Planar transformer comprising a magnetic core made of two different materials

Abstract

The invention relates to a planar transformer comprising a magnetic core (1) and an electrically conductive element (2) surrounding at least a portion of the magnetic core (1). The magnetic core (1) comprises: - a first material having a magnetic permeability greater than or equal to 1000 and a magnetic field less than or equal to 50 A / m; and - a second material having a magnetic permeability less than or equal to 100 and a magnetic field greater than or equal to 10,000 A / m. Figure for the abstract: Fig. 2

Description

Title of the invention: Planar transformer comprising a magnetic core comprising two different materials

[0001] The invention relates to a planar transformer.

[0002] A transformer is a device for modifying a voltage delivered by an alternating electrical energy source. It typically comprises a primary winding and a secondary winding wound around a magnetic core. The alternating current flowing in the primary winding generates, by induction in the magnetic core, a magnetic field, which in turn generates an alternating current in the secondary winding.

[0003] The planar transformer is a particular type of transformer in which the winding is flat. In general, at least one of the primary winding and the secondary winding are formed by turns etched on a printed circuit. The printed circuit has at least one through opening in which the magnetic core engages, so that the turns etched on the printed circuit are wound around the magnetic core. [Fig.1a] represents such a transformer of the prior art.

[0004] Prior art planar transformers only allow power to be transferred and not stored.

[0005] The invention aims to provide a planar transformer configured to both transfer and store electrical power.

[0006] The invention proposes for this purpose a planar transformer comprising a magnetic core and an electrically conductive element surrounding at least part of the magnetic core.

[0007] According to the invention, the magnetic core comprises: - a first material having a magnetic permeability greater than or equal to 1000 and a magnetic field less than or equal to 50 A / m; and - a second material having a magnetic permeability less than or equal to 100 and a magnetic field greater than or equal to 10,000 A / m.

[0008] The first material has high permeability while the second material has low permeability.

[0009] The first material allows, thanks to its high permeability, the transfer of electrical power. The magnetic losses of the first material are also relatively low.

[0010] The second material allows, thanks to a relatively high magnetic field (in particular greater than or equal to 10,000 A / m), the storage of electrical power. The magnetic losses of the second material are also relatively high.

[0011] Particularly convenient preferred features of the planar transformer according to the invention are presented below.

[0012] The magnetic core comprises a first portion and a second portion assembled together so as to delimit a window through which the electrically conductive element passes so that the electrically conductive element surrounds said at least one part of the magnetic core, the first portion being made of the first material, the second portion being made of the second material.

[0013] The first portion has a U, E or I shape, the second portion having a plate shape.

[0014] The first portion has a U-shape, an E-shape or a plate-shape, the second portion having an I-shape.

[0015] The first portion has an E shape, the second portion has a plate shape.

[0016] The first portion has a U shape and the second portion has a plate shape, the second portion being assembled against sides of the first portion.

[0017] The second portion comprises at least one face facing the outside of the magnetic core.

[0018] The planar transformer comprises an air gap between the first portion and the second portion.

[0019] The planar transformer comprises at least two magnetic cores, preferably four magnetic cores.

[0020] Other features and advantages of the invention will become apparent in the description below with reference to the appended drawings, given by way of non-limiting example: - [Fig. 1a] represents a planar transformer of the prior art; - [Fig. 1b] represents a planar transformer according to one embodiment of the invention; and - figures 2 to 23 represent examples of embodiments of a magnetic core of the planar transformer.

[0021] The planar transformer T according to the invention comprises at least one magnetic core 1 and one electrically conductive element 2. [Fig. lb] schematically represents the planar transformer T according to an exemplary embodiment, on the one hand in a perspective view (on the right) and on the other hand in an exploded view (on the left). The magnetic core 1 is in this figure similar to that of the assembly A17 described later in relation to [Fig. 18].

[0022] The electrically conductive element 2 surrounds at least a portion of the magnetic core 1. The electrically conductive element 2 is in particular made of copper, for example a copper winding. The electrically conductive element 2 is preferably etched on a printed circuit.

