Planar Coupler Design Method Based on Electromagnetic Force Analysis Model

Abstract

A planar coupler design method based on an electromagnetic force analysis model includes the following steps: determining the planar coupler design specifications and parameters according to the application scenario of wireless power transmission in a microgravity environment; establishing a planar coupler model based on electromagnetic force analysis according to the initial parameters; calculating the mutual inductance value and the corresponding number of coil turns in the initial design parameters of the planar coupler; adjusting the initial number of coil turns and the corresponding operating frequency; and adjusting the distance between the planar coupler core and the coil. This invention establishes an electromagnetic force model of the planar coupler regarding its performance parameters, fully utilizing the structural information of the planar coupler; adjusting the number of coil turns and the operating frequency reduces the electromagnetic force of the planar coupler while maintaining the same wireless power transmission power; and adjusting the distance between the planar coil and the core effectively reduces the electromagnetic force and further improves the coupler stability.

Description

Technical Field

[0001] This invention belongs to the field of electrical technology, and more specifically relates to a planar electromagnetic coupler design method based on an electromagnetic force analysis model within the field of wireless power transfer device technology. This invention is applicable to low-electromagnetic-force wireless power couplers in spacecraft wireless power transfer systems operating in microgravity environments. Background Technology

[0002] Currently, coil model design based on the mutual inductance coupling method has been widely applied in the design of wireless power transmission systems using planar couplers. The mutual inductance coupling method analyzes the influence of planar coupler component parameters on the self-inductance, mutual inductance, and coupling coefficient of the planar coupler coil, as well as the influence of the planar coupler impedance on the current, voltage, and power of the connected circuit. Based on this, optimal component parameter design and impedance matching are performed to obtain the planar coupler design parameters with the best wireless power transmission efficiency, thereby ensuring the performance of the wireless power transmission system. However, when the planar coupler operates at high frequency and high power, the design of the coil model using the mutual inductance coupling method with direct numerical solution suffers from problems such as inaccurate calculation of distributed parameters, difficulty in assessing electromagnetic environment safety standards for the planar coupler, electromagnetic interference to electronic equipment in the surrounding environment, and the stability of the planar coupler structure itself. In contrast, the mutual inductance coupling method using electromagnetic field simulation analysis for coil model design has a more accurate calculation mechanism for the high-frequency distributed parameters of the planar coupler and makes it easier to simulate the electromagnetic environment of the planar coupler. This design scheme can intuitively reveal the working mechanism of the magnetic shielding material and magnetic core material in the electromagnetic field of the planar coupler structure, and calculate the influence of the planar coupler component parameters on the electromagnetic force under high-power wireless power transmission. This design method is more suitable for high-power wireless power transmission in spacecraft than planar coupler designs that only consider transmission efficiency. Currently, this design method still has problems in the analysis and design of planar couplers: On the one hand, existing wireless power transmission technologies are mainly aimed at ground applications, and the research on electromagnetic forces in planar couplers mainly focuses on the Newton (N) level electromagnetic forces in the electric vehicle field under high-power conditions. Further research is needed on planar couplers with millinewton (mN) level and smaller electromagnetic forces in spacecraft applications under microgravity environments. On the other hand, the electromagnetic force generated by the planar coupler in the microgravity environment of spacecraft will cause the transceiver coil to gradually deviate from the center position, leading to the functional failure of the device.

[0003] Xian Zhang, Xuejing Ni, and others proposed a planar coupler design method considering electromagnetic forces in their paper "Research on the Influence of Structural Parameters on Electromagnetic Force of Wireless Power Transfer" (IEEE 2nd International Electrical and Energy Conference (CIEEC), 2018). This method introduces the component parameters of the planar coupler under design and establishes a numerical calculation model of the electromagnetic force of the planar coupler. It reduces the electromagnetic force generated by the planar coupler by optimizing parameters such as permeability, number of coil turns, and coil turn spacing. However, this method still has shortcomings. This design scheme improves the electromagnetic force generated between planar couplers by adjusting the component parameters of the planar coupler coils. Analysis using the mutual inductance coupling method shows that the number of coil turns is proportional to the mutual inductance value, and analysis of the planar coupler matching circuit topology shows that the mutual inductance value is proportional to the output power. Therefore, when the target transmission power of the planar coupler is limited to a specific numerical range, this design scheme cannot guarantee the system's transmission power.

