Coil structure for power over ethernet

Abstract

A coil structure includes first and second magnetic rings, a first-side single-wire group comprising first to sixth single wires, and a second-side single-wire group comprising seventh to ninth single wires. The first to third single wires and the seventh single wire are twisted together to form a first twisted wire, and the fourth to sixth single wires and the eighth single wire are twisted together to form a second twisted wire. The first and second twisted wires are wound around the first magnetic ring in an alternating but non-overlapping manner. The seventh to ninth single wires are twisted together to form a third twisted wire and extend to wind around the second magnetic ring. The fourth single wire on the first side of the first magnetic ring, the second single wire on the second side, and the third single wire are twisted together to form a fourth twisted wire. The fifth and sixth single wires on the first side of the first magnetic ring, and the first single wire on the second side, are twisted together to form a fifth twisted wire. The first to third single wires on the first side of the first magnetic ring are twisted together to form a sixth twisted wire. The fourth to sixth single wires on the second side of the first magnetic ring are twisted together to form a seventh twisted wire.

Description

Technical Field

[0001] This disclosure relates to a coil structure, and more particularly to a coil structure for use in Ethernet power supply. Prior Technology

[0002] Power over Ethernet (PoE) is a technology that transmits power and data to electronic devices over Ethernet networks via twisted-wire cables. As the functionality of electrical devices increases, their power requirements also grow, necessitating the use of thicker single-core copper wires on the PoE power supply side to meet high current and high power demands. However, the resilience, stress, and hardness of single-core copper wire all increase with increasing wire diameter, making soldering and lead winding more difficult. Under these circumstances, manual coil winding is essential, increasing production costs and making it difficult to ensure consistent product quality. Summary of the Invention

[0003] Therefore, the embodiments disclosed herein provide a coil structure for Ethernet power supply, comprising a first magnetic ring, a second magnetic ring, a first side single-wire group, and a second side single-wire group. The first magnetic ring has a first side and a second side. The first side single-wire group includes a first single wire, a second single wire, a third single wire, a fourth single wire, a fifth single wire, and a sixth single wire. The second side single-wire group includes a seventh single wire, an eighth single wire, and a ninth single wire. The first, second, third, and seventh single wires are twisted together to form a first twisted wire, and the fourth, fifth, sixth, and eighth single wires are twisted together to form a second twisted wire. The first and second twisted wires are wound around the first magnetic ring in an alternating but non-overlapping manner. The seventh single wire, which is wound outside the ring and located on the second side of the first magnetic ring, and the eighth and ninth single wires, which are wound outside the ring and located on the first side of the first magnetic ring, are twisted together outside the first magnetic ring to form a third twisted wire, and the third twisted wire extends from the first magnetic ring to the second magnetic ring and is wound around the second magnetic ring. A fourth single wire, located outside the loop and on the first side of the first magnetic ring, a second single wire, and a third single wire located on the second side of the first magnetic ring are twisted together to form a fourth twisted wire outside the first magnetic ring. A fifth and sixth single wire, located outside the loop and on the first side of the first magnetic ring, and a first single wire located on the second side of the first magnetic ring are twisted together to form a fifth twisted wire outside the first magnetic ring. A first, second, and third single wire, located outside the loop and on the first side of the first magnetic ring, are twisted together to form a sixth twisted wire outside the first magnetic ring. A fourth, fifth, and sixth single wire, located outside the loop and on the second side of the first magnetic ring, are twisted together to form a seventh twisted wire outside the first magnetic ring.

[0004] According to the embodiments disclosed herein, the fourth and fifth strands are twisted together to form a central strand, the number of strands in the central strand being 0 to 26 per inch.

[0005] According to the embodiments disclosed herein, the cross-sectional area of ​​the first magnetic ring is greater than the cross-sectional area of ​​the second magnetic ring.

[0006] According to the embodiments disclosed herein, after the third stranded wire extends from the first magnetic ring to the second magnetic ring and completes the winding, the distance between the first magnetic ring and the second magnetic ring is less than or equal to 2.5 mm.

[0007] According to the embodiments disclosed herein, the first magnetic ring is a 360° ring, and the first stranded wire and the second stranded wire are distributed at a total angle of 300° from the starting point to the ending point of the winding on the first magnetic ring.

