TECHNICAL FIELD

[0001] The present invention generally relates to wireless power transfer based on magnetic induction, and more particularly, a multilayer coupler for wireless power transfer and a method of manufacturing thereof, a wireless power transmitter including the multilayer coupler, a wireless power receiver including the multilayer coupler, a system for wireless power transfer including the wireless power transmitter and/or the wireless power receiver, and a method of wireless power transfer using the multilayer coupler.

BACKGROUND

[0002] Wireless power transfer (WPT) based on magnetic induction (which may also be referred to as inductive power transfer (IPT)) has been widely used in charging or powering numerous applications, such as electronic devices, medical implantable devices, automatic guided vehicles, robots, and electric transportations and so on, where safety and/or convenience are concerned. For example, in a WPT system for charging applications, coils may be provided that serve as couplers (i.e., magnetic couplers) that make the charging pads for both transmitter (Tx) and receiver (Rx). Electrical power can be transferred wirelessly through the magnetic coupling between transmitter and receiver coils in a similar working principle as a transformer. Furthermore, the physical separation between transmitter and receiver coils provides electrical isolation and avoids mechanical wear and tear found in contact charger.

[0003] The design/configuration of magnetic couplers is an important aspect of a WPT system. For example, the main purpose of magnetic couplers is power transfer through magnetic induction, which affects the performance of the WPT system, such as efficiency, air gap and misalignment between transmitter and receiver, voltage gain, and electromagnetic (EM) noise emission. For example, high EM noise emission may interfere with other electronic devices nearby. However, in conventional designs/configurations disclosed for magnetic couplers (i.e., the coils), the EM noise emission aspect has often been overlooked, but which may be a key factor in realizing the designs/configurations in commercial products or devices. For example, for a product to be sold, it may be necessary for the product to satisfy a maximum limit of conducted and radiated EM noise emission as defined by international and regional standards. This may also be applicable to various applications that utilize alternating current (AC) in coil(s), such as induction heating and induction cooker, for example, since power is nevertheless transferred wirelessly from the induction heating element to a heated object.

[0004] A need therefore exists to provide a coupler (i.e., a magnetic coupler) for wireless power transfer, that seek to overcome, or at least ameliorate, one or more of the deficiencies in conventional couplers for wireless power transfer, such as but not limited to, reducing or minimizing EM noise emission. It is against this background that the present invention has been developed.

SUMMARY

[0005] According to a first aspect of the present invention, there is provided a multilayer coupler for wireless power transfer, the multilayer coupler comprising: a coil configured for wireless power transfer based on magnetic induction and has a multilayer winding structure, the multilayer winding structure comprising a plurality of winding layers, each of the plurality of winding layers comprising a plurality of winding turns, wherein for each of the plurality of winding layers, at least each of a plurality of intermediate winding turns of the plurality of winding turns of the winding layer comprises one or more transition portions at which a corresponding coil transition of the coil occurs between the intermediate winding turn of the winding layer and a winding turn of another winding layer of the plurality of winding layers.

[0006] According to a second aspect of the present invention, there is provided a wireless power transmitter comprising: a power source configured to generate a time-varying current; and a multilayer coupler according to the above-mentioned first aspect of the present invention functioning as a transmitter coupler and connected to the power source, wherein the transmitter coupler is configured to receive the time-varying current from the power source for generating a magnetic field to perform wireless power transfer with a receiver coupler over an air gap based on magnetic induction.

[0007] According to a third aspect of the present invention, there is provided a wireless power receiver comprising: an electrical load; and a multilayer coupler according to the above-mentioned first aspect of the present invention functioning as a receiver coupler and connected to the electrical load, wherein the receiver coupler is configured to couple with a magnetic field generated from a transmitter coupler to induce a current in the receiver coupler for supplying power to the electrical load connected to the receiver coupler to perform wireless power transfer with the transmitter coupler over an air gap based on magnetic induction.

[0008] According to a fourth aspect of the present invention, there is provided a system for wireless power transfer comprising: a wireless power transmitter comprising: a power source configured to generate a time-varying current; and a transmitter coupler connected to the power source, wherein the transmitter coupler is configured to receive the time-varying current from the power source for generating a magnetic field to perform wireless power transfer with a receiver coupler over an air gap based on magnetic induction; and a wireless power receiver comprising: an electrical load; and the receiver coupler connected to the electrical load, wherein the receiver coupler is configured to couple with the magnetic field generated from the transmitter coupler to induce a current in the receiver coupler for supplying power to the electrical load connected to the receiver coupler to perform wireless power transfer with the transmitter coupler over the air gap based on magnetic induction, wherein at least one of the receiver coupler and the transmitter coupler is a multilayer coupler according to the above-mentioned first aspect of the present invention, and the wireless power transmitter and the wireless power receiver are separated by the air gap.

[0009] According to a fifth aspect of the present invention, there is provided a method of manufacturing a multilayer coupler for wireless power transfer, the method comprising: configuring a coil for wireless power transfer based on magnetic induction, the coil having a multilayer winding structure, the multilayer winding structure comprising a plurality of winding layers, each of the plurality of winding layers comprising a plurality of winding turns, wherein for each of the plurality of winding layers, at least each of a plurality of intermediate winding turns of the plurality of winding turns of the winding layer comprises one or more transition portions at which a corresponding coil transition of the coil occurs between the intermediate winding turn of the winding layer and a winding turn of another winding layer of the plurality of winding layers. [0010] According to a sixth aspect of the present invention, there is provided a method of wireless power transfer comprising: generating, by a power source at a wireless power transmitter, a time-varying current; and receiving, by a transmitter coupler at the wireless power transmitter connected to the power source, the time-varying current from the power source for generating a magnetic field to perform wireless power transfer with a receiver coupler over an air gap based on magnetic induction; coupling, by the receiver coupler at a wireless power receiver connected to an electrical load, with a magnetic field generated from the transmitter coupler to induce a current in the receiver coupler to perform wireless power transfer with the transmitter coupler over the air gap based on magnetic induction; and supplying, by the receiver coupler at the wireless power receiver, power to the electrical load connected thereto based on the current induced therein, wherein at least one of the receiver coupler and the transmitter coupler is a multilayer coupler according to according to the above-mentioned first aspect of the present invention, and the wireless power transmitter and the wireless power receiver are separated by the air gap.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Embodiments of the present invention will be better understood and readily apparent to one of ordinary skill in the art from the following written description, by way of example only, and in conjunction with the drawings, in which:

FIGs. 1 A to IF depict schematic drawings of example conventional couplers having various example configurations/shapes;

FIG. 2A depicts a perspective view of an example conventional coupler having a singlelayer winding;

FIG. 2B depicts a perspective view of an example conventional coupler having a multilayer winding;

FIG. 3 depicts a schematic drawing showing an example conventional multilayer coupler formed by stacking a number of single-layer couplers together into two layers;

FIG. 4 depicts a perspective view of an example conventional two-layer coupler, along with a schematic cross-sectional view of a section thereof; FIG. 5 depicts a simplified schematic drawing of an example conventional rectangular two-layer coupler with the coil being configured or wound according to the first conventional winding strategy;

FIGs. 6A and 6B depict schematic drawings of coils configured or wound according to the first conventional winding strategy, namely, an example conventional coil (FIG. 6A) having aligned winding layers and an example conventional coil (FIG. 6B) having non-aligned winding layers;

FIG. 7 depicts an example conventional double-layer coupler having a coil configured according to the first conventional winding strategy and with two wires bundled together per winding turn;

FIGs. 8A and 8B depict schematic drawings of a perspective view (FIG. 8A) and a top view (FIG. 8B) of an example conventional four-layer PCB coil configured according to the first conventional winding strategy;

FIG. 9 depicts a schematic cross-sectional view of a section of a second example conventional multilayer coupler configured according to a second conventional winding strategy or winding sequence;

FIG. 10 depicts a simplified schematic drawing of a conventional rectangular two-layer coupler with the coil being wound according to the second conventional winding strategy;

FIG. 11A depicts a conventional five-layer coupler comprising a coil configured according to the second conventional winding strategy;

FIG. 11B depicts a conventional four-layer coupler comprising a coil configured according to the second conventional winding strategy;

FIGs. 12A and 12B depict schematic drawings of a multilayer coupler for wireless power transfer, according to various embodiments of the present invention;

FIG. 13 depicts a schematic drawing of a system for wireless power transfer according to various embodiments of the present invention;

FIG. 14 depicts a schematic flow diagram of a method of wireless power transfer, according to various embodiments of the present invention;

FIG. 15 depicts a schematic flow diagram of a method of manufacturing a multilayer coupler for wireless power transfer according to various embodiments of the present invention;

FIG. 16 depicts a schematic cross-sectional view of a section of a first example multilayer coupler according to various example embodiments of the present invention, along with an associated first winding sequence (based on winding turns or loops) for forming the multilayer winding structure of the coil thereof illustrated or denoted by arrows;

FIGs. 17A to 17C depict simplified schematic drawings of example rectangular multilayer couplers, each comprising a coil configured to have a multilayer winding structure according to the first winding sequence, according to various example embodiments of the present invention;

FIG. 18 depicts a schematic cross-sectional view of a section of various example multilayer couplers according to various example embodiments of the present invention, along with the associated winding sequence for forming the multilayer winding structure of the coil thereof illustrated or denoted by arrows;

FIG. 19 depicts a schematic cross-sectional view of a section of a second example multilayer coupler according to various example embodiments of the present invention, along with an associated second winding sequence for forming the multilayer winding structure of the coil thereof illustrated or denoted by the arrows;

