A butterfly planar transformer with a kinked primary side and an anti-coupled secondary side and a switching power supply

Abstract

The present invention belongs to the technical field of high-frequency planar transformers, and relates to a butterfly-shaped planar transformer with a twisted primary and an anti-coupled secondary, and a switching power supply, comprising: a magnetic core, a winding; the winding comprising a primary winding and a secondary winding; the magnetic core presents a four-core butterfly structure, and the secondary winding and the primary winding respectively surround the two central core columns of the magnetic core; the secondary winding current has the same winding direction around the two middle columns of the magnetic core; the primary winding is positively coupled with one secondary winding and anti-coupled with the other secondary winding; the blocks of the secondary winding are connected in series by a rectifier tube and a secondary capacitor. The present invention solves the problem of magnetic saturation caused by the magnetic flux of the DC bias in the connection part of the transformer, so that the two-core matrix transformer can be applied to switching power supplies and power electronic converters with DC bias, and has a significant improvement in transformer efficiency and power density compared with traditional solutions.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-frequency planar transformers, and relates to a butterfly-shaped planar transformer with a kinked primary side and an anti-coupled secondary side, and a switching power supply. Background Art

[0002] High-frequency planar transformers are isolation and power conversion components used in switching power supplies. Here, planar transformers specifically refer to new transformers with small size and high power density that use PCB windings instead of traditional Litz wire windings. The operating frequencies of these planar transformers range from a few thousand hertz to several megahertz. In the fields of data center power supply, aviation power supply, communication power supply, etc., the power supply is often required to be able to convert higher DC power into lower DC voltage and have a larger output current carrying capacity. Depending on the application field and requirements, switching power supplies will adopt a variety of different topologies, a considerable number of which are with DC bias. For these switching power supply topologies with DC bias, when the output current is so large that a single planar transformer cannot bear it, the traditional solution is to copy the planar transformer used in switching power supplies without DC bias, that is, a matrix planar transformer with a positive-coupled secondary side, such as Figure 8 shown.

[0003] However, while traditional solutions offer a shortcut, they don't truly address the problems currently existing in switching power supplies. Positive coupling between secondary windings causes the DC bias portion of the output current to generate mutually reinforcing magnetic flux, ultimately leading to core saturation and transformer failure. Primary designs adapted for AC operation result in excessively low magnetizing inductance, and the primary windings are long, resulting in high losses.

[0004] Therefore, a transformer is needed that can solve the problem of magnetic saturation caused by the magnetic flux of DC bias in the transformer connection part to solve the above technical problems. Summary of the Invention

[0005] The technical solution adopted by the present invention to solve the technical problem is: a butterfly-shaped planar transformer with a twisted primary and an anti-coupled secondary, comprising: a magnetic core and a winding; the winding comprises a primary winding and a secondary winding; the magnetic core has a four-core butterfly structure, and the secondary winding and the primary winding respectively surround the two central core columns of the magnetic core; the secondary winding current has the same winding direction around the two middle columns of the magnetic core, forming anti-coupling between the secondary windings; the primary winding is positively coupled with one secondary winding and anti-coupled with the other secondary winding, and is used to transmit power to different secondary sides in different switching periods; the blocks of the secondary winding are connected in series by a rectifier tube and a secondary capacitor, which are used to control the secondary current and filter out the AC component respectively.

[0006] Preferably, the magnetic core includes: a magnetic core top plate and a magnetic core body, the magnetic core top plate and the magnetic core body are both butterfly-shaped flat plates and parallel to each other, and the magnetic core body is provided with outwardly protruding left-side column, left-side middle column, right-side middle column, and right-side column of the magnetic core in sequence from left to right, the left-side column, left-side middle column, right-side middle column, and right-side column of the magnetic core are all arranged on the same side of the magnetic core body and facing the magnetic core top plate;

[0007] The left side leg of the core is magnetically connected to the left center leg of the core via the left connecting portion of the core. The right center leg of the core is magnetically connected to the right side leg of the core via the right connecting portion of the core. The left center leg of the core is connected to the right center leg of the core via the center connecting portion of the core. The left and right connecting portions of the core are trapezoidal columns, while the center connecting portion of the core is rectangular columnar, giving the core an overall butterfly shape. The butterfly-shaped core can effectively alleviate the saturation problem of DC bias flux that is transferred to the outside after changing the coupling direction of the secondary winding. When using a counter-coupled secondary winding, the DC bias flux is transferred from the center connecting portion of the core to the outer side legs of the core. Since there are two side legs, this DC bias flux is reduced to half of that of a traditional design. Based on this, the overall core shape of the butterfly design can effectively increase the cross-sectional area of ​​the side legs, further improving the saturation flux of the side legs and effectively preventing core saturation failure.

