High efficiency resonator coil for large gap wireless power transfer systems

Abstract

High-efficiency resonator coils and coil design methods for large-gap resonant wireless power transfer (WPT) are disclosed. The resonator coils include a coil topology defined by coil parameters, where the turn dimensions per turn (such as trace width and spacing per turn) are configured to reduce or minimize the variance of the z-component of the magnetic field in a region of the charging plane at a specified distance or range from the coil. The Tx resonator coils include capacitor arrangements of tuning capacitors and network matching capacitors to improve coil-to-coil efficiency and end-to-end WPT system performance, for example, for through-wall WPT applications ranging from tens of watts to at least hundreds of watts. The planar resonator coil topology is compatible with manufacturing using low-cost PCB technologies (e.g., with multilayer metals) to reduce losses and improve thermal performance.

Description

Technical Field

[0001] This invention relates to wireless power transfer (WPT) and systems, methods and apparatus for performing WPT, and more particularly to a resonator coil design for resonant inductive power transfer. Background Technology

[0002] Electromagnetic resonant power transfer (also known as resonant inductive wireless power transfer (WPT) or resonant inductive wireless energy transfer) operates by generating electrical energy wirelessly between two coils tuned to resonate at the same frequency. Based on the principle of electromagnetic coupling, a resonant power source injects an oscillating current into the highly resonant coil to generate an oscillating electromagnetic field. The second coil, with the same resonant frequency, receives power from the electromagnetic field and converts it back into current that can be used to power and charge devices.

[0003] For example, standard IEC 63028:2017(E) defines the technical requirements, behaviors, and interfaces for ensuring the interoperability of flexible coupled WPT systems using the AirFuel Alliance Resonant WPT. Resonant inductive energy transfer enables energy to be transferred over longer distances than non-resonant inductive charging (see Table 1 below). For example, the Wireless Power Consortium (WPC) (formerly Qi) deals with (non-resonant) inductive WPTs, which have a limited range, such as a few millimeters. The predecessors of the AirFuel Alliance were PMA, AW4P, and Rezence. AirFuel resonant inductive WPTs have a much larger range, such as a maximum range of 50 millimeters.

[0004] Table 1

[0005] Standards Organization Wireless Power Consortium (Qi) AirFuel Alliance (Rezence) method induction resonance Frequency range 80 to 300 kHz 6.78MHz Maximum transmission range 5mm 50mm Number of charging devices one Can be multiple Communication system Load modulation Bluetooth

[0006] In the context of this disclosure, "large gap WPT" refers to a gap range of, for example, ~50 mm to ~300 mm or greater. An example application of large gap resonant WPTs is through-wall power transmission that does not require wired power connections for powering or charging small devices, such as communication equipment in 5G outdoor small cells and devices such as surveillance cameras, outdoor lighting, and sensing equipment. Through-wall applications typically require WPTs within the 200 mm to 300 mm range (i.e., the typical thickness of a building's exterior wall). As an example, a through-wall WPT system can provide power from an indoor power source to an outdoor unit (ODU) for, for example, power transmission in the range of tens to hundreds of watts without wiring. However, currently available WPT systems and resonator coil designs for WPTs suffer from problems such as low efficiency and poor thermal performance within this gap and power range.

[0007] For the design of a large-gap WPT system, several factors need to be considered, such as coil-to-coil efficiency between the transmitter coil (Tx coil) and the receiver coil (Rx coil), as well as the system end-to-end efficiency at the required power, while minimizing losses and acceptable thermal performance. For example, for coil-to-coil efficiency, it may be desirable to achieve maximum efficiency at a specified distance or gap between the Tx coil and the Rx coil.

[0008] Currently, commercially available Tx coils for the ~200mm gap range have low efficiency. These coils also tend to be optimized only for a specific gap distance between the Tx and Rx coils. That is, if the Rx coil is moved away from the designated charging plane, the efficiency drops rapidly with distance. Lower efficiency means greater losses, i.e., energy dissipated as heat, which can lead to overheating, i.e., exceeding the recommended operating temperature range.

[0009] For example, there is a need for improved resonator coils for WPT systems that provide at least one of the following: improved coil-to-coil efficiency, more efficient operation over an extended coil-to-coil gap range, higher power operation, improved thermal performance, or improvements in other performance factors. Summary of the Invention

[0010] The present invention seeks to provide a resonator coil for a large-gap WPT system that mitigates or avoids at least one of the aforementioned problems or at least provides an alternative.

[0011] A first aspect of the present invention provides a resonator coil for a large-gap resonant inductive wireless power transfer (WPT) system, comprising: a dielectric substrate; conductive traces patterned to define a coil topology including a plurality of n turns providing a specified inductance L; and a capacitor arrangement including: a first series tuning capacitor C2a and a second series tuning capacitor C2b in a first and a second feed line of the coil; a series matching capacitor C1 at the midpoint of the coil; and a parallel capacitor C3 connected at both ends of the feed line between the series tuning capacitors C2a and C2b and the turns of the coil.

[0012] The values ​​of capacitors C1, C2a, C2b, and C3 are chosen to provide a specified resonant frequency and input impedance. For example, when the resonator coil is the transmitter coil, the values ​​of capacitors C1, C2a, and C2b and C3 are chosen to optimize: the efficiency of the power amplifier in the WPT system; the coil-to-coil efficiency of the transmitter and receiver coils in the WPT system, and the end-to-end system efficiency; or to make the PA operate at or above the minimum required efficiency, or to maximize the efficiency of the PA.

[0013] The values ​​of capacitors C1, C2a, C2b, and C3 can be selected to reduce or optimize the input reflection coefficient S1 or to obtain the optimal operating efficiency point of the power amplifier (PA) in the WPT system. For example, if the resonator coil has a first input impedance Z with only C2a and C2b... TX 1 and a second input impedance Z with C1, C2a and C2b and C3 TX 2. Choose the value of the capacitor so that Z TX 2>Z TX 1. To reduce or minimize the input reflection coefficient S11, or to maximize the efficiency of PA.

[0014] In some embodiments, the coil has a coil region A, and each turn has a turn dimension including a conductive trace length, width, and turn spacing; the turn dimension is configured to provide a planar spacing distance D from the coil. gap The variance of the vertical magnetic field distribution on the target region of the charging plane is less than the reference variance; wherein the reference variance is defined as the variance of the vertical magnetic field distribution on the target region of the charging plane at a plane spacing Dgap from the reference coil of the corresponding coil region A, the reference coil having a reference coil topology with n turns including trace width and uniform turn spacing.

