Low-loss planar inductor core and method of designing the same

Abstract

The application discloses a low-loss planar inductor magnetic core and a design method thereof. The planar inductor magnetic core comprises an upper magnetic yoke and a lower magnetic yoke, a left column, a right column and a middle column. The upper magnetic yoke and the lower magnetic yoke, the left column, the right column and the middle column form a full-enclosed structure on the side surface, eliminating the traditional air gap structure. The upper magnetic yoke and the lower magnetic yoke are made of a first magnetic core material. The left column, the right column and the middle column are made of a second magnetic core material. The magnetic permeability of the first magnetic core material is lower than that of the second magnetic core material. The magnetic resistance of the planar inductor magnetic core is symmetrically distributed about a transverse symmetry axis. The magnetic core has a simple structure and is easy to implement, can significantly reduce the high-frequency copper loss of a high-frequency power magnetic component, and effectively solves the problem that the existing winding structure optimization method for MMF distribution optimization cannot be applied to the inductor.

Description

Technical Field

[0001] The present invention relates to a planar inductor optimization design, in particular to a low-loss planar inductor magnetic core and a design method thereof. Background Art

[0002] With society's ever-increasing demand for electricity and the increasing role of power electronics in all aspects of electricity production, transmission, and consumption, the design and application of high-frequency, low-loss, high-power-density power electronic converters for small and medium power levels are becoming increasingly important. Simultaneously, the emergence of a new generation of power semiconductor switching devices, represented by silicon carbide and gallium nitride, is further increasing the switching frequency of power electronic converters, reaching hundreds of kHz or even exceeding MHz.

[0003] Increasing switching frequency helps reduce the size of power magnetic components in converters, but this also increases the AC losses of power magnetic components, especially planar power inductor windings, further increasing the AC / DC resistance ratio of the windings. In planar inductors, the edge effects of the core and air gap become more severe with increasing frequency. Furthermore, to achieve sufficient inductance in a small size, the proximity effect of multi-layer, multi-turn inductors becomes more pronounced. These enhanced edge and proximity effects further increase the AC copper losses of the windings. The heat dissipation issues caused by increased losses hinder the reduction of planar magnetic components, thereby reducing the size reduction benefits of increased frequency.

[0004] Existing low-loss optimization design methods for magnetic components fall into two categories: one involves optimizing winding width, thickness, and number of turns, as well as Litz-wire-like structures and vertical and lateral transpositions. However, winding optimization is powerless to optimize magnetic field distribution and MMF, and cannot address the problem of winding AC losses from a more fundamental "field" perspective. The staggered winding structure widely used in transformers, while very effective, cannot be applied to inductors. The second category involves optimizing the core structure. Current core optimization methods primarily focus on optimizing the air gap, including quasi-distributed air gap structures and distributed air gap structures. These can weaken the edge effect of the air gap, but the air gap still exists and cannot simultaneously optimize the MMF, thus failing to address the significant proximity loss problem in multilayer inductors. Furthermore, the effectiveness of quasi-distributed air gaps relies on increasing the number of air gaps while reducing the geometric dimensions of each air gap. This places high demands on the core's processing capabilities, leading to increased processing complexity and decreased yield. The low magnetic permeability part in the traditional distributed air gap structure occupies a small volume, so the relative magnetic permeability of the material is required to be low. It is difficult to find suitable materials with extremely low relative magnetic permeability and good loss characteristics, so it has not been widely used in the industry. Summary of the Invention

[0005] In order to solve the above problems, the application provides a low-loss planar inductor magnetic core structure and a design method thereof.

[0006] In order to achieve the above object, the application adopts the following technical scheme:

[0007] The low-loss planar inductor magnetic core comprises an upper magnetic yoke, a lower magnetic yoke, an inductor winding, a left column, a right column and a middle column; the upper magnetic yoke and the lower magnetic yoke, the left column, the right column and the middle column form a full side surrounding structure; the inductor winding passes through the middle column and is surrounded by the upper and lower magnetic yokes and the left and right columns.

