Wireless power transmission device for heat reduction and miniaturization, and control method thereof

Abstract

A wireless power transmission device and a control method thereof solve a heating problem caused in high-power wireless power transmission and provide miniaturization and weight reduction of a device. A relative phase difference of a current applied to each coil is actively controlled on the basis of a spatial relationship (spatial orthogonality or non-orthogonality) of multiple coils. A phase difference is applied to coils having spatial orthogonality so that magnetic field distribution of the magnetic body becomes uniform and hotspots are thus suppressed, and a current of the same phase is applied to coils having no spatial orthogonality so that the current is distributed and the resistive loss of the coil itself is thus reduced. In addition, through a structure in which different coils are arranged on the same plane or the shape and material of the magnetic body are optimized, the thickness and weight of the device are reduced and performance stability is increased. As a result, heat reduction, miniaturization, weight reduction, cost reduction, and performance improvement can be simultaneously achieved in the field such as an electric vehicle charger requiring high output.

Description

Wireless power transmission device for heat reduction and miniaturization and its control method

[0001] The present invention relates to the field of wireless power transmission technology, and more specifically, to a wireless power transmission device including a plurality of coils, which improves heat generation characteristics and achieves miniaturization by controlling the phase of current applied to coils or optimizing the structure of coils and magnetic bodies, and a control method thereof.

[0002] With the recent growth of the electric vehicle (EV) market and the spread of industrial automation, demand for high-power wireless power transfer technology is rapidly increasing. Wireless power transfer technology is attracting attention as a next-generation charging technology, as it maximizes user convenience and eliminates the risk of wear and sparks associated with mechanical contacts.

[0003] However, as the output of the wireless power transmission device increases, the size of the current flowing in the coil increases, resulting in resistance loss (copper loss, I) of the conductor itself. 2 The problem of heat generation due to R loss becomes serious. In particular, in wireless power transmission using high frequencies ranging from tens to hundreds of kHz, the skin effect and proximity effect cause the AC resistance of the conductor to be much larger than the DC resistance. The skin effect is a phenomenon in which high-frequency current does not penetrate the center of the conductor but only flows to the surface, and the proximity effect is a phenomenon in which the current is concentrated in one direction due to magnetic field interference between adjacent conductors. These phenomena reduce the effective cross-sectional area through which the current flows, increasing the resistance and ultimately causing serious heat generation.

[0004] A well-known conventional technique for reducing such high-frequency resistance loss is the use of Litz wire, which is made by carefully twisting numerous thin, insulated strands so that their positions are constantly shifted. The twisted structure of Litz wire ensures that all strands pass equally through the center and surface of the bundle, equalizing the impedance of each strand and, consequently, evenly distributing the total current across each strand. This mitigates skin and proximity effects, reducing coil heat generation and enhancing efficiency.

[0005] However, even if Litz wire is used to increase the efficiency of the coil itself, systems using multiple coils present another heating issue. Specifically, the magnetic fields generated from each coil overlap on the magnetic material, concentrating the magnetic flux at a specific point, forming a localized hotspot. These hotspots degrade the performance of the magnetic material and threaten the thermal stability of the device.

[0006] Furthermore, when using multiple coils to secure a wide charging area or positional freedom, a stacking method that simply stacks them vertically has been primarily used. This method inevitably increases the overall thickness of the device, which runs counter to the trend toward miniaturization and thinness demanded in space-constrained applications such as electric vehicles.

[0007] In short, conventional wireless power transmission technologies have had difficulty simultaneously resolving the problems of coil loss, localized heating of the magnetic material, and increased structural volume, and there is a high need for a new technology that satisfies high output, high efficiency, and miniaturization.

[0008] The present invention was conceived to address the aforementioned problems of prior art, and its primary purpose is to effectively address the problem of heat generation in high-power wireless power transmission devices. Specifically, the invention aims to simultaneously suppress both the coil's own resistance loss and the occurrence of localized hot spots in the magnetic material.

[0009] Another object of the present invention is to achieve miniaturization and lightweighting suitable for space-constrained applications such as electric vehicles by reducing the overall thickness and weight of the device while using multiple coils.

[0010] In addition, another object of the present invention is to improve the performance and reliability of a device by enabling stable power transmission even in a situation where the alignment between the transmitter and receiver is misaligned.

[0011] In order to solve the above-mentioned problem, according to one aspect of the present invention, a method for optimizing the heat generation characteristics of a wireless power transmission device including a plurality of coils and a magnetic body arranged to have a predetermined spatial relationship is provided, the method including a step of controlling a relative phase difference of currents applied to each coil forming the plurality of coils based on the spatial relationship.

[0012] It is preferable that the above plurality of coils be arranged so as to be spatially orthogonal to each other.

[0013] When the above plurality of coils are composed of two coils, the relative phase difference is controlled to 90 degrees.

[0014] The above two coils may be DD coils that are orthogonal to each other.

