PCB air core inductor, design method thereof and switching power supply

Abstract

The application provides a PCB air-core inductor, a design method thereof and a switching power supply, wherein the design method comprises the following steps: determining the winding turns, winding width and winding thickness of the PCB air-core inductor, and designing the number of winding layers in the PCB and the width and thickness of the winding metal in each winding layer according to the winding turns, winding width and winding thickness; sequentially connecting the winding metal in each winding layer in series to form a PCB winding, wherein the PCB winding is embedded in an insulating support body composed of insulating medium; forming a metal shielding body around the PCB winding, wherein the metal shielding body and the PCB winding are separated by insulating medium; and the metal shielding body comprises four circumferential shielding walls, one upper shielding wall and one lower shielding wall, and the beginning and end of the PCB winding are connected to the input terminal and the output terminal respectively and lead out through the corresponding circumferential shielding walls. The application solves the problems of poor magnetic shielding performance and large high-frequency loss of the PCB planar inductor in the prior art.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, and in particular to a PCB air-core inductor and its design method, and a switching power supply. Background Technology

[0002] With the widespread application of third-generation semiconductor devices (such as gallium nitride devices), the operating frequency of switching power supplies is constantly increasing, reaching the MHz level and above. High-frequency operation brings advantages such as increased power density and smaller passive component size, but it also places more stringent requirements on magnetic components. Traditional wire-wound inductors or powder core inductors suffer from problems such as high eddy current losses, difficult thermal management, difficulty in further reducing size, and severe electromagnetic interference (EMI) generated by high-frequency magnetic fields at high frequencies.

[0003] Printed circuit board (PCB) planar inductors have attracted attention due to their ease of integration, high consistency, and suitability for automated production. However, PCB planar inductors are mostly simple planar spiral structures with an open magnetic field distribution. Under high frequency and high current, they generate strong near-field radiation, interfering with surrounding sensitive circuits, and are themselves susceptible to external interference. In addition, traditional magnetic core materials (such as ferrite and magnetic powder cores) experience a sharp increase in losses at high frequencies, limiting further improvements in efficiency and frequency.

[0004] Therefore, there is an urgent need to develop a power inductor with high-efficiency magnetic shielding, low high-frequency loss, compact structure, and easy integration with PCB to meet the application requirements of high-frequency, high-density switching power supplies.

[0005] It should be noted that the above description of the technical background is only for the purpose of providing a clear and complete explanation of the technical solutions of the present invention and facilitating understanding by those skilled in the art. It should not be assumed that the above technical solutions are known to those skilled in the art simply because they have been described in the background section of this invention. Summary of the Invention

[0006] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a PCB air-core inductor and its design method, as well as a switching power supply, to solve many problems in the prior art such as poor magnetic shielding performance and high high-frequency loss of PCB planar inductors.

[0007] To achieve the above and other related objectives, the present invention provides a design method for a PCB air-core inductor, the design method comprising:

[0008] Determine the number of turns, winding width, and winding thickness of the PCB air-core inductor, and design the number of winding layers in the PCB board and the width and thickness of the winding metal in each winding layer accordingly.

[0009] The winding metals in each winding layer are connected in series to form a PCB winding, wherein the PCB winding is embedded in an insulating support body made of an insulating medium.

[0010] A metal shield is formed on the outer periphery of the PCB winding, wherein the insulating medium is present between the metal shield and the PCB winding;

[0011] The metal shielding body includes four peripheral shielding walls, one upper shielding wall and one lower shielding wall. The start and end of the PCB winding pass through the corresponding peripheral shielding walls and are led out through the input terminal and output terminal, respectively.

[0012] Optionally, the method for determining the number of winding turns includes: obtaining the inductance value of the PCB air-core inductor based on electrical parameter design requirements, obtaining the coil radius and coil length of the PCB air-core inductor based on spatial dimension design requirements, and substituting the inductance value, the coil radius, and the coil length into the air-core inductor turn count calculation formula to obtain the number of winding turns; and / or,

[0013] The method for determining the winding width and winding thickness includes: obtaining the maximum current and maximum current density of the PCB air-core inductor based on the electrical parameter design requirements, and then obtaining the effective cross-sectional area of ​​the PCB air-core inductor based on this, and finally obtaining the winding width and winding thickness in combination with the spatial dimension design requirements.

[0014] Optionally, the method of sequentially connecting the winding metals in each winding layer in series includes:

[0015] The beginning and end of the winding metal in adjacent winding layers are staggered, wherein the end of the winding metal in the upper winding layer is set opposite to the beginning of the winding metal in the lower winding layer.

[0016] The winding metals in each winding layer are connected in series by electrically connecting the ends of the winding metals in the upper winding layer to the beginnings of the winding metals in the lower winding layer through interlayer interconnection holes.

[0017] Optionally, the design method further includes:

[0018] A plurality of first island metals are provided in each winding layer, wherein each first island metal is arranged sequentially between the beginning and end of the winding metal along the outer side of the winding metal and is positioned opposite to the corresponding end of the other winding metals.

[0019] A plurality of second island metals are provided in the upper shielding wall and the lower shielding wall, wherein each second island metal is arranged opposite to the beginning and end of the winding metal in any winding layer and to each first island metal.

[0020] The interlayer interconnects are formed using a metallization via process to electrically interconnect the relatively isolated metal islands.

[0021] Alternatively, methods for forming a metallic shield include:

[0022] A first shielding metal is provided around the winding metal in each winding layer, wherein the first shielding metal and the winding metal have the insulating medium between them;

[0023] A shielding layer is provided above the first winding layer and below the last winding layer in the PCB board, wherein a second shielding metal is provided in the shielding layer and at least covers the area surrounded by the first shielding metal;

[0024] The shielding metal of each layer in the PCB is processed using a metallized via process, and several metal pillars are formed around the PCB winding to serve as four peripheral shielding walls. The two shielding layers serve as the upper shielding wall and the lower shielding wall, respectively, thereby forming the metal shielding body.