[0008] The upper magnetic yoke and the lower magnetic yoke are made of a first magnetic core material; the left column, the right column and the middle column are made of a second magnetic core material; and the magnetic permeability of the first magnetic core material is lower than that of the second magnetic core material; the magnetic reluctance of the planar inductor magnetic core presents a symmetric distribution about a transverse symmetry axis.

[0009] As a further improvement of the application, the first magnetic core material is a metal soft magnetic material; and the magnetic permeability is 16-150.

[0010] As a further improvement of the application, the second magnetic core material is a power ferrite material; and the magnetic permeability is 600-3000.

[0011] As a further improvement of the application, the distribution of the magnetic motive force (MMF) amplitude of the planar inductor magnetic core presents a V-shaped transverse symmetric distribution.

[0012] As a further improvement of the application, the inductor winding is arranged on the transverse symmetry axis of the magnetic core.

[0013] As a further improvement of the application, the inductor winding is a copper foil winding based on a PCB.

[0014] As a further improvement of the application, the left column and the right column are arranged in parallel, and the upper magnetic yoke and the lower magnetic yoke are arranged in parallel and form the full side surrounding structure with the left column and the right column.

[0015] The design method of the low-loss planar inductor magnetic core comprises the following steps:

[0016] designing a magnetic core structure with a target inductance value L, an air gap and being completely composed of a high relative magnetic permeability μ rh material to obtain a high magnetic permeability value μ rh and basic geometric parameters related to the magnetic core.

[0017] According to the principle of magnetic reluctance conservation, the total magnetic reluctance of the magnetic core is not changed before and after the change of structure and material, and the relative magnetic permeability mu of the low relative magnetic permeability material suitable for the upper and lower magnetic yokes is obtained by the following method rl is:

[0018]

[0019] Wherein, delta 1 and delta 2 are the height of the upper and lower magnetic yokes; w1 and w2 are the width of the side column and the middle column respectively; k f1 and k f2 Are the amplification coefficients of the area equivalent expansion of the side column and the middle column due to the edge effect; l y Is the width of the magnetic core; g is the air gap length.

[0020] As a further improvement of the application, the high magnetic permeability value mu rh And the basic geometric parameters and key geometric parameters related to the magnetic core, such as air gap length g, are obtained by the following method:

[0021]

[0022] G≈l c / Mu rh

[0023] Wherein, B max Is the maximum magnetic density allowed by the magnetic core material; l c Is the effective magnetic path length of the magnetic core; K i Is the waveform coefficient of the excitation current; mu0 is the magnetic permeability of vacuum; P d_max Is the maximum dissipation power allowed by the magnetic core; k u Is the window utilization rate of the magnetic core; A w Is the window area of the magnetic core; rho w Is the electrical conductivity of copper; MLT is the average length of single-turn winding.

[0024] Compared with the prior art, the application has the following advantages:

[0025] The planar inductor with transverse symmetrical magnetic reluctance distribution structure characteristics has two kinds of magnetic conductive materials with large difference in relative magnetic permeability, and the magnetic reluctance of the whole magnetic core is symmetrically and centrally distributed in the upper and lower magnetic yokes by reasonable distribution. Through the design of transverse symmetrical distribution of magnetic reluctance, the difficulty of optimizing the MMF distribution in the inductor by optimizing the winding structure is solved. The magnetic core of the structure not only eliminates the traditional air gap structure, makes the magnetic field in the magnetic core window more parallel to the PCB winding, and weakens the edge effect of the magnetic core; at the same time, the distribution of MMF is also optimized, and the maximum value is reduced to half of that in the traditional structure, and the adjacent loss of the winding is reduced.

[0026] In addition, the planar inductor with the transverse symmetrical magnetic reluctance distribution structure does not contain the traditional air gap structure, so the edge effect of the inductor is greatly weakened compared with the inductor with the air gap; meanwhile, the low magnetic permeability material is arranged at the positions of the upper and lower yokes parallel to the PCB winding, and the high relative magnetic permeability material is reserved at the left and right side columns and the center column perpendicular to the PCB winding, so that the material combination can optimize the magnetic field distribution in the magnetic core window, make the distribution more parallel to the PCB winding, and weaken the edge effect at the corners of the magnetic core to some extent, thereby reducing the edge loss of the winding.

