A planar transformer with trapezoidal double-concave waist side column for CDR converter

Abstract

The present application belongs to the technical field of high-frequency planar transformer, and relates to a planar transformer with trapezoidal double-concave waist side column for CDR converter, which comprises a primary 8-shaped winding and a secondary fractional-turn winding, two circular middle column magnetic cores, two rectangular side column magnetic cores and a trapezoidal double-concave waist side column magnetic core; the trapezoidal double-concave waist core column is located in the middle of the two circular middle column magnetic cores and is close to the outer side, and forms a triangular shape together with the circular core column; the primary 8-shaped winding is wound in the shape of 8 in the counterclockwise direction around the two circular core columns; the secondary fractional-turn winding is composed of four independent half-turn windings and is wound around the two rectangular side column magnetic cores and the two circular middle column magnetic cores; the present application solves the problem of simultaneously realizing transformer inductance magnetic integration and winding fractional turns of the CDR topology transformer, so that the CDR topology transformer can still take into account the advantages of magnetic integration and fractional turns in the freewheeling state, and the loss of the whole machine is significantly reduced.

Description

Technical Field

[0001] This invention belongs to the field of high-frequency planar transformer technology, specifically relating to a planar transformer with trapezoidal double concave waist side columns for CDR converters. Background Technology

[0002] High-frequency planar transformers are isolation and power conversion components used in switching power supplies. Planar transformers are a new type of transformer that uses PCB windings instead of traditional Litz wire windings, resulting in a smaller size and higher power density. The operating frequency of planar transformers ranges from several kilohertz to several megahertz. In fields such as data center power supplies, aerospace power supplies, and communication power supplies, it is often necessary for the power supply to convert higher DC voltages to lower DC voltages and to have a large output current carrying capacity. Depending on the application and requirements, switching power supplies employ various topologies, among which the single-stage CDR topology is characterized by high efficiency and good dynamic characteristics.

[0003] However, the CDR topology requires both a transformer and an inductor. While existing magnetic integration technology can integrate the transformer and inductor into a single core, it cannot meet the requirements of the CDR converter's unique freewheeling operation, where both primary and secondary windings of the transformer are simultaneously conducting when the primary switch is off and the secondary switch is on.

[0004] Therefore, there is an urgent need for a magnetically integrated fractional-turn transformer that can meet the freewheeling state requirements of CDR converters to solve the above-mentioned technical problems. Summary of the Invention

[0005] This invention provides the following technical solution: a planar transformer with trapezoidal double concave waist-shaped side posts for a CDR converter, comprising: a magnetic core and windings; the magnetic core includes a magnetic core top plate and a magnetic core body, and the windings include a primary side figure-eight winding and a secondary side fractional-turn winding; the magnetic core body is provided with a first magnetic post, a second magnetic post, a third magnetic post, a fourth magnetic post, and a fifth magnetic post protruding towards the magnetic core top plate in sequence along the length direction of the magnetic core body, wherein the first and fifth magnetic posts are square posts, the second and fourth magnetic posts are cylindrical posts, and the third magnetic post is a square post. The column is a trapezoidal column with an isosceles trapezoidal cross-section; the primary side figure-eight winding is in the shape of an "8"; the secondary side fractional-turn winding is composed of four semi-circular first half-turn windings, second half-turn windings, third half-turn windings, and fourth half-turn windings spliced ​​together to form two rings; the two ends of the semi-circular first half-turn windings and second half-turn windings are connected in series to form a ring after being electrically connected through rectifier tubes and secondary capacitors respectively; the two ends of the semi-circular third half-turn windings and fourth half-turn windings are connected in series to form a ring after being electrically connected through rectifier tubes and secondary capacitors respectively.

[0006] The two loops of the "8" shape of the primary figure-8 winding are respectively wound and sleeved on the second magnetic column and the fourth magnetic column, and the ring formed by electrically connecting the first half-turn winding and the second half-turn winding and the ring formed by electrically connecting the third half-turn winding and the fourth half-turn winding are respectively sleeved on the second magnetic column and the fourth magnetic column; the sum of the magnetic flux areas of the first magnetic column and the fifth magnetic column is equal to the magnetic flux area of the third magnetic column.

[0007] Preferably, both the top core plate and the bottom plate of the core main body are bat-shaped and parallel to each other.

[0008] Preferably, the geometric centers of the first magnetic column, the second magnetic column, the fourth magnetic column and the fifth magnetic column are located on the same straight line.

