Transformer and method for producing such transformer

Abstract

The transformer (100) comprises: a printed circuit board (102, 104), the printed circuit board comprising conductive tracks (102B, 102C, 104B, 104C); a rigid electrical conductor (106, 108, 110); a primary winding comprising at least a conductive track (102B, 102C, 104B, 104C); a secondary winding comprising at least a rigid electrical conductor (106, 108, 110); and a core (116A, 116B) for electromagnetically coupling the primary winding to the secondary winding. The transformer further comprises an electrically insulating film (112, 114, 116, 118) interposed between the conductive tracks (102B, 102C, 104B, 104C) of the printed circuit board (102, 104) and the rigid electrical conductors (106, 108, 110), said film comprising two adhesive layers pressed against the conductive tracks (102B, 102C, 104B, 104C) of the printed circuit board (102, 104) and the rigid electrical conductors (106, 108, 110), respectively.

Description

Technical Field

[0001] The invention relates to a transformer and a method for producing such a transformer. Background Art

[0002] A transformer is known from the prior art, comprising:

[0003] a printed circuit board comprising an electrically insulating sheet and conductive tracks extending on one face of the electrically insulating sheet;

[0004] Rigid electrical conductor;

[0005] a primary winding comprising at least a conductive track of a printed circuit board;

[0006] a secondary winding comprising at least a rigid electrical conductor; and

[0007] An electromagnetic core couples the primary winding and the secondary winding.

[0008] In the prior art, the printed circuit board further comprises an electrically insulating layer covering the upper rails, and the rigid electrical conductors are bonded to the upper rails. Now, with conventional methods for producing printed circuit boards, the electrically insulating layer will be corrugated. This factor plus the adhesive means that there is a significant distance between the upper rails and the rigid electrical conductors, making it impossible to obtain a truly flat transformer.

[0009] It may therefore be desirable to provide a transformer that allows at least some of the above-mentioned problems and constraints to be overcome. Summary of the invention

[0010] Therefore, a transformer is proposed, comprising:

[0011] a printed circuit board comprising an electrically insulating sheet and conductive tracks extending on one face of the electrically insulating sheet;

[0012] Rigid electrical conductor;

[0013] a primary winding comprising at least a conductive track of a printed circuit board;

[0014] a secondary winding comprising at least a rigid electrical conductor; and

[0015] an electromagnetic core coupling the primary winding and the secondary winding;

[0016] Characterized in that the transformer further comprises:

[0017] An electrical insulating film is inserted between the conductive tracks of a printed circuit board and a rigid electrical conductor, the electrical insulating film comprising an electrical insulating layer and two adhesive layers respectively on two opposite sides of the electrical insulating layer, the adhesive layers respectively being tightly pressed against the conductive tracks of the printed circuit board and the rigid electrical conductor.

[0018] Thus, by using an electrically insulating film, it is possible to use a printed circuit board with bare upper tracks (that is, not covered by an electrically insulating layer). In this way, the problem of corrugation of the electrically insulating layer is avoided.

[0019] The present invention may further have one or more of the following optional features in any technically possible combination.

[0020] Optionally, the electrically insulating layer of the electrically insulating film has a thickness of less than 500 μm.

[0021] Also optionally, the electrically insulating layer of the electrically insulating film has a thermal conductivity of at least 0.2 W / mK.

[0022] Also optionally, the electrically insulating layer of the electrically insulating film is made of a dielectric such as one of: aromatic polyamide complex, polyamide, HT (high temperature) polyester and polyester.

[0023] Also optionally, each adhesive layer is a pressure sensitive adhesive or a thermosetting adhesive.

[0024] Also optionally, each adhesive layer has a thickness of less than 100 μm.

[0025] Also optionally, the transformer comprises a plurality of printed circuit boards and a plurality of rigid electrical conductors alternately stacked on each other, and further comprises an electrical insulating film interposed between each conductive track of the printed circuit board and the rigid electrical conductor facing the conductive track in the stack.

[0026] Also optionally, the rigid electrical conductors are present in an odd number in the stack, the rigid electrical conductors except for the middle rigid electrical conductor have the same first thickness, and the middle rigid electrical conductor has a second thickness that is twice the first thickness.

