Fractional turn planar transformer with matrix type integrated structure and converter

Abstract

The invention belongs to the technical field of planar transformers, and relates to a fractional-turn planar transformer of a matrix type integrated structure and a converter. Comprising M magnetic cores and a PCB (printed circuit board), and each magnetic core is provided with a plurality of layers of primary windings and N sections of secondary windings; a circuit structure is arranged between the secondary winding on the first surface and the secondary winding on the second surface, and a source electrode of a synchronous rectifier tube in the circuit structure is connected with a grounding end of an output capacitor; positive potential ends, back to two output capacitors in the circuit structure, on the first surface and the second surface are connected; according to the planar transformer, the advantages of the fractional turn scheme and the matrix scheme of the existing planar transformer are combined, the defects of the fractional turn scheme and the matrix scheme are suppressed, and the requirements of the market for the high-transformation-ratio transformer on the higher server power supply bus voltage are met.

Description

Technical Field

[0001] This invention belongs to the field of planar transformer technology, and relates to a fractional-turn planar transformer and converter with a matrix integrated structure. Background Technology

[0002] A planar transformer is a high-frequency transformer with a special planar structure design. It is formed by directly etching the windings onto a printed circuit board (PCB) and combining them with a planar magnetic core. Planar transformers have advantages such as a flat structure, high operating frequency, low leakage inductance, high efficiency, and high power density. Planar transformers represent a significant direction in the development of electronic transformers, and due to their unique planar structure and excellent electrical performance, they have been widely used in consumer electronics, automotive electronics, medical equipment, and industrial control. Existing planar transformer solutions are mainly divided into matrix planar transformer solutions and fractional-turn planar transformer solutions.

[0003] For the matrix planar transformer solution, a smaller magnetic component volume is achieved through flux cancellation and magnetic component integration, thereby achieving a higher power density. However, because the secondary winding needs to completely bypass one of the magnetic pillars, a large secondary winding loss is introduced, resulting in significant losses in low-voltage, high-current scenarios.

[0004] For fractional-turn planar transformer schemes, although the length of the current loop is reduced by optimizing the winding configuration, the lack of flux cancellation and magnetic component integration results in a large magnetic component volume. Therefore, the size of the transformer itself limits the compromises in iron loss and power density of this scheme, as exemplified by invention CN115223782B.

[0005] Therefore, a method or structure is needed to solve the above problems by achieving magnetic flux cancellation, reducing transformer size, reducing iron loss, and increasing power density. Summary of the Invention

[0006] The technical solution adopted by the present invention to solve the technical problem is: a matrix integrated structure fractional-turn planar transformer, including: a magnetic core and a PCB board. The magnetic core is provided with M layers, and each magnetic core is provided with a number of primary winding layers and N secondary winding segments, wherein 2≤M≤20 and 2≤N≤6.

[0007] The magnetic core includes edge magnetic pillars, a central magnetic pillar, and a magnetic top cover. The edge magnetic pillars and the central magnetic pillar penetrate the PCB board respectively. The edge magnetic pillars surround the central magnetic pillar along the plane of the PCB board, and the edge magnetic pillars and the central magnetic pillar form a drawing space for drawing the winding.

[0008] The winding includes a primary winding drawn inside the PCB board and a secondary winding drawn on the first and second surfaces of the PCB board. The primary winding is drawn on the central magnetic post in accordance with the current direction, and the primary windings of adjacent layers are arranged at intervals. The secondary windings on the first surface and the secondary windings on the second surface are drawn symmetrically, and the secondary windings on the first surface and the secondary windings on the second surface are both distributed circumferentially around the central magnetic post.

