Wireless power transfer systems with shield openings

In a first aspect, the disclosure features apparatuses for wireless power transfer, the apparatuses including a plurality of magnetic elements joined together to form a magnetic component extending in a plane, where discontinuities in the magnetic component between adjacent magnetic elements define gaps in the magnetic component, a coil including one or more loops of conductive material positioned, at least in part, on a first side of the plane. The apparatuses include a conductive shield positioned on a second side of the plane and which includes one or more openings positioned relative to the gaps.

TECHNICAL FIELD

This disclosure relates to wireless power transfer.

BACKGROUND

Energy can be transferred from a power source to a receiving device using a variety of known techniques such as radiative (far-field) techniques. For example, radiative techniques using low-directionality antennas can transfer a small portion of the supplied radiated power, namely, that portion in the direction of, and overlapping with, the receiving device used for pick up. In this example, most of the energy is radiated away in directions other than the direction of the receiving device, and typically the transferred energy is insufficient to power or charge the receiving device. In another example of radiative techniques, directional antennas are used to confine and preferentially direct the radiated energy towards the receiving device. In this case, an uninterruptible line-of-sight and potentially complicated tracking and steering mechanisms are used.

Another approach is to use non-radiative (near-field) techniques. For example, techniques known as traditional induction schemes do not (intentionally) radiate power, but use an oscillating current passing through a primary coil, to generate an oscillating magnetic near-field that induces currents in a near-by receiving or secondary coil. Traditional induction schemes can transfer modest to large amounts of power over very short distances. In these schemes, the offset tolerances between the power source and the receiving device are very small. Electric transformers and proximity chargers use these traditional induction schemes.

SUMMARY

This disclosure relates to wireless transfer systems utilizing wireless power transfer of power from a power transmitting apparatus to a power receiving apparatus. To achieve high power transfer efficiency, the power transmitting apparatus and/or the power receiving apparatus can include a magnetic component and a shield to facilitate the power transfer. Particularly, it can be advantageous to have a large magnetic component in transferring high power for some applications. However, manufacturing the large magnetic component as a single monolithic piece can be impractical or expensive because materials such as ferrites can be difficult to fabricate and/or easily break. Thus, the large magnetic component can instead be formed by combining smaller magnetic elements together. In this approach, the magnetic elements are typically joined across one or more gaps, which can be filled with air or adhesive for connecting the magnetic elements. Such gaps can be problematic, however, because magnetic fields can be concentrated at regions of the gaps. The concentrated magnetic fields can penetrate the nearby shield and other materials or structures and induce eddy currents, thereby leading to losses in the systems and reductions in the amount of power transferred. To address such issues, this disclosure describes a variety of configurations of magnetic components and shields to mitigate losses induced by penetration of magnetic fields into the shields, for example, by aligning openings of the shields to gaps of the magnetic components.

In a first aspect, the disclosure features apparatuses for wireless power transfer, the apparatuses including a plurality of magnetic elements joined together to form a magnetic component extending in a plane, where discontinuities in the magnetic component between adjacent magnetic elements define gaps in the magnetic component, and a coil including one or more loops of conductive material positioned, at least in part, on a first side of the plane. The apparatuses include a conductive shield positioned on a second side of the plane and which the shield includes one or more openings positioned relative to the gaps.

Embodiments of the apparatuses can include any one or more of the following features.

The openings can be respectively aligned with corresponding ones of the gaps. The one or more openings can be positioned relative to the gaps to reduce interactions between magnetic flux crossing the discontinuities and the conductive shield.

The coil can be positioned entirely on the first side of the plane. The one or more loops of conductive material can wrap around the magnetic component. The conductive shield can be substantially parallel to the plane. The one or more openings can extend entirely through the shield.

The plane can extend in orthogonal first and second directions, and where the one or more loops of conducting material wrap around a third direction perpendicular to the first and second directions (i.e., perpendicular to the plane). The gaps can include a first gap having a longest dimension extending in the first direction, and the one or more openings can include a first opening having a longest dimension extending in a direction substantially parallel to the first direction. The first gap can have a maximum width measured in a direction parallel to the second direction, the first opening can have a maximum width measured in a direction parallel to the second direction, and the maximum width of the first opening can be larger than the maximum width of the first gap. A ratio of the maximum width of the first opening to a characteristic size of the magnetic component can be 1:10 or less.

During operation, the coil can generate a magnetic field that oscillates in a direction parallel to the second direction. A first one of the gaps can correspond to a spacing between magnetic elements in a direction parallel to the second direction, and a first one of the one or more openings can be aligned with the first one of the gaps and include a width that extends in a direction parallel to the second direction. Each of the gaps can correspond to a spacing between magnetic elements in a direction parallel to the second direction, and each of the one or more openings can be aligned with a corresponding one of the one or more gaps and includes a width that extends in a direction parallel to the second direction.

The coil can be electrically isolated from the conductive shield.

The one or more loops can include a first plurality of loops concentric about a first axis and a second plurality of loops concentric about a second axis, where the first and second axes are parallel to the third direction. The first plurality of loops can be wound in a first concentric direction about the first axis, and the second plurality of loops can be wound about the second axis in a second concentric direction opposite to the first concentric direction, when measured from an end of the first plurality of loops towards an end of the second plurality of loops. During operation, the coil can generate a magnetic field within the magnetic component that oscillates in a direction parallel to the second direction.

The plurality of magnetic elements can form an array. The plurality of magnetic elements can include 4 or more magnetic elements. At least one of the gaps can include air spaces. At least one of the gaps can include a dielectric material positioned between the magnetic elements. For example, the dielectric material can include an adhesive material.

At least some of the plurality of magnetic elements can be formed of a ferrite material. The ferrite material can include at least one material selected from the group consisting of MnZn-based materials, NiZn-based materials, amorphous cobalt-based alloys, and nanocrystalline alloys.

The coil can be configured to wirelessly transfer power to, or receive power from, another coil. A minimum distance between a surface of the magnetic component and the shield can be 1 mm or less.

At least one of the openings can include lateral surfaces that are angled with respect to the plane.

At least one of the openings can include a triangular cross-sectional profile. At least one of the openings can include a trapezoidal cross-sectional profile. At least one of the openings can include a cross-sectional profile having one or more curved edges.

At least one of the gaps can be with a magnetic material comprising a magnetic permeability different from a magnetic permeability of the plurality of magnetic elements.

In another aspect, the disclosure features apparatuses for wireless power transfer, the apparatuses including a plurality of magnetic elements joined together to form a magnetic component extending in a plane, where discontinuities in the magnetic component between adjacent magnetic elements define gaps in the magnetic component. The apparatuses include a coil comprising one or more loops of conductive material positioned, at least in part, on a first side of the plane, and a conductive shield positioned on a second side of the plane and where the shield includes one or more depressions formed in a surface of the shield facing the magnetic component. Each of the one or more depressions is positioned relative to the gaps.

Embodiments of the apparatuses can include any one or more of the following features.

The one or more depressions can be respectively aligned with corresponding ones of the gaps. The one or more depressions can be positioned relative to the gaps to reduce interactions between magnetic flux crossing the discontinuities and the conductive shield. At least one of the depressions can form an opening that extends entirely through a thickness of the shield.

The coil can be positioned entirely on the first side of the plane. The plane can extend in orthogonal first and second directions, where the one or more loops of conducting material can wrap around a third direction perpendicular to the first and second directions (i.e., perpendicular to the plane). The one or more loops of conductive material wrap around the magnetic component. The conductive shield can be substantially parallel to the plane.

The one or more depressions can include lateral surfaces that are angled with respect to a surface of the shield facing the magnetic component. A width of the one or more depressions measured at the surface of the shield facing the magnetic component can be larger than a width of the one or more depressions measured at another location between the lateral surfaces.

At least one of the depressions can include a cross-sectional profile having a triangular shape. At least one of the depressions can include a cross-sectional profile having a trapezoidal shape. At least one of the depressions can include a cross-sectional profile having one or more curved edges. At least one of the depressions can correspond to a curved groove formed in the shield.

The one or more loops can include a first plurality of loops concentric about a first axis and a second plurality of loops concentric about a second axis parallel to the first axis, and the first and second axes can be orthogonal to the plane of the magnetic component. The first plurality of loops can be wound in a first concentric direction about the first axis, and the second plurality of loops can be wound about the second axis in a second concentric direction opposite to the first concentric direction, when measured from an end of the first plurality of loops towards an end of the second plurality of loops.

During operation, the coil can generate a magnetic field within the magnetic component that oscillates in a direction parallel to a width of at least one of the depressions.

The gaps can include a first gap having a longest dimension extending in a first direction, and the depressions can include a first depression having a longest dimension extending in a direction substantially parallel to the first direction. The first gap can have a maximum width measured in a direction perpendicular to the longest dimension of the first gap. The first depression can have a maximum width measured in a direction perpendicular to the longest dimension of the first depression, and the maximum width of the first opening can be larger than the maximum width of the first gap.

Each of the gaps can correspond to a spacing between magnetic elements in a direction perpendicular to the first direction, and each of the depressions can be aligned with a corresponding one of the gaps and can have a width that extends in a direction perpendicular to the first direction.

The plurality of magnetic elements can form an array. The plurality of magnetic elements can include 4 or more magnetic elements.

At least one of the one or more gaps can include air spaces. At least one of the one or more gaps can include a dielectric material positioned between the magnetic elements. For example, the dielectric material can include an adhesive material.

At least some of the plurality of magnetic elements can be formed of a ferrite material. The ferrite material can include at least one material selected from the group consisting of MnZn-based materials, NiZn-based materials, amorphous cobalt-based alloys, and nanocrystalline alloys.

The coil can be configured to wirelessly transfer power to, or receive power from, another coil.

A ratio of the maximum width of the first depression to a characteristic size of the magnetic component can be 1:10 or less. A minimum distance between a surface of the magnetic component and the shield can be 1 mm or less. At least one of the gaps is filled with magnetic material can have a magnetic permeability different from a magnetic permeability of the magnetic elements.

In another aspect, the disclosure features methods for wirelessly transferring power using apparatuses, the methods including wirelessly transferring power from a power transmitting apparatus to a power receiving apparatus, where at least one of the power transmitting apparatus and the power receiving apparatus includes: a magnetic component extending in a plane and formed from a plurality of magnetic elements joined together, where discontinuities in the magnetic component between adjacent magnetic elements define gaps in the magnetic component, a coil including one or more loops of conductive material positioned, at least in part, on a first side of the plane, and a conductive shield positioned on a second side of the plane and comprising one or more openings positioned relative to the gaps.

The power transmitting apparatus and the power receiving apparatus can each include the magnetic component, the coil, and the conductive shield.

Embodiments of the apparatuses and methods can also include any other features disclosed herein, including features disclosed in connection with other apparatuses and methods, in any combination as appropriate.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. In case of conflict with publications, patent applications, patents, and other references mentioned or incorporated herein by reference, the present disclosure, including definitions, will control. Any of the features described above may be used, alone or in combination, without departing from the scope of this disclosure. Other features, objects, and advantages of the systems and methods disclosed herein will be apparent from the following detailed description and figures.

DETAILED DESCRIPTION

Introduction

FIG. 1is a schematic diagram of a wireless power transfer system100. System100includes a power transmitting apparatus102and a power receiving apparatus104. Power transmitting apparatus102is coupled to power source106through a coupling105. In some embodiments, coupling105is a direct electrical connection. In certain embodiments, coupling105is a non-contact inductive coupling. In some embodiments, coupling105can include an impedance matching network (not shown inFIG. 1). Impedance matching networks and methods for impedance matching are disclosed, for example, in commonly owned U.S. patent application Ser. No. 13/283,822, published as US Patent Application Publication No. 2012/0242225, the entire contents of which are incorporated herein by reference.