[0027] A method for producing a transformer according to the invention is also proposed, the method comprising:

[0028] obtaining a printed circuit board, a rigid electrical conductor, and an electrical insulating film separated from each other;

[0029] pressing the adhesive layer of the electrically insulating film tightly against the conductive tracks and the rigid electrical conductor of the printed circuit board, respectively; and

[0030] The primary winding and the secondary winding of the transformer are coupled by means of a coupling core. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The invention will be better understood from the following description which is given by way of example only and which refers to the accompanying drawings, in which:

[0032] In the figure:

[0033] Figure 1 is an exploded cross-sectional view of a transformer according to the present invention;

[0034] Figure 2 is a cross-sectional view of the assembled transformer;

[0035] Figure 3 is a 3D exploded view of the transformer; and

[0036] Figure 4 is a flow chart of a method for producing a transformer according to the present invention. DETAILED DESCRIPTION

[0037] Now refer to Figure 1 , Figure 2 and Figure 3 An example of a transformer 100 according to the present invention is described.

[0038] The transformer 100 comprises a stack-up of components in an arbitrary direction X which is considered to be a vertical direction.

[0039] The stack firstly comprises at least one printed circuit board and, in the example shown, two printed circuit boards, which are provided with reference numerals 102 , 104 .

[0040] Each printed circuit board 102, 104 includes an electrically insulating sheet 102A, 104A having upper (upper) faces 102A opposite to each other. 上 、104A 上 and lower surface 102A 下 、104A 下 The electrical insulating sheets 102A, 104A include, for example, prepreg.

[0041] Each printed circuit board 102, 104 further comprises at least one conductive track on the upper surface 102A of the electrically insulating sheet 102A, 104A. 上 、104A 上 Or below 102A 下 、104A 下 In the illustrated example, each printed circuit board 102, 104 includes an upper surface 102A. 上 、104A 上 The upper rails 102B and 104B extend upward, and the lower rails 102A 下 、104A下 Each track 102B, 102C, 104B, 104C is bare, that is to say not covered by a layer of electrical insulation such as prepreg, and is therefore directly accessible.

[0042] Each track 102B, 102C, 104B, 104C is made of copper, for example.

[0043] Each printed circuit board 102 , 104 has a thickness of at most 2 mm, for example 1.3 mm.

[0044] The insulating sheet of each printed circuit board has a thermal conductivity of at least 0.2 W / mK, for example 0.3 W / mK, and each track has a thermal conductivity of at least 300 W / mK, for example 350 W / mK.

[0045] The stack further comprises at least one rigid electrical conductor (busbar), which is preferably flat. Each rigid electrical conductor is made of copper, for example. Each rigid electrical conductor zigzags back and forth in a plane perpendicular to the vertical direction X, for example.

[0046] When a number of rigid electrical conductors are provided, these rigid electrical conductors are preferably alternated with printed circuit boards. In the example shown, three rigid electrical conductors 106, 108, 110 are provided. The printed circuit board 102 extends between the rigid electrical conductor 106 and the rigid electrical conductor 108, and the printed circuit board 104 extends between the rigid electrical conductor 108 and the rigid electrical conductor 110. Preferably, when (as in the example shown) the rigid electrical conductors 106, 108, 110 are present in an odd number in the stack, the rigid electrical conductors 106, 110 except the middle electrical conductor 108 have the same first thickness, and the middle rigid electrical conductor 108 has a second thickness, which is twice the first thickness. Specifically, in theory, an even number of rigid electrical conductors (one on each side of each printed circuit board) all having the same thickness will be required. However, in this case, the two middle rigid electrical conductors will be back to back to each other. In order to save one component, the two components can be replaced by a single rigid electrical conductor (rigid electrical conductor 108 in the example shown) of twice the thickness.

[0047] This alternation makes it possible to obtain good electromagnetic properties, resulting in lower AC resistance and lower electrical power losses.

[0048] The transformer 100 further comprises at least one electrically insulating film in order to insulate the rigid electrical conductors 106, 108, 110 from the tracks 102B, 102C, 104B, 104C of the printed circuit boards 102, 104. Each electrically insulating film is thus inserted between the tracks of one of the printed circuit boards 102, 104 and the opposite rigid electrical conductor 106, 108, 110. In the example described, four electrically insulating films 112, 114, 116, 118 are provided, which are inserted respectively between the rigid electrical conductor 106 and the printed circuit board 102, the printed circuit board 102 and the rigid electrical conductor 108, the rigid electrical conductor 108 and the printed circuit board 104, and the printed circuit board 104 and the rigid electrical conductor 110.

[0049] Each of the electrical insulating films 112, 114, 116, 118 is in the form of a double-sided adhesive. More specifically, each of the electrical insulating films 112, 114, 116, 118 includes an electrical insulating layer having upper and lower surfaces opposite to each other. These surfaces are respectively covered with an upper adhesive layer and a lower adhesive layer ( Figure 1 Thus, one of the two adhesive layers is pressed tightly against the tracks of one of the printed circuit boards, and the other adhesive layer is pressed tightly against the opposite rigid electrical conductor.