FIGs. 20A to 20C depict simplified schematic drawings of rectangular multilayer couplers, each comprising a coil configured to have a multilayer winding structure according to the second winding sequence, according to various example embodiments of the present invention;

FIG. 21 depicts a schematic cross-sectional view of a section of various example multilayer couplers according to various example embodiments of the present invention, along with the associated winding sequence for forming the multilayer winding structure of the coil thereof illustrated or denoted by arrows;

FIG. 22 depicts a schematic cross-sectional view of a section of a third example multilayer coupler according to various example embodiments of the present invention, along with an associated third winding sequence for forming the multilayer winding structure of the coil thereof illustrated or denoted by the arrows;

FIGs. 23A and 23B depict simplified schematic drawings of rectangular multilayer couplers, each comprising a coil configured to have a multilayer winding structure according to the second winding sequence, according to various example embodiments of the present invention, whereby a plurality of transition portions are provided per winding turn;

FIG. 24 depicts schematic drawings of example conventional multilayer couplers configured according to the first and second conventional winding sequences, respectively, whereby winding turns in each winding layer are connected in a series configuration; FIG. 25 depicts a schematic drawing of a perspective view of an example conventional multilayer coupler configured according to the first conventional winding sequence, along with the formation of parasitic capacitances among coils of adjacent winding layers shown;

FIG. 26A depicts a simplified schematic drawing of a rectangular multilayer coupler comprising three coil cells stacked to form additional coil cell layers and are connected independently, according to various example embodiments of the present invention;

FIG. 26B depicts a schematic drawing of a simplified rectangular multilayer coupler comprising three coil cells stacked to form additional coil cell layers and are connected in series, according to various example embodiments of the present invention;

FIG. 26C depicts a schematic drawing of a simplified rectangular multilayer coupler comprising three coil cells stacked to form additional coil cell layers and are connected in parallel, according to various example embodiments of the present invention; and

FIGs. 27A and 27B show the alternating current measurements (AC current waveform) in the multilayer coupler configured according to the second winding sequence according to various example embodiments and a conventional multilayer coupler configured the first conventional winding sequence, respectively.

DETAILED DESCRIPTION

[0012] Various embodiments of the present invention generally relates to wireless power transfer (WPT) based on magnetic induction (which may also be referred to as inductive power transfer (IPT)). In particular, various embodiments of the present invention provide a multilayer coupler for wireless power transfer (which may also be referred to as a wireless power transfer multilayer coupler (i.e., magnetic multilayer coupler)) and a method of manufacturing thereof. Various embodiments of the present invention also provide a wireless power transmitter including the above-mentioned multilayer coupler (which may be referred to as a multilayer transmitter coupler), and a wireless power receiver including the above-mentioned multilayer coupler (which may be referred to as a multilayer receiver coupler). Various embodiments of the present invention further provide a system for wireless power transfer including the above- mentioned wireless power transmitter and/or the wireless power receiver, and a method of wireless power transfer using the above-mentioned multilayer coupler.

[0013] There are various design aspects of couplers (e.g., which may be coil(s) or may include coil(s)) for various purposes and applications. For example, couplers may be made of round wire, flat wire, magnet wire bunch, printed circuit board (PCB) traces, or various combinations thereof, as appropriate. Furthermore, the coil may be configured to have various shapes/configurations, such as but not limited to, a spiral shape, a round or circular shape 100 (e.g., as shown in FIG. 1 A), a rectangular shape 102 (e.g., as shown in FIG. IB), a triangular shape 104 (e.g., as shown in FIG. 1C), an elliptical shape 106 (e.g., as shown in FIG. ID), a polygonal shape (e.g., a hexagonal shape 108 as shown in FIG. IE or a pentagonal shape 110 as shown in FIG. IF), or any other shapes as appropriate.

[0014] Furthermore, couplers may also be designed or configured to have a single-layer winding structure (which may simply be referred to as a single-layer winding) or a multilayer winding structure (which may simply be referred to as a multilayer winding). For example, a coupler having a single-layer winding structure may be referred to as a single-layer coupler, and a coupler having a multilayer winding structure may be referred to as a multilayer coupler. For example, a multilayer winding may be used for various compact applications since a higher inductance can be achieved given the same area. By way of an example only for illustration purpose, FIG. 2A depicts a perspective view of an example conventional coupler 200 having a single-layer winding and FIG. 2B depicts a perspective view of an example conventional coupler 210 having a multilayer winding (or more specifically, a two-layer winding).

[0015] Conventionally, a few (or more) single-layer couplers may also be stacked to form a multilayer coupler, which serve as multiple receivers with possible multiple frequencies operations. By way of an example only for illustration purpose, FIG. 3 depicts a schematic drawing showing an example conventional multilayer coupler 300 formed by stacking a number of single-layer couplers together into two layers.

[0016] Various embodiments of the present invention note that the design or configuration of a multilayer winding impacts the parasitic impedance in the couplers and the EM noise emission generated. Conventionally, regardless of the coil shapes and wire materials, there are few winding strategies (which may also be referred to herein as winding techniques) for a multilayer winding. In this regard, for illustration purpose, two example conventional multilayer winding strategies will now be described below.

[0017] FIG. 4 depicts a perspective view of a first example conventional two-layer coupler 400, along with a schematic cross-sectional view of a section thereof. In the winding strategy associated with the first example conventional multilayer coupler 400, as illustrated in FIG. 4, the coil is wound (in winding turns or loops) from one side or end (e.g., a first side or end, such as corresponding to an innermost or outermost winding turn with respect to a center or core of the first example conventional multilayer coupler 400) to another side or end (e.g., a second side or end, such as corresponding to the outermost or innermost winding turn (opposite to the first side or end) with respect to the center) in a winding layer (e.g., layer 1), then continue in the same manner but in an opposite winding direction (i.e., from the second side or end to the first side or end) in the next or subsequent winding layer (e.g., layer 2), and so on. In particular, in FIG. 4, the winding sequence (based on winding turns or loops) according to the winding strategy associated with the first example conventional multilayer coupler 400 is illustrated or denoted by arrows 410. In this regard, such a conventional winding strategy or winding sequence may be referred to herein as the first conventional winding strategy or winding sequence.

[0018] By way of an example only for illustration purpose, FIG. 5 depicts a simplified schematic drawing of an example conventional rectangular two-layer coupler 500 (i.e., having two winding layers) with the coil being configured or wound according to the first conventional winding strategy. In the simplified schematic representation shown in FIG. 5, the winding turns represented by a full line corresponds to a first layer of the coil, while the winding turns represented by a dashed line corresponds to a second layer of the coil. As shown in FIG. 5 for illustration purpose and without limitation, each winding layer may comprise four winding turns. For simplicity and ease of comparison, the same or similar type of simplified schematic representation (i.e., the simplified schematic rectangular representation) may be utilized to illustrate or represent various configurations/designs of multilayer couplers described herein. It will be understood by a person skilled in the art that the present invention is not limited to coils having a rectangular shape and may have any other shapes as appropriate. Furthermore, in such simplified schematic representations, it will be appreciated by a person skilled in the art that winding turns at different layers but at the same turn position may be shown closely adjacent each other for illustration purpose only, but such winding turns at different winding layers may actually be directly over each other with respect to an axial direction (e.g., a vertical axis).

[0019] FIGs. 6A and 6B depict schematic drawings of coils 604, 608 configured or wound according to the first conventional winding strategy, whereby the coil 604 has aligned winding layers and the coil 608 has non-aligned winding layers (or shifted winding layers). In FIG. 6B, it is shown that the position of a winding layer may be shifted (e.g., in a lateral direction, which may also be referred to as a transverse direction, such as a radial direction in the case the coil is configured to have a circular shape) with respect to another winding layer of the coil 608. In FIGs. 6A and 6B, it is also shown that the coils 604, 608 are not limited to having two winding layers and may have any number of winding layers as desired or as appropriate. [0020] For example, the first conventional winding strategy can be found in commercial double-layer couplers, such as shown in FIGs. 4 and 7. In particular, the double-layer coupler 400 shown in FIG. 4 comprises a coil configured according to the first conventional winding strategy with one wire per winding turn, and the double-layer coupler 400 shown in FIG. 7 comprises a coil configured according to the according to the first conventional winding strategy with two wires bundled together per winding turn.

[0021] The first conventional winding strategy has also been found in existing conventional four-layer printed circuit board (PCB) coil. By way of an example for illustration purpose, FIGs. 8A and 8B depict schematic drawings of a perspective view (FIG. 8A) and a top view (FIG. 8B) of the conventional four-layer PCB coil 800 configured according to the first conventional winding strategy.

[0022] FIG. 9 depicts a schematic cross-sectional view of a section of a second example conventional multilayer coupler 900 configured according to a second conventional winding strategy or winding sequence. In the second conventional winding strategy associated with the second example conventional multilayer coupler 900, as illustrated in FIG. 9, the coil is configured or wound (in winding turns or loops) from one side or end (e.g., a first side or end, such as corresponding to an innermost or outermost winding turn with respect to a center or core of the second example conventional multilayer coupler 900) to another side or end (e.g., a second side or end, such as corresponding to the outermost or innermost winding turn (opposite to the first side or end) with respect to the center) in a winding layer (e.g., layer 1), then continue in the same manner and in the same winding direction (i.e., from the first side or end to the second side or end) in the next or subsequent winding layer (e.g., layer 2), and so on. In particular, in FIG. 9, the winding sequence (based on winding turns or loops) according to the second winding strategy is illustrated or denoted by arrows 910. In this regard, such a conventional winding strategy or winding sequence may be referred to herein as the second conventional winding strategy or winding sequence.

