Magnetic field shielding structure of surrounding type fan-shaped coil

Abstract

The invention provides a magnetic field shielding structure of a surrounding type fan-shaped coil, which comprises a transmitting coil, a surrounding type fan-shaped magnetic field shielding coil and a receiving coil, and belongs to the technical field of wireless power transmission. In order to solve the problems that a magnetic field shielding structure of existing small electronic equipment is large in occupied space volume and poor in leakage magnetic field shielding performance in a specific area, peripheral magnetic field shielding in a specific angle area is achieved through a reactive shielding mode of the surrounding type fan-shaped shielding coil magnetic coupling mechanism, meanwhile, the structure is small in occupied space volume, and the shielding performance is good. And the central angle of the fan-shaped coil can be adjusted according to different shielding areas to realize accurate shielding. According to the magnetic field shielding structure, the flexibility of the shielding structure of the wireless charging system of the small electronic device can be improved, and electromagnetic radiation to the surrounding environment and human tissues can be effectively reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wireless power transmission, and particularly relates to a magnetic field shielding structure of a ring-shaped sector coil. TECHNICAL BACKGROUND

[0002] Wireless power transmission (WPT) technology is used for non-contact power supply, which is a transmission mode for transmitting electric energy from a power supply end to a power consumption device by means of a space intangible soft medium (such as an electric field, a magnetic field, a sound wave, etc.). Compared with the traditional mode of transmitting electric energy by using a cable, this energy transmission mode is more secure, convenient and reliable in charging fields such as implantable medical devices, high-temperature and corrosive gas environments, and overcomes some shortcomings brought by wire power supply. Magnetic field coupling wireless power transmission (MCR-WPT) technology is the most important power transmission mode for small electronic device wireless charging due to its advantages of large transmission distance and high efficiency. Although the MCR-WPT technology can complete the transmission of electric energy in a non-contact manner, there is inevitably magnetic field energy leakage between the coils of the transmitting end and the receiving end due to the air gap, and the leakage magnetic field not only affects the transmission efficiency of the system, but also causes electromagnetic radiation safety problems to the surrounding environment and human tissues, so designing a reasonable shielding structure becomes a key problem to reduce the magnetic field strength of the leakage magnetic field.

[0003] In a small electronic device MCR-WPT system, the transmitting end transmits energy to the receiving end, which produces a leakage magnetic field. The generation of the leakage magnetic field can cause electromagnetic radiation to human organs, and when the magnetic field strength value of the leakage magnetic field is higher than the threshold value that can be tolerated by the human body, it will affect human health. Although there has been some progress in the research on shielding structures, there are still some problems. The method of active shielding coil is used in document [2] to reduce the magnetic field strength of the leakage magnetic field, but since an additional excitation source is needed, the use of space is greatly increased, which is not conducive to the integration of small electronic devices. The hybrid ring array mentioned in documents [3]-[5] uses two types of coils, i.e., an amplification coil and a shielding coil, and the array coil occupies a large space volume, which is not suitable for application scenarios of small electronic devices.

[0004] In 2021, Chinese invention patent CN202111231581.6 discloses an inductive WPT double-sided LCLC topology for shielding external peripheral magnetic field and its parameter design method. Although the proposed coil can meet the shielding effect in a certain area, the structure has defects, which is easy to produce sharp current and local magnetic field unevenness, and the shielding effect will be affected to a certain extent. The existing shielding device occupies a large space outside the transmitting coil, which cannot adapt to the application scene of implantable charging equipment. In 2024, Chinese invention patent CN202410322879.5 discloses a structure of a surrounding active shielding coil and a multi-objective optimization method thereof. By being connected in series with the original coil in reverse as the excitation source of the shielding coil, the space volume is large to a certain extent, and the system lacks flexibility.