[0050] Besides providing electrical insulation of very small thickness, the electrically insulating films 112, 114, 116, 118 thus enable the printed circuit boards 102, 104 and the rigid electrical conductors 106, 108, 110 to be held securely together, thereby forming a single unit that is easier to handle.

[0051] The transformer 100 includes a primary winding that groups together tracks 102B, 102C, 104B, 104C of printed circuit boards 102, 104. Thus, tracks 102B, 102C, 104B, 104C are intended to be connected together. For example, tracks 102B, 102C are connected to each other via plated through holes that pass through electrically insulating sheet 102A, and tracks 104B, 104C are connected to each other via plated through holes that pass through insulating sheet 104A. The transformer 100 further includes, for example, a first connector 115A connected to one of tracks 102B, 102C and a second connector 115B connected to one of tracks 104B, 104C, the two connectors 115A, 115B being connected to each other directly or indirectly via an intermediate component (not depicted).

[0052] The transformer 100 further comprises a secondary winding that groups together rigid electrical conductors 106, 108, 110. These rigid electrical conductors have, for example, tabs that contact each other for electrical connection of the transformer 110. In the illustrated example, the transformer 100 is a center-tapped transformer, such that each rigid electrical conductor 106, 108, 110 has three tabs.

[0053] The transformer 100 further includes an electromagnetic core 116A, 116B for electromagnetic coupling of the primary winding and the secondary winding. For example, the coupling core 116A, 116B includes an upper part 116A and a lower part 116B located on both sides of the printed circuit board 102, 104 and the rigid electrical conductor 106, 108, 110 in the stack. The coupling core 116A, 116B generally includes a vertical portion (at Figure 3 The vertical sections 116A, 116B are marked as 302 in the figure, and these vertical sections pass through the printed circuit boards 102, 104 via openings, which are formed in the printed circuit boards for this purpose. To improve the coupling, the tracks 102B, 102C, 104B, 104C and / or the rigid electrical conductors 106, 108, 110 are wound around at least one of these vertical sections 302. The coupling cores 116A, 116B are made of ferromagnetic material, for example.

[0054] The stack may further include an upper electrically insulating film 120 inserted between the upper part 116A of the coupling core and the rigid electrical conductor 106, and / or a lower electrically insulating film 122 inserted between the lower part 116B of the coupling core and the rigid electrical conductor 110. In this case, the electrically insulating films 120, 122 include, for example, an electrically insulating layer like the electrically insulating films 112, 114, 116, 118, which is covered by an adhesive layer on the side of the rigid electrical conductor 106, 110 and is tightly pressed against the conductor in order to fix the electrically insulating films 120, 122. In contrast, the electrically insulating films 120, 122 preferably do not have an adhesive layer on the side of the parts 116A, 116B of the coupling core.

[0055] The electrically insulating layer of each electrically insulating film 112 , 114 , 116 , 118 , 120 , 122 is made of, for example, a dielectric such as one of: aramid complex, polyamide, HT (high temperature) polyester and polyester.

[0056] Each adhesive layer is, for example, a pressure-sensitive adhesive (also referred to by its English abbreviation PSA) layer or a thermosetting adhesive layer such as an epoxy or acrylic adhesive.

[0057] The thickness of the electrically insulating layer is preferably less than 500 μm. The thickness of the adhesive layer is preferably less than 100 μm. Thus, the thickness of the electrically insulating film is preferably less than 0.2 mm, for example equal to 0.1 mm. Furthermore, the rigid electrical conductors 106, 108, 110 each have a thickness of less than 1 mm, for example 0.5 mm, for example. Thus, the transformer 100 can be truly flat.

[0058] Furthermore, each electrically insulating film has a thermal conductivity of at least 0.2 W / mK, for example 0.3 W / mK.

[0059] The transformer 100 further preferably comprises a heat sink 124 which is pressed against the lower side of the lower part 116B of the coupling core. The heat sink 124 is, for example, a finned heat sink.

[0060] The transformer 100 also preferably comprises a clamp 126 attached to the heat sink 124 and designed to clamp the stack on the heat sink 124 by securing the upper part 116A of the coupling core.

[0061] Now refer to Figure 4 A method for producing a transformer according to the invention (such as Figure 1 An example of a method 400 of a transformer 100).

[0062] During the process of step 402 , one or more printed circuit boards 102 , 104 , one or more rigid electrical conductors 106 , 108 , 110 , and electrical insulating films 112 , 114 , 116 , 118 are obtained separated from one another.