[0023] By way of an example only for illustration purpose, FIG. 10 depicts a simplified schematic drawing of a conventional rectangular two-layer coupler 1000 (i.e., having two winding layers) with the coil being wound also according to the second conventional winding strategy. As shown in FIG. 10 for illustration purpose and without limitation, each winding layer may comprise four winding turns.

[0024] For example, the second conventional winding strategy can be found in conventional double-layer couplers, such as shown in FIGs. 11A and 11B. In particular, FIG. 11 A depicts a conventional five-layer coupler 1104 comprising a coil configured according to the second conventional winding strategy and FIG. 11B depicts a conventional four-layer coupler 1108 comprising a coil configured according to the second conventional winding strategy.

[0025] However, various embodiments of the present invention note that conventional multilayer couplers configured based on conventional winding strategies (or winding techniques), such as the above-mentioned first or second conventional winding strategies, result in high parasitic capacitance in the coil. Without wishing to be bound by theory, but various embodiments of the present invention found that such conventional winding strategies create multiple low impedance pass at different frequencies, which undesirably increases EM noise emission profile.

[0026] Accordingly, various embodiments of the present invention found that conventional multilayer couplers may undesirably suffer from a high EM noise emission. Therefore, various embodiments provide a multilayer coupler (i.e., a magnetic multilayer coupler) for wireless power transfer, that seeks to overcome, or at least ameliorate, one or more of the deficiencies in conventional multilayer couplers for wireless power transfer, such as but not limited to, reducing or minimizing EM noise emission.

[0027] FIG. 12A depicts a schematic drawing of a multilayer coupler 1200 for wireless power transfer, according to various embodiments of the present invention. The multilayer coupler 1200 comprises a coil 1204 configured for wireless power transfer based on magnetic induction and has a multilayer winding structure, the multilayer winding structure comprising a plurality of winding layers 1208, each of the plurality of winding layers 1208 comprising a plurality of winding turns 1212. In particular, for each of the plurality of winding layers 1208, at least each of a plurality of intermediate winding turns of the plurality of winding turns 1212 of the winding layer comprises one or more transition portions 1216 at which a corresponding coil transition of the coil occurs between the intermediate winding turn of the winding layer and a winding turn of another winding layer of the plurality of winding layers 1208. Such a coil transition between a winding turn of a winding layer and a winding turn of another winding layer may also be referred to herein as an interlayer coil transition (or simply interlayer transition).

[0028] The term “winding turn” (which may also simply be referred to as a “turn”) in the context of couplers for wireless power transfer is known to a person skilled in the art and thus need not be described or defined herein. For example, it can be understood that a winding turn corresponds to a portion or section of the coil being wound about a center or a core (e.g., an air core) one time, and each winding turn is for example represented in FIG. 12A as one circle. It will be appreciated by a person skilled in the art that a winding turn may be completely wound about, or at least substantially wound about, a center or a core, especially intermediate winding turns. For example, it will be appreciated by a person skilled in the art that one or more winding turns may not be completely wound about a center or a core due to practical implementation factors, such as the winding turn directly coupled to or leading to an input (or an input portion) or output (or an output portion) of the coil.

[0029] It will be appreciated by a person skilled in the art that FIG. 12A illustrates the presence of a coil 1204 having a multilayer winding structure comprising a plurality of winding layers 1208, each winding layer comprising a plurality of winding turns 1212, but does not actually illustrate or define various details or parameters (e.g., shape, dimensions/size, and so on) of the coil 1204. In other words, it will be appreciated by a person skilled in the art that the coil 1204 is not limited to the shapes and/or dimensions/ sizes as shown in FIG. 12A in any way. It will also be appreciated by a person skilled in the art that, although not explicitly shown in FIG. 12 A, the plurality of winding turns 1212 of the plurality of winding layers 1208 are electrically connected, for example, since they may be integrally formed by winding the coil 1204 to form one continuous winding.

[0030] In various embodiments, an intermediate winding turn of a winding layer refers to a winding turn of the winding layer that is between the innermost winding turn and the outermost winding turn of the winding layer. Accordingly, the above-mentioned plurality of intermediate winding turns of the winding layer refer to any multiple (two or more) winding turns that are between the innermost winding turn and the outermost winding turn of the winding layer.

[0031] In various embodiments, the above-mentioned plurality of intermediate winding turns may correspond to all intermediate winding turns of the plurality of winding turns or a subset thereof (i.e., not all intermediate winding turns). For example, the above-mentioned plurality of intermediate winding turns comprising the above-mentioned one or more transition portions 1216 (i.e., at which interlayer coil transition occurs) may be located along the winding layer based on a predetermined pattern, such as periodically located. For example, upon the coil transitioning to a winding turn (e.g., at turn position 1) at a winding layer from another winding layer, the next intermediate winding turn at the winding layer at which interlayer coil transition occurs may be located two or more turn positions (e.g., at turn position 3 or 4) away from the winding turn. Accordingly, the predetermined pattern may be a predetermined number of turn position away. For example, the predetermined pattern may be the same amongst the plurality of winding layers. In other examples, the predetermined pattern may be the different amongst the plurality of winding layers.

[0032] In various embodiments, the coil 1204 may be made of round wire, flat wire, magnet wire bunch, printed circuit board (PCB) traces, or various combinations thereof, as desired or as appropriate. Furthermore, the coil may be made of a single wire or a wire bundle comprising a plurality of wires bundled together (e.g., in a parallel or twisted manner), such as a bundle of insulated wires twisted together as in the case for high frequency wires (e.g., Litz wires).

[0033] Accordingly, the coil 1204 is configured to have a multilayer winding structure whereby, for each of the plurality of winding layers, at least each of a plurality of intermediate winding turns of the plurality of winding turns of the winding layer comprising one or more transition portions at which a corresponding coil transition (interlayer coil transition) of the coil occurs between the intermediate winding turn and a winding turn of another winding layer of the plurality of winding layers. As a result, at least multiple winding turns of the plurality of winding turns of the winding layers that are between the innermost winding turn and the outermost winding turn of the winding layer comprise one or more of the above-mentioned transition portions, which has been found to advantageously reduce or minimize the effective parasitic capacitance (or optimize impedance) in the multilayer coupler 1200, thereby reducing or minimizing EM noise emission by the multilayer coupler 1200. In particular, without wishing to be bound by theory, but various embodiments of the present invention found that by configuring, for each of the plurality of winding layers, at least each of the above-mentioned plurality of intermediate winding turns of the winding layer to have one or more of the above- mentioned transition portions, parasitic capacitance in the multilayer coupler 1200 is advantageously distributed (e.g., across the plurality of winding layers and the plurality of winding turns), thereby reducing or minimizing the effective parasitic capacitance (or optimize impedance) in the multilayer coupler 1200. These advantages or technical effects will become more apparent to a person skilled in the art as the multilayer coupler 1200 is described in more details according to various embodiments and example embodiments of the present invention. [0034] In various embodiments, for the above-mentioned each of the plurality of winding layers, each of the plurality of winding turns of the winding layer comprises one or more transition portions at which a corresponding coil transition of the coil occurs between the winding turn of the winding layer and a winding turn of another winding layer of the plurality of winding layers. That is, for each of the plurality of winding layers 1208, each of the plurality of winding turns 1212 of the winding layer, including the above-mentioned plurality of intermediate winding turns, comprises the above-mentioned one or more transition portions. For example, the plurality of winding turns 1212 may include the outermost (or first) winding turn, the above-mentioned plurality of intermediate winding turns and the innermost (or last) winding turn. As another example, the plurality of winding turns 1212 may be all winding turns of the winding layer.

[0035] In various embodiments, for the above-mentioned each of the plurality of winding layers and for the above-mentioned each of the plurality of intermediate winding turns of the winding layer, the intermediate winding turn of the winding layer and the winding turn of the above-mentioned another winding layer between which the corresponding coil transition of the coil occurs are winding turns at a same turn position (e.g., with respect to the respective winding layer). In other words, the corresponding coil transition is between winding turns at the same turn position, such as illustrated in FIG. 16 to be described later below according to various example embodiments of the present invention. In various embodiments, the turn position of a winding turn of a winding layer refers to the position of the winding turn in the winding layer (i.e., with respect to the winding layer). For example, the turn position may be based on any reference or numbering system as desired or as appropriate. By way of an example only and without limitation, the outermost winding turn may be referred to as being at turn position 1, the immediately subsequent winding turn may be referred to as being at turn position 2, and so on, until the innermost winding turn, such as illustrated in FIGs. 6B and 9 described hereinbefore. Accordingly, the turn position may also be referred to as a turn index.

[0036] In various embodiments, for the above-mentioned each of the plurality of winding layers and for one or more of the plurality of intermediate winding turns of the winding layer, the winding turn of the winding layer and the intermediate winding turn of the above-mentioned another winding layer between which the corresponding coil transition of the coil occurs are winding turns at a different turn position (e.g., with respect to the respective winding layer). In other words, the corresponding coil transition is between winding turns at different turn position, such as illustrated in FIG. 22 to be described later below according to various example embodiments of the present invention.

[0037] In various embodiments, the plurality of winding turns 1212 of each of the plurality of winding layers 1208 collectively form a plurality of axial groups (e.g., column groups) of winding turns, each axial group of winding turns comprising winding turns at a same turn position (e.g., with respect to the respective winding layer). For illustration purpose, FIG. 12B depicts a schematic drawing of the multilayer coupler 1200 as shown in FIG. 12 A, but with the plurality of axial groups of winding turns shown. As shown in FIG. 12B, each axial group of winding turns comprising winding turns of the plurality of winding layers 1208 at the same turn position. As an example, the outermost axial group comprises all winding turns of the plurality of winding layers at turn position 1, the immediately subsequent axial group comprises all winding turns of the plurality of winding layers at turn position 2, and so on.

