A magnetic core structure and transformer for a three-phase interleaved LLC resonant converter

Abstract

This application discloses a magnetic core structure and transformer for a three-phase interleaved LLC resonant converter. The magnetic core structure includes a first magnetic yoke, a second magnetic yoke, and a magnetic column assembly disposed between the first and second magnetic yokes. The magnetic column assembly includes three main magnetic columns and one central magnetic column. The three main magnetic columns are arranged in an equilateral triangle, and the central magnetic column is located at the center of the three main magnetic columns. The three main magnetic columns are used to wind the windings, and the central magnetic column cooperates with the first magnetic yoke, the second magnetic yoke, and the three main magnetic columns to form a low reluctance magnetic circuit for the zero-sequence flux and the third harmonic flux. The cross-sectional area of ​​the central magnetic column is 1 / 3 to 1 / 2 of the cross-sectional area of ​​a single main magnetic column. This application enables the central magnetic column to cooperate with the three main magnetic columns to form a low reluctance magnetic circuit for the zero-sequence flux and the third harmonic flux, without inducing additional zero-sequence electromotive force in the windings, thus actively protecting the symmetry of the three-phase fundamental flux.

Description

Technical Field

[0001] This application relates to the field of power transformer technology, specifically to a magnetic core structure and transformer for a three-phase interleaved LLC resonant converter. Background Technology

[0002] Three-phase interleaved LLC resonant converters are widely used in high-power energy storage, industrial power supplies, and on-board chargers due to their advantages of high efficiency, high power density, and low output ripple. Among these, the transformer, as the core magnetic component of the three-phase interleaved LLC resonant converter, directly affects the overall efficiency, electromagnetic compatibility, and reliability of the device. A commonly used core structure in existing three-phase interleaved LLC resonant converters is an equilateral triangular three-pillar core, where the three main magnetic pillars are arranged in an equilateral triangle, connected at both ends by a yoke, and the central region of the triangle is hollowed out (for example, Chinese patents CN114613583A and CN1328690A disclose such core structure schemes). This type of structure exhibits good fundamental flux symmetry under ideal symmetrical operating conditions. However, in actual mass production and full-condition operation, it suffers from problems such as zero-sequence flux and third harmonic flux. Zero-sequence flux induces additional zero-sequence electromotive force in the three-phase windings, disrupting the symmetry of the three-phase winding terminal voltages, further exacerbating the three-phase current imbalance, and even posing a risk of local core saturation. This makes it unsuitable for full-condition operation under load fluctuations, light loads, and parameter tolerances. Consequently, while this type of three-phase interleaved LLC resonant converter performs well in project simulations, it fails to meet the requirements in actual prototype testing. Summary of the Invention

[0003] This application aims to address one of the technical problems in related technologies to a certain extent. To this end, this application provides a magnetic core structure and transformer for a three-phase interleaved LLC resonant converter.

[0004] To achieve the above objectives, this application adopts the following technical solution: a magnetic core structure for a three-phase interleaved LLC resonant converter, the magnetic core structure comprising a first magnetic yoke, a second magnetic yoke arranged parallel to and spaced apart from the first magnetic yoke, and a magnetic column assembly disposed between the first magnetic yoke and the second magnetic yoke;

[0005] The magnetic column assembly includes three main magnetic columns and one central magnetic column. The three main magnetic columns are arranged in an equilateral triangle. The central magnetic column is located at the center of the three main magnetic columns. The three main magnetic columns are used to wind the windings. The central magnetic column is used to cooperate with the first magnetic yoke, the second magnetic yoke and the three main magnetic columns to form a low magnetic reluctance magnetic circuit for the closure of zero-sequence magnetic flux and third harmonic magnetic flux.

[0006] The cross-sectional area of ​​the central magnetic column is 1 / 3 to 1 / 2 of the cross-sectional area of ​​a single main magnetic column.