[0005] [1] Luo Z, Nie S, Pathmanathan M, et al. Exciter-quadrature-repeater transmitter for wireless electric vehicle charging with high lateral misalignment tolerance and low EMF emission [J]. IEEE Transactions on Transportation Electrification, 2021, 7(4): 2156-2167.

[0006] [2] Campi T, Cruciani S, Maradei F, et al. Magnetic field mitigation by multicoil active shielding in electric vehicles equipped with wireless power charging system [J]. IEEE Transactions on Electromagnetic Compatibility, 2020, 62(4): 1398-1405.

[0007] [3] Lee S, Kim D H, Cho Y, et al. Low leakage electromagnetic field level and high efficiency using a novel hybrid loop-array design for wireless high power transfer system[J]. IEEE Transactions on Industrial Electronics, 2018, 66(6): 4356-4367.

[0008] [4] Rong C, Chen M, Duan X, et al. Optimized design of passive array coils for high-efficiency and anti-misalignment WPT system[J]. IEEE Transactions on Power Electronics, 2024, 39(5): 6504-6514.

[0009] [5] Chen W, Cao H, Yan X, et al. Research on Resonant Wireless Power Transfer with Hybrid Array Composite Shielding for Small Electronic Equipment[J]. International Journal of Circuit Theory and Applications, 2024. SUMMARY

[0010] In view of the problems that the existing small electronic equipment charging system has magnetic field leakage between transmission coils, which affects the surrounding environment and human body safety, the existing shielding structure is too large in volume and is not conducive to the integration of small electronic equipment, and the magnetic field shielding in a specific area cannot be realized, the present application provides a magnetic field shielding structure of a ring-shaped sector coil, by adding a sector coil shielding structure between the transmitting coil and the receiving coil, the problems of the original shielding device in the space volume utilization rate and the inability to shield the magnetic field in a specific angle area are improved, and the flexibility and safety of the small electronic equipment are improved.

[0011] In order to achieve the above technical problems, the technical scheme adopted by the present application is as follows:

[0012] According to the embodiment, a magnetic field shielding structure of a surrounding fan-shaped coil for a small electronic device charging system is provided, which comprises a transmitting coil L P , a receiving coil L S , a surrounding fan-shaped shielding coil L sh1 , L sh2 , L sh3 ……L shn .

[0013] According to an aspect of the embodiment, the transmitting coil and the receiving coil are circular planar spiral coils with consistent outer diameter, inner diameter and number of turns, and the size of the coil is set according to the change of the application scenario, and the transmission distance is set according to the actual application requirement.

[0014] According to an aspect of the embodiment, the outer diameter of the magnetic field shielding structure of the surrounding fan-shaped coil is greater than the radius of the transmitting coil, and the outer diameter is determined by the shielding effect of the peripheral magnetic field.

[0015] According to an aspect of the embodiment, the surrounding fan-shaped shielding coil is in multiple groups and is distributed in parallel above the transmitting coil.

[0016] According to an aspect of the embodiment, the surrounding fan-shaped shielding coil L sh1 , L sh2 , L sh3 ……L shn is kept at a certain distance from the transmitting coil, and the placement position of the fan-shaped shielding coil magnetic field shielding structure in the system is optimized by considering the shielding structure of the system transmission efficiency and the magnetic field shielding effect.

[0017] According to an aspect of the embodiment, the fan-shaped shielding coil can form a specific fan-shaped coil shielding structure by changing the central angle θ, and shield the specific area magnetic field.

[0018] According to an aspect of the embodiment, the current direction of the fan-shaped coil shielding structure is adjusted by an external matching capacitor, and the matching capacitor is adjusted by selecting a suitable system compensation circuit.

[0019] According to an aspect of the embodiment, the current direction of the fan-shaped shielding coil is adjusted by an external matching capacitor C sh , the inductive magnetic field of the transmitting coil is used as an excitation source, an induced current is generated by reactive resonance, the fan-shaped shielding coil realizes self-impedance dominated by inductance, the shielding coil and the transmitting coil are 180° phase angle, and then a reverse current is generated, and finally a reverse magnetic field is generated.