[0027] The magnetic core with the transverse symmetrical magnetic reluctance distribution structure has the benefits of weakening the edge effect and the proximity effect, and the benefits are more obvious with the increase of the excitation frequency within a certain range, so the magnetic core is very suitable for loss reduction of high-frequency magnetic components.

[0028] Meanwhile, the optimization design of the magnetic core structure of the application does not involve complex geometric structures, and the structure is simple and easy to mass produce after design. Meanwhile, the application has certain universality and can be applied to various magnetic cores of planar inductors. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 It is a side view of a traditional EI-type magnetic core structure with an air gap and related geometric parameters;

[0030] Figure 2 It is a side view of the magnetic core structure of the planar inductor with the transverse symmetrical magnetic reluctance distribution structure and related geometric parameters;

[0031] Figure 3 It is a front view of the magnetic core structure of the planar inductor and related geometric parameters;

[0032] Figure 4 It is a comparison of the finite element simulation results of the MMF distribution of the planar inductor with the transverse symmetrical magnetic reluctance distribution structure and the traditional planar inductor with the air gap;

[0033] Figure 5 Based on the finite element simulation analysis, (a) is the vector distribution of the magnetic field strength H in the magnetic core window of the planar inductor with the transverse symmetrical magnetic reluctance distribution structure; (b) is the vector distribution of the magnetic field strength H in the magnetic core window of the traditional planar inductor with the air gap;

[0034] Figure 6 It is a comparison of the finite element simulation of the effect of reducing the winding ac resistance of the planar inductor with the transverse symmetrical magnetic reluctance distribution structure at different frequencies. DETAILED DESCRIPTION

[0035] In order to make the person skilled in the art better understand the technical scheme of the present application, the technical scheme in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts shall fall within the scope of protection of the present application.

[0036] It should be noted that the terms "first", "second" and the like in the description and claims of the present application and the above drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or a chronological sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device that includes a series of steps or units need not be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0037] As shown in Figure 2 The present application provides a planar inductor magnetic core structure and design concept with a transverse symmetry distribution structure characteristic of magnetic resistance based on two kinds of magnetic core materials with large relative magnetic permeability difference. The traditional air gap structure is eliminated in the magnetic core structure, which specifically includes an upper magnetic yoke 1 and a lower magnetic yoke 5 with low relative magnetic permeability, left and right columns 2 and 6 and a middle column 3 with high relative magnetic permeability, and a multi-layer PCB winding 7 located in the center of the magnetic core.

[0038] The proposed magnetic core structure with transverse symmetry distribution of magnetic resistance is applicable to various types of planar inductor magnetic cores, and the inductor winding is a copper foil winding based on PCB.

[0039] The magnetic core is made of two kinds of magnetic core materials with large difference in magnetic permeability. The upper magnetic yoke and the lower magnetic yoke are made of a first magnetic core material; the left and right columns and the middle column are made of a second magnetic core material; and the magnetic permeability of the first magnetic core material is generally much lower than that of the second magnetic core material. Taking the transformation of a traditional EI type inductor magnetic core into a magnetic resistance symmetry distribution structure as an example: the upper magnetic yoke 1 and the lower magnetic yoke 5 are made of metal soft magnetic materials, which have a relatively low relative magnetic permeability (usually between 16 and 150); the left and right columns and the middle column are made of power ferrite materials, which have a relatively high relative magnetic permeability (usually between 600 and 3000).

[0040] The magnetic core is tightly combined between each part to form a whole, without the need for a traditional air gap structure 9.

[0041] PCB inductor winding 7 is through the middle column 3, surrounded by the upper yoke 1, the lower yoke 5 and the left column 2, the right column 6, and placed on the magnetic core transverse symmetry axis.

[0042] The design principle of the planar inductor magnetic core structure with transversely symmetrically distributed magnetic reluctance is the magnetic reluctance conservation principle, and any conventional structure magnetic core can be optimized and improved.