[0007] The application of this application has the following beneficial effects: Manufacturing tolerances of 1% to 5% in mass-produced components can lead to asymmetry in three-phase parameters; in a star connection, the third harmonic current cannot flow for excitation, resulting in harmonic flux; asymmetry in the characteristics of LLC switching transistors leads to DC bias; and harmonic distortion is amplified in light-load discontinuous mode. All four of these situations can lead to zero-sequence flux and third harmonic flux. Based on the above analysis, a low-resistivity closed loop is set up for the zero-sequence flux and third harmonic flux, fundamentally solving the loss and current sharing problems caused by the zero-sequence flux and third harmonic flux. Specifically, a central magnetic column is set at the center of the three main magnetic columns. The central magnetic column is not wound, and by limiting the cross-sectional area of ​​the central magnetic column relative to the main magnetic columns, the central magnetic column can cooperate with the three main magnetic columns to form a low-resistivity magnetic circuit for the zero-sequence flux and third harmonic flux to close. Therefore, under the aforementioned asymmetrical operating conditions, a low magnetic reluctance magnetic circuit can be formed by the first magnetic yoke, the central magnetic column, the second magnetic yoke, and the three main magnetic columns, which will not induce additional zero-sequence electromotive force in the winding and actively protect the symmetry of the three-phase fundamental magnetic flux.

[0008] Meanwhile, limiting the cross-sectional area of ​​the central magnetic column to 1 / 3 to 1 / 2 of the cross-sectional area of ​​a single main magnetic column can cover the magnetic flux requirements under extreme working conditions without encroaching on the winding window, increasing the volume and cost, and eliminating the need for significant adjustments to the original magnetic core structure, winding process and production equipment, thus ensuring extremely low mass production modification costs.

[0009] Optionally, the cross-sectional area of ​​the central magnetic column is 0.4 times the cross-sectional area of ​​a single main magnetic column.

[0010] Optionally, both the first and second magnetic yokes are plates with a set thickness, and the two ends of the main magnetic post are respectively fixed to the first and second magnetic yokes, and the end faces of the two ends of the main magnetic post are respectively flush with the outer surfaces of the first and second magnetic yokes.

[0011] The set thickness dimension is configured such that the contact area between the first magnetic yoke and the main magnetic post, and the contact area between the second magnetic yoke and the main magnetic post, are both not less than the cross-sectional area of ​​a single main magnetic post.

[0012] Optionally, the cross-sections of the first magnetic yoke and the second magnetic yoke are both triangular shapes with rounded notches at three corners. The three corners of the first magnetic yoke and the three corners of the second magnetic yoke respectively form first arc-shaped grooves for fixing to the end sides of the three main magnetic pillars. The inner wall of the first arc-shaped groove is larger than the cross-sectional area of ​​a single main magnetic pillar.

[0013] Optionally, the main magnetic column is an integral structure, and the two ends of the main magnetic column are respectively bonded and fixed to the first magnetic yoke and the second magnetic yoke.

[0014] Optionally, the main magnetic column includes a first half-magnetic column and a second half-magnetic column, the first half-magnetic column is fixed to a first magnetic yoke, and the second half-magnetic column is fixed to a second magnetic yoke; the first half-magnetic column and the second half-magnetic column are bonded and fixed, or there is an air gap between the first half-magnetic column and the second half-magnetic column.

[0015] Optionally, the first half-magnetic column is bonded and fixed to the first magnetic yoke, or the two are formed into an integral structure, and the second half-magnetic column is bonded and fixed to the second magnetic yoke, or the two are formed into an integral structure.

[0016] Optionally, the cross-section of the central magnetic column is a circle with three arc notches, and the central magnetic column forms three second arc grooves, with the three second arc grooves respectively opposite to the three main magnetic columns.

[0017] Optionally, the central magnetic column includes a first half-column and a second half-column, the first half-column being fixed to a first magnetic yoke, the second half-column being fixed to a second magnetic yoke, and the first half-column and the second half-column being bonded and fixed together.