[0020] The advantages of the present application compared with the existing shielding device are as follows:

[0021] The shielding effect of the ring-shaped fan-shaped coil magnetic field shielding structure is improved while the space volume occupied by the shielding device is reduced, the shielding effect is improved through the superposition of the reverse magnetic field generated by multiple groups of fan-shaped shielding coils, the leakage magnetic field of the transmitting coil is offset in different directions, and when the leakage magnetic field of the system in a specific direction is shielded, the leakage magnetic field in any direction can be specifically shielded by adjusting the angle of the fan-shaped coil. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the specific embodiments or the prior art description will be briefly introduced below.

[0023] Figure 1 is a schematic diagram of a magnetic coupling type WPT system comprising the ring-shaped fan-shaped coil magnetic field shielding structure of the embodiment of the present application and the structure thereof;

[0024] Figure 2 is a structural schematic diagram of the fan-shaped shielding coil of the embodiment of the present application;

[0025] Figure 3 is a whole schematic diagram of a magnetic coupling type WPT system comprising the 120° ring-shaped fan-shaped coil magnetic field shielding structure and the structure thereof;

[0026] Figure 4 is a turn number and coupling coefficient change curve of a transmitting coil and a receiving coil in the magnetic coupling type WPT system of the embodiment of the present application; the system schematic diagram of the ring-shaped 120° fan-shaped coil magnetic field shielding structure of the embodiment of the present application;

[0027] Figure 5 is an equivalent circuit diagram of the magnetic coupling type WPT system comprising the ring-shaped 120° fan-shaped coil magnetic field shielding structure and the structure thereof in the embodiment of the present application;

[0028] Figure 6 is a schematic diagram of the ring-shaped 120° fan-shaped coil magnetic field shielding structure in the embodiment of the present application;

[0029] Figure 7 is an optimal diagram of the relative position of the 120° fan-shaped coil magnetic field shielding structure and the transmitting coil;

[0030] Figure 8 is a schematic diagram of the magnetic field shielding effect of the ring-shaped 120° fan-shaped coil magnetic field shielding structure acting on the magnetic coupling system in the embodiment of the present application;

[0031] Figure 9 is an XZ magnetic flux density mode comparison diagram of the main system and the ring-shaped 120° fan-shaped coil magnetic field shielding structure in the embodiment of the present application.

[0032] Figure 10is the magnetic field intensity variation curve of the magnetic field shielding structure of the surrounding 120° sector coil in the embodiment of the application at the receiving coil side of the multiple measurement points.

[0033] Figure 11 is the magnetic flux density mode diagram of the XY cross section in the receiving coil side of the magnetic field shielding structure of the surrounding 120° sector coil in the embodiment of the application in the single shielding 120° angle region. DETAILED DESCRIPTION

[0034] The embodiments of the technical solution of the application will be described in detail below with reference to the drawings. The following embodiments are used to more clearly illustrate the specific implementation steps and parameter calculation of the technical solution of the application, and therefore only serve as implementation example content, and cannot be used to limit the protection scope of the application. It should be noted that the following description of the embodiments is only to provide a better understanding of the application by showing examples of the application. Unless otherwise specified, the technical terms used in the application should be understood in their usual sense by those skilled in the art to which the application belongs.

[0035] The magnetic field shielding structure of the surrounding sector coil is applied to a small electronic device wireless charging system, and specifically relates to a magnetic coupling structure applied to a small electronic device. The design steps of the magnetic field shielding structure of the surrounding sector coil are as follows:

[0036] 1) Figure 1 is a schematic diagram of the magnetic coupling type WPT system of the magnetic field shielding structure of the surrounding sector coil and its composition in the embodiment of the application. The parameters of the transmitting coil and the receiving coil are consistent. The magnetic field shielding structure of the surrounding sector coil is located on the upper side of the transmitting coil. The leakage magnetic field generated by the transmitting coil is the working excitation source, generates a reverse magnetic field, and offsets the peripheral magnetic field. The leakage magnetic field in the shielding specific region is changed by changing the central angle of the sector coil to realize the magnetic field shielding of the specific region.

