — ¹ (7)

[0061] A power corresponding to the current is represented by PL and calculated by the following equation (8)

^L (RL+Rlac)^{2 1 L}

[0062] A power transfer efficiency of the charging circuit 100 is represented by n and calculated by the following equation (9)

ω²Μ²¾

n— (9)

(ω²Μ²)(¾+¾_αε) + (¾+Λ_1αε)(¾+Λ_2α£;)

[0063] A method of operating the wireless charging system 10, including the charging circuit 100, may include utilizing near field resonant inductive charging to transfer power from the conductor 46 to the conductor 82. In some implementations, the system 10 may transfer power from the conductor 46 to the conductor 82 at a frequency of approximately 13.56 Mhz. The charging system 10 may transfer power from the conductor 46 to the conductor 82 utilizing both inductive power transfer and resonant power transfer. In this regard, a measured non -resonant coupling coefficient K of the system 10 may be higher than a measured non-resonant coupling coefficient Kc of a standard resonant system. For example, the measured non-resonant coupling coefficient K is between 0.3 and 0.4. In some implementations, the measured non-resonant coupling coefficient K is substantially equal to 0.36. In some implementations, the measured non-resonant coupling coefficient K is substantially equal to 0.35. In this regard, the size or shape of the ferrite 42 may help to increase the value of the non-resonant coupling coefficient K by, for example, reducing the leakage of magnetic flux from the system 10.

[0064] Various implementations of the systems and techniques described herein can be realized in digital electronic and/or optical circuitry, integrated circuitry, specially designed ASICs (application specific integrated circuits), computer hardware, firmware, software, and/or combinations thereof. These various implementations can include implementation in one or more computer programs that are executable and/or interpretable on a programmable system including at least one programmable processor, which may be special or general purpose, coupled to receive data and instructions from, and to transmit data and instructions to, a storage system, at least one input device, and at least one output device.

[0065] These computer programs (also known as programs, software, software applications or code) include machine instructions for a programmable processor, and can be implemented in a high-level procedural and/or object-oriented programming language, and/or in assembly/machine language. As used herein, the terms "machine -readable medium" and "computer-readable medium" refer to any computer program product, non-transitory computer readable medium, apparatus and/or device (e.g., magnetic discs, optical disks, memory, Programmable Logic Devices (PLDs)) used to provide machine instructions and/or data to a programmable processor, including a machine-readable medium that receives machine instructions as a machine-readable signal. The term "machine -readable signal" refers to any signal used to provide machine instructions and/or data to a programmable processor.

[0066] The processes and logic flows described in this specification can be performed by one or more programmable processors executing one or more computer programs to perform functions by operating on input data and generating output. The processes and logic flows can also be performed by special purpose logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit). Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, and any one or more processors of any kind of digital computer. Generally, a processor will receive instructions and data from a read only memory or a random access memory or both. The essential elements of a computer are a processor for performing instructions and one or more memory devices for storing instructions and data. Generally, a computer will also include, or be operatively coupled to receive data from or transfer data to, or both, one or more mass storage devices for storing data, e.g., magnetic, magneto optical disks, or optical disks. However, a computer need not have such devices. Computer readable media suitable for storing computer program instructions and data include all forms of non-volatile memory, media and memory devices, including by way of example semiconductor memory devices, e.g., EPROM, EEPROM, and flash memory devices;

magnetic disks, e.g., internal hard disks or removable disks; magneto optical disks; and CD ROM and DVD-ROM disks. The processor and the memory can be supplemented by, or incorporated in, special purpose logic circuitry.

[0067] To provide for interaction with a user, one or more aspects of the disclosure can be implemented on a computer having a display device, e.g., a CRT (cathode ray tube), LCD (liquid crystal display) monitor, or touch screen for displaying information to the user and optionally a keyboard and a pointing device, e.g., a mouse or a trackball, by which the user can provide input to the computer. Other kinds of devices can be used to provide interaction with a user as well; for example, feedback provided to the user can be any form of sensory feedback, e.g., visual feedback, auditory feedback, or tactile feedback; and input from the user can be received in any form, including acoustic, speech, or tactile input. In addition, a computer can interact with a user by sending documents to and receiving documents from a device that is used by the user; for example, by sending web pages to a web browser on a user's client device in response to requests received from the web browser.

[0068] A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. Accordingly, other implementations are within the scope of the following claims.

