Variable magnetic layer for wireless charging

Abstract

A magnetic film assembly includes a coil including a plurality of turns defining a first major boundary surface of the coil such that, when energized, the coil generates a planar magnetic field component in a region of interest in air proximate and substantially parallel to the first major boundary surface, the planar magnetic field component having a magnetic field strength H in the region of interest in air that varies between a maximum value Hmax and about 10% of Hmax; and a magnetic layer disposed on the coil so as to encompass the region of interest such that, when energized, the coil generates a magnetic field that induces a planar magnetic flux density B in the magnetic layer in the region of interest, the variation in the magnetic flux density in the region of interest being less than about 5%.

Description

SUMMARY

[0001] In some aspects of the description, a magnetic film assembly is provided that includes a coil having a plurality of turns defining a first major boundary surface of the coil such that, when energized, the coil generates a planar magnetic field component in a region of interest in air proximate and substantially parallel to the first major boundary surface, the planar magnetic field component having a magnetic field strength H in the region of interest in air that varies between a maximum value Hmax and about 10% of Hmax; and a magnetic layer disposed on the coil so as to include the region of interest such that, when energized, the coil generates a magnetic field that induces a planar magnetic flux density B in the magnetic layer in the region of interest, the variation of B in the region of interest being less than about 5%.

[0002] In some aspects of the description, a magnetic film assembly is provided that includes a coil including an electrically conductive wire wound to form a plurality of substantially concentric loops; and a magnetic layer disposed on the coil and having a non-uniform thickness and a saturation magnetic flux density Bs such that, when energized, the coil generates a magnetic field that induces a planar magnetic flux density B in the magnetic layer, the non-uniformity of the thickness of the magnetic film resulting in B being less than about 1.1 times Bs in a region of interest of the magnetic layer.

[0003] In some aspects of the description, a magnetic film is provided that includes a plurality of magnetic tiles arranged along a first in-plane direction of the magnetic film and stacked along a thickness direction of the magnetic film to define a plurality of stacked magnetic tiles arranged along the first direction such that a number of magnetic tiles in the stacked magnetic tiles varies along the first direction.

[0004] In some aspects of the description, a magnetic film is provided that includes a plurality of layers arranged along a thickness direction of the magnetic film, each layer including a plurality of substantially planar magnetic tiles arranged on the layer, wherein at least two of the plurality of layers have a different number of magnetic tiles arranged on the corresponding layer.

[0005] In some aspects of the description, a magnetic film is provided that includes a plurality of discrete individual magnetic pieces arranged along width, length, and thickness directions of the magnetic film, the magnetic film including a central region proximate a center of the magnetic film, a peripheral region proximate a peripheral edge of the magnetic film, and an intermediate region disposed between the central region and the peripheral region, the magnetic film having average thicknesses Tcen, Tmid, Tper in the respective central, intermediate, and peripheral regions such that Tmid is greater than Tcen and Tper.

[0006] In some aspects of the description, a magnetic film assembly is provided, the magnetic film assembly comprising a magnetic source configured to produce an in-plane magnetic field component in a region of interest in air proximate the magnetic source, the in-plane magnetic field component having a magnetic field strength H, the magnetic field strength having a larger value at a first location in the region of interest and a smaller value at a second location in the region of interest; and a magnetic film disposed on the magnetic source so as to encompass the region of interest, the magnetic film being thicker at the first location and thinner at the second location.

[0007] In some aspects of the description, a system for wireless power transfer is provided, the system comprising a power receiving assembly comprising a first magnetic film disposed between a first metal plate and a power receiving antenna; and a power transmitting assembly facing the power receiving assembly and comprising a second magnetic film disposed between a second metal plate and a power transmitting antenna, the power receiving antenna and the power transmitting antenna facing and substantially aligned with each other such that, when energized, the power transmitting antenna wirelessly transfers power to the power receiving antenna, wherein at least one of the first magnetic film and the second magnetic film comprises a plurality of stacked tiles arranged along a width and a length of the magnetic film, each stacked tile comprising a plurality of tiles stacked along a thickness direction of the magnetic film, wherein at least two of the plurality of stacked tiles have different numbers of tiles.

[0008] In some aspects of the description, a magnetic film is provided, the magnetic film comprising a plurality of tiles arranged along orthogonal first and second in-plane directions of the magnetic film and stacked along a thickness direction of the magnetic film to define a plurality of stacked tiles, at least two of the plurality of tiles having two different magnetic materials having two different relative magnetic permeabilities at the same frequency, the thickness of the magnetic film varying by less than about 20% such that, when the magnetic film is disposed on a coil and the coil is energized to produce a magnetic field, for at least one tile having a saturation magnetic flux density Bs, the magnetic field induces an in-plane magnetic flux density B in the magnetic film, the different magnetic materials in the magnetic film causing B to be less than about 1.2 Bs in the at least one tile.

[0009] In some aspects of the description, a magnetic film is provided, the magnetic film comprising a plurality of discrete magnetic segments arranged along a length and a width of the magnetic film, the segments being substantially identical in composition, wherein at least two of the magnetic segments have different thicknesses.

[0010] In some aspects of the description, a magnetic film is provided, the magnetic film comprising a plurality of discrete magnetic segments arranged along a length and a width of the magnetic film, the segments being substantially identical in thickness, wherein at least two of the magnetic segments have different magnetic permeabilities.