[0009] A circuit structure is provided between the secondary windings on the first surface and the secondary windings on the second surface. Each circuit structure includes an output capacitor and a synchronous rectifier. The source of the synchronous rectifier is connected to the ground terminal of the output capacitor. The positive potential terminals of the two output capacitors in the circuit structures on the first and second surfaces are connected. On the first surface, the drain of the synchronous rectifier is connected to the same-name terminal of an adjacent secondary winding segment, and the positive potential terminal of the output capacitor is connected to the opposite-name terminal of another adjacent secondary winding segment. On the second surface, the drain of the synchronous rectifier is connected to the opposite-name terminal of an adjacent secondary winding segment, and the positive potential terminal of the output capacitor is connected to the same-name terminal of another adjacent secondary winding segment.

[0010] Preferably, the first surface and the second surface are the front and back sides of the PCB board, respectively.

[0011] Preferably, the magnetic core has a line lead-out at the edge of the PCB board, and a magnetic component top cover hole is provided inside the PCB board. The line lead-out and the magnetic component top cover hole are used for the power lead-out wiring of the output capacitor.

[0012] Preferably, the output capacitor and synchronous rectifier are fixed to the PCB board by surface mount soldering.

[0013] Preferably, the positive potential terminal of the output capacitor on the first surface is connected to the positive potential terminal of the output capacitor on the second surface via a circuit; the source of the synchronous rectifier is connected to the ground terminal of the output capacitor and then grounded.

[0014] Preferably, the primary winding is connected to an LLC resonant circuit.

[0015] Preferably, 4≤M≤12, 3≤N≤4.

[0016] Preferably, the primary winding connects M central magnetic columns in series according to the winding method of adjacent magnetic columns with opposite current flow directions, and the secondary winding surrounds each central magnetic column and is divided into 2N segments.

[0017] Even better, the 2N sets of output capacitors and synchronous rectifier tubes surrounding the M central magnetic pillars are respectively set at the junction of the secondary windings of the 2N segments.

[0018] The present invention also discloses a converter comprising the fractional-turn planar transformer of the matrix integrated structure described above.

[0019] The beneficial effects of this invention are:

[0020] 1. This invention achieves flux cancellation and integration by improving the transformer structure and combining it with the winding of the primary side high-voltage, low-current winding. The secondary winding of the transformer adopts a fractional-turn scheme, dividing it into 2N segments according to the transformation ratio, and placing an output capacitor and synchronous rectifier tube at the junction of each segment to reduce the line length and impedance of the secondary winding. Therefore, this invention can achieve flux cancellation in the magnetic components by changing the low-current path, thus achieving magnetic integration and increasing power density; it also reduces the current path of the high-current secondary side, improving efficiency; and by combining the fractional-turn and matrix schemes, it improves the transformer gain, achieving high gain for a single transformer, and simultaneously achieving high gain, high efficiency, and high power density.

[0021] 2. This invention combines the advantages of existing planar transformer fractional-turn schemes and matrix schemes while suppressing their disadvantages, thus meeting the market demand for high-ratio transformers as server power supply bus voltages become increasingly higher. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of a matrix integrated fractional-turn planar transformer and converter according to the present invention;

[0023] Figure 2 This is a specific layout diagram of the transformer of the present invention in a four-layer PCB, wherein (a) is the layout of the secondary winding and devices on the first surface of the PCB, (b) is the layout of the primary winding on the middle layer 1 of the PCB, (c) is the layout of the primary winding on the middle layer 2 of the PCB, and (d) is the layout of the secondary winding and devices on the second surface of the PCB.

[0024] Figure 3 This is a schematic diagram of the equivalent circuit and integrated structure of the transformer during the positive half-cycle of the present invention, wherein (a) is the schematic diagram of the equivalent circuit under this working state, (b) is a schematic diagram of the current flow direction on the first surface of the PCB, and (c) indicates that no current flows through the secondary winding on the second surface of the PCB.

[0025] Figure 4 This is a schematic diagram of the equivalent circuit and integrated structure of the transformer in the negative half-cycle of the present invention, wherein (a) is the schematic diagram of the equivalent circuit in this working state, (b) indicates that no current flows through the secondary winding on the first surface of the PCB, and (c) is a schematic diagram of the current flow direction on the second surface of the PCB.