[0043] The power inductor is a planar inductor, and the winding of the inductor is a PCB-based copper foil winding 7. The magnetic core contains two kinds of magnetic core materials with large relative magnetic permeability difference, one is a metal soft magnetic material with low relative magnetic permeability, and the other is a power ferrite material with high relative magnetic permeability.

[0044] The metal soft magnetic material is used for the upper yoke 1 and the lower yoke 5, which provides the main magnetic reluctance in the magnetic circuit, that is, the magnetic reluctance of the magnetic circuit is concentrated in the upper and lower yoke parts of the overall magnetic core structure geometry, showing a transversely symmetric distribution; the power ferrite material is used for the left column 2, the right column 6 and the middle column 3, and the magnetic reluctance is very small.

[0045] The upper and lower yokes made of low relative magnetic permeability replace the air gap 7 of the traditional inductor to bear the magnetic pressure drop in the magnetic circuit, so the planar power inductor with transversely symmetrically distributed magnetic reluctance is an air gap-free inductor.

[0046] The transversely symmetrically distributed magnetic reluctance optimizes the distribution of the magnetic motive force (MMF) on the inductor winding, and the amplitude of the MMF presents a "V" type distribution, which is consistent with the distribution of the magnetic reluctance of the magnetic core; and the maximum value of the MMF is halved, reducing the proximity loss of the winding. The MMF distribution in the new structure inductor no longer monotonically increases with the number of layers, but presents a "V" type distribution; compared with the traditional structure inductor under the same conditions, the maximum value of the MMF in the new structure inductor is halved, so the proximity loss of the winding can be effectively reduced.

[0047] As shown in Figures 2 to 6 Taking a traditional EI type magnetic core as an example, the magnetic core structure develops from the EI type magnetic core. The specific structure is that the entire magnetic core is made of two different magnetic core materials, the upper yoke 1 and the lower yoke 5 of the magnetic core are made of a metal soft magnetic material with low relative magnetic permeability; the left column 6, the right column 2 and the middle column 3 of the magnetic core are made of a power ferrite material with high relative magnetic permeability. Therefore, the magnetic reluctance of the magnetic core is mainly concentrated in the upper and lower yokes, thus showing a symmetric distribution about the transverse symmetry axis of the magnetic core as a whole, and the distribution of the magnetic motive force amplitude MMF in the magnetic core window 4 also presents a "V" type transversely symmetric distribution as shown by the solid line in the middle. Figure 4

[0048] ​The magnetic core is a structure with one side fully surrounded. Since the low relative permeability material in the upper yoke 1 and the lower yoke 5 is used to bear most of the magnetic pressure drop in the magnetic circuit and prevent the magnetic core from being saturated, it is not necessary to open an air gap in the magnetic core. In addition, in order to make full use of the magnetic core, the PCB winding 7 should be placed in the center of the magnetic core window 4 to obtain the MMF distributed in space as much as possible, that is, the PCB winding is located at the position of the transverse symmetry axis of the magnetic core.

[0049] The design method of the magnetic core structure with transverse symmetry distribution of magnetic reluctance includes two steps:

[0050] First, the geometric size of the magnetic core with a target inductance L, a traditional single material, and an air gap is designed by using the AP method. Specifically, the geometric size of the magnetic core with a target inductance L, an air gap, and a high relative permeability μ rh material is designed to obtain a suitable high permeability value μ rh and basic geometric parameters such as the air gap length g related to the magnetic core; the relative permeability μ rh of the high permeability material and the key geometric parameters such as the air gap length g are obtained as shown in equations 1 and 2:

[0051]

[0052] g≈l c / μ rh (2)

[0053] where B max is the maximum magnetic density allowed by the magnetic core material; l c is the effective magnetic circuit length of the magnetic core; K i is the waveform coefficient of the exciting current; μ0 is the permeability of vacuum; P d_max is the maximum allowable dissipation power of the magnetic core; k u is the window utilization rate of the magnetic core; A w is the window area of the magnetic core; ρ w is the electrical conductivity of copper; and MLT is the average length of a single turn winding. Taking the conversion of a traditional EI magnetic core into a magnetic core with transverse symmetry distribution of magnetic reluctance as an example, according to the principle of magnetic reluctance conservation, the total magnetic reluctance of the magnetic core before and after the structure and material change is ensured to be unchanged, that is, the inductance value is ensured to be unchanged before and after the structure conversion. The basic geometric parameters of the traditional single material magnetic core with an air gap obtained by the above AP method are used as the geometric size parameters of the new structure magnetic core.