[0025] Optionally, before forming the metal shield, the design method further includes removing the insulating medium located in the PCB winding core area.

[0026] Optionally, after forming the metal shield, the design method further includes:

[0027] A radiator is installed on the upper shielding wall or the lower shielding wall; and / or,

[0028] An input electrode and an output electrode are formed on the outside of the upper shielding wall and / or the lower shielding wall, wherein the input electrode and the output electrode are electrically interconnected with the input terminal and the output terminal, respectively.

[0029] The present invention also provides a PCB air-core inductor, the PCB air-core inductor comprising:

[0030] PCB windings are embedded in an insulating support made of an insulating medium and include a number of winding metals connected in series, wherein each winding metal is formed in a winding layer of the PCB board.

[0031] A metal shield is formed on the outer periphery of the PCB winding, wherein the insulating medium is present between the metal shield and the PCB winding;

[0032] The metal shielding body includes four peripheral shielding walls, one upper shielding wall and one lower shielding wall. The start and end of the PCB winding pass through the corresponding peripheral shielding walls and are led out through the input terminal and output terminal, respectively.

[0033] Optionally, in the PCB winding, the beginning and end of the winding metal in adjacent winding layers are staggered, wherein the end of the winding metal in the upper winding layer is positioned opposite to the beginning of the winding metal in the lower winding layer and is electrically interconnected through interlayer interconnect holes.

[0034] Optionally, each winding layer is further provided with a plurality of first island metals, wherein each first island metal is arranged sequentially between the beginning and end of the winding metal along the outer edge of the winding metal and is disposed opposite to the corresponding end of the other winding metal; the upper shielding wall and the lower shielding wall are further provided with a plurality of second island metals, wherein each second island metal is disposed opposite to each first island metal; the corresponding ends of the oppositely disposed island metals and the corresponding winding metals are electrically interconnected through metallized vias.

[0035] Optionally, a first shielding metal is provided around the winding metal in each winding layer, wherein the first shielding metal and the winding metal have the insulating medium; a shielding layer is provided above the first winding layer and below the last winding layer in the PCB board, wherein the shielding layer contains a second shielding metal and at least covers the area surrounded by the first shielding metal; the shielding metal of each layer in the PCB board forms a plurality of metal pillars based on metallized vias to serve as four peripheral shielding walls, wherein the two shielding layers serve as the upper shielding wall and the lower shielding wall, respectively.

[0036] Optionally, the core area of ​​the PCB winding has a hollow structure.

[0037] Optionally, the PCB air-core inductor further includes:

[0038] A radiator is installed on the upper shielding wall or the lower shielding wall; and / or,

[0039] An input electrode and an output electrode are formed on the outside of the upper shielding wall and / or the lower shielding wall, wherein the input electrode and the output electrode are electrically interconnected with the input terminal and the output terminal, respectively.

[0040] The present invention also provides a switching power supply, the switching power supply including an output inductor, wherein the output inductor is obtained by the design method of the PCB air core inductor described in any one of the above claims, or is implemented by the PCB air core inductor described in any one of the above claims.

[0041] As described above, the PCB air-core inductor and its design method, as well as the switching power supply of the present invention, have the following beneficial effects:

[0042] 1. Excellent high-frequency magnetic shielding performance: The metal shielding body forms a nearly fully enclosed Faraday cage, which can prevent magnetic field escape, suppress radiation interference and external interference, and confine most of the working magnetic field (especially the high-frequency alternating magnetic field) inside the inductor, greatly reducing the radiation of the magnetic field outward and interference to external circuits. At the same time, it reduces the possibility of the inductor being affected by external magnetic fields, which is conducive to the integration of high-density, high-sensitivity circuits and improves the utilization efficiency of the inductor.

[0043] 2. Low high-frequency loss: The hollow core design fundamentally avoids the hysteresis loss, eddy current loss and residual loss of magnetic materials at high frequencies, so that the inductor can still maintain a high quality factor and efficiency when operating at ultra-high frequencies.

[0044] 3. High power density and good heat dissipation: The three-dimensional spiral PCB winding design makes the inductor structure more compact and the power density higher; the winding layer and shielding layer are combined by island metal, the heat conduction path is shorter, which is conducive to heat dissipation and improves thermal management.

[0045] 4. High consistency and easy integration: Mass production using standard or improved PCB manufacturing processes (e.g., high-density interconnect processes) ensures good consistency and high precision; inductors can be designed and manufactured directly as part of the PCB, achieving organic integration of passive components and reducing separate soldering processes and parasitic parameters.

[0046] 5. Robust and reliable structure: The entire structure is made of PCB materials and processes, with no assembly gaps, high mechanical strength, and better vibration and impact resistance than many traditional discrete inductors. Attached Figure Description

[0047] Figure 1 The flowchart shown is a PCB air-core inductor design method of the present invention.

[0048] Figure 2 The diagram shown is a structural schematic of a PCB air-core inductor according to the present invention.

[0049] Figure 3 The diagram shows a structural schematic of removing the upper shielding wall from the PCB hollow inductor according to the present invention.

[0050] Figure 4 Displayed as Figure 2 The diagram shows a structural schematic of the upper shielding layer in a PCB air-core inductor.

[0051] Figure 5 Displayed as Figure 2 The diagram shows a structural schematic of the first winding layer in a PCB air-core inductor.

[0052] Figure 6 Displayed as Figure 2The diagram shows a structural schematic of the second winding layer in a PCB air-core inductor.

