Design method of wireless power transmission system based on spiral resonant cavity

Abstract

The application discloses a design method of a wireless power transmission system based on a spiral resonant cavity, and the wireless power transmission system comprises a transmitting coil, a receiving coil, a dielectric substrate and a spiral resonant cavity arranged on the dielectric substrate; the spiral resonant cavity comprises a planar square spiral coil, a planar circular spiral coil, an open loop and a compensation capacitor; the planar square spiral coil, the planar circular spiral coil and the open loop are arranged in sequence from the center of the dielectric substrate to the edge of the dielectric substrate; the dielectric substrate is located between the transmitting coil and the receiving coil; according to the coupling degree of the spiral resonant cavity of the dielectric substrate and the transmitting coil and the receiving coil, the position is adjusted to change the transmission efficiency; when an alternating magnetic field in the transmitting coil is incident to the dielectric substrate, the originally divergent magnetic field changes the direction and starts to gather, and the receiving coil receives more energy, thereby increasing the transmission distance of the wireless power transmission and improving the transmission efficiency of the system.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetics and wireless power transfer technology, specifically relating to a design method for a wireless power transfer system based on a helical resonant cavity. Background Technology

[0002] In daily life, frequent plugging and unplugging of electrical appliances makes charging unsafe, especially in special situations such as mining, oil exploration, and underwater power supply, where traditional power transmission methods pose even greater safety hazards. In recent years, wireless power transfer has received considerable attention. Wireless power transfer technology refers to a method of transmitting electrical energy from the source to the load without using wires. Wireless power transfer technologies can be divided into inductive coupling, microwave radiation, and magnetic coupling resonance. Inductive coupling is suitable for short-distance transmission, while microwave radiation is harmful to humans and other organisms, thus both are significantly limited. Since 2007, the theory of magnetic coupling resonance was first proposed, laying the foundation for research in various fields of wireless power transfer. Because it does not require wires, this technology has advantages such as flexibility, convenience, and safety. Currently, it is widely used in portable electronic products, biomedical devices, electric vehicles, and underwater charging. However, as the charging distance increases, the transmission efficiency of wireless power transfer systems drops sharply, becoming a problem that urgently needs to be solved.

[0003] Dielectric-based spiral resonators are composite materials possessing extraordinary physical properties not found in artificially designed structures or natural materials. By designing the unit structure of a dielectric-based spiral resonator and adjusting the equivalent electromagnetic parameters within a specific frequency range, a dielectric-based spiral resonator with negative permittivity and negative permeability can be obtained. The negative permeability of the dielectric-based spiral resonator allows for focusing diverging magnetic fields and amplifying evanescent waves, adjusting the magnetic field distribution in the transmission space, and improving the system's transmission distance and efficiency. When a dielectric-based spiral resonator is combined with a wireless power transmission system, changing its position affects the system's transmission efficiency. Further analysis of the dielectric-based spiral resonator's position is used to propose methods to increase transmission efficiency. However, there are currently no reports on this aspect. Summary of the Invention

[0004] The technical problem solved by this invention is to provide a design method for a wireless power transmission system based on a helical resonant cavity. The designed wireless power transmission system effectively solves the problem of reduced efficiency as the transmission distance increases during wireless power transmission. A dielectric substrate helical resonant cavity is added between the transmitting coil and the receiving coil. By moving the position of the dielectric substrate helical resonant cavity, the magnetic field distribution of the wireless power transmission system is changed, and the evanescent wave is amplified.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a design method for a wireless power transmission system based on a helical resonant cavity, characterized in that: the wireless power transmission system includes a transmitting coil, a receiving coil, a dielectric substrate, and a helical resonant cavity disposed on the dielectric substrate. Both the transmitting coil and the receiving coil are planar circular helical coils with identical structures. The transmitting coil, the dielectric substrate, and the receiving coil are arranged coaxially and parallel to each other. The minimum inner diameter r1 of both the transmitting coil and the receiving coil is 30 mm, the maximum outer diameter r2 is 58 mm, the turn spacing is 1 mm, and the number of turns is 7. The helical resonant cavity is printed on one side of the dielectric substrate. This helical resonant cavity consists of a planar square helical coil, a planar circular helical coil, an open ring, and a compensation capacitor. The system comprises a planar square spiral coil, a planar circular spiral coil, and an open ring arranged sequentially from the center to the edge of the dielectric substrate. The linewidth w of the planar square spiral coil and the planar circular spiral coil is 2mm, the turn spacing g is 3mm, the linewidth of the open ring is 2mm, and the thickness of the planar square spiral coil, the planar circular spiral coil, and the open ring is 0.1mm. Compensation capacitors are soldered to both ends of the gap in the open ring. The distance between the transmitting coil and the receiving coil is D, and the distance between the receiving coil and the dielectric substrate is d. The range of D is set to [2.5r², 4r²], and the range of d is [0, D]. The wireless power transmission system performs optimally when the placement of the dielectric substrate satisfies d = 2 / 5D.