[0015] When the above plurality of coils are composed of three coils, the relative phase difference is controlled to 0 degrees, 45 degrees, and 135 degrees, respectively.

[0016] The above three coils can be one circular coil and two DD coils.

[0017] The above plurality of coils can be arranged so as not to be spatially orthogonal to each other.

[0018] The relative phase difference of the above plurality of coils is controlled to 0 degrees.

[0019] The above plurality of coils can be formed by overlapping N coils of the same shape (N is an integer greater than or equal to 2).

[0020] It is preferable that the above N coils are formed by branching each of the sub-bundles into N independent paths from a bundle of Litz wires consisting of a plurality of sub-bundles.

[0021] When N is 2, the total heat generation is reduced to half the level of when using a bundle of Litz wires.

[0022] The above plurality of coils may be composed of one circular coil and three DD coils arranged at an angle of 120 degrees to each other.

[0023] According to another aspect of the present invention, a wireless power transmission device is provided, comprising: a coil portion formed of a plurality of coils arranged to have a predetermined spatial relationship; a magnetic body arranged on one side of the coil portion; and a control portion that controls a relative phase difference of currents applied to each coil of the plurality of coils to optimize the heat generation characteristics of the device.

[0024] Preferably, the coil portion comprises a circular coil having an inner diameter capable of containing another coil therein, thereby reducing the increase in the overall thickness of the coil portion.

[0025] Preferably, the magnetic body includes a portion protruding into the empty space of the coil portion to minimize the amount of change in the mutual inductance value.

[0026] It is preferable that the above magnetic material be a hybrid magnetic material in which different types of magnetic materials are laminated.

[0027] The wireless power transmission device and its control method according to the present invention provide the following effects.

[0028] First, it fundamentally resolves the overheating problem, significantly improving thermal stability. The present invention suppresses localized hot spots in the magnetic material through phase difference control in spatially orthogonal structures, and directly reduces the coil's own resistive loss (copper loss) through in-phase control in non-orthogonal structures. This enhances device reliability and ensures stable operation even at high outputs.

[0029] Second, it achieves groundbreaking miniaturization and weight reduction of the device. By solving heat generation issues, thick magnetic materials and separate cooling systems can be eliminated, and the physical thickness is directly reduced through a structure that places different coils on the same plane. Furthermore, the use of hybrid magnetic materials reduces weight, making it highly advantageous for applications with severe space and weight constraints, such as electric vehicles.

[0030] Third, it provides stable performance under various operating conditions. The optimized magnetic material shape minimizes changes in mutual inductance values ​​even when the transmitter and receiver are misaligned, enabling stable power transmission even over a wide range of positional changes.

[0031] Fourth, it can reduce the manufacturing costs of the device. By reducing the use of expensive, high-performance magnetic materials and simplifying additional components such as cooling systems, the overall system production cost can be lowered, securing price competitiveness.

[0032] Fig. 1 is a perspective view showing a transmitter and a receiver of a wireless power transmission device according to Example 1 of the present invention.

[0033] Figure 2A is a diagram showing the distribution of a magnetic field formed in a magnetic body at a specific point in time in a comparative example of Example 1.

[0034] Figure 2B is a drawing showing the magnetic field distribution formed in the magnetic body at the same time as Figure 2A in Example 1.

[0035] Fig. 3 is a perspective view showing a transmitter and a receiver of a wireless power transmission device according to Example 2 of the present invention.

[0036] Figure 4A is a diagram showing the distribution of a magnetic field formed in a magnetic body at a specific point in time in a comparative example of Example 2.

[0037] Figure 4B is a drawing showing the magnetic field distribution formed in the magnetic body at the same time as Figure 4A in Example 2.

[0038] Fig. 5 is a plan view showing the structure of a hybrid phase control coil unit according to Example 3 of the present invention.

[0039] Figure 6A is a drawing showing the magnetic structure when the mutual inductance variation rate is maximum in Example 4.

[0040] Figure 6B is a drawing showing the magnetic body structure when the size of the magnetic body protrusion is at its maximum in Example 4.

[0041] Figure 6C is a drawing showing a magnetic structure in Example 4 when the mutual inductance variation rate is optimized to a minimum.

[0042] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. Identical or similar components are given identical or similar drawing reference numerals, and redundant descriptions thereof are omitted. In describing the embodiments disclosed in this specification, if a detailed description of a related known technology is judged to obscure the gist of the embodiments disclosed in this specification, the detailed description thereof will be omitted. The attached drawings are only intended to facilitate easy understanding of the embodiments disclosed in this specification, and the technical ideas disclosed in this specification are not limited by the attached drawings, and should be understood to include all modifications, equivalents, and replacements included in the spirit and technical scope of the present invention.

[0043] Terms containing ordinal numbers, such as "first," "second," etc., may be used to describe various components; however, these terms are used solely to distinguish one component from another and are not limited to the components in question. Singular expressions include plural expressions unless the context clearly indicates otherwise.