In similar fashion, power receiving apparatus104is coupled to a device108through a coupling107. Coupling107can be a direct electrical connection or a non-contact inductive coupling. In some embodiments, coupling107can include an impedance matching network, as described above.

In general, device108receives power from power receiving apparatus104. Device108then uses the power to do useful work. In some embodiments, for example, device108is a battery charger that charges depleted batteries (e.g., car batteries). In certain embodiments, device108is a lighting device and uses the power to illuminate one or more light sources. In some embodiments, device108is an electronic device such as a communication device (e.g., a mobile telephone) or a display. In some embodiments, device108is a medical device which can be implanted in a patient.

During operation, power transmitting apparatus102is configured to wirelessly transmit power to power receiving apparatus104. In some embodiments, power transmitting apparatus102can include a source coil, which can generate oscillating fields (e.g., electric, magnetic fields) when electrical currents oscillate within the source coil. The generated oscillating fields can couple to power receiving apparatus104and provide power to the power receiving apparatus through the coupling. To achieve coupling between power transmitting apparatus102and power receiving apparatus104, the power receiving apparatus104can include a receiver coil. The oscillating fields can induce oscillating currents within the receiver coil. In some embodiments, either or both of the source and receiver coils can be resonant. In certain embodiments, either or both of the source and receiver coils can be non-resonant so that the power transfer is achieved through non-resonant coupling.

In certain embodiments, the system100can include a power repeating apparatus (not shown inFIG. 1). The power repeating apparatus can be configured to wirelessly receive power from the power transmitting apparatus102and wirelessly transmit the power to the power receiving apparatus104. The power repeating apparatus can include similar elements described in relation to the power transmitting apparatus102and the power receiving apparatus104above.

System100can include an electronic controller103configured to control the power transfer in the system100, for example, by directing electrical currents through coils of the system100. In some embodiments, the electronic controller103can tune resonant frequencies of resonators included in the system100, through coupling109. The electronic controller103can be coupled to one or more elements of the system100in various configurations. For example, the electronic controller103can be only coupled to power source106. The electronic controller103can be coupled to power source106and power transmitting apparatus102. The electronic controller103can be only coupled to power transmitting apparatus102. In some embodiments, coupling109is direct connection. In certain embodiments, coupling109is a wireless communication (e.g., radio-frequency, Bluetooth communication). The coupling109between the electronic controller103can depend on respective one or more elements of the system100. For example, the electronic controller103can be directly connected to power source106while wirelessly communicating with power receiving apparatus104.

In some embodiments, the electronic controller can configure the power source106to provide power to the power transmitting apparatus102. For example, the electronic controller can increase the power output of the power source106sent to the power transmitting apparatus102. The power output can be at an operating frequency, which is used to generate oscillating fields by the power transmitting apparatus102.

In certain embodiments, the electronic controller103can tune a resonant frequency of a resonator in the power transmitting apparatus102and/or a resonant frequency of a resonator in the power receiving apparatus104. By tuning resonant frequencies of resonators relative to the operating frequency of the power output of the power source106, the efficiency of power transfer from the power source106to the device108can be controlled. For example, the electronic controller103can tune the resonant frequencies to be substantially the same (e.g., within 0.5%, within 1%, within 2%) to the operating frequency to increase the efficiency of power transfer. The electronic controller103can tune the resonant frequencies by adjusting capacitance values of respective resonators. To achieve this, for example, the electronic controller103can adjust a capacitance of a capacitor connected to a coil in a resonator. The adjustment can be based on the electronic controller103's measurement of the resonant frequency or based on wireless communication signal from the apparatuses102and104. In certain embodiments, the electronic controller103can tune the operating frequency to be substantially the same (e.g., within 0.5%, within 1%, within 2%) to the resonant frequencies of the resonators.

In some embodiments, the electronic controller103can control an impedance matching network in the system100to optimize or de-tune impedance matching conditions in the system100, and thereby control the efficiency of power transfer. For example, the electronic controller103can tune capacitance of capacitors or networks of capacitors included in the impedance matching network connected between power transmitting apparatus102and power source106. The optimum impedance conditions can be calculated internally by the electronic controller103or can be received from an external device.

In some embodiments, wireless power transfer system100can utilize a source resonator to wirelessly transmit power to a receiver resonator. For example, power transmitting apparatus102can include a source resonator that includes a source coil, and power receiving apparatus104can include a receiver resonator that includes a receiver coil. Power can be wirelessly transferred between the source resonator and the receiver resonator.

In this disclosure, “wireless energy transfer” from one coil (e.g., resonator coil) to another coil (e.g., another resonator coil) refers to transferring energy to do useful work (e.g., electrical work, mechanical work, etc.) such as powering electronic devices, vehicles, lighting a light bulb or charging batteries. Similarly, “wireless power transfer” from one coil (e.g., resonator coil) to another resonator (e.g., another resonator coil) refers to transferring power to do useful work (e.g., electrical work, mechanical work, etc.) such as powering electronic devices, vehicles, lighting a light bulb or charging batteries. Both wireless energy transfer and wireless power transfer refer to the transfer (or equivalently, the transmission) of energy to provide operating power that would otherwise be provided through a wired connection to a power source, such as a connection to a main voltage source. Accordingly, with the above understanding, the expressions “wireless energy transfer” and “wireless power transfer” are used interchangeably in this disclosure. It is also understood that, “wireless power transfer” and “wireless energy transfer” can be accompanied by the transfer of information; that is, information can be transferred via an electromagnetic signal along with the energy or power to do useful work.

Multiple-Element Magnetic Components

FIG. 2is a schematic diagram of an example of a power transmitting apparatus102including a coil210, a magnetic component220and a shield229according to coordinate291. The coil210includes a plurality of loops and can be connected to a capacitor (not shown). The coil210can be formed of a first conductive material. In some embodiments, the coil210can be a litz wire. For example, litz wire can be used for operation frequencies of lower than 1 MHz. In certain embodiments, the coil210can be a solid core wire or conducting layers (e.g., copper layers) in a printed circuit board (PCB). For example, such solid core wire or conducting layers can be used for operation frequencies of 1 MHz or higher. The magnetic component220is positioned between the coil210and the shield229. The magnetic component220can guide a magnetic flux induced by the plurality of loops of the coil210. The presence of the magnetic component220can lead to an increase of a magnetic flux density generated by the coil210in a region adjacent to the coil210when oscillating electrical currents circulate in the coil210, compared to the case without the magnetic component220.

The shield229(e.g., a sheet of electrically conductive material) can be positioned adjacent to the source resonator. The shield229can be formed of a second conductive material. For example, the shield229can be formed from a sheet of material such as copper, silver, gold, iron, steel, nickel and/or aluminum. Typically, the shield229acts to shield the resonator from loss-inducing objects (e.g., metallic objects). Further, in some embodiments, the shield229can increase coupling of the source resonator to another resonator by guiding magnetic field lines in the vicinity of the source resonator. For example, energy loss from aberrant coupling to loss-inducing objects can be reduced by using the shield229to guide magnetic field lines away from the loss-inducing objects.

WhileFIG. 2shows power transmitting apparatus102, it should be understood that a power receiving apparatus (e.g., power receiving apparatus104inFIG. 1) or power repeating apparatus can include similar elements. For example, power receiving apparatus104can include a coil, a capacitor and a magnetic component. A shield can be positioned adjacent to these elements.

Magnetic components can include magnetic materials. Typical magnetic materials that are used in the magnetic components disclosed herein include materials such as manganese-zinc (MnZn) and nickel-zinc (NiZn) ferrites. MnZn based ferrites can include a MnxZn1-xFe2O4where x ranges from 0.1-0.9. For example, x can be 0.2-0.8. NiZn based ferrites can include a NixZn1-zFe2O4ferrite where x ranges from 0.1-0.9. For example, x can be in a range of 0.3-0.4. In some embodiments, magnetic materials can include NiZn based ferrites such as NL12® from Hitachi and 4F1® from Ferroxcube, for example, for operation frequencies of 2.5 MHz or above. In certain embodiments, magnetic materials can include MnZn based ferrites such as ML90S® from Hitachi, for example, for operation frequencies between 500 kHz and 2.5 MHz. In some embodiments, magnetic materials can include MnZn based ferrites such as PC95® from TDK, N95®, N49® from EPCOS and ML24D® from Hitachi, for example, for operation frequencies of 500 kHz or lower. In certain embodiments, magnetic materials can include amorphous cobalt-based alloys and nanocrystalline alloys, for example, for operation frequencies of 100 kHz or lower. Nanocrystalline alloys can be formed on a basis of Fe, Si and B with additions of Nb and Cu. Nanocrystalline magnetic materials can be an alloy of Fe, Cu, Nb, Si and B (e.g., Fe73.5Cu1Nb3Si15.5B7). In some embodiments, nanocrystalline magnetic materials can be an alloy of Fe, Co, Zr, B and Cu. In certain embodiments, nanocrystalline magnetic materials can be an alloy of Fe, Si, B, Cu and Nb. In certain embodiments, nanocrystalline magnetic materials can be an alloy of Fe, Co, Cu, Nb, Si and B. The nanocrystalline magnetic materials can include an alloy based on Fe. For example, the alloy can be a FeSiB alloy.

While these materials are generally available in small sizes, some applications for wireless power transfer utilize magnetic components with a large areal size. For example, a car battery charging application may need to use a large areal size (e.g., 30 cm×30 cm) magnetic component to transfer high power of 1 kW or more (e.g., 2 kW or more, 3 kW or more, 5 kW or more, 6 kW or more).

In some embodiments, a single monolithic piece of magnetic components can be utiltized when the single monolithic piece of the required size is available. In some embodiments, it can be difficult and/or expensive to manufacture a monolithic piece of magnetic component such as MnZn or NiZn ferrites with a large areal size (e.g., 30 cm×30 cm) needed for the high power transfer. Moreover, MnZn and NiZn ferrites can be brittle, and accordingly, large-area pieces of these materials can be highly susceptible to breakage. To overcome such difficulties when fabricating the magnetic components disclosed herein, ferrite materials can be manufactured in pieces of small areal size (e.g., 5 cm+5 cm), and several such pieces can be joined together to form a larger combined magnetic component. These smaller magnetic elements can behave functionally in a very similar manner as a larger magnetic element when they are joined.

However, joining multiple smaller magnetic elements to form a larger magnetic component can introduce gaps and certain inhomogeneities relative to a single sheet of magnetic component. In particular, irregularities at the edges of the small pieces can lead to “magnetic field hot spots,” where magnetic fields are locally concentrated at the irregularities. Magnetic field hot spots due to irregularities at the edges of the joined pieces of magnetic component can damage the magnetic component due to heating, and/or reduce the quality factor of the apparatus.

In some embodiments, a gap can be formed between two pieces of magnetic elements. The gap can be an air gap, or can be filled with a dielectric material such as adhesive or a type of material different from the material of the magnetic elements (e.g., ferrite). When magnetic fields oscillate substantially perpendicular to interfaces of the gap, the magnetic fields can be concentrated with high density within the gap. In addition, magnetic fields can also be concentrated with high density at locations above or below the gap, and these concentrated magnetic fields can penetrate a portion of a shield at positions above or below or in the general vicinity of the gap. Such penetration can lead to loss of energy by generating eddy currents and heat in the corresponding portions of the shield. Similarly, strongly localized magnetic field hot spots induced by irregularities in the magnetic component may penetrate the shield and lead to loss of energy. To illustrate this phenomena,FIG. 3is a schematic diagram showing a cross-sectional view of the power transmitting apparatus102shown inFIG. 2according to coordinate392. In this example, when coil210generates a magnetic field within a gap302of magnetic component220, portions of the magnetic field304extend below the gap302and penetrate the shield229, which leads to energy loss as discussed above.