[0004] Xian Zhang, Fengxian Wang, and others, in their paper "Structure Electromagnetic Force Analysis of WPT System Under Fault Conditions" (IEEE Access, 2020), proposed a planar coupled coil design method based on the Snopt algorithm, which reduces the impact of Newton (N) level pulse forces between planar couplers on the operating performance of the planar coupler. This method introduces the turn spacing of the planar coupler coil under design as a design parameter, establishes an electromagnetic field mathematical model of the planar coupler under design, and optimizes the turn spacing of the planar coupler coil under design using the Snopt algorithm. When the receiver is in an open-circuit state, the electromagnetic force generated by the optimized planar coupler is significantly reduced compared to that generated by the unoptimized planar coupler. Although the above design scheme has obtained the influence mechanism of the component parameters and materials of the planar coupler to be designed on the electromagnetic force, and analyzed and designed a planar coupler to reduce the electromagnetic force, the method still has shortcomings. The design scheme studies the influence of design parameters such as the conductivity and permeability of the magnetic shielding material, the number of coil turns and the turn spacing of the planar coupler to be designed on the electromagnetic force. When the electromagnetic force of the planar coupler is limited to the millinewton (mN) level, the calculation process of the design scheme model is lengthened and the efficiency is low. Furthermore, it cannot guarantee the positional displacement of the planar coupler caused by the electromagnetic force under microgravity environment. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of the prior art by proposing a planar electromagnetic coupler design method based on an electromagnetic force analysis model. This method aims to solve the problems of existing coil model designs based on mutual inductance coupling, which are difficult to evaluate the influence of electromagnetic forces on planar couplers under microgravity conditions and cannot meet the design requirements of planar couplers with electromagnetic forces limited to the millinewton (mN) level and smaller under microgravity conditions, resulting in low operational safety and efficiency of the designed planar couplers.

[0006] The technical approach of this invention is as follows: First, this invention performs force analysis on the planar coupler and establishes an electromagnetic force analysis model for the planar coupler based on initial design parameters. This solves the problem of excessive electromagnetic force caused by incomplete parameter consideration during the design process of the planar coupler. Based on the electromagnetic force analysis model, this invention uses the ratio relationship between different numbers of turns and operating angular frequencies of the planar coupler under the same transmission power to calculate the number of turns and its corresponding operating frequency after adjustment based on the initial design parameters. By adjusting the number of turns and operating frequency of the planar coupler based on the initial design parameters, the electromagnetic force corresponding to the current parameters is calculated, and it is determined whether the performance parameter design index is met. This method avoids the need to separately traverse the number of turns and operating frequency for the design of planar couplers with low electromagnetic force, thus improving the design efficiency of planar couplers. Based on the electromagnetic force analysis model, this invention, after the number of turns and operating frequency of the planar coupler have been designed, adjusts the distance between the coil and the magnetic core to reduce the magnetic lines of force passing through the magnetic core in the horizontal direction and calculates the electromagnetic force and transmission power corresponding to the distance between the coil and the magnetic core to obtain the design value that meets the performance parameter design index. This solves the problems of high time cost and low accuracy in the existing method of selecting magnetic core permeability.

[0007] The specific steps of this invention are as follows:

[0008] Step 1: Based on the application scenario of the planar coupler, determine the transmission performance design specifications and initial design parameters of the planar coupler with symmetrical structure;

[0009] Step 2, establish the electromagnetic force model of the planar coupler with respect to the initial design parameters of the planar coupler as follows:

[0010]