[0044] The terms “comprises,” “includes,” or “has” as used herein should be understood to limit the presence of a feature, step, component, or combination thereof described in the specification, but not to exclude the possibility that one or more other features, steps, components, or combinations thereof may be present or added.

[0045] The term 'Wireless Power Transfer Apparatus' used in this specification should be understood to comprehensively refer to a device that performs the role of transmitting power wirelessly or receiving power wirelessly as an individual functional unit constituting a wireless power transfer system, except in cases where it should be interpreted to have a different meaning in a specific context.

[0046] More specifically, in the present specification and claims, depending on its implementation form, the 'wireless power transmission device' may be a 'transmitting apparatus' including a coil and related circuitry for wirelessly supplying energy (e.g., a charging pad, a power supply rail, etc.), or a 'receiving apparatus' including a coil and related circuitry for wirelessly receiving the energy and transmitting it to a load (e.g., a battery) (e.g., a current collector mounted on an electric vehicle, a mobile device, a robot, etc.).

[0047] Accordingly, when a specific component or technical feature of the present invention is described as being applied or included in a "wireless power transmission device," this means that the component or feature may be applied to either a "transmitting device" or a "receiving device." In other words, the present invention may be implemented in either or both of a transmitting device and a receiving device.

[0048]

[0049] Heat reduction through phase difference control in spatial orthogonal structures

[0050]

[0051] The present invention presupposes a spatially orthogonal structure designed to minimize electromagnetic interference between a magnetic field generated from a specific coil and other coils when arranging multiple coils within a wireless power transmission device. This structure can be implemented, for example, by physically overlapping a DD coil that generates a horizontal magnetic field with a DD coil that generates a vertical magnetic field, or by adding a circular coil thereto to form a three-layer configuration.

[0052] If, in this spatially orthogonal structure, currents of the same phase are applied to each coil or phase control is not applied, the magnetic field vectors generated by each coil at a certain point geometrically add up, resulting in excessive magnetic flux concentration in a specific region, such as the center of the magnetic body. This concentration of magnetic flux rapidly increases the power density in that area, directly causing localized heating, or "hotspots."

[0053] To address this issue, the present invention applies a technology that actively controls the relative phase difference of the AC current applied to each coil. For example, if currents with a 90-degree phase difference are applied to two orthogonal coils, the vector sum of the time-varying magnetic field does not remain at a specific point, but instead creates an effect similar to rotation. As a result, power density, previously concentrated at a specific time and location, is uniformly distributed temporally and spatially throughout the magnetic material.

[0054] Achieving this uniform power density within the magnetic material prevents localized flux saturation, fundamentally suppressing hot spots and core loss that result from it. This, in turn, ensures the thermal stability of the device and reduces the need for additional magnetic material thickness or a separate cooling system to dissipate heat. Therefore, the present invention directly contributes to miniaturization and weight reduction by reducing the overall thickness, weight, and cost of the device.

[0055]

[0056] Heat reduction through in-phase control in non-orthogonal structures

[0057]

[0058] Unlike approaches that utilize spatial orthogonality, the present invention also proposes a method to suppress heat generation by directly reducing the resistive loss (copper loss) generated within the coil itself. This is crucial for enhancing device efficiency and reliability, particularly in high-power transmission situations where high currents are essential.

[0059] This method is applied when intentionally forming a structure without spatial orthogonality by overlapping N coils (e.g., two circular coils or two DD coils) having the same shape (N is an integer greater than or equal to 2). The core of the invention is to control the relative phase difference to 0 degrees (in-phase) so that the current applied to each coil thus arranged always has the same phase.

[0060] This structure can utilize a bundle of Litz wires, which are physically twisted into multiple sub-bundles. The present invention implements this by branching each sub-bundle of Litz wire into N independent paths, so that each path forms a coil. Since each sub-bundle retains the characteristic of Litz wires having a complete twist structure in itself, the total current is distributed 1 / N to N paths (coils) with equal impedance.

[0061] The power loss (P) of a conductor is proportional to its resistance (R) and to the square of the current (I) (P=I 2 R) follows the physical principle. Therefore, if the total current I is distributed to N coils and only I / N current flows in each coil, the power loss occurring in each coil is (I / N). 2 R, i.e. 1 / N compared to a single conductor 2 decreases sharply to the level of N. Therefore, the total loss occurring in N coils is N x 1 / N. 2 = 1 / N. For example, in a structure using two coils (N=2), the current flowing in each coil is halved (1 / 2), so the loss occurring in each coil is (1 / 2). 2 The loss is reduced to 1 / 4 of the original value, and the total loss becomes 2 x 1 / 4 = 1 / 2.

[0062] As a result, the total heat generated by the system, calculated by adding up the losses of all N coils, is significantly reduced to 1 / Nth of the level when using a single coil. This method of directly reducing the resistance loss of the coil itself fundamentally suppresses heat generation during high-power transmission and contributes to increased device reliability and efficiency.