To mitigate such energy losses, this disclosure features shield geometries that reduce the effects of hot spots and concentrated magnetic fields due to irregularities at the edges and gaps of joined magnetic elements (e.g., pieces of magnetic component). In particular, energy losses due to the penetration of magnetic fields into shield229can be reduced by forming openings in the shield229and/or by modifying the shape of shield229in regions where the magnetic field density is locally increased, e.g., in regions corresponding to gaps between the magnetic elements. By adjusting the shape of the shield229, the extent to which the magnetic field304penetrates the shield229can be reduced, thereby mitigating energy losses.

The shields disclosed herein allow the use of magnetic components of large areal sizes (e.g., by joining many smaller pieces of magnetic component) while reducing energy losses due to interactions between the shield and concentrated magnetic fields. As a result, apparatuses that include the shields disclosed herein can achieve high power transfer efficiencies and can operate over a wide range of power transfer levels (e.g., between 0.5 kW to 50 kW). For example, the power transfer can be 3.3 kW or more (e.g., 6.6. kW or more).

Shield Configurations

FIG. 4Ais a schematic diagram showing an example of a power transmitting apparatus102including a coil210, a magnetic component220and a shield230. Shield230can function in a manner similar to shield229inFIG. 2, and the shield230can include an opening560which will be described later. Shield230can be formed of a conductive material similar to shield229. Coordinate390is the local coordinate of the magnetic component220.

InFIG. 4A, the coil210is positioned above the magnetic component220. The magnetic component220is positioned above the shield230in the C-direction without a portion of the coil210in between the magnetic component220and the shield230(e.g., without coil210extending in the C-direction). This configuration of the coil210can provide a compact power transmitting apparatus because the coil210does not take up space between the magnetic component220and the shield230as compared toFIG. 22described later.

The shield230lies in a plane nominally parallel to another plane in which the coil210lies. In this example, the magnetic component220lies in a plane parallel to another plane in which the coil210lies. In certain embodiments, the magnetic component220lies in a plane substantially parallel (e.g., within 3°, within 5°, within 10°, within 15°) to another plane in which the coil210lies.

The magnetic component220includes four magnetic elements410,412,414and416(e.g., ferrite tiles) each shaped as a rectangular slab. The magnetic elements are joined together with a dielectric material420to form the magnetic component220, which extends in a plane parallel to the A-B plane. In this example, the dielectric material420is an adhesive material which bonds the four magnetic elements410,412,414and416together. As explained previously, by fabricating a magnetic component from smaller magnetic elements, large-size magnetic components can be produced more easily and at lower cost compared to fabrication methods that rely on producing monolithic elements. By using multiple small magnetic elements to form a larger magnetic component, the size of the magnetic component can generally be selected as desired for a particular apparatus. In some embodiments, the size of the magnetic component can have an area of 30 cm×30 cm or larger (e.g., 40 cm×40 cm or larger, 50 cm×50 cm or larger).

In some embodiments, the magnetic component220can be formed from a plurality of tiles, blocks, or pieces of magnetic component that are arranged together to form magnetic component220. The plurality of tiles, blocks, or pieces can all be formed from the same type of magnetic component, or can be formed from two or more different types of magnetic components. For example, in some embodiments, materials with different magnetic permeability can be located at different positions of the magnetic component220. A dielectric material such as adhesive can be used to glue the different magnetic elements together. In some embodiments, magnetic elements can be in direct contact with one another. Irregularities in interfaces between the direct contact can lead to magnetic field hot spots. In some embodiments, the magnetic component220can include electrical insulator layers, coatings, strips, adhesives for mitigating build-up of heat at irregular interfaces within the magnetic component220.

Referring back toFIG. 4A, the magnetic component220includes gaps422and423, which are formed between the magnetic elements410,412,414and416. The discontinuities in the magnetic component220between adjacent magnetic elements define the gaps422and423. The gap422has its longest dimension extending in the A-direction and a maximum width424measured in a direction parallel to the B-direction. The gap423has its longest dimension extending in the B-direction and a maximum width425measured in the A-direction. The dielectric material420can fill the gaps422and423. In some embodiments, the gap422has a constant width measured in the B-direction. In certain embodiments, the gap422can have a non-constant width measured in the B-direction, e.g., depending upon the shapes of magnetic elements410,412,414, and416. For example, the magnetic elements can be arranged so that the gap422has a varying width. In some embodiments, the non-constant width can be due to curved edges of the magnetic elements.

The coil210has a plurality of loops which lie in the A-B plane, and includes windings451and452. The windings451and552correspond to first and second plurality of loops, respectively of the coil210. The winding451has an end401and connects to the winding452, which has an end403. In this example, starting from the end401, the winding451is concentrically wound around an axis402(starting from the inner winding of winding452towards its outer winding), which points into the drawing plane in (i.e., negative C-direction inFIG. 4A) according to the right-hand rule convention, which is used through-out this disclosure. The C-direction is perpendicular to the A-direction and the B-direction. As starting from the connected part between windings451and452, the winding452is concentrically wound around an axis404(starting from the outer winding of winding452towards its inner winding), which points out of the drawing plane (i.e., positive C-direction inFIG. 4A). In this example, the winding451is wound around in opposite direction of the winding452when measured from end401to end403. Dashed arrows479depict the direction of current flow in the windings451and452at a given time. In another way to described the winding directions, the winding451can be said to have clock-wise winding starting from its inner winding as seen towards the negative C-direction from the positive C-direction, and the winding451can be said to have clock-wise winding starting from its inner winding as seen towards the negative C-direction from the positive C-direction. In other words, the two windings can be said to have the same winding directions when measured from starting at their respective inner winding towards their outer windings.

The coil210is configured to generate oscillating magnetic fields and magnetic dipoles in the magnetic component220, which oscillate substantially along the B-axis, when currents oscillate within the coil210. The plurality of loops of the coil210define a coil that is positioned in the A-B plane. More generally, the coil210may form a flat portion of the coil210that is oriented at an angle to the A-B plane. For example, the angle can be within 5° or less (e.g., 10° or less, 15° or less, 20° or less). Generally, either or both of the axes402and404may point at an angle with respect to the C-direction. For example, the angle can be within 5° or less (e.g., 10° or less, 15° or less, 20° or less). In this disclosure, the “x” notation (e.g., of axis402) refers to a direction pointing into the drawing plane (i.e., negative C-direction inFIG. 4A) and the “dot” notation (e.g., of axis404) refers to a direction pointing out of the drawing plane (i.e., positive C-direction inFIG. 4A).

In this disclosure an “average magnetic field” of a magnetic component at a given time refers to the magnetic field integrated over the total volume of all magnetic elements in the magnetic component at the given time. Referring back toFIG. 4A, when an electrical current flows through the coil210from the end403to the end401, the current in the winding451circulates counter-clockwise, while current in the winding452circulates clockwise, as viewed from the positive C-direction towards the negative C-direction.

The oscillating electrical current in the coil210generates magnetic fields within the magnetic component220. To illustrate this, the power transmitting apparatus102shown inFIG. 4Ais depicted inFIG. 4B. The coil210and the shield230are not shown. Coordinate390is the local coordinate of the magnetic component220. Magnetic fields at several locations of the magnetic elements410,412,414and416at a particular time are schematically drawn as magnetic field lines470.FIG. 4Balso schematically depicts an average magnetic field471of the magnetic component220, which is the average of magnetic fields within the volume of magnetic elements410,412,414and416at a given time. In this example, the average magnetic field471points in direction441along the negative B-direction, at a given time. More generally, in some embodiments, the average magnetic field471points substantially along the direction441within 1° (e.g., within 3°, within 5°, within) 10° at a given time. Furthermore, the magnetic fields generated in the gap422oscillate in the B-direction. Accordingly, the magnetic fields generated in the gap422oscillate in a direction nominally perpendicular to an interface432between the magnetic element410and the dielectric material420and an interface434between the magnetic element416and the dielectric material420. Direction442is perpendicular to the direction441.

Generally, when the coil210generates magnetic fields in the magnetic component220with the average magnetic field471pointing along the direction441at a given time, high densities of magnetic fields become concentrated in the gap422. Moreover, irregularities at interfaces432and434of the gap422can contribute to form magnetic field hot spots.

FIG. 5is a schematic diagram of a portion of the power transmitting apparatus102shown inFIGS. 4A and 4B, showing the gap422between magnetic elements410and416at higher magnification. Coordinate390is the local coordinate as shown inFIGS. 4A and 4B. The interfaces432and434between the magnetic elements410and416are also shown. The interfaces432and434form the discontinuities of the magnetic component220between adjacent magnetic elements410and416. During operation, the coil210can generate oscillating magnetic fields, with a high density of magnetic fields521being concentrated in the gap422between the interfaces432and434. The gap422is filled with the dielectric material420(not shown) such as adhesive for joining the magnetic elements410and416. In some embodiments, the gap422is filled with air—in this case, the gap422is referred as an air gap.

In some embodiments, strongly localized magnetic field hot spots can be formed within the gap422. For example, as shown inFIG. 5, interfaces432and434may not be perfectly planar, and may include local peaks (e.g., peak512of interface432) and/or valleys (e.g., valley514of interface434). Oscillating magnetic fields between the interfaces432and434along the direction441can form “magnetic field hot spots,” where the magnetic fields are locally (e.g., in regions of the peaks or valleys) concentrated compared to other regions of the interfaces432and434.

For example, magnetic fields520depicted as dashed arrows within region510concentrate on the peak512. Concentrated field regions (e.g., region510) may lead to increased heating, material breakdown, and/or damaging of the magnetic component, which can lead to deteriorated power transfer efficiency provided by the power transmitting apparatus102.

Magnetic field hot spots can become more pronounced when the distance between the interfaces432and434is decreased. The distance between the interfaces432and434can be reduced (for example, when elements410and416are joined together more closely) to achieve a more compact arrangement of the magnetic elements410and416. Polishing the interfaces can, in certain embodiments, assist in reducing the extent of irregularities at the surfaces. However, it has generally been found that mechanical polishing alone does not fully ameliorate surface irregularities that lead to magnetic hot spots.

FIG. 6is a schematic diagram of a cross-sectional view of the power transmitting apparatus102described inFIGS. 4A, 4B and 5. Coordinate392is the local coordinate of the magnetic component220as shown inFIGS. 4A, 4B and 5. The coil210can generate magnetic fields521in the gap422between the interfaces432and434. In addition, concentrated magnetic fields525are also generated above and below gap422due to fringe effects. The fringe effects arise due to the edges of the magnetic elements410and412at the gap422, where the edges induce magnetic fields525to curve outwards from the A-B plane of the magnetic elements inFIG. 6. In addition, similarly, locations which form magnetic field hot spots such as in region510(shown inFIG. 5) can lead to high magnetic fields above and below the gap522due to fringe effects.

In the examples shown inFIGS. 4A, 4B, 5 and 6, the shield230is placed adjacent to the magnetic component420. This is illustrated inFIG. 6, where the shield230is depicted below the magnetic elements410and416. The shield230includes an opening560adjacent to the gap422. Opening560extends entirely through the thickness611of shield230.

For a conventional shield without opening560, the magnetic fields525below the gap422would penetrate the shield. Because the magnetic fields525can be strong due to the gap as described above, such penetration can induce large eddy currents which can generate heat in the shield. This leads to energy losses in the power transmitting apparatus102. If the conventional shield were moved closer to the gap422, the losses become even larger as magnetic fields525induce stronger eddy currents in the shield.

However, unlike conventional shields, the shield230has its opening560aligned to the gap between magnetic elements410and416and located in a region of the magnetic fields525. As a result, the penetration of fields525into shield230is significantly reduced or even eliminated, thereby mitigating the generation of strong eddy currents in the shield230. Thus, energy losses due to the shield230can be reduced or even eliminated, relative to energy losses that would otherwise occur due to a conventional shield.

