Vertical PCB winding structure capable of reducing alternating current loss and application thereof

Abstract

The invention discloses a vertical PCB winding structure capable of reducing alternating current loss and application thereof, and belongs to the field of power electronics. The vertical PCB winding structure comprises a PCB substrate, the PCB substrate is provided with a magnetic core in a slotting mode, the magnetic core is provided with a cavity, a plurality of narrow grooves are formed in the portion, in the cavity of the magnetic core, of the PCB substrate, vertical windings are arranged on the two side walls of the narrow grooves, and the vertical windings are connected through plane windings. By changing the arrangement mode of the conductors, the current density distribution condition in the conductors at high frequency is improved, so that the influence of a skin effect and a proximity effect on device impedance is reduced, and the low-loss and high-efficiency PCB winding is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of power electronics, and in particular relates to a vertical PCB winding structure capable of reducing AC loss and an application thereof. Background Art

[0002] PCB transformers and inductor windings used in power electronic equipment are mainly used to achieve the conversion and transmission of electric energy. Traditional transformers and inductors usually adopt a winding structure, but with the miniaturization and high frequency of electronic equipment, the defects of the traditional structure are gradually revealed: when working at high frequencies, the winding coil has increased losses due to the eddy current effect and reduced efficiency; the heat dissipation performance is poor, affecting the stability of the equipment; the leakage inductance of the winding inductor is large, which is easy to affect the normal operation of other electronic components.

[0003] With the rapid development of semiconductor wide bandgap devices, magnetic components are further developing in the direction of high frequency, miniaturization and lightweight, and planar windings on printed circuit boards have greater application prospects. Planar copper windings have a compact structure and high power density; their manufacturing technology is highly controllable and the product consistency is strong; copper plating has good heat dissipation performance, and can reduce ground line impedance and improve the device's anti-interference ability; in addition, the magnetic integration technology of planar windings facilitates improving the overall efficiency and power density of the system. Therefore, PCB transformers and inductors with planar copper windings are widely used in power management, wireless charging, high-frequency communications and other fields.

[0004] Although the planar winding structure has the above advantages, it also has some defects and shortcomings. First, due to the limitations of design and manufacturing process, the window utilization rate of planar inductors and transformers is low, and more space is occupied by insulating materials and other non-conductive materials, which is not conducive to improving system efficiency; at the same time, multi-layer PCB inductors will produce large parasitic capacitance, which is particularly obvious in high-frequency applications; in addition, in high-frequency applications, the skin effect and proximity effect lead to uneven current density distribution in the planar conductor, which in turn leads to an increase in the conductor AC impedance and reduces the overall efficiency of the system.

[0005] Therefore, in order to address the high loss problem of planar windings in high-frequency applications, a more effective PCB winding structure needs to be proposed to solve the problems existing in the prior art. Summary of the invention

[0006] The purpose of the present invention is to provide a vertical PCB winding structure and its application that can reduce AC loss, and solve the problem of high loss of planar winding. The present invention designs the conductor of the planar winding into a vertical structure, so that the conductor has a more uniform current density when used at high frequencies, thereby reducing its AC loss.

[0007] In order to achieve the above object, the present invention adopts the following technical solution: The present invention provides a vertical PCB winding structure capable of reducing AC loss, comprising a PCB substrate, a magnetic core is arranged on the PCB substrate through a slot, the magnetic core is provided with a cavity, a plurality of narrow slots are arranged on the PCB substrate in the magnetic core cavity, vertical windings are arranged on both side walls of the plurality of narrow slots, and the vertical windings are connected through a planar winding.

[0008] As a further improvement of the present invention, the number of the narrow slots is determined according to the number of turns of the winding required in the magnetic core cavity, one narrow slot is provided for every two turns of the winding, and vertical windings are provided on two side walls of the narrow slot.

[0009] As a further improvement of the present invention, the vertical winding uses a copper conductor, and the copper conductor is arranged on the side wall of the narrow slot by using a copper cladding or copper foil patch process.

[0010] As a further improvement of the present invention, the magnetic core is selected as an EI type or EE type magnetic core according to magnetic core parameters and actual applications. The magnetic core parameters include an effective cross-sectional area of ​​the magnetic core, a window cross-sectional area and an air gap length.

[0011] Where L is the inductance, N is the number of turns, Ae is the cross-sectional area of ​​the core, i m is the peak current in the device, B m is the saturation magnetic flux density, l a is the air gap length, u0 is.

[0012] As a further improvement of the present invention, the effective cross-sectional area of ​​the magnetic core, the air gap length and the window cross-sectional area are calculated according to L=u0N 2 A e / l a , B m =u0Ni m / l a and A w= NI / k c jCalculate; Where, L is the inductance, u0 is the vacuum permeability, N is the number of turns, Ae is the core cross-sectional area, l a is the air gap length, B m is the saturation magnetic flux density, i m is the peak current in the device, Aw is the window cross-sectional area, I is the effective current, kc is the winding filling factor, and j is the current density.