[0063]

[0064] Miniaturization through coil arrangement structure

[0065]

[0066] The present invention provides a method for optimizing the physical layout of multiple coils to achieve miniaturization by reducing the overall thickness of a wireless power transmission device. Typically, when using multiple coils, the stacking method, which stacks each coil on a different layer, inevitably increases the overall thickness of the device.

[0067] To address these issues, the present invention employs a horizontal, planar arrangement, rather than vertical stacking, when combining coils of different shapes. Specifically, in a structure that utilizes both a circular coil and a DD coil, the inner diameter of the circular coil is designed to be sufficiently large to accommodate the DD coil within it. This allows the circular coil and the DD coil to be placed together on the same plane (layer) without physically overlapping.

[0068] For example, when using three coils (a circular coil, a vertical DD coil, and a horizontal DD coil), even if two DD coils are stacked on top of each other, the circular coil is not stacked on top of the previous one, but is positioned so as to occupy the external space within the same layer as the DD coil structure. As a result, this structure has the direct effect of reducing the number of physical layers in the coil section, thereby reducing the overall thickness. This miniaturization is a very advantageous advantage in electric vehicles and various industrial equipment where space is critical.

[0069]

[0070] Weight reduction and performance improvement through magnetic structure optimization

[0071]

[0072] The present invention includes a method for improving the performance of a device and reducing its weight by optimizing the shape and material of a magnetic body that forms a path of a magnetic field as well as a coil.

[0073]

[0074] (1) Performance stabilization through optimal magnetic material shape

[0075] When transmitting wireless power, if the alignment of the transmitter and receiver is incorrect, the mutual inductance value between the coils changes significantly, making stable power control difficult.

[0076] To address these issues, the present invention proposes a structure that goes beyond simply using a flat plate-shaped magnetic body. Instead, it additionally places a magnetic body of optimal size and height in the empty three-dimensional space of the coil structure. This additional magnetic body acts as a "magnetic flux guide" that effectively guides the path of the magnetic field, minimizing the variation in mutual inductance between the device's normal position and its maximum deviation position.

[0077] As a result, stable power transmission is possible even under various alignment conditions, improving performance, which contributes to solving the size, weight, and cost issues of the device.

[0078]

[0079] (2) Lightweighting and cost reduction through hybrid magnetic materials

[0080] Typically, high-performance magnetic materials, such as ferrite, are heavy and expensive. To address these shortcomings, the present invention utilizes a hybrid structure that combines different types of magnetic materials.

[0081] Specifically, a structure can be formed by layering high-performance magnetic materials with high permeability and low-permeability magnetic materials. For example, high-performance magnetic materials can be used in core areas where the magnetic field is concentrated, while relatively lighter or cheaper materials can be used in other areas to achieve an overall balance.

[0082] This hybrid magnetic structure is an effective way to simultaneously achieve device weight reduction and cost reduction by reducing the total amount of expensive magnetic materials used while minimizing performance degradation.

[0083]

[0084] Example 1: Two-layer coil device with spatial orthogonality

[0085]

[0086] Fig. 1 is a perspective view showing a transmitter and a receiver of a wireless power transmission device according to one embodiment of the present invention. Referring to Fig. 1, a wireless power transmission device according to one embodiment of the present invention includes a wireless power transmission device (100) installed on the ground, underground, or in a structure to supply power, and a wireless power reception device (200) mounted on an object to be supplied with power, such as an electric vehicle.

[0087] The key feature of this embodiment lies in the coil portion. The wireless power transmitter (100) and receiver (200) each include a coil portion composed of two DD (Double-D) coils arranged orthogonally therein. Specifically, the first DD coil is arranged to form a magnetic field along a first direction (e.g., X-axis), and the second DD coil is arranged to form a magnetic field along a second direction (e.g., Y-axis) perpendicular to the first direction. These two DD coils form a two-layer structure in which they are overlapped in different layers, thereby having spatial orthogonality that minimizes the influence of the magnetic field generated in one coil on the other coil. In the case of the wireless power transmitter, a magnetic material is arranged at the bottom of the coil portion to form a path for the magnetic field and prevent leakage to the outside.

[0088]

[0089] (1) In case of no phase control (comparative example)

[0090] First, as a comparative example to clearly compare the effects of the present invention, we will examine a case where the relative phase difference between the currents applied to the two DD coils is 0 degrees. This means that currents of the same phase flow through the two coils.

[0091] In this case, the magnetic fields generated by the current flowing through the transmitter and receiver coils combine at their strongest at a specific point, concentrating the field in the central portion of the receiver's magnetic material. This concentration of the magnetic field increases power loss in that area, potentially leading to localized heating, or "hotspots."

[0092] The results of quantitative analysis of this phenomenon are shown in the table below.

