Fractional-turn current-sharing transformer

Abstract

The invention discloses a fractional-turn current-sharing type transformer, which can simultaneously meet the design requirements of current sharing and gain fine adjustment of parallel windings of a transformer in a high-frequency power converter, magnetic part optimization design and high power density. A primary winding and / or a secondary winding of the transformer comprise / comprises an integer turn winding and at least one fractional turn winding unit, each fractional turn winding unit is split into multiple sections symmetrically or asymmetrically along a center pillar by a turn winding arranged on the same layer, and different fractional turn winding units adopt the same or different split modes. The axial vertical projection of each fractional section in each fractional turn winding unit is completely overlapped or partially overlapped; compared with an existing parallel winding current sharing scheme, a complex structure of a matrix transformer can be avoided, interconnection via holes and corresponding loss required by parallel cross connection of the windings are reduced, and the system efficiency and the power density are further improved by integrating an external circuit comprising a switching device and a direct current filter capacitor, a resonant capacitor and a resonant inductor.

Description

Technical Field

[0001] The present invention belongs to the field of power electronics technology, and is aimed at the field of low-voltage and high-current applications. It specifically relates to a fractional-turn current-sharing transformer, and its integrated design with peripheral circuits. Background Art

[0002] With the rapid development of artificial intelligence technology, the power demand of data centers is increasing day by day. Data center power converters are urgently needed to have higher energy transfer efficiency and higher power density.

[0003] To meet the demands of high-efficiency, high-power-density applications, power converter designs are becoming increasingly high-frequency. In high-frequency power converters, the transformer is a key component that limits the converter's energy transfer efficiency, power density, and heat generation. Currently, transformer winding turns are mostly limited to integer turns, which means the transformer's gain can only be adjusted in integer multiples. However, in a power converter with a commonly used specification, such as 380V input and 12V output, a more precise gain of 15.83 is required. The coarse gain adjustment of an integer-turn transformer also prevents the transformer from operating in an ideal state, making it difficult to optimize the transformer's copper and iron losses.

[0004] Furthermore, data center power supplies feature low voltage and high current, necessitating the design of multiple layers of parallel windings within the transformer to accommodate these high current demands. Due to the proximity effect, the current between parallel windings concentrates in a small number of windings, making it impossible to achieve uniform current distribution across multiple windings. To improve the current sharing characteristics between parallel windings, current research results are generally categorized into the following two approaches:

[0005] Solution 1: Design the relative positions of the primary and secondary windings. (Y. Cai, M. H. Ahmed, Q. Li and F. C. Lee, "Optimized Design of Integrated PCB-Winding Transformer for MHz LLC Converter," IEEE-APEC, 2019, pp. 1452-1458) By winding the primary and secondary windings in the order of "primary-secondary-secondary-primary-primary-...-secondary," an interleaved magnetomotive force is created, improving the consistency of the magnetic field strength at the locations of the parallel windings and optimizing the current sharing characteristics of the parallel windings. However, this requires the parallel windings to be arranged several layers apart, requiring the introduction of a large number of additional through-holes to establish electrical connections between the parallel windings. This results in conduction losses caused by the through-holes being comparable to the conduction losses of the windings, reducing the transformer's energy transfer efficiency.

[0006] Solution 2: Split the transformer and build a matrix transformer. Figure 1As shown, patent CN201910125467.1 splits the transformer into two matrix transformers T1 and T2, and at the same time, by splitting the secondary windings of the matrix transformers T1 and T2, each matrix transformer is split into two units. s11 、N s21 The winding N connected in parallel with the primary p1 、N p2 The structure of "parallel secondary winding" is formed to ensure that the primary winding N of transformers T1 and T2 is p1 、N p2 There is a good current sharing characteristic between them. In addition, through the secondary winding N s11 , Winding N s21 and the primary winding N p1 The structure of "primary series and secondary parallel" is formed to ensure that the secondary windings of transformers T1 and T2 connected in parallel have good current sharing characteristics. However, in order to achieve the excitation inductance L of transformers T1 and T2 m1 、L m2 , the primary winding N of transformer T1 p1 and the primary winding N of transformer T2 p2 The secondary windings of each transformer must be wound on two different magnetic columns. Furthermore, to separate the secondary windings and couple them to different primary windings, each transformer's secondary winding must be wound on two different magnetic columns. As described in Y. Yang, J. Yao, H. Li, and J. Zhao, "A novel current sharing method by grouping transformer's secondary windings for a multiphase LLC resonant converter," IEEE-TPE, 2020, pp. 4877-4890, this approach requires the use of two magnetic cores. Compared to the single core used in traditional transformers, the power density of the transformer is significantly reduced.

[0007] Therefore, it is urgent to design a fractional-turn transformer to meet the design requirements of current sharing of parallel windings of transformers in high-frequency power converters, while meeting the design requirements of transformer gain fine adjustment, loss optimization design and high power density. Summary of the Invention

[0008] The present invention provides a fractional-turn transformer, which can realize automatic current sharing of parallel windings and meet the design requirements of high power density.

[0009] The technical solutions of the present invention are as follows:

[0010] A fractional-turn current-sharing transformer comprises a magnetic core and windings, wherein the magnetic core has a center leg and at least two side legs, and the windings comprise a primary winding and a secondary winding.

[0011] The primary winding and / or secondary winding of the transformer includes an integer-turn winding and at least one fractional-turn winding unit, and all windings are wound along the center column. Each fractional-turn winding unit is symmetrically or asymmetrically divided into multiple segments along the center column from a single-turn winding arranged on the same layer. The number of fractional segments divided into each fractional-turn winding unit is the same or different, and different fractional-turn winding units are distributed in the same or different winding layers. Different fractional-turn winding units are divided in the same or different ways, so that the axial vertical projections of the fractional segments in each fractional-turn winding unit completely or partially overlap.

[0012] The fractional segments of each fractional-turn winding unit are directly connected or connected in series, in parallel, or in a combination of series and parallel to form a k-segment fractional-turn winding, and the axial vertical projections of each segment in the k-segment fractional-turn winding are symmetrical to each other;

[0013] The integer-turn winding is divided into k groups, which are respectively connected in series with k segments of fractional-turn winding according to the same-name end relationship to form k groups of winding units. The k groups of winding units are connected in parallel inside the transformer by vias, end half holes or metal connectors, or are connected in parallel outside the transformer by peripheral circuits.

[0014] The current direction of each fractional segment in each fractional-turn winding unit is the same clockwise or counterclockwise, achieving ampere-turn balance between the primary and secondary sides;

[0015] The fractional-turn current-sharing transformer adopts the fractional-turn winding designed above, and utilizes the symmetrical characteristics of the current distribution of the fractional segments split on the same layer and the ampere-turn balance relationship between the primary and secondary sides of the transformer to achieve good current-sharing characteristics among the k groups of winding units connected in parallel.

[0016] Furthermore, the switching devices and DC filter capacitors in the peripheral circuit are arranged near the outlet terminals of the k groups of winding units to be connected in parallel. After connecting to the k groups of winding units, they are connected in parallel at the DC voltage, using the DC path of the peripheral circuit to complete the parallel connection of the windings. This shortens the AC current path length, eliminates winding connection terminals, reduces copper losses, and achieves automatic current sharing between parallel windings and devices.

