High step-up ratio planar matrix transformer

Abstract

The application discloses a high-voltage-ratio planar matrix transformer, which is used for boosting the output voltage of a resonance cavity in an LLC resonance circuit and comprises a transformer magnetic core (10), two primary winding (20), two secondary winding (30), a primary winding pin (40) and a secondary winding pin (50). The transformer magnetic core further comprises a magnetic core upper pole plate (103), a magnetic core lower pole plate (104), two magnetic core middle columns (101) arranged on the magnetic core lower pole plate, and two magnetic core side legs (102). The overall structure of the transformer magnetic core (10) is centrally symmetrical. The number of the magnetic core middle columns (101) of the transformer is 2, the cross sections of the magnetic core middle columns are the same, the shape of each of the magnetic core middle columns is two semicircles clamping a rectangle, the magnetic core middle columns are arranged in parallel and are provided with air gaps with the same length. The winding winding directions of the two magnetic core middle columns are opposite to each other, the magnetic flux directions formed by the winding winding directions are opposite to each other, and the two magnetic core side legs (102) are arranged in parallel on the left side of one of the magnetic core middle columns and the right side of the other magnetic core middle column, respectively.

Description

Technical Field

[0001] This invention belongs to the field of power electronics technology, and specifically relates to a high step-up ratio planar matrix transformer. Background Technology

[0002] In recent years, the rapid development of the photovoltaic energy storage industry has made factors such as the energy conversion efficiency, power density, and cost of microinverters increasingly important to their competitiveness. The low voltage (28V-45V) generated by photovoltaic panels typically requires multiple voltage boosts to be converted to DC bus voltage (400V) before finally being inverted and connected to the grid. Therefore, planar matrix transformers with high boost ratios, high efficiency, high power density, and low cost are of significant research and development importance for microinverters.

[0003] Traditional transformer cores are typically prismatic or cylindrical, with a large vertical dimension, which hinders power board integration. Furthermore, these columnar cores have a small surface area, resulting in poor heat dissipation. For high step-up ratios, traditional transformers, with only one core column, have a large number of turns in the primary and secondary windings, significantly increasing eddy current losses due to the air gap. To optimize winding losses, Litz wire is usually used, which is more expensive than copper wire. Summary of the Invention

[0004] In view of the above-mentioned problems, the present invention provides a high step-up ratio planar matrix transformer, which can reduce the size of micro inverters while achieving a high step-up ratio, optimizing losses and parasitic inductance.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A high step-up ratio planar matrix transformer is used in LLC resonant circuits to boost the output voltage of the resonant cavity. It includes a transformer core, two primary windings, two secondary windings, primary winding pins, and secondary winding pins. The transformer core further includes an upper core plate, a lower core plate, two core pillars on the lower core plate, and two core side legs. The overall structure of the transformer core is centrally symmetrical. The transformer has two core pillars with identical cross-sections, each shaped like two semicircles enclosing a rectangle, arranged in parallel with air gaps of the same length. The windings on the two core pillars are wound in opposite directions, forming magnetic flux directions. They are also opposite to each other; the two core side legs are arranged in parallel on the left side of one core column and the right side of the other core column, respectively. The connection between the core side legs and the upper and lower core plates is mirror-polished. The cross-sections of the core side legs are the same and rectangular in shape. The cross-sectional area of ​​a single core side leg is half that of a single core column. The two primary windings and two secondary windings are all wound with copper layers of PCB board conductors. There are six copper layers in total on the PCB board, and each layer has two primary or secondary winding coils arranged in parallel and symmetrically wound. A slot is cut in the center of the two coils on each layer of the PCB board, and the two core columns of the transformer are respectively fitted into the two slots. The primary winding pins and secondary winding pins are set on the side of the copper layer of the PCB board conductors. The upper core plate, the PCB winding plate and the lower core plate are fitted into an integral plate structure. The primary winding pins and secondary winding pins are each arranged in a row, parallel and symmetrically set on the front and rear sides of the PCB board, and connected to the external circuit.

[0007] In one possible implementation, the two sets of primary windings are connected in parallel, and the two sets of secondary windings are connected in series. The arrangement of the primary and secondary winding PCBs of a single core column from top to bottom is as follows: first secondary layer - second primary layer - third secondary layer - fourth secondary layer - fifth primary layer - sixth secondary layer.