[0015] Another aspect of the present invention provides a resonator coil topology for a large-gap resonant inductive wireless power transfer (WPT) system, the topology comprising: a coil in coil region A comprising a plurality of n turns, each turn having a turn dimension including conductive trace length, width, and turn spacing; the turn dimension being configured to provide a planar spacing distance D from the coil. gap The variance of the vertical magnetic field distribution on the target region of the charging plane, wherein the variance is less than the reference variance; wherein the reference variance is defined as the variance at a planar distance D from the reference coil of the corresponding coil region A. gap The variance of the vertical magnetic field distribution on the target region of the charging plane, the reference coil having a reference coil topology with n turns including uniform trace width and turn spacing; and at least one turn having a different turn size than the reference coil.

[0016] Another aspect of the present invention provides a resonator coil for a large-gap resonant inductive wireless power transfer (WPT) system, comprising: a dielectric substrate; conductive traces patterned to define a coil topology including a plurality of n turns on a coil region A; each turn having a turn dimension including a conductive trace length, a width, and a turn spacing; the turn dimensions being configured to provide a planar spacing distance D from the coil. gap The variance of the vertical magnetic field distribution on the target region of the charging plane, wherein the variance is less than the reference variance; wherein the reference variance is defined as the variance at a planar distance D from the reference coil of the corresponding coil region A. gapThe variance of the vertical magnetic field distribution on the target region of the charging plane, wherein the reference coil has a reference coil topology with n turns including uniform trace width and turn spacing.

[0017] For example, the turn size of at least one turn is configured to provide a coil topology different from that of a reference coil topology, or the turn size of at least one turn is configured to provide a coil topology including at least one of non-uniform trace width and non-uniform turn spacing; or the turn size of each turn is individually configured to provide a coil topology including at least one of non-uniform trace width and non-uniform turn spacing. The turn size of each turn can be individually configured to reduce or minimize the variance. In some embodiments, the variance is ≤15%, for example, the variance is a relative standard deviation of ≤15%.

[0018] For example, the resonator coil can be configured for D in the range of 50mm to 500mm. gap For some applications, such as through-wall WPT, D gap It can be within a range of ~200mm, for example 200mm ± 10%, and the power of through-wall WPT ranges from tens of watts to at least hundreds of watts.

[0019] In one embodiment, a resonator coil for a large-gap resonant inductive wireless power transfer (WPT) system includes: a dielectric substrate; conductive traces patterned to define a coil topology comprising a plurality of n turns on a coil region A; each turn having a turn dimension including a conductive trace length, width, and turn spacing; the turn dimensions are non-uniform and configured to provide a planar spacing distance D from the coil. gap The variance of the vertical magnetic field distribution on the target region of the charging plane is ≤15%. The resonator coil includes a capacitor arrangement comprising: a first series tuning capacitor C2a and a second series tuning capacitor C2b in the first and second feed lines of the coil; a series matching capacitor C1 at the midpoint of the coil; and a parallel capacitor C3 connected at both ends of the feed lines between the series tuning capacitors C2a and C2b and the turns of the coil. The resonator coil topology can be optimized to have a reduced magnetic field variance relative to the turns of a generally square or rectangular reference coil with rounded corners.

[0020] Another aspect of the present invention provides a transmitter (Tx) for a resonant inductive wireless power transfer (WPT) system, comprising a power amplifier (PA) and a Tx resonator coil; wherein the Tx resonator coil includes a dielectric substrate and conductive traces patterned to define a coil topology with a specified inductance L, and at least one of the following: a) a capacitor arrangement comprising: a first series tuning capacitor C2a and a second series tuning capacitor C2b in a first and a second feed line of the coil; a series matching capacitor C1 at the midpoint of the coil; and a parallel capacitor C3 connected at both ends of the feed line between the series tuning capacitors C2a and C2b and between the turns of the coil; wherein the values ​​of capacitors C1, C2a, C2b and C3 provide a specified resonant frequency and input impedance for the PA to operate at a desired (or maximum) efficiency of the PA; and b) a resonator coil topology comprising a coil region A comprising a plurality of n turns, each turn having a turn dimension including a conductive trace length, width and turn spacing; the turn dimensions being configured to provide a planar spacing distance D from the coil. gap The variance of the vertical magnetic field distribution on the target region of the charging plane, wherein the variance is less than the reference variance; wherein the reference variance is defined as the variance at a planar distance D from the reference coil of the corresponding coil region A. gap The variance of the vertical magnetic field distribution on the target region of the charging plane, wherein the reference coil has a reference coil topology with n turns including uniform trace width and turn spacing.

[0021] For example, the capacitor arrangement is tuned to operate the PA at its maximum efficiency point, or, for example, to operate the PA with an efficiency of ≥90%, and the variance is ≤15%. The transmitter can be configured for through-wall WPTs, for example, with a gap distance D in the range of 50 mm to 500 mm. gap Through-wall power transfer (WPT) systems with a power range from tens of watts to at least hundreds of watts are available. The power amplifier (PA) can be implemented using GaN transistors and can operate with an efficiency of ≥90%.

[0022] A resonant inductive wireless power transfer (WPT) system includes a power amplifier (PA) as disclosed herein and a Tx resonator coil, wherein the Rx resonator coil may have the same coil topology as the Tx resonator coil.

[0023] A design method is disclosed, including methods for configuring coil topology and capacitor arrangement, for example, to obtain optimal efficiency.

[0024] In an embodiment, the method for configuring the resonator coil includes: obtaining the total parameters (a1, b1, ... a1). n ,b n ) initialThese parameters define the initial coil topology to be optimized (e.g., the reference coil topology), and the total number of parameters (a1, b1, ... a) n ,b n ) initial This includes: maximum coil size per turn (e.g., side length of a rectangular coil, diameter of a circular coil), number of turns, minimum spacing between turns, minimum trace width, etc.; obtaining target specifications, including: selecting the gap distance D from the coil to the charging surface. gap Select the area relative to the coil region. coil The charging area of ​​the charging surface charging Select the quality factor (FOM), which is determined by the distance D from the coil. gap The charging area on the charging surface charging The vertical magnetic field distribution Hz (e.g., variance) is derived from the initial parameters of the population (a1, b1, ... a). n ,b n ) initial Calculate the vertical magnetic field distribution Hz on the charging plane; calculate the FOM based on the fitness function F(Hz) on the region of the charging plane; and systematically change the total number of parameters, and for multiple total numbers of m parameters (a1, b1, ..., a... n ,b n ) m For each (where m = 2 to m = M), calculate the Hz on the charging plane and calculate the fitness function F(Hz)m on the charging plane; when the m-th parameter population (a1, b1 ... a n ,b n ) m When the fitness function F(Hz) satisfies the target specification, store the m-th parameter population (a1, b1, ..., a). n ,b n ) m As the overall target parameters; the output is the set of parameters (a1, b1, ..., a) corresponding to the target value of the fitness function F(Hz). n ,b n ) m To define a coil topology that meets the target specification, the coil topology includes the dimensions, trace width, and spacing of each of the n turns.

