A self-resonant multi-stage wireless power supply coil structure and parameter design method

Abstract

The present invention relates to the technical field of multi-level wireless power supply, and specifically discloses a self-resonant multi-level wireless power supply coil structure and parameter design method. The self-resonant multi-level wireless power supply coil structure includes a transmitting coil, a plurality of relay coils and a receiving coil arranged in layers, and the transmitting coil, the relay coil and the receiving coil all use self-resonant coils. The self-resonant coil uses a first layer coil Q1, a first layer PCB board, a second layer coil Q2, a curing sheet, a third layer coil Q3, a second layer PCB board, and a fourth layer coil Q4 arranged in layers from top to bottom. The coils Q1 and Q2 are wound along a first direction, and the coils Q3 and Q4 are wound along a second direction opposite to the first direction. The coils Q1 and Q3 are connected in series, and the coils Q2 and Q4 are connected in series. By applying the present invention, there is no need for a discrete resonant compensation capacitor, and the installation volume is smaller. The self-resonant frequency of the self-resonant coil is stable, and the coil quality factor Q is higher.

Description

Technical Field

[0001] The present invention relates to the technical field of multi-level wireless power supply, and in particular to a self-resonant multi-level wireless power supply coil structure and a parameter design method. Background Art

[0002] Transmission lines are the largest component of the power system and are responsible for transmitting electric energy. Online monitoring equipment can monitor and feedback the status information of transmission lines in real time, and is a key link in ensuring the stable and reliable operation of transmission lines. The application scenarios of online monitoring equipment are becoming increasingly complex, and the scale of demand is gradually expanding. Ensuring its stable power supply has become an important prerequisite for ensuring the reliable and efficient operation of the power grid. Although the combination of solar energy and energy storage batteries is a commonly used DC power supply mode, it is subject to the weight and capacity of the battery, adverse weather conditions such as night, rain, ice and snow, and the cost of manual maintenance after long-term operation. This mode can no longer meet the needs of long-term stable power supply for online monitoring equipment.

[0003] Inductive power technology extracts electric energy from the transmission line through a magnetic field energy collection system installed on the transmission line, and transmits the electric energy to the online monitoring equipment on the low-voltage side of the tower over a long distance and contactlessly through a multi-relay wireless power supply system, thereby ensuring the insulation between the power-taking equipment on the high-voltage side and the electrical equipment on the low-voltage side. In order to provide suitable installation conditions for the multi-relay system, a common method is to integrate the coil and its resonant capacitor into the insulator. As a key link in the efficient and stable operation of the system, the resonant capacitor faces great difficulties when integrated into the insulator. Usually, the type of resonant capacitor is a polypropylene film capacitor, but it is large in size and difficult to integrate into an insulator with a narrow space and a thin shed. In addition, the protrusion formed by this discrete resonant capacitor is prone to accumulate charge, causing tip discharge, posing a serious safety hazard.

[0004] The wireless power supply system based on PCB coil can replace the discrete resonant capacitor with the interlayer capacitor between the upper and lower spiral coils as the resonant compensation capacitor, so it is also called a self-resonant coil. The self-resonant coil has a small installation volume, which is conducive to integration into the insulator, solves the disadvantages of the discrete resonant capacitor, and effectively improves the reliability of the power supply device. However, in practical applications, there are also certain problems with the self-resonant coil. When the resonant frequency of the traditional self-resonant coil is high, the interlayer capacitance of the coil is small, and the self-resonant frequency is easily affected by the external environment. The instability of the self-resonant frequency will cause the output characteristics of the multi-relay system to change, and it will not be able to provide a stable power supply for the monitoring equipment. On the other hand, when the self-resonant frequency is low, the coil quality factor Q is generally small, and the transmission efficiency of the system is low. Therefore, how to design a coil with a stable self-resonant frequency and a high quality factor Q to ensure stable system output characteristics and high transmission efficiency has become an urgent problem to be solved. Summary of the invention

[0005] The present invention provides a self-resonant multi-stage wireless power supply coil structure and a parameter design method, and solves the technical problem of how to design a wireless power supply coil with a stable self-resonant frequency and a high quality factor Q.