[0011] Where F represents the initial design parameter model of the electromagnetic force of the planar coupler, ρ represents the correction factor of the magnetic core for the magnetic flux of the planar coupler (the fitted value obtained from electromagnetic simulation), 1≤ρ≤2, and μ0 represents the free permeability of the magnetic core in the planar coupler structure, μ0=4π×10 -7π represents pi, X represents the number of turns of the primary and secondary coils in the initial design parameters of the planar coupler, I1 represents the input current of the primary coil of the planar coupler, I2 represents the current generated by the secondary coil of the planar coupler, R represents the radius of the primary and secondary coils of the planar coupler, θ represents the angle between the direction of the magnetic field and the direction of the current in the secondary coil of the planar coupler, d0 represents the distance between the primary and secondary coils of the planar coupler, and D(j) represents the electromagnetic force on the core of the planar coupler when the distance between the core and the coil is l in the initial design parameters of the planar coupler.

[0012] Step 3: Calculate the mutual inductance value of the initial design parameters of the planar coupler;

[0013] Step 4: Solve for the number of coil turns in the initial design parameters of the planar coupler;

[0014] Step 5, adjust the initial number of turns of the coil and its corresponding operating frequency:

[0015] Step 5.1: Within the turn count range [1, X1] in the initial design parameters of the planar coupler, select an unselected number of turns and adjust the initial turn counts of the primary and secondary coils of the planar coupler using the following formula:

[0016]

[0017] Among them, f i X represents the operating frequency corresponding to the number of coil turns after the i-th adjustment, τ1 represents the nonlinear variable introduced by the magnetic core, τ1∈[0,1], X i This represents the number of coil turns after the i-th adjustment;

[0018] Step 5.2: Calculate the transmission power corresponding to the coil turns adjustment;

[0019] Step 5.3: Determine whether the parameters corresponding to the currently adjusted number of coil turns meet the following constraints. If all constraints are met, proceed to step 6; otherwise, proceed to step 5.1.

[0020]

[0021] in, X represents the number of coil turns after the i-th adjustment. i With operating angular frequency The corresponding electromagnetic force model, F max P represents the maximum allowable electromagnetic force in the electromagnetic force design specifications of the planar coupler. out1 P represents the transmission power corresponding to the number of coil turns after the i-th adjustment. out0 P represents the transmission power in the initial design parameters of the planar coupler. out This indicates the minimum transmission power allowed by the planar coupler's transmission power design specifications.

[0022] Step 6, adjust the distance between the planar coupler core and the coil:

[0023] Step 6.1, calculate the operating angular frequency of the planar coupler. At that time, the mutual inductance value corresponding to the minimum allowable transmission power in the transmission power design specifications of the planar coupler;

[0024] Step 6.2: Within the range of coil-core spacing parameters in the initial design parameters of the planar coupler, select an unselected coil-core spacing.

[0025] Step 6.3: Determine whether the adjusted distance between the coil and the magnetic core meets the following constraints. If all constraints are met, proceed to step 7; otherwise, proceed to step 6.2.

[0026]

[0027] Wherein, F(j) m () represents the distance j between the magnetic core and the coil after the m-th adjustment of the planar coupler. m The corresponding electromagnetic force model, M out2 (j m M represents the mutual inductance value corresponding to the distance between the magnetic core and the coil after the m-th adjustment. min This represents the mutual inductance value corresponding to the minimum transmission power of the planar coupler;

[0028] Step 7: Complete the design of the planar coupler.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] First, this invention establishes a model of the electromagnetic force of a planar coupler with respect to the performance parameters of the planar coupler, which includes structural parameters such as the number of turns, input current, transmission distance, and the distance between the magnetic core and the coil. When designing a planar coupler, this invention overcomes the problem in the prior art that only considers transmission power or transmission efficiency, which leads to excessive electromagnetic force between planar couplers, causing structural damage and positional displacement of the planar coupler. This invention improves the stability of the planar coupler in microgravity environments.