[0006] Further specified, the dielectric substrate is square, and the material of the dielectric substrate is FR4 with a dielectric constant ε. r =4.4, thickness is 1.6mm, length and width are both 140mm.

[0007] Further specifying, the material of the compensation capacitor is a high-frequency surface-mount capacitor, and the compensation capacitor C p It is 330pF.

[0008] Further defining the process for determining the optimal placement position of the dielectric substrate, the following steps are taken: Within the range of [2.5r², 4r²], the value of D is increased from 2.5r² to 4r² in increments of 1.5r² / 100. The value of d corresponding to the highest transmission efficiency for different values ​​of D is calculated. The solution process is as follows: When D is a set value within the range, the value of d is increased from 0 to D in increments of D / 100 within the range of [0, D]. The S-parameters of the entire wireless power transmission system are calculated for different values ​​of d, and the transmission efficiency of the system is calculated using the S-parameters. The values ​​of D and d corresponding to the maximum efficiency are recorded as D. i and d i Based on the above calculation process, 100 sets of data are finally obtained, namely D. i and d ii = 1, 2, 3... 100; Based on the obtained 100 sets of data, curve fitting was performed, and it was finally concluded that the wireless power transmission system has the best performance when the placement position of the dielectric substrate satisfies d = 2 / 5D.

[0009] Further defining the specific design process of the spiral resonant cavity, the process is as follows: The dielectric substrate is placed vertically on a horizontal plane. A rectangular coordinate system is established with the geometric center of the substrate as the origin, the axis parallel to the horizontal plane as the x-axis, and the axis perpendicular to the horizontal plane as the y-axis. Facing the rectangular coordinate system, the positive x-axis is defined as the x-axis pointing to the left of the origin, and the positive y-axis is defined as the y-axis pointing downwards from the origin. The center coordinates of the planar square spiral coil are set as the origin, i.e., the positioning point Z(0, 0). A unit is defined as 1 mm. The positioning point A(-5, 0) is obtained by translating 5 units towards the negative x-axis from the center coordinates. Then, the y-axis is translated... The first turn of the planar square helical coil is obtained by translating 5 units along the positive x-axis. Then, it is translated 10 units along the positive x-axis to obtain point C (5, 5). Next, it is translated 10 units along the negative y-axis to obtain point D (5, -5). Finally, it is translated 5 units along the negative x-axis to obtain point E (0, -5). Connecting points Z, A, B, C, D, and E sequentially yields the first turn of the planar square helical coil. Following this pattern, starting from point E, and using a wire width of 2mm and a turn spacing of 3mm, the second and third turns of the planar square helical coil can be obtained. The fourth turn of the coil is located at a specific point. Then, each point is connected sequentially in a clockwise direction along the xOy plane to obtain a planar square spiral coil. The coordinates of the end point of the fourth turn of this planar square spiral coil can be defined as point F(0, -20). Starting from point F, a 12mm long and 1mm wide wire is printed along the negative y-axis to connect point F of the planar square spiral coil and point G of the planar circular spiral coil. The coordinates of point G are G(0, -32). The planar circular spiral coil, starting from point G, has an inner diameter of 32mm, an outer diameter of 52mm, and 4 turns. Based on the inner diameter, number of turns, and turn spacing... A planar circular spiral coil is printed by rotating counterclockwise along the xOy plane. The endpoint coordinates of the planar circular spiral coil are H(0, -52). The open ring is located on the outermost layer. Its design process is as follows: find the positioning points I(60, -60), J(-60, -60), K(-60, 60), and L(60, 60) in sequence. Connect the first and last points I, J, K, and L to form a square with a side length of 120mm. With the opening point M(0, 60) as the center position of the gap, cut a gap with a length of 4mm and a width of 2mm along the x-axis parallel direction to obtain the open ring.