[0053] Figure 7 Displayed as Figure 2 The diagram shows a structural schematic of the third winding layer in a PCB air-core inductor.

[0054] Figure 8 Displayed as Figure 2 The diagram shows a structural schematic of the fourth winding layer in a PCB air-core inductor.

[0055] Figure 9 Displayed as Figure 2 The diagram shows a structural schematic of the fifth winding layer in a PCB air-core inductor.

[0056] Figure 10 Displayed as Figure 2 The diagram shows a structural schematic of the sixth winding layer in a PCB air-core inductor.

[0057] Figure 11 Displayed as Figure 2 The diagram shows a structural schematic of the seventh winding layer in a PCB air-core inductor.

[0058] Figure 12 Displayed as Figure 2 The diagram shows a structural schematic of the eighth winding layer in a PCB air-core inductor.

[0059] Figure 13 Displayed as Figure 2 The diagram shows a structural schematic of the ninth winding layer in a PCB air-core inductor.

[0060] Figure 14 Displayed as Figure 2 The diagram shows a structural schematic of the filler layer in a PCB air-core inductor.

[0061] Figure 15 Displayed as Figure 2 The diagram shows a structural schematic of the lower shielding layer in a PCB air-core inductor.

[0062] Figure 16 Displayed as Figure 4 The diagram shows a structure in which input and output electrodes are added to the upper shielding layer.

[0063] Component labeling: 100-PCB air-core inductor, 110-PCB winding, 111-winding metal, 112-start end, 113-end end, 120-insulating medium, 130-metal shield, 131-peripheral shield, 132-upper shield, 133-lower shield, 140a-input terminal, 140b-output terminal, 150a-first shield metal, 150b-second shield metal, 160a-first island metal, 160b-second island metal, 170a-input electrode, 170b-output electrode. Detailed Implementation

[0064] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0065] Please see Figures 1 to 16 It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the illustrations only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the shape, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0066] Example 1

[0067] See Figure 1 and combined Figures 2 to 16 This embodiment provides a design method for a PCB air-core inductor 100, including the following steps, for example, steps S1 to S3. Wherein:

[0068] Step S1: Determine the number of turns, winding width, and winding thickness of the PCB air core inductor 100, and design the number of winding layers in the PCB board and the width and thickness of the winding metal 111 in each winding layer accordingly.

[0069] In one embodiment, the method for determining the number of winding turns includes: obtaining the inductance value of the PCB air-core inductor 100 based on electrical parameter design requirements, obtaining the coil radius and coil length of the PCB air-core inductor 100 based on spatial dimension design requirements, and substituting the inductance value, coil radius, and coil length into the air-core inductor turns calculation formula to obtain the number of winding turns.

[0070] In practical applications, the design requirements for electrical parameters and spatial dimensions are usually determined by the specific scenario, and no excessive restrictions are imposed on them. In addition, given a fixed spatial dimension, obtaining the optimal values ​​for the coil radius and coil length of a 100mm PCB air-core inductor is a conventional technique in this field, and therefore will not be elaborated upon.

[0071] In this embodiment, the inductance value of the PCB air-core inductor satisfies Formula 1: Where L is the inductance (in Henry, i.e., H), and μ0 is the free permeability (μ0 = 4π × 10⁻⁶). -7 H / m), N is the number of turns in the winding, R is the coil radius of the PCB air-core inductor (in meters, i.e., m), and l is the coil length of the PCB air-core inductor (in meters, i.e., m).

[0072] Equation 1 is transformed to obtain Equation 2: Additionally, μ0π = 4π 2 ×10 -7 ≈3.9478×10 -6 H / m, substituting it into Formula 2, yields Formula 3: Formula 3 is the formula for calculating the number of turns of an air-core inductor. By substituting the inductance value, coil radius, and coil length into Formula 3, the number of turns of the winding can be obtained.

[0073] In one embodiment, the method for determining the winding width and winding thickness includes: obtaining the maximum current and maximum current density of the PCB air-core inductor 100 based on electrical parameter design requirements, and thereby obtaining the effective cross-sectional area of ​​the PCB air-core inductor 100, and then combining the spatial dimension design requirements to obtain the winding width and winding thickness.

[0074] In this embodiment, current density is defined as the magnitude of the current flowing through the effective cross-sectional area of ​​the conductor, satisfying Formula 4: Where J is the current density (unit: amperes per square millimeter, i.e., A / mm²). 2 I is the current flowing through the conductor (in amperes, i.e., A), and S is the effective cross-sectional area of ​​the conductor (in square millimeters, i.e., mm). 2 ).

[0075] For a PCB air-core inductor of size 100, its cross-section is rectangular. Therefore, the effective cross-sectional area S of the conductor satisfies Formula 5: Where W is the winding width of the PCB air-core inductor (in millimeters, i.e., mm), and T is the winding thickness of the PCB air-core inductor (in millimeters, i.e., mm).

[0076] Substituting the maximum current and maximum current density into Formula 4, we can obtain the value of S, which is the product of W and T; then, by taking the spatial dimensions as a constraint, we can obtain the optimal solutions for W and T.

[0077] In addition, when designing a PCB board, the number of winding layers is determined by the number of winding turns, and the number of winding layers is the same as the number of winding turns. Furthermore, the width and thickness of the winding metal 111 in each winding layer are determined by the winding width W and the winding thickness T, respectively, where the width of the winding metal 111 is the same as the winding width W, and the thickness of the winding metal 111 is the same as the winding thickness T. Of course, the shape of the winding metal 111 also needs to be designed. In practical applications, the shape of the winding metal 111 is usually a non-closed loop with a starting end 112 and an ending end 113 to facilitate subsequent electrical interconnection.