[0031] Secondly, this invention adjusts the number of turns and operating frequency of the planar coupler by using the equation relationship between the turns ratio and the operating angular frequency ratio of different planar couplers under the same transmission power. This reduces the electromagnetic force of the planar coupler while ensuring that the output power remains constant. Furthermore, it utilizes the adjustability of the spacing between the magnetic core and the coil of the planar coupler to adjust the structure of the planar coupler. This overcomes the problem of large fluctuations in the output power and low electromagnetic force design accuracy of the planar coupler when using electromagnetic field simulation analysis based on mutual inductance coupling model to optimize the magnetic permeability, number of coil turns, and coil turn spacing of the planar coupler. This invention effectively reduces the electromagnetic force and alleviates the damage to the magnetic core caused by collisions between coils. Attached Figure Description

[0032] Figure 1 This is a flowchart of the present invention;

[0033] Figure 2 This is an analysis diagram of the electromagnetic force of the present invention;

[0034] Figure 3 This is a topology diagram of the resonant circuit of the present invention;

[0035] Figure 4 This is a diagram showing the electromagnetic force results of adjusting the distance between the magnetic core and the coil according to the present invention;

[0036] Figure 5 This is a comparison diagram showing the vertical offset of the primary side of the planar coupler relative to the secondary side before and after the adjustment of the distance between the coil and the magnetic core in this invention;

[0037] Figure 6 This is a comparison diagram showing the horizontal offset of the primary side relative to the secondary side of the planar coupler before and after the adjustment of the distance between the coil and the magnetic core in this invention. Detailed Implementation

[0038] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0039] Reference Figure 1 The implementation steps of the embodiments of the present invention will be further described below.

[0040] Step 1: Determine the transmission performance design parameters for the symmetrical planar coupler.

[0041] In the embodiments of the present invention, based on the application scenario of the planar coupler in a spacecraft under microgravity, the transmission performance design indicators of the symmetrical planar coupler are determined, as shown in Table 1.

[0042] Table 1. Design Specifications for Transmission Performance of Planar Couplers

[0043] Planar Coupler Transmission Performance Design Specifications numerical values <![CDATA[Transmission power P out > 500W~10kW Electromagnetic force F 10μH~20mN Operating frequency band f 30kHz-500kHz

[0044] Considering the actual size of the planar coupler, the initial design parameters of the planar coupler are set as shown in Table 2.

[0045] Table 2 Initial Design Parameters for Planar Couplers

[0046] Design parameters numerical values Planar coupler outer diameter r 200mm The distance j between the primary coil (or secondary coil) and the magnetic core 0≤j≤30mm The primary and secondary coil turn spacing s 1mm The wire diameters w of the primary and secondary coils 1mm <![CDATA[Distance d0 between the primary side and the secondary side]]> 30mm <![CDATA[Primary side coil input current I1]]> 10A <![CDATA[Transmission power P out0 > 1kW

[0047] Step 2: The planar coupler consists of primary and secondary planar magnetic cores and primary and secondary coils, with the primary and secondary sides installed parallel to each other, such as... Figure 2 As shown in the diagram. Here, dFx represents the radial electromagnetic force at point A of the secondary coil of the planar coupler, dFz represents the axial electromagnetic force at point A of the secondary coil of the planar coupler, F represents the resultant electromagnetic force at point A of the secondary coil of the planar coupler, θ represents the angle between the resultant electromagnetic force of the planar coupler and the radial direction, I1 represents the input current of the primary coil of the planar coupler, I2 represents the current generated by the secondary coil of the planar coupler, R represents the radius of the primary and secondary coils of the planar coupler, d0 represents the distance between the primary and secondary coils of the planar coupler, and j represents the distance between the primary and secondary coils and the magnetic core.

[0048] According to Biot's theorem, the magnetic field strength produced by the primary coil at point A of the secondary coil is as follows:

[0049]

[0050] Where μ0 represents the free permeability of the magnetic core in the planar coupler structure, μ0 = 4π × 10⁻⁶ -7 π represents the mathematical constant Pi, and X represents the equivalent number of turns of the primary and secondary coils in the initial design parameters of the planar coupler. Considering the edge effect of the magnetic field distribution, B has a vertical axis bias. Simplifying the influence of the magnetic core on the magnetic field of the secondary coil, the electromagnetic force on the secondary coil at point A is analyzed as follows:

[0051]

[0052] Considering the electromagnetic force acting on the magnetic core, the electromagnetic force model of the planar coupler with respect to the initial design parameters of the planar coupler is established as follows:

[0053]

[0054] Where F represents the initial design parameter model of electromagnetic force of planar coupler, ρ represents the correction factor of magnetic core on magnetic flux of planar coupler (fitted value obtained from electromagnetic simulation), 1≤ρ≤2, and D(j) represents the electromagnetic force on magnetic core of planar coupler when the distance between magnetic core and coil is j in the initial design parameters of planar coupler.