[0026] Figure 5 This is a schematic diagram illustrating the introduction of the transformer switching transistor drive in this invention;

[0027] Figure 6This is a graph showing the relationship between the transformer magnetic flux density B(t) and the output voltage of the present invention;

[0028] Figure 7 This is a schematic diagram of a transformer based on the present invention, which combines fractional turns with different numbers of turns and a matrix of different magnetic columns.

[0029] In the diagram, 1 is the magnetic core; 101 is the edge magnetic column; 102 is the center magnetic column; 103 is the top cover of the magnetic component; 104 is the hole in the top cover of the magnetic component; 2 is the PCB board; 3 is the line lead-out; 4 is the output capacitor; 5 is the synchronous rectifier tube; 6 is the current direction; 7 is the primary winding; and 8 is the secondary winding. Detailed Implementation

[0030] The relevant technologies of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0031] refer to Figures 1-7 This implementation combines the traditional fractional-turn scheme and the matrix scheme, integrating the fractional-turn scheme of the N-segment secondary winding with the matrix scheme of the M-pillar. Figure 1 and Figure 2 As shown, at this time N=3, M=4. The high-ratio planar transformer of this embodiment includes a magnetic core 1 and a PCB board 2. The magnetic core 1 includes an edge magnetic post 101, a central magnetic post 102, a magnetic component top cover 103, and a hole 104 in the magnetic component top cover. The edge magnetic post 101 and the central magnetic post 102 penetrate the PCB board 2, and the edge magnetic post 101 and the central magnetic post 102 form the drawing space for the winding. Figure 2 As shown in (b) and (c), the winding includes several layers of primary windings 7 drawn inside the PCB board 2. Adjacent layers of primary windings 7 are arranged at intervals and wound on M central magnetic pillars 102 according to a specific current direction, where M is a natural number not less than 2. The primary windings 7 are connected to the resonant cavity of the LLC. Figure 2 As shown in (a) and (d) above, the winding also includes N secondary windings 8 drawn on the first and second surfaces of the PCB board 2, where N is a natural number not less than 2. The N secondary windings 8 on the first and second surfaces of the PCB board 2 are symmetrically wound, and both the N secondary windings 8 on the first and second surfaces of the PCB board 2 are circumferentially distributed around the central magnetic post 102. In this embodiment, the first surface of the PCB board 2 is either the front or back surface of the PCB board 2. When the first surface is the front surface of the PCB board 2, the second surface is the back surface of the PCB board 2; when the first surface is the front surface of the PCB board 2, the second surface is the back surface of the PCB board 2.

[0032] like Figure 1 and Figure 2 As shown, circuit structures are provided between adjacent secondary windings 8 on the first surface and between adjacent secondary windings 8 on the second surface of PCB board 2. Each circuit structure includes an output capacitor 4 and a synchronous rectifier 5. The source of the synchronous rectifier 5 is connected to the ground terminal of the output capacitor 4. The positive potential terminals of the two capacitors 4 in the circuit structures on the first and second surfaces of PCB board 2 are connected. On the first surface of PCB board 2, the drain of the synchronous rectifier 5 in each circuit structure is connected to the same-name terminal of the adjacent secondary winding 8, and the positive potential terminal of the output capacitor 4 in each circuit structure is connected to the opposite-name terminal of the adjacent secondary winding 8. On the second surface of PCB board 2, the drain of the synchronous rectifier 5 in each circuit structure is connected to the opposite-name terminal of the adjacent secondary winding 8, and the positive potential terminal of the output capacitor 4 in each circuit structure is connected to the same-name terminal of the adjacent secondary winding 8.

[0033] like Figure 1 and Figure 2 As shown, the output capacitor 4 located at the edge is led out from the line lead-out port 3 directly through the gap between the edge magnetic pillars 101 in accordance with the power lead-out direction of the primary winding 7. The output capacitor 4 located in the center magnetic pillar 102 is led out from the hole 104 in the top cover of the magnetic component in accordance with the power lead-out direction of the secondary winding 8.

