Butterfly planar transformer with twisted primary side and anti-coupling secondary side and switching power supply

Abstract

The invention belongs to the technical field of high-frequency planar transformers, and relates to a butterfly-shaped planar transformer with a twisted primary side and an anti-coupling secondary side and a switching power supply. The winding comprises a primary winding and a secondary winding; the magnetic core is of a four-core-column butterfly-shaped structure, and the secondary winding and the primary winding respectively surround two core columns in the center of the magnetic core; the winding directions of the secondary winding current around the two middle columns of the magnetic core are the same; the primary winding is positively coupled with one secondary winding and reversely coupled with the other secondary winding; according to the two-core-column matrix type transformer, the problem that magnetic saturation is caused by the magnetic flux of direct-current magnetic bias at the connecting part of the transformer is solved, so that the two-core-column matrix type transformer can be applied to a switching power supply with direct-current magnetic bias and a power electronic converter; compared with a traditional scheme, the efficiency and the power density of the transformer are remarkably improved.

Description

Technical Field

[0001] The 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 supplies, aviation power supplies, and communications power supplies, 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 positively coupled secondary side, such as Figure 8 shown.

[0003] However, although the traditional solution provides a shortcut, it does not really solve the problems existing in current switching power supplies. The positive coupling between the secondary windings will cause the DC bias part of the output current to produce mutually reinforcing magnetic flux, which will eventually lead to core saturation and transformer failure. The primary side design adapted to AC makes the excitation inductance too small, and the length of the primary winding is long, resulting in large losses.

[0004] Therefore, a transformer is needed to solve the above technical problems by which the magnetic flux of DC bias magnetism can cause magnetic saturation in the connection part of the transformer. Summary of the invention

[0005] The technical solution adopted by the present invention to solve the technical problem is: a butterfly planar transformer with a twisted primary and an anti-coupled secondary, comprising: a magnetic core, a winding; the winding comprises a primary winding and a secondary winding; the magnetic core is 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 respectively used to control the secondary current and filter out the AC component.

[0006] Preferably, the magnetic core comprises: 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 are parallel to each other, and the magnetic core body is provided with outwardly protruding left-side magnetic core pillars, left-side magnetic core middle pillars, right-side magnetic core middle pillars, and right-side magnetic core pillars in sequence from left to right, and the left-side magnetic core pillars, left-side magnetic core middle pillars, right-side magnetic core middle pillars, and right-side magnetic core pillars are all arranged on the same side of the magnetic core body and facing the magnetic core top plate;

[0007] The left side column of the magnetic core is magnetically connected to the left middle column of the magnetic core through the left connection part of the magnetic core, the right middle column of the magnetic core is magnetically connected to the right side column of the magnetic core through the right connection part of the magnetic core, and the left middle column of the magnetic core is connected to the right middle column of the magnetic core through the center connection part of the magnetic core. The left connection part of the magnetic core and the right connection part of the magnetic core are respectively in the shape of trapezoidal columns, and the center connection part of the magnetic core is in the shape of a rectangular column; so that the magnetic core is butterfly-shaped as a whole; the butterfly-shaped magnetic core can effectively alleviate the problem of DC bias flux saturation transferred to the outside after changing the coupling direction of the secondary winding; after adopting the anti-coupling secondary winding, the DC bias flux will be transferred from the connection part in the center of the magnetic core to the side column outside the magnetic core. Since there are two side columns, this part of the DC bias flux will be reduced to half of the traditional design. On this basis, the overall magnetic core shape of the butterfly design can effectively increase the cross-sectional area of ​​the side column, further increase the saturation flux of the side column, and effectively avoid core saturation failure.

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

[0009] More preferably, the primary winding is in an "8" twisted shape, wrapping around the left and right middle columns of the magnetic core in reverse, and the middle 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 and an anti-coupled secondary, and can improve the power density of the entire transformer.