[0037] 2) Determine the selection of the structure parameters of the transmitting coil and the receiving coil and the selection of the system operating frequency. The outer diameter, the inner diameter, and the number of turns of the transmitting coil and the receiving coil are consistent. Determine the outer diameter R W of the coil, the inner diameter R N of the coil, the wire diameter A, the cross-sectional area S of the coil wire, the operating frequency f, the number of turns N, the turn spacing d, and the system energy transmission distance D. The parameterized scanning should satisfy the condition:

[0038] R N =R W -N×(A+d) (1)

[0039] 3) Determine the relationship curve of the number of turns N and the coupling coefficient k through parameterized scanning. The larger the k value, the higher the system transmission efficiency, so the number of turns N, the turn spacing d, and the inner diameter R N of the coil are selected when the k value is maximum.

[0040] 4) Determine the inductance value of the transmitting coil and the receiving coil, select the LCC-S compensation circuit.

[0041] 5) Determine the compensation inductance, build the LCC-S simulation circuit in Matlab, define the ratio between the compensation inductance and the transmitting coil inductance as P, scan the change of system transmission efficiency when P value changes with a step of 0.01, P value range is 0.01-0.99, select the P value when the transmission efficiency reaches the maximum.

[0042] 6) Design the fan-shaped coil shielding structure, determine the coil outer diameter R sh , inner diameter R in , select the central angle θ, coil wire diameter A sh , coil wire cross-sectional area S Q , to avoid excessive coupling between coils, optimize the distance between fan-shaped coils.

[0043] 7) The outer diameter and inner diameter of the fan-shaped coil magnetic field shielding structure should meet:

[0044]

[0045] 8) Parameterize scanning optimization is performed on the placement position of the designed fan-shaped coil magnetic field shielding structure, and the maximum transmission efficiency and the optimal shielding effect placement position are obtained.

[0046] 9) According to the compensation circuit LCC-S, the matching capacitance value C sh under the resonance condition of the fan-shaped coil magnetic field shielding structure is calculated:

[0047] ω 2 L sh C sh = 1 (3)

[0048] 10) By adjusting the matching capacitance C sh , the current phase of the fan-shaped coil magnetic field shielding structure and the transmitting coil are 180° phase angle, realizing the effect of reverse current, and finally generating a reverse magnetic field. Realize the self-impedance condition dominated by inductance:

[0049]

[0050] 11) Figure 2 is a structural diagram of the fan-shaped shielding coil, the fan-shaped shielding coil is used to shield the magnetic field in any angle area, by adjusting the central angle θ, the magnetic field shielding in a specific angle area is realized, where μ0 is the vacuum permeability, N is the number of turns of the fan-shaped coil, R1 and R2 are the outer diameter and inner diameter of the fan-shaped coil, I is the current flowing through the coil, and the magnetic field strength B sh generated by a single fan-shaped coil is:

[0051]

[0052] Take the wireless power supply system of small electronic equipment as an example, verify the actual effect of the shielding level and the size of the space volume occupied by the surrounding sector coil magnetic field shielding structure in the magnetic coupling system.

[0053] Figure 3 It is the overall schematic diagram of the 120° surrounding sector coil magnetic field shielding structure and the magnetic coupling WPT system composed of it, wherein the sector coil magnetic field shielding structure is placed on the upper side of the transmitting coil.

[0054] Further, the parameter values of the transmitting coil and the receiving coil are determined, the outer radius of the coil is R W = 20mm, the wire diameter is A = 0.5mm, the cross-sectional area of the coil wire is S = 0.25π[mm 2 ], the system operating frequency is f = 180kHz, and the energy transmission distance is D = 10mm.