[0011] In some aspects of the description, a magnetic film is provided such that a substantially planar coil, when energized, generates a magnetic field that is substantially directed along a line of interest at opposite first and second end points of the line of interest and substantially normal to the line of interest at an intermediate point between the first and second end points, if the magnetic film is disposed on the coil so as to be substantially parallel to the coil and to include the line of interest, then the coil, when energized, generates a magnetic flux density B that is at least substantially directed along the line of interest at the first and second end points and at the intermediate point of the line. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figures 1A-1B An alternative view of a magnetic film assembly is shown in accordance with an embodiment of the description;

[0013] Figures 2A-2B An alternative view of a spiral coil for a magnetic film assembly is shown in accordance with an embodiment of the description;

[0014] Figure 3 A top view of a spiral coil for a magnetic film assembly is shown in accordance with an embodiment of the description;

[0015] Figures 4A-4C An alternative view of an electrical conductor is shown in accordance with an embodiment of the description;

[0016] Figure 5 A plot of magnetic field strength (H) versus magnetic flux density (B) is shown in accordance with an embodiment of the description;

[0017] Figures 6A-6B An alternative view of a variable thickness magnetic layer is shown in accordance with an embodiment of the description;

[0018] Figure 7 A side view of a multi-layer magnetic film is shown in accordance with an embodiment of the description;

[0019] Figure 8 A top view of a variable thickness magnetic layer is shown in accordance with an embodiment of the description;

[0020] Figure 9 A side cross-sectional view of a system for wireless power transfer is shown in accordance with an embodiment of the description;

[0021] Figure 10 A side cross-sectional view of a magnetic film is shown in accordance with an embodiment of the description;

[0022] Figures 11A-11B A side cross-sectional view of a variation of a magnetic film is shown in accordance with an alternative embodiment of the description; and

[0023] Figures 12A-12B A plot of magnetic field strength and magnetic flux density of a magnetic film assembly is shown in accordance with one embodiment of the present specification. DETAILED DESCRIPTION

[0024] In the following description, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration various embodiments. The drawings are not necessarily to scale. It is to be understood that other embodiments can be utilized and structural or logical changes can be made without departing from the scope or spirit of the present specification. The following detailed description, therefore, is not to be taken in a limiting sense.

[0025] The present application relates to wireless charging applications in which energy is transferred from a power transmitting device (e.g., a wireless charging station) to a power receiving device (e.g., a mobile device, an electric vehicle, etc.). Typically, wireless power transfer occurs between an induction coil that can generate an alternating electromagnetic field in a charging device and a receiving coil disposed in a charged device in proximity to the charging device. When the receiving coil is placed within the electromagnetic field of the charging coil, a current is generated from the electromagnetic field (i.e., the electromagnetic field induces a current in the receiving coil), which is used to charge a battery or a power cell within the device.

[0026] Due to magnetic field leakage into the environment, particularly into metals, wireless charging systems can suffer from low efficiency. For example, the magnetic flux in a wireless charging system can induce eddy currents on nearby conductive surfaces and generate “competing” fields that can interfere with and reduce the efficiency of the electromagnetic field of the charging coil. In this regard, one potential solution is to place a ferrite layer (e.g., a magnetic shielding film) between the receiving coil and the nearby conductive surface. Relative to having no ferrite layer at all, this ferrite layer can reduce the magnetic field reaching the conductive surface, thereby improving overall efficiency. However, the magnetic field strength H and the magnetic flux density B of the entire coil assembly are not uniform. Typically, the in-plane field strength is significantly larger over the conductors (i.e., turns of the coil) and smaller at the center and edges of the ends of the conductors, which results in low charging system efficiency. While placing a ferrite layer (such as a shielding film) of uniform thickness over the coil assembly can effectively prevent magnetic field leakage into the environment, the thickness of the entire ferrite layer must be based on the point of the highest magnetic field strength generated by the coil. In other words, the same thickness of ferrite material is applied uniformly over the coil assembly, which only requires a thin layer of ferrite (or not at all) even in areas of weak magnetic field strength.

[0027] According to some aspects of the present specification, a method of applying a variable thickness layer of ferrite (magnetic) material on a coil assembly is provided, with thicker or additional ferrite material provided in areas of the coil that exhibit high magnetic field strength, and thinner material provided in areas that exhibit low magnetic field strength. By using a variable thickness magnetic layer, significant cost savings and weight reduction (shown in experiments to be at least 35%) can be achieved while providing substantially the same system level efficiency (e.g., less than 1% reduction in efficiency).

[0028] In some embodiments, a magnetic film assembly (e.g., a wireless charging system) includes a coil having a plurality of turns and a magnetic layer (e.g., a ferrite layer or a magnetic shielding film) disposed on the coil. In some embodiments, a first major boundary surface of the coil is defined such that, when energized (i.e., when an electrical current passes through the coil), the coil generates an in-plane magnetic field component in a region of interest in air proximate to and substantially parallel to the first major boundary surface. In some embodiments, the in-plane magnetic field component can have a magnetic field strength H that varies between a maximum value Hmax and a minimum value in the region of interest in air, the minimum value being approximately equal to 10% of Hmax (when the magnetic layer is not present). In some embodiments, when the magnetic layer is disposed on the coil so as to encompass the region of interest (i.e., the region of interest is covered by and enclosed within the magnetic layer), the coil can generate, when energized, a magnetic field that induces an in-plane magnetic flux density B in the magnetic layer in the region of interest such that a variation of B in the region of interest is less than approximately 5%. In some embodiments, the magnetic layer substantially covers the entire coil when the assembly is shown in plan view. In some embodiments, the magnetic layer covers only a portion of the coil when shown in plan view.

[0029] In some embodiments, the coil can be substantially planar, and the first major boundary surface can be a substantially planar surface (e.g., a substantially planar top surface of the planar coil). In some embodiments, the coil can define a substantially planar second major boundary surface of the coil (e.g., a substantially planar bottom surface of the planar coil) on an opposite surface of the planar coil, the second major boundary surface being substantially parallel to the first major boundary surface.

[0030] In some embodiments, the coil can be substantially a spiral coil, where the first major boundary surface is a substantially cylindrical outer surface (i.e., a cylindrical surface surrounding an exterior of the coil). In some embodiments, the coil can define a substantially cylindrical inner boundary surface of the coil opposite to and substantially concentric with the first major boundary surface.

[0031] According to some aspects of the present specification, a magnetic film assembly includes a coil (e.g., a charging coil or a receiving coil of a wireless charging system) and a magnetic layer disposed on the coil, the coil being composed of an electrically conductive wire wound to form a plurality of substantially concentric loops. In some embodiments, the magnetic layer can have a non-uniform thickness and exhibit a saturation magnetic flux density Bs. When energized, the coil can generate a magnetic field that induces an in-plane magnetic flux density B in the magnetic layer such that the non-uniformity of the thickness of the magnetic film results in B being less than about 1.1 times Bs, or less than about 1.0 times Bs, or less than about 0.8 times Bs, or less than about 0.5 times Bs in a region of interest of the magnetic layer (e.g., a region of interest substantially parallel to and above an outer surface of the coil).