[0023] Figures 2 to 23 schematically represent exemplary embodiments of the magnetic core 1 of a planar transformer according to the invention. The entire transformer is not shown in these figures, only the magnetic core 1 and the electrically conductive element 2 are shown schematically.

[0024] The magnetic core 1 comprises two different materials, called first material and second material. In order to distinguish them in the figures, the second material is hatched.

[0025] The first material has a high magnetic permeability p. In particular, the first material has a magnetic permeability p greater than or equal to 1000. The first material has a weak magnetic field H. In particular, the first material has a magnetic field H less than or equal to 50 A / m.

[0026] The magnetic losses of the first material are relatively low. In particular, the magnetic losses of the first material are less than or equal to 0.1 W / cm3 (at 100 kHz and 100 mT).

[0027] The first material is for example ferrite, in particular manganese-zinc ferrite.

[0028] The second material has a low magnetic permeability p. In particular, the second material has a magnetic permeability p less than or equal to 100. The second material has a high magnetic field H. In particular, the second material has a magnetic field H greater than or equal to 10,000 A / m.

[0029] The magnetic losses of the second material are relatively high. In particular, the magnetic losses of the second material are greater than or equal to 0.5 W / cm3 (at 100 kHz and 100 mT).

[0030] The second material is for example powder, in particular one of the following powders: Nanocrystalline powder; Amorphous powder with low magnetic permeability; Iron powder; Iron-nickel powder; Iron-silicon powder; Iron-silicon-boron powder; Iron-silicon-aluminum powder; Iron-nickel-molybdenum powder;

[0031] The magnetic core 1 comprises a first portion 10 and a second portion 11 assembled together so as to delimit a window 12 through which passes the electrically conductive element 2. The first portion 10 is made of the first material.

[0032] The first portion 10 has a U, E, I or plate shape.

[0033] The second portion 11 is made of the second material. The second portion 11 has an I or plate shape.

[0034] The U-shape comprises a central part 100 and two wings 101 extending the central part 100 on either side. The wings 101 are orthogonal to the central part 100.

[0035] The E-shape comprises three legs 102 parallel to each other, and a main part 103 orthogonally connecting the legs 102.

[0036] The I-shape has the shape of a rectangular parallelepiped.

[0037] Figures 2 to 23 represent several examples of assembly between the first portion 10 and the second portion 11. These figures represent the magnetic cores in their arrangement of use, horizontal or vertical, as explained later.

[0038] [Fig.2] shows a first example of association Al in which the magnetic core 1 comprises a first U-shaped portion 10 and a second I-shaped portion 11.

[0039] The second portion 11 extends between the wings 101 of the first U-shaped portion 10. The second portion 11 is arranged so that an external face 110 of the second portion 11 is coplanar with an external face 1010 of each of the wings 101 of the first portion 10. The second portion 11 here has a length equal to a width of each of the wings 101 of the first portion 10.

[0040] The magnetic core 1 also comprises an air gap E between the first portion 10 and the second portion 11. The air gap corresponds to the absence of magnetic material. The air gap E here has the same surface area as that of a longitudinal face of the second portion 11.

[0041] [Fig. 3] shows an example of association A2 comprising two magnetic cores 1, each magnetic core 1 being assembled according to the association AL. The first portions 10 of the two magnetic cores 1 are head-to-tail. In other words, an external face 1000 of the central part 100 of each first portion 10 is in contact with an external face 1000 of the central part 100 of the other first portion 10.

[0042] The electrically conductive element 2 passes through the windows 12 of the two magnetic cores.

[0043] [Fig.4] shows an example of association A3 comprising four magnetic cores, each magnetic core 1 being assembled according to association AL. Association A3 corresponds to a duplication of association A2. The first portions 10 of the magnetic cores are two by two head-to-tail. The cores ma magnetic cores are arranged so that the window 12 of each magnetic core 1 is opposite the window 12 of another magnetic core 1.

[0044] The electrically conductive element 2 passes through the windows 12 of the four magnetic cores.