[0008] According to the embodiments disclosed herein, the second magnetic ring is a 360° ring, and the third stranded wire is distributed over a total of 270° from the winding start point to the winding end point on the second magnetic ring.

[0009] According to the embodiments disclosed herein, the first single wire, the second single wire, the third single wire, and the seventh single wire in the first twisted wire have at least two different wire diameters, and the fourth single wire, the fifth single wire, the sixth single wire, and the eighth single wire in the second twisted wire have at least two different wire diameters.

[0010] According to the embodiments disclosed herein, the maximum wire diameter difference between the first single wire, the second single wire, the third single wire and the seventh single wire does not exceed 0.1 mm, and the maximum wire diameter difference between the fourth single wire, the fifth single wire, the sixth single wire and the eighth single wire does not exceed 0.1 mm.

[0011] According to the embodiments disclosed herein, the seventh single wire, which is wound outside the ring and located on the first side of the first magnetic ring, the eighth single wire, and the ninth single wire located on the second side of the first magnetic ring are twisted together to form an eighth twisted wire outside the first magnetic ring.

[0012] According to the embodiments disclosed herein, the eighth twisted wire and the third twisted wire sandwich the fourth twisted wire, the fifth twisted wire, the sixth twisted wire, and the seventh twisted wire.

[0013] Based on the above, the coil structure of the present invention uses three (or more) copper wires twisted in parallel to reduce the stress and hardness of the winding, effectively reducing the difficulty of welding and pin winding operations, and increasing the current carrying capacity, thereby expanding the power application range. Simple Explanation of the Diagram

[0014] To make the above and other features, advantages and embodiments of the present invention more readily understood, the accompanying drawings are described below: Figure 1 is a schematic diagram of a coil structure applied to Ethernet power supply according to an embodiment of the present invention; Figure 2 is a schematic diagram of the circuit diagram corresponding to the coil structure applied to Ethernet power supply according to an embodiment of the present invention; and Figures 3 to 8 are schematic diagrams illustrating the winding of a coil structure applied to Ethernet power supply according to an embodiment of the present invention. Implementation

[0015] The following disclosure provides numerous different embodiments or examples for implementing various features of the provided invention. The embodiments of components and configurations described below are merely examples and are not intended to be limiting. Furthermore, for simplicity and clarity, reference numerals and / or designations are repeated in the examples, but this does not itself limit the relationship between the various embodiments and / or components discussed.

[0016] Figure 1 is a schematic diagram of a coil structure 100 for Ethernet power supply according to an embodiment of the present invention. Figure 2 is a circuit diagram corresponding to the coil structure 100 for Ethernet power supply according to an embodiment of the present invention. Figures 3 to 8 further illustrate the winding schematic diagrams of the coil structure 100 according to an embodiment of the present invention. In the following text, the winding method of the coil structure 100 of the present invention can be better understood by referring to Figure 1 together with the circuit diagram shown in Figure 2 and the winding schematic diagrams shown in Figures 3 to 8.

[0017] As shown in Figure 1, in the completed coil structure 100, a first stranded wire 101 and a second stranded wire 102 are wound on a first magnetic ring C1, and a third stranded wire 103 is wound on a second magnetic ring C2. The wires extending beyond the first magnetic ring C1 include a fourth stranded wire 104, a fifth stranded wire 105, a sixth stranded wire 106, a seventh stranded wire 107, and an eighth stranded wire 108. In an embodiment of the invention, the eighth stranded wire 108 is positioned on the outermost side of all the strands extending beyond the first magnetic ring C1, such that the connecting segment between the root of the eighth stranded wire 108 and the root of the third stranded wire 103 sandwiches the roots of all the copper wires on the primary side (i.e., the first magnetic ring C1). This improves the coupling between the primary and secondary sides, thereby enhancing the high-frequency characteristics of the product.

[0018] In an embodiment of the present invention, the size of the first magnetic ring C1 is larger than the size of the second magnetic ring C2. Specifically, the first magnetic ring C1 has a larger cross-sectional area, which reduces the number of turns of the first stranded wire 101 and the second stranded wire 102 wound around the first magnetic ring C1, thereby shortening the length of the conductor through which the current flows. In one example, the dimensions of the first magnetic ring C1 are an outer diameter of 6.6 mm, an inner diameter of 2.5 mm, and a height of 3.3 mm; the dimensions of the second magnetic ring C2 are an outer diameter of 3.05 mm, an inner diameter of 1.78 mm, and a height of 1.52 mm.