[0008] In one possible implementation, the windings are arranged in a mirror-symmetrical structure, and the vias of the windings are arranged on the front and back sides of the PCB board. The vias of the primary windings of the second to fifth layers are respectively arranged in the middle of the two pins of the corresponding primary windings; the vias of the first to third layers are respectively arranged in the front side of the central slot of the corresponding secondary windings; the vias of the fourth to sixth layers are respectively arranged in the rear side of the central slot of the corresponding secondary windings; and the vias of the third to fourth layers are respectively arranged in the middle of the two pins of the corresponding secondary windings.

[0009] In one possible implementation, the primary side pin ① of the first primary winding is connected to the primary side pin ④ of the second primary winding as the primary winding input terminal, and the primary side pin ② of the first primary winding is connected to the primary side pin ③ of the second primary winding as the primary winding output terminal, thereby realizing the parallel connection of the two primary windings.

[0010] In one possible implementation, the secondary side pin ② of the first secondary winding is connected to the secondary side pin ④ of the second secondary winding. The secondary side pin ① of the first secondary winding serves as the output terminal of the secondary winding, and the secondary side pin ③ of the first secondary winding serves as the input terminal of the secondary winding, thereby realizing the series connection of the two secondary windings.

[0011] The present invention has the following beneficial effects:

[0012] (1) By adopting the core center column design scheme, the transformer core can achieve a high step-up ratio through winding matrixing, and avoid the core volume being too large due to the excessive number of core center columns, thus avoiding waste.

[0013] (2) The design scheme of air gap and magnetic flux direction of magnetic core column is adopted. The magnetic flux of the two magnetic core columns mainly flows and converges on the upper and lower pole plates and side legs, reducing the magnetic coupling between the magnetic core columns.

[0014] (3) The magnetic flux of each core column of the transformer can be evenly divided into two parts, which are returned from the left and right sides by the upper or lower plate respectively, so that the magnetic flux density of each part of the core is roughly equal and the magnetic flux is canceled out to a good degree, thereby reducing the magnetic flux density and reducing the core loss.

[0015] (4) By adopting a winding matrix design scheme, the overall turns ratio of the transformer can be doubled based on the primary and secondary turns ratio of a single core column, thereby increasing the step-up ratio. Furthermore, the parallel connection of the primary side can halve the large current on the low-voltage side, reducing winding losses.

[0016] (5) By adopting a winding arrangement design scheme, parasitic inductance can be reduced, the degree of magnetomotive force change can be reduced, and winding loss can be reduced.

[0017] (6) By adopting the winding via design scheme, the distance between the via and the magnetic core can be increased without changing the size of the magnetic core, thereby reducing the cost of electrical insulation and PCB manufacturing and improving safety performance. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the discrete structure of a high step-up ratio planar matrix transformer according to an embodiment of the present invention;

[0019] Figure 2 This is a schematic diagram of the splicing structure of a high step-up ratio planar matrix transformer according to an embodiment of the present invention;

[0020] Figure 3 This is a schematic diagram showing the connection between the primary winding and the secondary winding in one embodiment of the present invention;

[0021] Figure 4 This is an overall XY plan view of the PCB winding in one embodiment of the present invention;

[0022] Figure 5 This is an XY plan view of the first layer (secondary side) of the PCB winding in one embodiment of the present invention;

[0023] Figure 6 This is an XY plan view of the second layer (primary side) of the PCB winding in one embodiment of the present invention;

[0024] Figure 7 This is an XY plan view of the third layer (secondary side) of the PCB winding in one embodiment of the present invention;

[0025] Figure 8 This is an XY plan view of the fourth layer (secondary side) of the PCB winding in one embodiment of the present invention;

[0026] Figure 9 This is an XY plan view of the fifth layer (primary side) of the PCB winding in one embodiment of the present invention;

[0027] Figure 10 This is an XY plan view of the sixth layer (secondary side) of the PCB winding in one embodiment of the present invention;

[0028] Figure 11 This is a plan view of the primary winding vias and pin holes in one embodiment of the present invention;

[0029] Figure 12 This is a plan view of the secondary winding vias and pin holes in one embodiment of the present invention;

[0030] Figure 13 This is a plan view of the safety spacing of the secondary winding and vias in one embodiment of the present invention;