[0009] More preferably, the third magnetic column, the second magnetic column and the fourth magnetic column are arranged in a triangular "pin" shape.

[0010] More preferably, the two waists of the isosceles trapezoid of the third magnetic column face the second magnetic column and the fourth magnetic column respectively.

[0011] More preferably, arc-shaped grooves are respectively provided on the two waists of the isosceles trapezoid of the third magnetic column.

[0012] Preferably, no air gap is provided at the joints of the first magnetic column, the third magnetic column and the fifth magnetic column with the top core plate; air gaps are provided at the joints of the second magnetic column and the fourth magnetic column with the top core plate.

[0013] More preferably, the width of the air gap between the second magnetic column and the top core plate and between the fourth magnetic column and the top core plate is 0.1 to 0.3 mm.

[0014] Preferably, the primary figure-8 winding and the secondary fractional-turn winding are planar windings made of a printed circuit board.

[0015] Preferably, the rectifier tube and the output capacitor are located on the outer side of the top core plate and the core main body, and are not wrapped inside the magnetic core.

[0016] The beneficial effects of the present invention are as follows: 1. The present invention solves the problem that the freewheeling state of the CDR converter cannot work normally caused by the application of magnetic integration and fractional-turn technology to the CDR converter, so that the planar transformer with both inductor-transformer magnetic integration and fractional-turn winding can be applied to the CDR converter, which has significantly improved transformer efficiency and power density compared with the traditional scheme.

[0017] 2. This invention overcomes the limitation and bottleneck that magnetic integration and fractional-turn technologies cannot be simultaneously applied to CDR transformers. Through innovative design of key structures and parameters such as the trapezoidal double-concave waist cross-section side column, core center column, core side column, core shape, and core air gap, it achieves for the first time in a CDR converter transformer an optimized design where the secondary winding uses a half-turn fractional-turn winding, the primary winding uses a figure-eight equal-width winding, and a single core simultaneously integrates both the CDR transformer winding and the CDR inductor winding. This fully leverages the advantages of both magnetic integration technology (low magnetic loss) and fractional-turn technology (low copper loss). Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a planar transformer with trapezoidal double concave waist side pillars for use in a CDR converter according to the present invention; Figure 2 This is a schematic diagram of the bat-shaped 5-core magnetic core of the present invention; Figure 3 This is a top view of the primary side figure-eight winding of the present invention; Figure 4 This is a top view of the secondary fractional-turn winding of the present invention; Figure 5 The circuit diagram of the CDR-type switching power supply of the present invention is shown below. Figure 6 This is a schematic diagram of the air gap arrangement of the magnetic core in this invention; Figure 7 A schematic diagram showing the relationship between the air gap of the circular central column and the circulating current of the secondary winding when different cross-sectional areas are selected for the third magnetic column of the present invention. Figure 8 This is a schematic diagram showing the relationship between the air gap of the circular central column and the maximum magnetic flux density when the third magnetic column of the present invention is selected with different cross-sectional areas. Figure 9 This is a schematic diagram showing the relationship between the air gap of the circular central column and the core loss when different cross-sectional areas are selected for the third magnetic column of the present invention.

[0019] In the diagram, 1. Core top plate; 2. Core body; 3. First magnetic column; 4. Second magnetic column; 5. Third magnetic column; 6. Fourth magnetic column; 7. Fifth magnetic column; 8. Primary side figure-eight winding; 9. First half-turn winding; 10. Second half-turn winding; 11. Third half-turn winding; 12. Fourth half-turn winding; 13. Rectifier tube; 14. Secondary side fractional-turn winding; 15. Output capacitor. Detailed Implementation

[0020] The related technologies of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] like Figures 1-9 As shown, this embodiment of a planar transformer with trapezoidal double-concave waist side posts for CDR converter includes: a magnetic core and windings; the windings include a primary side figure-eight winding 8 and a secondary side fractional-turn winding 14; the magnetic core contains five core posts, and the magnetic core has a bat-shaped structure; the five core posts are respectively a trapezoidal double-concave waist cross-section side post, two circular cross-section center posts, and two rectangular cross-section side posts. The secondary side fractional-turn winding 14 consists of four independent half-turn secondary fractional-turn windings, which, along with the primary side figure-eight winding 8, respectively surround the two central core posts of the magnetic core; the segments of the secondary side fractional-turn winding 14 are connected in series by rectifier tubes 13 and secondary output capacitors 15.