[0045] [Fig. 5] shows an example of an association A4 comprising two magnetic cores, each magnetic core 1 being assembled according to the association A1. The magnetic cores 1 are assembled together so that the first portions 10 together form a frame. The first portions 10 frame the second portions 11. The wings 101 of the first portions 10 are in contact with each other and the central parts extend at two opposite ends. The second portions 11 of the magnetic cores extend parallel and in contact with each other.

[0046] The electrically conductive element 2 passes through the windows 12 of the two magnetic cores.

[0047] [Fig.6] shows an example of association A5 comprising four magnetic cores 1, each magnetic core 1 being assembled according to association AL. Association A5 corresponds to a duplication of association A4. The magnetic cores 1 are arranged so that window 12 of each magnetic core 1 is opposite window 12 of another magnetic core 1.

[0048] The electrically conductive element 2 passes through the windows 12 of the two magnetic cores 1.

[0049] In the associations A1 to A5, the wings 101 of the first portions 10 extend horizontally. Each window 12 is thus oriented horizontally.

[0050] [Fig.7] shows an example of association A6 similar to association AL. In association A6, the magnetic core 1 comprises a first U-shaped portion 10 and a second I-shaped portion 11. The wings 101 of the first portion 10 extend vertically. Thus, in its use arrangement, the magnetic core 1 is vertical. The window 12 is thus oriented vertically.

[0051] [Fig.8] shows an example of association A7 comprising two magnetic cores 1, each magnetic core 1 being assembled according to association A6. One of the wings 101 of each magnetic core 1 is parallel and in contact with one of the wings 101 of the other magnetic core 1. The first portions 10 of the two magnetic cores 1 thus together form an E.

[0052] The electrically conductive element 2 passes through the windows 12 of the two magnetic cores 1.

[0053] [Fig.9] shows an example of association A8 comprising four magnetic cores, each magnetic core 1 being assembled according to association A6. Association A8 corresponds to a duplication of association A7. The magnetic cores are arranged so that window 12 of each magnetic core 1 is in opposite the window 12 of another magnetic core 1.

[0054] The electrically conductive element 2 passes through the windows 12 of the four magnetic cores.

[0055] In the associations A6 to A8, the wings 101 of the first portions 10 extend vertically. Each window 12 is thus oriented vertically.

[0056] [Fig. 10] shows an example of association A9 in which the magnetic core 1 comprises a first U-shaped portion 10 and a second plate-shaped portion 11.

[0057] The second portion 11 extends against the external faces 1010 of the wings 101 of the first U-shaped portion 10. The second portion 11 extends parallel to the central part 100 of the first portion 10.

[0058] [Fig. 11] shows an example of association A10 comprising two magnetic cores 1, each magnetic core 1 being assembled according to association A9. The first portions 10 of the two magnetic cores 1 are head-to-tail. In other words, an external face 1000 of the central part 100 of each first portion 10 is in contact with an external face 1000 of the central part 100 of the other first portion 10.

[0059] The electrically conductive element 2 passes through the windows 12 of the two magnetic cores 1.

[0060] [Fig. 12] shows an example of an association A11 comprising four magnetic cores 1, each magnetic core 1 being assembled according to the association A9. The association A11 corresponds to a duplication of the association A10. The first portions 10 of the magnetic cores are two by two head to tail. The magnetic cores are arranged so that the window 12 of each magnetic core 1 is opposite the window 12 of another magnetic core 1.

[0061] The electrically conductive element 2 passes through the windows 12 of the four magnetic cores 1.

[0062] [Fig. 13] shows an example of an association A12 comprising two magnetic cores, each magnetic core 1 being assembled according to the association A9. The central portions 100 of the magnetic cores 1 extend at two ends opposite each other. The second portions 11 of the magnetic cores extend parallel and in contact with each other.

[0063] The electrically conductive element 2 passes through the windows 12 of the two magnetic cores 1.