[0055] Further, Figure 4 It is the relationship curve between the number of turns N and the coupling coefficient k determined by parameterized scanning. The larger the k value is, the higher the system transmission efficiency is, so the number of turns N when the k value is the largest is selected. In this embodiment, the coupling coefficient k = 0.30, and the number of turns N obtained at this time is 25.

[0056] Further, the inductance value L P of the transmitting coil and the receiving coil is determined. S = 17μH.

[0057] Further, the mutual inductance between the transmitting coil and the receiving coil is determined:

[0058]

[0059] Further, Figure 5 It is the equivalent circuit diagram of the system compensation circuit LCC-S, and the compensation inductance L f1 is determined. In Matlab, the LCC-S simulation circuit is built, the ratio relationship between the compensation inductance and the self-inductance of the transmitting coil is defined as P, the system transmission efficiency is scanned when the P value changes with a step of 0.01, the P value is selected in the range of 0.01-0.99, and the P value is selected as 0.24 when the transmission efficiency reaches the maximum, at this time the system reaches resonance. According to the resonance condition of the LCC-S compensation circuit:

[0060]

[0061] Further, the compensation circuit parameter value is L f1= 3.44 μH, C1 = 227.27 nF, C2 = 60.38 nF, C3 = 47.71 nF, the main system transmission coil parameter design is completed.

[0062] Further, in order to reduce the peripheral magnetic field strength of the receiving end, a 120° sector coil shielding structure is designed, which has three 120° sector coils, the outer diameter of the coil is R sh = 25 mm, the inner diameter is R in = 7 mm, the number of turns of the coil is 5 turns, and the coil wire diameter and wire cross-sectional area are consistent with the transmitting coil. That is, A sh = 0.5 mm, S Q = 0.25π [mm 2 ].

[0063] Further, Figure 6 is a schematic diagram of the magnetic field shielding structure of the surrounding 120° sector coil.

[0064] Further, the inductance values of the three groups of 120° sector coil magnetic field shielding structures are the same, and the inductance value is L sh1 = L sh2 = L sh3 = 0.504 μH. In order to avoid excess coupling between the coils, a spacing of 1 mm is provided between the coils.

[0065] Further, Figure 7 is an optimized diagram of the relative position of the 120° sector coil magnetic field shielding structure and the transmitting coil. The specific placement position is parameterized and optimized, and the placement position with the maximum transmission efficiency and the best shielding effect is obtained. The placement position is 1 mm above the receiving coil.

[0066] Further, Figure 8 is a schematic diagram of the magnetic field shielding effect of the surrounding 120° sector coil magnetic field shielding structure on the magnetic coupling system, wherein the shielding principle and magnetic field direction of the 120° sector coil magnetic field shielding structure are marked in the figure.

[0067] Further, after L sh is determined, according to the compensation circuit LCC-S, the matching capacitance value C sh under the condition that the inductance of the 120° sector coil magnetic field shielding structure is dominant is calculated.

[0068] Further, under the condition that the inductance is dominant, the matching capacitance C sh is continuously adjusted, and finally the capacitance value is C sh = 1.44 μF, so that the current phase of the 120° sector coil magnetic field shielding structure and the transmitting coil have a phase angle of 180°, realizing the effect of reverse current, and finally generating a reverse magnetic field.

[0069] Further,Figure 9 This is the XZ cross-section system magnetic flux density model effect diagram after the 120° sector coil magnetic field shielding structure is added to the magnetic coupling system. As can be seen from the figure, compared Figure 9 (a) Main system magnetic flux density model, Figure 9 (b) The magnetic flux density modulus range on the receiving coil side is reduced, and the shielding effect can be seen more clearly.

[0070] further, Figure 10 This is a comparison of the magnetic field strength at each measurement point. The shielding effect of the peripheral magnetic field on the receiving coil side is increased by up to 40% compared to the case without the 120° sector coil magnetic field shielding structure.