[0019] As shown in Figure 2, the circuit diagram corresponding to coil structure 100 includes a first magnetic ring C1, a second magnetic ring C2, a first-side (primary-side) single-wire group 110, and a second-side (secondary-side) single-wire group 120. The first-side single-wire group 110 includes a first single wire R1, a second single wire R2, a third single wire R3, a fourth single wire B1, a fifth single wire B2, and a sixth single wire B3. The second-side single-wire group 120 includes a seventh single wire N, an eighth single wire G, and a ninth single wire R4.

[0020] The first single wire R1, the second single wire R2, and the third single wire R3 of the first single wire group 110 are twisted together with the seventh single wire N of the second single wire group 120 to form the first twisted wire 101 shown in Figure 1. As shown in the enlarged schematic diagram of the first twisted wire 101 in Figure 3, the first twisted wire 101 is formed by twisting the first single wire R1, the second single wire R2, the third single wire R3, and the seventh single wire N together. The first single wire R1, the second single wire R2, the third single wire R3, and the seventh single wire N can have at least two different wire diameters to improve the flexibility of wire selection for different power designs.

[0021] In an embodiment of the present invention, the number of strands in the first stranded wire 101 is approximately 16 to 18 per inch. In an embodiment of the present invention, the maximum diameter difference between the individual wires in the first stranded wire 101 does not exceed 0.1 mm to prevent breakage of the individual wires when they are twisted together. In one example, the diameter of the first single wire R1 is 0.142 mm, the diameters of the second single wire R2 and the third single wire R3 are 0.127 mm, and the diameter of the seventh single wire N is 0.1 mm. The maximum diameter difference between the four is 0.042 mm, not exceeding 0.1 mm. In an embodiment of the present invention, the first single wire R1, the second single wire R2, and the third single wire R3 are red copper wires, and the seventh single wire N is a gold copper wire. It should be understood that the diameter and color of the individual wires in the first stranded wire 101 can be varied according to actual application requirements, and the present invention is not limited thereto.

[0022] The fourth single wire B1, the fifth single wire B2, and the sixth single wire B3 of the first single wire group 110 are twisted together with the eighth single wire G of the second single wire group 120 to form the second twisted wire 102 shown in Figure 1. As shown in the enlarged schematic diagram of the second twisted wire 102 in Figure 4, the second twisted wire 102 is formed by twisting the fourth single wire B1, the fifth single wire B2, the sixth single wire B3, and the eighth single wire G together. The fourth single wire B1, the fifth single wire B2, the sixth single wire B3, and the eighth single wire G can have at least two different wire diameters to improve the flexibility of wire selection for different power designs.

[0023] In an embodiment of the present invention, the number of strands in the second stranded wire 102 is approximately between 16 and 18 per inch. In an embodiment of the present invention, the maximum diameter difference between the individual wires in the second stranded wire 102 does not exceed 0.1 mm to prevent breakage of the individual wires when they are twisted together. In one example, the diameter of the fourth wire B1 is 0.142 mm, the diameters of the fifth and sixth wires B2 and B3 are 0.127 mm, and the diameter of the eighth wire G is 0.1 mm. The maximum diameter difference between the four is 0.042 mm, not exceeding 0.1 mm. In an embodiment of the present invention, the fourth wire B1, the fifth wire B2, and the sixth wire B3 are blue copper wires, and the eighth wire G is a green copper wire. It should be understood that the diameter and color of the individual wires in the second stranded wire 102 can be varied according to actual application requirements, and the present invention is not limited thereto.

[0024] Referring to Figure 5, after obtaining the first twisted wire 101 and the second twisted wire 102, the first twisted wire 101 and the second twisted wire 102 are wound around the first magnetic ring C1 in an alternating but non-overlapping manner. The first twisted wire 101 and the second twisted wire 102 wound around the first magnetic ring C1 are evenly distributed from the winding starting point O1 to the winding ending point E1, with a total angle of approximately 60° to 300°. In a preferred embodiment, the first twisted wire 101 and the second twisted wire 102 wound around the first magnetic ring C1 are evenly distributed with a total angle of approximately 300° (i.e., occupying approximately 5 / 6 of the ring body of the first magnetic ring C1). This can reduce the uneven magnetic flux intensity generated by the first twisted wire 101 and the second twisted wire 102 in different regions of the first magnetic ring C1, which leads to problems such as electromagnetic radiation, leakage flux, or stray capacitance between the primary and secondary windings. Therefore, an appropriate angle distribution design is crucial.