[0010] Compared with existing technologies, the present invention has the following advantages and beneficial effects: the transmitting coil and receiving coil of the present invention are small in size and simple in design; the dielectric substrate is made of FR4 material, and a spiral resonant cavity is printed on the dielectric substrate, which is simple in process, low in cost, and can be mass-produced; the designed dielectric substrate spiral resonant cavity can amplify evanescent waves and control the direction of the magnetic field, so that the alternating magnetic field generated by the transmitting coil is refocused on the receiving coil through the dielectric substrate; the 13.56MHz power supply is a standard industrial power supply, and this frequency band source can be widely used for wireless power supply of portable electronic devices and small and medium power appliances, making the large-scale production and application of wireless charging possible. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the transmitting coil and receiving coil structure designed in this invention.

[0012] Figure 2 This is a schematic diagram of the specific structure of the dielectric substrate spiral resonator designed in this invention.

[0013] Figure 3 This is a schematic diagram showing the variation of S-parameters of the dielectric substrate spiral resonant cavity designed in this invention with resonant frequency.

[0014] Figure 4 This is a schematic diagram of the wireless power transmission system with a dielectric substrate spiral resonant cavity according to the present invention.

[0015] Figure 5 This is a schematic diagram of the equivalent permeability of the dielectric substrate spiral resonator designed in this invention.

[0016] Figure 6 This is a schematic diagram illustrating how the transmission efficiency of the present invention varies with the position of the dielectric substrate.

[0017] Figure 7 This is a schematic diagram comparing the transmission efficiency of the wireless power transmission system with a dielectric substrate spiral resonant cavity of the present invention with that without a substrate. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0019] like Figure 1 The diagram shows the structure of the transmitting coil and the receiving coil. Both the transmitting coil and the receiving coil are planar circular helical coils with identical structures. The inner diameter r1 of both the transmitting coil and the receiving coil is 30mm, the outer diameter r2 is 58mm, the turn spacing is 1mm, the number of turns is 7, and the material is Litz wire.

[0020] like Figure 2 The diagram shows a schematic of a spiral resonant cavity on a dielectric substrate. The dielectric substrate is square, made of FR4 material, and has a dielectric constant ε. r =4.4, thickness is 1.6mm, length and width are both 140mm; the spiral resonant cavity is printed on the dielectric substrate, and the layout of each part is as follows: arranged sequentially from the center of the dielectric substrate to the edge of the dielectric substrate, the innermost layer is a planar square spiral coil, the middle layer is a planar circular spiral coil, and the outermost layer is an open ring and a compensation capacitor; the linewidth w of the planar square spiral coil and the planar circular spiral coil is 2mm, the turn spacing g is 3mm, the linewidth of the open ring is 2mm, and the thickness of the planar square spiral coil, the planar circular spiral coil and the open ring is 0.1mm; the compensation capacitor is soldered to both ends of the gap of the open ring, and its value is 330pF.

[0021] like Figure 3 The diagram shows the S-parameters of the designed dielectric substrate spiral resonator as a function of the resonant frequency. First, an electromagnetic simulation model of the dielectric substrate spiral resonator is established. Then, waveguide ports, perfect electrical boundaries, and perfect magnetic boundaries are respectively set on planes perpendicular to the x, y, and z axes. Finally, the model is simulated. Near the resonant frequency, the transmission coefficient S... 21 Starting from the initial 1% complete transmission, the reflection coefficient S decreases. 11 It starts from 0 and complete reflection and gradually increases, reaching resonance at 13.56MHz.

[0022] like Figure 4 The diagram shows a schematic of a wireless power transmission system with a dielectric substrate spiral resonant cavity. The transmitting coil, dielectric substrate, and receiving coil are parallel to each other and placed coaxially and vertically on the same horizontal plane. The resonant frequencies of the transmitting and receiving coils and the resonant frequency of the dielectric substrate spiral resonant cavity are both 13.56MHz. The compensation capacitor C of the transmitting and receiving coils is calculated to be 24pF using formula (1). The distance between the transmitting and receiving coils is defined as D, and the distance between the dielectric substrate and the receiving coil is defined as d. The value range of D is [150, 250], and the range of d is [0, D]. Since the same method is used to simulate the S-parameters, in order to reduce the calculation, three fixed values ​​of the nearest, middle, and farthest distances are selected for analysis within the range of transmission distances. The values ​​of D are 150mm, 200mm, and 250mm, respectively.