[0006] To solve the above technical problems, the present invention provides a self-resonant multi-stage wireless power supply coil structure, comprising a transmitting coil, a plurality of relay coils and a receiving coil arranged in layers, wherein the transmitting coil, the relay coil and the receiving coil all adopt self-resonant coils; the self-resonant coil comprises a first layer coil Q1, a first layer PCB board, a second layer coil Q2, a curing sheet, a third layer coil Q3, a second layer PCB board and a fourth layer coil Q4 arranged in layers from top to bottom, the first layer coil Q1 and the second layer coil Q2 are wound along a first direction, and the first layer coil Q1 and the third layer coil Q3 are connected in series through the first layer PCB board and the curing sheet, the third layer coil Q3 and the fourth layer coil Q4 are wound along a second direction opposite to the first direction, and the second layer coil Q2 and the fourth layer coil Q4 are connected in series through the curing sheet and the second layer PCB board.

[0007] Preferably, when the self-resonant coil is used as a transmitting coil, two ends of the AC power supply are connected to the other connection end of the first layer coil Q1 and the other connection end of the fourth layer coil Q4 respectively.

[0008] Preferably, when the self-resonant coil is used as a relay coil, the other connection ends of the four-layer coils Q1, Q2, Q3, and Q4 are not processed; when the self-resonant coil is used as a receiving coil, the other connection end of the first-layer coil Q1 and the other connection end of the fourth-layer coil Q4 are respectively connected to the input end of the rectifier.

[0009] Preferably, the series self-resonance frequency of the self-resonance coil is expressed as:

[0010]

[0011] Among them, L s represents the self-inductance of the self-resonant coil, C p represents the inter-turn capacitance of the self-resonant coil, C s represents the interlayer capacitance of the self-resonant coil.

[0012] Preferably, the first layer coil Q1, the second layer coil Q2, the third layer coil Q3, and the fourth layer coil Q4 are planar spiral coils with constant turn spacing. Except for the different winding directions, the other parameters of the four layers of coils are the same, and there is no offset between the upper and lower parts. The first layer PCB board and the second layer PCB board are PCB boards of the same specifications, that is, except for the different hole positions, all parameters of the two layers of PCB boards are the same.

[0013] Preferably, L s , C p , C s Calculated by the following formula:

[0014]

[0015] Among them, μ represents the magnetic permeability of copper, n, r in 、r out Respectively represent the number of turns, inner diameter and outer diameter of the planar spiral coil, Defined as ε0 represents the dielectric constant under vacuum conditions, ε d Represents the relative dielectric constant of the substrate material, ε a Represents the relative dielectric constant of the coil external filling material, ε p represents the relative dielectric constant of the cured sheet, w represents the width of the winding, and l is defined as s represents the turn spacing, θ represents the plane integration angle, t d Indicates the thickness of the PCB board, t p is the thickness of the cured sheet, and F is defined as x refers to the value inside the brackets of function F.

[0016] The present invention also provides a parameter design method, which is applied to the self-resonant multi-stage wireless power supply coil structure, and the key point is that it includes the steps of:

[0017] S1. According to actual needs, the maximum outer diameter r of the self-resonant coil is given out,max , minimum inner diameter r in,min 、Minimum thickness of PCB substrate t dmin , maximum thickness t dmax , Maximum number of turns n max and the minimum number of turns n min ; Determine n, s, w, t d The step lengths △n, △s, △w, △t d ; Determine n, s, w, t d All other parameters except

[0018] S2, initialization coil turns n = n max ;

[0019] S3, according to the minimum number of turns n min Calculate the maximum turn spacing s max and the maximum line width w max , according to the maximum number of turns n max Determine the minimum value s of the turn spacing min and the minimum line width w min ;

[0020] S4, in (s max ,s min )、(w max ,w min )、(n max ,n min )、(t dmin ,t dmax ), with step lengths △n, △s, △w, △t d Perform iterative optimization to determine the optimal solution that satisfies ΔC p / C s ≤K c And a set of n, s, w, t that maximizes the quality factor Q d Value, K c Indicates the change in inter-turn capacitance ΔC when the self-resonant frequency is just stable p and interlayer capacitance C s ratio.

[0021] Furthermore, step S4 specifically includes the steps of:

[0022] S41, s=s max , w=w max , t d =t dmax ;

[0023] S42, determine the current n, s, w, t d Whether ΔC is satisfied p / C s ≤K c , if yes, calculate the current quality factor Q and proceed to the next step, if no, let t d Reduce △t d Then re-judge;

[0024] S43, determine whether w is less than w min If yes, go to the next step. If no, let w decrease by △w and let t d =t dmax Then return to step S42;

[0025] S44, determine whether s is less than s min If yes, go to the next step. If no, let s decrease by △s and let t d =t dmax 、w=wmax Then return to step S42;

[0026] S45. Determine whether n is less than n min If yes, proceed to the next step. If no, reduce n by △n (set to 1 in this example) and return to step S2.