[0031] Figure 14 This is a plan view of the safety spacing of the primary winding and vias in one embodiment of the present invention. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Reference Figure 1 and Figure 2The figures show discrete and spliced ​​structural diagrams of a high step-up ratio planar matrix transformer according to an embodiment of the present invention, used to boost the output voltage of the resonant cavity in an LLC resonant circuit. The transformer includes a transformer core 10, two primary windings 20, two secondary windings 30, primary winding pins 40, and secondary winding pins 50. The transformer core further includes an upper core plate 103, a lower core plate 104, two core pillars 101 on the lower core plate 104, and two core side legs 102. The overall structure of the transformer core 10 is centrally symmetrical. The transformer has two core pillars 101 with identical cross-sections, each shaped like two semicircles sandwiching a rectangle, arranged in parallel and with the same length of air gap. The windings on the two core pillars are wound in a specific manner. The directions of the magnetic flux are opposite to each other; the two core side legs 102 are arranged in parallel on the left side of one core column and the right side of the other core column, respectively. The connection between the core side legs 102 and the upper pole plate 103 and the lower pole plate 104 of the core is mirror polished. The cross-sections of the core side legs 102 are the same and rectangular in shape. The cross-sectional area of ​​a single core side leg 102 is half the cross-sectional area of ​​a single core column 101. The two primary windings 20 and the two secondary windings 30 are all wound with copper layers of PCB board conductors. There are six copper layers in total on the PCB board, and each layer has two primary or secondary winding coils arranged in parallel and symmetrically wound. A slot is cut in the center of the two coils on each layer of the PCB board, and the two core columns 101 of the transformer are respectively fitted into the two slots. The primary winding pin 40 and the secondary winding pin 50 are located on the copper layer side of the PCB board conductor. The upper pole plate 103 of the magnetic core, the PCB winding board and the lower pole plate 104 of the magnetic core are embedded into an integral plate structure. The primary winding pin 40 and the secondary winding pin 50 are each arranged in a row, parallel and symmetrically located on the front and rear sides of the PCB board, and connected to the external circuit.

[0034] In a specific application example, the two sets of primary windings are connected in parallel, and the two sets of secondary windings are connected in series. The PCB layout of the primary and secondary windings of a single core column, from top to bottom, is as follows: first secondary layer - second primary layer - third secondary layer - fourth secondary layer - fifth primary layer - sixth secondary layer. The turns ratio of the primary and secondary windings of both windings is 1:8. After the primary windings are connected in parallel and the secondary windings are connected in series, the overall turns ratio of the planar matrix transformer is 1:16. That is, when applied to a resonant circuit, the regulated output of the resonant cavity from 25V can be directly boosted to 400V.

[0035] Furthermore, such as Figure 3As shown, pin ① of the first primary winding is connected to pin ④ of the second primary winding as the input terminal of the primary winding, and pin ② of the first primary winding is connected to pin ③ of the second primary winding as the output terminal of the primary winding, thus realizing the parallel connection of the two primary windings. Pin ② of the first secondary winding is connected to pin ④ of the second secondary winding, pin ① of the first secondary winding serves as the output terminal of the secondary winding, and pin ③ of the first secondary winding serves as the input terminal of the secondary winding, thus realizing the series connection of the two secondary windings.

[0036] In a specific application example, the magnetic core is 56mm long, 24mm wide, and 11.5mm high. The lower electrode plate (104) is 4.5mm thick, and the side legs are 4.5mm wide and 2.5mm high. The two core pillars have identical cross-sections, employing a structure of two semicircles enclosing a rectangle. The rectangle is 14mm long, and the matrix width (semicircle diameter) is 10mm. The two core pillars have the same height of 2.34mm, and the distance between them and the upper electrode plate (the air gap) is equal to 0.16mm. The distance between the two core pillars is 14mm, and the distance between the core pillar and the side legs is 6.5mm. The cross-sectional area of ​​the core pillars is equal, both being 218.54mm². The side legs have the same cross-sectional area as the upper and lower electrode plates, approximately half the cross-sectional area of ​​a single core pillar, at 108 mm².