[0008] More preferably, the primary winding and the secondary winding surround the left center column of the magnetic core and the right center column of the magnetic core respectively.

[0009] More preferably, the primary winding is in an "8-shaped" twisted shape, wrapping around the left and right center columns of the magnetic core in opposite directions, and the center column of the magnetic core connection part is removed; the end length of the primary winding can be greatly shortened to only one-third of the traditional design, reducing the end loss of the planar transformer.

[0010] More preferably, the winding includes a planar winding made of a printed circuit board; the process of the printed circuit board is stable and reliable, so the planar winding made of the printed circuit board can accurately process the winding with a kinked primary side and an anti-coupled secondary side, and can improve the power density of the entire transformer.

[0011] More preferably, the secondary winding is divided into sections surrounding the left and right center legs of the magnetic core, and the sections are electrically connected via rectifiers and output capacitors. The rectifiers and output capacitors are located outside the core's top plate and main body, and are not enclosed within the core. This reduces the height of the core and increases the power density of the switching power supply. It also facilitates heat dissipation of semiconductor components, allowing them to carry greater output current.

[0012] More preferably, the circuit of the primary winding and the secondary winding includes: transistors Q1 to Q4, inductors L1 and L2, and the circuit connection method of the primary winding and the secondary winding is: transistors Q1 and Q2 are connected in series and respectively connected to the input end of the external circuit, the two capacitors are connected in series and respectively connected to the input end of the external circuit, the primary input ends of the inductors L1 and L2 are connected in series and respectively connected to the connection node of the transistors Q1 and Q2 and the connection node of the two capacitors; transistors Q3 and Q4 are connected in series, and the secondary output ends of the inductors L1 and L2 are connected in series and then connected in parallel with each other, the connection node of the secondary output ends of the inductors L1 and L2 and the connection node of the transistors Q3 and Q4 are respectively connected to the output end of the external circuit, the capacitor C and the resistor R ESR After being connected in series, they are respectively connected to the output ends of the external circuit; the primary and secondary windings are connected to the external circuit; the secondary rectifier tube and secondary output capacitor in the external circuit have been integrated into this transformer, and only need to be connected to the secondary output port for normal operation; the primary winding needs to be connected to the primary switching tube and the bus capacitor.

[0013] The present invention further discloses a switching power supply, comprising: a housing and the butterfly-shaped planar transformer with a kinked primary side and an anti-coupled secondary side, wherein the butterfly-shaped planar transformer is arranged in the housing.

[0014] The beneficial effects of the present invention are:

[0015] 1. The present invention solves the problem of magnetic saturation caused by the magnetic flux of DC bias in the transformer connection part, so that the two-core matrix transformer can be used in switching power supplies and power electronic converters with DC bias. Compared with traditional solutions, the transformer efficiency and power density are significantly improved.

[0016] 2. The present invention compresses the length of the primary winding, especially the length of the end lead of the primary winding, thereby reducing the loss of the primary winding without affecting the secondary winding. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is an isometric view of a butterfly-shaped planar transformer and a switching power supply with a kinked primary and an anti-coupled secondary according to the present invention;

[0018] Figure 2 is an isometric view of a butterfly-shaped magnetic core of the present invention;

[0019] Figure 3 is a top view of the secondary winding of the present invention;

[0020] Figure 4 is a top view of the primary winding of the present invention, wherein Figure 4 (a) Figure 4 (b) Top views of the upper and lower primary windings, respectively;

[0021] Figure 5This is a schematic diagram of the current flow direction of the primary winding of the present invention from a top view, wherein Figure 5 (a) Figure 5 (b) Schematic diagram of the current flow direction of the upper and lower primary windings from a top view;

[0022] Figure 6 Schematic diagram of the current flow direction of the secondary winding of the present invention from a top view;

[0023] Figure 7 It is a circuit diagram of a CDR type switching power supply with DC bias according to the present invention;

[0024] Figure 8 It is a diagram of the winding structure of a matrix transformer in the prior art; Figure 8 (a) is the transformer winding structure diagram of the secondary side with same-direction coupling. Figure 8 (b) is the transformer winding structure diagram without a semi-encircled secondary.