[0025] For example, FOM is the planar spacing distance D from the coil. gap The variance of the vertical magnetic field distribution in the target area of ​​the charging plane is Hz, and the target specification includes the minimum value of the variance.

[0026] In an embodiment, the method of configuring the capacitor arrangement includes: selecting a value for C1 such that the inductance L of C1 and the Tx coil resonates at a desired frequency; setting C2a and C2b to be equal and having a value of C2a = C2b = 2 * C1; using the Rx coil, tuning the value of C3 to a target specification, such as the optimal efficiency point of the power amplifier (PA) of the transmitter; measuring the S11 parameter (i.e., the input reflection coefficient); and tuning C3 and C2a, C2b such that the Tx coil resonates at the desired frequency, such that the Tx impedance ZTx operates within the range of efficiency from the minimum desired efficiency to the maximum efficiency of the PA.

[0027] Therefore, resonator coils for large-gap WPT systems, resonator coil design methods, and high-efficiency transmitters for large-gap WPTs, such as through-wall WPTs, are disclosed. Attached Figure Description

[0028] Figure 1 A simplified schematic diagram of an example resonant inductive WPT system is shown;

[0029] Figure 2 A schematic diagram of the resonant inductive coupling between the Tx coil and the Rx coil is shown;

[0030] Figure 3 The equivalent circuit of the WPT system of the embodiment is shown;

[0031] Figure 4 (Prior Art) shows (A) an example of a multi-turn coil for wireless charging; (B) a simplified equivalent circuit model of a wireless charging coil; and (C) a power amplifier with a multi-turn coil L0 and a capacitor CS and resonant operation.

[0032] Figure 5 (Prior Art) shows (A) a schematic diagram of a WPT system including a Tx resonator coil and an Rx resonator coil; (B) a simplified equivalent system model; and (C) the calculation of the Rx power of Tx in the equivalent circuit.

[0033] Figure 6 A circuit diagram of an embodiment of the WPT system is shown, which includes a Tx resonator coil having an arrangement of tuning capacitors and network matching capacitors to improve efficiency;

[0034] Figure 7 A circuit diagram of a WPT system is shown, which includes a Tx resonator coil with a conventional arrangement of series-tuned capacitors;

[0035] Figure 8 A simplified flowchart is shown to illustrate the determination. Figure 7 The method for synthesizing the capacitor value of the resonator coil in the illustrated embodiment;

[0036] Figure 9 (A) A schematic diagram of the resonator coil structure of a large-gap WPT system with a first example embodiment is shown; (B) A simplified equivalent circuit for impedance matching; (C) A photograph of the resonator coil of the first embodiment implemented using PCB technology to show the coil topology and location of the tuning capacitor and network matching capacitors C1, C2a, C2b and C3.

[0037] Figure 10 (A) A circuit diagram of the resonator coil structure of the large-gap WPT system of the second example embodiment is shown; (B) A simplified equivalent circuit for impedance matching; (C) A photograph of the resonator coil of the second embodiment, showing the coil topology and the positions of the matching capacitor C1 and the tuning capacitors C2a and C2b.

[0038] Figure 11 A flowchart is shown for determining the matching capacitor value and the tuning capacitor value (capacitor value synthesis) to meet the target performance specifications;

[0039] Figure 12 (Prior art) A schematic diagram is shown to illustrate the geometric parameters of a conventional planar square loop coil with conductive traces of uniform width and spacing;

[0040] Figure 13 (Prior art) is shown by... Figure 12 A schematic diagram of modeling a planar coil as a wire and calculating the magnetic field B(x,y,z) using the Biot-Savart law by integrating over an infinitesimal length dl.

[0041] Figure 14 (Prior art) is a schematic diagram showing a simplified Biot-Savart law to calculate the magnetic field B(x,y,z) of a planar coil modeled as a wire by summing over a small length Δl.

[0042] Figure 15A and Figure 15B A schematic diagram is shown illustrating coil topology synthesis based on an embodiment of an arbitrary initial coil topology (reference coil topology), wherein the coil topology is optimized to meet target specifications, such as optimization at a distance D from the Tx resonant coil plane. gap The uniformity of the z-component Hz of the magnetic field on the charging plane;

[0043] Figure 16 A schematic diagram illustrating an example of an initial coil topology for configuring the planar resonator coils of an example embodiment is shown;

[0044] Figure 17This is a simplified flowchart illustrating a resonator coil synthesis method based on an optimized factor of quality (FOM) according to an embodiment. In this example, the FOM includes elements at a distance D from the plane of the Tx resonator coil. gap Magnetic field B on the charging plane region z The standard deviation;

[0045] Figure 18 This is a CAD drawing showing the dimensions of the resonator coil in a first example embodiment, the dimensions of which are designed to optimize H on the region of the desired charging plane. z The variance of the magnetic field is shown to meet the target specification, and the positions and values ​​of tuning capacitors C2a and C2b and network matching capacitor C1 are also shown.

[0046] Figure 19A A schematic diagram of the resonator coil topology of the second example embodiment is shown;

[0047] Figure 19B The calculation is shown Figure 19A A three-dimensional curve of the simulated H-field of the coil's FOM;

[0048] Figure 20A A schematic diagram of the resonator coil topology of the second example embodiment is shown;

[0049] Figure 20B The calculation is shown Figure 20A A three-dimensional curve of the simulated H-field of the coil's FOM;

[0050] Figure 20C Showing the target Figure 20A Two-dimensional curves of the magnetic field distribution simulation in the target area for the gap distances Dgap of the coil at 50mm, 100mm and 150mm.

[0051] Figure 20D It shows the operation during Figure 20A The thermal diagram of the coil;

[0052] Figure 21 It is a flowchart illustrating a method for resonator coil synthesis based on an optimized embodiment of the factor of quality (FOM);

[0053] Figure 22 This is a flowchart illustrating a method for resonator coil synthesis based on another embodiment of quality factor (FOM) optimization;

[0054] Figure 23ASimulation results are shown for the Tx impedance (input reflection coefficient) of a resonator coil in an example embodiment including a tuning capacitor and matching capacitors C1, C2a, C2b and C3, and b) a resonator coil in a conventional arrangement including tuning capacitors C2a and C2b.