[0022] Furthermore, the magnetic core includes: a magnetic core top plate 1 and a magnetic core body 2. Both the magnetic core top plate 1 and the magnetic core body 2 are bat-shaped flat plates and are parallel to each other. On the magnetic core body 1, from left to right, there are outwardly protruding first magnetic pillars 3, second magnetic pillars 4, third magnetic pillars 5, fourth magnetic pillars 6, and fifth magnetic pillars 7. The first magnetic pillars 3, second magnetic pillars 4, third magnetic pillars 5, fourth magnetic pillars 6, and fifth magnetic pillars 7 are all located on the same side of the magnetic core body 2 and face the magnetic core top plate 1.

[0023] Furthermore, the first magnetic post 3, the fifth magnetic post 7, and the third magnetic post 5 are all tightly connected to the top plate 1 of the magnetic core, with no air gap between them. This minimizes magnetic reluctance, reduces internal circulating current, improves the efficiency of the magnetic components, and reduces core loss.

[0024] Furthermore, by retaining an air gap only between the second magnetic column 4, the fourth magnetic column 6 and the top plate 1 of the magnetic core, an optimal design that balances maximum magnetic flux density and minimum core loss can be achieved.

[0025] Furthermore, the first magnetic post 3, the second magnetic post 4, the fourth magnetic post 6, and the fifth magnetic post 7 are arranged in a straight line on the magnetic core body 2. The third magnetic post 5 is not arranged in a straight line with the other four core posts, but is offset to one side of the two circular cross-section central posts, forming a triangular arrangement with the second magnetic post 4 and the fourth magnetic post 6. This arrangement provides sufficient space for the primary side figure-eight winding 8, ensuring that the width of the primary side figure-eight winding 8 remains consistent, resulting in a relatively uniform primary side current density distribution. At the same time, the third magnetic post 5 is located between the two circular central posts, which can balance the magnetic flux generated by the two circular central posts in the CDR freewheeling state, ensuring normal operation even in the freewheeling state of the CDR converter.

[0026] Furthermore, the primary side figure-eight winding 5 is arranged in a figure-eight pattern around the second magnetic post 4 and the fourth magnetic post 6. The first half-turn winding 9 and the second half-turn winding 10 jointly surround the second magnetic post 4, and the third half-turn winding 11 and the fourth half-turn winding 12 jointly surround the fourth magnetic post 6. This constitutes the structure of the secondary side fractional-turn winding 14, and realizes the magnetic integration of the transformer and the inductor. In the same magnetic component of the CDR converter, both the magnetic integration of the transformer and the inductor and the fractional-turn winding of the secondary side are realized. Therefore, the advantages of low copper loss of fractional-turn windings and the small size of magnetically integrated cores can be utilized.

[0027] Furthermore, the cross-sectional area of ​​the third magnetic pillar 5 is equal to the sum of the areas of the first magnetic pillar 3 and the fifth magnetic pillar 7. This ensures that the core loss is minimized.

[0028] Furthermore, the winding includes a planar winding made using a printed circuit board. The manufacturing process of printed circuit boards is stable and reliable; therefore, planar windings made from printed circuit boards can accurately produce primary and half-turn secondary fractional-turn windings, improving the power density of the entire transformer.

[0029] Furthermore, the secondary fractional-turn windings 14 are electrically connected via rectifier tubes 13 and output capacitors 15; both rectifier tubes 13 and output capacitors 15 are located on the outer side of the core top plate 1 and the core body 2 in the snap-fit ​​direction, and are not enclosed inside the core. This reduces the height of the core and increases the power density of the CDR, while also improving heat dissipation for the semiconductor components, allowing them to carry a larger output current.

[0030] Figure 5 The CDR-type switching power supply shown is one application scenario of this invention.

[0031] In summary, this invention provides a solution for magnetically integrated fractional-turn magnetic circuit flow in the freewheeling mode of the CDR converter by arranging five core columns in a triangular pattern and designing the side and center columns with a trapezoidal double-concave waist cross-section. Even when all primary-side transistors are off and all secondary-side transistors are on, and the secondary-side current flows in the opposite direction (freewheeling mode), the fractional-turn secondary winding still provides a circulating path for the magnetic flux through the trapezoidal double-concave waist cross-section core columns. Therefore, this invention solves the problem of magnetic circuit discontinuity caused by the reverse-flowing fractional-turn secondary winding, enabling the fractional-turn secondary winding scheme to be used in CDR planar transformers, resulting in significant improvements in transformer efficiency and power density compared to traditional schemes.

