Patent ID: 12249847

DETAILED DESCRIPTION

In general, this disclosure describes devices and methods for improving the efficiency, improving the utility, and/or reducing the cost of wireless power transfer, and in particular, wireless charging of portable electronic devices. In some examples, a charging device includes a thin-film, flexible inductive antenna coil and a concentric resonant capacitor ring inductively coupled with, but not electrically powered by, the energy from the main antenna coil. Using this technique, one can obtain at least comparable power-transfer performance to charging devices that implement typical litz wire coils, without requiring additional input power, while potentially gaining the advantages of flexible, cheap, and scalable transmitter films.

This disclosure also describes techniques involving stacking multiple overlapping layers of relatively inexpensive thin-film coils, which may enable more homogenous and/or uniform magnetic fields for wireless power transfer, and allow greater tolerance for transferring power to a misaligned electronic device. Additional techniques, such as connecting the coils' terminals in parallel or implementing multiple power sources, may reduce the coils' internal resistance and/or boost power transfer efficiency. Examples in accordance with this disclosure may be applied to wireless power chargers, NFC (Near Field Communication) readers, sign decoration boards, board games, etc.

FIG.1depicts a conventional copper litz wire antenna10used for wireless power transfer. Due to their thicker wire diameter, litz wire antennas have lower internal electrical resistance, and therefore relatively high power transfer efficiency and lower charging times. For example, a typical antenna10wound from a coil of litz wire12approximately 0.8 mm in diameter may have a measured resistance of 62 mΩ and inductance of 6.2 pH at a frequency of 150 kHz. An otherwise comparable thin-film copper coil would likely have a higher internal resistance, due to the reduced cross-sectional area of the wire strand. For example, a 33-μm-thick flexible thin-film antenna, having approximately the same circumference and number of turns as coil12, may have a measured resistance of 698 mΩ and inductance of 4.5 μH at a frequency of 150 kHz. Increased resistance of thin-film coils typically results in lower power-transfer efficiency, often translating to a higher charging time compared to rigid copper litz wire. However, thin-film copper coils may be significantly cheaper and easier to produce and scale than litz wire.

FIG.2Ais an oblique view of a thin-film antenna20in accordance with various techniques of this disclosure. In some examples, antenna20includes a single-layer loop or coil of copper wire22, in the form of a thin-film, that is either printed or etched onto a substrate. In some examples, antenna20has an outer diameter of 4.8 cm, defining outer circumference26. Antenna20may also have an inner diameter defining inner circumference24. In some examples, antenna20is excited by 700 mA input current, which thereby produces an electromagnetic field between the inner circumference24and the outer circumference26.

FIG.2Bdepicts a computer-simulation technology (CST) model and electromagnetic (EM) simulation of thin-film antenna20depicted inFIG.2A, having diameter 4.8 cm and excited by 700 mA input current. The simulation ofFIG.2Billustrates the power density of the electromagnetic field in the region defined by the antenna20. As shown inFIG.2B, the power density output by antenna20is relatively low in the area of the plane within the coil, and drops to approximately zero in the region of the plane immediately outside the coil. If a device that is to receive power from the coil (i.e., a “power-receiving device”, such as a mobile phone) is placed on the plane of the coil, power transfer from the coil to the power-receiving device will be relatively low, since the power density output, as illustrated inFIG.2B, is relatively low within the plane of the coil. This indicates, for a system that recharges a portable electronic device (PED) by placing the PED on the coil, a relatively low charging efficiency, resulting in relatively long charging times for the PED, and even longer charging times when the PED is misaligned with the coil.

FIG.3Ais an oblique view of a thin-film antenna30having main antenna coil32and inner resonance ring38, in accordance with various techniques of this disclosure. In the example shown, main coil32is composed of multiple loops (for example, ten loops) of a single layer of copper printed or etched onto a substrate. The coil defines inner circumference34and outer circumference36.

In some examples, antenna30includes resonating loop structure38(referred to herein as “resonance loop”, “resonance ring”, “resonating capacitor loop”, or “resonant capacitor ring”), where resonance loop38includes a capacitor tuned to resonate at or near the resonance frequency of main antenna coil32. In some examples, resonance loop38is substantially circular, like a ring-shape. In other examples, resonance loop38may have other shapes, such as an oval. In the example depicted inFIG.3A, resonance ring38resonates at the Wireless Power Consortium's “Qi” standard charging frequency of 170 kHz. In some examples, resonance ring38may be at least partially composed of copper. In some examples, but not all examples, resonance ring38is substantially coplanar and concentric with main antenna coil32. In some examples, such as the configuration depicted inFIG.3A, resonance ring38has a circumference smaller than inner circumference34. Resonating ring structure38does not require external power input, but is excited through inductive coupling with the EM signal of the main inductor coil32.