[0018] Alternatively, the central magnetic column is an integral structure, and both ends of the central magnetic column are respectively bonded and fixed to the first magnetic yoke and the second magnetic yoke.

[0019] Optionally, the first semi-cylinder is bonded and fixed to the first magnetic yoke, or the two are formed into an integral structure, and the second semi-cylinder is bonded and fixed to the second magnetic yoke, or the two are formed into an integral structure.

[0020] In addition, this application also provides a transformer for a three-phase interleaved LLC resonant converter, the transformer including a magnetic core structure as described in any of the above technical solutions, the transformer also including windings, and the three main magnetic columns are respectively wound with the windings.

[0021] The reasoning process for the beneficial effects of the transformer provided in this application are similar to that of the aforementioned magnetic core structure, and will not be repeated here.

[0022] These features and advantages of this application will be disclosed in detail in the following specific embodiments and accompanying drawings. Preferred embodiments or means of this application will be illustrated in detail with reference to the accompanying drawings, but are not intended to limit the technical solutions of this application. Furthermore, each of these features, elements, and components appearing in the following text and drawings is a plurality, and different symbols or numbers are used for convenience of representation, but all represent components with the same or similar structure or function. Attached Figure Description

[0023] The following description, in conjunction with the accompanying drawings, further illustrates this application:

[0024] Figure 1This application provides a schematic diagram of the core structure for a three-phase interleaved LLC resonant converter.

[0025] Figure 2 This is a side view of the magnetic core structure;

[0026] Figure 3 This is an exploded view of the magnetic core structure;

[0027] Figure 4 This is a schematic diagram of the magnetic core structure before the first magnetic yoke is integrated with the main magnetic column.

[0028] Figure 5 This is a cross-sectional view of the magnetic core structure;

[0029] Figure 6 This is a schematic diagram of a transformer that uses the magnetic core structure provided in this embodiment.

[0030] Among them, 1. First magnetic yoke; 10. First arc-shaped slot; 2. Second magnetic yoke; 3. Main magnetic column; 30. Air gap; 31. First half magnetic column; 32. Second half magnetic column; 4. Central magnetic column; 40. Second arc-shaped slot; 41. First half column; 42. Second half column; 5. Winding. Detailed Implementation

[0031] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described are intended to explain this application and should not be construed as limiting it.

[0032] The terms "an embodiment," "example," or "example" used in this specification refer to a particular feature, structure, or characteristic described in connection with the embodiment itself that may be included in at least one embodiment disclosed in this application. The phrase "in an embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment.

[0033] In the description of this application, it should be understood that the terms "upper," "lower," "front," "rear," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. In the description of this application, "a plurality of" means two or more, unless otherwise precisely specified.

[0034] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "connected," "linked," and "connected" should be interpreted broadly. For example, they can refer to a fixed connection, a connection through an intermediary, the internal connection of two elements, or the interaction between two elements. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0035] Manufacturing tolerances of 1% to 5% in mass-produced components can lead to asymmetry in three-phase parameters. In a star connection, the third harmonic current cannot flow for excitation, resulting in harmonic flux. Asymmetry in the characteristics of LLC switching transistors causes DC bias. In light-load discontinuous mode, harmonic distortion is amplified. All four of these situations result in zero-sequence flux and third harmonic flux. Therefore, from the perspective of manufacturing and assembly tolerances, the generation of zero-sequence flux and third harmonic flux is unavoidable in actual operating conditions. Based on the above analysis, a low-resistivity closed loop is designed to address the losses and current sharing problems caused by zero-sequence flux and third harmonic flux at their root.

[0036] This embodiment provides a magnetic core structure for a three-phase interleaved LLC resonant converter, such as... Figure 1 As shown, the magnetic core structure includes a first yoke 1, a second yoke 2, and a magnetic column assembly disposed between the first yoke 1 and the second yoke 2. The second yoke 2 is arranged parallel to and spaced apart from the first yoke 1, together forming a horizontal closed frame of the magnetic circuit. The magnetic column assembly includes three main magnetic columns 3 and one central magnetic column 4. The three main magnetic columns 3 are arranged in the space between the first yoke 1 and the second yoke 2 along a direction perpendicular to the first yoke 1 and the second yoke 2, serving as channels for the vertical flow of magnetic flux in the magnetic circuit.