[0055] Figure 23B Simulation results for the peak Tx impedance of a resonator coil in an example embodiment including a tuning capacitor and matching capacitors C1, C2a, C2b and C3 are shown, as well as simulation results for a resonator coil in a conventional arrangement including tuning capacitors C2a and C2b.

[0056] Figure 23C Simulation results are shown for the Rx impedance (output reflection coefficient) of a resonator coil in an example embodiment including a tuning capacitor and matching capacitors C1, C2a, C2b and C3, and b) a resonator coil in a conventional arrangement including tuning capacitors C2a and C2b.

[0057] Figure 23D Simulation results are shown for a) a resonator coil of an example embodiment including tuning capacitors and matching capacitors C1, C2a, C2b, and C3, and b) a resonator coil with a conventional arrangement including tuning capacitors C2a and C2b, showing coil losses (efficiencies); and

[0058] Figure 24A and Figure 24B Sample data of measured coil-to-coil efficiency and end-to-end system efficiency are shown for an example of a large-gap WPT transmission system at 50W output power.

[0059] The foregoing and other features, aspects and advantages of the present invention will become more apparent from the following detailed description of embodiments of the invention taken in conjunction with the accompanying drawings, which are merely examples. Detailed Implementation

[0060] Figure 1 An example of a resonant inductive wireless power transfer (WPT) system is schematically illustrated. In this WPT system, the source or transmitter (Tx) comprises an RF source in the form of a power amplifier (PA), an impedance matching network, and a Tx resonator coil. The PA drives the system and is modeled as an ideal constant current source. The receiver comprises an Rx resonator coil, an impedance matching network, and a rectifier (e.g., a diode bridge). The device being charged or powered is represented by a load. The diode bridge is used to rectify the input RF signal into a DC signal, thereby powering the device or charging a battery, for example. Figure 2 The diagram schematically illustrates the magnetic field that provides resonant inductive coupling between the Tx and Rx coils. Figure 3 The equivalent circuit of an example resonant WPT system used in an embodiment of the present invention is shown.

[0061] The Tx and Rx coils are important subsystems. For example, based on the AirFuel resonant specification, these coils (also called resonators) are required to exhibit certain performance characteristics. However, the current AirFuel resonant specification is limited to a WPT with a maximum gap of 50mm and a maximum power of 70W. Therefore, resonator coils designed to meet the current AirFuel performance characteristics are not optimized for larger gap WPTs (e.g., for through-wall WPTs). For larger gaps (e.g., 100mm, 200mm, or larger), the mutual coupling between the Tx and Rx coils is low, and improved coil design is needed to improve coil-to-coil efficiency, thereby enabling higher power wireless transmissions, such as hundreds of watts, over larger gaps.

[0062] Flat planar resonator coils can be manufactured using conventional PCB techniques; for example, the number of turns of the coil is formed by conductive copper traces on or within a dielectric substrate. For planar coils, the dominant magnetic field component is along the z-direction perpendicular to the coil plane (i.e., H). z H z Field uniformity in the charging region is important for balancing power dissipation (i.e., maintaining a low operating temperature). This H z The field component depends on the coil design or topology (i.e., the number and distribution of coil turns) and the specified distance or gap D between the Tx coil and the Rx coil. gap Planar resonator coil designs with conventional topologies (e.g., multiple rectangular or square turns with uniform trace width and spacing between turns) produce highly non-uniform magnetic field distributions because the destructive and constructive fields generated by each turn accumulate in a non-optimal form, resulting in high Q and large field variations. For WPT over large gaps (such as through-wall transmission), the coupling between the Tx and Rx coils is weak, leading to low efficiency in systems using known coil designs.

[0063] The need for improved or optimized resonator coil topology, and the provision of solutions for higher power, large-gap WPTs that provide a more uniform magnetic field distribution, offering improved efficiency for large-gap WPT systems with weak coupling between the Tx and Rx resonator coils.

[0064] A coil design method is proposed for configuring a Tx resonator coil topology to improve the uniformity of the magnetic field distribution and enhance efficiency to meet target performance specifications. To improve efficiency, the Tx resonator coil of an example embodiment includes a capacitor arrangement comprising tuning capacitors and network matching capacitors. The values ​​of the tuning capacitors and network matching capacitors are selected to provide improved efficiency, such as an increase in coil-to-coil and system end-to-end efficiency. The capacitor values ​​used to improve efficiency can be synthesized and applied to resonator coils with arbitrary coil topologies. To mitigate the detrimental effects of large magnetic field variations, the design method provides a coil topology in which the dimensions of each turn of the coil are individually configured to minimize or at least reduce magnetic field variations on a desired plane (e.g., a region of the charging plane at a specified distance from the plane of the Tx coil). An example embodiment of a resonator coil is disclosed, wherein the coil topology is configured to provide a magnetic field distribution to meet target specifications, such as minimizing magnetic field variations in a region of the charging plane, and wherein the arrangement of tuning capacitor and matching capacitor values ​​is selected to increase efficiency.

[0065] Capacitor value synthesis for improving efficiency

[0066] Consider the following example where the Tx and Rx resonator coils are designed to operate at their resonant frequency (e.g., 6.78 MHz or 13.56 MHz). The equivalent input impedance will be the coil's DC resistance. Figure 4 shows (A) an example of a multi-turn wireless coil; (B) a simplified equivalent circuit; and (C) resonant operation using a power amplifier, multi-turn coil L0, and tuning capacitor Cs. Figure 5 shows (A) a schematic diagram of the mutual coupling between the Tx and Rx coils in a WPT system; and (B) a simplified circuit model of the wireless charging coil and power amplifier load impedance at the output of the PA in a WPT system. The series capacitor C1 is the resonant capacitance of the multi-turn coil; L1 represents the total inductance of the multi-turn coil, and R represents the effective series resistance, which is a combination of the coil's radiation resistance and ohmic resistance (Z). 2 21 / RL). When the coil operates at the resonant frequency, the equivalent reactance and power of the resonant LC circuit shown in Figure 5(B) can be described by the following formula in Figure 5(C).

[0067] For a large-gap WPT system, the mutual coupling between the Tx coil and the Rx coil is Z. 21 Very low, typically less than 0.1. The equivalent impedance R in the PA output. TXVery low. For example, for a 4-turn 270mm coil, the DC resistance is approximately 1 ohm and the inductance is approximately 10μH. For weakly mutually coupled Rx loads, the equivalent impedance in the Tx PA output can be tuned to approximately 10 ohms at the resonant frequency. Peak efficiency is approximately 80%. The PA cannot operate at maximum efficiency for this input impedance range.