FIG.3Bdepicts a CST model and EM simulation of thin-film antenna30depicted inFIG.3A, having outer diameter 4.8 cm excited by 700 mA input current. Compared to antenna20ofFIG.2A, the magnetic field strength of antenna30is significantly stronger over a larger area, particularly in the central region inside of resonance ring38. This increase in magnetic field strength, which would occur for both rigid copper wire and flexible copper film implementations, may be sufficient to enable the practical use of flexible copper films for wireless charging of PEDs, such as cell phones.

FIG.4Ais an oblique view of a thin-film antenna40having main antenna coil42and outer resonance ring48, in accordance with various techniques of this disclosure. Antenna40includes main coil42, composed of multiple loops (for example, ten loops) of a single layer of copper printed or etched onto a substrate. The coil defines inner circumference44and outer circumference46.

In some examples, antenna40includes resonating ring structure48, which resonates at the Qi standard frequency of 170 kHz. In some examples, resonance ring48is substantially coplanar and concentric with main antenna coil42. In the configuration depicted inFIG.4A, resonating ring48has a circumference larger than outer circumference46. Resonating ring structure48does not require external power input, but is excited through inductive coupling with the EM signal of the main inductor coil42.

FIG.4Bdepicts a CST model and EM simulation of thin-film antenna40depicted inFIG.4A, having outer diameter 4.8 cm excited by 700 mA input current. Compared to antenna20ofFIG.2A, the magnetic field strength of antenna40is significantly stronger over a larger area, and substantially stronger in the outer region near and/or within resonance ring48. This increase in magnetic field strength may be sufficient to enable the practical use of flexible copper films for wireless charging of PEDs. Additionally, the example illustrated inFIG.4Amay, if used as a charging device, enable a greater tolerance for misalignment of a PED with charging coil42(i.e., comparable charging efficiency even when the PED is not sufficiently aligned or within the plane of the antenna40), since the outer ring results in a strong magnetic field distributed over a larger area compared to the magnetic fields depicted inFIGS.2B and3B.

FIG.5Ais an oblique view of a thin-film antenna50having main antenna coil52, inner resonance ring58, and outer resonance ring59, in accordance with various techniques of this disclosure. Antenna50includes main coil52, composed of multiple loops (for example, ten loops) of a single layer of copper printed or etched onto a substrate. The coil defines inner circumference54and outer circumference56.

In some examples, antenna50includes inner resonating ring structure58, which resonates at the Qi standard frequency of 170 kHz. In some examples, resonance ring58is substantially coplanar and concentric with main antenna coil52. In the configuration depicted inFIG.5A, inner resonating ring58has a circumference smaller than inner antenna circumference54. Inner resonating ring structure58does not require external power input, but is excited through inductive coupling with the EM signal of the main inductor coil52.

In some examples, antenna50includes outer resonating ring structure59. Outer resonating ring59may be a resonant capacitor ring configured to resonate at or near the resonating frequency of main antenna coil52, for example, the Qi standard frequency of 170 kHz. In some examples, outer resonance ring59is coplanar and concentric with main antenna coil52. In the example configuration depicted inFIG.5A, outer resonating ring59has a circumference larger than outer antenna circumference56. Outer resonating ring structure59does not require external power input, but is excited through inductive coupling with the EM signal of main inductor coil52.

FIG.5Bdepicts a CST model and EM simulation of thin-film antenna50depicted inFIG.5A, having outer diameter 4.8 cm excited by 700 mA input current. Compared to antenna20ofFIG.2A, the magnetic field strength of antenna50is significantly stronger over a larger area, and almost uniformly distributed. This increase in magnetic field strength may be sufficient to enable the practical use of flexible copper films for wireless charging of PEDs, and for other applications, such as wireless power transfer for other devices, or for use in decorative boards, lighting, or other applications. Additionally, the example illustrated inFIG.5Amay, if used as a charging device, enable a greater tolerance for misalignment of a PED with charging coil52(i.e., comparable charging efficiency even when the PED is not sufficiently aligned), since outer resonance ring59results in a strong magnetic field distributed over a larger area compared to the fields depicted inFIGS.2B and3B.FIG.5Bshows significant improvement in performance in terms of magnetic field strength over a large area indicating that multiple resonant rings may boost performance of thin-film antennas for wireless power transfer applications.