[0025] In the figure, 1. top plate of the core; 2. main body of the core; 3. winding; 4. left side column of the core; 5. left connecting part of the core; 6. left middle column of the core; 7. center connecting part of the core; 8. right middle column of the core; 9. right connecting part of the core; 10. right side column of the core; 11. upper layer of the primary winding; 12. left via group of the primary winding; 13. right via group of the primary winding; 14. lower layer of the primary winding; 15. outer part of the left secondary winding; 16. inner part of the left secondary winding; 17. inner part of the right secondary winding; 18. outer part of the right secondary winding; 19. output capacitor of the left secondary winding; 20. rectifier of the left secondary winding; 21. output capacitor of the right secondary winding; 22. rectifier of the right secondary winding. DETAILED DESCRIPTION

[0026] The following will provide a clear and complete description of the relevant technologies in the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0027] refer to Figures 1 to 8This embodiment provides a butterfly-shaped planar transformer with a twisted primary and anti-coupled secondary. The planar transformer consists of a magnetic core, a primary winding, and a secondary winding. The magnetic core has a four-core butterfly structure, with the secondary winding divided into blocks surrounding the two central core blocks of the magnetic core, and the primary winding also surrounding the two central core blocks of the magnetic core. Unlike traditional planar transformers, the secondary winding current has the same winding direction around the two central core blocks, forming anti-coupling between the secondary windings. The primary winding is positively coupled with one secondary winding and anti-coupled with the other secondary winding, and is used to transmit power to different secondary sides in different switching periods. A rectifier tube and a secondary capacitor are connected in series between each block of the secondary winding, which are used to control the secondary current and filter out the AC component, respectively.

[0028] Furthermore, the secondary windings are designed with anti-coupling, while retaining the characteristic of the secondary winding half-surrounding the core's center leg. This anti-coupling not only mitigates the saturation problem caused by DC bias flux at the core connection, but also staggers the energy transfer timing between the two secondary windings, resulting in smoother output power and lower ripple. This maximizes the advantages of the half-surround secondary winding in terms of both length and loss.

[0029] Furthermore, the primary winding is twisted in a figure-eight pattern, wrapping around the two core legs in opposite directions. The center leg at the core connection is removed. This design significantly shortens the primary winding's end length to about one-third of that of conventional designs, significantly reducing the planar transformer's end losses.

[0030] Furthermore, the connection between the two central core legs and the two side legs is trapezoidal, giving the overall core a butterfly shape. This effectively mitigates the saturation problem of the DC bias flux that is transferred to the outer sides after changing the coupling direction of the secondary winding. With the use of an anti-coupled secondary winding, the DC bias flux is transferred from the central connection of the core to the outer side legs. Because there are two side legs, this DC bias flux is reduced to half that of a conventional design. Furthermore, the overall core shape of the butterfly design effectively increases the cross-sectional area of ​​the side legs, further improving the saturation flux of the side legs and effectively preventing core saturation failure.

[0031] Furthermore, the primary and secondary windings are planar windings made of printed circuit boards. The printed circuit board process is stable and reliable, and can accurately produce windings with twisted primary and anti-coupled secondary windings, thereby improving the power density of the entire transformer.

[0032] Furthermore, the rectifier and output capacitor are located outside the butterfly core, rather than enclosed within it. This reduces the core height and increases the power density of the switching power supply. It also facilitates heat dissipation of the semiconductor components, allowing them to carry higher output currents.

[0033] Furthermore, the original secondary winding is Figure 7 The circuit diagram shown connects to the external circuit. The secondary rectifier and secondary output capacitor in the external circuit are already integrated into this transformer, requiring only connection to the secondary output port for normal operation. The primary winding requires connection to the primary switching transistor and bus capacitor.

[0034] It is important to emphasize that: Figure 7 The CDR switching power supply shown is only one application scenario of the present invention. The present invention can also be applied to other CDR power electronic converters, or flyback switching power supplies with two or more phases, or flyback power electronic converters, and other similar switching power supplies or power electronic converters with DC bias.