[0078] Step S2: The winding metals 111 in each winding layer are connected in series to form a PCB winding 110, wherein the PCB winding 110 is embedded in an insulating support body composed of an insulating medium 120, such as... Figure 3 , Figures 5 to 13 As shown, PCB winding 110 has a three-dimensional spiral structure, which allows for more winding turns within a limited space, optimizing space utilization, achieving a smaller volume, and increasing inductance.

[0079] In practical applications, each winding layer includes not only the winding metal 111 but also an insulating medium 120, which mainly serves as mechanical support, interlayer insulation, and heat conduction. The winding metal 111 is embedded in the insulating medium 120. As an optional solution, the winding metal 111 can be made of copper, and the insulating medium 120 can be made of epoxy resin fiberglass cloth substrate (FR4), high-frequency substrate, ceramic substrate, etc.

[0080] In one embodiment, the method of sequentially connecting the winding metals 111 in each winding layer in series includes the following steps, for example, steps S21 and S22. Wherein:

[0081] Step S21 involves staggering the start 112 and end 113 of the winding metals 111 in adjacent winding layers. Specifically, the end 113 of the winding metal 111 in the upper winding layer is positioned opposite the start 112 of the winding metal 111 in the lower winding layer. For example, the end 113 of the winding metal 111 in the first layer is positioned opposite the start 112 of the winding metal 111 in the second layer, the end 113 of the winding metal 111 in the second layer is positioned opposite the start 112 of the winding metal 111 in the third layer, and so on. In practical applications, the staggered arrangement of the start 112 and end 113 of each winding metal 111 in step S21 is usually implemented simultaneously with the PCB design in step S1.

[0082] Step S22: The end 113 of the winding metal 111 in the upper winding layer and the beginning 112 of the winding metal 111 in the lower winding layer are electrically interconnected through interlayer interconnecting holes to connect the winding metals 111 in each winding layer in series to form a PCB winding 110. Specifically, at least one interconnecting hole is formed at the end 113 of the winding metal 111 in the upper winding layer and the beginning 112 of the winding metal 111 in the lower winding layer. The interconnecting hole can be one of via, blind via, or buried via, and is usually formed by laser drilling. Then, conductive metal is filled into the interconnecting hole, usually formed by electroplating, to connect two winding metals 111 in adjacent winding layers in series.

[0083] Step S3: A metal shield 130 is formed on the outer periphery (including the four sides, top, and bottom) of the PCB winding 110, wherein an insulating medium 120 is provided between the metal shield 130 and the PCB winding 110 to achieve electrical isolation. Figure 2 As shown.

[0084] In this step, the metal shield 130 includes four peripheral shielding walls 131, one upper shielding wall 132, and one lower shielding wall 133. The beginning 112 and the end 113 of the PCB winding 110 pass through the corresponding peripheral shielding walls 131 and are led out through the input terminal 140a and the output terminal 140b, respectively. Figure 2 and Figure 3 As shown, the four peripheral shielding walls 131, the upper shielding wall 132, and the lower shielding wall 133 together form a nearly fully enclosed Faraday cage, and the Faraday cage is electrically interconnected with a specific potential (e.g., ground potential) of the PCB board.

[0085] In one embodiment, the method for forming the metal shield 130 includes the following steps, for example, steps S31, S32, and S33. Wherein:

[0086] Step S31: A first shielding metal 150a is provided around the winding metal 111 in each winding layer, wherein the first shielding metal 150a and the winding metal 111 are separated by an insulating medium 120 to achieve electrical isolation. Figures 5 to 13 As shown. In practical applications, step S31, which involves setting the first shielding metal 150a in the winding layer, is usually implemented simultaneously during the PCB design in step S1; in addition, the shape of the first shielding metal 150a is usually a hollow rectangle.

[0087] Step S32: A shielding layer is respectively disposed above the first winding layer and below the last winding layer in the PCB board. The shielding layer contains a second shielding metal 150b, which at least covers the area enclosed by the first shielding metal 150a. Figure 4 and Figure 15As shown. In practical applications, step S32, which sets the shielding layer and sets the second shielding metal 150b in the shielding layer, is usually implemented simultaneously with the PCB board design in step S1; in addition, the shape of the second shielding metal 150b is usually rectangular, and it is a large area of ​​continuous metal.

[0088] It should be noted that, for ease of distinction, the shielding layer formed above the first winding layer is referred to as the upper shielding layer, and the shielding layer formed below the last winding layer is referred to as the lower shielding layer.

[0089] Step S33: The shielding metal of each layer in the PCB board is processed using a metallized via process, and several metal pillars are formed around the PCB winding 110 to serve as four peripheral shielding walls 131. Two shielding layers serve as the upper shielding wall 132 and the lower shielding wall 133, respectively, thus forming a metal shielding body 130. Figures 2 to 15 As shown.

[0090] Specifically, firstly, several vias penetrating each layer of shielding metal are formed, typically using laser drilling. These vias are then arranged sequentially around the perimeter of the PCB winding 110 along the first shielding metal 150a. Next, conductive metal is filled into the vias to form metal pillars, typically using electroplating. Each metal pillar is electrically interconnected with the two shielding layers to form a metal shield 130. In practical applications, the spacing between adjacent vias is kept as small as possible, usually determined by the minimum process window, to facilitate the formation of a nearly fully enclosed Faraday cage.

[0091] Additionally, to facilitate the lead-out of the input terminal 140a, when the first shielding metal 150a is provided in the first winding layer, it can be configured as a non-closed hollow rectangle, so that the input terminal 140a can be led out from the break point, such as... Figure 5 As shown; for the vias in the area where the break is located, the vias start from the lower shielding layer and continue through the second winding layer; similarly, in order to bring out the output terminal 140b, when the first shielding metal 150a is provided in the last winding layer, it can be set as a non-closed hollow rectangle so that the output terminal 140b can be brought out from the break. (See reference...) Figure 14 As for the vias in the area where the break is located, they start from the upper shielding layer and continue until they penetrate the penultimate winding layer.