FIG.6depicts a system60having movable resonating capacitor rings for wireless power transfer to electronic devices, in accordance with various techniques of this disclosure. In the example depicted inFIG.6, system60includes an object62having a substantially planar surface, such as a conference table, desk, workbench, or similar structure. System60may include coil antenna64disposed around the outer rim of planar surface62. A power management system (shown near the center of object62inFIG.6) may be within, under, or otherwise connected to object62to provide power to the coil antenna64. For example, antenna64may either include a standard litz copper wire coil embedded in surface62, or alternatively, a thin-film copper coil printed on top of, or embedded underneath the top of, surface62.

System60may further include one or more movable articles or other objects, such as coasters66, configured to be placed at any point on the top of planar surface62. Each of movable coasters66may include one or more embedded resonating capacitor rings, configured to concentrate the electromagnetic field produced by coil antenna64into the region defined by the resonating capacitor ring embedded within the coaster66. In some examples, articles, objects, or coasters66may be flat and relatively thin.

In one example, conference table62includes a planar surface surrounded by one or more people seated at the outer rim. Each of the people, such as attendees of a meeting, may carry one or more portable electronic devices (PEDs), such as a smartphone, PDA, laptop, computer mouse, etc. Each attendee may place a PED on one of coasters66, which, when configured with a resonating capacitor ring, concentrates the electromagnetic field of antenna64to the region of the coaster, enabling wireless charging of the PED when placed on coaster66. In some examples, table62may operate in a “low-power mode”, wherein the electromagnetic field produced by antenna64may be either not strong enough or not concentrated enough to power a PED without the use of a coaster66, allowing for reduced energy consumption and reduction of wasted energy.

FIG.7depicts a system having multiple antennae and movable resonating capacitor rings for wireless power transfer in accordance with various techniques of this disclosure. In the example depicted inFIG.7, system70includes an object72having a substantially planar surface, such as a conference table, desk, workbench, or similar structure. System70may include multiple coil antennae74disposed around various sections of planar surface72. For example, antenna74may either include a standard litz copper wire coil embedded in surface72, or alternatively, a thin-film copper coil printed on top of, or embedded underneath the top of, surface72.

System70may further include one or more movable articles, objects, mouse pads, or coasters76, configured to be or capable of being placed at any point on the top of planar surface72. Each of movable coasters76may include one or more embedded resonating capacitor rings, configured to concentrate the electromagnetic field produced by coil antenna74into the region defined by the resonating capacitor ring embedded in the coaster76.

In one example, conference table72includes a planar surface surrounded by one or more people seated at the outer rim. Each of the people, such as attendees of a meeting, may carry one or more portable electronic devices (PEDs), such as a smartphone, PDA, laptop, computer mouse, etc. Each attendee may place a PED on one of coasters76, which concentrates the electromagnetic field of antenna74to the region defined by the coaster, enabling wireless charging of the PED placed on coaster76. In some examples, table72may operate in a “low-power mode”, wherein the electromagnetic field produced by antenna74may be either not strong enough or not concentrated enough to power a PED without the use of a coaster76, allowing for reduced power consumption and reduction of wasted energy.

FIG.8depicts a system80having multiple antennae and movable resonating capacitor rings for wireless power transfer in accordance with various techniques of this disclosure. In the example depicted inFIG.8, system80includes an object82, which may have a separate or integrated power management system. Object82may be, or may be part of a conference table, desk, workbench, wall, bar, etc. System80may include multiple coil antennae84, with a separate antenna84disposed around each “seat” along the rim of object82. For example, antenna84may either include a standard litz copper wire coil embedded in surface82, or alternatively, a thin-film copper coil printed on top of, or embedded underneath the top of, object82.

Each of individual antennae84may include one or more resonating capacitor rings86configured to focus, amplify, and/or redistribute the antenna's magnetic field, so as to improve the efficiency of wireless power transfer to an electronic device placed on top of the antenna. For example, by including one or more resonating capacitor rings, one of antennae84may sufficiently alter the antenna's magnetic field to power a computer mouse placed on or near the antenna. In another example, one or more resonating capacitor rings may enable one of antennae84to charge a battery of a mobile phone placed over the antenna. In the example shown inFIG.8, resonance ring86is depicted as the innermost rectangle within antenna84, although resonance ring86may also be disposed around the outside of antenna84, and may take other shapes, such as a circle.