[0055] In this embodiment of the invention, ρ = 1.45, I1 = 10A, R = 100mm, d0 = 30mm, and the heat dissipation between the coil and the magnetic core is taken as j = 2mm. Substituting these values ​​into the above formula, the electromagnetic force of the planar coupler in this embodiment of the invention with respect to the initial design parameters of the planar coupler is as follows:

[0056]

[0057] Step 3: Specify the planar coupler topology as an SS-shaped matching topology, as shown in the figure. Figure 3 As shown. Where U1 represents the primary input voltage of the planar coupler, R... S I1 represents the input resistance of the primary side of the planar coupler, I2 represents the input current of the primary coil of the planar coupler, C1 and C2 represent the resonant capacitances of the primary and secondary sides of the planar coupler resonant network, R1 and R2 represent the equivalent resistances of the primary and secondary coils of the planar coupler, L1 and L2 represent the self-inductances of the primary and secondary coils of the planar coupler, and M represents the mutual inductance of the planar coupler. L The load value at the output of the secondary coil of the planar coupler is represented by the following value: The mutual inductance value of the initial design parameters of the planar coupler is calculated as follows:

[0058]

[0059] Where M1 represents the mutual inductance value in the initial design parameters of the planar coupler, and R2 represents the resistance value of the secondary coil of the planar coupler. This represents the operating angular frequency in the initial design parameters of the planar coupler. f1 represents the operating frequency in the initial design parameters of the planar coupler, P out0 I represents the transmission power in the initial design parameters of the planar coupler, and I1 represents the primary input current of the planar coupler.

[0060] In this embodiment of the invention, R2 can be ignored, R L =50Ω, take f1=30kHz, I1 = 10A, P out0 =1kW, substituting into the above formula, we get M1 =118μH;

[0061] Step 4: Use the following formula to solve for the number of coil turns in the initial design parameters of the planar coupler under tight coupling:

[0062]

[0063] Where L1 represents the self-inductance value in the initial design parameters of the primary and secondary coils of the planar coupler, the unit of L1 is μH, L1 = M1, r represents the outer diameter of the primary and secondary coils of the planar coupler, and D i Let X1 represent the inner diameters of the primary and secondary coils of the planar coupler, X1 represent the initial number of turns of the primary and secondary coils of the planar coupler obtained from the solution, w represent the wire diameters of the primary and secondary coils of the planar coupler, and s represent the turn spacing between the primary and secondary coils of the planar coupler; r, D i The units for w and s are all inches.

[0064] In this embodiment of the invention, by substituting into the above formula, we obtain N1 = 26, and thus the initial value of the number of turns in the initial design parameters of the planar coupler is obtained. Since the actual working state of the planar coupler is loose coupling, L1 > M1 in actual operation. By adjusting the number of turns using software, we obtain that when N1 = 30, M1 = 118μH.

[0065] Step 5: Adjust the initial number of turns of the coil and its corresponding operating frequency.

[0066] Step 5.1: Select an unselected number of coil turns within the range [1,30] of the initial design parameters for the planar coupler.

[0067] The initial number of turns of the primary and secondary coils of the linear-planar coupler can be adjusted using the following formula:

[0068]

[0069] Among them, f i X represents the operating frequency corresponding to the number of coil turns after the i-th adjustment, τ1 represents the nonlinear variable introduced by the magnetic core, τ1∈[0,1], X i This represents the number of coil turns after the i-th adjustment.