[0017] Furthermore, to optimize the current sharing characteristics among the k parallel-connected winding units, the windings of the multiple fractional-turn winding units are split differently, with the axial vertical projections of at least one fractional segment in one fractional-turn winding unit overlapping with two or more fractional segments in another fractional-turn winding unit. Furthermore, the current direction of each fractional segment on the primary or secondary side is guaranteed to be the same, either clockwise or counterclockwise, and the ampere-turn distribution is symmetrical.

[0018] Furthermore, the transformer's magnetic core includes a central magnetic column and m symmetrical side columns, where m is greater than or equal to 2. When m is greater than or equal to 3, the magnetic core is arranged in a regular m-gon, with the central column located at the center and the m side columns located at each vertex of the regular m-gon. This allows for a larger magnetic conductive area or window area while maintaining a given core footprint.

[0019] In order to further improve the power density of the system, the resonant capacitor in the peripheral circuit is arranged in the area where the primary winding or secondary winding of the transformer is exposed outside the magnetic core, that is, the weak magnetic field of the primary winding and / or secondary winding, to form an AC closed path, thereby realizing the internal integration of the resonant capacitor in the transformer.

[0020] In order to further improve the power density, at least one fractional segment is provided at the primary winding and / or the secondary winding, which does not serve as a k-segment fractional-turn winding and is not connected to the k groups of winding units, thereby forming an adjustable leakage inductance as a resonant inductor in the peripheral circuit, thereby realizing the internal integration of the resonant inductor in the transformer.

[0021] In order to further improve the power density, a fractional segment Wf1 in at least one fractional-turn winding unit is set to overlap with the axial vertical projection of at least two fractional segments in another fractional-turn winding unit. The at least two fractional segments are named Wf2, Wf3,…, Wfi. At least one fractional segment among Wf1 and Wf2, Wf3,…, Wfi is set to be connected in series with the primary integer-turn winding, and the remaining fractional segments are connected in series with the secondary integer-turn winding to form an adjustable leakage inductance as the resonant inductance in the peripheral circuit, thereby realizing the internal integration of the resonant inductance in the transformer.

[0022] To further improve the power density, the axial vertical projection of the primary winding and the axial vertical projection of the secondary winding are set to be asymmetric and their geometric centers do not overlap, forming an adjustable leakage inductance as the resonant inductor in the peripheral circuit, thereby realizing the internal integration of the resonant inductor in the transformer.

[0023] Furthermore, in each fractional-turn winding unit of the primary winding and / or the secondary winding of the transformer, there are at least two fractional-turn winding units, and the two ends of each segment of fractional turns in the fractional-turn winding units are at least separated by two magnetic core side columns.

[0024] A fractional-turn current-sharing inductor comprises a magnetic core and a winding, wherein the magnetic core has a middle column and at least two side columns.

[0025] The winding comprises an integer-turn winding and at least one fractional-turn winding unit, all of which are wound along the center column; each fractional-turn winding unit is symmetrically or asymmetrically split into multiple segments along the center column from a single-turn winding arranged on the same layer; each fractional-turn winding unit is split into the same or different numbers of fractional segments, and different fractional-turn winding units are distributed in the same or different winding layers; different fractional-turn winding units are split in the same or different ways, so that the axial vertical projections of the fractional segments in each fractional-turn winding unit completely or partially overlap;

[0026] The fractional segments of each fractional-turn winding unit are directly connected or connected in series, in parallel, or in a combination of series and parallel to form a k-segment fractional-turn winding, and the axial vertical projections of each segment in the k-segment fractional-turn winding are symmetrical to each other;

[0027] The integer-turn winding is divided into k groups, and each group is connected in series with k segments of fractional-turn winding according to the same end relationship to form k groups of winding units. The k groups of winding units are connected in parallel, and the current direction of each fractional segment in each fractional-turn winding unit is the same clockwise or counterclockwise;

[0028] The fractional-turn current-sharing inductor adopts the fractional-turn winding designed above and utilizes the symmetrical current distribution characteristics of the fractional segments split on the same layer to achieve good current-sharing characteristics among the k sets of winding units connected in parallel.

[0029] The primary winding and the secondary winding of the transformer of the present invention can be made of Litz wire, enameled wire, copper sheet, flat copper wire or PCB winding.

[0030] Compared with the prior art, the present invention has the following advantages:

[0031] The present invention provides a fractional-turn transformer, which not only facilitates fine gain adjustment and optimized magnetic component design by using fractional turns, but also realizes automatic current sharing of parallel windings and meets the design requirements of high power density.

[0032] The fractional-turn current-sharing transformer proposed in the present invention splits the same-layer winding into fractional-turn windings, connects them in series with integer-turn windings, and then connects them in parallel as a whole. At the same time, the current directions of the fractional-turn windings are designed to be connected end to end to ensure the ampere-turn balance of the primary and secondary sides. The symmetrical current distribution characteristics of the fractional-turn windings split in series and the ampere-turn balance relationship between the primary and secondary sides of the transformer are utilized to ensure good current-sharing characteristics between the parallel windings. Compared with the existing current-sharing scheme, the complex structure of the matrix transformer is avoided, and the interconnection vias and corresponding losses required for the parallel cross-connection of the windings are reduced.

[0033] The fractional-turn current-sharing transformer proposed in the present invention is designed with multiple fractional-turn winding units having different winding splitting methods, so that a section of the fractional-turn winding in at least one fractional-turn winding unit overlaps with the axial vertical projection of two or more sections of the fractional-turn winding in another fractional-turn winding unit, and ensures that the current direction of the fractional-turn winding on the primary or secondary side is connected end to end around the center column and the ampere-turn distribution is symmetrical, further optimizing the current distribution between parallel windings.

[0034] The fractional-turn current-sharing transformer proposed in the present invention can arrange the peripheral circuit including the switching device and the DC filter capacitor near the output end of the winding to be connected in parallel, connect it in parallel at the DC voltage after connecting it to the winding, and use the DC path of the peripheral circuit to complete the current closure and parallel connection of the windings, so as to reduce the length of the AC path, reduce copper loss, and realize automatic current sharing between the parallel windings and devices.

[0035] The fractional-turn current-sharing transformer proposed in the present invention realizes resonant inductance through fractional-turn windings and designs resonant capacitors to form the winding AC current path, completing the integration of the transformer and resonant elements and improving the power density of the system.

[0036] The fractional-turn current-sharing transformer proposed in the present invention can achieve fine adjustment of the transformer gain, facilitating the optimized design of magnetic components. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a circuit topology of a multi-phase parallel resonant converter with automatic current sharing proposed in patent CN201910125467.1;

[0038] Figure 2 This is a schematic diagram of an implementation of a fractional-turn winding unit provided on the primary or secondary side of the fractional-turn current-sharing transformer of the present invention. Figure 2 (a) is a schematic diagram of the splitting of a fractional-turn winding unit using a two-leg core, where 100 two-leg cores are used. Figure 2 (b) is a schematic diagram of a split-up fractional-turn winding unit using a quadrilateral magnetic core, where 100 is the quadrilateral magnetic core. Figure 2 (c) is a schematic diagram of the splitting of a fractional-turn winding unit using a polygonal core, where 100 is the polygonal core. Figure 2 (d) is a schematic diagram of the splitting of an integer-turn winding unit using a quadrilateral core. Figure 2 (e) Figure 2 (b) with Figure 2(d) is a schematic diagram of a series connection, wherein 100 is a quadrilateral core, 101 is a first segment of fractional-turn windings, 102 is a second segment of fractional-turn windings, 103 is a third segment of fractional-turn windings, 104 is a schematic diagram of a fourth segment of fractional-turn windings, 105 is a first group of integer-turn windings, 106 is a second group of integer-turn windings, 107 is a third group of integer-turn windings, and 108 is a schematic diagram of a fourth group of integer-turn windings. The arrows in the figure indicate the direction of current in each winding.