[0068] exist Figure 6 The diagram schematically illustrates a WPT system configured to optimize the efficiency of both the Tx and Rx coils. The inductance L of the Tx resonator coil is L1 + L2, and includes a first series tuning capacitor C2a and a second series tuning capacitor C2b located at the input port of the coil, a series matching capacitor C1 located at the center of the coil (i.e., between L1 and L2), and a parallel capacitor C3 serving as a network matching capacitor. For comparison, Figure 7 A conventional arrangement or resonator coil with series tuning capacitors C2a and C2b is shown. Appropriate selection of the values ​​of tuning capacitors C2a and C2b, along with network matching capacitors C1 and C3, provides increased coil-to-coil efficiency and system end-to-end efficiency. That is, the resonator coil includes matching capacitors C1 and C3 to tune the input impedance of the Tx coil to a range that improves or optimizes PA efficiency.

[0069] Figure 8 An example embodiment is shown (e.g.) Figure 6 The diagram shows a simplified flowchart of a method for optimizing capacitor values ​​(for example, a resonant frequency of 6.78 MHz). Initially, the value of C1 is selected so that C1 and the inductance L of the Tx coil resonate at the desired frequency (step 8-1). That is, as shown... Figure 6 As shown, L = L1 + L2. Initially, C2a and C2b are set to be equal, with the value C2a = C2b = 2 * C1 (step 8-2). Then, the value of C3 is tuned using the Rx coil to obtain the optimal efficiency point of the transmitter's power amplifier (PA) (step 8-3). The S11 parameter (i.e., the input reflection coefficient) is measured. S11 depends on the input impedance Z of the Tx coil. Tx Then, C3, C2a, and C2b are tuned so that the Tx coil resonates at the desired frequency of 6.78MHz, and the Tx impedance Z is adjusted. Tx Within the maximum efficiency range of PA, and minimizing S11 (8-4). If necessary, the latter two steps can be repeated by fine-tuning C3 and C2a, C2b until the best-matched elements are obtained to achieve the highest efficiency (8-5).

[0070] Figure 9(C) shows a photograph of the resonator coil of the first example embodiment. In this embodiment, the coil is manufactured using PCT technology and includes 4 turns, i.e., 4 rectangular turns with rounded corners, these turns being made of Figure 9 (C) shows the copper traces embedded in the black area of ​​the PCB. Figure 9 The equivalent circuit of the resonator coil design in (C) is shown in Figure 9 In (A), with Figure 6 The same as shown. The impedance matching formula is shown in Figure 9 In (B), the dimensions of each coil turn are individually optimized to minimize the variation of the z-component Hz of the magnetic field in the desired region of the charging plane (e.g., 200 mm from the coil plane). The actual locations of matching capacitors C1 and C3 and the locations of tuning capacitors C2a and C2b are shown in [the diagram]. Figure 9 In (C), tuning capacitors C2a and C2b are series capacitors at each feed port (input port) of the coil. Matching capacitor C1 is a series capacitor placed at the center (midpoint) of the coil. Another matching capacitor C3 is a parallel capacitor connected at both ends of the feed line between the series tuning capacitors C2a and C2b and the coil turns.

[0071] The coil design of the second example embodiment is shown in Figure 10 (C). The design of the equivalent circuit is shown in [C]. Figure 10 In (A), the impedance matching formula is shown in... Figure 10 (B) in. For example... Figure 10 As shown in (C), the coil topology comprises eight non-uniform turns. The dimensions of each coil turn are optimized to ensure that the z-component H of the magnetic field in the desired region of the charging plane (e.g., 200 mm from the coil plane) is... z The changes are minimized. The positions of the matching capacitor C1, tuning capacitors C2a and C2b are shown in... Figure 10 (C) In this example, C3 is omitted. For example, see reference Figure 8 As explained in the flowchart, by combining capacitor values ​​to determine the required values ​​for C1, C2a, and C2b, and for C3, it can be determined that C3 has a very small value. In this case, C3 can be omitted because adding C3 will have little effect on efficiency.

[0072] More generally, methods for synthesizing capacitor values ​​involve selecting capacitor values ​​C1, C2a, C2b, and C3 to meet desired performance targets (e.g., target efficiency), thereby optimizing, for example, coil-to-coil efficiency and end-to-end efficiency of the WPT system. Figure 11 The flowchart shown is a schematic representation.

[0073] Coil topology synthesis for improving magnetic field distribution uniformity

[0074] An example of a planar coil with a conventional topology (e.g., having rectangular or square turns, with uniform trace width and uniform spacing between turns) is schematically shown in... Figure 12 Including, for example Figure 12 The WPT system with the conventional square resonator coil configuration shown (with uniform trace width and spacing) is described in the article by SH Lee et al. (Energies 2019, 12, page 271). Figure 13 As illustrated, the Biot-Savart law can be used to calculate the magnetic field B(x,y,z) of an arbitrary coil containing a wire by integrating the field over an infinitesimally small length dl. This simple coil topology (with multiple rectangular turns, each with uniform trace width and spacing) produces a highly non-uniform magnetic field distribution because the destructive and constructive fields generated by each turn accumulate in a non-optimal form, resulting in high Q and large field variations.

[0075] Reference Figure 3 The equivalent circuit shown shows that the mutual inductance between the Tx resonator coil and the Rx resonator coil is related to the magnetic field, according to the following formula:

[0076]

[0077] V Rx =ωMI Tx =Z 21 I Tx (2)

[0078]

[0079] Where H Z It is caused by the current I in the Tx coil Tx The generated magnetic field in the z-direction, parameter N Rx and A Rx These are the number of turns and the cross-sectional area of ​​the Rx coil, respectively. From formulas (1) and (2), it is clear that the input current I... Tx and the output voltage V on the receiver coil Rx The relationship between the magnetic field and the voltage at the receiver side is as follows. A large change in the magnetic field will result in a large change in the voltage at the receiver side. This voltage change may cause the operating temperature to exceed the safe range in certain regions. In a perfectly series-tuned resonant system, the load applied to the PA is related to the mutual inductance M by equation (3). Therefore, a large change in the mutual inductance results in a large load R applied to the power amplifier (PA). load Corresponding changes.