[0011] More preferably, the secondary winding is divided into blocks that surround the left and right middle columns of the magnetic core, and the surrounding blocks of the secondary winding are electrically connected through the rectifier tube and the output capacitor; the rectifier tube and the output capacitor are both located on the outer side of the buckling direction of the magnetic core top plate and the magnetic core body, and are not wrapped inside the magnetic core; the rectifier tube and the output capacitor are located outside the butterfly-shaped magnetic core, and are not wrapped inside the magnetic core. On the one hand, the height of the magnetic core can be reduced and the power density of the switching power supply can be improved. On the other hand, it is beneficial to the heat dissipation of the semiconductor components, allowing them to carry a larger output current.

[0012] Preferably, the circuit of the primary winding and the secondary winding comprises: transistors Q1 to Q4, inductors L1 and L2, and the circuit connection mode of the primary winding and the secondary winding is: the transistors Q1 and Q2 are connected in series and are respectively connected to the input end of the external circuit, the two capacitors are connected in series and are 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 are respectively connected to the connection nodes of the transistors Q1 and Q2 and the connection nodes of the two capacitors; the transistors Q3 and Q4 are connected in series, the secondary output ends of the inductors L1 and L2 are connected in series and are then connected in parallel with each other, the connection nodes of the secondary output ends of the inductors L1 and L2 and the connection nodes 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 the secondary output port needs to be connected to operate normally; the primary winding needs to be connected to the primary switch tube and the bus capacitor.

[0013] The invention also discloses a switching power supply, comprising: a housing and the above-mentioned 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 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. 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, and reduces 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 side and an anti-coupled secondary side 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 5Schematic diagram of the current flow direction of the primary winding of the present invention from top view, wherein Figure 5 (a) Figure 5 (b) The top view of the current flow direction of the upper and lower primary windings, respectively;

[0022] Figure 6 is a 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 a DC bias according to the present invention;

[0024] Figure 8 It is a structural diagram of a matrix transformer winding in the prior art; Figure 8 (a) is the transformer winding structure diagram of the same-direction coupled secondary side. 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 primary winding; 12. left via group of primary winding; 13. right via group of primary winding; 14. lower layer of primary winding; 15. outer part of left secondary winding; 16. inner part of left secondary winding; 17. inner part of right secondary winding; 18. outer part of right secondary winding; 19. output capacitor of left secondary winding; 20. rectifier of left secondary winding; 21. output capacitor of right secondary winding; 22. rectifier of right secondary winding. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the relevant technologies in the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] refer to Figures 1 to 8In this embodiment, a butterfly planar transformer with a twisted primary and an anti-coupled secondary is provided. The planar transformer is composed of a magnetic core, a primary winding and a secondary winding. The magnetic core presents a four-core butterfly structure. The secondary winding is divided into blocks and surrounds the two core columns in the center of the magnetic core, and the primary winding surrounds the two core columns in the center of the magnetic core at the same time. Unlike the traditional planar transformer, the secondary winding current has the same winding direction around the two middle columns of the magnetic core, forming an anti-coupling between the secondary windings. The primary winding is positively coupled with one secondary winding and anti-coupled with the other secondary winding, so as to transmit power to different secondary sides in different switching periods. Rectifier tubes and secondary capacitors are connected in series between each block of the secondary winding, which are respectively used to control the secondary current and filter out the AC component.

[0028] Furthermore, the secondary windings are designed in an anti-coupling manner, while retaining the characteristic of the secondary winding half-surrounding the core column. On the one hand, anti-coupling can solve the saturation problem caused by the magnetic flux of the DC bias magnetization in the core connection part, and on the other hand, it can stagger the timing of energy transmission of the two sets of secondary windings, making the output power smoother and the ripple smaller. On this basis, the advantages of the secondary winding length and the secondary winding loss brought by the secondary winding half-surrounding can be retained to the greatest extent.

[0029] Furthermore, the primary winding is in an "8-shaped" twisted shape, wrapping around the two core columns in reverse, and the middle column of the core connection part is removed. This design can greatly shorten the end length of the primary winding to only about one-third of the traditional design, greatly reducing the end loss of the planar transformer.