[0037] In this embodiment, the three main magnetic columns 3 are arranged in an equilateral triangle. This is the basis for ensuring consistent fundamental magnetic circuit length, symmetrical mutual inductance, and optimal utilization of the winding window in the three-phase interleaved parallel topology. Combined with... Figure 6 As shown, in this embodiment, the three main magnetic columns 3 are used to wind the winding 5, and the three main magnetic columns 3 correspond to the A, B, and C phases of the transformer, respectively. The center magnetic column 4 is located at the center of the three main magnetic columns 3. Here, "center magnetic column 4 is located at the center of the three main magnetic columns 3" means that the central axis of the center magnetic column 4 coincides with the center line of the equilateral triangle formed by the three main magnetic columns 3. The center magnetic column 4 is used to cooperate with the first magnetic yoke 1, the second magnetic yoke 2, and the three main magnetic columns 3 to form a low reluctance magnetic circuit that allows for the closure of zero-sequence magnetic flux and third harmonic magnetic flux, and the cross-sectional area of ​​the center magnetic column 4 is 1 / 3 to 1 / 2 of the cross-sectional area of ​​a single main magnetic column 3. It should be emphasized that in this embodiment, no windings or coils are wound outside the center magnetic column 4.

[0038] The magnetic core structure provided in this embodiment features a central magnetic post 4 positioned at the center of the three main magnetic posts 3. This central magnetic post 4 is not wound with any coils. By defining the cross-sectional area of ​​the central magnetic post 4 relative to the main magnetic posts 3, it is possible for the central magnetic post 4 to cooperate with the three main magnetic posts 3 to form a low-resistivity magnetic circuit that allows for the closure of zero-sequence and third harmonic magnetic fluxes. Therefore, under the aforementioned asymmetrical operating conditions, a low-resistivity magnetic circuit can be formed through the first yoke 1, the central magnetic post 4, the second yoke 2, and the three main magnetic posts 3, preventing the induction of additional zero-sequence electromotive force in the winding 5 and actively protecting the symmetry of the three-phase fundamental magnetic flux.

[0039] Combination Figure 5 As shown, the relationship between the cross-sectional area Ac of the central magnetic column 4 and the cross-sectional area Ap of the single main magnetic column 3 is one of the core design parameters of this scheme. Through magnetic circuit theory derivation and finite element simulation verification, in this embodiment, Ac is limited to 1 / 3 to 1 / 2 of Ap. The specific design rationale is explained as follows: The formula for the magnetic circuit is... (Φ is magnetic flux, B is magnetic flux density, and A is the cross-sectional area of ​​the magnetic core). Let the cross-sectional area of ​​a single main magnetic column 3 be Ap. In actual operation, the zero-sequence magnetic flux (including third harmonic flux) generated by three-phase parameter asymmetry, DC bias, or harmonic excitation manifests as in-phase magnetic flux components in the main magnetic column 3. Let the amplitude of the zero-sequence magnetic flux density flowing through a single main magnetic column 3 be B0. Therefore, the zero-sequence magnetic flux in a single main magnetic column 3 is:

[0040] ;

[0041] Since the zero-sequence magnetic fluxes of the three phases are in phase, after converging in the first yoke 1, they will all seek to return to the second yoke 2 through the central magnetic column 4 (because the central magnetic column 4 is the only path without reverse magnetomotive force resistance). Therefore, the total zero-sequence magnetic flux Φc that the central magnetic column 4 needs to carry is the sum of the zero-sequence magnetic fluxes of the three main magnetic columns 3:

[0042] ;