[0080] To mitigate the detrimental effects of large magnetic field variations, an optimized Tx resonator coil design method is now described. First, this design method provides optimization of the coil topology, wherein the dimensions of each coil turn are configured to minimize or at least reduce magnetic field variations on the desired plane (e.g., a region of the charging plane at a specified distance from the Tx coil plane). This optimization of the coil topology to meet target specifications (e.g., improved magnetic field uniformity) enables other sub-blocks of the WPT system to operate more robustly. Second, the capacitor arrangement and the values ​​of the tuning capacitors and network matching capacitors are selected to increase efficiency, as described earlier in the section on the synthesis of capacitor values ​​for increasing efficiency.

[0081] The fundamental principle of the proposed coil design method is to optimize the size and distribution of each coil turn to achieve improved or optimized magnetic field uniformity, for example, to meet desired target specifications. This design method includes a systematic coil synthesis procedure based on the H... z The component-derived factor of quality (FOM) provides a unique combination of dimensions per turn to achieve optimal field distribution, thereby meeting the target specifications required for wireless charging applications. For example, the FOM can be based on the variance in the charging plane, such as H... z Standard deviation (std H) z Target specifications may include, for example, the maximum size of the Tx coil, transmit and receive power requirements, and the clearance distance D from the plane of the Tx coil to the charging plane. gap The required dimensions of the Rx coil or the area of ​​the charging plane, etc. For the resulting coil topology, the design method then includes a capacitor value synthesis procedure to select the values ​​of the tuning capacitor and network matching capacitor to maximize efficiency, or at least provide target efficiencies for the required Rx and Tx power and gap distance, such as coil-to-coil efficiency or other parameters.

[0082] Example of coil synthesis

[0083] Define the FOM, for example, at a distance D from the surface of the Tx coil. gap The magnetic field H in the z-direction on a specified region of the charging plane at that location z The target variance, such as the maximum variance. An arbitrary initial coil topology (which can be called the reference coil topology), for example... Figure 15A The diagram illustrates the process, and then an optimization process is performed to systematically change the coil parameters to meet target specifications, such as the target variance or minimum variance of the magnetic field in a specified region of the charging plane (Hz), to provide an optimized coil topology, such as... Figure 15B As shown schematically. (For example) Figure 15B As illustrated in the diagram, the resulting coil topology can have a non-uniform turn distribution, where each turn has a unique configuration of trace width and spacing between traces.

[0084] As Figure 13 schematically shown, the Biot - Savart law can be used to find the magnetic field produced by any current - filament structure. The Biot - Savart law uses an integral formula to find the magnetic field at an observation point by summing the fields caused by infinitesimal parts that make up the entire structure, where l is the current through an infinitesimal length dl, and is a vector pointing from dl to the observation point (x0, y0, z0). It is assumed that the current through all the spiral loops is constant. To convert the integral formula into a form more suitable for computer calculations, the structure is divided into small elements or segments of finite length Δl instead of infinitesimal segments, so that the integral is converted into a sum as Figure 14 shown, where r n is the vector pointing from the center of the Δl segment to the observation point P, as Figure 14 schematically shown.

[0085] The coil topology synthesis program starts with the selection of any initial coil topology (e.g., an n - turn planar spiral coil in the form of a rectangle or square with rounded corners, as Figure 15A schematically shown), and obtains an initial set or ensemble of parameters that define the initial coil topology, i.e., a set of geometric parameters that define the dimensions of each element Δl of the coil, so that the magnetic field can be calculated based on the Biot - Savart sum. For example, as Figure 15A schematically shown, for a coil of n concentric generally rectangular turns with rounded corners, where the length of the nth turn is an and bn, and initial values are chosen to start the optimization as follows:

[0086] a1 and b1 are the lengths of the largest (outer) turn;

[0087] a1 and b1 are chosen to provide a coil of the desired external dimensions, e.g., <275 mm square;

[0088] a n < a n-1 ... < a1 and b n < b n-1 ... < b1;

[0089] For example, for a resonator coil with four turns n = 4, as Figure 15A shown, the smallest (inner) turn has lengths a4 and b4.

[0090] A minimum distance, d space = trace width + trace spacing, is set between the turns. For example, d space ≥10 mm provides a minimum of, for example, 5 mm trace width and 5 mm spacing between the traces, so initially a n < a n-1 +11 mm and b n < bn-1 +11mm.

[0091] Using this initial arbitrary coil topology, we obtain (a1, b1, ... a) coils including the defined coil topology. n ,b n ) initial The initial parameters are the total. In this simple example, the initial parameters are the values ​​of each turn in n turns (a n ,b n ) initial The set. Of course, for more complex coil topologies, in addition to limiting (a) per turn... n ,b n In addition to (a1, b1, ... x1, ... a), more parameters may be needed (e.g., (a1, b1, ... x1, ... a n ,b n ....x n To define each turn, for example, to consider optimizing the rounded corners of each turn relative to the straight portion of each turn (a n ,b n The dimensions of the coil topology. An initial set of parameters defining the coil topology serves as the starting point for coil topology optimization to meet the target specification. The target specification is selected, including the FOM (Form Oscillator). For example, the FOM is defined as a distance D from the surface of the Tx coil. gap Magnetic field H in the z-direction of a charging plane region (e.g., 200 mm) z The minimum variance. For example, the area of ​​the charging plane can be defined as the area surrounded by a specific percentage (e.g., 30%) of the outer dimension of the coil.

[0092] Using the initial parameter set (a1, b1, ... a) for a defined initial coil topology n ,b n ) initial The Biot-Savart summation is used to calculate the z-component of the magnetic field on the charging plane region and to evaluate the uniformity of the z-component of the magnetic field on the charging plane or other selected planar regions. For example, the uniformity on the planar region is evaluated based on the relative standard deviation to provide a value for the cost or fitness function c. Then, the initial parameter population (a1, b1, ..., a) is used. n ,,b n initial or (a1, b1, ... a n ,b n ) m＝1 Systematically change to a second population (a1, b1, ..., a n ,,b n ) m＝2 Calculate H for multiple points P on a plane. z And evaluate H on the planar region zThe uniformity. For each subsequent parameter population m(a1,b1,....a) from m=3 to M. n ,,b n ) m Repeat this process to find the optimal H. z The overall parameters of field uniformity. H z Field uniformity can be, for example, satisfying the target specification H in a region of the charging plane. z The optimal or minimum value of the relative standard deviation. The total number of parameters (a1, b1, ..., a) for the objective or optimization. n ,,b n ) targe t defines the coil topology that meets the target specification, for example, Figure 15B The diagram illustrates an n-turn coil with non-uniform trace width and spacing. The output parameter set is then used, for example, as a parameter set from a CAD design tool specifying an optimized coil topology. The target or optimized parameter set (a1, b1, ..., a...) n ,,b n ) target Limit the size of the device for manufacturing coils, for example, using PCB technology, where coil turns are patterned or printed as one or more layers of conductive copper traces on / in a single or multi-layer dielectric substrate.