[0070] In this embodiment of the invention, i = 2, select an unselected coil with a number of turns X2 = 7, take τ1 = 0.9, and substitute it into the above formula to obtain f2 = 500 kHz in this embodiment of the invention;

[0071] Step 5.2, use the following formula to calculate the transmission power corresponding to the coil turns adjustment:

[0072]

[0073] Among them, P out1 This represents the transmission power corresponding to the number of coil turns after the i-th adjustment. This represents the operating angular frequency corresponding to the number of coil turns after the i-th adjustment. M i This represents the mutual inductance value corresponding to the number of coil turns after the i-th adjustment.

[0074] In this embodiment of the invention, the internal resistance R of the planar coupler coil is... i If the resistance is much less than 50Ω, it can be ignored. Substitute it into the above formula to calculate the output power of the embodiment of the present invention.

[0075] Step 5.3: Determine whether the parameters corresponding to the currently adjusted number of coil turns meet the following constraints. If all constraints are met, proceed to step 6; otherwise, proceed to step 5.1:

[0076]

[0077] in, X represents the number of coil turns after the i-th adjustment. i With operating angular frequency The corresponding electromagnetic force model, F max P represents the maximum allowable electromagnetic force in the electromagnetic force design specifications of the planar coupler. out1 P represents the transmission power corresponding to the number of coil turns after the i-th adjustment. out0 This represents the transmission power in the initial design parameters of the planar coupler;

[0078] In this embodiment of the invention, the transmission power P corresponding to the number of coil turns after the second adjustment out0 =1kW, P out0 =1kW, and calculated The conditions described in the embodiments of the present invention in the above formula are satisfied. As shown in Table 3, the electromagnetic force before and after adjusting the number of turns of the planar coupler coil and the operating frequency is compared. The adjusted planar coupler reduces the electromagnetic force while maintaining the same power transmission capability.

[0079] Table 3 Comparison of performance parameters of planar coupler before and after adjustment of number of turns and operating frequency.

[0080] Number of turns / turns Frequency / kHz Electromagnetic force / mN Mutual inductance value / μH Maximum output power / W 30 30 450 118 1000 7 500 15 7 1000

[0081] Step 6: Adjust the distance between the planar coupler core and the coil.

[0082] Step 6.1, use the following formula to calculate the operating angular frequency of the planar coupler. At that time, the mutual inductance values ​​corresponding to the minimum allowable transmission power in the planar coupler transmission power design specifications are as follows:

[0083]

[0084] Among them, M min R1 represents the mutual inductance value corresponding to the minimum transmission power of the planar coupler, and R2 represents the resistance value of the secondary coil of the planar coupler.

[0085] In this embodiment of the invention, i = 2, R L =50Ω, P out =500W, I1=10A, substituting these values ​​into the above formula yields the embodiment of the present invention.

[0086] Step 6.2: Using the current planar coupler turns and operating frequency settings, adjust the core-coil spacing within the range of the coil-core spacing. Perform logarithmic fitting on the obtained data to correct the electromagnetic force model of the planar coupler. The resulting electromagnetic force model F(j) for the current planar coupler structure with respect to the core-coil spacing is as follows:

[0087] F(j) = 16.4 - 3.4ln(j)

[0088] Step 6.3: Within the range of coil-core spacing parameters in the initial design parameters of the planar coupler, select an unselected coil-core spacing.

[0089] Step 6.4: Determine whether the adjusted distance between the coil and the magnetic core meets the following constraint conditions. If all conditions are met, proceed to step 7; otherwise, proceed to step 6.2.

[0090]

[0091] Wherein, F(j) m () represents the distance j between the magnetic core and the coil after the m-th adjustment of the planar coupler. m The corresponding electromagnetic force model, M out2 (j m ) represents the mutual inductance value corresponding to the distance between the magnetic core and the coil after the m-th adjustment.

[0092] In this embodiment of the invention, based on the actual adjustment results of the magnetic core and the planar coupler coil, such as... Figure 4 As shown. Figure 4 The horizontal axis in the figure represents the distance between the magnetic core and the coil, in mm, and the vertical axis represents the electromagnetic force on the planar coupler. The number of turns of the planar coupler is determined to be X2 = 7, the distance between the magnetic core and the coil is j = 15 mm, the mutual inductance is M2 = 16 μH, and F = 2.5 mN, which satisfies the conditions shown in the above formula of the present invention embodiment.