[0027] S46. Compare all the calculated Q values ​​and select the n, s, w, t with the largest Q value. d As determined by n, s, w, t d .

[0028] Furthermore, max Calculated by the following formula:

[0029]

[0030] w max satisfy:

[0031] w max =0.8s max .

[0032] Further, the quality factor is calculated by the following formula:

[0033]

[0034] Where ρ is the resistivity of copper, μ0 is the magnetic permeability under vacuum conditions, and H i is the magnetic field strength of the i-th coil when the excitation current is 1A, l i represents the length of the i-th coil, i∈[1,n], Φ(w,t c ) is an expression related to line width and copper thickness, D kd and D kp are the tangent loss values ​​of the substrate and the cured sheet, δ=[ρ / (πμ0f)] 1 / 2 represents the skin depth of the coil at frequency f.

[0035] The present invention provides a self-resonant multi-stage wireless power supply coil structure and parameter design method, wherein the self-resonant multi-stage wireless power supply coil structure includes a transmitting coil, a plurality of relay coils and a receiving coil arranged in layers, wherein the transmitting coil, the relay coil and the receiving coil all use self-resonant coils. The self-resonant coil uses a first layer coil Q1, a first layer PCB board, a second layer coil Q2, a curing sheet, a third layer coil Q3, a second layer PCB board, and a fourth layer coil Q4 arranged in layers from top to bottom, wherein the first layer coil Q1 and the second layer coil Q2 are wound along a first direction, and the first layer coil Q1 and the third layer coil Q3 are connected in series through the first layer PCB board and the curing sheet, and the third layer coil Q3 and the fourth layer coil Q4 are wound along a second direction opposite to the first direction, and the second layer coil Q2 and the fourth layer coil Q4 are connected in series through the curing sheet and the second layer PCB board. By applying the present invention, there is no need for a discrete resonant compensation capacitor, and when integrated into an insulator, it has a smaller installation volume, and can better ensure the insulation performance of the insulator. In addition, compared with the conventional self-resonant coil, the self-resonant coil of the present invention has a stable self-resonant frequency and a higher coil quality factor Q. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is a hierarchical diagram of a self-resonant multi-stage wireless power supply coil structure provided by an embodiment of the present invention;

[0037] Figure 2 is an application example diagram of a self-resonant multi-stage wireless power supply coil structure provided by an embodiment of the present invention;

[0038] Figure 3 is a hierarchical diagram of a self-resonant coil provided by an embodiment of the present invention;

[0039] Figure 4 is a connection relationship diagram of a self-resonant coil provided in an embodiment of the present invention;

[0040] Figure 5 is a parameter definition diagram of a self-resonant coil provided by an embodiment of the present invention;

[0041] Figure 6 is a distributed circuit model diagram of coils Q1 and Q2 provided in an embodiment of the present invention;

[0042] Figure 7 The embodiment of the present invention provides Figure 6 Equivalent circuit diagram of

[0043] Figure 8 The embodiment of the present invention provides Figure 6 The final equivalent circuit diagram of

[0044] Fig. 9 is a distributed circuit model diagram of a self-resonant coil provided in an embodiment of the present invention;

[0045] Fig.10 It is a flow chart of a parameter design method of a self-resonant coil provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0046] The following specifically illustrates the implementation mode of the present invention in conjunction with the accompanying drawings. The embodiments are provided for illustrative purposes only and cannot be understood as limiting the present invention. The accompanying drawings are provided for reference and illustration only and do not constitute a limitation on the scope of patent protection of the present invention, because many changes can be made to the present invention without departing from the spirit and scope of the present invention.

[0047] The embodiment of the present invention provides a self-resonant multi-stage wireless power supply coil structure. Figure 1 As shown, the self-resonant multi-stage wireless power supply coil structure includes a transmitting coil arranged in layers, a plurality of relay coils ( Figure 1 Taking three relay coils as an example) and receiving coils, the transmitting coil, relay coil and receiving coil all use self-resonant coils.