[0054] Secondly, the geometric size of the magnetic core obtained above is used as the basic geometric size parameter of the new structure magnetic core after being converted into a magnetic core with transverse symmetry distribution of magnetic reluctance, that is, the size of the magnetic core is basically unchanged. Taking the conversion of an EI magnetic core as an example, the air gap is eliminated, and the materials in the upper yoke 1 and the lower yoke 5 are replaced with a material with a relative permeability μrl Low permeability metal magnetic powder core material, according to the principle of magnetic resistance conservation, μ is calculated as shown in formula 3 rl :

[0055]

[0056] Wherein δ1 and δ2 are the height of the upper and lower yokes; w1 and w2 are the width of the side column and the middle column respectively; k f1 and k f2 are the amplification coefficients of the area equivalent expansion of the side column and the middle column due to the edge effect; l y is the width of the magnetic core.

[0057] Example 1

[0058] The magnetic resistance transverse symmetry distribution structure and design concept proposed in the present application are applicable to magnetic cores of various types of planar inductors, and the following implementation is described for the purpose of transforming the traditional EI type magnetic core.

[0059] Reference Figure 1 is a traditional EI type inductor magnetic core, which specifically includes an upper yoke 8, an air gap structure 9 and an E type magnetic element 10. The magnetic resistance distribution is designed to be transversely symmetrical, which is developed from the concept of distributed air gap structure: the traditional EI type magnetic core is converted into the planar inductor magnetic core with transverse symmetry distribution structure proposed in the present application as shown in Figure 2 , which specifically includes an upper yoke 1, a lower yoke 5, a left side column 2, a right side column 6, a middle column 3 and a magnetic core window 4.

[0060] In order to make the magnetic resistance of the magnetic core present a transverse symmetry distribution, two kinds of magnetic materials with relatively large difference in relative permeability are needed to construct each component of the magnetic core. Among them, the upper yoke 1 and the lower yoke 5 need to provide the main magnetic resistance in the magnetic circuit, so they need to be made of materials with low relative permeability. At the same time, attention needs to be paid to reducing the increase of magnetic core loss in the design of the magnetic core structure, so the iron-silicon metal magnetic powder core material belonging to the metal soft magnetic material is finally selected, which has slightly higher high-frequency loss than ferrite or comparable to ferrite under high-frequency excitation, and can provide some specific values of relative permeability between 16 and 125, which can meet the design requirements of power inductors in high-frequency converters. The left side column 2 and the right side column 6 and the middle column 3 are still composed of power ferrite with relatively high relative permeability.

[0061] The selection of appropriate permeability, that is, the design method of the planar inductor magnetic core with transverse symmetry distribution structure of magnetic resistance includes two steps:

[0062] First, the target inductance L is completed by AP method, the geometry size of the magnetic core made of single high relative permeability material and containing air gap is designed, as shown in formula 1 and 2, the key geometric parameters such as air gap length g and the relative permeability of high permeability material μ are obtained rh :

[0063]

[0064] g≈l c / μ rh (2)

[0065] Then, the magnetic core geometry size obtained above is taken as the basic geometric size parameter of the new structure of the magnetic core after being converted into the transverse symmetrical distribution structure of magnetic resistance, that is, the size of the magnetic core is basically unchanged, taking the conversion of EI type magnetic core as an example, the air gap is eliminated, the material of the upper yoke 1 and the lower yoke 5 is replaced by low permeability metal magnetic powder core material with relative permeability μ rl , and the appropriate μ rl is calculated according to the principle of magnetic resistance conservation, as shown in formula 3.