[0039] Figure 3 Schematic diagram of an implementation of a fractional-turn current-sharing transformer according to the present invention in which a plurality of fractional-turn winding units are provided on the primary side or the secondary side;

[0040] Figure 3 (a) is a schematic diagram of symmetrical splitting of multiple fractional-turn winding units with the same number of split segments. 201 to 204 are the segments of the windings split from the first fractional-turn winding unit, and 205 to 208 are the segments of the windings split from the second fractional-turn winding unit. 200 is a quadrilateral core.

[0041] Figure 3 (b) is a schematic diagram of symmetrical splitting of multiple fractional-turn winding units with different numbers of split segments, 201-204 are the segments of the winding split from the first fractional-turn winding unit, 205-206 are the segments of the winding split from the second fractional-turn winding unit, and 200 is the magnetic core of the quadrilateral;

[0042] Figure 3 (c) is a schematic diagram of symmetrical or asymmetrical splitting of multiple fractional-turn winding units, 201-203 are the winding segments split from the first fractional-turn winding unit, 204-205 are the winding segments split from the second fractional-turn winding unit, 206-208 are the winding segments split from the third fractional-turn winding unit, and 200 is an octagonal magnetic core;

[0043] Figure 3 (d) is a schematic diagram of overlapping segments of multiple fractional-turn winding units, 201-204 are the segments of the windings split from the first fractional-turn winding unit, 205-208 are the segments of the windings split from the second fractional-turn winding unit, and 200 is the magnetic core of the quadrilateral;

[0044] Figure 4 A schematic diagram of a fractional-turn current-sharing transformer of the present invention in which a plurality of fractional-turn winding units form four sections of fractional-turn windings and are connected in series with integer-turn windings;

[0045] Figure 4 (a) Figure 3 (a) Schematic diagram of the fractional-turn winding units in series forming four sections of fractional-turn windings; Figure 4 (b) Figure 3 (a) Schematic diagram of the fractional-turn winding units in parallel forming four sections of fractional-turn windings; Figure 4 (c) Figure 4 (a) Schematic diagram of series connection with integer-turn winding; 4(d) Figure 4 (b) Schematic diagram of parallel connection with integer-turn windings; 301-304 are the winding segments split from the first fractional-turn winding unit, 305-308 are the winding segments split from the second fractional-turn winding unit, and 309-312 are four groups of integer-turn windings;

[0046] Figure 4 (e) Figure 3 (b) is a schematic diagram of a two-section fractional-turn winding formed by connecting the fractional-turn winding units in series; Figure 4 (f) Figure 3 (b) Schematic diagram of the fractional-turn winding units forming two sections of fractional-turn windings in parallel; Figure 4 (g) Figure 4 (e) Schematic diagram of series connection with integer-turn winding; 4(h) Figure 4 (f) Schematic diagram of parallel connection with integer-turn windings; 301-304 are the winding segments split from the first fractional-turn winding unit, 305-306 are the winding segments split from the second fractional-turn winding unit, and 307-308 are two groups of integer-turn windings;

[0047] Figure 4 (i) Figure 3 (c) Schematic diagram of the fractional-turn winding units connected in series to form four fractional-turn windings; Figure 4 (j) Figure 4 (i) is a schematic projection diagram of the four-section fractional-turn winding structure. Figure 4 (k) Figure 4 (i) Schematic diagram of series connection with integer-turn windings; 301-303 are the individual winding segments of the first fractional-turn winding unit, 304-305 are the individual winding segments of the second fractional-turn winding unit, 306-308 are the individual winding segments of the third fractional-turn winding unit, and 309-312 are four groups of integer-turn windings;

[0048] Figure 4 (l) Figure 3 (d) is a schematic diagram of a four-segment fractional-turn winding structure formed by connecting the fractional-turn winding units in series; Figure 4 (m) is Figure 3 (d) is a schematic diagram of a four-segment fractional-turn winding formed by connecting the fractional-turn winding units in parallel; Figure 4 (n) is Figure 4 (l) Schematic diagram of series connection with an integer-turn winding; Figure 4 (o) Figure 4 (m) Schematic diagram of parallel connection with integer-turn windings; 301-304 are the winding segments split from the first fractional-turn winding unit, 305-308 are the winding segments split from the second fractional-turn winding unit, and 309-312 are four groups of integer-turn windings;

[0049] Among them, 300 is a quadrilateral core;

[0050] Figure 5 Schematic diagram of the parallel connection of windings in the fractional-turn current-sharing transformer of the present invention; Figure 5 (a) is a schematic diagram of the connection between the primary winding and the secondary winding to be connected in parallel through the peripheral circuit; Figure 5 (b) is a schematic diagram of the parallel connection of the primary windings to be connected in parallel through the DC part of the peripheral circuit. Figure 5 (c) is a schematic diagram of the parallel connection of the primary winding and the secondary winding to be connected in parallel inside the transformer. Figure 5 (d) is a schematic diagram of the parallel connection of the primary windings to be connected in parallel inside the transformer; wherein 400 is the magnetic core, 401 is the primary winding, 402 is the secondary winding, 403 is the DC bus input, 404 is the DC bus output, and the peripheral circuit consists of the DC bus input, DC bus output, Q 1-1 ~Q 1-4 and Q 2-1 ~Q 2-4 composition;

[0051] Figure 6 (a) is a schematic diagram of the partial overlap of the primary and secondary fractional-turn windings of the fractional-turn current-sharing transformer of the present invention, wherein the magnetic core is (1-0), the fractional-turn windings of the primary winding are (1-3) and (1-4), the fractional-turn windings of the secondary winding are (1-5) and (1-6), the integer-turn windings of the primary winding are (1-1) and (1-2), the integer-turn windings of the secondary winding are (1-7) and (1-8), the output terminals of the primary winding are (1-9) to (1-12), the output terminals of the secondary winding are (1-13) to (1-16), and the peripheral circuit is controlled by the input voltage V in , Q 1-1 ~Q 1-4 and Q 2-1 ~Q 2-4 Two parallel full-bridge inverter circuits, primary power ground PGND, SR 1-1 ~SR 1-4 and SR 2-1 ~SR 2-4 The two parallel full-bridge rectifier circuits, output voltage V o and the secondary side power ground SGND, i P1 and i P2are the currents flowing through the two sets of parallel windings of the primary winding, i S1 and i S2 are the currents flowing through the two sets of parallel windings of the primary winding;