[0092] In this embodiment, since the PCB winding 110 is embedded in the insulating medium 120, the insulating medium 120 serves as the core material of the PCB winding 110. Furthermore, due to the low permeability of the PCB insulating medium 120 (close to the permeability of air 1), the PCB winding 110 can be considered as an air-core inductor, thereby eliminating high-frequency core losses. Alternatively, an intermediate step, designated as step S2-3, can be added before the metal shield 130 is formed, for example, between steps S2 and S3, to remove the insulating medium 120 located in the core region of the PCB winding 110, thus forming a truly air-core inductor.

[0093] Furthermore, the design method of this embodiment also includes at least one of steps S4 and S5; when both steps S4 and S5 are included, the execution order of the two steps can be interchanged, which has no substantial impact on this embodiment. Wherein:

[0094] Step S4: An input electrode 170a and an output electrode 170b are formed on the outside of the upper shielding wall 132 and / or the lower shielding wall 133, wherein the input electrode 170a and the output electrode 170b are electrically interconnected with the input terminal 140a and the output terminal 140b, respectively. Figure 16 As shown.

[0095] The input electrode 170a and output electrode 170b in this step can be formed simultaneously on the outside of the upper shielding wall 132, or simultaneously on the outside of the lower shielding wall 133, or one can be formed on the outside of the upper shielding wall 132 and the other on the outside of the lower shielding wall 133; in practical applications, they are usually formed simultaneously on the outside of either the upper shielding wall 132 or the lower shielding wall 133. Furthermore, an insulating medium 120 is provided between the input electrode 170a and the output electrode 170b and their corresponding shielding walls to facilitate electrical isolation and prevent short circuits.

[0096] In one embodiment, the method of electrically interconnecting the corresponding terminal with the corresponding electrode includes: electrically interconnecting the input terminal 140a and the output terminal 140b with the input electrode 170a and the output electrode 170b respectively through a metallized via process, so as to connect the PCB air core inductor 100 to the circuit; wherein the input electrode 170a and the output electrode 170b can be one of the following: pad, pin, and solder ball.

[0097] Step S5: A heat sink (not shown in the figure) is installed on the upper shielding wall 132 or the lower shielding wall 133; for example, the heat sink is installed on the upper shielding wall 132 or the lower shielding wall 133 by an adhesive layer. In practical applications, when the design method of this embodiment further includes step S4, the heat sink and the input and output electrodes usually correspond to different shielding walls. For example, the input electrode 170a and the output electrode 170b are located outside the upper shielding wall 132, and the heat sink is located on the lower shielding wall 133.

[0098] The PCB air-core inductor 100 in this embodiment adopts a unique "embedded" PCB winding structure and a near-fully enclosed Faraday cage shielding structure. While achieving high inductance density and low DC resistance, it can effectively suppress high-frequency magnetic field leakage and reduce electromagnetic interference. Furthermore, due to the air-core design, high-frequency magnetic core loss is avoided, making it particularly suitable for MHz-level high-frequency operating conditions.

[0099] Example 2

[0100] Combination Figures 2 to 16 This embodiment provides a design method for a PCB air-core inductor 100, which, compared to Embodiment 1, further includes the following steps, such as steps Sa, Sb, and Sc. Wherein:

[0101] Step Sa involves setting a plurality of first island metals 160a in each winding layer. Each first island metal 160a is arranged sequentially along the outer edge of its corresponding winding metal 111 between the starting end 112 and the ending end 113, and is positioned opposite to the corresponding ends of other winding metals 111, such as... Figure 3 , Figures 5 to 13 As shown, the PCB winding 110 with its three-dimensional spiral structure presents an overall "flower" shape. In practical applications, each first island metal 160a and its corresponding winding metal 111 are separated by an insulating medium 120 to achieve electrical isolation. In addition, the setting of the first island metal 160a in step Sa is usually implemented simultaneously during the PCB design in step S1.

[0102] In this step, the beginning 112 of any winding metal 111 is positioned opposite to the end 113 of the winding metal 111 in the upper winding layer, and also opposite to the corresponding first island metal 160a in other winding layers; similarly, the end 113 of any winding metal 111 is positioned opposite to the beginning 112 of the winding metal 111 in the lower winding layer, and also opposite to the corresponding first island metal 160a in other winding layers. In fact, the number of first island metals 160a in each winding layer is determined by the number of winding turns. Let the number of winding turns be N, then the number of first island metals 160a in each winding layer is N-1, where N is a natural number greater than 1.

[0103] Step Sb: A plurality of second island metals 160b are disposed in the upper shielding wall 132 and the lower shielding wall 133, wherein each second island metal 160b is disposed opposite to the beginning 112 and end 113 of the winding metal 111 in any winding layer, and to each first island metal 160a, as shown below. Figure 2 , Figure 4 and Figure 15 As shown. In practical applications, each second island metal 160b is separated from its corresponding shielding metal by an insulating medium 120 to achieve electrical isolation; in addition, the setting of the second island metal 160b in step Sb is usually implemented simultaneously during the PCB board design in step S1.

[0104] In step Sc, an interlayer interconnection hole is formed using a metallization via process to electrically interconnect the end 113 of the winding metal 111 in the upper winding layer with the beginning 112 of the winding metal 111 in the lower winding layer. At the same time, the island metals that are arranged opposite to each other are also electrically interconnected.

[0105] It should be noted that when performing step Sc in this embodiment, it is not necessary to perform step S22 in embodiment one. In other words, step Sc is a replacement step for step S22.