[0013] As a further improvement of the present invention, the magnetic core is a ferrite core.

[0014] As a further improvement of the present invention, the shape of the narrow groove is n-deformed, where n≥4.

[0015] As a further improvement of the present invention, the width of the narrow groove is greater than or equal to 1.2 mm. As a further improvement of the present invention, the planar winding adopts a copper foil patch process. The present invention also provides a PCB inductor for an ultra-thin power supply, comprising the above-mentioned vertical PCB winding structure capable of reducing AC loss.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention proposes a novel vertical PCB winding structure, which improves the current density distribution inside the conductor at high frequency by changing the arrangement of the conductors, thereby reducing the influence of the skin effect and the proximity effect on the device impedance, thereby realizing a low-loss, high-efficiency PCB winding design. The present invention provides a vertical PCB winding structure that designs part of the winding as a vertical winding structure to improve space utilization; has lower ESR loss than a planar winding; and has higher current and power density than a Litz wire.

[0017] The vertical PCB winding structure designed in the present invention can be applied to PCB transformers and inductors required for ultra-thin power supplies, and can be easily integrated with other electronic components to form a compact and efficient power supply system, which can effectively improve the performance of ultra-thin power supplies. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0019] Figure 1 is a cross-sectional view of the vertical PCB winding structure of the present invention; Figure 2 It is a schematic diagram of the current density distribution in the conductor of the planar PCB winding; Figure 3 Schematic diagram of current density distribution in the conductor of the vertical PCB winding of Example 1 Figure 4 It is a schematic diagram of the planar PCB winding simulation structure; Figure 5 is a schematic diagram of the simulation structure of the vertical PCB winding of Example 1; Figure 6 This is a physical picture of the vertical PCB winding; In the figure, 1. PCB substrate; 2. narrow slot; 3. vertical winding; 4. magnetic core; 5. air gap. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0021] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0023] In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inside", "outside", "middle", "vertical", "horizontal", "lateral", "longitudinal" and the like are used to indicate the orientation or position relationship based on the orientation or position relationship shown in the accompanying drawings, or the orientation or position relationship in which the product of the invention is usually placed when in use, it is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0024] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", which does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0025] In the description of the embodiments of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0026] The present invention will be further described below in conjunction with the accompanying drawings: The present invention provides a vertical PCB winding structure capable of reducing AC loss, comprising a PCB substrate, a magnetic core is arranged on a slot in the PCB substrate, the magnetic core is provided with a cavity, a plurality of narrow slots are arranged on the PCB substrate in the magnetic core cavity, vertical windings are arranged on both side walls of the plurality of narrow slots, and the vertical windings are connected by planar windings to realize a vertical PCB winding structure.

[0027] The present invention greatly improves space utilization by designing the conductors of some planar windings into a vertical structure, combining the vertical windings with the planar windings, and changing the arrangement of the conductors, so that the conductors have a more uniform current density when used at high frequencies, thereby reducing the influence of the skin effect and the proximity effect on the device impedance, thereby achieving a low-loss, high-efficiency PCB winding design. Compared with planar windings, the vertical PCB winding structure has lower ESR loss; compared with Litz wire, it has higher current and power density.

[0028] It should be noted that the skin effect is that when an alternating current flows through a conductor, the distribution of the current on the conductor cross section is uneven, the current density on the conductor surface is large, the current density in the center is small, and the current density decays exponentially from the surface to the center. The proximity effect refers to when two adjacent conductors pass current, if the current directions are the same, then due to the mutual interaction of the alternating magnetic fields they generate, the induced back electromotive force on the adjacent side of the two conductors is the largest, and the current is driven to flow through the outside of the conductor; on the contrary, when the current directions are opposite, the current is driven to flow through the adjacent side of the two conductors, that is, the inside. The proximity effect increases the AC resistance of the conductor, thereby increasing the loss. In high-frequency circuits, the skin effect and the proximity effect often exist at the same time and affect each other, and jointly affect the impedance of the device, resulting in changes in the impedance value and a decrease in transmission performance. The present invention designs the planar winding in the prior art as a vertical winding, changes the arrangement of the winding, and reduces the influence of the skin effect and the proximity effect on the impedance of the device.

[0029] It should be noted that Litz wire is made of multiple single wires with insulated surfaces twisted or woven according to a certain lay length and direction; from the cross-section, each single wire tends to occupy every possible position. This design helps to balance the continuity of the magnetic current; the strands are connected in parallel, which can balance the current distribution and reduce the influence of skin effect and proximity effect.