[0043] Let the cross-sectional area of ​​the central magnetic column 4 be Ac, then the working magnetic flux density Bc inside the central magnetic column 4 can be calculated by the following formula:

[0044] ;

[0045] The constraints are set as follows: In typical high-frequency LLC converter applications, to control core losses within an acceptable range and ensure sufficient anti-saturation margin, the fundamental operating flux density amplitude Bm of the main magnetic column 3 under rated operating conditions is typically designed to be between 0.2T and 0.3T (depending on the grade of the selected manganese-zinc ferrite material and the switching frequency). Under non-ideal operating conditions such as conventional parameter tolerances and light-load intermittent operation, the extreme maximum value of the zero-sequence flux density amplitude B0 usually does not exceed one-third of the fundamental flux density Bm. This is a conservative boundary derived from extensive engineering practice and simulation statistics. To ensure that the central magnetic column 4 can effectively perform its low-resistance bypass function under any operating condition, it must not undergo magnetic saturation. Once the central magnetic column 4 saturates, its permeability will drop sharply to near the level of air, and the low-resistance path will fail. Therefore, it is necessary to ensure that the maximum value of the operating flux density Bc of the central magnetic column 4 does not exceed the rated operating flux density limit Bm of the main magnetic column 3, i.e., Bc ≤ Bm.

[0046] Substituting the constraints into the aforementioned formula, we can derive that Ac ≥ Ap / 3, meaning the cross-sectional area of ​​the central magnetic column 4 is not less than one-third of the cross-sectional area of ​​a single main magnetic column 3. This is the minimum safe cross-sectional area of ​​the central magnetic column 4. Furthermore, the upper limit of Ac is taken as Ap / 2, meaning the cross-sectional area of ​​the central magnetic column 4 is not greater than half the cross-sectional area of ​​a single main magnetic column 3. This approach covers the flux requirements under extreme operating conditions without encroaching on the winding window, increasing volume or cost, or requiring significant adjustments to the original core structure, winding process, and production equipment, ensuring extremely low mass production modification costs.

[0047] Through parametric scanning using 3D electromagnetic simulation software such as Ansys Maxwell and comprehensive verification through actual prototype testing, it was found that within the range of Ac being 1 / 3 to 1 / 2 of Ap, the central magnetic column 4 can remain unsaturated under various conventional asymmetrical operating conditions and effectively conduct zero-sequence magnetic flux. Specifically, selecting Ac as 0.4 times Ap, i.e., the cross-sectional area of ​​the central magnetic column 4 being 0.4 times the cross-sectional area of ​​a single main magnetic column 3, has been proven to be the optimal engineering solution balancing magnetic performance (anti-saturation capability), material cost, central region space utilization, and mass production feasibility. If Ac is less than Ap / 3, there is a risk of central column saturation under extreme unbalanced operating conditions (such as phase loss or severe magnetic bias); if Ac is greater than Ap / 2, it will significantly encroach on the space of the central region of the equilateral triangle, potentially necessitating a reduction in the diameter of the main magnetic column 3 or compression of the winding window 5, thereby sacrificing the overall power density of the unit.

[0048] Combination Figure 2 and Figure 4As shown, in this embodiment, both the first magnetic yoke 1 and the second magnetic yoke 2 are plates with a predetermined thickness. The two ends of the main magnetic post 3 are fixed to the first magnetic yoke 1 and the second magnetic yoke 2, respectively, and the end faces of the two ends of the main magnetic post 3 are flush with the outer surfaces of the first magnetic yoke 1 and the second magnetic yoke 2, respectively. This structural design improves the mechanical strength of the connection between the main magnetic post 3 and the first magnetic yoke 1 and the second magnetic yoke 2, and optimizes the magnetic circuit.

