Planar electrical transformer and assembly

Abstract

The present invention relates to a planar electrical assembly (10) comprising a substrate (5), in particular formed from sheets of prepreg, comprising, incorporated into the mass of the substrate (5): - at least one primary electrically conductive winding (12), in a first layer of the substrate (5), forming at least part of a primary circuit for an electrical transformer (1); and additionally - at least one secondary electrically conductive winding (22), in a second layer of the substrate (5) superimposed on the first layer, forming at least part of a secondary circuit for the electrical transformer (1).

Description

[0001] Planar electrical transformer and assembly

[0002] The present invention relates to the field of electrical transformers. More specifically, the present invention relates to a planar electrical assembly for forming a planar electrical transformer.

[0003] This electrical transformer belongs, for example, to an electrical circuit on board an electric or hybrid vehicle, this circuit being commonly called the “on-board network”.

[0004] This transformer allows for example the passage from a voltage of 12V or 48V to a voltage higher than 300V, for example 400V or 800V, and vice versa. Alternatively, this transformer is associated with an inverter / rectifier for charging from an electrical network external to the vehicle of an electrical energy storage unit of the vehicle, this electrical energy storage unit having for example a voltage of 48V or higher, for example a voltage higher than 300V such as a voltage of 400V, 800V, or higher.

[0005] The present invention thus relates to the manufacture of a planar electrical transformer, that is to say comprising a flat monolithic electrical assembly on which a ferromagnetic core is attached.

[0006] A known problem lies in the need to produce such electrical transformers that are compact, while taking into account the associated heating and cooling constraints.

[0007] The most classic known electrical transformer structure consists of a winding of turns of copper wire around a ferromagnetic core, generally made of ferrite. However, this type of coil has a significant bulk because the winding, also called coil, extends around the ferromagnetic core in space, in volume, in other words in a substantially homogeneous manner in the three dimensions of space.

[0008] According to the state of the art, it is therefore known to produce coils consisting of thin layers of electrically conductive material, in particular copper, superimposed, separated by thin electrically insulating layers. Said layers of electrically conductive material are brought into mechanical and electrical contact with each other, in particular by welding, to form a spiral capable of performing a coil function. This then produces substantially flat coils with a small spatial footprint.

[0009] However, to constitute an electrical transformer, it is necessary to have a primary circuit and a secondary circuit magnetically coupled via a ferromagnetic core. Thus, to produce an electrical transformer with reduced bulk, even taking into account the technology corresponding to the substantially flat coils mentioned above, in the state of the art, a printed circuit board, in other words a PCB (for "Printed Circuit Board"), is produced, formed of a substrate, for example made of pre-impregnated material, in which is incorporated at least one electrically conductive winding forming a secondary or primary circuit of an electrical transformer. Then at least one other winding forming a primary or secondary circuit, respectively, as well as a ferromagnetic core, is added to this PCB, in order to produce a complete electrical transformer.We thus report, on the PCB which integrates a secondary or primary winding, another conductive winding, generally in copper, which is soldered or welded, or even glued, on said PCB.

[0010] There is therefore still a need for a less bulky planar electrical transformer, as well as for a corresponding manufacturing method. The object of the invention, in general, is to promote the industrialization of the manufacture of planar electrical transformers.

[0011] More specifically, the invention relates to a planar electrical assembly comprising a substrate, in particular formed from prepreg sheets. The planar electrical assembly comprises, incorporated in the mass of the substrate:

[0012] - at least one primary electrically conductive winding, in a first layer of the substrate, and forming at least part of a primary circuit for an electrical transformer, and, on the other hand

[0013] - at least one secondary electrically conductive winding, in a second layer of the substrate superimposed on the first layer, forming at least part of a secondary circuit for the electrical transformer.

[0014] In particular, the secondary electrically conductive windings are held in the planar electrical assembly solely by the material of said substrate, in particular solely by the assembly of the prepreg sheets forming the material of said substrate. A prepreg sheet may also be referred to as a “prepreg sheet”.

[0015] According to one embodiment, the electrical assembly according to the invention comprises a plurality of first layers and a plurality of second layers stacked alternately. According to one embodiment, said at least one primary electrically conductive winding is spiral.

[0016] According to one embodiment, said at least one secondary electrically conductive winding has a wavy shape in the plane of the second layer. According to one embodiment, the planar electrical assembly comprises a plurality of secondary electrically conductive windings connected in parallel to common secondary electrical connection terminals.

[0017] According to one embodiment, the substrate is obtained from a stack of several prepreg sheets, thermoset together.

[0018] According to a variant:

[0019] - the first layer of the substrate is obtained from at least one first prepreg sheet on one face of which the at least one primary electrically conductive winding is etched, and

[0020] - the second layer of the substrate is obtained by applying at least one secondary electrically conductive winding to a prepreg face of the first layer and by covering said secondary electrically conductive winding with a second sheet of prepreg.