Although some examples are described herein in terms of multiple circular loops of conductive thin-film material and concentric circular resonant rings of conductive thin-film material, other implementations in accordance with one or more aspects of the present disclosure are possible. For example, conventional copper litz wire or other conductive material may be used to implement either the powered conductive loops or the passive resonant loops, or both. Also, the circular loops of conductive material and/or the circular resonant ring of conductive material need not be in a circular or oval shape, but may be in other shapes, including rectangular or other shapes. Further, although the resonant rings are primarily illustrated in some examples as being concentric with the powered loops of conductive materials, the resonant ring (or resonant loop) may be disposed anywhere within the interior of the loops of conductive material. Still further, although multiple loops of conductive material may be beneficial in generating a more powerful magnetic field, using multiple loops of conductive material is not necessarily required, and one or more aspects of the present disclosure may be implemented with only a single loop.

FIG.9Ais an oblique view of a single-layer thin-film antenna110, in accordance with various techniques of this disclosure. Antenna110includes thin-film coil112, which may be printed or etched onto a substrate. In the example depicted inFIG.9A, coil112consists of four loops, although a thin-film coil may include any number of loops. Coil112defines an interior region116. Antenna110also includes terminals114, to which a power source may be connected.

Typical wireless power transfer applications implement a single-layer circular coil made of copper litz wire. Thin-film flexible coils, such as coil112, are not typically used, as their smaller wire thickness often corresponds to a higher internal resistance, resulting in relatively low power-transfer efficiency compared to copper litz wire.

FIG.9Bis a computer-simulation technique (CST) model and electromagnetic (EM) simulation of the thin-film antenna110depicted inFIG.9A, in accordance with various techniques of this disclosure. As shown inFIG.9B, a single-layer thin-film antenna, with its relatively high internal resistance, generates a relatively weak magnetic field in the area immediately surrounding the coil112, and essentially zero magnetic field everywhere else, such as the interior region116. Accordingly, a single-layer thin-film antenna is not ideal for wireless power transfer applications. Additionally, because the generated magnetic field is so locally confined to the region immediately at, near, or surrounding the coil112, even a slight misalignment of an electronic device with respect to the optimal placement of the device relative to the coil may result in significant decrease in power transferred to the device.

FIG.10is an oblique view of a dual-layer stacked thin-film antenna120, in accordance with various techniques of this disclosure. Antenna120includes two thin-film coils122A and122B (collectively, coils122), each of which may be printed or etched onto a substrate. In the example depicted inFIG.10, each of coils122includes four loops, although a thin-film coil may include any number of loops. Because coils122A and122B are approximately the same size and substantially overlap each other, coils122define a single interior region126.

Each of coils122includes a pair of terminals124, to which a power source may be connected. In some examples, each pair of terminals may be connected to a different power source. In other examples, each pair of terminals may be connected to a common power source. When connected to a common power source, each pair of terminals may be electrically connected in parallel to each other pair. By electrically connecting each pair of terminals in parallel, the overall resistance of antenna120is reduced by the number of coils122, according to Ohm's law. For example, for the example depicted inFIG.10having two coils122:
1/Rtotal=1/R1+1/R2
For two approximately equal coils122, the resistance of coil122A equals the resistance of coil122B (i.e., R1=R2):
1/Rtotal=2/R1
Rtotal=R1/2,

Therefore, for an antenna120with two coils122, the total resistance is theoretically halved, significantly increasing the power transfer efficiency of antenna120in the region immediately surrounding the coils122. However, interior region126may still experience little to no magnetic field strength because the inductance is correspondingly reduced, resulting in very low tolerance for transferring power to an electronic device that is not substantially aligned with coils122. Although the total inductance of antenna120may similarly be halved by connecting terminals124in parallel, a higher inductance value may be attained by increasing the number of loops, changing the width of the conducting line, and/or decreasing the spacing of coils122.

The electrical resistance of antenna120may be reduced even further by increasing the thickness of each of thin-film coils122. However, increasing the thickness may increase the cost of production, and reduce the flexibility of each coil.

FIG.11is an oblique view of two pairs of single-layer thin-film antennae130A and130B prior to stacking, in accordance with various techniques of this disclosure. Certain arrangements of stacked layers of thin-film coils may enable a wireless power transfer antenna to generate a substantially uniform magnetic field across its interior region by using multiple coils to divide the single large interior region into multiple smaller ones. For example, antennae pair130A includes two thin-film coils132A and132B, each coil defining an interior space136A and136B, respectively. An additional space136C is provided between the two antennae.

