Planar transformer with trapezoidal double-concave-waist side columns for CDR converter

Abstract

The invention belongs to the technical field of high-frequency planar transformers, and relates to a planar transformer with trapezoidal double-concave waist side columns for a CDR converter, which comprises a primary side 8-shaped winding, a secondary side 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 positioned on the outer side between the two circular middle columns, and forms a triangular layout with the circular core column; the primary side 8-shaped winding is wound around the two circular core columns in an 8-shaped manner in the anticlockwise direction; the secondary side fractional-turn winding is composed of four independent half-turn windings which are wound around the two rectangular side columns and the two circular middle columns respectively. According to the invention, the problem that the transformer of the CDR topology simultaneously realizes the inductance magnetic integration and the winding fractional turn is solved, so that the converter of the CDR topology can still consider the advantages of the magnetic integration and the fractional turn in a follow current state, and the loss of the whole machine is obviously reduced.

Description

A planar transformer with trapezoidal double concave waist-side pillars for CDR converters 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 figure-eight shape of the primary side figure-eight winding are respectively wound and sleeved on the second magnetic column and the fourth magnetic column. The rings formed after the first half-turn winding and the second half-turn winding are electrically connected, and the rings formed after the third half-turn winding and the fourth half-turn winding are electrically connected 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 magnetic core top plate and the bottom plate of the magnetic core 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 "pin" shape.

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

[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 docking positions of the first magnetic column, the third magnetic column, and the fifth magnetic column with the magnetic core top plate; air gaps are provided at the docking positions of the second magnetic column and the fourth magnetic column with the magnetic core top plate.

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

[0014] Preferably, the primary side figure-eight winding and the secondary side fractional-turn winding are planar windings made of printed circuit boards.

[0015] Preferably, the rectifying diodes and the output capacitors are located on the outer sides of the magnetic core top plate and the magnetic core 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 CDR converter cannot work properly in the freewheeling state caused by the application of magnetic integration and fractional-turn technology to the CDR converter, enabling the planar transformer with both inductive transformer magnetic integration and fractional-turn windings to be applied to the CDR converter, and there are significant improvements in the 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 is a schematic diagram of a planar transformer with trapezoidal double concave waist side pillars for a CDR converter according to the present invention; Figure 2 is a schematic diagram of a bat-shaped 5-core magnetic core according to the present invention; Figure 3 is a top view of the primary side figure-eight winding according to the present invention; Figure 4 is a top view of the secondary side fractional-turn winding according to the present invention; Figure 5 is a circuit diagram of the CDR type switching power supply according to the present invention; Figure 6 is a schematic diagram of the air gap arrangement of the magnetic core according to the present invention; Figure 7 is a schematic diagram of the relationship between the air gap of the circular middle pillar and the circulating current of the secondary winding when the third magnetic pillar of the present invention is selected with different cross-sectional areas; Figure 8 is a schematic diagram of the relationship between the air gap of the circular middle pillar and the maximum magnetic flux density when the third magnetic pillar of the present invention is selected with different cross-sectional areas; Figure 9 is a schematic diagram of the relationship between the air gap of the circular middle pillar and the magnetic core loss when the third magnetic pillar of the present invention is selected with different cross-sectional areas.

[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] As shown in Figures 1-9, a planar transformer with trapezoidal double-concave waist side posts for CDR converter according to this embodiment 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, 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] The CDR-type switching power supply shown in Figure 5 is one application scenario of the present 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 waist-side pillars for use in a CDR converter, characterized in that, Including: A magnetic core and windings; the magnetic core includes a magnetic core top plate (1) and a magnetic core body (2), and the windings include a primary side figure-eight winding (8) and a secondary side fractional-turn winding (14); on the magnetic core body (2), along the length direction of the magnetic core 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) that protrude towards the magnetic core top plate (1) are sequentially arranged. 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 trapezoid cross-section; the primary side figure-eight winding (8) is in the shape of an "8", and the secondary side fractional-turn winding (14) is composed of four groups of semi-annular first half-turn windings (9), second half-turn windings (10), third half-turn windings (11), and fourth half-turn windings (12) respectively spliced into two rings; the two ends of the semi-annular shapes of the first half-turn winding (9) and the second half-turn winding (10) are respectively electrically connected through rectifier tubes and secondary side capacitors and then connected in series to form a ring, and the two ends of the semi-annular shapes of the third half-turn winding (11) and the fourth half-turn winding (12) are respectively electrically connected through rectifier tubes and secondary side capacitors and then connected in series to form a ring; the two rings of the "8" shape of the primary side figure-eight winding (8) are respectively wound and sleeved on the second magnetic column (4) and the fourth magnetic column (6), and the rings formed after the first half-turn winding (9) and the second half-turn winding (10) are electrically connected, and the rings formed after the third half-turn winding (11) and the fourth half-turn winding (12) are electrically connected 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 waist-side pillars for a CDR converter according to claim 1, characterized in that, Both the magnetic core top plate (1) and the bottom plate of the magnetic core body (2) are in the shape of a bat and are parallel to each other.

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

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

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

7. A planar transformer with trapezoidal double concave waist-side pillars for a CDR converter according to claim 1, characterized in that, No air gap is provided at the docking 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); an air gap is provided at the docking 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 waist-side pillars for a CDR converter according to claim 7, characterized in that, The width of the air gap between the second magnetic column (4), the fourth magnetic column (6) and the magnetic core top plate (1) is 0.1 - 0.3 mm.

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

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

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