[0025] In an embodiment of the present invention, each turn of wire substantially wound around the first magnetic ring C1 is a stranded wire, rather than being wound around the first magnetic ring C1 in a single wire or in a loose form. "Substantially wound" means that at least one turn is wound around the first magnetic ring C1.

[0026] A portion of the first twisted wire 101 and the second twisted wire 102 that extend beyond the first magnetic ring C1 (e.g., the beginning and end of each single wire in the first twisted wire 101 and the second twisted wire 102) are free segments. That is, the first twisted wire 101 is restored to the untwisted form of the first single wire R1, the second single wire R2, the third single wire R3, and the seventh single wire N, while the second twisted wire 102 is restored to the untwisted form of the fourth single wire B1, the fifth single wire B2, the sixth single wire B3, and the eighth single wire G. In the following example, the free segments located on the first side S1 of the first magnetic ring C1 will have a "+" sign added after the label, and the free segments located on the second side S2 of the first magnetic ring C1 will have a "-" sign added after the label. The first side S1 of the first magnetic ring C1 is the frontal view shown in Figure 5, and the second side S2 of the first magnetic ring C1 is the opposite side of the first side S1.

[0027] The free segments of the first twisted wire 101 include the first single wire R1+, the second single wire R2+, the third single wire R3+, and the seventh single wire N+ located on the first side S1 of the first magnetic ring C1, and the first single wire R1-, the second single wire R2-, the third single wire R3-, and the seventh single wire N- located on the second side S2 of the first magnetic ring C1. The free segments of the second twisted wire 102 include the fourth single wire B1+, the fifth single wire B2+, the sixth single wire B3+, and the eighth single wire G+ located on the first side S1 of the first magnetic ring C1, and the fourth single wire B1-, the fifth single wire B2-, the sixth single wire B3-, and the eighth single wire G- located on the second side S2 of the first magnetic ring C1.

[0028] The fourth single wire B1+ located on the first side S1 of the first magnetic ring C1, the second single wire R2- located on the second side S2 of the first magnetic ring C1, and the third single wire R3- located on the second side S2 of the first magnetic ring C1 are twisted together to form the fourth twisted wire 104 shown in FIG6 outside the first magnetic ring C1. In this embodiment, the number of twisted wires in the fourth twisted wire 104 is 0 to 26 strands per inch. The number of twisted wires is "0 strands per inch", which means that the fourth single wire B1+, the second single wire R2-, and the third single wire R3- in the fourth twisted wire 104 are in an untwisted state in application.

[0029] The fifth single wire B2+, the sixth single wire B3+, and the first single wire R1- located on the first side S1 of the first magnetic ring C1, and the second single wire R1- located on the second side S2 of the first magnetic ring C1 are twisted together to form the fifth twisted wire 105 shown in FIG. 6 outside the first magnetic ring C1. In this embodiment, the number of twisted wires in the fifth twisted wire 105 is 0 to 26 twists per inch. The number of twisted wires is "0 twists per inch", which means that the fifth single wire B2+, the sixth single wire B3+, and the first single wire R1- in the fifth twisted wire 105 are in an untwisted state in application.

[0030] The first single wire R1+, the second single wire R2+, and the third single wire R3+ located on the first side S1 of the first magnetic ring C1 are twisted together to form the sixth stranded wire 106 shown in FIG. 6 outside the first magnetic ring C1. In this embodiment, the number of strands in the sixth stranded wire 106 is 0 to 26 strands per inch. Wherein, the number of strands per inch is "0 strands" means that the first single wire R1+, the second single wire R2+, and the third single wire R3+ in the sixth stranded wire 106 are in an untwisted state in application.

[0031] The fourth single wire B1-, the fifth single wire B2-, and the sixth single wire B3- located on the second side S2 of the first magnetic ring C1 are twisted together to form the seventh twisted wire 107 shown in FIG. 6 outside the first magnetic ring C1. In this embodiment, the number of twisted wires in the seventh twisted wire 107 is 0 to 26 twists per inch. Wherein, the number of twisted wires is "0 twists per inch" means that the fourth single wire B1-, the fifth single wire B2-, and the sixth single wire B3- in the seventh twisted wire 107 are in an untwisted state.

[0032] The seventh single wire N+ located on the first side S1 of the first magnetic ring C1, the eighth single wire G- located on the second side S2 of the first magnetic ring C1, and one end of the ninth single wire R4 are twisted together to form the eighth twisted wire 108 shown in FIG6 outside the first magnetic ring C1. In this embodiment, the number of twisted wires in the eighth twisted wire 108 is 16 to 18 per inch.

[0033] The eighth single wire G+ located on the first side S1 of the first magnetic ring C1, the seventh single wire N- located on the second side S2 of the first magnetic ring C1, and the other ends of the ninth single wire R4 are twisted together to form the third twisted wire 103 shown in FIG6 outside the first magnetic ring C1. In this embodiment, the number of twisted wires in the third twisted wire 103 is 16 to 18 per inch.

[0034] Referring to Figure 7, after the first magnetic ring C1 is wound, the third strand 103, formed by twisting the other ends of the eighth single wire G+, the seventh single wire N-, and the ninth single wire R4, extends from the winding endpoint E1 of the first magnetic ring C1 to the second magnetic ring C2 and is wound around the second magnetic ring C2. In an embodiment of the present invention, both the first magnetic ring C1 and the second magnetic ring C2 are 360° loops, and the third strand 103 wound around the second magnetic ring C2 extends from the winding starting point O2 to the winding endpoint E2, with a total uniform distribution of approximately 60° to 360°. In a preferred embodiment, the third strand 103 wound around the second magnetic ring C2 is uniformly distributed for approximately 270° (i.e., approximately 3 / 4 of the loop of the second magnetic ring C2), which can reduce the uneven magnetic flux intensity generated by the third strand 103 in different areas of the second magnetic ring C2, thus mitigating problems such as electromagnetic radiation and stray capacitance. Therefore, an appropriate angle distribution design is crucial.

[0035] In an embodiment of the present invention, each turn of wire substantially wound around the second magnetic ring C2 is a stranded wire, rather than being wound around the second magnetic ring C2 in a single wire or loose form. "Substantially wound" means that at least one turn is wound around the second magnetic ring C2.

[0036] Please refer to Figure 8. After winding the second magnetic ring C2, cut off the excessively long portion of the eighth strand 108 and solder it to short-circuit one end of the seventh single wire N+, the eighth single wire G-, and the ninth single wire R4. Finally, apply glue to cover the solder joints. At this point, the winding of the coil structure 100 is roughly complete.

[0037] In some embodiments, the fourth twisted wire 104 and the fifth twisted wire 105 may be twisted together to form a central twisted wire 109, and the number of twisted wires in the central twisted wire 109 is 0 to 26 per inch. The number of twisted wires is "0 per inch", which means that the fourth twisted wire 104 and the fifth twisted wire 105 are in an untwisted state as shown in FIG1.

[0038] In an embodiment of the present invention, after the first magnetic ring C1 and the second magnetic ring C2 are wound, there is a distance d between them, and this distance d is less than or equal to 2.5 mm.

[0039] Compared to the drawbacks of a single thick copper wire, this invention effectively reduces product temperature rise by lowering the copper wire resistance, thereby increasing application power. This invention employs a method of parallel winding of three (or more) strands to increase the cross-sectional area of ​​the copper wire. Furthermore, without compromising product performance requirements, a magnetic ring with a larger cross-section is selected as the first magnetic ring, thereby reducing the length of the copper wire through which current flows by reducing the number of windings. This effectively reduces reflection and insertion losses in the coil structure, meeting the high-frequency characteristics and high-power requirements of the product.

[0040] In summary, compared to conventional single-core thick copper wire, the coil structure of this invention uses three (or more) copper wires twisted in parallel to reduce winding stress and stiffness, effectively reducing the difficulty of welding and lead winding operations. It also enables automated winding onto the magnetic ring, ensuring consistent product quality. Furthermore, three (or more) copper wires increase current carrying capacity, expanding the range of power applications. Depending on the designed power, each copper wire can contain different diameters, provided the difference is less than the maximum wire diameter, thus increasing product flexibility.

[0041] Although the present invention has been disclosed above with various embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make some modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

[0042] 100: Coil Structure 101: First strand 102: Second twisted wire 103: Third strand 104: Fourth strand 105: Fifth strand 106: Sixth twisted wire 107: Seventh twisted wire 108: Eighth strand 109: Central stranded wire 110: First side single line group 120: Second side single line group R1, R1+, R1-: First single line R2, R2+, R2-: Second single line R3, R3+, R3-: Third single line B1, B1+, B1-: Fourth single line B2, B2+, B2-: Fifth single line B3, B3+, B3-: Sixth single line R4: Ninth Single Line C1: First magnetic ring C2: Second magnetic ring d: distance E1, E2: End point of winding G, G+, G-: Eighth single line N,N+,N-: Seventh single line O1, O2: Entanglement start point S1: First side S2: Second side

Claims

1. A coil structure for power supply in Ethernet networks, comprising: a first magnetic ring having a first side and a second side; a second magnetic ring; a first-side single-wire group including a first single wire, a second single wire, a third single wire, a fourth single wire, a fifth single wire, and a sixth single wire; and a second-side single-wire group including a seventh single wire, an eighth single wire, and a ninth single wire, wherein: The first, second, third, and seventh single wires are twisted together to form a first twisted wire; the fourth, fifth, sixth, and eighth single wires are twisted together to form a second twisted wire; and the first and second twisted wires are interlaced but not overlapping, wound around the first magnetic ring. The seventh single wire, which is outside the ring and located on the second side of the first magnetic ring, the eighth single wire, which is outside the ring and located on the first side of the first magnetic ring, and the ninth single wire are twisted together outside the first magnetic ring to form a third twisted wire; and the third twisted wire extends from the first magnetic ring to the second magnetic ring and is wound around the second magnetic ring. The fourth single wire, which is outside the ring and located on the first side of the first magnetic ring, the second single wire, and the third single wire, which are located on the second side of the first magnetic ring, are twisted together to form a fourth twisted wire outside the first magnetic ring. The fifth and sixth single wires, which are outside the ring and located on the first side of the first magnetic ring, and the first single wire, which is located on the second side of the first magnetic ring, are twisted together to form a fifth twisted wire outside the first magnetic ring; the first, second, and third single wires, which are outside the ring and located on the first side of the first magnetic ring, are twisted together to form a sixth twisted wire outside the first magnetic ring; and the fourth, fifth, and sixth single wires, which are outside the ring and located on the second side of the first magnetic ring, are twisted together to form a seventh twisted wire outside the first magnetic ring.

2. The coil structure as described in claim 1, wherein the fourth strand and the fifth strand are twisted together to form a central strand, the central strand having a number of strands from 0 to 26 per inch.

3. The coil structure as described in claim 1, wherein the cross-sectional area of ​​the first magnetic ring is greater than the cross-sectional area of ​​the second magnetic ring.

4. The coil structure as described in claim 1, wherein after the third stranded wire extends from the first magnetic ring to the second magnetic ring and the winding is completed, the distance between the first magnetic ring and the second magnetic ring is less than or equal to 2.5 mm.

5. The coil structure as described in claim 1, wherein the first magnetic ring is a 360° ring, and the first strand and the second strand are distributed over a total of 300° from a winding start point to a winding end point on the first magnetic ring.

6. The coil structure as described in claim 1, wherein the second magnetic ring is a 360° ring and the third stranded wire is distributed over a total of 270° from a winding start point to a winding end point on the second magnetic ring.

7. The coil structure as described in claim 1, wherein the first single wire, the second single wire, the third single wire, and the seventh single wire in the first stranded wire have at least two different wire diameters, and the fourth single wire, the fifth single wire, the sixth single wire, and the eighth single wire in the second stranded wire have at least two different wire diameters.

8. The coil structure as described in claim 7, wherein the maximum wire diameter difference between the first single wire, the second single wire, the third single wire and the seventh single wire does not exceed 0.1 mm, and the maximum wire diameter difference between the fourth single wire, the fifth single wire, the sixth single wire and the eighth single wire does not exceed 0.1 mm.

9. The coil structure as claimed in claim 1, wherein the seventh single wire, the eighth single wire, and the ninth single wire, which are wound outside the ring and located on the first side of the first magnetic ring, are twisted together to form an eighth strand outside the first magnetic ring.

10. The coil structure as described in claim 9, wherein the eighth strand and the third strand sandwich the fourth strand, the fifth strand, the sixth strand and the seventh strand therein.

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