[0034] In this embodiment, the output capacitor 4 and the synchronous rectifier tube 5 are fixed to the PCB board 2 by surface mount soldering. The positive potential terminal of the output capacitor 4 in the circuit structure on the first and second surfaces of the PCB board 2 is connected through PCB traces. The source of the synchronous rectifier tube 5 is grounded after being connected to the ground terminal of the output capacitor 4.

[0035] To provide a more detailed explanation of the high-ratio planar transformer of the present invention, this embodiment uses a full-wave rectified LLC circuit as an example, wherein the integrated structure is as follows: Figure 1As shown, this method uses a transformer configuration of M=4 and N=3, integrating four fractional-turn transformers with three side columns into a four-column matrix transformer, resulting in a high-ratio transformer with a total turns ratio of M*N=12. The primary winding 7 is wound around the four central columns 102 in the direction of current 6, between the edge columns 101 and the central columns 102. The secondary winding 8 is divided into four groups, each group consisting of three segments, wound around the central column 102. The secondary winding 8 is wound between the central column 102 and adjacent central columns 102, and between the edge columns 101 and the central column 102. Twelve output capacitors 4 and twelve synchronous rectifier diodes 5 are divided into four groups, each group consisting of three output capacitors 4 and three synchronous rectifier diodes 5. The negative voltage terminal of output capacitor 4 is connected to the source of synchronous rectifier diode 5, and the positive voltage terminal of output capacitor 4 is connected to the opposite terminal of the adjacent secondary winding 8. The drain of synchronous rectifier diode 5 is connected to the same terminal of the adjacent secondary winding 8. All positive and negative voltage terminals of output capacitors 4 on the first and second surfaces of PCB board 2 are connected via vias. In the four-layer PCB structure, the specific layout of the transformer primary and secondary windings, output capacitor 6, and synchronous rectifier diode 5 is as follows: Figure 2 As shown, the secondary winding 8 of the transformer is wound inside the PCB board 2, and the primary winding 7 of the transformer is wound on the outer surface of the PCB board 2.

[0036] Figure 3 and Figure 4 To illustrate the working process and its equivalent circuit, the synchronous rectifier diodes are replaced with diodes. Twelve synchronous rectifier diodes (SR) are arranged on the front side of PCB 2. a1 -SR a12 These are connected to the corresponding segments (represented by 'a' in the diagram) of the twelve secondary windings 8, with a corresponding output capacitor of 4C. a1 -C a12 The 12 synchronous rectifier tubes SR arranged on the reverse side of PBC plate 2 b1 -SR b12 These are connected to the corresponding segments (represented by b in the diagram) of the twelve secondary windings 8, with the corresponding output capacitor 4C. b1 -C b12 The edge magnetic posts 101 of the magnetic core 1 have line leads 3 between the positions where the output capacitor 4 and the synchronous rectifier tube 5 are placed and the center magnetic post 102. The line leads around the edge magnetic posts lead out the transformer's center tap and secondary ground, while the line leads 3 located in the center of the magnetic post 102 require a hole 104 in the top cover of the magnetic component to lead out the transformer's center tap and secondary ground. For example... Figure 3 As shown, during the positive half-cycle, SR a1 -SR a12 On, SR b1 -SR b12 When switched off, the current in the secondary winding 8 is as follows: Figure 3 The current in (a) flows in the direction shown and exits the transformer through the four magnetic notches and the top cover perforation. The symmetrical design of the electrical characteristics of the magnetic components and circuitry enables SR... a1 -SR a12 The currents are equal, and the secondary winding current i SRa There is a shortest path around the central magnetic column, and the current i of each output path is... o1 -i o12 The values ​​are also equal. The voltage across the capacitor at each output is V. o The voltage across each segment of the secondary winding is also V. o The voltage across the output capacitor is equal in magnitude but opposite in direction to the voltage across the output capacitor. There are three sets of output capacitors wound around a central magnetic core; that is, the voltage across one winding around the central magnetic core is 3V. o The output voltage is V o Therefore, the equivalent turns ratio of the secondary winding is 1 / 3, and because the primary winding connects the four central magnetic posts in series, the voltage carried by the primary winding around each central magnetic post is 1 / 4V. i For the negative half-cycle, such as Figure 4 As shown, SR a1 -SR a12 Off, SR b1 -SR b12 The operation process is similar to that of the positive half-cycle, except that the other 12 synchronous rectifier tubes are turned on. The electromotive force generated by electromagnetic induction charges the other 12 output capacitors in the direction of current shown in Figure (a).