[0049] To prevent a magnetic flux "bottleneck" effect at the connection interfaces between the first yoke 1 and the second yoke 2 and the main magnetic column 3, this embodiment limits the thickness of the yokes. Specifically, the thickness in this embodiment is configured such that the contact area between the first yoke 1 and the main magnetic column 3, and the contact area between the second yoke 2 and the main magnetic column 3, are both not less than the cross-sectional area of ​​a single main magnetic column 3. This constraint ensures that when the fundamental magnetic flux flows from the main magnetic column 3 into the first yoke 1 and the second yoke 2, the effective magnetic cross-section does not shrink, thereby avoiding local core saturation and additional eddy current losses caused by excessively high local magnetic flux density.

[0050] Furthermore, in combination Figure 4 and Figure 5 As shown, in order to minimize the volume and weight of the first magnetic yoke 1 and the second magnetic yoke 2 while meeting the above-mentioned contact area requirements and to improve power density, the structural shapes of the first magnetic yoke 1 and the second magnetic yoke 2 are specially designed in this embodiment. In this embodiment, the cross-sections of the first magnetic yoke 1 and the second magnetic yoke 2 are both triangular shapes with rounded notches at three corners. The three corners of the first magnetic yoke 1 and the three corners of the second magnetic yoke 2 respectively form first arc-shaped grooves 10 for fixing to the end sides of the three main magnetic pillars 3. The inner wall surface of the first arc-shaped groove 10 is larger than the cross-sectional area of ​​a single main magnetic pillar 3. That is, Figure 4 The inner wall of the first arc-shaped groove 10 shown on the first magnetic yoke 1 is the "contact area between the first magnetic yoke 1 and the main magnetic column 3" mentioned above. The inner wall of the first arc-shaped groove 10 is larger than the cross-sectional area of ​​a single main magnetic column 3, and the "contact area between the first magnetic yoke 1 and the main magnetic column 3 is not less than the cross-sectional area of ​​a single main magnetic column 3" mentioned above.

[0051] Combination Figure 1 and Figure 3As shown, in this embodiment, the main magnetic post 3 includes a first half-magnetic post 31 and a second half-magnetic post 32. The first half-magnetic post 31 is fixed to the first magnetic yoke 1, and the second half-magnetic post 32 is fixed to the second magnetic yoke 2. An air gap 30 exists between the first half-magnetic post 31 and the second half-magnetic post 32. Simultaneously, the central magnetic post 4 includes a first half-pillar 41 and a second half-pillar 42. The first half-pillar 41 is fixed to the first magnetic yoke 1, and the second half-pillar 42 is fixed to the second magnetic yoke 2. Furthermore, the first half-pillar 41 and the second half-pillar 42 are bonded together. That is, both the first half-pillar 41 and the first half-magnetic post 31 are fixed to the first magnetic yoke 1, and both the second half-pillar 42 and the second half-magnetic post 32 are fixed to the second magnetic yoke 2. During assembly, the three first half-magnetic posts 31 and the second half-magnetic post 32 are aligned, the first half-pillar 41 and the second half-pillar 42 are aligned, and then adhesive is used to bond and fix the first half-pillar 41 and the second half-pillar 42 together. The size design ensures that an air gap 30 is formed between the first half-magnetic post 31 and the second half-magnetic post 32.

[0052] In LLC resonant converters, the magnetizing inductance Lm of the transformer is a key parameter determining the gain characteristics of the resonant network and the range of soft-switching implementation. By introducing an air gap 30 into the magnetic circuit, the magnetic reluctance of the magnetic circuit can be significantly increased, thereby precisely reducing and controlling the value of the magnetizing inductance. In this embodiment, the main magnetic column 3 is designed as a split unit, and a tiny air gap 30 can be formed between the two by designing the dimensions of the first half-magnetic column 31 and the second half-magnetic column 32.

[0053] Alternatively, in an optional embodiment, when the first half-magnetic post 31 and the second half-magnetic post 32 are joined, the same effect of setting an air gap 30 can be achieved by inserting a non-magnetic gasket (e.g., FR-4 epoxy glass cloth laminate sheet) of a specific thickness between their joint surfaces. Therefore, in an optional embodiment, the first half-magnetic post 31 and the second half-magnetic post 32 can also be bonded and fixed together.