[0032] In some embodiments, the coil can have a thickness Tc and the electrically conductive wire can have a thickness Tw such that the ratio Tc / Tw is less than about 1.5 (e.g., for a substantially planar spiral coil). In some embodiments, the coil thickness Tc and the wire thickness Tw can be such that the ratio Tc / Tw is greater than about 2 (e.g., for a spiral coil). In some embodiments, the electrically conductive wire can be a non-insulated wire. In some embodiments, the electrically conductive wire can have an electrically conductive inner core surrounded by an insulating layer (e.g., a dielectric material). In some embodiments, the electrically conductive wire can be a stranded wire (i.e., a plurality of electrically conductive wires surrounded by an insulating layer).

[0033] According to some aspects of the present specification, a magnetic film includes a plurality of magnetic tiles arranged along a first in-plane direction of the magnetic film (e.g., the x-axis) and stacked along a thickness direction of the magnetic film to define a plurality of stacked tiles arranged along the first direction (i.e., tiles in stacks, where each stacked tile can include one or more tiles). In some embodiments, the number of tiles in a stacked tile varies along the first direction.

[0034] Smaller ferrite tiles are often used to form larger continuous ferrite layers. In some embodiments, the tiles can be made of one or more materials including, but not limited to, soft magnetic conductive ferrite, magnetic conductive metal, magnetic conductive crystalline alloy, magnetic conductive nanocrystalline alloy, magnetic conductive amorphous alloy, and magnetic conductive composite. In some embodiments, the tiles can be ferrite tiles, such as ferrite tiles used in electric vehicle charging systems. In some embodiments, the tiles can be tiles of a magnetic shielding film. One embodiment of a tile is a 3M™ Flux Field Directional Material (FFDM), such as the EM15TF series of materials manufactured by 3M Company. In some embodiments, one or more tiles of the plurality of tiles can include a plurality of layers, where at least two layers are magnetic layers.

[0035] In some embodiments, the magnetic tiles can also be arranged along a second in-plane direction (e.g., y-axis) of the magnetic film that is orthogonal to the first in-plane direction, and stacked along a thickness direction (e.g., z-axis) of the magnetic film to define a plurality of stacked magnetic tiles arranged along the second direction, such that the number of magnetic tiles in the stacked magnetic tiles varies along the second direction.

[0036] According to some aspects of the present specification, a magnetic film includes a plurality of layers arranged along a thickness direction of the magnetic film, each layer including a plurality of substantially planar magnetic tiles arranged on the layer, wherein at least two of the plurality of layers have different numbers of magnetic tiles arranged on the corresponding layer. In some embodiments, each layer can have substantially the same thickness. In some embodiments, each magnetic tile of the plurality of layers can have substantially the same thickness. In some embodiments, each magnetic tile can include a plurality of magnetic layers (e.g., magnetic film layers, disposed to form each magnetic tile). In some embodiments, each magnetic layer can be disposed on a corresponding substrate, which can be a non-magnetic substrate. In some embodiments, each magnetic tile can include a bonding layer (e.g., a bonding film layer) that bonds adjacent magnetic layers to each other. In some embodiments, at least some of the magnetic tiles can have different shapes and / or different relative sizes.

[0037] According to some aspects of the present specification, a magnetic film can include a plurality of discrete individual magnetic pieces (e.g., magnetic tiles) arranged along width, length, and thickness directions of the magnetic film. In some embodiments, the magnetic film can include a central region proximate to a center of the magnetic film, a peripheral region proximate to an edge of the magnetic film, and an intermediate region between the central region and the peripheral region, such that the central region, the intermediate region, and the peripheral region have respective average thicknesses Tcen, Tmid, and Tper. In some embodiments, Tmid is greater than Tcen and Tper (i.e., the stack of magnetic tiles arranged proximate to the center and the outer edge is shorter compared to the intermediate region).

[0038] According to some aspects of the present specification, a magnetic film assembly can include a magnetic source (e.g., a coil electrically coupled to a power source) and a magnetic film. In some embodiments, the magnetic source can be configured to generate an in-plane magnetic field component in a region of interest in air proximate to the magnetic source. In some embodiments, the region of interest can be defined as a spatial region disposed proximate to and substantially parallel to the magnetic source (e.g., a spatial “layer” proximate to a substantially planar surface of the coil). In some embodiments, the in-plane magnetic field component can have a magnetic field strength (H) that has a larger value at a first location in the region of interest and a smaller value at a second location in the region of interest.

[0039] In some embodiments, a magnetic film can be disposed on a magnetic source so as to include a region of interest (i.e., the region of interest is substantially within the magnetic film). In some embodiments, the magnetic film can be thicker at a first location and thinner at a second location. In other words, the magnetic film can be thinner at locations of smaller H within the region of interest and thicker at locations of larger H.

[0040] According to some aspects of the present specification, a system for wireless power transfer (e.g., a wireless charging system for an electric vehicle or a handheld mobile device) can include a power receiving assembly and a power transmitting assembly facing the power receiving assembly. In some embodiments, the power receiving assembly can include a first metal plate, a power receiving antenna (e.g., a receiving coil), and a first magnetic film disposed between the first metal plate and the power receiving antenna. In some embodiments, the power transmitting assembly can include a second metal plate, a power transmitting antenna (e.g., a transmitting coil), and a second magnetic film disposed between the second metal plate and the power transmitting antenna.

[0041] In some embodiments, the power receiving antenna and the power transmitting antenna can face and be substantially aligned with each other. In some embodiments, when the power transmitting antenna is energized, the power transmitting antenna can wirelessly transfer power to the power receiving antenna. In some embodiments, at least one of the first magnetic film and the second magnetic film can include a plurality of stacked magnetic tiles arranged along a width and a length of the magnetic film. In some embodiments, each stacked magnetic tile can include a plurality of magnetic tiles stacked along a thickness direction of the magnetic film, wherein at least two stacked magnetic tiles have different numbers of magnetic tiles. In some embodiments, the height of the stacked magnetic tiles can vary as each stacked magnetic tile includes a different number of magnetic tiles.