[0093] In an example Tx resonator design, the structure includes a helical coil with square turns and rounded corners to form a helix with n = 4 turns, 27 cm wide and 27 cm long. The initial topology is based on, respectively, as follows: Figure 15A The a shown n Width and b n A spiral of 4 concentric squares of length, a n and b n These are the optimal variables, and for four turns there will be six variables because a1 and b1 are both constants equal to 27cm, representing the length and width of the spiral circumference. The minimum distance between turns is, for example, 10mm, to ensure a minimum of 5mm trace and 5mm spacing space. Additionally, the width and length of each turn should be greater than the next smaller turn, i.e., a n >a n-1 And b n >b n-1 .

[0094] In a larger field change (i.e., a large Z), 21 In the event of changes, the I provided by PA Tx The very limited range will satisfy the voltage regulator's allowed voltage range. This will result in an unstable system that cannot be optimized through the system's feedback loop.

[0095] in The optimization problem of the unit vector in the z direction is

[0096] where: 0 < a n < 27 cm, 0 < b n < 27 cm

[0097] z o = 100 mm, 0 < x o < 15 cm, 0 < y o < 15 cm

[0098] Linear constraint: a n > a n-1 + 11 mm, b n > b n-1 + 11 mm

[0099] In the resonator coil of this embodiment, a genetic algorithm is used to solve the optimization problem, as Figure 17 schematically shown in the simplified flowchart of. The optimization process starts with any set of a n and b n , for example, for each turn in n turns (a n , b n )initial(15 - 1), and continues for each of multiple m populations of (a n , b n ). The criterion for stopping the optimization is the change in the cost function. If the change in the cost function < c, that is, less than the target value (15 - 4). Then at this time, the set values of a n and b n are the best results for achieving uniformity (15 - 5), otherwise the values of a n and b n are changed (15 - 6), and then the process is repeated again.

[0100] Using Figure 17 the algorithm represented by the simplified flowchart, the coil topology of the exemplary embodiment is obtained, including the dimensions shown in the CAD drawing such as Figure 18 , including 4 turns, each turn having specific different (i.e., non-uniform) turn dimensions and turn spacings. Figure 18 The positions and values of the tuning capacitors C2a and C2b (each 360 pF) and the matching capacitor C1 (180 pF) are also shown.

[0101] In Figure 19A the coil topology of another exemplary embodiment is shown. The simulated Hz field of this coil topology is as Figure 19B shown. In this example, the FOM (defined by the percentage standard deviation of the z - component of the field) is 15% over 50% of the coil region in the 100 - mm - high observation plane.

[0102] Figure 20A Another example embodiment of the coil design is shown. The calculated Hz field is... Figure 20B As shown in the image. Figure 20C Two-dimensional graphs of the magnetic field distribution in planes at heights of 50 mm, 100 mm, and 150 mm above the coil plane are shown. Figure 20D A thermal simulation of the coil in operation is shown.

[0103] A flowchart of the method steps for coil synthesis, including other example embodiments, is in Figure 21 and Figure 22 As shown in the image. Figure 17 The method shown in the simplified flowchart is applicable to, for example, Figure 16 The coil topology shown is such that each turn is an approximately rectangular shape with rounded corners, and each turn n can be simply determined by size a. n and b n The FOM is defined as being at a distance D from the plane of the Tx coil. gap B on the planar region z or H z The standard deviation. (From) Figure 21 The flowchart representation method is applicable to the following topologies, where each turn n is represented by a set of parameters a. n and b n Limited, and FOM is from B z The derived fitness function or other function is constrained, and this fitness function can be, for example, B. z The variance is used to assess whether the target specification is met. Figure 22 The flowchart representation method is more generally applicable to arbitrary coil topologies, where each turn n is determined by an extended parameter or a set of parameters (e.g., a for each turn). n ,b n ...x n (This is because) limitations, for example, for coils with complex geometries, require the use of numerous parameters to define the geometry of each turn. Figure 21 and Figure 22 In the method schematically illustrated in the flowchart, after optimizing the coil topology, i.e., defining the coil size to meet the desired target specifications, capacitor values ​​are then selected for tuning and impedance matching. Capacitor value synthesis has been described in detail above.

[0104] The output of coil topology synthesis can be a set of parameters (a1, b1, ... a n ,,b n ) target These parameter sets define the dimensions of each turn in the n turns, such as coil topology specifications used for output to a CAD system. For example, Figure 18This is a CAD drawing showing the dimensions and spacing of the conductive traces per turn of the coil in a defined prototype embodiment, configured for fabrication using standard PCB techniques, such as... Figure 9 The photograph of the prototype shown in (C) illustrates this. Each turn has a unique size and spacing configured to optimize magnetic field variations over the desired area of ​​the charging plane. Therefore, unlike conventional coil topologies with turns having uniform trace width and spacing, this coil topology is defined by coil parameters, in which dimensions such as the trace width and spacing of each individual turn are configured to optimize the factor of quality (FOM), for example, at a specified distance or distance range D from the coil. gap Magnetic field H on the charging plane region z The standard deviation of the z-component. The capacitor arrangement is configured for impedance and network matching to improve efficiency.

[0105] Following the coil topology synthesis and capacitor synthesis procedures, the proposed coil design is analyzed using a three-dimensional electromagnetic field simulation tool, such as ANSYS HFSS (High Frequency Structure Simulator), to verify the design.

[0106] It has been shown that adding a network matching series capacitor C1 at the center (midpoint) of the coil, and, if necessary, adding a network matching parallel capacitor C3 with an appropriate value, increases the efficiency of coil-to-coil energy transfer and increases the system's end-to-end efficiency.

[0107] A key characteristic of this type of coil design is its high efficiency with low mutual coupling and a large gap between the Tx and Rx coils. This characteristic allows for effective resonant WPT over larger gaps (e.g., 100mm to 300mm or more) and for a wider range of power transfers (e.g., from several hundred watts to one kilowatt). For example, these ranges far exceed current AirFuel specifications (e.g., 6.78MHz, a maximum gap of 50mm, and power transfer further limited to 70W).

[0108] Figure 23A , Figure 23B , Figure 23C and Figure 23D Some sample data of the coil topology of the example prototype embodiment are shown, wherein the tuning and network matching capacitors include, for example Figure 6 The capacitor values ​​C1, C2a, C2b, and C3 shown are used for, for example... Figure 7 The data shown are for the same coil topology capacitors with only the conventional capacitor arrangement including tuning capacitors C2a and C2b.