Electromagnetic simulations can be used to predict and to compare characteristics of various power transmitting apparatuses.FIGS. 7A-Cshow schematic diagrams of a plurality of different embodiments for which operating characteristics have been both simulated and measured.FIG. 7Ashows a portion of a power transmitting apparatus700including a coil210.FIG. 7Bshows a portion of a power transmitting apparatus710including a coil210and a magnetic component220.FIG. 7Cshows a portion of a power transmitting apparatus720including a coil210, magnetic component220and a shield229.FIGS. 7A-Care depicted according to coordinates291. In all three apparatuses, coil210includes a litz wire forming a plurality of loops. In apparatuses710and720, magnetic component220includes a 2×2 array of 100 mm×100 mm N95 ferrite tiles. The N95 ferrite tiles are formed from MnZn ferrite materials. In apparatus720, shield229is 0.3 m×0.3 m in size and does not have an opening. The minimum distance between any point on the surface of magnetic component220and any point on the surface of shield229is 1 mm.FIG. 7Dis a schematic diagram of the magnetic component220in apparatuses710and720. In these embodiments, the magnetic component220has a constant width424of gap422measured in the B-direction.

Typically, wireless power transfer using high Q-factor resonators can be efficient because the high Q-factor can lead to large energy transfer efficiency between resonators. Furthermore, quality factor Qtransof an apparatus and quality factor contributed by a shield Qshield(which will be described in greater detail in a later section) can be indicators of how efficient the power transfer can be between apparatuses. In the following, the quality factor Qtransof an apparatus and the quality factor contributed by a shield to an apparatus, Qsheild, are discussed. A smaller value of quality factor Qtranscan lead to smaller energy transfer efficiency between apparatuses.

FIG. 8is a plot800showing measured and simulated quality factor values of apparatuses700,710and720as function of an operating frequency of currents applied to coil210, where width424of gap422is 1 mm. Curves802and804are the measured and simulated quality factor values for apparatus700, respectively. Curves806and808are the measured and simulated quality factor values for apparatus710, respectively. Curves810and812are the measured and simulated quality factor values for apparatus720, respectively. Curves810and812indicate smaller quality factor values compared to the quality factor values of curves802,804,806and808for a given operating frequency. The smaller values are attributable to the presence of the shield229of apparatus720; energy loss occurs when magnetic fields generated by coil210penetrate the shield229, as described in relation toFIGS. 3 and 6. The measured and simulated inductance values of apparatus700are 19.2 μH and 19.6 μH, respectively. The measured and simulated inductance values of apparatus710are 26.9 μH and 27.3 μH, respectively. The measured and simulated inductance values of apparatus720are 26.1 μH and 26.2 μH, respectively.

Electromagnetic simulations can be used to compare characteristics of systems with different distances between magnetic component and shields. Generally, the minimum distance between any point on the surface of magnetic component220and any point on the surface of shield229can be 1 mm or less (e.g., 2 mm or less, 5 mm or less, 10 mm or less, 15 mm or less, 20 mm or less).FIG. 9is a plot900showing simulated values of Qshieldaccording to Eq. (3) (described later) of the apparatus720for different separation distances between the magnetic component220and the shield229in the C-direction at an operating frequency of 85 kHz. Qshieldis calculated as a function of the width424of gap422measured in the B-direction. Curve902corresponds to a zero separation distance. Curve904corresponds to a separation distance of 0.5 mm. Curve906corresponds to a separation distance of 1 mm. Curve902has the smallest Qshieldfor a given width424of the gap422. Accordingly, shield229corresponding to curve902leads to the largest energy loss compared to that of other curves. This is because, for the case of curve902, shield429is closest to the magnetic component220, and thus a larger portion of magnetic fields penetrate the shield229. For all three curves902,904and906, Qshielddecreases as the width of the gap422increases. In some embodiments, a separation distance between a shield and a magnetic component can be increased to have a higher Qshieldby reducing penetration of localized magnetic fields into the shield. However, this approach may be disadvantageous because the overall size of a power transmitting apparatus becomes larger due to the increased separation between the shield and the magnetic component.

As previously described, energy loss due to penetration of magnetic fields into shield229can be reduced by forming openings in the shield229where the magnetic field density is locally increased, e.g., in regions corresponding to gaps between the magnetic elements.FIG. 10Ashows a cross-sectional view of apparatus720according to coordinate392.FIG. 10Bshows a cross-sectional view of a power transmitting apparatus1000, which includes a shield230according to coordinate392. The shield230includes an opening560, which extends along the A-direction and has a maximum width1009measured in a direction parallel to the B-direction.

In the example shown inFIG. 10B, the magnetic component220extends in a plane in which arrow of direction441lies on and parallel to the A-B plane. Accordingly, the plane extends in the A-direction and the B-direction, which are orthogonal to each other. The plane passes through the middle of the magnetic component220as measured in the C-direction. The coil210is positioned on a first side of the plane in the positive C-direction. The shield230is positioned on a second side of the plane in the negative C-direction. In this example, the coil210is positioned entirely on the first side of the plane. In other examples, the coil210can be at least in part positioned on the first side of the plane. As described below, the shield230can include one or more openings (e.g.,560) positioned relative to one or more gaps (e.g., gap422). The shield230can lie in a plane substantially parallel (e.g., within 3°, within 5°, within 10°, within 15°) to the plane in which the magnetic component220extends. Similar descriptions can be applied to other examples in this disclosure.

When coil210generates a magnetic field within gap422of the magnetic component220in a direction parallel to the B-direction, a portion of the magnetic field525extends below gap422and penetrates shield229, which leads to energy loss, as discussed previously. The penetration of portion525of the magnetic field into shield229is shown onFIG. 10A.

In apparatus1000, however, penetration of magnetic field525into shield230is reduced or eliminated because opening560is aligned with gap422, and therefore positioned at the location where magnetic field525extends below gap422. Because there is no shield material where magnetic field525extends below the gap422, the effect of magnetic field525on shield230is significantly mitigated relative to apparatus720.

In general, the opening560can be located where the magnetic field below the magnetic component420is particularly strong due to fringe effects or hot spots. By providing an opening in a region of the shield where strong magnetic fields would otherwise penetrate the shield, energy losses due to the shield can be reduced or eliminated. Accordingly, one or more openings of the shield230can be respectively aligned with corresponding ones of the one or more gaps of the magnetic component220. The relative positioning of the one or more openings with respect to the one or more gaps can reduce interactions between magnetic flux of the magnetic fields crossing discontinuities of the magnetic component220and the shield230. Moreover, the absence of shield material can lead to a lighter weight shield and reduce shield material costs.

InFIG. 10B, opening560has the width1009and the opening560extends in the A-direction, e.g., out of the plane ofFIG. 10B. Typically, due to the shapes of the magnetic elements and the gaps between them, the opening560has a longest dimension extending along the A-direction. In some embodiments, the longest dimension of the opening560is substantially parallel (e.g., within 3°, within 5°) to the A-direction. In the example shown inFIG. 10B, the width1009of opening560is orthogonal to its longest dimension, and the width424of the gap422measured in the B-direction is orthogonal to its longest dimension extending in the A-direction.

The width1009of opening560of shield230can be selected to provide reduced energy loss due to magnetic field penetration into the shield230, while at the same time shield230still effectively shields magnetic fields from lossy objects.FIG. 11Ais a schematic diagram of a portion of a power transmitting apparatus1100with an opening560having a width1009of 4 mm in direction441, which is oriented in a direction parallel to the B-direction of coordinate1191.FIG. 11Bis a schematic diagram of a portion of a power transmitting apparatus1110with an opening560having a width1009of 10 mm in direction441, according to coordinate1191. Apparatuses1100and1110each include a magnetic component220with a gap422(not shown). The gap422has a width424in the B-direction.

FIG. 12is a plot1200showing simulated values of Qshield(described later) for apparatuses720(curve1202),1100(curve1204) and1110(curve1206) at an operating frequency of 85 kHz for currents applied to coil210. Qshieldis calculated as a function of the width of gap422measured in the B-direction in mm. Curve1202has the smallest Qshieldfor a given width of gap422because, for apparatus720, penetration by magnetic field525into shield229occurs to a larger extent than for apparatuses1100and1110due to the absence of an opening in shield229. For all three apparatuses720,1100, and1110, Qshielddecreases as the width of gap422of magnetic component220increases.

Generally, an opening560can have a width1009in a direction parallel to oscillations of magnetic fields within a gap of a magnetic component220. Referring back toFIG. 12, plot1200shows that apparatus1110has a larger Qshieldthan that of apparatus1100for a given width424of gap422. Accordingly, in some embodiments, it can be advantageous to have an opening560with a width1009larger than width424of the gap422. This is because with a larger width1009, penetration of locally concentrated magnetic fields within the gap422into shield230is reduced.

In certain embodiments, a ratio of the width1009to width424can be 10:5 or less (e.g., 10:2.5 or less, 10:2 or less, 10:1 or less, 10:0.5 or less, 10:0.4 or less, 10:0.2 or less). A high ratio may lead to a higher Qshield. In some cases, if the ratio of the width1009to width424is too large, the shield230may not effectively shield lossy objects. In some embodiments, the ratio of the width1009to width424is not larger than 100:1 (e.g., not larger than 50:1, not larger than 25:1). For example, the ratio of the width1009to width424can be about 100:1 rather than 25:1 when the width424is smaller compared to the case when it is larger.

In some embodiments, gap422can have a minimum width of 0.2 mm or more (e.g., 0.5 mm or more, 1 mm or more, 1.5 mm or more, 2 mm or more). Opening560can have a minimum width of 1 mm or more (e.g., 2 mm or more, 4 mm or more, 8 mm or more, 10 mm or more, 15 mm or more).

In some embodiments, width1009of opening560can be equal to or less than width424of gap422. Such a configuration may be utilized, for example, when a thickness of shield230is about a skin depth or less (e.g., half the skin depth) of the shield material and/or one or more lossy objects are close by (e.g., within 3 mm) to the shield230. The skin depth of the shield material is the length of material through which the oscillating magnetic fields at the operating frequency pass before their amplitudes have decayed by a factor 1/e. In this case, if the width1009is larger than the width424, concentrated magnetic fields within gap422can still interact with the lossy object because the thickness of shield230is relatively thin and/or the lossy object is close to the shield230. Therefore, in this case, it can be desirable to have width1009to be equal or less than width424although magnetic fields may still penetrate the shield230.

In this disclosure, a characteristic size of the magnetic component220is defined as the radius1011of the smallest sphere that fits around the magnetic component220as illustrated inFIG. 10C. The extent of fringing magnetic field (e.g., field525) induced in the vicinity of the magnetic component220can depend on the characteristic size of the magnetic component220. For example, if the characteristic size is scaled by a factor of 2, the extent of fringing magnetic field may scale by a factor of 2. Because of the dependence of the fringing magnetic field on the characteristic size, an optimum width1009of opening560can depend on the characteristic size of the magnetic component220. When the ratio of the width1009to the characteristic size of the magnetic component220becomes larger, the fringing magnetic field can more effectively pass through the opening560and interact with a lossy object, which may be positioned on the other side of the shield230. Such interaction can lead to losses of magnetic fields induced in the vicinity of the magnetic component220. Accordingly, in certain embodiments, it is advantageous to have the ratio of the width1009to the characteristic size to be an optimum value or less to avoid the losses described in the preceding sentence. For example, the ratio of the width1009to the characteristic size of the magnetic component220can be 1:10 or less to mitigate the effects of magnetic fields passing through opening560and interacting with lossy objects. In certain embodiments, the ratio can be 1:12 or less (e.g., 1:15 or less).