[0030] It should be noted that ESR is the equivalent resistance that measures the energy loss of a capacitor under specific working conditions. ESR is an important indicator for measuring capacitor performance, especially in high-frequency and high-voltage circuits. The smaller the ESR, the better the performance of the capacitor.

[0031] In some embodiments, the number of narrow slots is determined according to the number of turns of winding required in the magnetic core cavity, one narrow slot is set for every two turns of winding, and vertical windings are set on the two side walls of the narrow slot to achieve higher space utilization. In addition, in order to achieve sufficient mechanical strength, the vertical windings in each narrow slot are connected by planar windings, and the spacing between the planar windings should be large enough to reduce the influence of the proximity effect on the impedance.

[0032] In some embodiments, the vertical winding uses a copper conductor, and the copper conductor is arranged on the side wall of the narrow slot by a copper cladding or patch copper foil process. The planar winding adopts a patch copper foil process. The copper cladding process can provide excellent conductive properties to ensure efficient and stable circuit signal conduction. The patch copper foil process is relatively simple to process, can be designed according to requirements, and has good adaptability. In practical applications, the appropriate process can be selected by comprehensively considering factors such as conductive properties, heat dissipation properties, mechanical properties, and cost.

[0033] In some embodiments, the magnetic core is a ferrite core, which is mainly composed of iron oxide, manganese, zinc, nickel and other substances and is a high-frequency magnetic conductive material. The ferrite core has the advantages of high resistivity, small eddy current loss and high magnetic permeability, and is suitable for high-frequency applications.

[0034] In some embodiments, according to L=u0N 2 A e / l a , B m =u0Ni m / l a and A w= NI / k c jCalculate the core parameters required for specific applications, including the effective cross-sectional area Ae, window cross-sectional area Aw and air gap length la. According to the calculated core parameters and actual applications, select a core with a shape such as EI or EE so that the core is not saturated under normal working conditions. Using EE cores has the advantages of large lead space and strong heat dissipation capacity; choosing EI cores has the advantages of compact structure and low loss. Cores made of different core materials have different saturation flux densities. For example, the saturation flux density of PC40 and PC95 is about 0.5T. When designing, it is necessary to determine the maximum operating flux density based on the current in the inductor, the number of coil turns, the inductance value and the effective cross-sectional area of ​​the core to avoid excessive flux density, the core entering the saturation zone, resulting in a decrease in inductance and an increase in core loss.

[0035] Where, L is the inductance, N is the number of turns, Ae is the cross-sectional area of ​​the core, i m is the peak current in the device, B m is the saturation magnetic flux density, l a is the air gap length, u0 is the vacuum permeability, N is the number of turns, I is the effective value of the current, kc is the winding filling factor, and j is the current density In some embodiments, the shape n of the narrow slot is deformed, n≥4, and the narrow slot can be a quadrilateral, a pentagon, etc., and the corners are minimized as much as possible according to actual needs. The fewer the corners, the less additional impedance is generated at the connection, and the difficulty of processing can also be reduced.

[0036] In some embodiments, the narrow slot width should be at least greater than 1.2 mm to meet the process requirements of arranging a three-dimensional winding in the narrow slot.

[0037] In some embodiments, metal edging can also be used to provide a new conductive path for the inductive current. The precise design of the copper conductor edging is achieved through the following process: first, metal edging is performed on each side of the narrow slot, and then the edging metal layer is cut off by punching holes to achieve the target structure. In specific operations, since the metal edging process is difficult to accurately distribute in a local area of ​​the side wall of the PCB board to form a complete inductive current loop, the entire side wall can be fully metal edged first, and then the local area metal edging can be disconnected by punching holes.

[0038] The vertical PCB winding structure capable of reducing AC loss of the present invention is applied to the PCB inductor of the ultra-thin power supply. The present invention can greatly reduce the volume of the transformer and the inductor by efficient space utilization; and reduce the power consumption of the transformer by optimizing the structure of the PCB winding. Since the vertical structure is conducive to heat dissipation and reducing the interference and leakage of the magnetic field, the efficiency of the transformer can usually reach a higher level and improve the stability of the transformer. The vertical structure makes it easier to integrate the transformer and the inductor with other electronic components to form a compact and efficient power supply system.

[0039] Example 1 See also Figure 1 and Figure 6 As shown, in this embodiment, a vertical structure of the PCB winding is achieved by opening a narrow groove on the PCB substrate and coating the side wall with copper.