[0064] [Fig. 14] shows an example of association A13 comprising four magnetic cores 1, each magnetic core 1 being assembled according to association A9. Association A13 corresponds to a duplication of association A12. The magnetic cores are arranged so that window 12 of each magnetic core 1 is in opposite the window 12 of another magnetic core 1.

[0065] The electrically conductive element 2 passes through the windows 12 of the four magnetic cores 1.

[0066] In the associations A9 to A13, the wings 101 of the first portions 10 extend horizontally. Each window 12 is thus oriented horizontally.

[0067] [Fig. 15] shows an example of association A14 similar to association A9. In association A14, the magnetic core 1 comprises a first U-shaped portion 10 and a second plate-shaped portion 11. The second portion 11 extends against the outer faces 1010 of the wings 101 of the first U-shaped portion 10. The second portion 11 extends parallel to the central part 100 of the first portion 10.

[0068] The wings 101 of the first portion 10 extend vertically. Thus, in its operating arrangement, the magnetic core 1 is vertical. The window 12 is thus oriented vertically.

[0069] [Fig. 16] shows an example of association A15 comprising two magnetic cores 1, each magnetic core 1 being assembled according to association A14. One of the wings 101 of each magnetic core 1 is parallel and in contact with one of the wings 101 of the other magnetic core 1. The first portions 10 of the two magnetic cores thus together form an E.

[0070] The electrically conductive element 2 passes through the windows 12 of the two magnetic cores 1.

[0071] [Fig. 17] shows an example of association A16 comprising four magnetic cores, each magnetic core 1 being assembled according to association A14. Association A16 corresponds to a duplication of association A15. The magnetic cores are arranged so that window 12 of each magnetic core 1 is opposite window 12 of another magnetic core 1.

[0072] The electrically conductive element 2 passes through the windows 12 of the four magnetic cores 1.

[0073] In the associations A14 to A16, the wings 101 of the first portions 10 extend vertically. Each window 12 is thus oriented vertically.

[0074] [Fig. 18] shows an example of association A17 in which the magnetic core 1 comprises a first E-shaped portion 10 and two second I-shaped portions 11.

[0075] Each second portion 11 extends between the legs 102 of the first portion 10 in E. Each second portion 11 is arranged so that an external face 110 of the second portion 11 is coplanar with an external face 1020 of each of the legs 102 of the first portion 10. The second portion 11 here has a length equal to a width of each of the legs 102 of the first portion 10.

[0076] The magnetic core 1 here comprises two windows 12. Each window 12 is delimited by the legs 102, the main part 103 of the first portion 10, and one of the second portions 11. The electrically conductive element 2 passes through the two windows 12.

[0077] The magnetic core 1 also comprises an air gap E between the first portion 10 and each of the second portions 11. The air gap here has the same surface area as that of a longitudinal face of the second portion 11.

[0078] [Fig. 19] shows an example of association A18 comprising two magnetics, each magnetic core 1 being assembled according to association A17. Association A18 corresponds to a duplication of association A17. The magnetic cores are arranged so that window 12 of each magnetic core 1 is opposite window 12 of another magnetic core 1.

[0079] The electrically conductive element 2 passes through the windows 12 of the two magnetic cores.

[0080] [Fig.20] shows an example of association A19 in which the magnetic core 1 comprises a first portion 10 in the shape of an E and a second portion 11 in the shape of a plate.

[0081] The second portion 11 extends against external faces 1020 of the legs 102 of the first portion 10 in E. The second portion 11 extends parallel to the main part 103 of the first portion 10.

[0082] [Fig.21] shows an example of association A20 comprising two magnetics, each magnetic core 1 being assembled according to association A19. Association A20 corresponds to a duplication of association A19. The magnetic cores 1 are arranged so that window 12 of each magnetic core 1 is opposite window 12 of another magnetic core 1.

[0083] The electrically conductive element 2 passes through the windows 12 of the two magnetic cores.

[0084] In the associations A17 to A20, the legs 102 of the first portions 10 extend vertically. The windows 12 are thus oriented vertically.