[0042] According to some aspects of the present specification, a magnetic film can include a plurality of magnetic tiles arranged along orthogonal first and second in-plane directions (e.g., x and y axes) of the magnetic film and stacked along a thickness direction (e.g., z axis) of the magnetic film to define a plurality of stacked magnetic tiles. For example, in some embodiments, the magnetic film can be defined by rows and columns forming a rectangular grid, where each location in the rectangular grid can be formed by a different number of vertically stacked magnetic tiles. In some embodiments, at least two magnetic tiles have two different magnetic materials each having a different relative permeability when measured at the same frequency. In some embodiments, the thickness variation of the magnetic film can be less than about 20%. In some embodiments, for at least one magnetic tile having a saturation magnetic flux density Bs, when the magnetic film is disposed on a coil and the coil is energized to produce a magnetic field, the magnetic field induces an in-plane magnetic flux density B in the magnetic film such that the different magnetic materials in the magnetic film cause B to be less than about 1.2 times Bs, or about 1.0 times Bs, or about 0.8 times Bs, or about 0.4 times Bs in the at least one magnetic tile.

[0043] According to some aspects of this specification, the magnetic film includes a plurality of discrete magnetic segments arranged along the length (e.g., x-axis) and width (e.g., y-axis) of the magnetic film, the segments being substantially identical in composition (i.e., the same material), wherein at least two magnetic segments have different thicknesses (e.g., different heights in the z-axis). In some embodiments, the magnetic segments may be magnetic tiles with varying thicknesses. In some embodiments, the magnetic segments may be stacks of magnetic tiles, wherein each magnetic tile has substantially the same thickness, and wherein at least one stack may have a different number of magnetic tiles than at least one other stack.

[0044] According to some aspects of this specification, a substantially planar coil generates a magnetic field when energized, which, for a line of interest approaching and substantially parallel to the coil, can be substantially oriented along the line of interest at its opposing first and second endpoints and substantially orthogonal to the line of interest at a midpoint between the first and second endpoints. In some embodiments, a magnetic film can be disposed on the coil so as to be substantially parallel to the coil and encompass the line of interest, such that when energized, the coil can generate a magnetic flux density B that is substantially oriented along the line of interest at least at the first and second endpoints and the midpoint. For example, the line of interest can be positioned such that its midpoint coincides with the center of the coil, and its first and second endpoints are close to the outer edge of the coil (i.e., close to the outermost turn of the coil).

[0045] Now turn to the attached image. Figures 1A-1B An alternative view of one embodiment of the magnetic film assembly according to this specification is shown. Figure 1A A side cross-sectional view of the magnetic film assembly 100 is shown, including the coil 10 (in Figure 1A It is shown as a rectangular outline, but usually includes multiple turns, such as Figure 1B The coil 10 (shown as element 11) and magnetic layer 40. In some embodiments, magnetic layer 40 may be a magnetic film having a region of varying thickness and disposed substantially parallel to the first primary boundary surface 12 of the coil. In some embodiments, coil 10 defines a second primary boundary surface 13 on the surface of coil 10 opposite to the first primary boundary surface 12. In some embodiments, magnetic layer 40 may cover substantially all of coil 10 (i.e., substantially all of the first primary boundary surface 12). In some embodiments, magnetic layer 40 may cover only a portion of coil 10. In some embodiments, coil 10 may be electrically connected to power source 70 such that coil 10 can be energized (i.e., current flows through coil 10) so that coil 10 generates an electromagnetic field that can be used to wirelessly transfer power to a corresponding receiving coil (not shown).

[0046] In some embodiments, the magnetic layer 40 is positioned such that it covers and includes the region of interest 30, which for discussion purposes is defined in air above the coil 10, and not by the magnetic layer 40 itself. That is, the region of interest 30 is relative to the coil 10 Figure 10 defined, and when the magnetic layer 40 is disposed over the coil 10 so as to enclose the region of interest 30, the region of interest includes only within the magnetic layer 40. The region of interest 30 is defined as a reference region in which the behavior of the magnetic field generated by the coil 10 is considered for discussion purposes. For example, in some embodiments, when the coil 10 is energized, an in-plane magnetic field component 20 is generated within the region of interest 30. In some embodiments, the in-plane magnetic field component 20 can have a magnetic field strength (H) that varies over the coil 10 (e.g., stronger over the conductors making up the coil 10, weaker at the center and edges where there are no conductors). If Hmax represents the maximum magnetic field strength H seen over the coil 10, then H can vary within the region of interest by at least between Hmax and about 10% of Hmax. It should be noted that because the magnetic layer 40 is disposed over the coil 10, the magnetic field strength H is not seen by the region of interest 30. Figure 1A is a cross-sectional view, the region of interest 30 is represented by a two-dimensional rectangle. However, in practice, the region of interest 30 can be a three-dimensional volume, such as a rectangular prism (or any appropriate volume shape) extending in air over at least a portion of the coil 10.

[0047] In some embodiments, when the magnetic layer 40 is disposed over or near the coil 10 so that it includes the region of interest, the coil 10 (when energized) can generate a magnetic field that induces an in-plane magnetic flux density (B) 21 in the magnetic layer 40 within the region of interest 30 that varies by less than about 5% throughout the region of interest 30. More simply stated, the presence of the magnetic layer 40 positioned to cover the region of interest 30 forms a magnetic flux density 21 that is substantially uniform over the region of interest.

[0048] It should be noted that whether the thickness of the magnetic layer is constant or variable, a magnetic layer disposed over a coil generating a magnetic field will suppress and reduce the magnetic flux density B of the magnetic field generated by the coil, and can be used to reduce eddy current induction in surrounding structures (e.g., conductive metal structures such as on an electric vehicle). However, using a magnetic layer of constant (uniform) thickness over a magnetic field having a varying field strength H will result in a flux density B that is likewise variable, because the relationship of field strength H to flux density B is generally defined by B = μ r μ0H, where μ0 is a constant (the permeability of free space), and μ r is the relative permeability of the (nearby material). For smaller values of H, this equation defines a substantially linear relationship between B and H (as Figure 5such that when a constant thickness magnetic layer is used, the resulting B value is proportional to the varying H value (in some embodiments, varying between Hmax and about 10% of Hmax).