[0066]

[0067] Finally, in the example of the present application, the iron-silicon metal magnetic powder core material with relative permeability of 16 and the manganese-zinc ferrite material with relative permeability of 900 are selected as the materials of the upper yoke 1, the lower yoke 5, and the left column 2, the right column 6 and the middle column 3, respectively, and the design of the planar inductor with inductance of 13 μH is completed.

[0068] Due to the existence of the low permeability upper and lower yokes 1, 5, the traditional air gap structure 9 is eliminated in the planar inductor with transverse symmetrical distribution structure of magnetic resistance proposed in the present application, and the overall magnetic core structure presents a kind of structure of being fully surrounded on the side. At the same time, in order to maximize the reduction of the adjacent loss brought by the transverse symmetrical distribution of MMF after the transverse symmetrical distribution of magnetic resistance and the halving of the maximum value, the PCB winding 7 should be located at the position of the transverse symmetrical axis of the magnetic core window 4 by filling some non-magnetic material.

[0069] Reference Figure 4 According to the quantitative finite element simulation analysis results of the MMF distribution in the planar inductor with transverse symmetrical distribution structure of magnetic resistance proposed in the present application and the traditional magnetic core inductor, it can be seen that the optimization design of the magnetic resistance distribution effectively optimizes the distribution of MMF: from monotonic increasing to "V" type distribution, and the maximum value is reduced from about 11.3 kA / m to about 6.2 kA / m, thereby effectively reducing the size of the winding adjacent loss.

[0070] Reference Figure 5Fig. 2 is a comparison of the vector distribution of the magnetic field intensity H in the left half of the core window 4 of the conventional magnetic core inductor and the vector distribution of the magnetic field intensity H in the magnetic core of the planar inductor with the magnetic resistance transverse symmetrical distribution structure according to the present application; (a) is the vector distribution of H in the symmetrical magnetic resistance distribution structure core, which can be seen to have improved concentration of H compared to (b) the vector distribution of H in the conventional inductor with air gap; meanwhile, the distortion of H at the corners of the core is significantly reduced, and the magnetic field distribution in the core window 4 is more parallelized and homogenized relative to the PCB winding 7, thereby proving the effectiveness of the magnetic resistance transverse symmetrical distribution structure according to the present application in weakening the edge effect and improving the magnetic field distribution.

[0071] Reference Figure 6 Fig. 3 is a comparison of the winding AC resistance simulation results of the planar inductor with the magnetic resistance transverse symmetrical distribution structure based on finite element simulation and the conventional inductor with air gap; it can be seen that when the frequency of the applied current excitation is 300 kHz, 500 kHz, 800 kHz and 1 MHz respectively, the new structure core can reduce the winding AC resistance by about 40%, 47%, 52% and 53% respectively, thereby proving the effectiveness and feasibility of the optimized structure of the planar inductor with the magnetic resistance transverse symmetrical distribution structure according to the present application in reducing winding AC loss.

[0072] In summary, the planar inductor with the magnetic resistance transverse symmetrical distribution structure according to the present application includes upper and lower magnetic yokes, left and right side columns and a middle column, and an inductor winding based on a PCB copper foil. The core part is composed of two different magnetic conductive materials, the upper and lower magnetic yokes are made of low relative permeability ferrosilicon metal magnetic powder core material, which provides the main magnetic resistance in the magnetic circuit; the left and right side columns and the middle column are made of high relative permeability manganese-zinc ferrite material; the traditional air gap structure is eliminated in the core; thereby the magnetic resistance distribution of the overall core presents a transverse symmetrical distribution. The optimization of the magnetic resistance distribution can effectively optimize the distribution of the magnetic motive force on the winding in the core, making it present a similar "V" type distribution, and the maximum value of the MMF amplitude is reduced by about half, thereby effectively reducing the proximity loss of the winding; the combination of the low permeability components of the core and the PCB winding in parallel and the high permeability components of the core and the PCB winding perpendicular can also optimize the magnetic field distribution in the core window, weaken the edge effect of the core, and reduce the edge loss of the winding. The optimized core structure is simple and easy to implement, can significantly reduce the high-frequency copper loss of high-frequency power magnetic components, and at the same time solves the problem that the existing winding structure optimization method for MMF distribution optimization cannot be applied in inductors.