[0035] In summary, the present invention sets the magnetic core into a butterfly shape and a four-core column structure arranged in the same direction, and the secondary winding current winds around the two middle columns of the magnetic core in the same direction, thereby forming reverse coupling between the secondary windings; the primary winding is positively coupled with one secondary winding and reversely coupled with the other secondary winding, and is used to transmit power to different secondary sides in different switching periods; the blocks of the secondary winding are connected in series by a rectifier tube and a secondary capacitor, which are used to control the secondary current and filter out the AC component, respectively; therefore, the present invention solves the problem of magnetic saturation caused by the magnetic flux of the DC bias in the connection part of the transformer, so that the two-core column matrix transformer can be used in switching power supplies and power electronic converters with DC bias, and has significant improvements in transformer efficiency and power density compared to traditional solutions.

[0036] It should be emphasized that the above are only preferred embodiments of the present invention and do not limit the present invention in any form. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A butterfly-type planar transformer with a kinked primary and an anti-coupled secondary, characterized in that: include: A magnetic core and a winding (3); the winding (3) includes a primary winding and a secondary winding; the magnetic core is in a four-core butterfly structure, the secondary winding and the primary winding respectively surround the two central core columns of the magnetic core; the secondary winding current has the same winding direction around the two central columns of the magnetic core; the primary winding is positively coupled with one secondary winding, and the primary winding is reversely coupled with the other secondary winding; the blocks of the secondary winding are connected in series by a rectifier tube and an output capacitor, and the secondary winding blocks surround the left central column (6) and the right central column (8) of the magnetic core; The magnetic core comprises: a magnetic core top plate (1) and a magnetic core body (2); the magnetic core top plate (1) and the magnetic core body (2) are both butterfly-shaped flat plates and are parallel to each other; the magnetic core body (2) is provided with a left side column (4) of the magnetic core, a left middle column (6) of the magnetic core, a right middle column (8) of the magnetic core, and a right side column (10) of the magnetic core that are protruding outwards in sequence from left to right; the left side column (4) of the magnetic core, the left middle column (6) of the magnetic core, the right middle column (8) of the magnetic core, and the right side column (10) of the magnetic core are all arranged on the same side of the magnetic core body (2) and face the magnetic core top plate (1); The left side column (4) of the magnetic core is magnetically connected to the left middle column (6) of the magnetic core via the left side connection portion (5), the right middle column (8) of the magnetic core is magnetically connected to the right side column (10) of the magnetic core via the right side connection portion (9), and the left middle column (6) of the magnetic core is connected to the right middle column (8) of the magnetic core via the center connection portion (7), the left side connection portion (5) and the right side connection portion (9) of the magnetic core are respectively in the shape of a trapezoidal column, and the center connection portion (7) of the magnetic core is in the shape of a rectangular column; The primary winding is in an "8" kinked shape, and the primary winding surrounds the left middle column (6) of the magnetic core and the right middle column (8) of the magnetic core in opposite directions.

2. A butterfly-type planar transformer with a kinked primary and an anti-coupled secondary according to claim 1, characterized in that: The winding (3) comprises a planar winding made of a printed circuit board.

3. The butterfly-shaped planar transformer with a kinked primary and an anti-coupled secondary according to claim 1, characterized in that: The rectifier tube and the output capacitor are both located on the outer side of the magnetic core top plate (1) and the magnetic core body (2) in the direction of engagement, and are not wrapped inside the magnetic core.

4. A butterfly-type planar transformer with a kinked primary and an anti-coupled secondary according to claim 1, characterized in that: The circuit of the primary winding and the secondary winding includes: transistors Q1 to Q4, inductors L1 and L2, and the circuit connection method of the primary winding and the secondary winding is: transistors Q1 and Q2 are connected in series and respectively connected to the input end of the external circuit, the two capacitors are connected in series and respectively connected to the input end of the external circuit, the primary input ends of the inductors L1 and L2 are connected in series and respectively connected to the connection node of the transistors Q1 and Q2 and the connection node of the two capacitors; transistors Q3 and Q4 are connected in series, and the secondary output ends of the inductors L1 and L2 are connected in series and then connected in parallel with each other, the connection node of the secondary output ends of the inductors L1 and L2 and the connection node of the transistors Q3 and Q4 are respectively connected to the output end of the external circuit, the capacitor C and the resistor R ESR After being connected in series, they are respectively connected to the output ends of the external circuit.

5. A switching power supply, characterized in that: include: A shell and a butterfly-shaped planar transformer with a kinked primary and an anti-coupled secondary as claimed in any one of claims 1 to 4, wherein the butterfly-shaped planar transformer is arranged in the shell.

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