[0052] Figure 6 (b) Figure 6 (a) Magnetoresistance model, Figure 6 (c) Figure 6 The dual circuit of (b) is Figure 6 (d) Figure 6 (c) Circuit model after scale transformation, Figure 6 (e) Figure 6 (a) Dual inductor model, where N P N is the number of turns of each group of integer turns in the primary winding, S is the number of turns of each group of integer turns in the secondary winding, Φ0 is the magnetic flux flowing through the core center column, Φ1~Φ4 are the magnetic flux flowing through the core side columns 1~4, R g is the air gap reluctance of the core column, R g1 ~R g4 is the air gap reluctance of the core side columns 1 to 4, i P1 and i P2 are the currents flowing through the two sets of parallel windings of the primary winding, i S1 and i S2 are the currents flowing through the two sets of parallel windings of the primary winding;

[0053] Figure 7 (a) is a schematic diagram of the dimensions of a traditional magnetic core with a central column and two symmetrical side columns. Figure 7 (b) is a schematic diagram of the core size with a central column and side columns distributed at the vertices of a regular m-gon, m = 4;

[0054] Figure 8 In order to keep the same floor space and magnetic conductive area, Figure 7 (b) The core and Figure 7 (a) Comparison of the winding width allowed by the traditional magnetic core, where w(θ) is Figure 7 The allowable winding width of the core of (b), w1(θ) is Figure 7 (a) The winding width allowed by the traditional magnetic core;

[0055] Figure 9 Schematic diagram of the integration of the fractional-turn current-sharing transformer and the resonant capacitor of the present invention;

[0056] Figure 10This is a schematic diagram of integrating a fractional-turn current-sharing transformer and a resonant inductor by fractional turns as described in Example 7, wherein P11 to P13 together constitute a first parallel winding on the primary side, P21 to P23 together constitute a second parallel winding on the primary side, S11 to S13 together constitute a first parallel winding on the secondary side, and S21 to S23 together constitute a second parallel winding on the secondary side;

[0057] Figure 11 This is a schematic diagram of integrating a fractional-turn current-sharing transformer and a resonant inductor by fractional turns as described in the eighth embodiment, wherein P11, P12, and W f1 Together they form the first parallel winding on the primary side, P21, P22, W f2 Together they form the second parallel winding of the primary side. The first parallel winding and the second parallel winding of the primary side are connected in parallel through the common ports P1 and P2. S11, S12, and W f1 'Together constitute the first parallel winding of the secondary side, S21, S22, W f3 Together they form the second parallel winding of the secondary side. The first parallel winding and the second parallel winding of the secondary side are connected in parallel via the common ports S1 and S2.

[0058] Figure 12 This is a schematic diagram of integrating a fractional-turn current-sharing transformer and a resonant inductor by using fractional turns as described in Example 9;

[0059] Figure 13 This is a simulation comparison of the current sharing performance of the fractional-turn current-sharing transformer of the present invention and the traditional integer-turn transformer. Figure 13 (a) is the model of the fractional-turn current-sharing transformer used in the simulation, where P11-P13 together constitute the first parallel winding of the primary side, P21-P23 together constitute the second parallel winding of the primary side, S11-S13 together constitute the first parallel winding of the secondary side, and S21-S23 together constitute the second parallel winding of the secondary side; Figure 13 (b) is a model of a conventional integer-turn transformer used in the simulation, where P11 to P13 together constitute the first parallel winding of the primary side, P21 to P23 together constitute the second parallel winding of the primary side, S11 to S13 together constitute the first parallel winding of the secondary side, and S21 to S23 together constitute the second parallel winding of the secondary side; Figure 13 (c) is the current sharing simulation result of the fractional-turn current sharing transformer. Figure 13 (d) is the current sharing simulation result of the traditional integer-turn transformer. DETAILED DESCRIPTION

[0060] The accompanying drawings disclose several specific implementation examples of the present invention in a non-limiting manner. The present invention will be further described below with reference to the accompanying drawings.

[0061] Example 1:

[0062] A fractional-turn current-sharing transformer according to the present invention is Figures 2 to 4 As shown. The transformer includes a magnetic core and a winding, wherein the magnetic core has a central column and at least two side columns, the winding includes a primary winding and a secondary winding, and the primary winding and / or secondary winding of the transformer includes an integer-turn winding and at least one fractional-turn winding unit, and all windings are wound along the central column. The following will specifically describe the implementation of the present invention based on the number and composition of the fractional-turn winding units provided. It should be noted that the implementation described below is only a typical embodiment of the present invention, which is used to help understand the technical solution of the present invention. Those skilled in the art will understand that, without departing from the concept of the present invention, several variations and improvements can be made, and these all fall within the scope of protection of the present invention.

[0063] Structure (1): The fractional-turn current-sharing transformer comprises a fractional-turn winding unit, which is arranged in the primary winding or the secondary winding.

[0064] Taking the fractional-turn winding unit set in the primary winding as an example, the fractional-turn winding unit is symmetrically divided into n sections (n≥2) along the center column from one turn of winding in the same layer, as shown in FIG. Figure 2 (a)-2(c) shown below; Figure 2 (b) is used as an example to illustrate the specific design of the structure. Figure 2 (b) It can be seen that the fractional-turn winding unit is divided into four sections symmetrically along the center column from one turn winding in the same layer, and the integer-turn winding of the primary winding is divided into four groups, as shown in Figure 2 As shown in (d), the four fractional segments are used as four fractional turn windings, which are connected in series with the four groups of integer turn windings according to the same end relationship, as shown in Figure 2. Figure 2 As shown in (e), the parallel connection is then achieved inside the transformer by welding vias, end half holes or metal connectors, or by external peripheral circuits; the current directions of the four fractional segments on the same layer in the fractional-turn winding unit are all clockwise, that is, the current directions are connected end to end, ensuring the ampere-turn balance of the primary and secondary sides; the symmetrical characteristics of the current distribution of the symmetrically split fractional-turn winding units on the same layer and the ampere-turn balance relationship of the primary and secondary sides of the transformer are utilized to ensure good current sharing characteristics between the four parallel winding units.

[0065] Structure (2): The primary winding and / or the secondary winding of the transformer comprises a plurality of fractional-turn winding units.

[0066] A. Taking the fractional-turn winding unit as an example, the number of segments and the splitting method of each fractional-turn winding unit are the same.