Referring toFIG. 11B, the coil210is electrically disconnected from the shield230. This approach can lead to easier manufacturing of the arrangement1110compared to approaches where a coil is electrically connected to a shield. The coil210lies above the magnetic component220without passing through gaps of the magnetic component220. This approach can lead to easier manufacturing of the arrangement1110compared to the approach described later in relation toFIG. 22, because the coil210can be easily positioned above the magnetic component220. A single power source can be used to drive the coil210.

Referring back toFIG. 10B, oscillation of currents in coil210can induce “image” currents in shield230. Such image currents can generally be described in a manner analogous to image charges and the method of images used to replicate electromagnetic boundary conditions along an infinite plane of a perfect conductor. Image currents can flow in a distribution at the surface of the shield230and in some embodiments, the image currents in the shield230can increase the effective thickness of the magnetic component220(e.g., by a factor of about 2). InFIG. 10, opening560does not significantly disrupt image currents formed in the shield230because the opening560extends parallel to the image currents. For example, referring back toFIG. 4A, center portion440of coil210has currents flowing in positive and negative directions of axis A at a given time. Accordingly, in a shield positioned adjacent to center portion440, image currents flow in both the positive and negative A-directions as well. When opening560extends along the A-direction, the opening560does not extend perpendicular to image currents below the center portion440, but instead extends parallel to the image currents. Accordingly, opening560does not significantly disrupt the image currents in the shield230.

FIG. 13Ais a schematic diagram of a power transmitting apparatus1300without a shield placed between a magnetic component220and a lossy object1302according to coordinate1391. Direction441points in the negative B-direction.FIG. 13Bis a schematic diagram of a power transmitting apparatus1310including a shield230(e.g., a copper shield) with an opening560, positioned between a magnetic component220and a lossy object1302, according to coordinate1391. Direction441points in the negative B-direction. The shield230is separated from the lossy object1302by a distance of 2.5 mm in the C-direction. Magnetic component220is formed from a 2×2 array of magnetic elements joined by dielectric material420, which fills the gaps between the magnetic elements, in the same manner as described previously. Dielectric material420is not depicted inFIGS. 13A and 13B. In these examples, the lossy object1302formed of ASTM type A1008 steel.

FIG. 14is a plot1400showing simulated values of Qshield(described later) for apparatuses1300and1310at an operating frequency of 85 kHz for currents applied to coil210. Qshieldwas calculated as a function of width424of gap422of the magnetic component420measured in direction441. Curve1220corresponds to apparatus1300with no shield. Curve1404corresponds the apparatus1310where the width1009of opening560is 0 mm. Curve1406corresponds to apparatus1310where the width1009of opening560measured in the direction441is 4 mm. Curve1408corresponds to apparatus1310where the width1009of opening560is 10 mm. Apparatus1300has the smallest Qshielddue to absence of a shield. The apparatuses that correspond to openings of width 4 mm and 10 mm have higher Qshieldthan the apparatus that corresponds to no opening, indicating that the presence of opening560can reduce power dissipation and energy losses induced by the presence of a shield.

As described above, in some embodiments, the width of opening560can be selected based on the width of gap422. To choose the width of opening560, a plot such as plot1400can be used. In certain embodiments, where width of gap422is fixed, the width of opening560can be selected. For example, for a width of 0.2 mm of gap422, the width of opening560can be selected to be 4 mm over 10 mm. For a width of 1.8 mm of gap422, the width of opening560can be selected to be 10 mm over 4 mm according to plot1400. Other widths than 4 mm and 10 mm of opening560can be selected to have a higher Qshielddepending on a fixed width of gap422.

FIG. 15Ashows a series of images of an example of a power transmitting apparatus including a coil210. Image1500shows the coil210positioned on one side of a support1502. Image1510shows the other side of support1502where a magnetic component220is positioned. Image1520shows a shield229without an opening or segments. The shield229is positioned such that magnetic component220is positioned between shield229and support1502.

FIG. 15Bshows a series of images of example of another power transmitting apparatus including a coil210. Image1530shows a coil210positioned on one side of a support1502. A shield230with an opening560is positioned below the support1502. Image1540shows a magnetic component220a shield230, which are positioned on the opposite side of support1502from the coil210.

FIG. 16is a plot1600showing measured values of Qtransvalues for the apparatuses shown inFIGS. 15A and 15Bas a function of operating frequencies of currents applied to coil210. Curve1602corresponds to the apparatus inFIG. 15Awith no opening in shield229. Curve1604corresponds to the apparatus inFIG. 15Bwith a shield opening of width 2 mm. Curve1606corresponds to the apparatus inFIG. 15Bwith a shield opening of width 5 mm. Curve1608corresponds to the apparatus inFIG. 15Bwith a shield opening of width 10 mm. It is evident from plot1600that as the width of opening560increases, Qtransalso increases at each operating frequency.

FIG. 17is a plot1700showing measured values of Qshieldfor the apparatuses shown inFIGS. 15A and 15Bas a function of the operating frequencies of currents applied to coil210. Curve1702corresponds to the apparatus inFIG. 15Awith no opening in shield481. Curve1704corresponds to the apparatus inFIG. 15Bwith a width of 2 mm for opening. Curve1706corresponds to the apparatus inFIG. 15Bwith a width of 5 mm for opening. Curve1708corresponds to the apparatus inFIG. 15Bwith a width of 10 mm for opening. It is evident from plot1700that Qshieldincreases for a given operating frequency as width of the opening560becomes larger.

Openings in the shield can generally be implemented in a variety of ways. In some embodiments, a shield can be segmented into two pieces like the example shown inFIG. 15B. In certain embodiments, a shield can be a monolithic piece of conductor with an opening. To illustrate this,FIG. 18Ashows a schematic diagram of a shield1850formed of a monolithic piece of conductor with length1854measured in the A-direction of coordinate390. The shield1850includes an opening1852having a length1856smaller than the length1854in the A-direction. Such a shield1850can be fabricated from a single sheet of conductor, where the opening1852is drilled, punched, cut, stamped, pressed, or otherwise introduced into shield1850. Such an approach can be advantageous due to ease of manufacturing. Further, the use of a monolithic shield can eliminate the alignment of two different pieces of conductor to form a shield. In this example, the opening1852extends entirely through the thickness of the shield1850, although more generally, opening1852can also extend only partially through the thickness of shield1850. Further, although shield1850includes one opening1852inFIG. 18A, more generally shield1850can include any number of openings.

FIGS. 18B and 18Cshow schematic diagrams of a shield1800with notches1802and1803. InFIG. 18B, coordinate390indicates the orientation of the shield1800. The notch1802can be positioned such that it is aligned with a gap422of a magnetic component220where magnetic fields can be concentrated, as shown inFIG. 18C. Similarly, the shield1800can be positioned such that notches1803are aligned with magnetic field hot spots1806in the magnetic component220(shown inFIG. 18C), which are described in greater detail above.

FIG. 18Cshows a cross-sectional view of the shield1800according to coordinate392. The notch1802extends to a fraction of the thickness1804of the shield1800but sufficiently deep enough to reduce penetration of magnetic field525into the shield1800. For example, a depth1805from a surface of the shield1800to the deepest point of the notch1803can be about twice or more (e.g., three times or more, four times or more) of a skin depth of the shield material of the shield1800at the operating frequency. Generally, the shield1800can include curved grooves forming depressions in the shield.

The strength of the magnetic field525typically decays away from the surface of magnetic component220according to a power law of the ratio (α) of the width of gap422(i.e., width424inFIG. 10B) to the distance of magnetic field525from the surface of the magnetic component (i.e., the surface facing shield1800inFIG. 18C), where the distance is measured in the −C direction inFIG. 18C. To reduce penetration of the magnetic field into shield1800, in some embodiments, notch1802and/or notch1803can extend to a depth below a surface of the shield (i.e., below the surface facing magnetic component220inFIG. 18C) of 1/α or more (e.g., about ½α or more). The cross-sectional profile of the notch1802can be curved, as shown in the cross-sectional view, or triangular, as shown for notch1803. Similarly, the cross-sectional profile for notch1803can be triangular, as shown in the cross-sectional view, or curved as shown for notch1802.

FIG. 18Dis a schematic diagram of a shield1860including multiple openings1862. In this example, each of the openings1862are aligned to multiple gaps422between magnetic elements1863to mitigate the penetration of concentrated magnetic fields into the shield1860. Each of the openings1862has a width that extends parallel to the B-direction.FIG. 18Eis a schematic diagram of a shield1870including openings1872and1874. The openings1872and1874have non-rectangular cross-sectional shapes so that the openings1872and1874are aligned to gaps422between magnetic elements1873,1875and1876to mitigate the penetration of concentrated magnetic fields into the shield1870. Generally, openings can have cross-sectional profiles including triangular, trapezoidal, circular, elliptical, parabolical and hyperbolical shapes. The profiles can be selected based on geometry of gaps and arrangements of magnetic elements.

More generally, a magnetic component can be formed in a way that multiple gaps exist and magnetic fields oscillate perpendicular to surfaces of the gap, for example, as described above. In this case, multiple openings and notches can be formed in the shield to reduce power dissipation and energy loss due to the shield positioned below the magnetic component. The openings and notches can form depressions in the shield that extend only partially through a thickness of the shield, or can extend completely through the shield. In similar manner described in preceding paragraphs, the depressions can be positioned to be respectively aligned with corresponding gaps of the magnetic component. The depressions can be positioned relative to the gaps to reduce interactions between magnetic flux of magnetic fields crossing discontinuities of the magnetic component and the shield.

In the example shown inFIG. 18D, the shield1860has three openings1862. In certain embodiments, the shield1860can have other number (e.g., two, four, five) of openings to match a number of gaps422formed by magnetic elements. At least one of the gaps422can be filled with dielectric material (e.g., adhesive material).

In some embodiments, openings formed in the shield have lateral surfaces that are orthogonal to the surface of the shield that faces the magnetic component. More generally, however, openings formed in the shield can have lateral surfaces with a variety of orientations with respect to the surface of the shield that faces the magnetic component.FIG. 18Fis a schematic diagram of a cross-sectional view of a shield1880according to coordinate392. The shield1880includes an opening1882, which extends entirely through the shield1880of its thickness1886. In this example, the opening1882has tapered side-walls. In other words, the side-walls of the opening1882form angle1888with respect to the C-direction, which is normal to the surface of shield1880that faces magnetic component220. In some embodiments, the angle1888can be 45° or less (e.g., 30° or less, 15° or less). By having a larger open region closer to gap422of magnetic component220and a smaller open region on the other side of the magnetic component220, where lossy object1889is positioned, the opening1882can mitigate penetration of magnetic field525into the shield1880due to the larger open region, while effectively shielding lossy object1889due the smaller open region. Similarly, notch1884can be aligned to magnetic field hot spot1806to mitigate magnetic field penetration into shield1880. In this example, notch1884has cross-sectional profile of a trapezoidal shape. Generally, the profile can be a triangular, trapezoidal, circular, elliptical, parabolical and hyperbolical shapes. The profiles can be selected based on geometry of gaps and arrangements of magnetic elements. An opening or notch which forms a depression can have a width measured at the surface of the shield facing the magnetic component to be larger than a width of the depression measured at another location between its lateral surfaces.

FIG. 18Gis a schematic diagram of a cross-sectional view of a shield1895according to coordinate392. In this example, opening1897of shield1895has one or more curved edges1896, which are shaped to conform to a distribution of the magnetic field525along the negative C-direction to mitigate penetration of field525into the shield1895.

During use of a power transmitting apparatus, magnetic component220can become damaged, which may lead to the formation of hot spots. The existence and/or development of hot spots can be monitored using a thermal detector with appropriate spatial resolution. For example, the thermal detector can measure localized high temperature points which can correspond to damage or defects in the magnetic component220. Then openings or notches described in detail above can be formed into a shield based on the monitored hot spots to accommodate the presence of hot spots.