[0038] In various embodiments, in each of the plurality of axial groups 1220 of winding turns, for each winding turn except a last (or final) winding turn of the axial group 1220 of winding turns, the winding turn comprises a first transition portion of the one or more transition portions 1216 at which the corresponding coil transition of the coil occurs between the winding turn and the above-mentioned another winding turn in the axial group of winding turns.

[0039] In various embodiments, for each winding turn except the last (or final) winding turn of the axial group of winding turns, at the first transition portion of the winding turn, the corresponding coil transition of the coil occurs from the winding turn to an immediately adjacent (or subsequent) winding turn in the axial group of winding turns.

[0040] In various embodiments, for each pair of immediately adjacent axial groups of the plurality of axial groups 1220 of winding turns, in a first axial group of winding turns of the pair, for each winding turn except the last (or final) winding turn of the axial group of winding turns, at the first transition portion of the winding turn, the corresponding coil transition of the coil occurs from the winding turn to the immediately adjacent winding turn in the axial group of winding turns is in a first transition direction, and in a second axial group of winding turns of the pair, for each winding turn except the last (or final) winding turn of the axial group of winding turns, at the first transition portion of the winding turn, the corresponding coil transition of the coil occurs from the winding turn to the immediately adjacent winding turn in the axial group of winding turns is in a second transition direction. In this regard, the first and second transition directions are opposite in direction. In other words, winding turns in immediately adjacent axial groups of winding turns are wound in opposite transition directions with respect to an axial direction (e.g., a vertical axis), such as shown in FIG. 16 to be described later below according to various example embodiments of the present invention.

[0041] In various embodiments, for each pair of immediately adjacent axial groups of the plurality of axial groups 1220 of winding turns, in a first axial group of winding turns of the pair, for each winding turn except the last (or final) winding turn of the axial group of winding turns, at the first transition portion of the winding turn, the corresponding coil transition of the coil occurs from the winding turn to the immediately adjacent winding turn in the axial group of winding turns is in a first transition direction, and in a second axial group of winding turns of the pair, for each winding turn except the last (or final) winding turn of the axial group of winding turns, at the first transition portion of the winding turn, the corresponding coil transition of the coil occurs from the winding turn to the immediately adjacent winding turn in the axial group of winding turns is in the first transition direction. In other words, winding turns in immediately adjacent axial groups of winding turns are wound in the same transition directions with respect to an axial direction (e.g., a vertical axis), such as shown in FIG. 19 to be described later below according to various example embodiments of the present invention.

[0042] In various embodiments, the last winding turn of the first axial group of winding turns comprises a second transition portion at which the coil transitions to a first winding turn of the second axial group of winding turns. In this regard, the first winding turn and the last winding turn of the second axial group of winding turns are at opposite ends of the second axial group of winding turns. For example, as shown in FIG. 16, if the winding turn at turn position 1 at layer 2 is the last winding turn of the first axial group, the winding turn comprises a second transition portion at which the coil transitions to a first winding turn (the winding turn at layer 2) of the second axial group (at turn position 2). As another example, as shown in FIG. 19, if the winding turn at turn position 1 at layer 2 is the last winding turn of the first axial group, the winding turn comprises a second transition portion at which the coil transitions to a first winding turn (the winding turn at layer 1) of the second axial group (at turn position 2). Accordingly, in various embodiments, a first winding turn and a last winding turn of an axial group of winding turns may be defined with respect to the direction of coil transition across the winding turns in the axial group of winding turns, or in other words, with respect to where the coil transition across the winding turns within the axial group begins (corresponding to the first winding turn) and ends (corresponding to the last winding turn).

[0043] In various embodiments, in each of the plurality of axial groups 1220 of winding turns, the first transition portion of each winding turn in the axial group of winding turns is at least substantially aligned with respect to an axial direction (e.g., along a vertical axis). In various embodiments, in each of the plurality of winding layers, the first transition portion of each winding turn in the winding layer is at least substantially aligned with respect to a lateral direction (e.g., along a horizontal axis). For example, as shown in FIG. 20B to be described later below according to various example embodiments of the present invention, the transition portions (corresponding to the above-mentioned first transition portion) are aligned with respect to a vertical axis and a horizontal axis, or in other words, at the same corresponding portions of the winding turns.

[0044] In various embodiments, for each of the plurality of winding layers 1208, each of the plurality of winding turns 1212 of the winding layer is wound along a plane (e.g., a horizontal plane) of the winding layer and forms at least substantially a complete loop along the plane of the winding layer.

[0045] In various embodiments, for each of the plurality of winding layers 1208, the one or more transition portions of each of the plurality of winding turns 1212 of the winding layer comprises a plurality of transition portions, including the first transition portion, at which the corresponding coil transition of the coil occurs between the winding turn of the winding layer and a winding turn of another winding layer of the plurality of winding layers 1208. In other words, each winding turn may have multiple transition portions at which the corresponding transition of the coil occurs, such as shown in FIGs. 23 A and 23B to be described later below according to various example embodiments of the present invention.

[0046] In various embodiments, the plurality of transition portions of each of the plurality of winding turns 1216 are located along the winding turn based on a predetermined pattern, such as but limited to, periodically located (e.g., at a regular interval).

[0047] In various embodiments, for each of the plurality of winding layers 1208, each of the plurality of winding turns 1212 of the winding layer comprises a plurality of winding turn portions, each winding turn portion being wound along a plane of the winding layer and comprising at least one of the plurality of transition portions. In this regard, the plurality of winding turn portions of the winding turn collectively form the winding turn along the plane of the winding layer. In other words, the winding turn of a winding layer is formed by the corresponding plurality of winding turn portions (i.e., at the corresponding turn position) wound along the plane of the winding layer.

[0048] In various embodiments, the coil 1204 is configured as one continuous winding.

[0049] In various embodiments, the coil 1204 forms (or constitutes) a first coil cell, and the multilayer coupler 1200 further comprises one or more additional coil cells connected to the first coil cell, each additional coil cell comprising a second coil configured for wireless power transfer based on magnetic induction and has a multilayer winding structure. The multilayer winding structure comprises a plurality of winding layers, each of the plurality of winding layers comprising a plurality of winding turns. In particular, for each of the plurality of winding layers, at least each of a plurality of intermediate winding turns of the plurality of winding turns of the winding layer comprises one or more transition portions at which a corresponding coil transition of the second coil occurs between the intermediate winding turn of the winding layer and a winding turn of another winding layer of the plurality of winding layers. In various embodiments, each additional coil cell may be configured in the same or similar (or corresponding) manner as the first coil cell (i.e., coil 1204) as described herein according to various embodiments and thus need not be repeated with respect to each additional coil cell for clarity and conciseness. It will be appreciated by a person skilled in the art that the present invention is not limited to any particular number of additional coil cells, and the number of additional coil cells included in the multilayer coupler 1200 may be determined as desired or as appropriate for various purposes. Accordingly, in various embodiments, for the above- mentioned each additional coil cell and the above-mentioned each of the plurality of winding layers, each of the plurality of winding turns of the winding layer of the additional coil cell comprises one or more transition portions at which a corresponding coil transition of the coil occurs between the winding turn of the winding layer and a winding turn of another winding layer of the plurality of winding layers of the additional coil cell. In various embodiments, the one or more additional coil cells may be connected to the first coil cell in series or in parallel.

[0050] In various embodiments, the multilayer coupler 1200 is (or may be implemented as) a transmitter coupler configured to receive a time-varying current from a power source connected thereto for generating a magnetic field to perform wireless power transfer with a receiver coupler over an air gap based on magnetic induction.

[0051] In various embodiments, the multilayer coupler 1200 is (or may be implemented as) a receiver coupler configured to couple with a magnetic field generated from a transmitter coupler to induce a current in the receiver coupler for supplying power to an electrical load connected to the receiver couple to perform wireless power transfer with the transmitter coupler over an air gap based on magnetic induction.

[0052] FIG. 13 depicts a schematic drawing of a system 1300 for wireless power transfer according to various embodiments of the present invention. The system 1300 comprises a wireless power transmitter 1320 and a wireless power receiver 1350 separated by an air gap 1352. It will be appreciated by a person skilled in the art that the air gap may be configured as desired or as appropriate for various practical applications, for example, small air gap of less than 5 mm. [0053] In various embodiments, the wireless power transmitter 1320 comprises a power source 1324 configured to generate a time-varying current; and a transmitter coupler 1328 (e.g., configured as described hereinbefore) connected (electrically connected) to the power source 1324. Accordingly, the power source 1324 and the transmitter coupler 1328 may together form a circuit (transmitter circuit). In this regard, the transmitter coupler 1328 is configured to receive the time-varying current from the power source 1324 for generating a magnetic field 1332 to perform wireless power transfer with a receiver coupler 1360 over the air gap 1352 based on magnetic induction.

[0054] In various embodiments, the wireless power receiver 1350 comprises an electrical load 1356; and the receiver coupler 1360 (e.g., configured as described hereinbefore) connected (electrically connected) to the electrical load 1356. Accordingly, the receiver coupler 1360 and the electrical load 1356 may together form a circuit (receiver circuit). In this regard, the receiver coupler 1360 is configured to couple with the magnetic field 1332 generated from the transmitter coupler 1328 to induce a current in the receiver coupler 1360 for supplying power to the electrical load 1356 connected to the receiver coupler 1360 to perform wireless power transfer with the transmitter coupler 1328 over the air gap 1352 based on magnetic induction.