[0049] By using a magnetic layer of varying thickness (such as, for example, Figure 1A the magnetic layer 40 in FIG. 1), the magnetic layer can be formed such that its thicker portions cover areas with higher H values, and its thinner portions cover areas with relatively lower H values. That is, in the presence of a varying H field, a varying thickness magnetic layer can be used to produce a substantially uniform B field. This also has the effect of reducing the amount of material needed for the magnetic layer, reducing the cost and / or weight of the overall system without significantly reducing the efficiency of power transfer. When a constant thickness magnetic layer is employed, the thickness is determined by the maximum H field produced at one or both locations on the coil. However, by using a variable thickness magnetic layer, only enough material is needed at each location to ensure that the induced B field (local to that location) is sufficiently suppressed (and is substantially uniform from one location on the magnetic layer to the next).

[0050] Figure 1B An alternative perspective view of the magnetic film assembly 100 is shown, showing additional details on the coil 10 and magnetic film 40. In some embodiments, the coil 10 can be an electrically conductive wire 14 (or similar electrically conductive body) that is wound to form a series of substantially concentric turns or loops 15. In some embodiments, the coil 10 can be a printed circuit board (PCB) trace, or other similar electrically conductive body. Figure 1B In some embodiments, the configuration of the coil 10 is a spiral coil, but other configurations are possible (such as Figure 2A the spiral coil 10a of FIG. 1, discussed elsewhere herein).

[0051] In some embodiments, the magnetic layer 40 can be formed so as to have varying thickness regions 45, where the local thickness of each varying thickness region 45 is determined by the strength of the magnetic field H produced near the corresponding location on the coil 10. It should be noted that, Figure 1A and Figure 1B The exemplary configuration of the magnetic layer 40 shown in FIG. 1 is intended to demonstrate a magnetic layer with varying thickness, and the exact shape of the magnetic layer is not necessarily shown because it will be applied to the coil 10 to produce a substantially uniform B field as described elsewhere herein.

[0052] Figures 2A-2BAlternative embodiments of coils for use in magnetic film assemblies as described herein are shown. Coil 10a has a helical configuration, wherein the turns 15 of the conductive wire 14 are helical (similar to a DNA strand or a spiral ladder). In some embodiments, coil 10a may have a thickness Tc, and conductive wire 14 may have a thickness Tw, such that the ratio Tc / Tw is greater than about 2 (i.e., the overall coil height is at least twice the thickness of wire 14). Conversely, for helical coil configurations, such as... Figure 1B The coil 10 shown (or Figure 3 The ratio Tc / Tw of the coil 10b can be less than about 1.5 (i.e., the overall coil height is mainly limited by the thickness of the wire 14).

[0053] Go to Figure 2B A cross-sectional view, the accompanying drawing showing that the first main boundary surface 12a is defined by the cylindrical outer surface of the coil 10a (as opposed to the surface used for...). Figure 1A The first primary boundary surface 12a of the spiral coil 10 is substantially planar compared to the second primary boundary surface 13a, and the second primary boundary surface 13a is defined by the cylindrical inner surface of the coil 10a. That is, in some embodiments of the wireless charging system, the spiral power transmitting coils may be positioned close to and / or adjacent to the spiral power receiving coils, such that the first primary boundary surfaces 12a of each coil are close to each other (i.e., "cylinders" side-by-side), and any magnetic layer applied as described herein will be wound around at least a portion of at least one surface of the surface 12a, or may be positioned between the side-by-side coils. In some embodiments, two spiral coils may be positioned such that one spiral coil is higher than the other (i.e., like stacked "cylinders"). In this embodiment, the first primary boundary surface may be defined between the ends of the cylindrical coils (similar to...). Figure 1A The first main boundary surface 12 shown in the figure.

[0054] Figure 3 A top view of the helical coil of the magnetic film assembly according to this specification is shown. The helical coil 10b includes a conductive wire 14 wound in a helical manner to form a series of substantially concentric turns or loops 15. Figure 3 The spiral coil 10b shown is generally circular in shape, but other shapes and configurations are also possible, including, for example... Figure 1B The turn shown is roughly square. Figures 4A-4C Alternative embodiments of the conductors that can be used to generate the turns of a helical coil are shown. 14. Figure 4A A cross-sectional view of conductor 14a, which is a single uninsulated wire, is shown. Figure 4B A cross-sectional view of a conductor 14b is shown, which is a single conductor (wire) 14c encased in an outer insulating layer 14d. Figure 4CA cross-sectional view of the electrical conductor 14e is shown, which includes a plurality of conductors (wires) 14g that can be wrapped or woven within an outer insulating layer 14f. Other types of conductors 14 are possible and within the scope of the present disclosure. In some embodiments, the cross-sectional profile of the conductors can be circular (at least as shown in Figures 4A-4C FIG. 1), elliptical, square, rectangular, or any other appropriate profile shape.

[0055] Figure 5 A plot 1200 of magnetic flux density (B) versus magnetic field strength (H) is shown, which illustrates the importance of the magnetic layer. The plot 1200 (including 1200a / 1200b) is a plot of magnetic field strength H along the x-axis (i.e., horizontal axis) versus magnetic flux density B along the y-axis (i.e., vertical axis). As can be seen from the plot 1200, the B field increases sharply with increasing magnetic field strength H (see portion of plot labeled 1210a) until the system reaches a magnetic saturation point Bs. At this point, the increase in B is significantly reduced as H continues to increase (see plot segment 1210b). This is critical because once the system reaches magnetic saturation (when the B field reaches Bs or a significant portion thereof), the inductance of the coil suddenly decreases, and normal wireless charging operation can be reduced or completely fail. To prevent the system from reaching the magnetic saturation point, a magnetic layer (such as the magnetic layer 40 of Figure 1A FIG. 1) is provided near the coil to reduce the size of the resulting B field (so that the system remains well below the magnetic saturation point Bs). As previously mentioned, and based on the corresponding plot 1200 of the designed system, the magnetic layer can be formed with a variable thickness such that the B field at each location on the coil (and particularly within the region of interest 30 as shown in Figure 1A FIG. 1) remains below the level of the magnetic saturation point (and preferably at the low level of the 1210a portion of the plot 1200). In other words, if the designed magnetic layer is assumed to be substantially planar and represented by a grid of points in the x-y plane (see, e.g., the magnetic layer 200 shown in Figure 6B FIG. 2), the thickness at each x-y location on the grid can be selected such that only the amount of material needed to keep the B field size well below the saturation point (e.g., less than half of Bs) at each location is used, and preferably a constant level is maintained throughout the layer.