[0048] As an application example, the self-resonant multi-stage wireless power supply coil structure is applied to high-voltage wireless power collection, and the schematic diagram is as follows: Figure 2 As shown. The self-resonant coil is installed in the insulator through the core rod. The size of the self-resonant coil is constrained by the internal space of the insulator.

[0049] like Figure 3 As shown in the hierarchical structure diagram, the self-resonant coil includes a first-layer coil Q1, a first-layer PCB board, a second-layer coil Q2, a curing sheet, a third-layer coil Q3, a second-layer PCB board, and a fourth-layer coil Q4 arranged from top to bottom. The first-layer coil Q1 and the second-layer coil Q2 are wound along a first direction, and the first-layer coil Q1 and the third-layer coil Q3 are connected in series through the first-layer PCB board and the curing sheet. The third-layer coil Q3 and the fourth-layer coil Q4 are wound along a second direction opposite to the first direction, and the second-layer coil Q2 and the fourth-layer coil Q4 are connected in series through the curing sheet and the second-layer PCB board. The first-layer coil Q1 and the third-layer coil Q3 are connected, and the second-layer coil Q2 and the fourth-layer coil Q4 are connected in order to increase the interlayer capacitance of the self-resonant coil, ensure that the current flow direction of the coil is always consistent, and the coil structure is compact.

[0050] The function of the curing sheet is to connect two PCB boards. The inner and outer diameters of the curing sheet are consistent with those of the PCB boards, and the thickness is usually 0.1mm-0.2mm.

[0051] When used as a transmitting coil, the two ends of the AC power supply are connected to the other connection end of the first layer coil Q1 and the other connection end of the fourth layer coil Q4 respectively. The second layer coil Q2 and the third layer coil Q3 do not lead out the outer end (the other connection end) and are suspended in the air. There is a displacement current through the substrate between the outer end of Q2 and Q1, and there is a displacement current through the substrate between the outer end of Q3 and Q4. When used as a relay coil, the other connection ends of the four layers of coils Q1, Q2, Q3, and Q4 are not processed. When used as a receiving coil, the other connection end of the first layer coil Q1 and the other connection end of the fourth layer coil Q4 are connected to the two input ends of the rectifier respectively.

[0052] like Figure 4 As shown in the schematic diagram of the connection relationship of the four-layer coil used as the transmitting coil, the first layer coil Q1 and the second layer coil Q2 are wound counterclockwise from the outer layer to the inner layer, and the two inner ends of the first layer coil Q1 and the third layer coil Q3 are connected. The third layer coil Q3 and the fourth layer coil Q4 are wound clockwise from the outer layer to the inner layer, and the two inner ends of the second layer coil Q2 and the fourth layer coil Q4 are connected. The two ends of the AC power supply are respectively connected to the outer ends of the first layer coil Q1 and the outer ends of the fourth layer coil Q4, so that the external wiring is all on the outside of the coil, making the structure more compact.

[0053] The four-layer coil in this embodiment adopts a planar spiral coil with a constant turn spacing. Except for the different winding directions, the other parameters of the four-layer coils, including the number of turns, turn spacing, winding, inner diameter, outer diameter, etc., are the same, and the upper and lower PCB boards are aligned without offset. The first layer PCB board and the second layer PCB board also use PCB boards of the same specifications, that is, except for the different opening positions of the two layers of PCB boards, all parameters are the same. Figure 5 As shown in the parameter definition diagram, in this example, n represents the number of turns of the planar spiral coil, r in is the distance from the center of the circle to the midpoint of the first turn of the coil, i.e. the inner diameter of the planar spiral coil, r out is the distance from the center of the circle to the midpoint of the nth turn of the coil, i.e., the outer diameter of the planar spiral coil, s is the turn spacing of the planar spiral coil, the planar spiral coil uses a winding with a rectangular cross section, w is the width of the winding used, and t c is the copper foil thickness of the winding wire used, t d is the thickness of the PCB board.

[0054] The distributed circuit model of coils Q1 and Q2 is as follows: Figure 6 As shown, the distributed circuit model of Q3 and Q4 is similar. (1,1) To L (1,n) represents the inductance from the first turn to the nth turn in Q1, L (2,1) To L (2,n) represents the inductance of the first to nth turns of the coil in Q2, C p(1,1) To Cp(1,n) represents the inter-turn capacitance from the first turn to the nth turn of Q1, C p(2,1) To C p(2,n) represents the inter-turn capacitance from the first turn to the nth turn of Q2, C sn and C sn+1 It represents the interlayer capacitance between the n-th coil in Q1 and the n-th coil in Q2. In a distributed circuit, two interlayer capacitances are constructed at both ends of the two opposite coils, such as C sn and C sn+1 ,like Figure 6 shown.