Claims

CLAIMS What is claimed is:

1. A wireless charging system comprising:

a first conductor forming a power transmitting coil, the power transmitting coil including a plurality of first wraps of the first conductor, the plurality of first wraps including an outermost first wrap defining an outer diameter and an innermost first wrap defining an inner diameter, the outer diameter being between ten millimeters and twelve millimeters; and a second conductor forming a power receiving coil operable to receive power from the power transmitting coil, the power receiving coil including a plurality of second wraps of the second conductor, the plurality of second wraps including an outermost second wrap defining a stadium shape.

2. The wireless charging system of claim 1, wherein the plurality of first wraps are disposed about a first axis and define a first area extending in a direction perpendicular to the first axis, and the plurality of second wraps are disposed about a second axis and define a second area extending in a direction perpendicular to the second axis, and wherein a ratio of the first area to the second area is between 2.5: 1 and 5: 1.

3. The wireless charging system of either of claims 1 or 2, wherein the plurality of first wraps includes ten wraps of the first conductor.

4. The wireless charging system of any one of claims 1-3, further comprising a ferrite and a printed circuit board assembly in communication with the power transmitting coil, the ferrite disposed between the power transmitting coil and the printed circuit board assembly.

5. The wireless charging system of claim 4, wherein the printed circuit board assembly includes a processor operable to control a flow of current through the first conductor.

6. The wireless charging system of any one of claims 1-3, further comprising a printed circuit board assembly and an insert, the printed circuit board assembly coupled to the power transmitting coil and defining a first aperture and a second aperture, the insert including a proximal end and a distal end opposite the proximal end, the proximal end defining a cavity configured to receive the power receiving coil, the distal end having a first pin and a second pin and defining a recess configured to receive the power transmitting coil.

7. The wireless charging system of claim 6, wherein the recess is disposed between the first pin and the second pin.

8. The wireless charging system of either of claims 6 or 7, wherein the first pin is disposed within the first aperture and the second pin is disposed within the second aperture.

9. The wireless charging system of any one of claims 6-8, wherein the first pin is secured to the printed circuit board assembly.

10. A wireless charging system comprising:

a first conductor forming a power transmitting coil, the power transmitting coil including a plurality of first wraps of the first conductor, the plurality of first wraps disposed about a first axis and defining a first area extending in a direction perpendicular to the first axis; and

a second conductor forming a power receiving coil, the power receiving coil including a plurality of second wraps of the second conductor, the plurality of second wraps disposed about a second axis and defining a second area extending in a direction perpendicular to the second axis, a ratio of the first area to the second area being between 2.5: 1 and 5: 1.

11. The wireless charging system of claim 10, wherein the plurality of first wraps include an outermost first wrap defining an outer diameter and an innermost first wrap defining an inner diameter, the outer diameter being between ten millimeters and twelve millimeters.

12. The wireless charging system of either of claims 10 or 11, wherein the plurality of second wraps include an outermost second wrap defining a stadium shape.

13. The wireless charging system of any one of claims 10-12, wherein the first axis is parallel to the second axis.

14. The wireless charging system of any one of claims 10-13, wherein the first area is parallel to the second area.

15. The wireless charging system of any one of claims 10-14, wherein the first area defines a first shape and the second area defines a second shape that is the same as the first shape.

16. The wireless charging system of any one of claims 10-15, further comprising a ferrite and a printed circuit board assembly in communication with the power transmitting coil, the ferrite disposed between the power transmitting coil and the printed circuit board assembly.

17. The wireless charging system of claim 16, wherein the printed circuit board assembly includes a processor operable to control a flow of current through the first conductor.

18. The wireless charging system of any one of claims 10-15, further comprising a printed circuit board assembly and an insert, the printed circuit board assembly coupled to the power transmitting coil and defining a first aperture and a second aperture, the insert including a proximal end and a distal end opposite the proximal end, the proximal end defining a cavity configured to receive the power receiving coil, the distal end having a first pin and a second pin and defining a recess configured to receive the power transmitting coil.

19. The wireless charging system of claim 18, wherein the first pin is secured to the printed circuit board assembly.

20. A method of manufacturing a wireless charging system, the method comprising: providing an insert having a proximal end and a distal end opposite the proximal end, the proximal end defining a cavity configured to receive a power receiving coil, the distal end having a first pin and a second pin and defining a recess configured to receive a power transmitting coil;

providing a power transmitter assembly having a printed circuit board assembly and a power transmitting coil, the power transmitting coil defining a first aperture and a second aperture, the power transmitting coil coupled to, and in communication with, the printed circuit board assembly; positioning the power transmitting coil within the recess; and

heat staking the first pin within the first aperture and the second pin within the second aperture.