[0109] Figure 23A The simulated Tx impedance at the resonant frequency is shown; Figure 23B The simulated peak Tx impedance is shown; Figure 23CThe simulated Rx impedance at the resonant frequency is shown; Figure 23D The simulated losses (efficiencies) are shown. As these sample data demonstrate, the Tx impedance increases from 11 ohms with a conventional tuned capacitor arrangement to 32 ohms in the example embodiment, which includes network matching capacitors C1 (in series) and C3 (in parallel). Figure 23A The peak Tx impedance increased from 11 ohms in the conventional arrangement to 45 ohms in the example embodiment. Figure 23B The Rx impedance is reduced from 12 ohms in the conventional arrangement to 9.4 ohms in the example embodiment. Figure 23C Therefore, by increasing the Tx impedance and decreasing the Rx impedance, the loss is reduced from 3.2 dB in the conventional arrangement to 0.7 dB in the example embodiment, an improvement of 2.5 dB. That is, the coil-to-coil efficiency at the resonant frequency is significantly improved by increasing the Tx impedance and providing a significantly higher peak Tx impedance at the resonant frequency, thereby reducing the S11 (input reflection coefficient or input return loss) at the resonant frequency.

[0110] The optimized coil topology of the example embodiment can be manufactured using conventional PCB techniques, such as copper traces on a dielectric substrate. Using PCB technology to implement the coil topology is advantageous because it allows for very tight control over process variations and optimization of parameters per turn of the coil. Furthermore, since PCB technology is a very mature technology, it is suitable for high-volume production and easy to integrate with other components. Another advantage is the ability to achieve a lower z-height. In the example prototype design, the total thickness of the PCB coil board is 0.8 mm compared to a conventional Airfuel coil with a thickness of 4.2 mm.

[0111] Figure 24A and Figure 24B Some measurement data are provided for an example of a WPT system, which includes a 50W PA (GaN Systems technology), a Tx coil, and an Rx coil (configured as follows). Figure 9 (The same coil shown in the photograph in (C)) is designed to improve the uniformity of the magnetic field (Hz) over the charging plane region and has an output load impedance of 30 ohms and an output power of 50W with a gap of 200mm. The measured coil-to-coil peak efficiency is 93%, and the system end-to-end (E2E) efficiency is 75%.

[0112] Typically, PCB coils exhibit high resistance due to dielectric loss and small trace thickness. To address this issue, the prototype coil was constructed by connecting three identical PCB metal layers in parallel using vias. The coil includes fewer turns, resulting in a shorter coil length than conventional coil designs. This PCB manufacturing technique allows for the design of coils with lower losses. The low resistance of the Tx coil also contributes to improved efficiency.

[0113] Some example coil topologies of specific embodiments are described only by way of example. It is clear that specific design parameters for the Tx or Rx coil will depend on the target specifications of the specific customer and application, as well as the FOM selected for optimization. When the FOM is at a distance D from the plane of the Tx coil... gap When considering the variance of the magnetic field over a specified region of the charging plane, it may be desirable to optimize the Form of Memory (FOM) by finding coil parameters that minimize this selected variance (e.g., the relative standard deviation of the magnetic field Bz over the charging plane). In other cases, it may be sufficient to terminate the optimization process when the variance meets the target specification. Example embodiments are presented that enable more efficient WPT for gaps in the ~200 mm range, such as for through-wall WPTs. This design approach can also be used to optimize the Hz field of coil designs configured for charging over a wider gap range (e.g., 200 mm ± 20 mm), i.e., providing improved efficiency and reduced losses when the Rx coil is moved away from the main charging plane.

[0114] Choosing the FOM (Form-of-Means) optimizes efficiency over large gaps, i.e., meeting target specifications and preferably maximizing efficiency, such as reducing losses and improving thermal performance. For example, during prototyping, it has been shown that >90% coil-to-coil efficiency can be achieved for a 200mm gap, while close to 90% efficiency can be achieved for a 300mm gap. Appropriate selection of capacitors for impedance matching and tuning also contributes to increased system efficiency, for example, by matching the input impedance to allow the power amplifier to operate within its maximum efficiency range. The design methodology is applicable, for example, to power ranges from tens to hundreds of watts, such as 40W to >500W or higher, such as 1 kilowatt, for example, with coil dimensions (i.e., maximum external dimensions) and gap distances (Dgap) ranging from ~100mm to ~500mm. Advantageously, genetic algorithms can be used in the FOM optimization process. Other types of optimization algorithms may be applicable.

[0115] Although embodiments of the invention have been described and illustrated in detail, it should be clearly understood that the embodiments are by way of illustration and example only, and not by way of limitation, and the scope of the invention is limited only by the appended claims.

Claims

1. A method for configuring a resonator coil, comprising: acquiring parameters (a1, b1,.... a n , b n ) initial which define an initial coil topology to be optimized, Parameters (a1, b1,.... a n , b n ) initial include: maximum coil size per turn, number of turns, minimum spacing between turns, minimum trace width; Obtain the target specifications, including: Selecting the gap distance D from the coil to the charging surface gap ; selecting a charging area Area coil relative to a coil area Area charging ; A figure of merit FOM is selected, which is derived from the vertical magnetic field distribution Hz over the charging area Area of the charging surface at a gap distance D gap from the coil charging ; a) for the initial parameter set (a1, b1,.... a n , b n ) initial , calculate the vertical magnetic field distribution Hz on the charging plane; b) Fitness function F(H) on the region based on the charging plane z To calculate FOM; and c) Systematically change the overall parameters, and for multiple populations of m parameters (a1, b1... a... n , b n ) m For each m = 2 to m = M, calculate H on the charging plane. z And calculate the fitness function F(H) on the charging plane. z )m; d) When the m-th parameter is in the overall population (a1, b1... a) n , b n ) m fitness function F(H) z When the value of ) satisfies the target specification, store the m-th parameter population (a1, b1, ... a) n , b n ) m As the overall target parameter; e) Output and fitness function F(H) z The parameter set (a1, b1... a) corresponding to the target value. n , b n ) m To define a coil topology that meets the target specification, the coil topology includes the dimensions, trace width, and spacing of each of the n turns.

2. The method according to claim 1, wherein, FOM is the vertical magnetic field distribution H in the target region of the charging plane at a planar spacing distance Dgap from the coil. z The variance.

3. The method according to claim 2, wherein, The target specification includes the minimum value of the variance.

Images