[0093] Unit of distinction: Total phase Mean: 86.905 mTesla Total phase Std: 20.792 mTesla Coefficient of variation: 23.925%

[0094] The meaning of each number in the table above and the calculation method are as follows. (a) Calculation method of the average magnetic field (overall phase mean) of a magnetic material

[0095] The overall phase Mean represents the average RMS magnetic field value formed throughout the specified magnetic material volume. This value is calculated through the following three steps.

[0096] * Step 1: Calculating the complex magnetic field magnitude (based on peak)

[0097] Through simulation, the complex-valued magnetic field vector components (Bx, By, Bz) at each point within the magnetic material are obtained. Using these values, the peak reference magnetic field magnitude (|Bcomplex|) at each point is calculated using the formula below.

[0098]

[0099] * Step 2: RMS conversion

[0100] Since it is an alternating magnetic field, the peak value obtained in step 1 is converted to an RMS (Root Mean Square) value. This is calculated by dividing the peak value by sqrt(2).

[0101]

[0102] This calculation can ultimately be expressed in the integrated formula below.

[0103]

[0104] * Step 3: Apply spatial averaging

[0105] B calculated in step 2 RMSThe values ​​are averaged over the entire volume of the magnetic material to obtain the spatial average RMS magnetic field value at that point in time (phase). This value corresponds to the Mean for each phase.

[0106] (b) Method for calculating the coefficient of variation (CV)

[0107] The coefficient of variation is a measure of how spatially uniform the magnetic field distribution is. A smaller value indicates a more uniform magnetic field distribution.

[0108] The overall phase Mean is a representative system average, obtained by averaging the phase-specific Mean values ​​calculated for all time phases (from 0 to 360 degrees) over time. Furthermore, the overall phase Std represents the standard deviation of the phase-specific Mean values ​​calculated across all time phases.

[0109] Therefore, the coefficient of variation is calculated using the formula below.

[0110] Coefficient of variation = (overall phase Std) / (overall phase Mean)

[0111] In conclusion, the coefficient of variation in the case without phase control is 23.925%, which quantitatively confirms that the magnetic field distribution within the magnetic material is relatively non-uniform.

[0112]

[0113] (2) In case of 90 degree phase control (embodiment of the present invention)

[0114] Next, we will examine a case in which the relative phase difference of the current applied to two DD coils is controlled to 90 degrees according to the present invention.

[0115] When the magnetic field formed in the receiver magnetic body is checked under the same conditions as when there is no phase control, it can be confirmed that the magnetic field is not concentrated in the center but is uniformly distributed across the pad.

[0116] The results of quantitative analysis of these effects are shown in the table below.

[0117] Unit of distinction: Total phase Mean: 86.932 mTesla Total phase Std: 7.038 mTesla Coefficient of variation: 8.096%

[0118] The most notable aspect of the table above is the coefficient of variation. Compared to the coefficient of variation of 23.925% without phase control, the coefficient of variation with 90-degree phase control significantly decreased to 8.096%. This quantitatively demonstrates a significant improvement in the uniformity of the magnetic field distribution within the magnetic material.

[0119] (3) Effect

[0120] In conclusion, applying 90-degree phase shift control to a two-layer coil structure with spatial orthogonality effectively distributes the power density generated in the magnetic material, suppressing localized heat generation. This enhances the thermal stability of the device and allows for a reduction in the thickness of the magnetic material and cooling system, directly contributing to device miniaturization and weight reduction.

[0121] FIG. 2A is a drawing showing the distribution of a magnetic field formed in a magnetic body at a specific point in time (phase 30 degrees) in a comparative example (phase difference 0 degrees) of the present invention, and FIG. 2B is a drawing showing the distribution of a magnetic field formed in a magnetic body at the same point in time (phase 30 degrees) in Example 1 of the present invention (phase difference 90 degrees).

[0122] The dark areas in the diagram indicate areas with strongly concentrated magnetic fields. Looking at Figure 2A, the magnetic field is highly concentrated (up to 166.930 mTesla) in the center and some edges, while other areas exhibit very weak magnetic fields, resulting in a highly uneven distribution. This suggests a high probability of hotspots.

[0123] In contrast, Figure 2B confirms that the magnetic field is distributed much more uniformly across the entire magnetic material in a wave-like pattern, without excessive concentration at specific points. The maximum magnetic field value is also lower at 139.035 mTesla compared to the comparative example, indicating that localized concentration has been suppressed.

[0124] These visual differences become clearer when we compare the quantitative data below.

[0125] Phase-by-phase Mean [mTesla] Phase-by-phase Std [mTesla] Phase-by-phase CV [%] Comparative Example 26.47616.15161.002 Example 151.58221.02540.759

[0126] Looking at the phase-by-phase coefficient of variation (CV) indicating the uniformity of the magnetic field distribution in the table above, it can be confirmed that the comparative example has a value of 61.002%, while the example 1 has a value of 40.759%, which is significantly lower. Therefore, it can be visually and quantitatively proven that applying a 90-degree phase difference control as in the example 1 of the present invention is very effective in suppressing the occurrence of hot spots and increasing thermal stability by making the magnetic field distribution much more uniform than the comparative example.