[0030] Furthermore, the connection between the two core columns in the center of the core and the two side columns is trapezoidal, and the overall core is butterfly-shaped. This can effectively alleviate the problem of DC bias flux saturation that is transferred to the outside after changing the coupling direction of the secondary winding. After adopting the reverse-coupled secondary winding, the DC bias flux will be transferred from the connection part in the center of the core to the side column outside the core. Since there are two side columns, this part of the DC bias flux will be reduced to half of the traditional design. On this basis, the overall core shape of the butterfly design can effectively increase the cross-sectional area of ​​the side column, further increase the saturation flux of the side column, and effectively avoid 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 process the windings of the kinked primary and the anti-coupled secondary, and can improve the power density of the entire transformer.

[0032] Furthermore, the rectifier tube and the output capacitor are located outside the butterfly core, and are not wrapped inside the core. On the one hand, the height of the core can be reduced and the power density of the switching power supply can be improved. On the other hand, it is beneficial to the heat dissipation of the semiconductor components, allowing them to carry a larger output current.

[0033] Furthermore, the original secondary winding is Figure 7 The circuit diagram shown is connected to the external circuit. The secondary rectifier and secondary output capacitor in the external circuit have been integrated into this transformer, and only the secondary output port needs to be connected to operate normally. The primary winding needs to be connected to the primary switch tube and the bus capacitor.

[0034] It is important to emphasize that: Figure 7 The CDR type switching power supply shown is only one application scenario of the present invention. The present invention can also be applied to other CDR type power electronic converters, or flyback type switching power supplies with more than two phases, or flyback type 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 to 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 anti-coupling between the secondary windings; the primary winding is positively coupled with one secondary winding and anti-coupled with the other secondary winding, so as 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 respectively used to control the secondary current and filter out the AC component; therefore, the present invention solves the problem of magnetic saturation caused by the magnetic flux of the DC bias in the connecting part of the transformer, so that the two-core column matrix transformer can be applied to switching power supplies and power electronic converters with DC bias, and compared with the traditional scheme, the transformer efficiency and power density are significantly improved.

[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-shaped 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) comprises 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 another secondary winding; each block of the secondary winding is connected in series by a rectifier tube and a secondary capacitor.

2. A butterfly-shaped planar transformer with a kinked primary and an anti-coupled secondary according to claim 1, characterized in that: 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), a left middle column (6), a right middle column (8) and a right side column (10) protruding outwards in sequence from left to right; the left side column (4), the left middle column (6), the right middle column (8) and the right side column (10) 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 a 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 a 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 a center connection portion (7), the left side connection portion (5) of the magnetic core 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.

3. A butterfly-shaped planar transformer with a kinked primary and an anti-coupled secondary according to claim 2, characterized in that: The primary winding and the secondary winding surround the left middle column (6) of the magnetic core and the right middle column (8) of the magnetic core respectively.

4. A butterfly-shaped planar transformer with a kinked primary and an anti-coupled secondary according to claim 2, characterized in that: The primary winding is in a 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 reverse direction.

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

6. A butterfly-type planar transformer with a kinked primary and an anti-coupled secondary according to claim 2, characterized in that: The secondary winding is divided into blocks surrounding the left middle column (6) of the magnetic core and the right middle column (8) of the magnetic core, and the surrounding blocks of the secondary winding are electrically connected through a rectifier tube and an output capacitor; the rectifier tube and the output capacitor are both located on the outer side of the buckling direction of the magnetic core top plate (1) and the magnetic core body (2), and are not wrapped inside the magnetic core.

7. A butterfly-shaped planar transformer with a kinked primary and an anti-coupled secondary according to claim 2, 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 mode of the primary winding and the secondary winding is: the transistors Q1 and Q2 are connected in series and are respectively connected to the input end of the external circuit, the two capacitors are connected in series and are 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 are respectively connected to the connection nodes of the transistors Q1 and Q2 and the connection nodes of the two capacitors; the transistors Q3 and Q4 are connected in series, and the secondary output ends of the inductors L1 and L2 are connected in series and are connected in parallel with each other, the connection nodes of the secondary output ends of the inductors L1 and L2 and the connection nodes 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.

8. 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 7, wherein the butterfly-shaped planar transformer is arranged in the shell.

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