[0055] Figure 7 (a) and (b) are the distributed circuit and equivalent circuit formed by the first coil turns of Q1 and Q2 respectively. C1 and C2 represent the interlayer capacitance between the nodes at both ends of the first coil turn in Q1 and the nodes at both ends of the first coil turn in Q2 in the distributed circuit. Writing the KVL equation for the distributed circuit formed by the first coil turn in Q1 and Q2 yields:

[0056]

[0057] In formula (1), M c1 represents the mutual inductance between the first coil turn in Q1 and the first coil turn in Q2, ω represents the excitation frequency of the AC power supply, represents the voltage on the first coil turn of Q1, represents the voltage across the interlayer capacitor C1, represents the voltage on the first coil turn in Q2, represents the voltage across the interlayer capacitor C2, represents the current flowing through the first coil turn of Q1, represents the current flowing through the first coil turn of Q2, represents the reactance generated by the inductance of the first turn of coil in Q1 and the inter-turn capacitance, It represents the reactance generated by the inductance of the first coil turn and the inter-turn capacitance in Q2. Since the distance between the upper and lower layers is very close, the coupling coefficient k is approximately equal to 1, and the upper and lower coils are exactly the same, that is:

[0058]

[0059] In addition, the self-inductance L of each turn of the coil (1,1) The value of is between nH-μH, and the inter-turn capacitance C p(1,1) Between fF-pF. Therefore, at an excitation frequency of 1MHz:

[0060]

[0061] Therefore, formula (1) can be approximately expressed as:

[0062]

[0063] Combining equations (2) and (4) we can get:

[0064] V L(2,1) =(I3+I5)·jωL (2,1) =I6·jωL (2,1) (5)

[0065] like Figure 7 As shown in (a), I6 is the total current in the first turn of coil in Q2, which is the sum of I5 and I3.

[0066] Since k is approximately equal to 1, I3+I5 is equal to both I6 and I1. From KCL, we can get:

[0067]

[0068] Use the same method to write KVL and KCL equations for the remaining circuits. After equivalent simplification, the final equivalent circuits of Q1 and Q2 can be obtained as follows: Figure 8 As shown, where L s Represents the total self-inductance of a layer of coil, C p Represents the total inter-turn capacitance of a layer of coil, C s It represents the total interlayer capacitance between the two layers of coils Q1 and Q2. It can be found that the self-inductance is connected in parallel with the inter-turn capacitance in the equivalent circuit, and then in series with the inter-layer capacitance.

[0069] Since the distributed circuits of Q3 and Q4 are similar to those of Q1 and Q2, the distributed circuit of the four-layer double-winding self-resonant coil is as follows: Fig. 9 The final equivalent circuit of the four-layer double-winding self-resonant coil is similar to the equivalent circuit of Q1 and Q2, as shown in Figure 8 shown.

[0070] The inner diameter r of the four-layer double-winding coil in 、Outer diameter r out The relationship between the coil self-inductance, interlayer capacitance and interturn capacitance can be expressed as follows:

[0071]

[0072] In formula (7), t p is the thickness of the cured sheet, t d Indicates the thickness of the PCB board, ε p is the relative dielectric constant of the cured sheet. k is the ratio of the area facing each other between Q2 and Q3 to the area of ​​the single-layer coil. Defined as l is defined as θ represents the plane integral angle, μ represents the magnetic permeability of copper, ε0 represents the dielectric constant under vacuum conditions, and ε d It represents the relative dielectric constant of the PCB substrate material medium, and F is defined as ε a represents the relative dielectric constant of the coil external filling material, ε p represents the relative dielectric constant of the cured sheet. At this time, the series self-resonant frequency of the self-resonant coil can be expressed as:

[0073]

[0074] From equation (8), it can be found that the coil resonant frequency is related to the coil's self-inductance, interlayer capacitance, and interturn capacitance.