[0106] Specifically, a laser drilling process is used to penetrate the relatively isolated metal islands and their corresponding ends to form a micro-hole array. Then, an electroplating process is used to fill the micro-hole array with conductive metal. Each micro-hole array can contain one, two, or more micro-holes, typically determined by specific requirements. When there are two or more micro-holes, the spacing between adjacent micro-holes is usually 1 mm. Furthermore, the diameter of the micro-holes is typically very small, for example, 0.2 mm, much smaller than the wavelength of electromagnetic waves in the medium at the operating frequency, to avoid affecting the shielding performance of the metal shield 130.

[0107] The PCB air-core inductor 100 in this embodiment uses an islanded metal design to fill the micro-hole array with conductive metal to establish a shorter heat conduction path and improve thermal management. Without affecting the shielding performance, it can reduce the temperature rise caused by eddy current loss of the metal shield 130. At the same time, it can also increase the resistance of the eddy current path and reduce the eddy current intensity.

[0108] Taking a winding turn count of N=9 as an example, when manufacturing a PCB air-core inductor 100: First, the PCB board is designed with 9 winding layers and 2 shielding layers. The winding metal 111, first island metal 160a, and first shielding metal 150a in the winding layers are designed, as well as the second island metal 160b and second shielding metal 150b in the shielding layers. Second, a stacked lower shielding layer, 9 winding layers, and upper shielding layer are formed sequentially from bottom to top. Then, each island metal, each start point 112, and each end point 113 are processed using a metallized via process, and each shielding metal is processed using a metallized via process. Finally, the input terminal 140a and output terminal 140b are led out through the input electrode 170a and output electrode 170b. Of course, before forming the upper shielding layer, the insulating medium 120 within the winding metal 111 in each winding layer can be removed.

[0109] In practical applications, the number of PCB layers is usually even. When the number of winding turns is odd, the corresponding number of PCB layers is also odd. Typically, a filler layer is formed between the last winding layer and the underlying shielding layer. In this case, the filler layer can only have the design of the first island metal 160a and the first shielding metal 150a. Of course, the output terminal 140b can also be designed on it, such as... Figure 14 As shown, this has no substantial impact on this embodiment. It should be noted that it is also feasible to place the compensation layer between the first winding layer and the upper shielding layer, and there is no limitation on this.

[0110] Example 3

[0111] like Figures 2 to 16 As shown, this embodiment provides a PCB air-core inductor 100, including a PCB winding 110, an insulating support, and a metal shield 130. In practical applications, the PCB air-core inductor 100 of this embodiment can be obtained using the design methods described in Embodiment 1 or Embodiment 2. Of course, it is also feasible to obtain it using other design methods.

[0112] PCB winding 110 is embedded in an insulating support body composed of insulating medium 120; wherein, PCB winding 110 includes a plurality of winding metals 111 connected in series, and each winding metal 111 is formed in each winding layer of the PCB board, such as Figure 3 , Figures 5 to 13 As shown.

[0113] Specifically, in PCB winding 110, the starting ends 112 and ending ends 113 of the winding metal 111 in adjacent winding layers are staggered. The ending end 113 of the winding metal 111 in the upper winding layer is positioned opposite to the starting end 112 of the winding metal 111 in the lower winding layer and is electrically interconnected via interlayer interconnect holes. The PCB winding 110 in this example has a three-dimensional spiral structure, which allows for a greater number of winding turns within a limited space, optimizing space utilization, achieving a smaller volume, and simultaneously increasing inductance.

[0114] In one example, the core region of the PCB winding 110 is filled with insulating medium 120. Due to the low permeability of the insulating medium 120 (close to the permeability of air 1), the PCB winding 110 can be regarded as a hollow structure, thereby eliminating high-frequency core losses. In another example, the core region of the PCB winding 110 is a hollow structure. In this case, the PCB winding 110 is a truly hollow structure.

[0115] A metal shield 130 is formed on the outer periphery (including the four sides, top, and bottom) of the PCB winding 110, wherein an insulating medium 120 is provided between the metal shield 130 and the PCB winding 110 to achieve electrical isolation, such as... Figure 2 and Figure 3 As shown.

[0116] Specifically, such as Figure 2 and Figure 3 As shown, the metal shield 130 includes four peripheral shielding walls 131, an upper shielding wall 132, and a lower shielding wall 133. The shielding walls together form a nearly fully enclosed Faraday cage, and the Faraday cage is electrically interconnected with a specific potential (e.g., ground potential) of the PCB board. The beginning 112 and the end 113 of the PCB winding 110 pass through the corresponding peripheral shielding walls 131 and are led out through the input terminal 140a and the output terminal 140b, respectively.

[0117] As an example, such as Figures 5 to 13 As shown, a first shielding metal 150a is also provided around the winding metal 111 in each winding layer, wherein an insulating medium 120 is provided between the first shielding metal 150a and the winding metal 111 to achieve electrical isolation; as shown Figure 4 and Figure 15 As shown, a shielding layer is provided above the first winding layer and below the last winding layer in the PCB board. The shielding layer is provided with a second shielding metal 150b, and the second shielding metal 150b at least covers the area surrounded by the first shielding metal 150a. The shielding metal of each layer in the PCB board forms a number of metal pillars based on metallized vias to serve as four peripheral shielding walls 131. In addition, the two shielding layers serve as the upper shielding wall 132 and the lower shielding wall 133, respectively.

[0118] In practical applications, the first shielding metal 150a is typically a hollow rectangle, and the second shielding metal 150b is typically a rectangle, such as... Figures 4 to 15 As shown; in addition, among the several metal pillars formed based on metallized vias, the spacing between adjacent metal pillars should be as small as possible in order to form an approximately fully enclosed Faraday cage.