In some embodiments, the width of gap422between elements of the magnetic component can vary, and accordingly, an opening of shield230can have a varying width to match the varying width of gap422. To illustrate this,FIG. 19Ashows a schematic diagram of an example of a power transmitting apparatus1900according to coordinate390. The apparatus1900includes a coil210, a magnetic component220and a shield1920. The magnetic component220includes an array of magnetic elements1910. The coil210is configured to generate magnetic fields oscillating along the B-direction within the magnetic component220. The magnetic elements1910are positioned between the coil210and the shield1920along the C-direction. The magnetic elements1910are tapered and have side-walls1911extending at an angle relative to the A-direction. The angle can be, for example, 45° or less (e.g., 30° or less, 15° or less). The angle of the side-walls with respect to the A-direction produces a gap of varying width in the B-direction between elements1910of the magnetic component220(exaggerated inFIG. 19Afor purposes of illustration).

The varying width of the gap leads to varying magnetic resistance of the magnetic component220along the A-direction. Accordingly, when the coil210generates magnetic field within the magnetic component220, magnetic elements1910can be arranged so that the varying magnetic resistance provides a more uniform distribution of magnetic fields than would otherwise be possible with a gap of constant width in the B-direction, thereby leading to less power dissipation in the magnetic component220.

For magnetic components with gaps between elements that vary in width, opening1921of the shield1920can also have varying width to match the varying width of the gap between magnetic elements1910to mitigate concentration of penetration of magnetic fields into the shield1920.

FIG. 19Bis a schematic diagram of a cross-sectional view of a power transmitting apparatus1930, which includes a magnetic component220and a shield230, according to coordinate392. In this example, the magnetic component220has curved edges1932. The curved edges1932can lead to reduced fringe effects at gap422so that magnetic fields525extend less outward of the gap422compared to the case shown inFIG. 10Bwith straight edges. Thus, in this approach, shield230can have an opening560with smaller width because magnetic field525can penetrate less into the shield230due to reduced fringe effects. In some embodiments, the magnetic component220can have beveled edges cut as a straight line instead of curved edges. In some embodiments, the shield230can have curved edges1934at its opening560. An opening with curved edges may reduce concentration of induced eddy currents by magnetic field525, and thereby reducing losses by the shield230. In certain embodiments, the shield230can have beveled edges cut as a straight line instead of curved edges.

FIG. 19Cis a schematic diagram of a cross-sectional view of a power transmitting apparatus1940, which includes a magnetic component220and a shield230, according to coordinate392. In this example, a magnetic material1942fills in gap422. The magnetic material1942can be a different type of material from that of magnetic component220. For example, in some embodiments, magnetic material1942can have a larger magnetic permeability than that of magnetic component220. When magnetic material1942has a larger magnetic permeability than magnetic component220, magnetic fields525typically do not extend outward from gap422as far as they would if magnetic material1942had a smaller magnetic permeability than magnetic component220, because the magnetic material1942helps to confine magnetic fields within the gap422. In certain embodiments, the magnetic material1942can be applied to thoroughly fill in the gap422. Thus, in the above approach, shield230can have an opening560with smaller width because magnetic field525penetrates less into the shield230due to reduced fringe effects.

FIG. 19Dis a schematic diagram of a cross-sectional view of an example of a power transmitting apparatus1950, which includes a magnetic component220and a shield230, according to coordinate392. In this example, magnetic tape1954is attached over gap422in a location between the magnetic component220and the shield230. The magnetic tape1954can contact the magnetic component220. Due to the magnetic permeability of the magnetic tape1954, the magnetic tape1954can confine magnetic fields, mitigating the fringe effect of gap422. As a result, magnetic fields525do not extend as far outward from gap422. Thus, in this approach, shield230can have an opening560with smaller width because magnetic field525penetrate less into the shield230due to reduced fringe effects attributable to the presence of magnetic tape1954. Material within gap422can include dielectric material and/or magnetic material as described in preceding paragraphs.

In some embodiments, a dielectric material or magnetic material can fill in gap422of a magnetic component220. The dielectric material (e.g., coolant liquids) or magnetic material filling the gap422can have high thermal conductivity and be placed between magnetic elements to facilitate the dissipation of heat generated within the magnetic elements. Referring toFIG. 19E, a magnetic component220includes an array of magnetic elements1962-1966according to coordinate390. Only a few magnetic elements are labeled inFIG. 19Efor simplicity. A dielectric material420of high thermal conductivity fills in gaps between the magnetic elements1962-1966. Accordingly, heat generated at magnetic elements1964and1966in inner regions of the magnetic component220can effectively transfer to heat sinks1967contacting sides of the magnetic component220. For example, the heat sinks1967can contain coolant for transferring heat out of the magnetic component220.

In the example shown inFIG. 19E, the array is a 4×4 array. More generally, however, any number of magnetic elements can be joined to form a magnetic component, which allows the size of the magnetic component to extend over a larger area than that shown inFIG. 19E.

In some embodiments, magnetic elements can be joined together by an adhesive tape. For example,FIG. 19Fis a schematic diagram showing an example of a magnetic component220joined by an adhesive tape1981within gaps422and423and sandwiched between magnetic elements410,412,414and416. As another example,FIG. 19Gis a schematic diagram showing an example of another magnetic component220with magnetic elements joined together by adhesive tape1982and1983.

FIG. 19His a schematic diagram of a magnetic component220having a rectangular cuboid shape with magnetic elements410,412,414and416and gaps422and423. Generally, a magnetic component can be in other forms than a rectangular cuboid. For example,FIG. 19Iis a schematic diagram of an example of a magnetic component220of a cylindrical shape. The magnetic component220has two magnetic elements410and416with gap422in between. As another example,FIG. 19Jis a schematic diagram of another example of a magnetic component220of an elongated cylinder with oval face1971. The magnetic component220includes magnetic elements410,412and414with gaps422.

In addition to the shield geometries disclosed above for mitigating energy losses due to penetration of the magnetic fields from the magnetic component into the shield, other techniques can also be used to reduce energy losses.

In some embodiments, for example, energy losses due to penetrating magnetic fields can be reduced by adjusting the magnetic field distribution within the magnetic component.FIGS. 20A and 20Bare schematic diagrams of additional examples of coil210. Coordinate390indicates the coordinate axis. A shield is not shown. In the left-hand side ofFIG. 20A, coil210includes a conducting wire forming a plurality of loops, where different portions of the loops correspond to different diameters of the wire. For example, portion2031of the wire has a larger diameter than portion2032. Portion2032of the wire has a larger diameter than portion2033. Differences in diameters in different portions of the coil are schematically depicted by the thickness of lines of the coil2030. To illustrate this, a cross-sectional view along section line B1-B2is depicted on the right-hand side ofFIG. 20Aaccording to coordinate392. The variations of diameters along the wire may be used to control a uniformity of magnetic field distribution induced in magnetic component220by the coil210. For example, a more uniform distribution can lead to less hot spots and energy losses of the magnetic fields. In some embodiments, the diameter variation can be selected based on the geometry of magnetic component220.

FIG. 20Bis a schematic diagram of an example of a power transmitting apparatus2020. A shield is not shown. Two coils2040and2041are positioned adjacent to a magnetic component220. Each of two coils2040and2041includes a plurality of loops. Currents can be separately applied to coils2040and2041to generate a magnetic field distribution in the magnetic component220. For example, oscillating currents can be applied with equal magnitude and phase to coils2040and2041so that, at a given time, currents within the coil2040circulate counter-clockwise and currents within the coil2041circulate clockwise as seen from the positive C-direction towards the negative C-direction.

The magnitudes and phases of the applied currents in each of the two coils2040and2041can be selected to control a uniformity of magnetic field distribution induced in the magnetic component220. A more uniform distribution can lead to less hot spots and energy losses of the magnetic fields within the magnetic component220. In contrast, less uniform magnetic distribution may localize fields into hot spots. The magnitudes and phases can be selected depending on the geometry and/or properties of the magnetic component220.

Non-uniform magnetic field distributions within the magnetic component lead to the formation of hot spots, because power is dissipated locally in proportion to the square of the magnetic field amplitude. Moreover, a non-uniform magnetic field distribution increases the loss coefficient of the magnetic component. Both of these effects lead to a reduced quality factor for a resonator that includes the magnetic component, and can even cause the magnetic component to saturate at lower power levels.

However, these effects can be mitigated by generating a more uniform magnetic field distribution within the magnetic component, as described above. In particular, because power dissipation varies approximately proportionally to the square of the magnetic field amplitude, for a fixed total magnetic flux through a magnetic component, a configuration with a more uniform field distribution will generally exhibit lower losses than a configuration with a more non-uniform field distribution. The effect is analogous to the electrical resistance of an electrical conductor, where decreasing the effective cross-sectional area of the conductor leads to higher resistance, for example, due to the skin effect.

In some embodiments, magnetic elements positioned below coil2040can have a different magnetic resistance than the magnetic elements positioned below coil2041due to manufacturing imperfections that lead to different sizes of magnetic elements and/or different magnetic permeabilites of the magnetic elements. For example, magnetic elements positioned below coil2040can have a magnetic permeability smaller by 2% or more (e.g., 5% or more, 10% or more) than that of magnetic elements positioned below coil2041due to fabrication tolerances and/or errors.

To circumvent such imperfections, coil2040can operate with current having a magnitude that is larger by 2% or more (e.g., 5% or more, 10% or more) than that of coil2041. The phase difference of currents between the coils2040and2041can be 10° or more (e.g., 20° or more, 30° or more) to match a magnitude of the currents at a given time. Such approaches may lead to a more uniform magnetic field distribution, thereby reducing the formation of hot spots that lead to magnetic fields bending outwards from gaps between the elements of magnetic component220, and also reducing energy losses of the magnetic fields within the magnetic component220. In some embodiments, either or both of two coils2040and2041can have varying diameters of wire in a similar manner described in relation to coil210inFIG. 20A.

FIG. 21is a schematic diagram of another example of coil210. Coordinate390indicates the coordinate axis. A shield is not shown. In the left-hand side ofFIG. 20A, coil210includes two windings451and452similar to coil210shown inFIG. 4A. But in this example, portions of windings451and452have different spacings2111and2112. For example, wire portion2131of the coil210has spacing2112from the adjacent wire portion2132. Wire portion2134of the coil230has spacing2111from the adjacent wire portion2133. To illustrate this further, a cross-sectional view along section line B1-B2is depicted on the right-hand side ofFIG. 21according to coordinate392.

By providing a coil with an increased spacing2111(e.g., relative to spacing2112) between adjacent loops in the region of coil210that is near gap422(not shown) in the magnetic component, the concentration of magnetic fields within gap422can be reduced, because less dense coil windings can induce weaker magnetic fields. Thus, penetration of magnetic fields into an adjacent shield can be reduced. Moreover, variations in spacings between adjacent wire portions in coil210can be used to control a uniformity of magnetic field distribution induced in magnetic component220, leading to less hot spots and energy losses of the magnetic fields.

FIG. 22is a schematic diagram of a power transmitting apparatus2200, which includes a coil2204having a plurality of loops wrapped around a magnetic component220. In this example, the coil2204is connected to at least one capacitor (not shown). The conductor shield2206can include two flaps2207which are bent down ends of the conductor shield2206. The flaps2207do not add to the overall length2209of the conductor shield2206, but can improve the shielding effect of the conductor shield2206by deflecting and guiding magnetic field lines downwards, and reducing field interactions with lossy object2208. This configuration can increase the effectiveness of conductor shield2206without increasing its length2209.

The coil2204is wound around the magnetic component220, which can have one or more gaps422(not shown) as described above. The gaps may lead to concentrated magnetic fields penetrating into the shield2206. Accordingly, the shield2206can have an opening2210aligned to a gap422of the magnetic component220to mitigate the magnetic field penetration.