[0093] Step 6.5: Determine whether the positional offset of the completed planar coupler meets the electromagnetic force limitation condition. If yes, proceed to step 7; otherwise, proceed to step 5.

[0094] In this embodiment of the invention, the planar coupler is set to X = 7, j = 2 mm, and f = 500 kHz before adjustment, and to X = 7, j = 15 mm, and f = 500 kHz after adjustment. Figure 5 , Figure 6 As shown. Figure 5The horizontal axis represents the vertical offset of the secondary coil of the planar coupler, in mm, and the vertical axis represents the electromagnetic force of the planar coupler, in millinewtons (mN). Figure 5 The curve marked with a circle represents the curve before the spacing between the coil and the magnetic core is adjusted; the curve marked with a square represents the curve after the spacing between the magnetic core and the coil is adjusted using existing technology. Figure 6 The horizontal axis represents the horizontal offset of the secondary coil of the planar coupler, in mm, and the vertical axis represents the electromagnetic force of the planar coupler, in millinewtons (mN). Figure 6 The curve marked with a circle represents the curve before the coil-core spacing was adjusted; the curve marked with a square represents the curve after adjusting the coil-core spacing using existing technology. By adjusting the horizontal and vertical offsets of the planar coupler, and observing the changes in the electromagnetic force of the planar coupler with positional offset before and after the coil-core spacing adjustment, it was concluded that the positional offset of the planar coupler after adjusting the coil-core spacing is more stable and meets the electromagnetic force constraint conditions.

[0095] Step 7: Complete the design of the planar coupler.

Claims

1. A planar coupler design method based on an electromagnetic force analysis model, characterized by, An electromagnetic force analysis model is established for the planar coupler, the initial number of turns of the coil and the corresponding working frequency are adjusted, and the distance between the magnetic core and the coil of the planar coupler is adjusted; the steps of the design method include the following: Step 1, according to the application scene of the planar coupler, the transmission performance design index of the symmetrical structure planar coupler and the initial design parameters of the planar coupler are determined; Step 2, the electromagnetic force of the planar coupler is established as follows: Wherein, F represents the initial design parameter model of the planar coupler electromagnetic force, p represents the correction factor of the magnetic core to the planar coupler magnetic flux (the fitting value obtained by electromagnetic simulation), 1≤p≤2, μ0 represents the vacuum permeability of the magnetic core in the planar coupler structure, μ0=4π×10 -7 , π represents the circular constant, X represents the turns of the primary coil and the secondary coil in the initial design parameters of the planar coupler, I1 represents the input current of the primary coil of the planar coupler, I2 represents the generated current of the secondary coil of the planar coupler, R represents the radius of the primary coil and the secondary coil of the planar coupler, θ represents the angle between the electromagnetic force of the planar coupler and the radial direction, d0 represents the distance between the primary coil and the secondary coil of the planar coupler, D(j) represents the electromagnetic force of the planar coupler magnetic core when the relative distance between the magnetic core and the coil is l in the initial design parameters of the planar coupler; Step 3, the mutual inductance value of the initial design parameters of the planar coupler is calculated; Step 4, the number of turns of the coil in the initial design parameters of the planar coupler is solved; Step 5, the initial number of turns of the coil and the corresponding working frequency are adjusted: Step 5.1, in the range of the number of turns of the coil in the initial design parameters of the planar coupler [1, X1], an unselected number of turns of the coil is selected, and the initial number of turns of the primary coil and the secondary coil of the planar coupler is adjusted by using the following formula: Wherein, f represents the working frequency corresponding to the coil turns after the i adjustment, τ1 represents the nonlinear variable introduced by the magnetic core, τ1∈[0, 1], X i represents the coil turns after the i adjustment; Step 5.2, the transmission power corresponding to the adjusted number of turns of the coil is calculated; Step 5.3, it is judged whether the parameters corresponding to the current adjusted number of turns of the coil satisfy the following limit conditions, if all the conditions are satisfied, step 6 is executed, otherwise, step 5.1 is executed; wherein, represents the number of turns of the coil after the i-th adjustment X i represents the working angular frequency corresponding to the electromagnetic force model, F max represents the maximum electromagnetic force allowed by the electromagnetic force design index of the planar coupler P out1 represents the transmission power corresponding to the number of turns of the coil after the i-th adjustment P out0 represents the transmission power in the initial design parameters of the planar coupler P out represents the minimum transmission power allowed by the transmission power design index of the planar coupler; Step 6, the distance between the magnetic core and the coil of the planar coupler is adjusted: Step 6.1, the working angular frequency of the planar coupler is calculated as When the working angular frequency of the planar coupler is 2.5 GHz, the mutual inductance value corresponding to the minimum transmission power allowed in the design index of the transmission power of the planar coupler; Step 6.2, in the range of the distance between the coil and the magnetic core in the initial design parameters of the planar coupler, an unselected distance between the coil and the magnetic core is selected; Step 6.3, it is judged whether the adjusted distance between the coil and the magnetic core satisfies the following limit condition, if all the conditions are satisfied, step 7 is executed, otherwise, step 6.2 is executed; Wherein, F(j) m () represents the distance j between the magnetic core and the coil after the m-th adjustment of the planar coupler. m The corresponding electromagnetic force model, M out2 (j m M represents the mutual inductance value corresponding to the distance between the magnetic core and the coil after the m-th adjustment. min This represents the mutual inductance value corresponding to the minimum transmission power of the planar coupler; Step 7, the design of the planar coupler is completed.