[0037] Figure 5 The diagram illustrates the connection method of the drive signals in this embodiment. Taking the first surface of PCB board 2 as an example, the drive signal of one synchronous rectifier tube 5 for each central magnetic post 102 needs to be vertically introduced through a hole in the top cover of the magnetic component. The drive signals of the remaining synchronous rectifier tubes 5 can be directly introduced into the plane on the corresponding PCB surface. The method of introducing the drive signals of the synchronous rectifier tubes 5 on the second plane of PCB board 2 is consistent with that on the first plane.

[0038] The high-turn-ratio planar transformer provided by this invention has a variable number of segments for both the central magnetic post through which the primary winding passes and the secondary winding is divided. These segments can be arbitrarily selected, allowing for flexible transformer turn-ratio gain through appropriate combinations. In this embodiment, the number of central magnetic posts is defined as M, and the number of segments in the secondary winding is defined as N. Once M and N are selected, the dimensions of the central magnetic post can be calculated as follows.

[0039] After the synchronous rectifier diode is turned on, the voltage applied to any secondary winding surrounding the central magnetic post is NV. o The voltage applied to the M central magnetic pillars is MNV.o The voltage Vs(t) across a full turn of the winding and the magnetic flux density B(t) in core 1 are as follows: Figure 6 As shown, the effective cross-sectional area A of a single magnetic core 1 can be derived according to Faraday's law of electromagnetic induction. e :

[0040]

[0041] The effective cross-sectional area of ​​all the central magnetic pillars can be obtained by simply adding up the number of all the central magnetic pillars, A. ea =MA e .

[0042] Let B m and f s If the value of A remains constant, then A ea It is proportional to N and M, and N and M are related to A. ea The impact is the same, therefore there are two different implementation methods when matching the same transformer ratio. In this case, because the value of N*M remains unchanged, A... ea The value remains unchanged. Taking the case where the cylindrical shape of the core 1 is circular as an example, the effective area A of a central magnetic cylinder 102 is... e =πr 2 Then the radius r of the central cylinder of magnetic core 1 can be obtained:

[0043]

[0044] Assuming the width of the secondary winding is fixed at c, the total length l1 of one loop of the secondary winding around the central column of core 1 can be calculated, and thus the length l of each segment of the secondary winding can be obtained. s for:

[0045]

[0046] The total area A of the central magnetic column of the transformer ec for:

[0047]

[0048] The high-ratio planar transformer of this embodiment can achieve a more flexible transformer ratio. Figure 7 A schematic diagram of combinations of fractional-turn and matrix schemes with different structures is given. The positive horizontal axis represents the increase in the turns ratio of the fractional-turn scheme, where N increases; the positive vertical axis represents the increase in the turns ratio of the matrix scheme, where M increases. The transformer gain is G = M * N. To ensure G remains constant, the relationship between M and N can be freely adjusted. This can be achieved by placing the 2MN output capacitors and synchronous rectifier diodes at the junctions of the secondary windings of 1 / 2MN segment.

[0049] In summary, this invention combines the advantages of existing fractional-turn and matrix schemes for planar transformers while mitigating their disadvantages, thus meeting the market demand for high-ratio transformers as server power supply bus voltages increase. Therefore, this invention has broad application prospects in the field of planar transformers.