[0023]

[0024] like Figure 5The diagram shows the equivalent permeability of the dielectric substrate spiral resonator. The equivalent permeability of the dielectric substrate spiral resonator is calculated according to formulas (2)-(4). At 13.56MHz, the imaginary part of the equivalent permeability of the dielectric substrate spiral resonator is close to 0, which greatly reduces the loss; the real part begins to show a negative value, amplifying the evanescent wave and adjusting the direction of the magnetic field, so that the divergent magnetic field is refocused on the receiving coil, further increasing the transmission distance and improving the transmission efficiency.

[0025]

[0026]

[0027] μ eff =nz (4)

[0028] like Figure 6 The diagram shows the variation of transmission efficiency with the position of the dielectric substrate. The wireless power transmission system can be modeled as a two-port network, and its transmission efficiency can be expressed as Equation (5), S. 21 and S 11 Let d be the transmission coefficient and reflection coefficient of the entire wireless power transmission system, which together determine the system's transmission efficiency. When D takes a certain value, within the range [0, D], the value of d is increased from 0 to D in steps of D / 100. The S-parameters of the entire wireless power transmission system are calculated for different values ​​of d, and the transmission efficiency is calculated using these S-parameters. The value of d corresponding to the maximum efficiency is recorded as d0. i The calculation results show that, as can be seen from the graph, the efficiency increases and then decreases with respect to d at different transmission distances. For the first curve, the maximum efficiency occurs at a transmission distance of 150mm, corresponding to d1 = 60mm; for the second curve, at a transmission distance of 200mm, the maximum efficiency occurs at d2 = 80mm; and for the third curve, at a transmission distance of 250mm, the maximum efficiency occurs at d3 = 100mm. Based on the data, it can be seen that the wireless power transfer system performs optimally when the position of the dielectric substrate satisfies the relationship d = 2 / 5D.

[0029]

[0030] like Figure 7 The diagram shows a comparison of the transmission efficiency of a wireless power transfer system with a dielectric substrate helical resonator and a plateless system. As can be seen from the figure, the transmission efficiency reaches 82.4% when D = 150 mm; the peak efficiency reaches 67.8% and 47.3% when D = 200 mm and 250 mm, respectively. Compared with the plateless wireless power transfer system, the wireless power transfer system with a dielectric substrate improves efficiency by 17.5%, 37.5%, and 35.9% at the three distances, respectively.

[0031] The above embodiments describe the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are only illustrative of the principles of the present invention. Various changes and modifications can be made to the present invention without departing from the scope of the principles of the present invention, and all such changes and modifications fall within the protection scope of the present invention.

Claims

1. A design method for a wireless power transfer system based on a helical resonator, characterized in that: The wireless power transmission system includes a transmitting coil, a receiving coil, a dielectric substrate, and a helical resonant cavity disposed on the dielectric substrate. Both the transmitting and receiving coils are planar circular helical coils with identical structures. The transmitting coil, dielectric substrate, and receiving coil are arranged coaxially and parallel to each other. The minimum inner diameter r1 of both the transmitting and receiving coils is 30 mm, the maximum outer diameter r2 is 58 mm, the turn spacing is 1 mm, and the number of turns is 7. The helical resonant cavity is printed on one side of the dielectric substrate. This helical resonant cavity consists of a planar square helical coil, a planar circular helical coil, an open ring, and a compensation capacitor. The planar square helical coil, the planar circular helical coil, and the open ring are arranged sequentially from the center of the dielectric substrate to its edge. The linewidth w of both the planar square helical coil and the planar circular helical coil is 2 mm, the turn spacing g is 3 mm, the linewidth of the open ring is 2 mm, and the thickness of each planar square helical coil, the planar circular helical coil, and the open ring is 0.1 mm. The compensation capacitor is soldered to both ends of the gap in the open ring. The distance between the transmitting coil and the receiving coil is... D， The distance between the receiving coil and the dielectric substrate is d ,set up D The value range is [2.5r², 4r²]. d The range of variation is [0, D The placement of the dielectric substrate satisfies d =2 / 5 D At that time, the performance of the wireless power transmission system is optimal.