FIG. 23is a schematic diagram of another example of a power transmitting apparatus2300according to coordinate2391. The apparatus2300includes multiple coils2304, where each coil2304is wound around a magnetic component2302, with several such magnetic components2302are arranged as an array. The magnetic component2302may or may not have gaps422as described for magnetic component220. In some embodiments, coil2304is in direct contact with it respective magnetic component2302. In certain embodiments, coil2304is not in direct contact with it respective magnetic component2302. The coils2304are configured to generate oscillating magnetic fields and magnetic dipoles within their respective magnetic components2302when currents oscillate within the coils2304. For example, at a given time, the coils2304can generate magnetic dipoles along the axis of dipole moments2303. The configuration shown inFIG. 23can be used in preference to an apparatus that includes a large monolithic magnetic component, for example, with a size of the combined areas of the four magnetic components2302, due to the difficulties associated with producing such large magnetic components disclosed herein. The configuration may also be advantageous in that multiple larger sized and differently shaped apparatuses can be assembled from smaller and single-sized apparatuses. In some manufacturing, the ability to assemble, repair and reconfigure a wide range of apparatus configurations from a number of subcomponents that may be tracked, stored, shipped can be desirable. The four magnetic components2302are separated by gaps2310and2311, which correspond to separations AA and BB, respectively. Accordingly, within the gap2311, magnetic fields generated by the coils2304oscillate in the B-direction.

The apparatus2300can include a shield2320positioned adjacent to the magnetic component2302in the negative C-direction. The shield2320can include an opening2322, which can act as an opening560described above. The configuration of apparatus2300can be advantageous because each of the coils2304can generate strong magnetic flux densities within respective magnetic components2302, which can be utilized for providing for high power transfer in applications such as car charging.

In the example shown inFIG. 23, the magnetic components2302extends in a plane in which the arrows of axis of dipole moment2303lie on and parallel to the A-B plane. The plane passes through the middle of the magnetic components2302as measured in the C-direction. Parts of the coils2304are positioned on a first side of the plane in the positive C-direction, while the other parts of the coils2304are positioned on a second side of the plane in the negative C-direction. The shield2320is positioned on the second side of the plane in the negative C-direction. Accordingly, the coils2304are, in part, positioned on the first side of the plane. Generally, the shield2320can include one or more openings (e.g., opening2322) positioned relative to one or more gaps within the magnetic components2302or between the magnetic components (e.g., gap2311). Similar description can be applied to the examples shown inFIGS. 22 and 24A.

FIG. 24Ais a schematic diagram of a power transmitting apparatus2400including a plurality of conducting wire segments2432that form a coil, and a shield2481electrically connected to the plurality of conducting wire segments2432, according to coordinate2491. In this example, a magnetic component220is disposed in an internal region of the coil defined by the conducting wire segments2432and the shield2481. The shield2481is split into distinct isolated conductor segments2402each electrically connected to different conducting wire segments2432. The net result is a series connection of conductor wire segments2432alternated with electrically isolated segments of the shield2481. The isolated segments of the shield2481can be electrically insulated from one another by air gaps or by one or more dielectric materials with high-breakdown voltages, such as Teflon, Kapton, and/or potting compound. In certain embodiments, the conductor wire segments2432can be electrically isolated from one another. Electrical currents can therefore be applied independently to each of the conducting wire segments2432.

The configuration of apparatus2400can eliminate a portion of the wires that might otherwise be positioned between the magnetic component and the shield (as shown inFIGS. 22 and 23, for example). To illustrate this,FIG. 24Bshows a schematic diagram of a cross-sectional view of the apparatus2400according to coordinate2492. The conducting wire segments2432are electrically connected to the shield2481with the absence of wire portions below the magnetic component220in the negative C-direction (i.e., between magnetic component220and shield2481). This configuration can lead to a lighter weight and more compact apparatus due to the absence of the wire portions.

Referring again toFIG. 24A, the magnetic component220can include gaps422between magnetic elements (not shown inFIG. 24A). The coil segments2432can generate magnetic fields oscillating in the B-direction within the gaps422. Accordingly, shield2481can include openings of the type described herein to reduce the penetration of magnetic fields in the gap regions into the shield. To illustrate this,FIG. 24Cshows the shield2481viewed in the positive C-direction according to coordinate2493. Dashed line2483corresponds to the magnetic component220shown inFIG. 24A.

The shield2481includes multiple openings560which are aligned to respective gaps422depicted inFIG. 24A. Gap422at the center of the magnetic component220is not shown inFIG. 24A. Accordingly, similar to other embodiments, the shield2481can have one or more openings or notches aligned to gaps or hot spots in the magnetic component220to reduce or eliminate power dissipation and energy losses in the shield2481by penetrating magnetic fields.

The disclosed techniques can be implemented during a manufacturing process of an apparatus (e.g., power transmitting apparatus, power receiving apparatus, power repeating apparatus) utilized in a wireless power transfer system. For example, the type of magnetic elements and arrangement can be selected to form a magnetic component. The arrangement defines the location and positions of gaps between the magnetic elements. In some embodiments, the shape and position of one or more coils with respect to the magnetic component can be determined. During manufacture, currents are directed through the one or more coils, and the temperature distribution of the magnetic component is measured. The measured temperature distribution indicates the generated magnetic field distribution and presence of hot spots. The magnitude and phases applied to the one or more coils can be controlled to make the temperature distribution more uniform and reduce the hot spots as described herein. In certain embodiments, the shape and position of the one or more coils can be adjusted to make the temperature distribution and the magnetic field distribution more uniform.

During the manufacturing process, a shield can be placed adjacent to the magnetic component. The location and shape of one or more openings of the shield can be determined based on the measured temperature distribution. For example, the one or more openings of the shield can be positioned to be aligned with regions of high temperature of the magnetic component. The shape of the one or more openings can be selected to conform to the high temperature regions of the magnetic component. For example, the one or more openings can be shaped to conform to regions with temperatures above a threshold value. Such threshold value can be predetermined from separate measurements for different types of magnetic elements, where the threshold value is identified to be below the damaging temperature of the specific type of magnetic element. In some embodiments, the depth of the one or more openings can depend on the measured temperature distribution. For example, an opening aligned with a region of higher temperature can have a larger depth compared to another opening with a region of lower temperature. This is because the induced magnetic fields can extend further for the region with higher temperature.

The above-mentioned processes can be implemented while assembling the wireless power transfer system. In certain embodiments, a calibration measurements can be carried out the relation between the type, shape, arrangement of magnetic elements, the shape, positioning of coils, the magnitude and phases of applied currents, the induced temperature distribution and high temperature threshold values. The data obtained by the calibration measurements can be saved in a library (e.g., electronic database), which can be used as a reference during assembly of the system. The temperature measurements can utilize temperature sensors which are attached to various locations of the apparatus being measured. In some embodiments, the temperatures sensor can be a camera (e.g., infra-red camera) to capture a thermal image.

Furthermore, the above mentioned techniques can be implemented after the manufacture of the apparatus. For example, during operation or maintenance of the system, a user can measure the temperature distribution and control parameters of the system. The user can control the magnitude and phase of applied currents to make the temperature distribution more uniform. In certain embodiments, the location, shape and depth of the openings can be reconfigured to conform to the change of temperature distribution over time. The reconfigured can be achieved by, for example, molding, milling and/or moving parts of the shield by actuators. These processes be implemented during wireless power transfer of the system. These approaches can be used to maintain the system to operate under efficient power transfer and nonhazardous conditions and allow the system to be robust to changes in the coils, magnetic component and/or shield caused by vibration, thermal shocks and mechanical shocks.

These techniques can be used to take into account the fabrication imperfections of the magnetic component, coils and shield. For example, the magnetic component may have an imperfect surface after fabrication and the operation parameters of the can be set to take such imperfection into account to have more uniform field distribution. Moreover, the techniques can be used to take into account any imperfections of the elements (e.g., magnetic component, coils, shield) arising due to use of the elements over time.

The disclosed techniques can be implemented for low operating frequencies where a shield can have higher loss properties than at high operating frequencies. The operating frequency of a wireless power transfer system can be chosen as the frequency of minimum loss of the combined contribution of losses of an apparatus including elements such as a shield, coil, magnetic component and electronics such as amplifiers and DC-AC converters of the system. For example, the shield can have lower losses as the operating frequency increases, and the coil can have lower losses as long as the frequency is low enough that radiative losses in the coil are lower than ohmic losses in the coil. On the other hand, the electronics can have higher losses as the operating frequency increases. An optimum frequency can exist where the combined losses can be minimum. In addition, the operating frequency of a wireless power transfer system may be chosen to exist within certain pre-specified frequency bands determined by a regulatory agency, a standards committee, a government or military organization. In some cases, the coil and shield designs are optimized to operate at a specified frequency and/or within a certain frequency range. For example, such an operating frequency can be about 85 kHz. As the shield can have higher losses at 85 kHz than at higher frequencies, the disclosed techniques can be used to have one or more openings in the shield to reduce losses induced within the shield. In some embodiments, the operating frequency can be at about 145 kHz. In high power applications, the losses of the electronics are typically lower for operating frequencies below 200 kHz, and thus certain high power applications are designed to operate at 20 kHz, 50 kHz, 85 kHz, and 145 kHz. In low power applications (e.g., low power consumer electronics), certain applications are designed to operate at the Industrial, Scientific and Medical (ISM) frequencies, where conducted and radiated emissions are not subject to regulatory restrictions. The ISM frequencies include 6.78 MHz, 13.56 MHz and many harmonics of 13.56 MHz.

Techniques described in relation toFIGS. 2-24Ccan be applied to a power receiving apparatus. For example, a power receiving apparatus can include a coil, a shield and a magnetic component which has gaps between its magnetic elements. Hence, the power receiving apparatus can experience similar magnetic field penetration into the shield leading to energy loss, as described herein in relation to a power transmitting apparatus. Therefore, the techniques described above in relation to a power transmitting apparatus are equally applicable to a power receiving apparatus.

Techniques described in relation toFIGS. 2-24Ccan be applied to a power repeating apparatus. For example, a power repeating apparatus can include a coil, a shield and a magnetic component, which has gaps between its magnetic elements. Hence, the power repeating apparatus can experience similar magnetic field penetration into the shield leading to energy loss, as described herein in relation to a power transmitting and power receiving apparatuses. The techniques described above in relation to a power transmitting apparatus and a power receiving apparatus are equally applicable to a power repeating apparatus, which wirelessly receives power from one apparatus and wirelessly transfer power to another apparatus.

Quality Factors and Operating Conditions

Generally, wireless power transfer may occur between the source and receiver resonators by way of multiple source resonators and/or multiple device resonators and/or multiple intermediate (also referred as “repeater” or “repeating”) resonators.

The source resonators, receiver resonators, and repeater resonators disclosed herein can each be an electromagnetic resonator capable of storing energy in fields (e.g., electric fields, magnetic fields). Any one of the resonators can have a resonant frequency f=ω/2π, an intrinsic loss rate Γ, and a Q-factor Q=ω/(2Γ) (also referred as “intrinsic” quality factor in this disclosure), where ω is the angular resonant frequency. A resonator can have a capacitance (C) and inductance (L) that defines its resonant frequency f according to equation 1 (Eq. (1)) below:

In some embodiments, any one of a source resonator, a receiver resonator, and/or a repeater resonator can have a Q-factor that is a high Q-factor where Q>100 (e.g., Q>100, Q>200, Q>300, Q>500, Q>1000). For example, a wireless power transfer system can include one or more source resonators, and at least one of the source resonators having a Q-factor of Q1>100 (e.g., Q1>200, Q1>300, Q1>500, Q1>1000). The wireless power transfer system can include one or more receiver resonators, and at least one of the receiver resonators can have a Q-factor of Q2>100 (e.g., Q2>200, Q2>300, Q2>500, Q2>1000). The wireless power transfer system can include one or more repeater resonators, and at least one of the repeater resonators can have a Q-factor of Q3>100 (e.g., Q3>200, Q3>300, Q3>500, Q3>1000).