[0127]

[0128] Example 2: Three-layer coil device with spatial orthogonality

[0129]

[0130] Fig. 3 is a perspective view showing a transmitter and a receiver of a wireless power transmission device according to another embodiment of the present invention. Referring to Fig. 3, the wireless power transmission device of the present embodiment includes a wireless power transmission device (100) and a wireless power reception device (200), similar to that of Example 1.

[0131] The coil section of the second embodiment is characterized by being composed of one circular coil and two DD coils that are orthogonal to each other. Specifically, in addition to the structure in which the two DD coils that are arranged orthogonally to each other as in the first embodiment are overlapped, a circular coil that wraps around these DD coils is additionally arranged. These three coils (circular, DD1, DD2) are arranged so as not to have a large influence on each other's magnetic fields, thereby securing spatial orthogonality. This multi-coil structure enables more stable power transmission in response to various alignment conditions and coupling coefficient changes. In the case of a wireless power transmission device, a magnetic material for forming a magnetic field path is similarly arranged at the bottom of the coil section.

[0132]

[0133] (1) In case of no phase control (comparative example)

[0134] First, let us examine a comparative example in which the relative phase difference of the current applied to the three coils (circular, DD1, DD2) is all set to 0 degrees.

[0135] In this case, the magnetic field distribution formed in the magnetic material exhibits a relatively non-uniform shape, and the maximum magnetic field value is measured as 34.964 mTesla. The quantitative characteristics of this magnetic field distribution are shown in the table below.

[0136] Unit of distinction: Total phase Mean: 26.880 mTesla Total phase Std: 4.997 mTesla Coefficient of variation: 18.588%

[0137] As can be seen in the table above, the coefficient of variation in the case without phase control is calculated to be 18.588%, indicating that the magnetic field distribution is somewhat non-uniform.

[0138] (2) When there is optimal phase control (embodiment of the present invention)

[0139] Next, we will examine a case in which the relative phase difference of the current applied to three coils is controlled to 0 degrees for the circular coil, 45 degrees for the DD1 coil, and 135 degrees for the DD2 coil, respectively, according to the present invention.

[0140] By providing optimal differences between the three phases, the magnetic field saturation formed in the magnetic material is distributed much more evenly than in the previous comparative example. The quantitative analysis results for this effect are shown in the table below.

[0141] Unit of distinction: Total phase Mean: 26.604 mTesla Total phase Std: 3.210 mTesla Coefficient of variation: 12.067%

[0142] Comparing the table above with the results of the comparative example, it can be seen that the coefficient of variation has been significantly reduced from 18.588% to 12.067%. This indicates that the uniformity of the magnetic field distribution has been significantly improved through the phase control technology of the present invention.

[0143] (3) Effect

[0144] This example demonstrates that optimally controlling the phase difference between each coil can effectively equalize power density and suppress localized heating of the magnetic material, not only in a two-layer structure but also in a complex three-layer structure. This is a significant advantage of the present invention, enabling the device to handle higher power capacities while maintaining thermal stability.

[0145] FIG. 4A is a diagram showing the distribution of a magnetic field formed in a magnetic body at a specific point in time (phase 30 degrees) in a comparative example (all coil phase differences 0 degrees) for Example 2 of the present invention. FIG. 4B is a diagram showing the distribution of a magnetic field formed in a magnetic body at the same point in time in Example 2 of the present invention (circular 0°, DD1 45°, DD2 135° phase differences).

[0146] In Figure 4A, the magnetic field is visually concentrated very strongly in certain areas, while it is very weak in other areas, demonstrating significant non-uniformity in distribution. In contrast, Figure 4B, which applies optimal phase control, clearly shows that the magnetic field is not concentrated in a specific point, but is distributed much more evenly across the entire magnetic material surface than before.

[0147] These distribution differences are also evidenced by the quantitative data below.

[0148] Phase-by-phase Mean [mTesla] Phase-by-phase Std [mTesla] Phase-by-phase CV [%] Comparative Example 10.6205.93755.905 Example 113.5714.63834.177

[0149] Looking at the coefficient of variation (CV) by phase, which indicates the uniformity of the magnetic field distribution in the table above, the comparative example had 55.905%, while Example 2 showed a significant decrease to 34.177%. This clearly demonstrates that the phase control method of the present invention effectively uniformly distributes the magnetic field even in a complex three-layer coil structure, thereby reducing the possibility of hot spots and ensuring thermal stability.

[0150] (4) Miniaturization effect through structural arrangement

[0151] In addition, this embodiment 2 demonstrates the advantage of miniaturization through structural arrangement of the coil, in addition to the phase control effect described above.