[0055] In various embodiments, at least one of the transmitter coupler 1328 and the receiver coupler 1360 is a multilayer coupler 1200 as described herein according to various embodiments of the present invention. In various embodiments, the transmitter coupler 1328 and the receiver coupler 1360 are each a multilayer coupler 1200 as described herein according to various embodiments of the present invention. In various embodiments, only one of the transmitter coupler 1328 and the receiver coupler 1360 is a multilayer coupler 1200 as described herein according to various embodiments of the present invention.

[0056] In various embodiments, the transmitter coupler 1328 and the receiver coupler 1360 may be configured to have the same or similar configuration or shape, according to the winding strategy or technique as described herein with reference to the multilayer coupler 1200 according to various embodiments. In various other embodiments, the transmitter coupler 1328 and the receiver coupler 1360 may be configured to have different configurations or shapes. For example, the transmitter coupler 1328 and the receiver coupler 1360 may be configured according to the winding strategy or technique as described herein with reference to the multilayer coupler 1200 according to various embodiments, but transmitter coupler 1328 may be configured to have a different configuration or shape as the receiver coupler 1360. For example, the coil of the transmitter coupler 1328 may have a different configuration or shape to that of the receiver coupler 1360, the number of winding turns per winding layer in the transmitter coupler 1328 may be different to that in the receiver coupler 1360, and/or the number of coil cells in the transmitter coupler 1328 may be different to that in the receiver coupler 1360. For example, different combinations of configurations or shapes between the transmitter and receiver coupler may be selected from, but not limited to, square, rectangular, circular, triangle, trapezoid, hexagon and so on. For example, different number of coil cells in the transmitter and receiver couplers, respectively, may be in the range of one to five coil cells, or one to two coil cells.

[0057] In various embodiments, only one of the transmitter coupler 1328 and the receiver coupler 1360 may be configured according to the multilayer coupler 1200 as described herein according to various embodiments, and the other one of the transmitter coupler 1328 and the receiver coupler 1360 may be configured as a conventional coupler (e.g., conventional single or multilayer coupler).

[0058] The electrical load 1356 may be any electrical component or element requiring power for performing an operation or a function, or to store power/energy, such as but not limited to, a rechargeable battery.

[0059] It will be appreciated by a person skilled in the art that additional element(s) or component(s) may be added to the wireless power transmitter 1320 and/or the wireless power receiver 1350 as desired or as appropriate for various purpose, such as a resonance capacitor to form a resonance circuit configured for resonant inductive power transfer. As another example, it will be appreciated by a person skilled in the art that the wireless power receiver 1350 may include an element or component (e.g., a bidirectional rectifier) configured to convert the timevarying current (AC) induced by the receiver coupler to a direct current (DC) if the electrical load 1356 (e.g., a rechargeable battery) requires a direct current.

[0060] FIG. 14 depicts a flow diagram of a method 1400 of wireless power transfer, according to various embodiments of the present invention. The method 1400 comprises: generating (at 1402), by a power source 1324 at a wireless power transmitter 1320, a timevarying current; and receiving (at 1404), by a transmitter coupler 1328 at the wireless power transmitter 1320 connected to the power source 1324, the time-varying current from the power source 1324 for generating a magnetic field 1332 to perform wireless power transfer with a receiver coupler 1360 over an air gap 1352 based on magnetic induction; coupling (at 1406), by the receiver coupler 1360 at a wireless power receiver 1350 connected to an electrical load 1356, with the magnetic field 1332 generated from the transmitter coupler 1328 to induce a current in the receiver coupler 1360 to perform wireless power transfer with the transmitter coupler 1328 over the air gap 1352 based on magnetic induction; and supplying (at 1408), by the receiver coupler 1360 at the wireless power receiver 1350, power to the electrical load 1356 connected thereto based on the current induced therein. In particular, as described hereinbefore, at least one of the receiver coupler 1360 and the transmitter coupler 1328 is a multilayer coupler 1200 as described hereinbefore according to various embodiments of the present invention. As also described hereinbefore, the wireless power transmitter 1320 and the wireless power receiver 1350 are separated by the air gap 1352.

[0061] FIG. 15 depicts a flow diagram of a method 1500 of manufacturing a multilayer coupler for wireless power transfer according to various embodiments of the present invention, such as the multilayer coupler 1200 as described hereinbefore according to various embodiments of the present invention. The method 1500 comprises configuring (at 1502) a coil 1204 for wireless power transfer based on magnetic induction, the coil 1204 having a multilayer winding structure. The multilayer winding structure comprises a plurality of winding layers 1208, each of the plurality of winding layers 1208 comprising a plurality of winding turns 1212. In particular, for each of the plurality of winding layers 1208, at least each of a plurality of intermediate winding turns of the plurality of winding turns 1212 of the winding layer comprises one or more transition portions 1216 at which a corresponding coil transition of the coil occurs between the intermediate winding turn of the winding layer and a winding turn of another winding layer of the plurality of winding layers 1208.

[0062] In various embodiments, the method 1500 is for manufacturing the multilayer coupler 1200 as described hereinbefore according to various embodiments of the present invention, therefore, various aspects or steps of the method 1500 may correspond to various aspects or features of the multilayer coupler 1200 as described herein, and thus need not be repeated with respect to the method 1500 for clarity and conciseness. In other words, various embodiments described herein in context of the multilayer coupler 1200 are analogously valid for the method 1500, and vice versa. In various embodiments, the coil 1204 may be formed on a substrate made of a non-conductive material, such as but not limited to, non-metallic epoxy resin, plastic-like acrylonitrile butadiene styrene (ABS), acrylic materials, nylon and so on.

[0063] Furthermore, a coil (e.g., a wire or a group/bundle of wires) may be formed into a configuration or shape as described herein according to various embodiments (e.g., as described herein with reference to FIG. 12A or FIG. 12B) based on existing techniques known in the art. For example, a coil (a continuous winding) may be laid onto a substrate (e.g., mould or housing) that is made of non-conductive materials. The substrate may comprise one or more tracks (or grooves) configured/shaped for accommodating the coil (to be laid therein along the track(s)) for forming/configuring the coil into a desired shape or configuration. In other words, the track(s) may be configured/shaped in the substrate in accordance with (to conform with) a desired coil shape or configuration, and the coil may then be configured (wound) into the desired shape/configuration as described herein according to various embodiments of the present invention by laying/placing the coil along the track(s). For example, the tracks (or grooves) may be formed on both sides of a substrate to create a two-layer structure. Multiple of these substrates with their individual tracks (or grooves) may also be stacked to form a coil having a multilayer winding structure. As another example, a cast may be configured/designed similarly to the above-described substrate with tracks (or grooves) in order to accommodate or secure the wire in the desired shape or configuration before being encased in an epoxy. The cast may thereafter be removed once the epoxy resin is hardened and the coil shape is fixed. As a further example, the cast may also be left as a support structure. As yet another example, the conductive winding of the desired coil shape or configuration may be formed using multiple layers of printed circuit boards (PCBs) to form the winding turns.

[0064] It will be appreciated by a person skilled in the art that the terminology used herein is for the purpose of describing various embodiments only and is not intended to be limiting of the present invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

[0065] Furthermore, any reference to an element or a feature herein using a designation such as “first”, “second” and so forth does not limit the quantity or order of such elements or features, unless stated or the context requires otherwise. For example, such designations are used herein as a convenient way of distinguishing between two or more elements or instances of an element. Thus, a reference to first and second elements does not mean that only two elements can be employed, or that the first element must precede the second element. In addition, a phrase referring to “at least one of’ a list of items refers to any single item therein or any combination of two or more items therein. [0066] In order that the present invention may be readily understood and put into practical effect, various example embodiments of the present invention will be described hereinafter by way of examples only and not limitations. It will be appreciated by a person skilled in the art that the present invention may, however, be embodied in various different forms or configurations and should not be construed as limited to the example embodiments set forth hereinafter. Rather, these example embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present invention to those skilled in the art.

[0067] In particular, for better understanding of the present invention and without limitation or loss of generality, unless stated otherwise, various example embodiments of the present invention will now be described with respect to a multilayer winding structure whereby each of the plurality of winding turns of each winding layer comprises one or more transition portions at which a corresponding interlayer coil transition of the coil occurs. However, it will be appreciated by a person skilled in the art that the present invention is not limited as such, as long as at least each of a plurality of intermediate winding turns of the plurality of winding turns of each winding layer comprises one or more transition portions at which a corresponding interlayer coil transition of the coil occurs, such as described hereinbefore according to various embodiments of the present invention.

[0068] According to various example embodiments, there is provide a multilayer coupler comprising a coil having a multilayer winding structure (e.g., based on a winding strategy (or technique) or sequence) configured according to various example embodiments of the present invention. In various example embodiments, the coil configured to have such a multilayer winding structure may have a serpentine shape (e.g., a general “S” shape) in a lateral direction (e.g., a transverse direction or a radial direction), and thus may be referred to as a serpentine coil (e.g., an “S” coil (or S-coil)).