[0067] The first and second fractional-turn winding units in the two fractional-turn winding units are respectively divided into four segments symmetrically along the center column from one turn of winding in the same layer. The two fractional-turn winding units are divided into the same number of segments. Different fractional-turn winding units can be distributed in the same or different winding layers, and the splitting method of different fractional-turn winding units is the same, that is, the axial vertical projections of each fractional segment in each fractional-turn winding unit completely overlap, such as Figure 3 As shown in (a); the two fractional-turn winding units provided can constitute four sections of fractional-turn windings, each section of which is composed of fractional segments selected from each fractional-turn winding unit connected in series or in parallel. For example, fractional segment 301 is connected in series with fractional segment 305, or fractional segment 301 is connected in parallel with fractional segment 308 to form a section of fractional-turn winding, so that the axial vertical projections of each section of the four sections of fractional-turn winding are symmetrical to each other. The four sections of fractional-turn winding formed in series are as follows: Figure 4 As shown in (a), four fractional-turn windings are connected in parallel. Figure 4 As shown in (b), the integer turns of the primary side are divided into 4 groups, which are connected in series with the 4 fractional turns of the winding according to the same end relationship. Figure 4 The four fractional-turn windings in (a) are connected in series with the four integer-turn windings. Figure 4 (c) Figure 4 The four fractional-turn windings and the four integer-turn windings in (b) are connected in series as shown in Figure 4 (d) As shown; then, the parallel connection is achieved inside the transformer by welding vias, end half holes or metal connectors, or the parallel connection is achieved outside by a peripheral circuit; the current direction of the four fractional segments on the same layer in each fractional-turn winding unit is the same as the clockwise direction, that is, the current direction is connected end to end, ensuring the ampere-turn balance of the primary and secondary sides; utilizing the symmetrical characteristics of the current distribution of the symmetrically split fractional segments on the same layer and the ampere-turn balance relationship of the primary and secondary sides of the transformer, the four parallel winding units have good current sharing characteristics.

[0068] B. Each fractional-turn winding unit has different number of segments but the same splitting method.

[0069] Taking two fractional-turn winding units both arranged in the primary winding as an example, the first fractional-turn winding unit is symmetrically divided into four sections along the center column from one turn of winding in the same layer, and the second fractional-turn winding unit is symmetrically divided into two sections along the center column from one turn of winding in the same layer. Different fractional-turn winding units can be distributed in the same or different winding layers, and the splitting method of different fractional-turn winding units is the same, that is, the axial vertical projections of each section of the fractional-turn winding in each fractional-turn winding unit can completely overlap, such as Figure 3 (b)

[0070] The two fractional-turn winding units provided together constitute two sections of fractional-turn windings, and each section of the fractional-turn winding is composed of fractional sections selected from each fractional-turn winding unit connected in series and / or in parallel, so that the axial vertical projections of each section of the two sections of the fractional-turn winding are symmetrical to each other; Figure 4 As shown in (e), the fractional segments 302 and 303 in the first fractional-turn winding unit are connected in series with the fractional segment 305 in the second fractional-turn winding unit, and the fractional segments 301 and 304 in the first fractional-turn winding unit are connected in series with the fractional segment 306 in the second fractional-turn winding unit, thereby forming two sections of fractional-turn windings, and the axial vertical projections of the two sections of fractional-turn windings are symmetrical circles; as shown in Figure 4 As shown in (f), the fractional segments 302 and 303 in the first fractional-turn winding unit are connected in parallel with the fractional segment 306 in the second fractional-turn winding unit, and the fractional segments 301 and 304 in the first fractional-turn winding unit are connected in parallel with the fractional segment 305 in the second fractional-turn winding unit, forming two-segment fractional-turn windings, and the axial vertical projections of the two-segment fractional-turn windings are symmetrical semicircles;

[0071] At the same time, the integer-turn winding is split into two groups, which are connected in series with the two fractional-turn windings according to the same-name end relationship. Figure 4 The series connection of the two fractional-turn windings and the two integer-turn windings in (e) is as follows: Figure 4 (g) Figure 4 The series connection of the two fractional-turn windings and the two integer-turn windings in (f) is as follows: Figure 4 (h) As shown; then, the parallel connection is achieved inside the transformer by welding vias, end half holes or metal connectors, or the parallel connection is achieved externally by a peripheral circuit; the current flow direction of the fractional segments on the same layer in each fractional-turn winding unit is the same counterclockwise, ensuring the ampere-turn balance of the primary and secondary sides; the symmetrical characteristics of the current distribution of the symmetrically split fractional-turn windings on the same layer and the ampere-turn balance relationship of the primary and secondary sides of the transformer are utilized to ensure good current sharing characteristics between the two parallel winding units.

[0072] C. Each fractional-turn winding unit has different number of segments and different splitting methods.

[0073] Taking the example of three fractional-turn winding units all arranged in the secondary winding, the first and third fractional-turn winding units are asymmetrically split into three sections along the center column from one turn of winding in the same layer, and the second fractional-turn winding unit is symmetrically split into two sections along the center column from one turn of winding in the same layer. Different fractional-turn winding units can be distributed in the same or different winding layers, and the splitting methods of different fractional-turn winding units are different, that is, the axial vertical projections of each section of the fractional-turn winding in each fractional-turn winding unit can partially overlap, such as the axial vertical projections of the fractional segments 204 and the fractional segments 201 and 203 partially overlap, such as Figure 3 (c)

[0074] The three fractional-turn winding units provided can constitute four sections of fractional-turn windings, and each section of fractional-turn winding is composed of fractional sections selected from each fractional-turn winding unit connected in series, such as Figure 4 As shown in (i), the axial vertical projections of each segment of the 4-segment fractional-turn winding are made symmetrical to each other, as shown in Figure 4 (j) As shown; At the same time, the integer turn winding is divided into 4 groups, and connected in series with the 4 segments of fractional turn winding according to the relationship of the same end, as shown in FIG. Figure 4 As shown in (k), the parallel connection is then achieved inside the transformer by welding vias, end half holes or metal connectors, or by external peripheral circuits; the current direction of the fractional segments on the same layer in each fractional-turn winding unit is counterclockwise to ensure the ampere-turn balance of the primary and secondary sides; the symmetrical characteristics of the current distribution of the fractional segments split in the same layer and the ampere-turn balance relationship of the primary and secondary sides of the transformer are utilized to ensure good current sharing characteristics between the four parallel winding units.

[0075] D. Each fractional-turn winding unit has the same number of segments but different splitting methods.

[0076] Taking two fractional-turn winding units both arranged in the secondary winding as an example, the two fractional-turn winding units are symmetrically divided into four segments along the center column from one turn of winding in the same layer. The number of segments divided into different fractional-turn winding units is the same. Different fractional-turn winding units can be distributed in the same or different winding layers, and the splitting methods of different fractional-turn winding units are different, that is, the axial vertical projections of each fractional segment in each fractional-turn winding unit partially overlap, such as the axial vertical projections of fractional segment 201 partially overlap with the axial vertical projections of fractional segments 205 and 208, respectively. Figure 3 (d) As shown; all the fractional-turn winding units provided can constitute 4 sections of fractional-turn windings, each section of fractional-turn winding is composed of fractional segments selected from each fractional-turn winding unit connected in series or in parallel, for example, fractional segment 301 is connected in series with fractional segment 306 or in parallel with fractional segment 305 to form a fractional segment, so that the axial vertical projections of each segment in the 4 sections of fractional-turn winding are symmetrical to each other, wherein the 4 sections of fractional-turn winding are formed in series as shown Figure 4 (l) shows that four fractional-turn windings are connected in parallel. Figure 4 (m) As shown; the integer turn winding is divided into 4 groups, which are connected in series with the 4 segments of fractional turn windings according to the same end relationship. Figure 4 The series connection of the four fractional-turn windings and the four integer-turn windings in (l) is as follows: Figure 4 (n) shown, Figure 4 The series connection of the 4 fractional-turn windings and the 4 integer-turn windings in (m) is as follows: Figure 4(o) is shown; then, the parallel connection is achieved inside the transformer by welding vias, end half holes or metal connectors, or the parallel connection is achieved outside by a peripheral circuit; the current direction of the four fractional segments on the same layer in each fractional-turn winding unit is the same as the clockwise direction, that is, the current direction is connected end to end, ensuring the ampere-turn balance of the primary and secondary sides; utilizing the symmetrical characteristics of the current distribution of the symmetrically split fractional segments on the same layer and the ampere-turn balance relationship of the primary and secondary sides of the transformer, the four parallel winding units have good current sharing characteristics.