2. The design method for a wireless power transfer system based on a helical resonator according to claim 1, characterized in that: The dielectric substrate is square, and the material of the dielectric substrate is FR4 with a dielectric constant of [missing value]. ε r =4.4, thickness is 1.6mm, length and width are both 140mm.

3. The design method for a wireless power transfer system based on a helical resonator according to claim 1, characterized in that: The compensation capacitor is made of high-frequency surface mount capacitor, and the compensation capacitor C p It is 330pF.

4. The design method of the wireless power transfer system based on a helical resonator according to claim 1, characterized in that: The process for determining the optimal placement position of the dielectric substrate is as follows: within the range of [2.5r², 4r²], the position is adjusted in increments of 1.5r² / 100. D The value increases from 2.5r² to 4r², and the calculation... D The value corresponding to the highest transmission efficiency d The value of is calculated as follows: When D When the set value is within the range of values, in [0, D Within the range of changes, according to D A step change of / 100 makes d The value increases from 0 to D ; calculate d The S-parameters of the entire wireless power transmission system are determined by taking different values, and the transmission efficiency of the system is calculated using these S-parameters. The system with the highest efficiency is then identified. D and d The values ​​are recorded as follows D i and d i Based on the above calculation process, 100 sets of data are finally obtained, that is... D i and d i , i =1, 2, 3...100; Based on the obtained 100 sets of data, curve fitting is performed to finally determine the placement position of the dielectric substrate that satisfies... d =2 / 5 D At that time, the performance of the wireless power transmission system is optimal.

5. The design method of the wireless power transfer system based on a helical resonator according to claim 1, characterized in that: The specific design process of the spiral resonant cavity is as follows: The dielectric substrate is placed vertically on a horizontal plane. A rectangular coordinate system is established with the geometric center of the substrate as the origin, the axis parallel to the horizontal plane as the x-axis, and the axis perpendicular to the horizontal plane as the y-axis. Facing the rectangular coordinate system, the positive x-axis is defined as the x-axis pointing to the left of the origin, and the positive y-axis is defined as the y-axis pointing downwards from the origin. The center coordinates of the planar square spiral coil are set as the origin, i.e., the positioning point Z(0, 0). A unit of 1 mm is defined. The positioning point A(-5, 0) is obtained by translating 5 units towards the negative x-axis from the center coordinates. Then, the positioning point A is translated towards the positive y-axis. Shifting the direction by 5 units yields point B (-5, 5). Then, shifting it 10 units towards the positive x-axis yields point C (5, 5). Next, shifting it 10 units towards the negative y-axis yields point D (5, -5). Finally, shifting it 5 units towards the negative x-axis yields point E (0, -5). Connecting points Z, A, B, C, D, and E sequentially yields the first turn of the planar square helical coil. Following this pattern, starting from point E, and using a wire width of 2mm and a turn spacing of 3mm, the second, third, and fourth turns of the planar square helical coil can be obtained. The positioning points of the coil are then connected sequentially along the xOy plane in a clockwise direction to obtain a planar square spiral coil. The coordinates of the end point of the fourth turn of the planar square spiral coil can be defined as point F (0, -20). Starting from point F, a 12mm long and 1mm wide wire is printed along the negative y-axis to connect point F of the planar square spiral coil and point G of the planar circular spiral coil. The coordinates of point G are G (0, -32). The planar circular spiral coil, starting from point G, has an inner diameter of 32mm, an outer diameter of 52mm, and 4 turns. The coil is then designed according to its inner diameter, number of turns, and turn spacing. The planar circular spiral coil is printed by rotating the xOy plane counterclockwise. At this time, the endpoint coordinates of the planar circular spiral coil are H(0, -52). The open ring is located on the outermost layer. Its design process is as follows: find the positioning points I(60, -60), J(-60, -60), K(-60, 60), and L(60, 60) in sequence. Connect the first and last points I, J, K, and L to form a square with a side length of 120mm. With the opening point M(0, 60) as the center position of the gap, cut a gap with a length of 4mm and a width of 2mm along the x-axis parallel direction to obtain the open ring.

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