[0037] In a specific application example, the windings are arranged in a mirror symmetrical structure. The vias of the windings are arranged on the front and back sides of the PCB board. The vias of the primary windings of the second to fifth layers are arranged in the middle of the two pins of the corresponding primary windings. The vias of the first to third layers are arranged in front of the central slot of the corresponding secondary windings. The vias of the fourth to sixth layers are arranged in back of the central slot of the corresponding secondary windings. The vias of the third to fourth layers are arranged in the middle of the two pins of the corresponding secondary windings.

[0038] The primary winding's primary side pin ① is connected to the primary winding's primary side pin ④ as the primary winding's input terminal, and the primary winding's primary side pins ② and ③ as the primary winding's output terminal, thus achieving parallel connection of the two primary windings. The secondary winding's secondary side pin ② is connected to the secondary winding's secondary side pin ④, the primary winding's secondary side pin ① as the secondary winding's output terminal, and the secondary winding's secondary side pin ③ as the secondary winding's input terminal, thus achieving series connection of the two secondary windings.

[0039] Figure 4 This is an XY planar view of the PCB windings of a high step-up ratio planar matrix transformer, as shown below. Figure 4As shown, the PCB winding board is 46mm long and 60mm wide, consisting of winding I and winding II, and is made up of 6 stacked copper layers. Each copper layer has windings I and II arranged in a mirror image, in the following order: secondary-primary-secondary-secondary-primary-secondary. The individual windings from the top to the bottom are as follows: Figure 5 As shown, the secondary side (4 turns, first layer), as Figure 6 As shown, the primary edge (1 turn, second layer); as Figure 7 As shown, the secondary side (4 turns, third layer); as Figure 8 As shown, the secondary side (4 turns, fourth layer); as Figure 9 As shown, the primary edge (1 turn, fifth layer); as Figure 10 As shown, the secondary winding (4 turns, sixth layer). From the top view, the secondary winding of the first winding (Ⅰ) is wound as follows: from the outside to the inside - counterclockwise (secondary winding - first layer), from the inside to the outside - counterclockwise (secondary winding - third layer), from the outside to the inside - counterclockwise (secondary winding - fourth layer), from the inside to the outside - counterclockwise (secondary winding - sixth layer); the secondary winding of the second winding (Ⅱ) is wound as follows: from the outside to the inside - clockwise (secondary winding - first layer), from the inside to the outside - clockwise (secondary winding - third layer), from the outside to the inside - clockwise (secondary winding - fourth layer), from the inside to the outside - clockwise (secondary winding - sixth layer). From the top view, the primary winding of winding I is wound clockwise from the outside in (primary side - second layer) and clockwise from the inside out (primary side - fifth layer); the primary winding of winding II is wound counterclockwise from the outside in (primary side - second layer) and counterclockwise from the inside out (primary side - fifth layer). Different layers of the windings are connected by blind holes. The secondary winding of the first winding (I) is: first layer - hole ③ - third layer - hole ⑤ - fourth layer - hole ⑦ - sixth layer; the secondary winding of the second winding (II) is: first layer - hole ④ - third layer - hole ⑥ - fourth layer - hole ⑧ - sixth layer. The primary winding of the first winding (I) is: second layer - hole ① - fifth layer; the primary winding of the second winding (II) is: second layer - hole ② - fifth layer. The copper layer width of a single turn of the primary winding is 4.5 mm and the thickness is 0.21 mm. The copper layer width of a single turn of the secondary winding is 0.9 mm and the thickness is 0.14 mm. The ratio of the cross-sectional area of ​​the copper layer of a single turn of the primary winding to that of the secondary winding is 15:2.

[0040] Figure 11 and Figure 12 This is a planar view of the PCB vias and pin holes for a high step-up ratio planar matrix transformer, as shown below. Figure 11 As shown, the pin holes ①, ②, ③, and ④ on the primary side and the pin holes ①, ②, ③, and ④ on the secondary side are identical, all being single through holes with an inner diameter of 1.3mm and an outer diameter of 2.6mm. Vias ① and ② are identical, both consisting of six blind holes with a diameter of 1.7mm. Figure 12As shown, vias ③, ④, ⑤, ⑥, ⑦, and ⑧ are identical, each consisting of two through holes with a diameter of 0.6 mm.