[0069] FIG. 16 depicts a schematic cross-sectional view of a section of a first example multilayer coupler 1600 according to various example embodiments of the present invention, along with an associated first winding sequence (based on winding turns or loops) for forming the multilayer winding structure of the coil thereof illustrated or denoted by arrows 1610. The first example multiplayer coupler 1600 comprises a coil 1604 configured for wireless power transfer based on magnetic induction and has a multilayer winding structure, the multilayer winding structure comprising a plurality of winding layers 1608, each of the plurality of winding layers 1608 comprising a plurality of winding turns 1612. [0070] In the first winding sequence associated with the first example multilayer coupler 1600, as illustrated in FIG. 16, the coil 1604 is wound (in winding turns or loops) from one side or end (e.g., a first side or end, such as corresponding to innermost or outermost winding turns with respect to a center or core of the first example multilayer coupler 1600) to another side or end (e.g., a second side or end, such as corresponding to the outermost or innermost windings turn (opposite to the first side or end) with respect to the center) of the first example multilayer coupler 1600, while transitioning across the plurality of winding layers (i.e., interlayer coil transition) at each turn position of the first example multilayer coupler 1600. In various example embodiments, the plurality of winding turns of each of the plurality of winding layers may collectively form a plurality of axial groups of winding turns, each axial group of winding turns comprising winding turns at a same turn position (e.g., a first axial group of winding turns at Turn 1, a second axial group of winding turns at Turn 2, and so on). In this regard, according to the first winding sequence, the coil 1604 may be configured to transition across the plurality of winding turns (e.g., one winding turn to another until the last (or final) remaining winding turn, and hence across the plurality of winding layers) within a first axial group of winding turns (e.g., at a first turn position, such as Turn 1), and then transitions to a next (e.g., a second) axial group of winding turns (i.e., at a next turn position (or a second turn position), such as Turn 2) upon completing transitioning in the first axial group of winding turns, where the coil 1604 may then be configured to transition across the plurality of winding turns (e.g., one winding turn to another until the last remaining winding turn, and hence across the plurality of winding layers) within the second axial group of winding turns, and so on, until the last (or final) axial group of winding turns, where the coil 1604 may be configured to transition across the plurality of winding turns (e.g., one winding turn to another until the last remaining winding turn, and hence across the plurality of winding layers) in the last axial group of winding turns. Accordingly, as shown in FIG. 16, the coil 1604 configured to have the above-mentioned multilayer winding structure has a serpentine shape, or more specifically, a general “S” shape, in a lateral direction, and thus may be referred to as a serpentine coil, or more specifically, an “S” coil (or S-coil).

[0071] Accordingly, for each of the plurality of winding layers 1608, each of the plurality of winding turns 1612 of the winding layer comprises a transition portion at which a corresponding coil transition of the coil 1604 occurs between the winding turn of the winding layer and a winding turn of another winding layer of the plurality of winding layers 1608. In particular, in each of the plurality of axial groups of winding turns, for each winding turn except a last winding turn of the axial group of winding turns, the winding turn comprises a transition portion (e.g., corresponding to the first transition portion as described hereinbefore according to various embodiments) at which the corresponding coil transition of the coil 1604 occurs between the winding turn and another winding turn in the axial group of winding turns, and in various example embodiments, from the winding turn to an immediately adjacent winding turn in the axial group of winding turns (e.g., from layer 1 to layer 2 with respect to the axial group at Turn 1).

[0072] In addition, according to the first winding sequence, for each pair of immediately adjacent axial groups (e.g., a pair of axial groups at Turns 1 and 2, a pair of axial groups at Turns 2 and 3, and so on) of the plurality of axial groups of winding turns, in a first axial group (e.g. the axial group at Turn 1 for the pair of axial groups at Turns 1 and 2) of winding turns of the pair, for each winding turn except the last winding turn of the axial group of winding turns, at the first transition portion of the winding turn, the corresponding coil transition of the coil 1604 occurs from the winding turn to the immediately adjacent winding turn in the axial group of winding turns is in a first transition direction 1616, and in a second axial group (e.g. the axial group at Turn 2 for the pair of axial groups at Turns 1 and 2) of winding turns of the pair, for each winding turn except the last winding turn of the axial group of winding turns, at the first transition portion of the winding turn, the corresponding coil transition of the coil 1604 occurs from the winding turn to the immediately adjacent winding turn in the axial group of winding turns is in a second transition direction 1618. In this regard, the first and second transition directions 1616, 1618 are opposite in direction, such as shown in FIG. 16.

[0073] Furthermore, according to the first winding sequence, the last winding turn of the first axial group (e.g., the axial group at Turn 1 for the pair of axial groups at Turns 1 and 2) of winding turns comprises a second transition portion at which the coil transitions to a first winding turn of the second axial group of winding turns (e.g. the axial group at Turn 2 for the pair of axial groups at Turns 1 and 2), such as the coil transition illustrated by the arrow 1622 in FIG. 16. Accordingly, in various embodiments, a first winding turn and a last winding turn of an axial group of winding turns may be defined with respect to the direction of coil transition across the winding turns in the axial group of winding turns, or in other words, with respect to where the coil transition across the winding turns within the axial group begins (corresponding to the first winding turn) and ends (corresponding to the last winding turn).

[0074] By way of examples only and without limitations, FIGs. 17A to 17C depict simplified schematic drawings of example rectangular multilayer couplers, each comprising a coil configured to have a multilayer winding structure according to the first winding sequence, according to various example embodiments of the present invention. In particular, FIG. 17A depicts a simplified schematic drawing of an example rectangular two-layer coupler 1704 comprising a coil 1706 configured to have a multilayer winding structure according to the first winding sequence, FIG. 17B depicts a simplified schematic drawing of an example rectangular three-layer coupler 1714 comprising a coil 1716 configured to have a multilayer winding structure according to the first winding sequence, and FIG. 17C depicts a simplified schematic drawing of an example rectangular four-layer coupler 1724 comprising a coil 1726 configured to have a multilayer winding structure according to the first winding sequence. Accordingly, it can be appreciated by a person skilled in the art that the multilayer winding structure configured according to the first winding sequence may comprise any number of multiple winding layers as desired or as appropriate, and the multilayer winding structure is not limited to any particular number of multiple winding layers. Furthermore, it can be appreciated by a person skilled in the art that the multilayer winding structure configured according to the first winding sequence may comprise any number of winding turns per winding layer as desired or as appropriate, and the multilayer winding structure is not limited to any particular number of winding turns per winding layer.

[0075] FIG. 18 depicts a schematic cross-sectional view of a section of various example multilayer couplers according to various example embodiments of the present invention, along with the associated winding sequence for forming the multilayer winding structure of the coil thereof illustrated or denoted by arrows. In particular, FIG. 18 illustrates that a coil of a multilayer coupler may comprise a plurality of coil portions (or coil sections, such as represented by dashed boxes in FIG. 18), and one or more coil portions of the plurality of coil portions may be configured to have a multilayer winding structure according to the first winding sequence, and other one or more coil portions of the plurality of coil portions may be configured according to other winding sequence as desired or as appropriate, such as a conventional one- layer winding sequence or also according to the first winding sequence. As an example, the three-layer coupler 1714 shown in FIG. 18 may comprise two coil portions, namely, a first coil portion 1718 configured to have a multilayer winding structure according to the first winding sequence and a second coil portion 1720 configured according to a conventional one-layer winding sequence, whereby the first coil portion 1718 transitions to the second coil portion 1720 as shown in FIG. 18. As another example, the four-layer coupler 1724 shown in FIG. 18 may comprise two coil portions, namely, a first coil portion 1728 configured to have a multilayer winding structure according to the first winding sequence and a second coil portion 1730 also configured to have a multilayer winding structure according to the first winding sequence (but in an opposite direction or manner compared to the first coil portion 1728), whereby the first coil portion 1728 transitions to the second coil portion 1730 as shown in FIG. 18. Further examples of the four-layer coupler 1724 having a first coil portion configured to have a multilayer winding structure according to the first winding sequence and a second coil portion configured according to other winding sequences or also according to the first winding sequence are also shown in FIG. 18.

[0076] FIG. 19 depicts a schematic cross-sectional view of a section of a second example multilayer coupler 1900 according to various example embodiments of the present invention, along with an associated second winding sequence (based on winding turns or loops) for forming the multilayer winding structure of the coil thereof illustrated or denoted by the arrows. The second example multilayer coupler 1900 may be the same or similar as the first example multilayer coupler 1600, except that the multilayer winding structure of the coil thereof is configured according to a second winding sequence. Accordingly, the second example multilayer coupler 1900 comprises a coil 1904 configured for wireless power transfer based on magnetic induction and has a multilayer winding structure, the multilayer winding structure comprising a plurality of winding layers 1908, each of the plurality of winding layers 1908 comprising a plurality of winding turns 1912.

[0077] In the second winding sequence associated with the second example multilayer coupler 1900, as illustrated in FIG. 19, the coil 1904 is wound (in winding turns or loops) from one side or end (e.g., a first side or end, such as corresponding to innermost or outermost winding turns with respect to a center or core of the second example multilayer coupler 1900) to another side or end (e.g., a second side or end, such as corresponding to the outermost or innermost windings turn (opposite to the first side or end) with respect to the center) of the second example multilayer coupler 1900, while transitioning across the plurality of winding layers (i.e., interlayer coil transition) at each turn position of the second example multilayer coupler 1900. Similar to the first example multilayer coupler 1600, in various example embodiments, the plurality of winding turns of each of the plurality of winding layers may collectively form a plurality of axial groups of winding turns, each axial group of winding turns comprising winding turns at a same turn position with respect to the respective winding layer (e.g., a first axial group of winding turns at Turn 1, a second axial group of winding turns at Turn 2, and so on). In this regard, according to the second winding sequence, the coil 1904 may be configured to transition across the plurality of winding turns (e.g., one winding turn to another until the last remaining winding turn, and hence across the plurality of winding layers) within a first axial group of winding turns (e.g., at a first turn position, such as Turn 1), and then transitions to a next (e.g., a second) axial group of winding turns (i.e., at a next turn position (or a second turn position), such as Turn 2) upon completing transitioning in the first axial group of winding turns, where the coil 1904 may then be configured to transition across the plurality of winding turns (e.g., one winding turn to another until the last remaining winding turn, and hence across the plurality of winding layers) within the second axial group of winding turns, and so on, until the last axial group of winding turns, where the coil 1904 may be configured to transition across the plurality of winding turns (e.g., one winding turn to another until the last remaining winding turn, and hence across the plurality of winding layers) in the last axial group of winding turns. Accordingly, as shown in FIG. 19, the coil 1904 configured to have the above- mentioned multilayer winding structure has a serpentine shape, or more specifically, a general “Z” shape, in a lateral direction, and thus may be referred to as a serpentine coil, or more specifically, an “Z” coil (or Z-coil).