[0077] Example 2:

[0078] This embodiment is further designed based on the first embodiment in that:

[0079] The peripheral circuit including the switching device and the DC filter capacitor is arranged near the output terminal of the winding to be connected in parallel, and connected in parallel at the DC voltage after being connected to the winding. The DC path of the peripheral circuit is used to complete the parallel connection of the windings, shortening the length of the AC current path, eliminating the winding connection terminals, reducing copper loss, and realizing automatic current sharing between the parallel windings and devices. Figure 5 As shown in (a) and (b).

[0080] Compared with the traditional method of parallel connection by welding through holes, end half holes or metal connectors inside the transformer, Figure 5 As shown in (c) and (d), it is obvious that Figure 5 The AC paths 401 and 402 in (a) and (b) are both shorter than Figure 5 (c) and (d) show the AC paths 401 and 402. Figure 5 (b) and Figure 5 (d) As can be seen, the parallel connection of peripheral circuits replaces the AC path outside the magnetic core required by the traditional parallel connection method with a DC path through the PGND. According to the Dowell equation, the resistance of the AC path is several times that of the DC path, and the more layers of parallel windings there are, the more the AC path resistance can reach dozens of times that of the DC path. Therefore, the parallel connection of peripheral circuits not only shortens the AC current path length, but also reduces the resulting connection resistance by less than the traditional parallel connection method, effectively reducing copper losses and facilitating the optimized design of magnetic components.

[0081] Example 3:

[0082] This embodiment is further designed based on the first embodiment in that: in order to optimize the current sharing characteristics between the parallel groups of series winding units, the winding splitting methods of multiple fractional-turn winding units should be different, and at least one fractional-turn winding section in one fractional-turn winding unit should overlap with the axial vertical projection of two or more fractional-turn winding sections in another fractional-turn winding unit, and ensure that the current direction of the fractional-turn winding on the primary or secondary side is connected end to end around the center column and the ampere-turn distribution is symmetrical. The following takes two groups of winding units on the primary side, two groups of winding units on the secondary side, and one fractional-turn winding unit on each primary and secondary side as an example. Figure 6 As shown in (a), the physical mechanism of current sharing optimization brought about by partially overlapping the axial vertical projections of the fractional segments of the winding units with different fractional turns is explained.

[0083] Since each segment of the integer-turn winding surrounds the magnetic flux of the coupled middle column, and each segment of the fractional-turn winding surrounds the magnetic flux of the coupled corresponding side column, the reluctance model of the fractional-turn current-sharing winding can be obtained, as shown in Figure 6 (b). By the duality principle, Figure 8 The magnetic flux Φ0~Φ4 flowing through each magnetic column in (b) is expressed as a voltage drop, and the magnetic voltage drop N on each magnetic column P i P1 、N P i P2 、N S i S1 、N S i S2 、i P1 、i P2 、i S1 、i S2 Expressed as current, the dual equivalent circuit can be obtained, as Figure 6 (c) As shown. Then, under the premise of ensuring that Kirchhoff's law in the dual circuit remains unchanged, Figure 6 All the voltage drops Φ0 to Φ4 in (c) are multiplied by N P , all current N P i P1 、N P i P2 、N S i S1 、N S i S2 、i P1 、i P2 、i S1 、i S2 Divide by N P , and all the magnetic resistance R g 、R g1 ~R g4 Multiply by N P 2 , we can get the dual equivalent circuit after scale transformation, as Figure 6 (d) is shown. Figure 6 In (d), according to the voltage drop, it can be divided into five parallel modules. P1 、i P2 、N S / N P i S1 、N S / N P i S2 、N P 2 R g For example, according to professional common sense, "the inductance value is equal to the square of the number of turns divided by the magnetic resistance" and "the ampere-turn balance of the primary and secondary sides of the transformer", it can be known that the parallel module i P1 、i P2 、N S / N P i S1 、N S / N P i S2 、N P 2 R g It can be regarded as an excitation inductance of N P 2 R g , a transformer unit with two parallel primary windings and two parallel secondary windings. By analogy to the above equivalent idea Figure 6 From the remaining parallel modules in (d), we can get the dual inductance model of this case, as Figure 6 (e) According to common sense, the dual inductance model can accurately describe the current-voltage relationship of each winding in the transformer. Figure 6 (e) Accurately reveals the physical mechanism of current sharing between parallel windings caused by partial overlap of primary and secondary fractional-turn windings.

[0084] from Figure 6(e) It can be seen that because the primary fractional-turn winding (1-3) and the upper half of the secondary fractional-turn windings (1-5) and (1-6) form a "primary series-secondary parallel" structure, current sharing is naturally achieved between the secondary fractional-turn windings (1-5) and (1-6). Furthermore, because the secondary fractional-turn winding (1-5) is connected in series with the secondary integer-turn winding (1-7), and the secondary fractional-turn winding (1-6) is connected in series with the secondary integer-turn winding (1-8), current sharing is achieved between the two parallel secondary windings. In addition, because the secondary fractional-turn winding (1-5) and the upper half of the primary fractional-turn winding (1-3) and the lower half of (1-4) form a "secondary series-primary parallel" structure, current sharing is naturally achieved between the primary fractional-turn windings (1-3) and (1-4). Furthermore, because the primary fractional-turn winding (1-3) is connected in series with the primary integer-turn winding (1-1), and the primary fractional-turn winding (1-4) is connected in series with the primary integer-turn winding (1-2), current sharing is achieved between the two primary parallel windings. Thus, the partial overlap of the vertical projections of the fractional segments creates a crossover "primary-series-secondary-parallel" and "secondary-series-primary-parallel" structure between the primary and secondary parallel windings, achieving natural current sharing between the two primary parallel windings and the two secondary parallel windings.

[0085] Example 4:

[0086] This embodiment is further designed based on the first embodiment in that: the transformer core includes a central magnetic column and m symmetrical side columns, where m is greater than or equal to 2; when m is greater than or equal to 3, the core is arranged in a regular m-gon, where the central column is set at the center of the regular m-gon and the m side columns are set at each vertex of the regular m-gon, so as to obtain a better magnetic conductive area and window area within a fixed footprint. Compared with the traditional magnetic core when m=2, Figure 7 As shown in (a), by distributing the side columns of the core at the vertices of the regular m-gon, as Figure 7 As shown in (b), this allows for better copper and iron utilization within a fixed transformer footprint, further facilitating optimized magnetic component design and increased power density. The following comparison of a core with m = 4 and a conventional core demonstrates the superiority of a core arranged in a regular m-gon.