[0075] Since the main reason for the change of the coil self-resonance frequency is the change of the coil inter-turn capacitance, when the coil inter-layer capacitance is small, the change of the inter-turn capacitance will cause a large change in the coil self-resonance frequency, which makes the coil self-resonance frequency susceptible to changes in external filling materials. Therefore, the stability of the coil self-resonance frequency can be improved by increasing the coil inter-layer capacitance value and reducing the change of the coil inter-turn. In order to better illustrate the relationship between the self-resonance frequency change range and the inter-turn capacitance and inter-layer capacitance, the following can be obtained by transforming equation (8):

[0076]

[0077] f1 and f2 represent the self-resonant frequencies before and after the change respectively. p1 , C p2 Represent the inter-turn capacitance before and after the change respectively.

[0078] Simplifying, we can get:

[0079]

[0080] In formula (10), ΔC p =C p2 -C p1 .

[0081] The ratio of the change in inter-turn capacitance to the inter-layer capacitance can be approximately expressed as:

[0082]

[0083] From equation (11), we can see that by adjusting the substrate thickness t d Can be used for ΔC p / C s to adjust the value.

[0084] The quality factor Q of a coil is usually defined as ω is the operating angular frequency, L s is the coil self-inductance, R s is the coil AC internal resistance (the sum of DC internal resistance and dielectric loss internal resistance), R s It can be obtained through existing calculation methods.

[0085] For wireless power supply systems, the efficiency of the system can be improved by improving the coil quality factor Q. The coil quality factor Q can be expressed as:

[0086]

[0087] Where ρ is the resistivity of copper, μ0 is the magnetic permeability under vacuum conditions, and H i is the magnetic field strength on the conductor surface when the excitation current is 1A, l i represents the length of the i-th coil, i∈[1,n], Φ(w,t c ) is an expression related to line width and copper thickness, usually obtained by fitting finite element simulation data. kd and D kp are the tangent loss values ​​of the substrate and the cured sheet respectively (which can be obtained by consulting the data), and δ represents the skin depth of the coil at the frequency f, and its size can be expressed as:

[0088] δ=[ρ / (πμ0f)] 1 / 2 (13)

[0089] Before optimizing the design, it is also necessary to establish the constraints of parameter design.

[0090] Constraint 1: When designing a self-resonant coil, first consider the restrictions of the external space size on the coil. Since the entire wireless power supply coil will be integrated into the large shed of the insulator, the parameters of the insulator also determine the spatial size of the coil. The outer diameter of the coil shall not exceed the outer diameter of the large shed of the insulator, the inner diameter of the coil shall not be less than the outer diameter of the core rod, and the total thickness of the coil shall not be greater than the thickness of the large shed of the insulator.

[0091] Constraint 2: When processing PCBs, the processing technology of the PCB board and the processing capabilities of the manufacturer need to be considered. The thickness of the PCB board is usually 0.1mm and 0.2mm. In addition, the copper thickness of the outer layer (coils Q1 and Q4) is usually between 1-6oz, while the copper thickness of the inner layer (coils Q2 and Q3) is usually between 0.5oz and 2oz.

[0092] Constraint 3: When designing the coil, it is also necessary to consider the mutual restrictions between parameters. For the number of turns, inner diameter, outer diameter, and turn spacing, the following relationship is satisfied:

[0093] r in =r out -s*n (14)

[0094] Since the size of the coil is limited by the insulator, there is a maximum coil outer diameter and a minimum inner diameter r in,min , so the maximum turn spacing of the coil is s max It can be expressed as:

[0095]

[0096] In addition, when the turn spacing of the coil is determined, in order to ensure a high coil quality factor Q, the maximum value of the coil width w max Should meet:

[0097] w max =0.8s max (16)

[0098] Based on the coil quality factor Q expression and actual constraints, the coil inner diameter, turn spacing, line width and other parameters are designed to improve the coil quality factor Q. At the same time, the ratio of the change in inter-turn capacitance to the inter-layer capacitance when the self-resonant frequency is just stable is K c , by designing the substrate thickness of the PCB material, the stability of the coil's self-resonant frequency can be improved. The coil parameter design process is as follows Fig.10 As shown, the specific design steps include:

[0099] S1. According to actual needs, the maximum outer diameter r of the self-resonant coil is given out,max , minimum inner diameter r in,min 、Minimum thickness of PCB substrate t dmin , maximum thickness t dmax , Maximum number of turns n max and the minimum number of turns n min ; Determine n, s, w, t d The step lengths △n, △s, △w, △t d ; Determine n, s, w, t d All other parameters except