[0085] [Fig.22] shows an example of an association A21 comprising two magnetic cores. Each magnetic core 1 comprises two first portions 10 in the form of a plate and two second portions 11 in the form of an I. The first portions 10 of each magnetic core 1 are parallel to each other. The second portions 11 of each magnetic core 1 extend between the first portions 10. The second portions 11 of each magnetic core 1 are parallel to each other. The second portions 11 of each magnetic core 1 are spaced apart from each other so as to delimit with the first portions 10 the window 12 of the magnetic core 1. The second portions 11 of each magnetic core 1 extend transversely to the first portions 10.

[0086] The two magnetic cores are arranged so that each first portion 10 of each magnetic core 1 extends in the extension (i.e. in the same plane) of one of the first portions 10 of the other magnetic core 1.

[0087] One of the second portions 11 of each magnetic core 1 comprises a longitudinal face in contact with a longitudinal face of one of the second portions 11 of the other magnetic core 1.

[0088] Each magnetic core 1 comprises two air gaps E. Each air gap E being formed between one of the first portions 10 and one of the second portions IL. The air gap E here has the same surface as that of a longitudinal face of the second portion IL.

[0089] The electrically conductive element 2 passes through the windows 12 of the two magnetic cores.

[0090] [Fig.23] shows an example of an association A22 comprising two magnetic cores. Each magnetic core 1 comprises two first I-shaped portions 10 and two second plate-shaped portions 11. The association A22 has a structure similar to the association A21 and differs only in that the first and second portions 10, 11 are reversed.

[0091] In the associations A21 and A22, the first portions 10 and the second portions 11 extend horizontally. The windows 12 are thus oriented horizontally.

[0092] The associations A1 to A22 allow the planar transformer to store and transmit an electrical power Ps which can be expressed according to the following simplified expression:

[0093] d rz rx Ps ~ ------

[0094] The terms of this expression are defined as follows: - Im corresponds to the magnetic current generating the magnetic field, - ^max corresponds to the ratio of the conduction time divided by the period; - 7 is the efficiency; - Acui is the section of the electrically conductive element corresponding to the section through which the electric current passes; - Ae is the section of the magnetic materials corresponding to the section through which the magnetic flux passes; - A 6 corresponds to the temperature rise of the transformer; - Fref is the reference frequency at which the material is characterized; - Ve corresponds to the volume of the first material and second material; - K2 are parameters or coefficients characteristic of the losses of the material ; - J is the current density passing through the window; - times is the expansion (i.e. the way in which the electrically conductive element is wound in the window) between 0 and 1; - ^max is the frequency at which the transformer operates.

[0095] The associations A1 to A22 make it possible to obtain the following characteristics: - a large transformer thus providing greater stored and transferred power (of the order of 10 kW or even 100 kW, whereas the transformers of the prior art make it possible to obtain a transferred power of at most 1000 W); - low equivalent permeability (p < 100); - a high equivalent magnetic field (H > 10,000 A / m); - low magnetic losses by maximizing the volume of the first material and minimizing the volume of the second material; - low thermal resistance by maximizing the exchange surface with the exterior, in particular for the second material; - a large window for the passage of the electrically conductive element to reduce losses linked to the copper electrically conductive element; - a section of high Ae magnetic materials.

[0096] The associations A10, A11, A12, A13, A14, A15, A16, A20, A22 particularly make it possible to increase the electrical power transmitted and stored. This is made possible by a high admissible magnetic current, in particular thanks to a second portion 11 in the form of a plate.

[0097] The associations Al, A2, A3, A4, A5, A6, A7, A8, A17, A18, A19, A21 particularly make it possible to limit the temperature rise A0. This is made possible by a high volume of low-loss material (the first material), and a low volume of high-loss material (the second material).

[0098] The associations A1, A2, A3, A4, A5, A6, A7, A8, A17, A18, A19, A21 particularly make it possible to increase the electrical power transmitted and stored. This is made possible by a high admissible magnetic current, in particular thanks to the presence of an air gap.