[0087] For a fair comparison, the two cores are compared under the premise of the same magnetic conductive area and the same floor space. Therefore, the relationship between the various dimensional parameters of the core of the present invention and the various dimensional parameters of the traditional core is as follows:

[0088]

[0089] w(θ)=R0(θ)-r0(θ) (5)

[0090]

[0091]

[0092] According to formulas (5) and (9), when l = 30 mm, the comparison results of the winding widths allowed by the two cores under the premise of the same magnetic conductive area and the same floor space can be obtained, as follows: Figure 8 As shown. Figure 8 As can be seen, compared to traditional magnetic cores, the magnetic core of the present invention allows for wider winding widths, which means lower copper losses. Since the cores have the same footprint and magnetic conductive area, the iron losses of the two cores are also the same. Therefore, the magnetic core of the present invention can achieve lower overall losses, meaning higher energy transfer efficiency, while maintaining the same overall losses. It can also achieve a smaller size, meaning higher power density, while maintaining the same overall losses.

[0093] Embodiment 5:

[0094] This embodiment is further designed on the basis of the first embodiment in that: the primary winding and the secondary winding of the transformer can be made of Litz wire, enameled wire, copper sheet, flat copper wire or PCB winding.

[0095] Example 6:

[0096] This embodiment is further designed on the basis of the first embodiment in that: in order to further improve the power density of the system, the resonant capacitor in the peripheral circuit is arranged at the weak magnetic field of the primary winding and / or the secondary winding of the transformer, that is, the primary winding and / or the secondary winding of the transformer are exposed outside the magnetic core to form an AC closed path, such as Figure 9 As shown, the resonant capacitor is integrated inside the transformer.

[0097] Embodiment seven:

[0098] This embodiment is further designed on the basis of the first and fourth embodiments in that: in order to further improve the power density, at least one fractional segment is provided at the primary winding and / or the secondary winding, which is not used as a k-segment fractional-turn winding and is not connected to the k groups of winding units, thereby forming an adjustable leakage inductance as a resonant inductor in the peripheral circuit, thereby realizing the internal integration of the resonant inductor in the transformer, such as Figure 10 As shown, the two fractional segments P13 and P21 in a fractional-turn winding unit on the primary side are each used as a fractional-turn winding, while the other two fractional segments in the fractional-turn winding unit are not used as fractional-turn windings (not shown in the figure). The two fractional segments S13 and S21 in a fractional-turn winding unit on the secondary side are each used as a fractional-turn winding, while the other two fractional segments in the fractional-turn winding unit are not used as fractional-turn windings (not shown in the figure). The above structural design forms a leakage inductance for adjustment as a resonant inductor in the peripheral circuit, achieving the purpose of integrating the resonant inductor within the transformer.

[0099] Embodiment 8:

[0100] This embodiment is further designed on the basis of the first and fourth embodiments in that: to further improve the power density, by setting a fractional segment Wf1 in at least one fractional turn winding unit to overlap with the axial vertical projection of at least two fractional segments in another fractional turn winding unit, the at least two fractional segments are named Wf2, Wf3, ..., Wfi, setting at least one fractional segment among Wf1 and Wf2, Wf3, ..., Wfi in series with the primary integer turn winding, and the remaining fractional segments in series with the secondary integer turn winding, forming an adjustable leakage inductance as the resonant inductance in the peripheral circuit, realizing the internal integration of the resonant inductance in the transformer. Figure 11 As shown, the fractional segment Wf1 of a fractional-turn unit is set to overlap the axial vertical projection of the fractional segments Wf2 and Wf3 of another fractional-turn unit. The fractional segments Wf2 and Wf3 are designed to be connected in series with the primary integer-turn winding, and the remaining fractional segments are connected in series with the secondary integer-turn winding, thereby realizing adjustable leakage inductance as the resonant inductor in the peripheral circuit and achieving the purpose of integrating the resonant inductor inside the transformer.

[0101] Embodiment 9:

[0102] This embodiment is further designed on the basis of the first and fourth embodiments: in order to further improve the power density, the axial vertical projection of the primary winding and the axial vertical projection of the secondary winding are set to be asymmetric and their geometric centers do not overlap, so as to realize an adjustable leakage inductance as a resonant inductance in the peripheral circuit, such as Figure 12 As shown, the purpose of integrating the resonant inductor inside the transformer is achieved.

[0103] Embodiment 10:

[0104] This embodiment is further designed on the basis of Embodiments 1, 3, and 4 in that: in each fractional-turn winding unit of the primary winding and / or the secondary winding of the transformer, there are at least two fractional-turn winding units, and the two ends of each segment of the fractional turns in them are separated by at least two magnetic core side columns.

[0105] Example 11:

[0106] The fractional-turn current-sharing inductor of this embodiment comprises a magnetic core and a winding, wherein the magnetic core has a center leg and at least two side legs, and is characterized in that:

[0107] The winding includes an integer-turn winding and at least one fractional-turn winding unit, and all windings are wound along the center column. Each fractional-turn winding unit is symmetrically or asymmetrically divided into multiple segments along the center column from a single-turn winding arranged on the same layer. The number of fractional segments divided into each fractional-turn winding unit is the same or different, and different fractional-turn winding units are distributed in the same or different winding layers. Different fractional-turn winding units use the same or different splitting methods, so that the axial vertical projections of the fractional segments in each fractional-turn winding unit completely overlap or partially overlap.

[0108] The fractional segments of each fractional-turn winding unit are directly connected or connected in series, in parallel, or in a combination of series and parallel to form a k-segment fractional-turn winding, and the axial vertical projections of each segment in the k-segment fractional-turn winding are symmetrical to each other;

[0109] The integer-turn winding is divided into k groups, and each group is connected in series with k segments of fractional-turn winding according to the same end relationship to form k groups of winding units. The k groups of winding units are connected in parallel, and the current direction of each fractional segment in each fractional-turn winding unit is the same clockwise or counterclockwise;

[0110] The fractional-turn current-sharing inductor adopts the fractional-turn winding designed above and utilizes the symmetrical current distribution characteristics of the fractional segments split on the same layer to achieve good current-sharing characteristics among the k sets of parallel-connected winding units.

[0111] Application Example 1:

[0112] In order to illustrate the effectiveness of the fractional-turn current-sharing transformer proposed in the third embodiment of the present invention in improving the current-sharing characteristics of the parallel windings, the following example is used: Figure 7 (b) shows the core. The proposed fractional-turn current-sharing transformer and the traditional integer-turn transformer were simulated in COMSOL to compare their parallel winding current-sharing characteristics. The core geometry parameters used in the simulation are: c = 7.42mm, w = 7.38mm, R0 = 14.733mm, r0 = 7.153mm, and air gap g = 0.05mm. The simulated fractional-turn current-sharing transformer model is shown in Figure 1. Figure 13 As shown in (a), the primary winding consists of two 2.5-turn windings in parallel, and the secondary winding consists of two 2.5-turn windings in parallel; the model of the simulated traditional integer-turn transformer is as follows Figure 13 As shown in (b), the primary winding consists of two 3-turn windings in parallel, and the secondary winding consists of two 3-turn windings in parallel; both are excited by 20A current. Figure 13 (c) shows the current distribution results of the proposed fractional-turn current-sharing transformer. Figure 13 (d) shows the current distribution results of the traditional integer-turn transformer. Figure 13 (c) and Figure 13 (d) It is obvious that the parallel windings of the fractional-turn current-sharing transformer proposed in the present invention have excellent current-sharing characteristics.