[0041] Figure 13 and Figure 14 This is a planar view of the PCB safety spacing for a high step-up ratio planar matrix transformer, as shown below. Figure 13 As shown, the spacing between the conductors of each PCB winding is 0.3mm, the distance between the conductor and the board edge is 0.5mm, the distance between the board edge and the magnetic core is 0.5mm, and the distance between the conductor and the magnetic core is 1mm; the distance between the secondary winding vias and the magnetic core is 3.5mm, and the via spacing is 0.6mm; Figure 14 As shown, the distance between the primary winding conductor and the magnetic core is 1mm, the distance between the winding via and the edge of the conductor is 0.5mm, the distance between the conductor and the magnetic core is 11mm, and the distance between the via and the conductor is 0.6mm.

[0042] It should be understood that the exemplary embodiments described herein are illustrative and not restrictive. Although one or more embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art will understand that various changes in form and detail may be made without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. A high step-up ratio planar matrix transformer, used in LLC resonant circuits to boost the output voltage of the resonant cavity, characterized in that, The transformer core includes a transformer core (10), two primary windings (20), two secondary windings (30), primary winding pins (40), and secondary winding pins (50). The transformer core further includes an upper core plate (103), a lower core plate (104), two core columns (101) disposed on the lower core plate, and two core side legs (102). The overall structure of the transformer core (10) is centrally symmetrical. The transformer core columns (101) are two in number, with identical cross-sections, both in the shape of two semicircles sandwiching a rectangle, arranged in parallel and having the same openings. The air gap is of a certain length; the winding directions of the two core columns are opposite to each other, and the magnetic flux directions are also opposite to each other; the two core side legs (102) are arranged in parallel on the left side of one core column and the right side of the other core column, respectively. The connection between the core side leg (102) and the upper pole plate (103) and the lower pole plate (104) of the core is mirror polished. The cross-sections of the core side legs (102) are the same and are all rectangular. The cross-sectional area of ​​a single core side leg (102) is half the cross-sectional area of ​​a single core column (101); the two primary windings and the two secondary windings are all made of PCB. The PCB board has six copper layers, and each layer has two primary or secondary winding coils arranged in parallel and symmetrically wound. A slot is cut in the center of each coil in each layer of the PCB board, and the two core columns (101) of the transformer are respectively fitted into the two slots. The primary winding pins (40) and secondary winding pins (50) are set on the side of the copper layer of the PCB board. The upper pole plate of the core, the PCB winding board and the lower pole plate of the core are fitted into an integral plate structure. The primary winding pins (40) and secondary winding pins (50) are arranged in a row, parallel and symmetrically set on the front and rear sides of the PCB board, and connected to the external circuit. The two sets of primary windings are connected in parallel, and the two sets of secondary windings are connected in series. The arrangement of the primary and secondary windings of a single core column on the PCB board from top to bottom is as follows: first secondary layer - second primary layer - third secondary layer - fourth secondary layer - fifth primary layer - sixth secondary layer.

2. The high step-up ratio planar matrix transformer as described in claim 1, characterized in that, The windings are arranged in a mirror symmetrical structure. The vias of the windings are arranged on the front and back sides of the PCB board. The vias of the primary windings of the second to fifth layers are respectively arranged in the middle of the two pins of the corresponding primary windings. The vias of the first to third layers are respectively arranged in the front side of the central slot of the corresponding secondary windings. The vias of the fourth to sixth layers are respectively arranged in the rear side of the central slot of the corresponding secondary windings. The vias of the third to fourth layers are respectively arranged in the middle of the two pins of the corresponding secondary windings.

3. The high step-up ratio planar matrix transformer as described in claim 1, characterized in that, The primary side pin ① of the first primary winding is connected to the primary side pin ④ of the second primary winding as the primary winding input terminal, and the primary side pin ② of the first primary winding is connected to the primary side pin ③ of the first primary winding as the primary winding output terminal, thereby realizing the parallel connection of the two primary windings.

4. The high step-up ratio planar matrix transformer as described in claim 1, characterized in that, The secondary winding pin ② of the first secondary winding is connected to the secondary winding pin ④ of the second secondary winding. The secondary winding pin ① of the first secondary winding is used as the output terminal of the secondary winding, and the secondary winding pin ③ of the first secondary winding is used as the input terminal of the secondary winding, thereby realizing the series connection of the two secondary windings.

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