[0152] Typically, when three coils are used as in this embodiment, the coils are sequentially stacked in separate layers to form a three-layer thickness. However, in this embodiment, the inner diameter of the circular coil is designed to be large enough to accommodate two bundles of DD coils within it.

[0153] This allows the circular coil to be placed together on the same plane, outside the two-layer stacked structure of two DD coils. As a result, while using three coils, the total number of coil layers is limited to two, achieving a miniaturization effect that directly reduces the overall thickness of the device.

[0154]

[0155] Example 3: Hybrid phase control coil device

[0156]

[0157] Fig. 5 is a plan view showing the structure of a coil unit according to another embodiment of the present invention. Referring to Fig. 5, the coil unit of the present embodiment is composed of one circular coil (110) and three DD coils arranged at an angle of 120 degrees to each other. The three DD coils each include a first DD coil (121, 122), a second DD coil (131, 132), and a third DD coil (141, 142).

[0158] The structural feature of this embodiment lies in the two-layer planar arrangement. On the first plane (upper layer), a circular coil (110) and a portion corresponding to half of each DD coil (121, 131, 141) are arranged together. On the second plane (lower layer), the remaining half portions of the DD coil (122, 132, 142) are arranged, thereby forming a coil portion having an overall thickness of two layers.

[0159] This embodiment is characterized by being a hybrid method that utilizes both of the heat reduction methods described above.

[0160] * Relationship between DD coils: The three DD coils are spaced 120 degrees apart from each other and are not spatially orthogonal. Therefore, in-phase control is applied between them. That is, by applying the same phase current to the three DD coils, the total current is divided into 1 / 3, thereby reducing the resistive loss (copper loss) of the coils themselves.

[0161] * Relationship between the circular coil and the DD coil group: There is spatial orthogonality between the combined magnetic field formed by the circular coil (110) and the three DD coils. Therefore, phase difference control is applied between them to uniformly distribute the magnetic field formed in the magnetic body, thereby suppressing hot spots.

[0162] In this way, the present embodiment optimizes heat generation by comprehensively applying in-phase control and phase difference control according to the arrangement relationship of the coils.

[0163]

[0164] Example 4: Performance improvement and weight reduction through optimal magnetic structure

[0165]

[0166] This embodiment relates to a method for improving the performance of a wireless power transmission device and achieving weight reduction and cost reduction by optimizing the shape and material of a magnetic body.

[0167]

[0168] (1) Performance stabilization through magnetic material shape optimization

[0169] When the transmitter and receiver are misaligned during wireless power transmission, the mutual inductance (M) value fluctuates, making stable power control difficult. The present invention minimizes this fluctuation rate by placing a magnetic block of a specific shape protruding into the empty three-dimensional space surrounding the coil and optimizing its shape, size, and position.

[0170] Figures 6A, 6B, and 6C illustrate this optimization process. Each figure shows the variation in mutual inductance when magnetic blocks of different shapes and sizes are applied.

[0171] * Figure 6A shows the case where the fluctuation rate was highest at 34.57% in a specific structure.

[0172] * Figure 6B shows the case where the size of the magnetic protrusion is maximized, and the fluctuation rate is 33.91%.

[0173] * Figure 6C shows an optimal case in which the mutual inductance variation rate is successfully reduced to 27.64% by optimizing the shape and arrangement of the magnetic blocks.

[0174] By optimizing the shape of the magnetic material in this way and suppressing fluctuations in the mutual inductance value, stable power transmission is possible even under various alignment conditions, thereby improving the performance and reliability of the device.

[0175]

[0176] (2) Lightweighting and cost reduction through hybrid magnetic materials

[0177] Furthermore, this embodiment can utilize a hybrid magnetic structure that utilizes different types of magnetic materials to reduce the weight and cost of the magnetic material. This structure involves layering and stacking high-performance magnetic materials with high permeability and cost, and low-permeability but lightweight and inexpensive magnetic materials. For example, high-performance magnetic materials can be used extensively in core areas where the magnetic field is concentrated, while lightweight or inexpensive materials can be used extensively in other areas to achieve an overall balance.

[0178] This hybrid magnetic structure is an effective way to simultaneously achieve lightweighting and cost reduction of the device by reducing the total amount of magnetic material used while minimizing performance degradation.

[0179]

[0180] Application to receiving devices

[0181]

[0182] Meanwhile, the above description has been mainly focused on the wireless power transmission device (100) for convenience of explanation, but all technical principles proposed in the present invention can be applied equally or symmetrically to the wireless power reception device (200).

[0183] Specifically, in the case of the 'heat reduction through phase control' technology, when a current is induced in multiple coils of the receiving device (200) by the magnetic field of the transmitting unit, the phase relationship between the currents induced in each coil has the same effect on the magnetic field distribution of the receiving unit magnetic body. Therefore, if the phase control principle of the present invention is applied, hot spots of the receiving unit magnetic body can also be effectively suppressed. In addition, if the receiving coil itself is designed as a non-orthogonal multi-path structure to which 'phase control' is applied, the resistance loss (copper loss) occurring in the receiving device can be reduced, thereby increasing power reception efficiency and reducing heat generation.