Utilizing high Q-factor resonators can lead to large energy transfer efficiency between at least some or all of the resonators in the wireless power transfer system. Resonators with high Q-factors can couple strongly to other resonators such that the “coupling time” between resonators is shorter than the “loss time” of the resonators. As a result, the energy transfer rate between resonators can be larger than the energy dissipation rate of individual resonators. Energy can therefore be transferred efficiently between resonators at a rate higher than the energy loss rate of the resonators, which arises from heating and radiative losses in the resonators.

In certain embodiments, for a source-receiver resonator pair with Q-factors Qiand Qj(i=1, j=2), for a source-repeater resonator pair with Q factors Qiand Qj(i=1, j=3), and/or for a receiver-repeater resonator pair with Q factors Qiand Qj(i=2, j=3), a geometric mean √{square root over (QiQj)} can be larger than 100 (e.g., √{square root over (QiQj)}>200, √{square root over (QiQj)}>300, √{square root over (QiQj)}>500, √{square root over (QiQj)}>1000). Any one of the source, receiver, and repeater resonators can include one or more of the coils described in the following sections. High-Q resonators and methods for transferring power using such resonators are described, for example, in commonly owned U.S. patent application Ser. No. 12/567,716, published as US Patent Application Publication 2010/0141042, and issued as U.S. Pat. No. 8,461,719 on Jun. 11, 2013; U.S. patent application Ser. No. 12/720,866, published as US Patent Application Publication 2010/0259108, and issued as U.S. Pat. No. 8,587,155 on Nov. 19, 2013; U.S. patent application Ser. No. 12/770,137, published as U.S. Patent Application Publication 2010/0277121; U.S. patent application Ser. No. 12/860,375, published as US Patent Application Publication 2010/0308939; U.S. patent application Ser. No. 12/899,281, published as US Patent Application Publication 2011/0074346; U.S. patent application Ser. No. 12/986,018, published as U.S. Patent Application Publication 2011/0193416; U.S. patent application Ser. No. 13/021,965, published as US Patent Application Publication 2011/0121920; U.S. patent application Ser. No. 13/275,127, published as US Patent Application Publication 2012/0119569; U.S. patent application Ser. No. 13/536,435, published as US Patent Application Publication 2012/0313742; U.S. patent application Ser. No. 13/608,956, published as US Patent Application Publication 2013/0069441; U.S. patent application Ser. No. 13/834,366, published as US Patent Application Publication 2013/0221744; U.S. patent application Ser. No. 13/283,822, published as US Patent Application Publication No. 2012/0242225, issued as U.S. Pat. No. 8,441,154 on May 14, 2013; U.S. patent application Ser. No. 14/059,094; and U.S. patent application Ser. No. 14/031,737. The contents of each of the foregoing applications are incorporated herein by reference.

In some embodiments, a resonator of any of the types disclosed herein (e.g., source, receiver, repeater resonators) can include a coil formed of a conductive material. In certain embodiments, the resonator can have a resonance with a resonant frequency defined by an inductance and capacitance of the coil as described by Eq. (1) In this disclosure, the coil is also referred to interchangeably as a “coil structure.”

In certain embodiments, the coil can be connected to at least one capacitor, and the resonator can have a resonance with a resonator frequency defined by a combined inductance and combined capacitance of the coil-capacitor structure as described by Eq. (1) In this disclosure, the combination of the coil and the capacitor is also referred to interchangeably as a “coil-capacitor structure.”

In certain embodiments, an apparatus can include a coil wound around or positioned above and/or near-by a magnetic component (e.g., ferrite material). The magnetic component can enhance an induced magnetic flux density and can shield from nearby absorbing materials to reduce energy losses by such materials. In this disclosure, the combination of the coil and the magnetic component is also referred to interchangeably as a “coil-magnetic component structure.” A coil-magnetic component structure may or may not include a capacitor connected to the coil. A coil-magnetic component structure can have a resonant frequency defined by a combined inductance and combined capacitance of the coil structure and the magnetic component, or the coil-capacitor structure and the magnetic component, and a quality factor. In this disclosure, the quality factor Qtotalof the coil-magnetic component structure, Qtota, can be expressed according to:

1Qtotal=Rtotalω⁢⁢Ltotal=1Qcoil+1Qμ=Rcoilω⁢⁢Ltotal+Rμω⁢⁢Ltotal,(2)
where Rtotaland Ltotalis the total effective resistance and inductance of the coil-magnetic component structure, respectively. Rcoiland Rμare the effective resistance contributed by the coil and the magnetic component, respectively. In Eq. (2), Qcoilcan be considered as the quality factor of the configuration assuming a lossless magnetic component, and Qμcan be considered as the quality factor contributed by the magnetic component (e.g., ferrite material) with its loss to the coil structure or the coil-capacitor structure.

In some embodiments, a power transmitting apparatus can include a coil-magnetic component structure, and a shield positioned adjacent to the coil-magnetic component structure. Such a power transmitting apparatus can be described to have a quality factor Qtrans. When the shield is present, the quality factor Qtransof the power transmitting apparatus can be different from the quality factor Qtotalof the coil-magnetic component structure (when isolated from the shield) due to the shield perturbing the quality factor, i.e., because the shield alters the magnetic field distribution and therefore the effective inductance of the coil-magnetic component structure. Taking into account the contributions from the shield, the quality factor Qtranscan be expressed as:

1Qtrans=Rtotalω⁢⁢Ltotal=1Qcoil′+1Qμ′+1Qshield=Rcoilω⁢⁢Ltotal+Rμω⁢⁢Ltotal+Rshieldω⁢⁢Ltotal,(3)
where Rtotaland Ltotalis the total effective resistance and inductance of the configuration including the coil-magnetic component structure and the shield, respectively. The parameters described in Eq. (3) can be different from that described in Eq. (2). For example, Ltotalin Eq. (3) can be different from that in Eq. (2). Rcoil, Rμand Rshieldare the effective resistances contributed by the coil, the magnetic component and the shield, respectively. Rcoiland Rμmay be the same as in Eq. (2), when assumed that they are not affected by the presence of the shield. In Eq. (3), Q′coilcan be considered as the quality factor of the configuration assuming a lossless magnetic component and a lossless shield. Q′μcan be considered as the quality factor contributed by the magnetic component with its loss and assuming a lossless shield. In this disclosure, Qshieldis referred to as a quality factor contributed by the shield.

In some embodiments, Qtranscan be measured or calculated. Rtotaland Ltotalcan be calculated from the obtained Qtrans. Another measurement or calculation without the presence of the shield can be carried out to obtain Rcoil+Rμin Eq. (3) assuming they are not affected by the presence of the shield. Then, Rshieldcan be calculated by subtracting Rcoil+Rμfrom Rtotal. Further, Qshieldcan be obtained using the calculated Rshieldand Ltotalbased on the relations described in Eq. (3).

Hardware and Software Implementation

FIG. 25shows an example of an electronic controller103, which may be used with the techniques described here. As mentioned earlier, the electronic controller103can be used to control power transfer of a wireless power transferring system, for example, by changing power output of a power source, adjusting operation and/or resonant frequencies and adjusting impedance matching networks. In some embodiments, the electronic controller103can be directly connected to or wirelessly communicate with various elements of the system.

Electronic controller103can include a processor2502, memory2504, a storage device2506and interfaces2508for interconnection. The processor2502can process instructions for execution within the electronic controller103, including instructions stored in the memory2504or on the storage device2506. For example, the instructions can instruct the processor2502to determine parameters of the system such as efficiency of power transfer, operating frequency, resonant frequencies of resonators and impedance matching conditions. In certain embodiments, the processor2502is configured to send out control signals to various elements (e.g., power source, power transmitting apparatus, power receiving apparatus, power repeating apparatus, impedance matching networks) to adjust the determined parameters. For example, control signals can be used to tune capacitance values of capacitors in an impedance matching network. In certain embodiments, control signals can be used to adjust operation frequency of a power source. Control signals can change capacitance value of a capacitor in a resonator to tune its resonant frequency.

The memory2504can store information of optimized parameters of the system. For example, the information can include optimized impedance matching conditions for various levels of power output from the power source. In certain embodiments, the memory2504can store information such as resonant frequencies of resonator and magnetic properties (e.g., magnetic permeability depending on power levels) of magnetic components in the system, which can be used by the processor2502for determining signals to be sent out to control various elements in the system.

The storage device2506can be a computer-readable medium, such as a floppy disk device, a hard disk device, an optical disk device, or a tape device, a flash memory or other similar solid state memory device, or an array of devices, including devices in a storage area network or other configurations. The storage device2506can store instructions that can be executed by processor2502described above. In certain embodiments, the storage device2506can store information described in relation to memory2504.

In some embodiments, electronic controller103can include a graphics processing unit to display graphical information (e.g., using a GUI or text interface) on an external input/output device, such as display2516. The graphical information can be displayed by a display device (device (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor) for displaying information. A user can use input devices (e.g., keyboard, pointing device, touch screen, speech recognition device) to provide input to the electronic controller103. In some embodiments, the user can monitor the display2516to analyze the power transfer conditions of the system. For example, when the power transfer is not in optimum condition, the user can adjust parameters (e.g., power transfer level, capacitor values in impedance matching networks, operation frequency of power source, resonant frequencies of resonators) by inputting information through the input devices. Based on the receive input, the electronic controller103can control the system as described above.

In some embodiments, the electronic controller103can be used to monitor hazardous conditions of the system. For example, the electronic controller103can detect over-heating in the system and provide an alert (e.g., visual, audible alert) to the user through its graphical display or audio device.

In certain embodiments, electronic controller103can be used to control magnitudes and phases of currents flowing in one or more coils of the wireless power transfer system. For example, processor2502can calculate and determine the magnitudes and phase of currents to be supplied to coils in a power transmitting apparatus. The determination can be based on the monitored power transfer efficiency and information stored in memory2504or storage2506.

A feedback signal can be received and processed by the electronic controller103. For example, the electronic controller103can include a wireless communication device (e.g., radio-frequency, Bluetooth receiver) to receive information from either or both of a power transmitting apparatus and a power receiving apparatus (which can have its own wireless communication device). In some embodiments, the received information can be processed by processor2502, which can further send out control signals to adjust parameters of the system as described above. For example, the control signals can be used to adjust the magnitudes and phases of currents flowing in one or more coils of resonators in the system to increase the power transfer efficiency.

Various embodiments of the systems and techniques described here can be realized by one or more computer programs that are executable and/or interpretable on the electronic controller103. 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. For example, computer programs can contain the instructions that can be stored in memory2504and storage2506and executed by processor2502as described above. As used herein, the terms “computer-readable medium” refers to any computer program product, 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.

Generally, electronic controller103can be implemented in a computing system to implement the operations described above. For example, the computing system can include a back end component (e.g., as a data server), or a middleware component (e.g., an application server), or a front end component (e.g., a client computer having a graphical user-interface), or any combination therefor, to allow a user to utilized the operations of the electronic controller103.

The electronic controller103or one or more of its elements can be integrated in a vehicle. The electronic controller103can be utilized to control and/or monitor wireless power charging of a battery installed in the vehicle. In some embodiments, the display2516can be installed adjacent to the driving wheel of the vehicle so that a user may monitor conditions of the power charging and/or control parameters of the power charging as described in relation toFIG. 25. The display2516can also visualize information traffic information and road maps based on Global Positioning System (GPS) information. Any of the elements such as the processor2502, memory2504and storage device2506can be installed in the space behind the display2516, which can visualize the data process by those elements.

In addition to the embodiments disclosed herein, other embodiments are within the scope of the disclosure.