Similarly, antennae pair130B includes two thin-film coils132C and132D, each coil defining an interior region136D and136E, respectively. An additional space136F is provided between the two antennae. In the example depicted inFIG.11, each of coils132A-132D has four loops, although coils123may include any number of loops. By stacking antennae pairs130A and130B (e.g., as in the arrangement depicted inFIG.12A, described below), a combined single antenna may be produced having a substantially evenly-distributed magnetic field across its interior region, allowing for efficient power transfer to an electric device, even when the electronic device is not substantially aligned with the perimeter of the coil.

FIG.12Ais an oblique view of a dual-layer stacked thin-film antenna140, in accordance with various techniques of this disclosure. Antenna140may be manufactured by producing two pairs of thin-film coils on substrates, such as coil pairs130A and130B depicted inFIG.11, stacking one substrate on top of the other, and electrically connecting the coils' antenna terminals144in parallel. In this particular arrangement, the six interior spaces136A-136F depicted inFIG.11may be further divided into nine smaller interior spaces146A-146I. This particular arrangement may prevent antenna140from having a single large interior region that is largely devoid of magnetic field, and instead, more-evenly distributes the magnetic field across the interior, as depicted inFIG.12B.

In some example applications, antenna140may be embedded within a mouse pad (or similar object) to transfer power to a wireless computer mouse or other device. In another example, antenna140may be used to charge a battery of a portable electronic device, such as a smartphone, laptop, or tablet.

FIG.12Bis a CST model and EM simulation of the dual-layer stacked thin film antenna depicted inFIG.12A, in accordance with various techniques of this disclosure. As illustrated inFIG.12B, the configuration of antenna140inFIG.12Aresults in nine sub-regions146A-146I of varying magnetic field strengths. For example, sub-regions146A,146C,146E,146G, and146I may feature relatively robust magnetic field strengths, due to the constructive interference of the electric currents in those regions. Sub-regions146B and146H may feature moderate magnetic field strengths, due to the influence of both constructive and destructive interference of electric currents at their perimeters. Sub-regions146D and146F may feature relatively weaker magnetic field strengths, due to the destructive interference of opposing electric currents at their perimeters. Such relatively weaker sub-regions might not be present in all examples in accordance with one or more aspects of this disclosure—alternative antenna designs (for example, adding a third stacked layer to the antenna) may result in even higher uniformity of magnetic field distribution.

FIG.13depicts an example application of stacked thin-film antennae in accordance with various techniques of this disclosure. In the example depicted inFIG.13, system150includes an object152having a substantially planar surface, such as a wall, whiteboard, or smartboard, (or if oriented differently, a conference table, desk, workbench, or similar structure). A perimeter of object152may define an interior region158. In some examples, interior region158may be substantially rectangular, or any other shape, such as circular.

Although not depicted inFIG.13, system150may include a plurality of thin-film coil antennae embedded within the surface of object152, configured to produce a magnetic field, for example, for wirelessly transferring power to articles placed near the surface of object150. The thin-film antennae may at least partially overlap one another, for example, to divide the interior region158of object152into a plurality of smaller sub-regions, so as to more-evenly distribute a magnetic field across the surface.

System150may further include one or more movable articles154, configured to be placed at various points on the surface of object152. In the example ofFIG.13, articles154are depicted as sticky notes, such as Post-it® Notes produced by 3M Corporation of Maplewood, Minn., that are configured to receive power from the antennae embedded within the surface of object152. In general, movable articles154may be any portable electronic device configured to wirelessly receive power from the antennae embedded within the surface of object152. For example, movable articles154may be light-emitting devices, computer mice, mobile phones, laptops, tablets, or any other portable electronic device.

In one example, such as the example depicted inFIG.13, object152includes an interactive whiteboard, and movable articles154include a plurality of sticky notes. Sticky notes154may include one or more LEDs configured to emit light (as indicated by sticky note156) by wirelessly receiving power from a plurality of stacked thin-film antenna embedded within the surface of whiteboard152. Because the thin-film antennae may homogenously or relatively uniformly distribute a magnetic field across the surface of whiteboard154, sticky note156may emit light when placed anywhere on the surface. In some examples, whiteboard152may be configured to wirelessly send and receive digital information from articles154, for example, information displayed as text on a sticky note154.