[0050] 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 fractional-turn planar transformer with a matrix integrated structure, characterized in that, include: Magnetic core (1), PCB board (2), the magnetic core (1) is provided with M, each magnetic core (1) is provided with a number of layers of primary winding (7) and N segments of secondary winding (8), wherein 2≤M≤20, 2≤N≤6; The magnetic core (1) includes an edge magnetic post (101), a central magnetic post (102), and a magnetic top cover (103). The edge magnetic post (101) and the central magnetic post (102) respectively penetrate the PCB board (2). The edge magnetic post (101) surrounds the central magnetic post (102) along the plane of the PCB board (2). A drawing space for drawing the winding is formed between the edge magnetic post (101) and the central magnetic post (102). The windings include the primary winding (7) drawn inside the PCB board (2) and the secondary winding (8) drawn on the first and second surfaces of the PCB board (2); the primary winding (7) is drawn on the central magnetic column (102) in the direction of current, and the primary windings (7) of adjacent layers are arranged at intervals; the secondary windings (8) on the first surface and the secondary windings (8) on the second surface are drawn symmetrically, and the secondary windings (8) on the first surface and the secondary windings (8) on the second surface are both distributed circumferentially around the central magnetic column (102); A circuit structure is provided between the secondary winding (8) on the first surface and the secondary winding (8) on the second surface. Each circuit structure includes an output capacitor (4) and a synchronous rectifier (5). The source of the synchronous rectifier (5) is connected to the ground terminal of the output capacitor (4). The positive potential terminals of the two output capacitors (4) in the circuit structure opposite to each other on the first surface and the second surface are connected. On the first surface, the drain of the synchronous rectifier (5) is connected to the same-name terminal of an adjacent secondary winding (8), and the positive potential terminal of the output capacitor (4) is connected to the opposite-name terminal of another adjacent secondary winding (8). On the second surface, the drain of the synchronous rectifier (5) is connected to the opposite end of an adjacent secondary winding (8), and the positive potential end of the output capacitor (4) is connected to the same potential end of another adjacent secondary winding (8).

2. The fractional-turn planar transformer with a matrix integrated structure according to claim 1, characterized in that, The first surface and the second surface are the front and back sides of the PCB board (2), respectively.

3. The fractional-turn planar transformer with a matrix integrated structure according to claim 1, characterized in that, The magnetic core (1) is provided with a line lead-out outlet (3) at the edge of the PCB board (2), and the magnetic core (1) is provided with a magnetic component top cover hole (104) inside the PCB board (2). The line lead-out outlet (3) and the magnetic component top cover hole (104) are used for the power lead-out routing of the output capacitor (4).

4. The fractional-turn planar transformer with a matrix integrated structure according to claim 1, characterized in that, The output capacitor (4) and synchronous rectifier (5) are fixed on the PCB board (2) by surface mount soldering.

5. A fractional-turn planar transformer with a matrix integrated structure according to claim 1, characterized in that, The positive potential terminal of the output capacitor (4) on the first surface is connected to the positive potential terminal of the output capacitor (4) on the second surface through a line; the source of the synchronous rectifier (5) is connected to the ground terminal of the output capacitor (4) and then grounded.

6. A fractional-turn planar transformer with a matrix integrated structure according to claim 1, characterized in that, The primary winding (7) is connected to an LLC resonant circuit.

7. A fractional-turn planar transformer with a matrix integrated structure according to claim 1, characterized in that, 4≤M≤12, 3≤N≤4.

8. A fractional-turn planar transformer with a matrix integrated structure according to claim 1, characterized in that, The primary winding (7) connects M central magnetic columns (102) in series according to the winding method of adjacent magnetic columns and opposite current flow direction. The secondary winding (8) surrounds each central magnetic column (102) and is divided into 2N segments.

9. A fractional-turn planar transformer with a matrix integrated structure according to claim 8, characterized in that, The 2N sets of output capacitors (4) and synchronous rectifier tubes (5) surrounding the M central magnetic pillars (102) are respectively set at the junction of the secondary windings (8) of the 2N segment.

10. A converter, characterized in that, Including a fractional-turn planar transformer with a matrix integrated structure as described in any one of claims 1 to 9.

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