[0100] S2, initialization coil turns n = n max ;

[0101] S3, according to the minimum number of turns n min According to formula (15) and formula (16), the maximum turn spacing s is calculated max and the maximum line width w max , according to the maximum number of turns n max Determine the minimum value s of the turn spacing min and the minimum line width w min ;

[0102] S4, in (s max ,s min)、(w max ,w min )、(n max ,n min )、(t dmin ,t dmax ), with step lengths △n, △s, △w, △t d Perform iterative optimization to determine the optimal solution that satisfies ΔC p / C s ≤K c And a set of n, s, w, t that maximizes the quality factor Q d value.

[0103] Step S4 specifically includes the following steps:

[0104] S41, s=s max , w=w max , t d =t dmax ;

[0105] S42, determine the current n, s, w, t d Whether ΔC is satisfied p / C s ≤K c , if yes, calculate the current quality factor Q and proceed to the next step, if no, let t d Reduce △t d Then re-judge;

[0106] S43, determine whether w is less than w min If yes, go to the next step. If no, let w decrease by △w and let t d =t dmax Then return to step S42;

[0107] S44, determine whether s is less than s min If yes, go to the next step. If no, let s decrease by △s and let t d =t dmax 、w=w max Then return to step S42;

[0108] S45. Determine whether n is less than n min If yes, proceed to the next step. If no, reduce n by △n (set to 1 in this example) and return to step S2.

[0109] S46. Compare all the calculated Q values ​​and select the n, s, w, t with the largest Q value. d As determined by n, s, w, t d .

[0110] In summary, the embodiment of the present invention provides a self-resonant multi-stage wireless power supply coil structure and parameter design method, wherein the self-resonant multi-stage wireless power supply coil structure includes a transmitting coil, a plurality of relay coils and a receiving coil arranged in layers, and the transmitting coil, the relay coil and the receiving coil all use self-resonant coils. The self-resonant coil uses a first layer coil Q1, a first layer PCB board, a second layer coil Q2, a curing sheet, a third layer coil Q3, a second layer PCB board, and a fourth layer coil Q4 arranged in layers from top to bottom, the first layer coil Q1 and the second layer coil Q2 are wound along a first direction, and the first layer coil Q1 and the third layer coil Q3 are connected in series through the first layer PCB board and the curing sheet, the third layer coil Q3 and the fourth layer coil Q4 are wound along a second direction opposite to the first direction, and the second layer coil Q2 and the fourth layer coil Q4 are connected in series through the curing sheet and the second layer PCB board. By applying the present invention, there is no need for a discrete resonant compensation capacitor, and when integrated into an insulator, it has a smaller installation volume, and can better ensure the insulation performance of the insulator. In addition, compared with the conventional self-resonant coil, the self-resonant coil of the present invention has a stable self-resonant frequency and a higher coil quality factor Q.

[0111] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A self-resonant multi-stage wireless power supply coil structure, characterized in that: It includes a transmitting coil, a plurality of relay coils and a receiving coil arranged in layers, wherein the transmitting coil, the relay coil and the receiving coil are all self-resonant coils; the self-resonant coil includes a first layer coil Q1, a first layer PCB board, a second layer coil Q2, a curing sheet, a third layer coil Q3, a second layer PCB board and a fourth layer coil Q4 arranged in layers from top to bottom, the first layer coil Q1 and the second layer coil Q2 are wound along a first direction, and the first layer coil Q1 and the third layer coil Q3 are connected in series through the first layer PCB board and the curing sheet, the third layer coil Q3 and the fourth layer coil Q4 are wound along a second direction opposite to the first direction, and the second layer coil Q2 and the fourth layer coil Q4 are connected in series through the curing sheet and the second layer PCB board; The self-inductance L of the self-resonant coil s , inter-turn capacitance C p , interlayer capacitance C s Calculated by the following formula: Among them, μ represents the magnetic permeability of copper, n, r in 、r out Respectively represent the number of turns, inner diameter and outer diameter of the planar spiral coil, Defined as ε0 represents the dielectric constant under vacuum conditions, ε d Represents the relative dielectric constant of the substrate material, ε a Represents the relative dielectric constant of the coil external filling material, ε p represents the relative dielectric constant of the cured sheet, w represents the width of the winding, and l is defined as represents the length of the planar spiral coil, s represents the turn spacing, θ represents the plane integral angle, and t d Indicates the thickness of the PCB board, t p is the thickness of the cured sheet, and the function F is defined as x refers to the value inside the brackets of function F.