[0040] The vertical PCB winding structure provided in the present embodiment includes a PCB substrate, and an EI type ferrite core is arranged in a slot on the PCB substrate. The EI-shaped core is selected because the EI core has the advantages of compact structure and small size, and then the specific model of the EI core is selected based on the calculated effective cross-sectional area of ​​the core and the window cross-sectional area. Four narrow slots are arranged on the PCB substrate in the cavity of the EI type ferrite core, and the copper conductor is arranged on the side wall of the narrow slot through the copper cladding process. The copper conductor is partially arranged in the EI type ferrite core, and the copper conductors in the narrow slot are connected by copper foil to realize the vertical PCB winding structure. In the present embodiment, the narrow slot is in the shape of a quadrilateral, and the width of the narrow slot is 1.5 mm.

[0041] like Figure 2 and Figure 3As shown, it is a schematic diagram of the distribution of current density in the conductor in the planar PCB winding and the vertical PCB winding of Example 1. In the planar PCB winding, due to the influence of the proximity effect between the conductors, the current density distribution inside the conductor is relatively uneven, and the current is concentrated on the inner side of the winding. In the vertical PCB winding, firstly, due to the high space utilization rate and the large spacing between the conductors, the influence of the proximity effect is weakened; secondly, the vertical structure has a larger coverage area in the direction of higher current density, which is conducive to a more uniform distribution of current density. Under the same experimental conditions, the difference between the maximum current density and the minimum current density in the conductor of the traditional planar winding is about 10.23% of the average current density, while it is only 0.89% in the vertical winding.

[0042] like Figure 4 and Figure 5 As shown, it is a schematic diagram of the simulation structure of the planar PCB winding and the vertical PCB winding of Example 1. After parameter calculation, the planar winding inductance and the vertical winding inductance with an inductance value of 22uH at 1MHz are designed. Under the condition of the same copper coating thickness, the copper conductor width and spacing of the planar PCB winding are optimized to obtain the lowest impedance layout of the planar winding. The simulation shows that the winding ESR at this time is about 95mΩ; while the vertical winding structure with the same inductance value has an ESR of 66mΩ, which is 30.52% lower than that of the planar winding.

[0043] The above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, a person skilled in the art can still modify or make equivalent substitutions to the specific implementations of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention are within the scope of protection of the claims of the present invention to be approved.

Claims

1. A vertical PCB winding structure that can reduce AC losses, It is characterized in that The invention comprises a PCB substrate, a magnetic core is arranged on the PCB substrate through a groove, a cavity is arranged on the magnetic core, a plurality of narrow grooves are arranged on the PCB substrate in the magnetic core cavity, vertical windings are arranged on both side walls of the plurality of narrow grooves, and the vertical windings are connected through a planar winding.

2. A vertical PCB winding structure capable of reducing AC loss according to claim 1, It is characterized in that The number of the narrow slots is determined according to the number of turns of the winding required in the magnetic core cavity, one narrow slot is arranged for every two turns of the winding, and vertical windings are arranged on two side walls of the narrow slot.

3. A vertical PCB winding structure capable of reducing AC loss according to claim 1, It is characterized in that The vertical winding uses copper conductors, which are arranged on the side walls of the narrow slots through the process of copper cladding or copper foil patching.

4. A vertical PCB winding structure capable of reducing AC loss according to claim 1, It is characterized in that The magnetic core is selected as an EI type or an EE type magnetic core according to magnetic core parameters and actual applications. The magnetic core parameters include an effective cross-sectional area of ​​the magnetic core, a window cross-sectional area and an air gap length.

5. A vertical PCB winding structure capable of reducing AC loss according to claim 4, It is characterized in that The effective cross-sectional area of ​​the magnetic core, the air gap length and the window cross-sectional area are calculated according to L=u 0 N 2 A e / l a , B m =u 0 Ni m / l a and A w= NI / k c jCalculate; Where, L is the inductance value, u 0 is the vacuum magnetic permeability, N is the number of turns, Ae is the cross-sectional area of ​​the core, l a is the air gap length, B m is the saturation magnetic flux density, i m is the peak current in the device, Aw is the window cross-sectional area, I is the effective current, kc is the winding filling factor, and j is the current density.

6. A vertical PCB winding structure capable of reducing AC loss according to claim 1, It is characterized in that The magnetic core is a ferrite core.

7. A vertical PCB winding structure capable of reducing AC loss according to claim 1, It is characterized in that The narrow groove shape is n-deformed, n≥4.

8. A vertical PCB winding structure capable of reducing AC loss according to claim 1, It is characterized in that The width of the narrow groove is greater than or equal to 1.2 mm.

9. A vertical PCB winding structure capable of reducing AC loss according to claim 1, It is characterized in that The planar winding adopts the copper foil patch process.

10. A PCB inductor for ultra-thin power supply, It is characterized in that A vertical PCB winding structure capable of reducing AC loss as described in any one of claims 1 to 9.

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