[0054] In other alternative embodiments, the air gap 30 may not be provided. In this embodiment, the main magnetic column 3 is an integral structure, and the two ends of the main magnetic column 3 are respectively bonded and fixed to the first magnetic yoke 1 and the second magnetic yoke 2.

[0055] In this embodiment, the first half-magnetic pillar 31 is bonded and fixed to the first magnetic yoke 1, and the second half-magnetic pillar 32 is bonded and fixed to the second magnetic yoke 2. Alternatively, in other optional embodiments, the first half-magnetic pillar 31 and the first magnetic yoke 1 are bonded to form an integral structure, and the second half-magnetic pillar 32 and the second magnetic yoke 2 become an integral structure. In this embodiment, the first magnetic yoke 1 and the three first half-magnetic pillars 31 can be manufactured in one step by ferrite dry pressing and high-temperature sintering processes. During the high-temperature sintering process exceeding 1100°C, the blanks of the first magnetic yoke 1 and the three first half-magnetic pillars 31 undergo solid-phase diffusion at the interface, and the grains grow and fuse to form a completely seamless integral component. This integral sintering method eliminates the micro-gaps and contact magnetic resistance that may exist at the bonding interface, which is particularly advantageous for applications that pursue ultimate high-frequency performance.

[0056] Similarly, in this embodiment, the first semi-cylinder 41 is bonded and fixed to the first magnetic yoke 1 or the two are integrated into a single structure, and the second semi-cylinder 42 is bonded and fixed to the second magnetic yoke 2 or the two are integrated into a single structure.

[0057] Combination Figure 3 and Figure 4 As shown, in this embodiment, the cross-section of the central magnetic post 4 is a circle with three arc-shaped notches. The central magnetic post 4 forms three second arc-shaped grooves 40, and the three second arc-shaped grooves 40 are respectively opposite to the three main magnetic posts 3. Since the three main magnetic posts 3 are distributed in an equilateral triangle, the central region is a space similar to a curved triangle. In order to obtain the maximum effective magnetic conduction area in this limited space, while ensuring sufficient electrical insulation distance between the central magnetic post 4 and the three main magnetic posts 3, the cross-section of the central magnetic post 4 is designed to have three arc-shaped notches (i.e., second arc-shaped grooves 40).

[0058] In an optional embodiment, the central magnetic post 4 can also be designed as an integral structure, and the two ends of the central magnetic post 4 can be bonded and fixed to the first magnetic yoke 1 and the second magnetic yoke 2 respectively.

[0059] like Figure 6 As shown, the magnetic core structure provided in this embodiment can be applied to a transformer, which also includes windings 5, with three main magnetic pillars 3 each wound with a winding 5. Three sets of windings 5 ​​are provided, each correspondingly nested and wound on one of the three main magnetic pillars 3. The windings 5 ​​typically include primary and secondary coils, which can be interleaved (e.g., sandwich winding) to reduce proximity effect losses and leakage inductance at high frequencies. Because the magnetic core structure provided in this embodiment fundamentally solves the problem of zero-sequence flux leakage, transformers using this magnetic core structure exhibit higher efficiency, lower EMI noise, and better thermal stability across the entire operating range.

[0060] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Those skilled in the art will understand that this application includes, but is not limited to, the contents described in the accompanying drawings and the specific embodiments above. Any modifications that do not depart from the functional and structural principles of this application will be included within the scope of the claims.