[0184] Likewise, "structural optimization" technology is also crucial for receivers (200). Because receivers mounted on vehicles, for example, face greater constraints on thickness and weight, miniaturization techniques through "planar coil arrangement" are particularly useful for receivers. Furthermore, forming "optimally shaped" protrusions on the receiver magnetic body or using "hybrid magnetic bodies" directly contribute to the performance stabilization, weight reduction, and cost reduction of the receiver device.

[0185] In fact, all drawings presented in this specification, such as FIG. 1, FIG. 3, and FIG. 6, show that the transmitting device (100) and the receiving device (200) can have structures that are symmetrical or similar to each other, which clearly supports that all technical ideas of the present invention can be applied to both sides.

[0186] Therefore, the present invention is not limited to a technology for transmitting devices, but provides a comprehensive solution for optimizing the entire wireless power transmission system including a transmitting unit and a receiving unit.

[0187]

[0188] The above-described embodiments are merely illustrative of the technical idea of ​​the present invention, and the present invention is not limited thereto. For example, in addition to the two DD coil structures described in Example 1, even in a structure in which one circular coil and one DD coil are arranged to be spatially orthogonal to each other, the same heat generation reduction effect can be obtained by applying currents with a 90-degree phase difference to the two coils. Therefore, the above-described detailed description should not be construed as limiting in any way, but should be considered as illustrative. The scope of the present invention should be determined by a reasonable interpretation of the appended claims, and all changes within the equivalent scope of the present invention are included in the scope of the present invention.

Claims

1. A method for optimizing the heat generation characteristics of a wireless power transmission device including a plurality of coils and a magnetic body arranged to have a predetermined spatial relationship, A step of controlling the relative phase difference of currents applied to each coil forming the plurality of coils based on the above spatial relationship. A method for optimizing the heat generation characteristics of a wireless power transmission device including a .

2. In claim 1, The above plurality of coils are arranged to be spatially orthogonal to each other. A method for optimizing the heat generation characteristics of a wireless power transmission device characterized by:

3. In claim 2, When the above plurality of coils are composed of two coils, the relative phase difference is controlled by 90 degrees. A method for optimizing the heat generation characteristics of a wireless power transmission device characterized by:

4. In claim 3, The above two coils are DD coils that are orthogonal to each other. A method for optimizing the heat generation characteristics of a wireless power transmission device characterized by:

5. In claim 2, When the above plurality of coils are composed of three coils, the relative phase difference is controlled to 0 degrees, 45 degrees, and 135 degrees, respectively. A method for optimizing the heat generation characteristics of a wireless power transmission device characterized by:

6. In claim 5, The above three coils are one circular coil and two DD coils. A method for optimizing the heat generation characteristics of a wireless power transmission device characterized by:

7. In claim 1, The above plurality of coils are arranged so that they are not spatially orthogonal to each other. A method for optimizing the heat generation characteristics of a wireless power transmission device characterized by:

8. In claim 7, Controlling the relative phase difference of the above plurality of coils to 0 degrees A method for optimizing the heat generation characteristics of a wireless power transmission device characterized by:

9. In claim 8, The above plurality of coils are formed by overlapping N coils of the same shape (N is an integer greater than or equal to 2). A method for optimizing the heat generation characteristics of a wireless power transmission device characterized by:

10. In claim 9, The above N coils are formed by branching each of the sub-bundles into N independent paths in a bundle of Litz wires consisting of a plurality of sub-bundles. A method for optimizing the heat generation characteristics of a wireless power transmission device characterized by:

11. In claim 10, when N is 2, the total heat generation is reduced to half the level of when a bundle of Litz wires is used. A method for optimizing the heat generation characteristics of a wireless power transmission device characterized by:

12. In claim 1, The above plurality of coils are composed of one circular coil and three DD coils arranged at an angle of 120 degrees to each other. A method for optimizing the heat generation characteristics of a wireless power transmission device characterized by:

13. As a wireless power transmission device, A coil section comprising a plurality of coils arranged to have a predetermined spatial relationship; A magnetic material placed on one side of the above coil section; A control unit that controls the relative phase difference of currents applied to each coil of the plurality of coils to optimize the heating characteristics of the device. A wireless power transmission device comprising:

14. In claim 13, The above coil portion includes a circular coil having an inner diameter capable of containing another coil therein, thereby reducing the increase in the overall thickness of the coil portion. A wireless power transmission device characterized by:

15. In claim 13, The above magnetic material includes a portion protruding into the empty space of the coil section to minimize the amount of change in the mutual inductance value. A wireless power transmission device characterized by:

16. In claim 13, The above magnetic material is a hybrid magnetic material that is made by stacking different types of magnetic materials. A wireless power transmission device characterized by:

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