[0071] Furthermore, in order to achieve magnetic field shielding within a specific 120° area, a separate 120° sector coil shielding structure is used, and its shielding effect is as follows: Figure 11 (b) shows that Figure 11 (a) By comparison, it can be seen that within the 120° area, the shielding coil has an obvious effect and can achieve magnetic field shielding in a specific area.

[0072] In summary, the present invention provides a magnetic field shielding structure with a surrounding sector-shaped coil, achieving a high level of shielding while occupying a small volume, making it suitable for use in small electronic devices. Furthermore, to achieve magnetic field shielding within specific areas in practical applications, the central angle of the sector-shaped coil shielding structure is varied to achieve this goal.

[0073] The present invention may be implemented in other specific forms without departing from its spirit or essential characteristics, and the described embodiments are to be considered in all respects as illustrative rather than restrictive, for example:

[0074] 1) The selection of the central angle of the surrounding sector coil magnetic field shielding structure is not limited to that described in the specific embodiment;

[0075] 2) The outer diameter and inner diameter of the surrounding sector coil magnetic field shielding structure are not limited to those described in the specific embodiment;

[0076] 3) The operating frequency of the surrounding sector coil magnetic field shielding structure is not limited to that described in the specific embodiment;

[0077] 4) The compensation circuit of the surrounding sector coil magnetic field shielding structure is not limited to the specific embodiment described.

[0078] Therefore, the protection scope of the present invention is indicated by the appended claims rather than the above description of the specific embodiments. All changes within the content and scope of the equivalent technical solutions contained in the claims are included in their scope.

Claims

1. A magnetic field shielding structure of a surrounding sector coil, characterized in that: Including transmitting coil , receiving coil ,Surrounding sector shield coil 、 、 … .

2. The magnetic field shielding structure of the surrounding sector coil according to claim 1, characterized in that: Transmitting coil and receiving coil It is a circular planar spiral coil with consistent outer diameter, inner diameter, and number of turns. The coil size is set according to the changes in the application scenario, and the transmission distance is set according to the actual application requirements.

3. The magnetic field shielding structure of the surrounding sector coil according to claim 1, characterized in that: The outer diameter of the sector coil is larger than the radius of the transmitting coil. The outer diameter is determined by testing the shielding effect of the peripheral magnetic field, and the inner diameter is consistent with the radius of the transmitting coil.

4. The magnetic field shielding structure of the surrounding sector coil according to claim 1, characterized in that: The surrounding sector-shaped shielding coils are distributed in parallel above the transmitting coil in a surrounding manner in multiple groups.

5. The magnetic field shielding structure of the surrounding sector coil according to claim 4, characterized in that: Surround sector shield coil 、 、 … Maintain a certain distance between the transmitting coil and the shielding structure, consider the shielding structure's effect on system transmission efficiency and magnetic field shielding, and optimize the placement of the sector shielding coil's magnetic field shielding structure in the system.

6. The magnetic field shielding structure of the surrounding sector coil according to claim 1, characterized in that: According to the requirements of the required shielding area, the sector-shaped shielding coil can form a specific sector-shaped coil shielding structure by changing the central angle of the circle to shield the leakage magnetic field in a specific area.

7. The magnetic field shielding structure of the surrounding sector coil according to claim 1, characterized in that: The current direction of the sector coil shielding structure is adjusted by adding an external matching capacitor, and the matching capacitor is adjusted by selecting a suitable system compensation circuit.

8. The magnetic field shielding structure of the surrounding sector coil according to claim 1, characterized in that: The induced magnetic field of the transmitting coil is used as the excitation source, and the induced current is generated through circuit resonance. When the sector-shaped shielding coil realizes the self-impedance dominated by inductance, the current between the shielding coil and the transmitting coil is at a 180° phase angle, thereby generating a reverse current and ultimately a reverse magnetic field to achieve reactive shielding.

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