[0073] Many embodiments and many applications other than those described herein will be apparent to those skilled in the art from consideration of the specification and practice of the teachings herein. Therefore, the scope of the present teachings should be determined by the appended claims and equivalents thereof, rather than by the description alone. All articles and references, including patent applications and publications, are incorporated herein by reference for all that they contain. Any aspect of the subject matter disclosed herein that is not recited in the claims is hereby abandoned. The summary of the application is not intended to limit the scope of the application.

[0074] The above description is further detailed of the present application, and cannot be considered as limiting the specific embodiments of the present application to the above, and for those skilled in the art, without departing from the concept of the present application, a number of simple deductions or replacements can also be made, which should be considered as belonging to the present application determined by the submitted claims.

Claims

1. A method for designing a low-loss planar inductor core, characterized by: The low-loss planar inductor core includes an upper magnetic yoke, a lower magnetic yoke, an inductor winding, a left column, a right column, and a center column; the upper magnetic yoke, the lower magnetic yoke, the left column, the right column, and the center column form a fully enclosed structure; the inductor winding passes through the center column and is surrounded by the upper and lower magnetic yokes and the left and right side columns; The upper magnetic yoke and the lower magnetic yoke are made of a first magnetic core material; the left column, the right column and the middle column are made of a second magnetic core material; and the magnetic permeability of the first magnetic core material is lower than the magnetic permeability of the second magnetic core material; The magnetic resistance of the planar inductor core is symmetrically distributed about the transverse symmetry axis; The design method comprises: The target induction value is L, there is an air gap and it is completely composed of high relative magnetic permeability. μ rh The core structure composed of materials is designed to obtain high magnetic permeability values μ rh and the air gap length of the core g ; According to the principle of conservation of magnetic resistance, the relative permeability of the low relative permeability material suitable for the upper and lower magnetic yokes is obtained by the following method, while ensuring that the total magnetic resistance of the magnetic core remains unchanged before and after the structure and material changes. μ rl for: in δ 1 and δ 2 is the height of the upper and lower yokes; w 1 and w 2 is the width of the side column and the middle column respectively; k f1 and k f2 are the magnification coefficients of the equivalent expansion of the area of ​​the side columns and the middle column due to the edge effect; l y is the width of the core; g is the air gap length.

2. The method for designing a low-loss planar inductor core according to claim 1, wherein: The high permeability value obtained μ rh and the air gap length of the core g , the method used is as follows: in, B max The maximum magnetic flux density allowed by the core material; l c is the effective magnetic path length of the core; K i is the waveform factor of the excitation current; μ 0 is the magnetic permeability of vacuum; P d_max is the maximum power dissipation allowed by the magnetic core; k u is the core window utilization; A w is the core window area; ρ w is the electrical conductivity of copper; MLT is the average length of a single-turn winding.

3. The method for designing a low-loss planar inductor core according to claim 1, wherein: The first magnetic core material is a metallic soft magnetic material with a magnetic permeability of 16-150.

4. The method for designing a low-loss planar inductor core according to claim 1, wherein: The second magnetic core material is a power ferrite material with a magnetic permeability of 600-3000.

5. The low-loss planar inductor core according to claim 1, wherein: The distribution of the magnetomotive force amplitude MMF of the planar inductor core presents a V-shaped transversely symmetrical distribution.

6. The method for designing a low-loss planar inductor core according to claim 1, wherein: The inductor winding is placed on the transverse symmetry axis of the magnetic core.

7. The method for designing a low-loss planar inductor core according to claim 1, wherein: The inductor winding is a copper foil winding based on PCB.

8. The method for designing a low-loss planar inductor core according to claim 1, wherein: The left column and the right column are arranged in parallel, and the upper magnetic yoke and the lower magnetic yoke are arranged in parallel and form the side fully enclosed structure with the left column and the right column.

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