2. The planar coupler design method based on an electromagnetic force analysis model according to claim 1, wherein, The transmission performance design index of the planar coupler in step 1 includes: transmission power range, electromagnetic force range, working frequency band.

3. The planar coupler design method based on an electromagnetic force analysis model according to claim 1, wherein, The initial design parameters of the planar coupler in step 1 include: planar coupler size, planar coupler primary and secondary coil wire diameter, planar coupler primary and secondary distance, planar coupler coil turn distance, coil and magnetic core distance, planar coupler primary coil input current, planar coupler transmission power.

4. The planar coupler design method based on an electromagnetic force analysis model according to claim 1, wherein, The mutual inductance value of the initial design parameters of the planar coupler in step 3 is obtained by the following formula: wherein M1 represents a mutual inductance value in initial design parameters of the planar coupler, R2 represents a resistance value of the secondary coil of the planar coupler, R L represents a load value of an output terminal of the secondary coil of the planar coupler, represents an operating angular frequency in the initial design parameters of the planar coupler, f1 represents an operating frequency in the initial design parameters of the planar coupler.

5. The planar coupler design method based on an electromagnetic force analysis model according to claim 1, wherein, The number of turns of the coil in the initial design parameters of the planar coupler in step 4 is obtained by the following formula: Wherein, L1 represents the self-inductance value in the initial design parameters of the primary and secondary coils of the planar coupler, L1 is in units of μH, L1=M1, r represents the outer diameter value of the primary and secondary coils of the planar coupler, D i represents the inner diameter value of the primary and secondary coils of the planar coupler, w represents the wire diameter value of the primary and secondary coils of the planar coupler, and s represents the turn spacing value of the primary and secondary coils of the planar coupling coil; r, D i , w, and s are all in units of inch.

6. The planar coupler design method based on an electromagnetic force analysis model according to claim 4, wherein The transmission power corresponding to the adjusted number of turns of the coil in step 5.2 is obtained by the following formula: wherein, represents the operating angular frequency corresponding to the number of turns of the coil after the i-th adjustment, M i represents the mutual inductance value corresponding to the number of turns of the coil after the i-th adjustment, R i represents the coil resistance value after the i-th adjustment.

7. The planar coupler design method based on an electromagnetic force analysis model according to claim 4, wherein The mutual inductance value corresponding to the minimum transmission power in step 6.1 is obtained by the following formula: Wherein, R2 represents the resistance value of the secondary coil of the planar coupler.

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