[0078] Accordingly, for each of the plurality of winding layers 1908, each of the plurality of winding turns 1912 of the winding layer comprises a transition portion at which a corresponding coil transition of the coil 1904 occurs between the winding turn of the winding layer and a winding turn of another winding layer of the plurality of winding layers 1908. In particular, in each of the plurality of axial groups of winding turns, for each winding turn except a last winding turn of the axial group of winding turns, the winding turn comprises a transition portion (e.g., corresponding to the first transition portion as described hereinbefore according to various embodiments) at which the corresponding coil transition of the coil 1904 occurs between the winding turn and another winding turn in the axial group of winding turns, and in various example embodiments, from the winding turn to an immediately adjacent winding turn in the axial group of winding turns (e.g., from layer 1 to layer 2 with respect to the axial group at Turn 1).

[0079] In addition, according to the second winding sequence, for each pair of immediately adjacent axial groups (e.g., a pair of axial groups at Turns 1 and 2, a pair of axial groups at Turns 2 and 3, and so on) of the plurality of axial groups of winding turns, in a first axial group (e.g. the axial group at Turn 1 for the pair of axial groups at Turns 1 and 2) of winding turns of the pair, for each winding turn except the last winding turn of the axial group of winding turns, at the first transition portion of the winding turn, the corresponding coil transition of the coil occurs from the winding turn to the immediately adjacent winding turn in the axial group of winding turns is in a first transition direction 1916, and in a second axial group (e.g. the axial group at Turn 2 for the pair of axial groups at Turns 1 and 2) of winding turns of the pair, for each winding turn except the last winding turn of the axial group of winding turns, at the first transition portion of the winding turn, the corresponding coil transition of the coil occurs from the winding turn to the immediately adjacent winding turn in the axial group of winding turns is also in the first transition direction 1918, such as shown in FIG. 19.

[0080] Furthermore, according to the second winding sequence, the last winding turn of the first axial group (e.g., the axial group at Turn 1 for the pair of axial groups at Turns 1 and 2) of winding turns comprises a second transition portion at which the coil transitions to a first winding turn of the second axial group of winding turns (e.g. the axial group at Turn 2 for the pair of axial groups at Turns 1 and 2), such as the coil transition illustrated by the arrow 1922 in FIG. 19. Accordingly, in various embodiments, a first winding turn and a last winding turn of an axial group of winding turns may be with respect to the direction of coil transition across the winding turns in the axial group of winding turns, or in other words, with respect to where the coil transition across the winding turns within the axial group begins (corresponding to the first winding turn) and ends (corresponding to the last winding turn).

[0081] By way of examples only and without limitations, FIGs. 20A to 20C depict simplified schematic drawings of rectangular multilayer couplers, each comprising a coil configured to have a multilayer winding structure according to the second winding sequence, according to various example embodiments of the present invention. In particular, FIG. 20A depicts a simplified schematic drawing of a rectangular two-layer coupler 2004 comprising a coil 2006 configured to have a multilayer winding structure according to the second winding sequence, FIG. 20B depicts a simplified schematic drawing of a perspective view of the rectangular two-layer coupler 2004, and FIG. 20C depicts a simplified schematic drawing of a rectangular three-layer coupler 2014 comprising a coil 2016 configured to have a multilayer winding structure according to the second winding sequence. Accordingly, similarly, it can be appreciated by a person skilled in the art that the multilayer winding structure configured according to the second winding sequence may comprise any number of multiple winding layers as desired or as appropriate, and the multilayer winding structure is not limited to any particular number of multiple winding layers. Furthermore, it can be appreciated by a person skilled in the art that the multilayer winding structure configured according to the second winding sequence may comprise any number of winding turns per winding layer as desired or as appropriate, and the multilayer winding structure is not limited to any particular number of winding turns per winding layer.

[0082] FIG. 21 depicts a schematic cross-sectional view of a section of various example multilayer couplers according to various example embodiments of the present invention, along with the associated winding sequence for forming the multilayer winding structure of the coil thereof illustrated or denoted by arrows. In particular, similar to FIG. 18, FIG. 21 illustrates that a coil of a multilayer coupler may comprise a plurality of coil portions (or coil sections, such as represented by dashed boxes in FIG. 21), and one or more coil portions of the plurality of coil portions may be configured to have a multilayer winding structure according to the second winding sequence, and other one or more coil portions of the plurality of coil portions may be configured according to other winding sequence as desired or as appropriate, such as a conventional one-layer winding sequence or also according to the second winding sequence. As an example, the three-layer coupler 2014 shown in FIG. 21 may comprise two coil portions, namely, a first coil portion 2018 configured to have a multilayer winding structure according to the second winding sequence and a second coil portion 2020 configured according to a conventional one-layer winding sequence, whereby the first coil portion 2018 transitions to the second coil portion 2020 as shown in FIG. 21. As another example, the four-layer coupler 2024 shown in FIG. 21 may comprise two coil portions, namely, a first coil portion 2028 configured to have a multilayer winding structure according to the second winding sequence and a second coil portion 2030 also configured to have a multilayer winding structure according to the second winding sequence (but in an opposite direction or manner compared to the first coil portion 2028), whereby the first portion 2028 transitions to the second portion 2030 as shown in FIG. 21. A further example of the four-layer coupler 2024 having a first coil portion and a second coil portion both configured to have a multilayer winding structure according to the second winding sequence, whereby the first coil portion 2028 transitions to the second coil portion 2030 in a different manner.

[0083] FIG. 22 depicts a schematic cross-sectional view of a section of a third example multilayer coupler 2200 according to various example embodiments of the present invention, along with an associated third winding sequence (based on winding turns or loops) for forming the multilayer winding structure of the coil thereof illustrated or denoted by the arrows. The third example multilayer coupler 2200 may be the same or similar as the first or second example multilayer coupler, except that the multilayer winding structure of the coil thereof is configured according to a third winding sequence. Accordingly, the third example multilayer coupler 2200 comprises a coil 2204 configured for wireless power transfer based on magnetic induction and has a multilayer winding structure, the multilayer winding structure comprising a plurality of winding layers, each of the plurality of winding layers comprising a plurality of winding turns. [0084] In the third winding sequence associated with the third example multilayer coupler 2200, as illustrated in FIG. 22, the coil 2204 is wound (in winding turns or loops) from one side or end (e.g., a first side or end, such as corresponding to innermost or outermost winding turns with respect to a center or core of the third example multilayer coupler 2200) to another side or end (e.g., a second side or end, such as corresponding to the outermost or innermost windings turn (opposite to the first side or end) with respect to the center) of the third example multilayer coupler 2200, while transitioning across the plurality of winding layers (i.e., interlayer coil transition) at at least each of a plurality of intermediate winding turns of the plurality of winding turns. In particular, according to the third winding sequence, the coil 2204 may not be configured to transition to another winding layer at all winding turns of a winding layer, but at at least a plurality of intermediate winding turns of the winding layer. In other words, according to the third winding sequence, interlayer coil transition at one or more intermediate winding turns at a winding layer may be skipped (i.e., may not occur), and may simply transition to another winding turn at the same winding layer. For example, the plurality of intermediate winding turns at which interlayer coil transition occurs may be periodically located at the winding layer, such as based on a predetermined pattern. For example, upon the coil transitioning to a winding turn (e.g., at turn position 1) at a winding layer from another winding layer, the next intermediate winding turn at the winding layer at which interlayer coil transition occurs may be located two or more turn positions (e.g., at turn position 2 or 3) away from the winding turn. Accordingly, the predetermined pattern may be a predetermined number of turn position away. By way of an example only and without limitations, as shown in FIG. 22, upon the coil transitioning to a first winding turn (e.g., at turn position 1) at a winding layer (e.g., layer 2) from another winding layer (e.g., layer 1), coil transition from the first winding turn may proceed to a second winding turn (e.g., an immediately subsequent winding turn, i.e., at turn position 2) at the same winding layer (e.g., layer 2), and further transition from the second winding turn to a third winding turn (e.g., at turn position 3) at the same winding layer, and then transition at the third winding turn to a winding turn (e.g., at turn position 2) of another winding layer (e.g., layer 2), and so on, until the last remaining winding turn (e.g., innermost winding turn). Accordingly, in the case of the predetermined number of turn position away being 2, interlayer coil transition at the second winding turn of the winding layer may be skipped. Furthermore, as shown in FIG. 22, one or more interlayer transitions may be between winding turns at different turn positions (or different axial groups).

[0085] By way of examples only and without limitations, FIG. 22 further depicts a simplified schematic drawing of the third example multilayer coupler 2200 in the form of a rectangular multilayer coupler comprising a coil 2204 configured to have a multilayer winding structure according to the third winding sequence, according to various example embodiments of the present invention. In particular, FIG. 22 depicts a simplified schematic drawing of a rectangular two-layer coupler 2200 comprising a coil 2204 configured to have a multilayer winding structure according to the third winding sequence. Similarly, it can be appreciated by a person skilled in the art that the multilayer winding structure configured according to the third winding sequence may comprise any number of multiple winding layers as desired or as appropriate, and the multilayer winding structure is not limited to any particular number of multiple winding layers. Furthermore, it can be appreciated by a person skilled in the art that the multilayer winding structure configured according to the third winding sequence may comprise any number of winding turns per winding layer as desired or as appropriate, and the multilayer winding structure is not limited to any particular number of winding turns per winding layer.