[0032] It should be emphasized that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A planar transformer with trapezoidal double-concave flanked leg columns for a CDR converter, characterized by, comprises: a magnetic core and windings; the magnetic core comprises a magnetic core top plate (1) and a magnetic core main body (2), and the windings comprise a primary figure-8 winding (8) and a secondary fractional-turn winding (14); on the magnetic core main body (2), a first magnetic column (3), a second magnetic column (4), a third magnetic column (5), a fourth magnetic column (6) and a fifth magnetic column (7) protruding toward the magnetic core top plate (1) are sequentially arranged along the length direction of the magnetic core main body (2), the first magnetic column (3) and the fifth magnetic column (7) are square columns, the second magnetic column (4) and the fourth magnetic column (6) are cylindrical columns, and the third magnetic column (5) is a trapezoidal column with an isosceles trapezoidal cross section; the primary figure-8 winding (8) is in a "8" shape, the secondary fractional-turn winding (14) is formed by splicing four groups of semi-annular first half-turn winding (9), second half-turn winding (10), third half-turn winding (11) and fourth half-turn winding (12) into two annular shapes respectively; two semi-annular ends of the first half-turn winding (9) and the second half-turn winding (10) are electrically connected through a rectifier tube and a secondary capacitor respectively and then connected in series to form one annular shape, and two semi-annular ends of the third half-turn winding (11) and the fourth half-turn winding (12) are electrically connected through a rectifier tube and an output capacitor respectively and then connected in series to form another annular shape; the two rings of the "8" shape of the primary figure-8 winding (8) are respectively wound and sleeved on the second magnetic column (4) and the fourth magnetic column (6), and the annular shape formed by electrically connecting the first half-turn winding (9) and the second half-turn winding (10) and the annular shape formed by electrically connecting the third half-turn winding (11) and the fourth half-turn winding (12) are respectively sleeved on the second magnetic column (4) and the fourth magnetic column (6); the sum of the magnetic flux areas of the first magnetic column (3) and the fifth magnetic column (7) is equal to the magnetic flux area of the third magnetic column (5).

2. A planar transformer with trapezoidal double concave side column for CDR converter according to claim 1, characterized in that, The magnetic core top plate (1) and the bottom plate of the magnetic core main body (2) are both bat-shaped and parallel to each other.

3. A planar transformer with trapezoidal double concave side column for CDR converter according to claim 1, characterized in that, The geometric centers of the first magnetic column (3), the second magnetic column (4), the fourth magnetic column (6) and the fifth magnetic column (7) are located on the same straight line.

4. A planar transformer with trapezoidal double concave side column for CDR converter according to claim 3, characterized in that, The third magnetic column (5), the second magnetic column (4) and the fourth magnetic column (6) are arranged in a Chinese character "pin" shape.

5. A planar transformer with trapezoidal double concave side column for CDR converter according to claim 4, characterized in that, The two waists of the isosceles trapezoid of the third magnetic column (5) face the second magnetic column (4) and the fourth magnetic column (6) respectively.

6. A planar transformer with trapezoidal double concave side column for CDR converter according to claim 5, characterized in that, Arc-shaped grooves are respectively arranged on the two waists of the isosceles trapezoid of the third magnetic column (5).

7. A planar transformer with trapezoidal double concave side column for CDR converter according to claim 1, characterized in that, No air gap is provided at the joints of the first magnetic column (3), the third magnetic column (5) and the fifth magnetic column (7) with the magnetic core top plate (1); air gaps are provided at the joints of the second magnetic column (4) and the fourth magnetic column (6) with the magnetic core top plate (1).

8. A planar transformer with trapezoidal double concave side column for CDR converter according to claim 7, characterized in that, The width of the air gap between the second magnetic column (4) and the magnetic core top plate (1) and between the fourth magnetic column (6) and the magnetic core top plate (1) is 0.1 to 0.3 mm.

9. A planar transformer with trapezoidal double concave side column for CDR converter according to claim 1, characterized in that, The primary figure-8 winding (8) and the secondary fractional-turn winding (14) are planar windings made of printed circuit boards.

10. A planar transformer with trapezoidal double concave side column for CDR converter according to claim 1, characterized in that, The rectifier tubes (13) and the output capacitor (15) are located on the outer side portions of the magnetic core top plate (1) and the magnetic core main body (2), and are not wrapped inside the magnetic core.

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