[0063] During the process of step 404 , the adhesive layer of each electrically insulating film 112 , 114 , 116 , 118 is pressed tightly against the tracks 102B, 102C, 104B, 104C and the opposing rigid electrical conductors 106 , 108 , 110 of one of the printed circuit boards 102 , 104 , respectively.

[0064] During the process of step 406 , the primary winding and the secondary winding of the transformer 100 are coupled to each other by means of the coupling cores 116A, 116B.

[0065] During the process of step 408, the heat sink 124 is pressed tightly against the underside of the coupling cores 116A, 116B.

[0066] During the process of step 410 , the clamp 126 is attached to the heat sink 124 to hold the stack of transformer 100 together.

[0067] It is clearly evident that a transformer such as this one described above is very flat.

[0068] It should also be noted that the present invention is not limited to the embodiments described above. In particular, it will be apparent to those skilled in the art that various modifications may be made to the embodiments described above based on the teachings just disclosed to them.

[0069] In the detailed presentation of the invention given above, the terms used should not be interpreted as limiting the invention to the embodiments disclosed in this specification, but should be interpreted as including all equivalent schemes that a person skilled in the art can foresee by applying their general knowledge to implement the teachings just disclosed.

Claims

1. A transformer (100), include: A printed circuit board (102, 104) comprising an electrically insulating sheet (102A, 104B) and conductive tracks (102B, 102C, 104B, 104C) extending on one side of the electrically insulating sheet (102, 104); Rigid electrical conductor (106, 108, 110); a primary winding, the primary winding comprising at least a conductive track (102B, 102C, 104B, 104C) of the printed circuit board (102, 104); a secondary winding, the secondary winding comprising at least the rigid electrical conductor (106, 108, 110); and an electromagnetic core (116A, 116B) coupling the primary winding and the secondary winding; Characterized in that the transformer further comprises: An electrical insulating film (112, 114, 116, 118) is inserted between the conductive tracks (102B, 102C, 104B, 104C) of the printed circuit board (102, 104) and the rigid electrical conductor (106, 108, 110), the electrical insulating film comprising an electrical insulating layer and two adhesive layers respectively on two opposite sides of the electrical insulating layer, the adhesive layers respectively tightly pressed against the conductive tracks (102B, 102C, 104B, 104C) of the printed circuit board (102, 104) and the rigid electrical conductor (106, 108, 110).

2. The transformer (100) according to claim 1, in, The electrically insulating layer of the electrically insulating film (112, 114, 116, 118) has a thickness of less than 500 μm.

3. The transformer (100) according to claim 1 or 2, in, The electrically insulating layer of the electrically insulating film (112, 114, 116, 118) has a thermal conductivity of at least 0.2 W / mK.

4. The transformer (100) according to any one of claims 1 to 3, in, The electrically insulating layer of the electrically insulating film (112, 114, 116, 118) is made of a dielectric such as one of the following: aromatic polyamide complex, polyamide, HT polyester and polyester.

5. The transformer (100) according to any one of claims 1 to 4, in, Each adhesive layer is a pressure sensitive adhesive or a thermosetting adhesive.

6. The transformer (100) according to any one of claims 1 to 5, in, Each adhesive layer has a thickness of less than 100 μm.

7. The transformer (100) according to any one of claims 1 to 6, comprising a plurality of printed circuit boards (102, 104) and a plurality of rigid electrical conductors (106, 108, 110) alternately stacked on each other, and further comprising an electrically insulating film (112, 114, 116, 118) interposed between each conductive track (102B, 102C, 104B, 104C) of the printed circuit boards (102, 104) and the rigid electrical conductors (106, 108, 110) facing the conductive tracks in the stack.

8. The transformer (100) according to claim 7, in, The rigid electrical conductors (106, 108, 110) are present in an odd number in the stack, wherein the rigid electrical conductors (106, 110) except for the middle electrical conductor (108) have the same first thickness, and wherein the middle rigid electrical conductor (108) has a second thickness that is twice the first thickness.

9. A method (400) for producing a transformer (100) according to any one of claims 1 to 8, the method include: Obtaining (402) the printed circuit board (102, 104), the rigid electrical conductor (106, 108, 110) and the electrical insulating film (112, 114, 116, 118) separated from each other; pressing (404) the adhesive layer of the electrically insulating film (112, 114, 116, 118) tightly against the conductive tracks (102B, 102C, 104B, 104C) of the printed circuit board (102, 104) and the rigid electrical conductors (106, 108, 110), respectively; and The primary winding and the secondary winding of the transformer (100) are coupled (406) by means of the coupling core (116A, 116B).

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