[0119] To bring out the input terminal 140a and the output terminal 140b, the first shielding metal 150a of the corresponding terminal layer is usually set as a non-closed hollow rectangle, and no metal pillar is formed at its break point; for the input terminal 140a, the metal pillar in the break point area extends upward from the lower shielding layer to the second winding layer, and for the output terminal 140b, the metal pillar in the break point area extends downward from the upper shielding layer to the penultimate winding layer.

[0120] As a preferred embodiment, each winding layer is further provided with a plurality of first island metals 160a, wherein each first island metal 160a is arranged sequentially between the starting end 112 and the ending end 113 along the outer side of the corresponding winding metal 111, and is positioned opposite to the corresponding ends of other winding metals 111, such as... Figures 5 to 13 As shown; the upper shielding wall 132 and the lower shielding wall 133 are also provided with a number of second island metals 160b, wherein each second island metal 160b is arranged opposite to each first island metal 160a, as shown. Figure 4 and Figure 15 As shown, the corresponding ends of the island metals and the corresponding winding metals 111 are electrically interconnected through metallized vias, so as to improve thermal management by establishing a shorter heat conduction path with the help of the island metal design.

[0121] In practical applications, each first island metal 160a is electrically isolated from its corresponding winding metal 111 by an insulating medium 120, and each second island metal 160b is electrically isolated from its corresponding shielding metal by an insulating medium 120. Furthermore, the beginning end 112 of any winding metal 111 is positioned opposite to the end end 113 of the winding metal 111 in the upper winding layer, and also opposite to the corresponding first island metal 160a in other winding layers; similarly, the end end 113 of any winding metal 111 is positioned opposite to the beginning end 112 of the winding metal 111 in the lower winding layer, and also opposite to the corresponding first island metal 160a in other winding layers.

[0122] Furthermore, the PCB air-core inductor 100 in this embodiment also includes electrodes (including input electrode 170a and output electrode 170b, such as...) Figure 16 At least one of the following: (shown in the figure) and a heat sink (not shown in the figure).

[0123] Input electrode 170a and output electrode 170b are formed on the outside of upper shielding wall 132 and / or lower shielding wall 133, wherein input electrode 170a and output electrode 170b are electrically interconnected with input terminal 140a and output terminal 140b, respectively.

[0124] Regarding the input electrode 170a and the output electrode 170b, they can be simultaneously formed on the outside of the upper shielding wall 132, or simultaneously formed on the outside of the lower shielding wall 133, or one can be formed on the outside of the upper shielding wall 132 and the other on the outside of the lower shielding wall 133. In practical applications, the input electrode 170a and the output electrode 170b are usually formed simultaneously on the outside of either the upper shielding wall 132 or the lower shielding wall 133. Furthermore, an insulating medium 120 is provided between the input electrode 170a and the output electrode 170b and their respective shielding walls to facilitate electrical isolation and prevent short circuits.

[0125] The heat sink is mounted on the upper shielding wall 132 or the lower shielding wall 133. In practical applications, when both electrodes and heat sinks are included, the electrodes and heat sinks usually correspond to different shielding walls. For example, the input electrode 170a and the output electrode 170b are located outside the upper shielding wall 132, and the heat sink is located on the lower shielding wall 133.

[0126] In practical applications, the number of PCB layers is usually even. When the number of winding turns is odd, the corresponding number of PCB layers is also odd. Typically, a filler layer is formed between the last winding layer and the underlying shielding layer. In this case, the filler layer can only have the design of the first island metal 160a and the first shielding metal 150a. Of course, the output terminal 140b can also be designed on it, such as... Figure 14 As shown, this has no substantial impact on this embodiment. It should be noted that it is also feasible to place the compensation layer between the first winding layer and the upper shielding layer, and there is no limitation on this.

[0127] Example 4

[0128] This embodiment provides a switching power supply, including an output inductor. Of course, it may also include other components, such as switching transistors, output capacitors, etc., without much limitation. The output inductor is a PCB air-core inductor 100, which can be obtained by the design method described in Embodiment 1 or Embodiment 2, or implemented by the structure described in Embodiment 3.

[0129] In practical applications, the switching transistors of switching power supplies are usually implemented using third-generation semiconductor devices (e.g., gallium nitride devices) in order to increase the operating frequency of the switching power supply to MHz.

[0130] Taking the switching power supply as an example of a synchronous half-bridge converter structure, the output inductor is implemented using a PCB air-core inductor 100, and the switching transistor is implemented using gallium nitride devices. Simulation verification shows that, due to the excellent magnetic shielding performance of the output inductor, the strong high-frequency magnetic field it generates is effectively limited, and the interference to nearby sensitive components such as controllers and feedback networks is significantly reduced.

[0131] In summary, the PCB air-core inductor and its design method, as well as the switching power supply of the present invention, possess numerous advantages, including excellent high-frequency magnetic shielding performance, low high-frequency loss, high power density and good heat dissipation, high consistency and ease of integration, and a robust and reliable structure. It is particularly suitable for high-frequency, high-density switching power supply applications, effectively improving the power density, operating efficiency, and electromagnetic compatibility of the switching power supply. Therefore, the present invention effectively overcomes the various shortcomings of the prior art and has high industrial applicability.

[0132] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A design method for a PCB air-core inductor, characterized in that, The design method includes: Determine the number of turns, winding width, and winding thickness of the PCB air-core inductor, and design the number of winding layers in the PCB board and the width and thickness of the winding metal in each winding layer accordingly. The winding metals in each winding layer are connected in series to form a PCB winding, wherein the PCB winding is embedded in an insulating support body made of an insulating medium. A metal shield is formed on the outer periphery of the PCB winding, wherein the insulating medium is present between the metal shield and the PCB winding; The metal shielding body includes four peripheral shielding walls, one upper shielding wall and one lower shielding wall. The start and end of the PCB winding pass through the corresponding peripheral shielding walls and are led out through the input terminal and output terminal, respectively. The design method further includes: A plurality of first island metals are provided in each winding layer, wherein each first island metal is arranged sequentially between the beginning and end of the winding metal along the outer side of the winding metal and is positioned opposite to the corresponding end of the other winding metals. A plurality of second island metals are provided in the upper shielding wall and the lower shielding wall, wherein each second island metal is arranged opposite to the beginning and end of the winding metal in any winding layer and to each first island metal. The interlayer interconnects are formed using a metallization via process to electrically interconnect the relatively isolated metal islands.