[0113] Application Example 2:

[0114] In order to verify the effectiveness of the adjustable leakage inductance integrated resonant inductor by fractional turns proposed in Example 8 of the present invention, the following example is used: Figure 7 The magnetic core shown in (b) was constructed in COMSOL. Figure 11 The simulation model of an integrated resonant inductor with adjustable leakage inductance achieved through fractional turns is shown. The geometric parameters of the magnetic core used in the simulation are: c = 7.42mm, w = 7.38mm, R0 = 14.733mm, r0 = 7.153mm, air gap g1 = 0.05mm, g2 = 0.1mm, g3 = 0.2mm. Table 1 shows the leakage inductance of the transformer obtained by simulation under different air gaps. As can be seen from Table 1, the resonant inductance can be adjusted within the range of 0.56μH to 1.57μH, verifying the effectiveness of the present invention.

[0115] Table 1 Simulation results of adjustable leakage inductance of application example 2

[0116]

Claims

1. A fractional-turn current-sharing transformer, comprising a magnetic core and windings, wherein the magnetic core has a center leg and at least two side legs, and the windings include a primary winding and a secondary winding, characterized in that: The primary winding and / or secondary winding of the transformer includes an integer-turn winding and at least one fractional-turn winding unit, and all windings are wound along the center column. Each fractional-turn winding unit is symmetrically or asymmetrically divided into multiple segments along the center column from a single-turn winding arranged on the same layer. The number of fractional segments divided into each fractional-turn winding unit is the same or different, and different fractional-turn winding units are distributed in the same or different winding layers. Different fractional-turn winding units are divided in the same or different ways, so that the axial vertical projections of the fractional segments in each fractional-turn winding unit completely or partially overlap. The fractional segments of each fractional-turn winding unit are directly connected or connected in series, in parallel, or in a combination of series and parallel to form a k-segment fractional-turn winding, and the axial vertical projections of each segment in the k-segment fractional-turn winding are symmetrical to each other; The integer-turn winding is divided into k groups, which are respectively connected in series with k segments of fractional-turn winding according to the same-name end relationship to form k groups of winding units. The k groups of winding units are connected in parallel inside the transformer by vias, end half holes or metal connectors, or are connected in parallel outside the transformer by peripheral circuits. The current direction of each fractional segment in each fractional-turn winding unit is the same clockwise or counterclockwise, achieving ampere-turn balance between the primary and secondary sides; The fractional-turn current-sharing transformer adopts the fractional-turn winding designed above, and utilizes the symmetrical characteristics of the current distribution of the fractional segments split on the same layer and the ampere-turn balance relationship between the primary and secondary sides of the transformer to achieve good current-sharing characteristics among the k groups of winding units connected in parallel.

2. The fractional-turn current-sharing transformer according to claim 1, characterized in that: The switching devices and DC filter capacitors in the peripheral circuit are arranged near the output terminals of the k groups of winding units to be connected in parallel, and are connected in parallel at the DC voltage after being connected to the k groups of winding units, and the parallel connection of the windings is completed using the DC path of the peripheral circuit.

3. The fractional-turn current-sharing transformer according to claim 1, characterized in that: The windings of the multiple fractional-turn winding units are split in different ways, and an axial vertical projection of a fractional segment in at least one fractional-turn winding unit overlaps with two or more fractional segments in another fractional-turn winding unit.

4. The fractional-turn current-sharing transformer according to claim 1, characterized in that: The magnetic core of the transformer includes a central magnetic column and m symmetrical side columns, where m is greater than or equal to 2; when m is greater than or equal to 3, the magnetic core is arranged in a regular m-gon, wherein the central column is arranged at the center of the regular m-gon and the m side columns are arranged at each vertex of the regular m-gon.

5. The fractional-turn current-sharing transformer according to claim 1, characterized in that: The resonant capacitor in the peripheral circuit is arranged in the area where the primary winding or the secondary winding of the transformer is exposed outside the magnetic core, forming an AC closed path, thereby realizing the internal integration of the resonant capacitor in the transformer.

6. The fractional-turn current-sharing transformer according to claim 1 or 4, characterized in that: At least one fractional segment is provided at the primary winding and / or the secondary winding, which does not serve as a k-segment fractional-turn winding and is not connected to the k groups of winding units, thereby forming an adjustable leakage inductance as a resonant inductor in the peripheral circuit, thereby realizing the internal integration of the resonant inductor in the transformer.

7. The fractional-turn current-sharing transformer according to claim 1 or 4, characterized in that: A fractional segment Wf1 in at least one fractional-turn winding unit is set to overlap with the axial vertical projection of at least two fractional segments in another fractional-turn winding unit, and the at least two fractional segments are named Wf2, Wf3,…, Wfi. At least one fractional segment among Wf1 and Wf2, Wf3,…, Wfi is set to be connected in series with the primary integer-turn winding, and the remaining fractional segments are connected in series with the secondary integer-turn winding to form an adjustable leakage inductance as the resonant inductance in the peripheral circuit, thereby realizing the internal integration of the resonant inductance in the transformer.

8. The fractional-turn current-sharing transformer according to claim 1, characterized in that: The axial vertical projection of the primary winding and the axial vertical projection of the secondary winding are set to be asymmetric and their geometric centers do not overlap, so as to form an adjustable leakage inductance as a resonant inductor in the peripheral circuit, thereby realizing the internal integration of the resonant inductor in the transformer.

9. The fractional-turn current-sharing transformer according to claim 1, 3 or 4, characterized in that: In each fractional-turn winding unit of the primary winding and / or the secondary winding of the transformer, there are at least two fractional-turn winding units, and the two ends of each segment of the fractional turns in the units are at least separated by two magnetic core side columns.

10. A fractional-turn current-sharing inductor, comprising a magnetic core and a winding, wherein the magnetic core has a center leg and at least two side legs, characterized in that: The winding comprises an integer-turn winding and at least one fractional-turn winding unit, all of which are wound along the center column; each fractional-turn winding unit is symmetrically or asymmetrically split into multiple segments along the center column from a single-turn winding arranged on the same layer; each fractional-turn winding unit is split into the same or different numbers of fractional segments, and different fractional-turn winding units are distributed in the same or different winding layers; different fractional-turn winding units are split in the same or different ways, so that the axial vertical projections of the fractional segments in each fractional-turn winding unit completely or partially overlap; The fractional segments of each fractional-turn winding unit are directly connected or connected in series, in parallel or in a combination of series and parallel to form a k-segment fractional-turn winding, and the axial vertical projections of each segment in the k-segment fractional-turn winding are symmetrical to each other; The integer-turn winding is divided into k groups, and each group is connected in series with k segments of fractional-turn winding according to the same end relationship to form k groups of winding units. The k groups of winding units are connected in parallel, and the current direction of each fractional segment in each fractional-turn winding unit is the same clockwise or counterclockwise; The fractional-turn current-sharing inductor adopts the fractional-turn winding designed above and utilizes the symmetrical current distribution characteristics of the fractional segments split on the same layer to achieve good current-sharing characteristics among the k sets of winding units connected in parallel.

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