Claims

1. A magnetic core structure for a three-phase interleaved LLC resonant converter, characterized in that, The magnetic core structure includes a first magnetic yoke, a second magnetic yoke arranged parallel to and spaced apart from the first magnetic yoke, and a magnetic column assembly disposed between the first magnetic yoke and the second magnetic yoke. The magnetic column assembly includes three main magnetic columns and one central magnetic column. The three main magnetic columns are arranged in an equilateral triangle. The central magnetic column is located at the center of the three main magnetic columns. The three main magnetic columns are used to wind the windings. The central magnetic column is used to cooperate with the first magnetic yoke, the second magnetic yoke and the three main magnetic columns to form a low magnetic reluctance magnetic circuit for the closure of zero-sequence magnetic flux and third harmonic magnetic flux. The cross-sectional area of ​​the central magnetic column is 1 / 3 to 1 / 2 of the cross-sectional area of ​​a single main magnetic column; The first and second magnetic yokes are both plates with a set thickness. The two ends of the main magnetic post are respectively fixed to the first and second magnetic yokes, and the end faces of the two ends of the main magnetic post are flush with the outer surfaces of the first and second magnetic yokes, respectively. The set thickness dimension is configured such that the contact area between the first magnetic yoke and the main magnetic column and the contact area between the second magnetic yoke and the main magnetic column are both not less than the cross-sectional area of ​​a single main magnetic column. The cross-sections of the first magnetic yoke and the second magnetic yoke are both triangular shapes with rounded notches at three corners. The three corners of the first magnetic yoke and the three corners of the second magnetic yoke respectively form a first arc-shaped groove for fixing to the end sides of the three main magnetic pillars. The inner wall of the first arc-shaped groove is the contact area between the first magnetic yoke and the main magnetic pillar. The inner wall of the first arc-shaped groove is larger than the cross-sectional area of ​​a single main magnetic pillar.

2. The magnetic core structure for a three-phase interleaved LLC resonant converter as described in claim 1, characterized in that, The cross-sectional area of ​​the central magnetic column is 0.4 times the cross-sectional area of ​​a single main magnetic column.

3. The magnetic core structure for a three-phase interleaved LLC resonant converter as described in claim 1, characterized in that, The main magnetic column is an integral structure, and its two ends are respectively bonded and fixed to the first magnetic yoke and the second magnetic yoke.

4. The magnetic core structure for a three-phase interleaved LLC resonant converter as described in claim 1, characterized in that, The main magnetic column includes a first half-magnetic column and a second half-magnetic column, the first half-magnetic column being fixed to a first magnetic yoke, and the second half-magnetic column being fixed to a second magnetic yoke; The first half-magnetic column and the second half-magnetic column are bonded together, or there is an air gap between the first half-magnetic column and the second half-magnetic column.

5. The magnetic core structure for a three-phase interleaved LLC resonant converter as described in claim 4, characterized in that, The first half-magnetic column is bonded and fixed to the first magnetic yoke, or the two are formed into an integral structure; the second half-magnetic column is bonded and fixed to the second magnetic yoke, or the two are formed into an integral structure.

6. The magnetic core structure for a three-phase interleaved LLC resonant converter as described in claim 1 or 2, characterized in that, The central magnetic column has a circular cross-section with three arc notches, and the central magnetic column forms three second arc grooves, which are respectively opposite to the three main magnetic columns.

7. The magnetic core structure for a three-phase interleaved LLC resonant converter as described in claim 6, characterized in that, The central magnetic column includes a first half-column and a second half-column. The first half-column is fixed to a first magnetic yoke, and the second half-column is fixed to a second magnetic yoke. The first half-column and the second half-column are bonded and fixed together. Alternatively, the central magnetic column is an integral structure, and both ends of the central magnetic column are respectively bonded and fixed to the first magnetic yoke and the second magnetic yoke.

8. The magnetic core structure for a three-phase interleaved LLC resonant converter as described in claim 7, characterized in that, The first semi-cylinder is bonded and fixed to the first magnetic yoke, or the two are formed into a single structure; the second semi-cylinder is bonded and fixed to the second magnetic yoke, or the two are formed into a single structure.

9. A transformer for a three-phase interleaved LLC resonant converter, characterized in that, The transformer includes a magnetic core structure as described in any one of claims 1 to 8, and the transformer further includes windings, with the three main magnetic columns respectively wound with the windings.

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