[0099] The associations Al, A2, A3, A6, A7, A8, A9, A10, A11, A14, A15, A16, A17, A18, A19, A20, A22 also make it possible to limit the temperature rise A0. This is made possible by a large surface area of ​​the second material facing the outside of the planar transformer. The second material having high losses, this makes it possible to evacuate the heat more easily. The thermal resistance Rth in these associations is thus weak.

[0100] The associations A9, A10, A11, A12, A13, A14, A15, A16 also make it possible to limit the temperature rise A0. This is made possible by a high section Acui of the electrically conductive element 2. The section A„„, the electrical resistances of the conductors passing through this section are in fact reduced. These associations make it possible to obtain a larger window 12 for the passage of the electrically conductive element 2, in particular thanks to the association of a first U-shaped portion 10 and a second plate-shaped portion 11.

[0101] The associations A3, A5, A8, A11, A13, A16, A18, A20 also make it possible to increase the transmitted and stored electrical power. This is made possible by a high section of the magnetic materials Ae. These associations assemble several magnetic cores in order to obtain a high section of the magnetic materials Ae.

[0102] The associations A7, A8, A15, A16 allow by construction to join two by two wings 101 of the first portions 10 of the magnetic cores. This makes it possible to obtain a central section corresponding to the section of the joined wings twice as large as a section of each of the wings 101 located towards the outside of the transformer. When an electric current passes through the electrically conductive element 2, a magnetic flux is generated and the flux is divided into two at the level of the central section. The magnetic cores thus behave as if they were placed in parallel. The same advantage applies in the case of the associations A2, A3, A10, A11 in which the central parts 100 are joined.

[0103] Depending on the desired characteristics (in particular those detailed above), linked to the intended application, a choice may be made on one of the associations A1 to A22.

[0104] The associations A1 to A22 are present for some horizontal arrangements and for others vertical arrangements. The choice between these arrangements depends on the intended application (for example if it is desired to have a single or several windings of electrically conductive element 2).

[0105] The planar transformer of the invention allows, by its structure comprising two types of materials, to store electrical power in addition to transferring it. It also allows, by construction of the assemblies of the core(s), in particular the associations Al to A22, to increase the electrical power stored and transferred.

[0106] In the combinations shown and described, the transformer comprises one, two or four magnetic cores. Of course, the transformer may comprise a different number, in particular greater than four, of magnetic cores. Increasing the number of magnetic cores makes it possible to increase the electrical power transferred and stored.

Claims

Claims

1. Planar transformer comprising a magnetic core (1) and an electrically conductive element (2) surrounding at least a portion of the magnetic core (1), said transformer being characterized in that the magnetic core (1) comprises: - a first material having a magnetic permeability greater than or equal to 1000 and a magnetic field less than or equal to 50 A / m; and - a second material having a magnetic permeability less than or equal to 100 and a magnetic field greater than or equal to 10,000 A / m.

2. A planar transformer according to claim 1, wherein the magnetic core (1) comprises a first portion (10) and a second portion (11) assembled together so as to delimit a window (12) through which the electrically conductive element (2) passes so that the electrically conductive element (2) surrounds said at least one part of the magnetic core (1), the first portion (10) being made of the first material, the second portion (11) being made of the second material.

3. A planar transformer according to claim 2, wherein the first portion (10) has a U, E or I shape, the second portion (11) has a plate shape.

4. A planar transformer according to claim 2, wherein the first portion (10) has a U-shape, an E-shape or a plate-shape, the second portion (11) has an I-shape.

5. A planar transformer according to claim 2, wherein the first portion (10) has an E shape, the second portion (11) has a plate shape.

6. A planar transformer according to claim 2, wherein the first portion (10) has a U shape and the second portion (11) has a plate shape, the second portion (11) being assembled against flanks of the first portion (10).

7. Planar transformer according to one of claims 2 to 6, in which the second portion (11) comprises at least one face facing the outside of the magnetic core (1).

8. Planar transformer according to one of claims 2 to 7, comprising an air gap between the first portion (10) and the second portion (11).

9. Planar transformer according to one of claims 1 to 8, comprising at least two magnetic cores, preferably four magnetic cores.

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