2. The self-resonant multi-stage wireless power supply coil structure according to claim 1, characterized in that: When the self-resonant coil is used as a transmitting coil, two ends of the AC power supply are connected to the other connection end of the first layer coil Q1 and the other connection end of the fourth layer coil Q4 respectively.

3. The self-resonant multi-stage wireless power supply coil structure according to claim 2, characterized in that: When the self-resonant coil is used as a relay coil, the other connection ends of the four-layer coils Q1, Q2, Q3, and Q4 are not processed; when the self-resonant coil is used as a receiving coil, the other connection end of the first-layer coil Q1 and the other connection end of the fourth-layer coil Q4 are respectively connected to the input end of the rectifier.

4. The self-resonant multi-stage wireless power supply coil structure according to claim 3, characterized in that: The series self-resonant frequency of the self-resonant coil is expressed as:

5. The self-resonant multi-stage wireless power supply coil structure according to claim 4, characterized in that: The first layer coil Q1, the second layer coil Q2, the third layer coil Q3, and the fourth layer coil Q4 are planar spiral coils with constant turn spacing. Except for the different winding directions, the other parameters of the four layers of coils are the same, and there is no offset between the upper and lower sides. The first layer PCB board and the second layer PCB board are PCB boards of the same specifications, that is, except for the different hole positions, all parameters of the two layers of PCB boards are the same.

6. A parameter design method, applied to the self-resonant multi-stage wireless power supply coil structure according to any one of claims 1 to 5, characterized in that: Includes steps: S1. According to actual needs, the maximum outer diameter r of the self-resonant coil is given out,max , minimum inner diameter r in,min 、Minimum thickness of PCB substrate t dmin , maximum thickness t dmax , Maximum number of turns n max and the minimum number of turns n min ; Determine n, s, w, t d The step lengths △n, △s, △w, △t d ; Determine n, s, w, t d All other parameters except S2, initialization coil turns n = n max ; S3, according to the minimum number of turns n min Calculate the maximum turn spacing s max and the maximum line width w max , according to the maximum number of turns n max Determine the minimum value s of the turn spacing min and the minimum line width w min ; S4, in (s max ,s min )、(w max ,w min )、(n max ,n min )、(t dmin ,t dmax ), with step lengths △n, △s, △w, △t d Perform iterative optimization to determine the optimal solution that satisfies ΔC p / C s ≤K c And a set of n, s, w, t that maximizes the quality factor Q d Value, K c Indicates the change in inter-turn capacitance ΔC when the self-resonant frequency is just stable p and interlayer capacitance C s ratio.

7. The parameter design method according to claim 6, characterized in that: Step S4 specifically includes the following steps: S41、s=s max ,w=w max ,t d =t dmax ; S42, determine the current n, s, w, t d Whether ΔC is satisfied p / C s ≤K c , if yes, calculate the current quality factor Q and proceed to the next step, if no, let t d Reduce △t d Then re-judge; S43, determine whether w is less than w min If yes, go to the next step. If no, let w decrease by △w and let t d =t dmax Then return to step S42; S44, determine whether s is less than s min If yes, go to the next step. If no, let s decrease by △s and let t d =t dmax 、w=w max Then return to step S42; S45. Determine whether n is less than n min If yes, go to the next step, if no, reduce n by △n and return to step S2; S46. Compare all the calculated Q values ​​and select the n, s, w, t with the largest Q value. d As determined by n, s, w, t d .

8. The parameter design method according to claim 7, characterized in that: s max Calculated by the following formula: w max satisfy: In max =0.8s max 。 9. The parameter design method according to claim 8, characterized in that: The quality factor is calculated by the following formula: Where ρ is the resistivity of copper, μ0 is the magnetic permeability under vacuum conditions, and H i is the magnetic field strength of the i-th coil when the excitation current is 1A, l i represents the length of the i-th coil, i∈[1,n], Φ(w,t c ) is related to the line width w and copper thickness t c The relevant expression, D kd and D kp are the tangent loss values ​​of the substrate and the cured sheet, δ = [ρ / (πμ0f)] 1 / 2 represents the skin depth of the coil at frequency f.

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