2. The design method for a PCB air-core inductor according to claim 1, characterized in that, The method for determining the number of turns in a winding includes: obtaining the inductance value of the PCB air-core inductor based on electrical parameter design requirements; obtaining the coil radius and coil length of the PCB air-core inductor based on spatial dimension design requirements; and substituting the inductance value, the coil radius, and the coil length into the formula for calculating the number of turns in an air-core inductor to obtain the number of turns in the winding; and / or, The method for determining the winding width and winding thickness includes: obtaining the maximum current and maximum current density of the PCB air-core inductor based on the electrical parameter design requirements, and then obtaining the effective cross-sectional area of ​​the PCB air-core inductor based on this, and finally obtaining the winding width and winding thickness in combination with the spatial dimension design requirements.

3. The design method for a PCB air-core inductor according to claim 1, characterized in that, Methods for sequentially connecting the winding metals in each winding layer in series include: The beginning and end of the winding metal in adjacent winding layers are staggered, wherein the end of the winding metal in the upper winding layer is set opposite to the beginning of the winding metal in the lower winding layer. The winding metals in each winding layer are connected in series by electrically connecting the ends of the winding metals in the upper winding layer to the beginnings of the winding metals in the lower winding layer through interlayer interconnection holes.

4. The design method for a PCB air-core inductor according to claim 1, characterized in that, Methods for forming a metallic shield include: A first shielding metal is provided around the winding metal in each winding layer, wherein the first shielding metal and the winding metal have the insulating medium between them; A shielding layer is provided above the first winding layer and below the last winding layer in the PCB board, wherein a second shielding metal is provided in the shielding layer and at least covers the area surrounded by the first shielding metal; The shielding metal of each layer in the PCB is processed using a metallized via process, and several metal pillars are formed around the PCB winding to serve as four peripheral shielding walls. The two shielding layers serve as the upper shielding wall and the lower shielding wall, respectively, thereby forming the metal shielding body.

5. The design method for a PCB air-core inductor according to any one of claims 1 to 4, characterized in that, Before forming the metal shield, the design method further includes removing the insulating medium located in the core region of the PCB winding.

6. The design method for a PCB air-core inductor according to any one of claims 1 to 4, characterized in that, After forming the metal shield, the design method further includes: A radiator is installed on the upper shielding wall or the lower shielding wall; and / or, An input electrode and an output electrode are formed on the outside of the upper shielding wall and / or the lower shielding wall, wherein the input electrode and the output electrode are electrically interconnected with the input terminal and the output terminal, respectively.

7. A PCB air-core inductor, characterized in that, The PCB air-core inductor includes: PCB windings are embedded in an insulating support made of an insulating medium and include a number of winding metals connected in series, wherein each winding metal is formed in a winding layer of the PCB board. A metal shield is formed on the outer periphery of the PCB winding, wherein the insulating medium is present between the metal shield and the PCB winding; The metal shielding body includes four peripheral shielding walls, one upper shielding wall and one lower shielding wall. The start and end of the PCB winding pass through the corresponding peripheral shielding walls and are led out through the input terminal and output terminal, respectively. Each winding layer is further provided with a number of first island metals, wherein each first island metal is arranged sequentially between the beginning and end of the winding metal along the outer edge of the winding metal and is positioned opposite to the corresponding end of the other winding metal; the upper shielding wall and the lower shielding wall are further provided with a number of second island metals, wherein each second island metal is positioned opposite to each first island metal; the corresponding ends of the oppositely positioned island metals and the corresponding winding metals are electrically interconnected through metallized vias.

8. The PCB air-core inductor according to claim 7, characterized in that, In the PCB winding, the beginning and end of the winding metal in adjacent winding layers are staggered. The end of the winding metal in the upper winding layer is positioned opposite to the beginning of the winding metal in the lower winding layer and is electrically interconnected through interlayer interconnect holes.

9. The PCB air-core inductor according to claim 7, characterized in that, Each winding layer has a first shielding metal around its winding metal, wherein the first shielding metal and the winding metal are separated by an insulating medium; a shielding layer is provided above the first winding layer and below the last winding layer in the PCB board, wherein the shielding layer contains a second shielding metal and at least covers the area surrounded by the first shielding metal; the shielding metal of each layer in the PCB board forms several metal pillars based on metallized vias to serve as four peripheral shielding walls, wherein two shielding layers serve as the upper shielding wall and the lower shielding wall, respectively.

10. The PCB air-core inductor according to claim 7, characterized in that, The core area of ​​the PCB winding has a hollow structure.

11. The PCB air-core inductor according to any one of claims 7 to 10, characterized in that, The PCB air-core inductor also includes: A radiator is installed on the upper shielding wall or the lower shielding wall; and / or, An input electrode and an output electrode are formed on the outside of the upper shielding wall and / or the lower shielding wall, wherein the input electrode and the output electrode are electrically interconnected with the input terminal and the output terminal, respectively.

12. A switching power supply, characterized in that, The switching power supply includes an output inductor, wherein the output inductor is obtained by the design method of the PCB air-core inductor as described in any one of claims 1 to 6, or is implemented by the PCB air-core inductor as described in any one of claims 7 to 11.

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