[0086] In various example embodiments, the multilayer coupler as described hereinbefore according to various example embodiments of the present invention may comprise one transition portion (e.g., corresponding to the first transition portion as described hereinbefore according to various embodiments) per winding turn, such as shown in FIGs. 17A to 17C and 20A to 20C. In various example embodiments, in each of the plurality of axial groups of winding turns, the one transition portion of each winding turn in the axial group of winding turns is at least substantially aligned with respect to an axial direction, such as shown in FIGs. 17A to 17C and 20A to 20C. Furthermore, in each of the plurality of winding layers, the one transition portion of each winding turn in the winding layer is at least substantially aligned with respect to a lateral direction, such as also shown in FIGs. 17A to 17C and 20A to 20C. By way of an example only and without limitation, the one transition portion may be located or positioned at a side (e.g., top side) middle portion of the coil in the case of the coil having a rectangular shape, such as shown in FIGs. 17A to 17C and 20A to 20C.

[0087] In various example embodiments, the multilayer coupler may comprise a plurality of transition portions per winding turn. That is, for each of the plurality of winding layers, each of the plurality of winding turns of the winding layer comprises a plurality of transition portions at which the corresponding coil transition of the coil occurs between the winding turn of the winding layer and a winding turn of another winding layer of the plurality of winding layers. In various example embodiments, the plurality of transition portions of each of the plurality of winding turns may be periodically located along the winding turn based on a predetermined pattern.

[0088] By way of examples only and without limitations, FIGs. 23A and 23B depict simplified schematic drawings of rectangular multilayer couplers, each comprising a coil configured to have a multilayer winding structure according to the second winding sequence, according to various example embodiments of the present invention, whereby a plurality of transition portions are provided per winding turn. In particular, FIG. 23 A depicts a simplified schematic drawing of a rectangular two-layer coupler 2304 comprising a coil 2306 configured to have a multilayer winding structure according to the second winding sequence, whereby two transition portions are provided per winding turn, and FIG. 23B depicts a simplified schematic drawing of a rectangular two-layer coupler 2314 comprising a coil 2316 configured to have a multilayer winding structure according to the second winding sequence, whereby four transition portions are provided per winding turn. Accordingly, as shown in FIGs. 23A and 23B, the plurality of transition portions of each of the plurality of winding turns may be located along the winding turn based on a predetermined pattern. For example, the plurality of transition portions may be periodically located along the winding turn. In various example embodiments, for each of the plurality of winding layers, each of the plurality of winding turns of the winding layer comprises a plurality of winding turn portions, each winding turn portion being wound along a plane of the winding layer and comprising at least one of the plurality of transition portions. Accordingly, the plurality of winding turn portions of the winding turn collectively form the winding turn along the plane of the winding layer. It will be appreciated by a person skilled in the art that the multilayer winding structure is not limited to any particular number of transition portions per winding turn, and any number of transition portions may be provided per winding turn as desired or as appropriate. Furthermore, it will be appreciated by a person skilled in the art that the location of the one or more transition portions at each winding turn are not limited to any particular locations along the winding turn and their locations may be set as desired or as appropriate.

[0089] Accordingly, it will be appreciated by a person skilled in the art that the multilayer winding structure according to various example embodiments of the present invention is not limited to any particular number of winding turns, winding layers, number of transition portions per winding turn, and the locations of the transition portions at the winding turn.

[0090] With the multilayer winding structure according to various example embodiments of the present invention, the distribution of parasitic element is advantageously improved. Accordingly, the impedance characteristics of the coil is improved across different frequency. For example, at frequency higher than intended operating frequency, the impedance is higher. As a result, the multilayer winding structure according to various example embodiments of the present invention was found to significantly reduce EM noise emission in conduction and radiation path, while achieving the same or better performance of wireless power transfer at intended operating frequency.

[0091] Accordingly, various example embodiments of the present invention provide methods and structures of multilayer winding which significantly improve the impedance characteristics of the multilayer coupler and reduce the EM noise emission (conducted and radiated). As a result, for example, the multilayer coupler when realized as a product can advantageously have a higher potential to conform to specific electromagnetic compatibility regulatory limit. Furthermore, it can reduce the additional EM filter and clamp, thereby reducing cost and weight.

[0092] Accordingly, the multilayer winding structure may be advantageously configured to redistribute parasitic capacitance among different stretch of wire across different winding layers.

[0093] In stark contrast, in existing multilayer structure (e.g., configured based on the first and second conventional winding sequence as described hereinbefore), the coupler may be seen be configured with different coils that resides in different layers, each connected in a series configuration as shown in FIG. 24, where the dashed box represents individual coil components. Accordingly, as can be seen from FIG. 24, in each winding layer, long stretch of winding turns may form a coil. FIG. 25 depicts a schematic drawing of a perspective view of an example conventional multilayer coupler 2500 configured according to the first conventional winding sequence, along with the formation of parasitic capacitances among coils of adjacent winding layers shown. Various example embodiments found that the adjacent winding layers create multiple resonance points in impedance characteristics, resulting in multiple low impedance paths where EM noise easily propagates.

[0094] In stark contrast, without wishing to be bound by theory, based on the multilayer winding structure according to various example embodiments, parasitic capacitances are advantageously redistributed by structuring the stretch of wire across different layers. In this way, the winding is truly distributed across different layers, instead of effectively having a distinctive coil per layer according to the example conventional multilayer coupler 2500. As a result, effective parasitic capacitance is smaller, therefore shifting the low impedance resonant point towards higher frequency, where generated EM noise is significantly smaller (further away from fundamental).

[0095] As mentioned hereinbefore, it will be appreciated by a person skilled in the art that the multilayer winding structure or the coil is not limited to any particular shape, and may be any shape as appropriate, such as rectangular, circular, hexagonal, and so on. Furthermore, one or more different winding layers of multilayer winding structure may also have different coil shapes. For example, the coil may be formed by any type of wires or their combinations (e.g., single round wire, flat wire, magnet wire, bunch wire, Litz wire, PCB traces, and so on). Furthermore, each winding layer may have different number of winding turns, different number of transition portions and/or different transition locations.

[0096] In various example embodiments, the coil configured to have a multilayer winding structure as described hereinbefore according to various example embodiments may form a coil cell (e.g., a first coil cell). In this regard, the multilayer coupler may further comprise one or more additional coil cells connected to the first coil cell, each additional coil cell comprising a second coil configured for wireless power transfer based on magnetic induction and has a multilayer winding structure. The multilayer winding structure comprises a plurality of winding layers, each of the plurality of winding layers comprising a plurality of winding turns. In particular, similarly, for each of the plurality of winding layers, each of the plurality of winding turns of the winding layer comprises one or more transition portions at which a corresponding coil transition of the second coil occurs between the intermediate winding turn of the winding layer and a winding turn of another winding layer of the plurality of winding layers. In other words, each additional coil cell may be configured, for example, according to the first, second or third winding sequence as described hereinbefore according to various example embodiments.

[0097] By way of an example only for illustration purpose, FIGs. 26A to 26C depict simplified schematic drawings of rectangular multilayer couplers comprising a plurality of coil cells. In particular, FIG. 26A depicts a simplified schematic drawing of a rectangular multilayer coupler 2604 comprising three coil cells stacked (e.g., at least partially on top of each other) to form additional coil cell layers and are connected independently. FIG. 26B depicts a schematic drawing of a simplified rectangular multilayer coupler 2614 comprising three coil cells stacked (e.g., at least partially on top of each other) to form additional coil cell layers and are connected in series. FIG. 26C depicts a schematic drawing of a simplified rectangular multilayer coupler 2624 comprising three coil cells stacked (e.g., at least partially on top of each other) to form additional coil cell layers and are connected in parallel.

[0098] The multilayer coupler according to various example embodiments may be applied to, in general, any applications that utilize alternating current (AC) flowing in coil(s) to generate EM flux as means to transfer power, and in particular, wireless power transfer applications. For example, the multilayer coupler is independent of the electronics topology to generate the AC current in coils, therefore it can be applied for, but not limited to, purely inductive wireless power transfer (e.g., in a similar manner as gapped transformer) and resonant wireless power transfer. The multilayer coupler is also not limited to any particular compensation topologies, such as series-series, series-parallel, parallel-series, parallel-parallel, or combinations thereof (e.g., LCL, LCC, CCL, and so on). The multilayer coupler may also be applicable for all power ratings covering from low power applications (e.g., phones, cameras and sensors) to higher power applications (e.g., robots, automatic guided vehicles and electric vehicles). Furthermore, the multilayer coupler is not limited to wireless power application, and may be employed in, for example, induction heating, and more particularly, to the heating coil in an induction cooker, for example, since power is nevertheless transferred wirelessly from the induction heating element to a heated object.

[0099] As an example performance comparison, FIGs. 27A and 27B show the alternating current measurements (AC current waveform) in the multilayer coupler configured according to the second winding sequence according to various example embodiments and a conventional multilayer coupler configured the first conventional winding sequence. With everything being the same except for the magnetic coupler itself, FIG. 27A and FIG. 27B show that the EM noise emission is significantly lower in the multilayer coupler configured according to the second winding sequence according to various example embodiments, thereby demonstrating the significant advantage or technical effect associated with the multilayer coupler according to various example embodiments over conventional multilayer coupler.

[00100] While embodiments of the present invention have been particularly shown and described with reference to specific embodiments, it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the scope of the present invention as defined by the appended claims. The scope of the present invention is thus indicated by the appended claims and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced.