A multi-layer integrated winding method of printed circuit board leitz coil

Abstract

This invention discloses a multilayer integrated winding method for Litz coils on printed circuit boards, belonging to the field of power electronics technology. The invention includes: providing a PCB with at least four conductive layers; forming input / output cutout areas at the edge of the PCB; dividing multiple parallel conductors constituting one turn of the coil into multiple groups, each group starting from the same layer; each conductor sequentially traversing all conductive layers through vias in a predetermined order, extending circumferentially at a predetermined angle in each layer, so that the current paths of all conductors are uniformly distributed in a direction perpendicular to the coil plane; the input and output ends of all parallel conductors are led out from the cutout areas. This invention increases the number of PCB layers available for a single-turn coil to 4, 6, or more, significantly improving current carrying capacity; the input / output cutouts are concentrated in small-angle areas, reducing the end area occupied; each conductor only needs to undergo a minimum number of position exchanges within the cross-sectional area, reducing wiring complexity and making it suitable for the integrated design of magnetic components.

Description

Technical Field

[0001] This invention belongs to the field of power electronics technology, specifically relating to a multi-layer integrated winding method for Litz coils on printed circuit boards, applicable to the planar and integrated design of magnetic components such as high-frequency transformers, inductors, and wireless power transmission coils. Background Technology

[0002] As power electronics technology develops towards higher frequencies and higher power densities, planar magnetic components (such as planar transformers and planar inductors) are widely used due to their advantages such as low height and ease of integration. Under high-frequency operating conditions, in order to reduce eddy current losses in the windings, a Litz wire structure is often used, which involves winding multiple strands of fine wires in parallel to ensure that the current is evenly distributed across the cross-section of the wires.

[0003] Implementing Litz coils in printed circuit boards has become an important technological direction. In the prior art, US patent application US20250210246A1 discloses a Litz coil structure for a printed circuit board transformer. Specifically, Figure 1 The overall structure of the PCB Litz coil in this patent is shown, with solid lines representing the first layer and dashed lines representing the second layer. Figure 2 The patent demonstrates three Figure 1 The diagram shows the connection method of the coils connected in series in a 6-layer PCB. Figure 3 The patent demonstrates a structure in which a 5-turn coil is wound within a 4-layer PCB. In this structure, each turn of the coil can utilize a maximum of two PCB layers.

[0004] In addition, a similar planar winding structure was proposed in the paper "A Winding Structure of Air-Core Planar Inductors for Reducing High-Frequency Eddy Currents" published by Orikawa et al. in IEEE Transactions on Industry Applications. Figure 4 The paper demonstrates the structure of an 8-turn coil wound within a two-layer PCB.

[0005] The common feature of the aforementioned prior art is that a maximum of two PCB conductive layers can be used to wind one turn of the coil, and each turn of the coil needs to undergo at least three position exchanges within the cross-sectional area (i.e., from the inside to the outside of the coil or vice versa, and inter-layer switching). This structure has the following disadvantages:

[0006] 1. Limited current carrying capacity: Since a single-turn coil can only utilize two layers of PCB, the total cross-sectional area of ​​the coil is limited under a given PCB thickness and copper foil thickness, making it difficult to carry large currents.

[0007] 2. Excessive end area: In order to achieve position exchange, the coil requires a large additional area at the end, which is not conducive to improving power density.

[0008] 3. Insufficient flexibility: It is difficult to achieve uniform current distribution of a single-turn coil in PCBs with more layers, which limits its application in higher power level scenarios.

[0009] Therefore, how to increase the number of PCB layers available for a single-turn coil and simplify the number of position exchanges while making full use of the multi-layer PCB area and ensuring uniform distribution of current cross-section has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0010] The purpose of this invention is to provide a multi-layer integrated winding method for Litz coils on printed circuit boards, so as to overcome the defects of the prior art that a single-turn coil can only utilize a maximum of two PCB layers and requires multiple position exchanges, thereby achieving higher current carrying capacity, smaller end area, and more flexible multi-layer winding.

[0011] To achieve the above objectives, the present invention adopts the following technical solution: a multilayer integrated winding method for Litz coils on printed circuit boards, comprising the following steps:

[0012] Provide a printed circuit board having at least four conductive layers;

[0013] At least one inlet / outlet cut-out area is formed at the edge of the printed circuit board, the cut-out area extending inward from the edge;

[0014] The multiple parallel wires that make up a coil are divided into multiple groups, with each group of wires starting from the same conductive layer.

[0015] Each wire passes through the via in a predetermined order and traverses all conductive layers sequentially, extending circumferentially at a predetermined angle in each layer, so that the current path of all wires is uniformly distributed in a direction perpendicular to the coil plane.

[0016] The input and output terminals of all parallel wires are led out from the cut-out area to connect to external circuitry.

[0017] Furthermore, the entry and exit cut-out regions are configured such that each parallel conductor undergoes only one position exchange within the cross-sectional area throughout its entire path from the starting layer to the ending layer.

[0018] Furthermore, each of the multiple parallel wires, during its traversal of each conductive layer, sequentially passes through the first layer, the second layer, and up to the Nth layer, before returning to the first layer or another starting layer, where N is an even number greater than 2.

[0019] Furthermore, in each layer, the wire starts from a radial position in that layer, rotates circumferentially by an angle of 2π·M / L, and then passes through a via to the adjacent layer, changing its radial position in the adjacent layer, where M is the total number of coil turns and L is the total number of conductive layers.

[0020] Furthermore, the total angle of the inlet / outlet cut area is less than 180 degrees, preferably 120 degrees or less.

[0021] Furthermore, when the coil has a single layer or 3 turns, the depth of the cut area is shared by the two conductive layers, and the sum of the depths of the two cut layers is 2 / 3 of the width of the single-layer coil.

[0022] Furthermore, the number of conductive layers in the printed circuit board is 4, 6, or 8 layers, or any other even number of layers.

[0023] Furthermore, the method is used to implement Litz coil winding with an arbitrary integer number of turns on an even-numbered printed circuit board.

[0024] The present invention also provides a Litz coil for a printed circuit board, which is wound using the above method.

[0025] The present invention also provides a power electronic device including a transformer, an inductor or a wireless power transmission coil, wherein the transformer, inductor or wireless power transmission coil comprises at least one of the above-described printed circuit board Litz coils.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. Improved current carrying capacity: This invention significantly increases the total cross-sectional area of ​​the conductors by distributing the parallel wires of the single-turn coil in 4, 6 or more layers of PCB, thereby improving the current carrying capacity of the coil and making it suitable for higher power applications.

[0028] 2. Reduced end area: The design of the inlet and outlet wire cut-out area of ​​this invention concentrates all the lead wires in a small arc segment (such as 120°), avoiding the large angle (180° or even 360°) lead-out area required by traditional solutions, effectively reducing the extra area occupied by the coil end, which is conducive to improving the overall power density.

[0029] 3. Reduce the number of position exchanges: Through optimized inter-layer traversal order and cutout design, this invention requires each wire to undergo only the fewest position exchanges within the cross-sectional area throughout the entire path. Compared with the three exchanges in the prior art, this simplifies the wiring structure, reduces process complexity, and further shortens the wire length and reduces DC resistance.

[0030] 4. High flexibility: The method of this invention can be applied to PCBs with any even number of layers (4, 6, 8 layers and above) and can realize coil winding with any integer number of turns, which has strong versatility and scalability. Attached Figure Description

[0031] Figure 1 This is a structural diagram of the PCB Litz coil in the prior art US20250210246A1 (solid lines represent the first layer, and dashed lines represent the second layer).

[0032] Figure 2 This is a schematic diagram of the connection method of three coils connected in series in a 6-layer PCB in the prior art US20250210246A1.

[0033] Figure 3 This is a schematic diagram of the structure of a 5-turn coil wound inside a 4-layer PCB in the prior art US20250210246A1.

[0034] Figure 4 This is a schematic diagram of the structure of an 8-turn coil wound inside a two-layer PCB, as described in the paper by Orikawa et al., which is an existing technology.

[0035] Figure 5 This is a comparative diagram of the input and output port designs of the present invention and the prior art (the left side is the prior art design, and the right side is the design of the present invention).

[0036] Figure 6 This is a schematic diagram illustrating the application of the inlet / outlet cuts in a 2-layer, 3-turn coil in an embodiment of the present invention (showing the case where the cuts are distributed in two layers).

[0037] Figure 7 This is a schematic diagram of the inlet / outlet cut design for different numbers of turns (1 turn, 2 turns, 3 turns) in an embodiment of the present invention.

[0038] Figure 8 This is a schematic diagram of the inlet / outlet cut design in an embodiment of the present invention for 1 turn, 2 layers, and different numbers of wires (8 strands, 16 strands).

[0039] Figure 9 This is a schematic diagram of the different distribution of ports in the two layers (4 / 4, 6 / 2, 8 / 0) when the input / output wire cut-out design is used for a 2-turn, 2-layer coil in an embodiment of the present invention.

[0040] Figure 10 This is a schematic diagram of a multi-layer integrated structure in an embodiment of the present invention, showing the specific routing path for winding a coil using a 4-layer PCB.

[0041] Figure 11 This is a schematic diagram of a multilayer integrated structure in an embodiment of the present invention, wherein (a) is a 4-layer winding with one turn, and (b) is a 6-layer winding with one turn. Detailed Implementation

[0042] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0043] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0044] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0045] Example 1: Design of Inlet / Outlet Cutouts

[0046] like Figure 5 As shown on the right, one of the core improvements of this invention lies in the design of the input and output ports. Unlike existing technologies where the input and output ports are located along the entire arc of the coil edge (e.g., ...), this invention... Figure 5 Unlike the one shown on the left, this invention cuts a narrow area (cutout) inward from the edge of the printed circuit board, and the input and output ends of all parallel wires are concentrated and led out from this cutout area.

[0047] The total angle of the cut area is much smaller than the 180° or 360° required by existing technologies. In a preferred embodiment, the cut area corresponds to a 120° arc segment. This design allows each conductor to complete all outgoings with only a minimal number of position exchanges within the cross-sectional area, whereas existing technologies require at least three exchanges.

[0048] Figure 6 This demonstrates the specific application of this cut design in a 2-layer, 3-turn coil. The cut can be distributed across two layers, each cutting into 1 / 3 of the coil width, or concentrated in one layer, cutting into 2 / 3 of the coil width. As long as the total cut depth on both layers is 2 / 3 of the width of a single-layer coil, it can be ensured that each wire is cut and cut only once.

[0049] Figures 7 to 9 This further demonstrates the flexible application of the cut design under different numbers of turns (1, 2, 3 turns), different numbers of parallel lines (8 strands, 16 strands), and different cut depth distributions (4 / 4, 6 / 2, 8 / 0).

[0050] Example 2: Multi-layer integrated winding structure (4 layers)

[0051] like Figure 10 and Figure 11 As shown in (a), this embodiment demonstrates a specific method for winding a one-turn coil using a four-layer PCB. Wherein, Figure 10 The routing paths and via connections for each layer of conductors are shown in detail. Figure 11 (a) shows the overall layout of the 4-layer structure in a more simplified way.

[0052] In this embodiment, a total of 40 wires are connected in parallel. These wires are divided into 4 groups of 10 wires each, starting from the 1st layer (red), the 2nd layer (orange), the 3rd layer (green), and the 4th layer (blue), respectively.

[0053] Taking the red wire group starting from the first layer as an example, its routing path is as follows:

[0054] 1. First layer: Enter from the input end of the right-side cut area, rotate a certain angle counterclockwise (or clockwise) to reach the inside of the coil.

[0055] 2. Layer 1 → Layer 2: Switch to Layer 2 through the 10 vias evenly distributed inside the coil.

[0056] 3. Second layer: On the second layer, the wire starts from the inside and rotates around the circumference by about 2π·M / L (for a single-turn coil, M=1, L=4, which is 90°) to reach the outside of the coil, and then changes to the third layer through the via on the outside.

[0057] 4. Layer 3: On the third layer, the wire starts from the outside, rotates around the circumference by about 2π·M / L, reaches the inside of the coil, and changes to the fourth layer through the through hole on the inside.

[0058] 5. 4th layer: On the 4th layer, the wire starts from the inside, rotates around the circumference by about 2π·M / L, reaches the outside of the coil, and returns to the 1st layer through the via on the outside.

[0059] 6. Return to Layer 1: On Layer 1, the wire continues to rotate from the outside to the remaining angle, and finally exits from the same position as the input end (cut area) to complete one turn of the coil.

[0060] The wires of other colors (groups) follow the exact same traversal order, differing only in the starting layer. Through this path design of "traversing all layers and rotating 2π·M / L per layer", the current in all 40 wires is uniformly distributed in the direction perpendicular to the coil plane (i.e., between layers).

[0061] It should be noted that "layer 1" to "layer 4" in the above description only indicate the logical order of the traces, not a limitation on their physical location. In actual PCBs, these logical layers can correspond arbitrarily to physical layers, as long as the continuity of the layer order is maintained.

[0062] Example 3: Multi-layer integrated winding structure (6 layers)

[0063] like Figure 11 As shown in (b), this embodiment demonstrates the structure of a single-turn coil wound using a 6-layer PCB. The principle is the same as in Embodiment 2: the wires traverse all 6 layers sequentially in a predetermined order, rotating approximately 2π·M / L per layer (for a single-turn coil, M=1, L=6, which is 60°) (or the angle can be adjusted according to the specific design), ultimately distributing evenly across the 6 layers. As the number of layers increases, the rotation angle of each layer decreases accordingly, but the overall principle remains the same.

[0064] Example 4: Application of multi-layer, multi-turn coils

[0065] The method of this invention is not limited to single-turn coils, but can be extended to multi-turn coils. For example, in Figure 2 Based on the structure shown, the single-turn multi-layer coil of this invention can be used as the basic unit to realize a multi-turn coil through series connection. Since the input and output wire cuts are concentrated in a small angle region, the series connection between multiple coil units becomes very simple and does not require additional end area. For multi-turn coils, the rotation angle of each layer is 2π·M / L, where M is the total number of turns and L is the total number of layers.

[0066] Example 5: Generalization of Arbitrary Even Number of Layers and Arbitrary Number of Turns

[0067] Based on the teachings of the above embodiments, those skilled in the art will readily understand that the method of the present invention can be extended to PCBs with any even number of layers (e.g., 8 layers, 10 layers, etc.), simply by adjusting the rotation angle of each layer accordingly (2π·M / L, where M is the total number of turns and L is the total number of layers, and further adjusted appropriately according to the specific design). Furthermore, by connecting multiple single-turn multi-layer coil units in series, coils with any integer number of turns can be achieved. Therefore, the present invention possesses extremely high flexibility and versatility.

[0068] The multilayer integrated winding method for Litz coils on printed circuit boards provided by this invention can be widely applied to the design of planar transformers and planar inductors in fields such as high-frequency switching power supplies, DC-DC converters, on-board chargers, communication power supplies, server power supplies, and wireless power transmission equipment, which helps to improve power density and conversion efficiency.

[0069] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A multi-layer integrated winding method of printed circuit board (PCB) air-core transformer, characterized in that, Includes the following steps: Provide a printed circuit board having at least four conductive layers; At least one inlet / outlet cut-out area is formed at the edge of the printed circuit board, the cut-out area extending inward from the edge; The multiple parallel wires that make up a coil are divided into multiple groups, with each group of wires starting from the same conductive layer. Each wire passes through the via in a predetermined order and traverses all conductive layers sequentially, extending circumferentially at a predetermined angle in each layer, so that the current path of all wires is uniformly distributed in a direction perpendicular to the coil plane. The input and output terminals of all parallel wires are led out from the cut-out area to connect to external circuitry.

2. The multilayer integrated winding method of printed circuit board leitz coils according to claim 1, characterized in that, The entry and exit cut-out regions are configured such that each parallel conductor undergoes only one position exchange within the cross-sectional area throughout its entire path from the starting layer to the ending layer.

3. The multilayer integrated winding method of printed circuit board (PCB) air-core inductor according to claim 1, wherein, Each of the multiple parallel wires, in its traversal of each conductive layer, sequentially passes through the first layer, the second layer, up to the Nth layer, and then returns to the first layer or another starting layer, where N is an even number greater than 2.

4. The multilayer integrated winding method of printed circuit board (PCB) air-core inductor according to claim 1, wherein, In each layer, the wire starts from a radial position of the layer, rotates circumferentially by an angle of 2π·M / L, and then passes through a via to the adjacent layer, changing its radial position in the adjacent layer, where M is the total number of coil turns and L is the total number of conductive layers.

5. The multilayer integrated winding method of printed circuit board (PCB) air-core inductor according to claim 1, wherein, The total angle of the inlet and outlet cut areas is less than 180 degrees.

6. The multilayer integrated winding method of printed circuit board (PCB) air-core inductor according to claim 5, wherein, When the coil has a single layer or 3 turns, the depth of the cut area is shared by the two conductive layers, and the sum of the depths of the two cuts is 2 / 3 of the width of the single coil layer.

7. The multilayer integrated winding method of printed circuit board (PCB) air-core inductor according to claim 1, wherein, The number of conductive layers on the printed circuit board is 4, 6, or 8, or any other even number of layers.

8. The multilayer integrated winding method of printed circuit board (PCB) air-core inductor according to claim 1, wherein, The method is used to implement Litz coil winding with an arbitrary integer number of turns on a printed circuit board with an even number of layers.

9. A Litz coil on a printed circuit board, characterized in that, It is wound using the method described in any one of claims 1-8.

10. A power electronic device comprising a transformer, an inductor, or a wireless power transmission coil, characterized in that, The transformer, inductor, or wireless power transfer coil includes at least one printed circuit board Litz coil as described in claim 9.

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