[0056] Figures 6A-6B Alternative views of the variable thickness magnetic layer according to the present specification are shown. First turning to Figure 6AThe magnetic film assembly 300 includes a magnetic film 200 and a magnetic source 240. In some embodiments, the magnetic source 240 may include a coil 260 electrically coupled to a power source 270 (e.g., a coil of a wireless charging system). In some embodiments, the magnetic film 200 includes multiple layers 205a to 205g along the thickness direction (i.e., the z-axis, as shown in the image). Figure 6A (As shown). In some embodiments, each of layers 205a to 205g is composed of one or more magnetic tiles 210, forming one or more stacked magnetic tiles 230 (i.e., a stacked magnetic tile 230 is formed by stacking two or more magnetic tiles 210). In some embodiments, the magnetic tiles 210 are substantially planar. In some embodiments, at least two layers of layers 205a to 205g have different numbers of magnetic tiles arranged on the corresponding layers. For example, layer 205a is shown as containing eight magnetic tiles 210 (as seen in the cross-section), while layer 205e has only four magnetic tiles 210. In other words, in some embodiments, the number of magnetic tiles 210 in each stacked magnetic tile 230 may vary along the thickness direction. In some embodiments, the magnetic tiles may be disposed on a substrate 215 (e.g., a polymer film substrate). In some embodiments, each of layers 205a to 205g may have substantially the same thickness Ta. In some embodiments, the magnetic tiles 210 may have substantially the same thickness Ta. In other words, in some implementations, the thickness Ta of layers 205a to 205g can be defined by the thickness of the magnetic tile 210.

[0057] In some embodiments, the magnetic source 240 may generate an in-plane magnetic field component 225 within the region of interest 220. The region of interest 220 should be defined in air in a region adjacent to the magnetic source 240. In some embodiments, the magnetic field component 225 may have a magnetic field strength (H) that is greater at a first location 226 within the region of interest 220 than at a second location 227 within the region of interest 220. In some embodiments, the magnetic film 200 may be disposed close to or on the magnetic source 240 such that it includes the region of interest 220. In some embodiments, the thickness of the magnetic film 200 at the first location 226 may be greater than the thickness at the second location 227 (e.g., having more vertically stacked magnetic tiles 210). For example, Figure 6A The embodiment shows that the stacked magnetic tile 230 coinciding with position 226 has 6 magnetic tiles 210, and the stacked magnetic tile 230 coinciding with position 227 has only 3 magnetic tiles 210. In some embodiments, the thickness of each stacked magnetic tile 230 may be defined by the magnitude of the corresponding value of H at the position coinciding with each stacked magnetic tile 230.

[0058] Figure 6BAn alternative top view of the magnetic film 200 is shown, which shows the magnetic tiles 210 arranged in a pattern (e.g., a grid-like pattern) on a substrate 215. Figure 6B The magnetic film 200 is shown from a different perspective and is not meant to be limiting in any way. Although the shape of the magnetic film 200 is shown as rectangular with the magnetic tiles 210 arranged in a grid (in a varying thickness stack, not seen in top view) in Figure 6B , any appropriate shape, configuration, or arrangement of the magnetic film 200 and magnetic tiles 210 can be used. For example, in some embodiments, the magnetic film 200 can be circular, elliptical, triangular, or any other shape needed to cover an appropriate portion of a magnetic coil.

[0059] In some embodiments, the magnetic tiles can include, but are not limited to, one or more of the following materials: soft magnetic electrically conductive ferrite, magnetic electrically conductive metal, magnetic electrically conductive crystalline alloy, magnetic electrically conductive nanocrystalline alloy, magnetic electrically conductive amorphous alloy, and magnetic electrically conductive composite.

[0060] In some embodiments, each of the magnetic tiles 210 can be a multi-layer magnetic film. Figure 7 A side view of the magnetic tile 210 as one embodiment of a multi-layer magnetic film in accordance with the present specification is shown. In some embodiments, one or more of the magnetic tiles 210 can include multiple layers. Figure 7 An embodiment of the present specification shows three separate layers 280, 281, and 282 arranged along a thickness direction (e.g., the z-axis as shown in Figure 7 In some embodiments, at least two of these types of layers can be magnetic layers. In some embodiments, only one layer (e.g., layer 280) can be a magnetic layer. In some embodiments, each of the magnetic layers 280 can be disposed on a corresponding non-magnetic substrate 281. In some embodiments, a bonding layer 282 can bond adjacent magnetic layers 280 (in some embodiments including substrate layers 281) to one another.

[0061] Figure 8 A top view of a variable thickness magnetic layer in accordance with the present specification is shown, which shows one possible embodiment of the distribution of magnetic tiles on a magnetic film 200. The magnetic film 200 is represented here as an 8x8 grid / matrix of magnetic tiles, although for discussion purposes, some of the magnetic tiles are shown merged into larger magnetic tiles, as will be described elsewhere herein. The thickness of each magnetic tile or region is printed on the magnetic tile or region in millimeters (mm). For example, the thickness of the four magnetic tiles at the four corners of the square magnetic film 200 is 0.25 millimeters. The thickness of each magnetic tile or region shown in this example is selected based on the value of the B-field corresponding to that magnetic tile or region.

[0062] As Figure 8As shown, the magnetic film 200 can be divided into discrete individual magnetic pieces (i.e., tiles) arranged along the width, length, and thickness directions of the magnetic film 200, or the y-axis, x-axis, and z-axis, respectively. For discussion purposes, the magnetic film 200 is divided into various regions, including a center region 271 (located near the center 275 of the magnetic film 200), a peripheral region 272 (located near the edges of the magnetic film 200), and an intermediate region 273 (disposed between the center region 271 and the peripheral region 272). Figure 8 The magnetic film 200 can be designed to correspond to a solenoid, such as the coil 10 of Figure 1B The center region 271 can correspond to the center of the coil, where there is no conductor, such that the strength of the B-field in this region is relatively low, and thus the thickness of the magnetic tiles in the center region 271 is relatively small compared to the thickness of the magnetic tiles in the intermediate region 273. Figure 8 The intermediate region 273 can correspond to the region above the turns (i.e., conductors) of the coil, where the strength of the B-field is relatively large. In some embodiments, the segments (e.g., tiles) of the magnetic film 200 in the center region 271 can have an average thickness Tcen, the segments in the intermediate region 273 can have an average thickness Tmid, and the segments in the peripheral region 272 can have an average thickness Tper, such that Tmid is greater than Tcen and Tper.

[0063] As previously mentioned, embodiments of the magnetic film 200 as shown in Figure 8 may be formed as an 8x8 grid or matrix of tiles. The shape and size of the film 200, the number, configuration, and arrangement of the tiles, and the relative dimensions of the tiles can vary, and the embodiments shown here are for illustrative purposes only. In some embodiments, at least two of the tiles forming the magnetic film 200, such as tiles 283 and 284, can have different shapes, rather than a grid of tiles of the same size. In some embodiments, at least two of the tiles, such as tiles 284 and 285, can have the same shape (e.g., rectangular), but different relative dimensions.

[0064] Figure 9 A side cross-sectional view of a system for wireless power transfer according to the present specification is shown. In some embodiments, the wireless power transfer system 700 can include a power receiving assembly 600 (e.g., a mobile device) and a power transmitting assembly 500 (e.g., a wireless charging station for the mobile device). In some embodiments, the power receiving assembly 600 includes a first magnetic film 610 disposed between a first metal plate 620 and a power receiving antenna 630. In some embodiments, the power receiving antenna 630 can be a coil including a conductive wire wound into turns. Figure 9The depiction of the power receiving antenna 630 shows the cross-sectional profile of several turns of the coil. In some embodiments, the power transmitting assembly 500 includes a second magnetic film 710 disposed between the second metal plate 720 and the power transmitting antenna 730. The power receiving antenna 630 and the power transmitting antenna 730 are substantially aligned with each other. When the power transmitting antenna 730 is energized (e.g., current passes through the turns of the coil), the power transmitting antenna 730 wirelessly transmits power to the power receiving antenna.

[0065] In some embodiments, at least one of the first and second magnetic films can include a plurality of stacked magnetic tiles 611, 711 arranged along a width (e.g., x-axis as shown Figure 9 In some embodiments, each of the stacked magnetic tiles can include a plurality of magnetic tiles 612, 712 stacked along a thickness direction of the magnetic film (e.g., z-axis as shown Figure 9 In some embodiments, at least two of the stacked magnetic tiles, e.g., 713, 714 (or 613, 614) have different numbers of magnetic tiles (i.e., resulting in each of the stacked magnetic tiles 713, 714 or 613, 614 having a different thickness along the z-axis).

[0066] In some embodiments of the magnetic film, the magnetic film can have a constant overall thickness, but achieve a substantially uniform B-field by including tiles of different magnetic materials having different relative permeability on the film. Figure 10 A side cross-sectional view of one such embodiment of a magnetic film according to the present specification is shown. The magnetic film assembly 800 can include a magnetic film 810 disposed proximate to a coil 830. The magnetic film 810 can have a thickness Tl that is substantially constant across the magnetic film 810, or that varies by less than about 20%, or less than about 10%, or less than about 5% across the magnetic film.

[0067] In some embodiments, the magnetic film 810 can include a plurality of magnetic tiles 811 arranged along a first in-plane direction (e.g., x-axis as shown Figure 10 In some embodiments, the magnetic film 810 can include a plurality of magnetic tiles 811 arranged along a first in-plane direction (e.g., x-axis as shown

[0068] In some embodiments, when the coil 830 is energized (e.g., current passes through the turns of the coil), a magnetic field is generated that, in turn, induces a planar magnetic flux density B 821 within the magnetic film 810. In some embodiments, the different magnetic materials used in the magnetic tiles 811 can cause the magnetic flux density 821 to be about 1.2 times, or about 1.0 times, or about 0.8 times, or about 0.4 times less than the magnetic saturation level Bs of the magnetic film 810.

[0069] Many of the example embodiments discussed herein describe a varying thickness magnetic layer or film produced by stacking smaller magnetic tiles, where each magnetic tile has substantially the same relative dimensions. The varying thickness of the magnetic film is achieved by varying the number of magnetic tiles used in each “stacked tile.” In some embodiments, it can be desirable to use magnetic sections that inherently have different thicknesses, without the need to stack multiple magnetic tiles, to form a variable thickness magnetic layer. Figure 11A A side cross-sectional view of one such embodiment of a magnetic film is shown. The magnetic film 900a includes a plurality of discrete magnetic sections 910 arranged along the length (e.g., the x-axis as shown) and width (e.g., the y-axis) of the magnetic film 900a. In some embodiments, each magnetic section 910 can have substantially similar composition, but can have different thicknesses. For example, the thickness of sections 910a, 910b are significantly different. Figure 11A

[0070] In some embodiments, it can be desirable to use magnetic sections that have substantially the same thickness, but have different materials and / or have different magnetic permeability. Figure 11B A side cross-sectional view of one such embodiment of a magnetic film is shown. The magnetic film 900b includes a plurality of discrete magnetic sections 915 arranged along the length (e.g., the x-axis as shown) and width (e.g., the y-axis) of the magnetic film 900b. In some embodiments, each magnetic section 915 can have substantially the same thickness (e.g., in the z-direction as shown), but can have different materials, or otherwise exhibit different magnetic permeability values. For example, the thickness of sections 915a, 915b are substantially the same, but each section can have different materials and / or have different magnetic permeability. Figure 11B Figure 11B Figure 11A and Figure 11B These are merely example embodiments, and other configurations and / or material combinations can be used. For example, in some embodiments, a magnetic film can exhibit both a variable thickness and a variable magnetic permeability on its surface.

[0071] Finally, Figures 12A-12B Graphs of magnetic field strength and magnetic flux density for a magnetic film assembly according to the present specification are shown. It can be useful to examine these graphs concurrently with the following description. Figure 12A ​​​A graph showing the magnetic field 1010 produced by a substantially planar coil 1000 when energized and without a magnetic film disposed near the coil is shown. The arrows shown in the graph represent the magnitude of the magnetic field strength H by their relative size (larger arrows represent larger H values) and the direction of the magnetic field (i.e., the direction the arrow points represents the direction of the magnetic field lines). If the hypothetical line of interest 1020 projected on the field 1010 is examined, it can be seen that the magnetic field is substantially oriented along the line of interest 1020 at each of the first and second endpoints 1030, 1040, and substantially orthogonal to the line of interest at the midpoint 1050. Further, it can also be seen that the magnitude of the magnetic field 1010 in the plane is largest in the region corresponding to the conductors (i.e., turns) of the coil 1000, and relatively smaller outside the outer edge of the coil 1000.

[0072] Figure 12B A graph showing the magnetic flux density B 1060 produced by the coil 1000 when a magnetic film is disposed on the coil so as to be substantially parallel to the coil and including the line of interest 1020 is shown. When the coil 1000 is energized, the magnetic flux density 1060 is substantially oriented along the line of interest at least at the first endpoint 1030, the second endpoint 1040, and the midpoint 1050. The magnitude of the magnetic flux density 1060 near the line of interest is also relatively uniform.

[0073] Terms such as“about” will be understood by those of ordinary skill in the art in the context in which they are used and described in this specification. If the use of“about” to express the magnitude of a quantity, number, and physical property is unclear to those of ordinary skill in the art in the context in which it is used and described in this specification, then“about” will be understood to mean within 10% of the specified value. A quantity given as about a specified value can be exactly the specified value. For example, if it is unclear to those of ordinary skill in the art in the context in which it is used and described in this specification, a quantity having a value of about 1 means that the quantity has a value between 0.9 and 1.1, and the value can be 1.

[0074] The term such as“substantially” will be understood by those of ordinary skill in the art in the context in which it is used and described in this specification. If the use of“substantially equal” is unclear to those of ordinary skill in the art in the context in which it is used and described in this specification, then“substantially equal” will mean about as approximately as noted above. If the use of“substantially parallel” is unclear to those of ordinary skill in the art in the context in which it is used and described in this specification, then“substantially parallel” will mean within 30 degrees of parallel. In some embodiments, directions or surfaces described as being substantially parallel to each other can be within 20 degrees or within 10 degrees of parallel, or can be parallel or nominally parallel. If the use of“substantially aligned” is unclear to those of ordinary skill in the art in the context in which it is used and described in this specification, then“substantially aligned” will mean aligned within 20% of the width of the aligned object. In some embodiments, objects described as being substantially aligned can be aligned within 10% or within 5% of the width of the aligned object.

[0075] All cited references, patents and patent applications in the above application for patent, in one form or another, are hereby incorporated by reference in their entirety. In the event that one or more of the incorporated literature references, patents or patent applications contradicts with the preceding description, including definition of terms, the preceding description, including definition of terms, controls.

[0076] Unless otherwise indicated, description of elements in the figures is to be understood as applying to corresponding elements in other figures, where applicable. While specific embodiments have been illustrated and described, it will be appreciated that various alternate and / or equivalent modifications can be made of the embodiments described without deviating from the scope of the disclosure. This application is intended to cover any adaptations or variations of the specific embodiments discussed. Therefore, it is intended that the disclosure be protected by the following claims and their equivalents.

Claims

1. A magnetic film assembly, the magnetic film assembly comprising: A coil comprising multiple turns that define a first principal boundary surface of the coil, such that when energized, the coil generates an in-plane magnetic field component in a region of interest in air that is close to and substantially parallel to the first principal boundary surface, the in-plane magnetic field component having a magnetic field strength H varying between a maximum value Hmax and 10% of the maximum value Hmax in the region of interest in air; as well as A magnetic layer is disposed on the coil to include the region of interest, such that when energized, the coil generates a magnetic field that induces an in-plane magnetic flux density B in the magnetic layer within the region of interest, the variation of the in-plane magnetic flux density within the region of interest being less than 5%. The magnetic layer has regions of varying thickness, wherein the local thickness of each region of varying thickness is determined by the magnetic field strength generated near the corresponding position on the coil.

2. The magnetic film assembly of claim 1, wherein the coil is substantially planar, the first primary boundary surface is substantially planar, and wherein the coil defines a substantially planar second primary boundary surface of the coil, the second primary boundary surface being opposite to and substantially parallel to the first primary boundary surface.

3. The magnetic film assembly of claim 1, wherein the coil is substantially a helical coil, the first primary boundary surface is a substantially cylindrical outer surface, and wherein the coil defines a substantially cylindrical primary inner boundary surface of the coil, the primary inner boundary surface being opposite to and substantially concentric with the first primary boundary surface.

4. The magnetic film assembly of claim 1, wherein, in a plan view, the magnetic layer substantially completely covers the coil.

5. The magnetic film assembly of claim 1, wherein, in a plan view, the magnetic layer covers only a portion of the coil.

6. A magnetic film assembly, the magnetic film assembly comprising: A coil, the coil comprising conductive wire wound to form a plurality of substantially concentric loops; as well as A magnetic layer is disposed on the coil and has a non-uniform thickness and a saturation magnetic flux density Bs, such that when energized, the coil generates a magnetic field, which induces an in-plane magnetic flux density B in the magnetic layer. The non-uniformity in the thickness of the magnetic film results in the in-plane magnetic flux density B in the region of interest of the magnetic layer being less than 1.1 saturation magnetic flux density Bs. The magnetic layer has regions of varying thickness, wherein the local thickness of each region of varying thickness is determined by the magnetic field strength generated near the corresponding position on the coil.

7. The magnetic film assembly of claim 6, wherein the coil has a thickness Tc and the conductive wire has a thickness Tw, and the ratio of thickness Tc to thickness Tw is less than 1.

5.

8. The magnetic film assembly of claim 6, wherein the coil has a thickness Tc and the conductive wire has a thickness Tw, wherein the ratio of thickness Tc to thickness Tw is greater than 2.

9. The magnetic film assembly of claim 6, wherein the conductive wire is non-insulated.

10. The magnetic film assembly of claim 6, wherein the conductive wire is insulated and includes a conductive core surrounded by an insulating layer.

11. The magnetic film assembly of claim 6, wherein the conductive wire is a binding wire, the binding wire comprising an insulating layer surrounding a plurality of conductive chains.

12. The magnetic film assembly of claim 6, wherein the non-uniformity of the thickness of the magnetic film results in a magnetic flux density B in the plane of the region of interest of the magnetic layer being less than 0.8 saturation magnetic flux density Bs.

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