[0021] In particular, in the context of the present application, “prepreg face” designates an external surface of a layer, said surface being integrally formed of prepreg. According to a sub-variant:

[0022] - the first layer of the substrate is obtained from the first prepreg sheet on each face of which a respective primary electrically conductive winding is etched, a third prepreg sheet then covering one face of said first prepreg sheet;

[0023] - the second substrate layer is obtained by attaching the at least one secondary electrically conductive winding to the free face of the third prepreg sheet and covering it with said second prepreg sheet.

[0024] According to one embodiment:

[0025] - the primary electrically conductive winding is formed of an electrical track, in particular having a thickness less than or equal to 0.25 mm; and

[0026] - the secondary electrically conductive winding is formed of an electrically conductive blade (or a rigid conductor such as an electrically conductive bar), in particular having a thickness greater than or equal to 0.4 mm and / or less than 2 mm.

[0027] In at least a first layer, the primary electrically conductive winding may be an electrical track defining two spirals connected in series. These two spirals may have the same shape and be symmetrical to each other with respect to an axis intersecting the substrate. This axis then cuts the series connection between the two spirals.

[0028] From one end of a spiral to the other, including at the series connection between the two spirals, the electrical track defining the primary electrically conductive winding can maintain the same width.

[0029] Each spiral may have a primary connection terminal at its free end, this primary terminal allowing the connection of the primary electrical conductor winding to the outside. This connection is made, for example, with the high-voltage part of the on-board network.

[0030] From one spiral to another, the same number of turns can be present, for example between three and ten turns, for example five turns.

[0031] When several first layers are present, all or part of these first layers may comprise an electrical track defining two spirals connected in series, and these different spirals in series may be connected in parallel, from one first layer to the other.

[0032] In at least a second layer, the secondary electrical winding may be an electrically conductive blade having a corrugated shape.

[0033] In a stacking axis in which the first layer(s) are stacked with the second layer(s), the electrically conductive strip and the electrical track defining two spirals connected in series may at least partially overlap. Such an arrangement may further enhance the induction effect.

[0034] The electrically conductive blade may have a W shape when viewed along this stacking axis. The blade defines, for example, two round trips, each round trip comprising two straight parts connected together by an angled part.

[0035] The first round trip may extend between a first secondary terminal for connecting the secondary electrical conductor winding to the outside and a second secondary terminal for connecting this secondary electrical conductor winding to the outside. This connection is made, for example, with the low-voltage part of the on-board network.

[0036] The second round trip may extend between the aforementioned second secondary connection terminal and a third secondary connection terminal of the secondary electrical conductor winding to the outside. The second secondary connection terminal may make it possible to define an intermediate connection in the secondary electrical winding, for example at a midpoint. Alternatively, only two secondary terminals may be provided: the first and the third.

[0037] When both primary and secondary terminals are present, the primary terminals may protrude from the same first side of the substrate while the secondary terminals may protrude from the same second side of the substrate. These first and second sides of the substrate are, for example, opposite. This makes it possible to separate the high-voltage part and the low-voltage part of the transformer, and better meet different electrical insulation constraints.

[0038] Each straight part of the electrically conductive blade can be superimposed on the straight part of a spiral of the electrical track in a first layer along the stacking axis. This improves the coupling.

[0039] The cumulative width of the different turns forming a straight part of a spiral can be substantially equal to the width of the straight part of the electrically conductive blade superimposed on it.

[0040] When several second layers are present, all or part of these second layers may comprise an electrically conductive blade as described above. These different blades may be connected in parallel, from one second layer to another.

[0041] The above-mentioned overlap may be present for all first layers and all second layers.

[0042] The invention also relates to an electrical transformer comprising an electrical assembly according to the invention, as well as a ferromagnetic core attached to said substrate so as to magnetically couple the primary electrically conductive windings with the secondary electrically conductive windings. In particular, the ferromagnetic core is attached in a through opening of the planar electrical assembly.

[0043] In particular, the planar electrical assembly is pressed against a heat dissipation plate or against a fluid circulation cooling plate, so as to press one face of the ferromagnetic core against the heat dissipation plate or against the fluid circulation cooling plate to cool the ferromagnetic core. The invention further relates to a method for manufacturing an electrical assembly comprising a primary circuit and a secondary circuit, said method comprising the following steps:

[0044] - a first layer is formed comprising a first prepreg sheet on one face of which a primary electrically conductive winding is etched, said primary electrically conductive winding being intended to form at least part of a primary circuit of an electrical transformer;

[0045] - we have a monolithic electrical conductor, called a secondary electrical conductor winding;

[0046] - the secondary electrically conductive winding is deposited on a prepreg face of the first layer, said secondary electrically conductive winding being intended to form at least part of a secondary circuit of the electrical transformer;

[0047] - a second sheet of pre-impregnated material is placed on top;

[0048] - the assembly of prepreg sheets and primary and secondary electrically conductive windings is pressed and heated, so as to assemble said sheets together and form the electrical assembly comprising the stack of primary and secondary electrically conductive windings.

[0049] All or part of the foregoing and which has been described in connection with the planar electrical assembly still applies to the method, in particular the structure of the primary electrically conductive winding with the electrical track defining two spirals connected in series, and the structure of the secondary electrically conductive winding which has a corrugated shape.

[0050] According to an implementation of the method according to the invention:

[0051] - in the formation of the first layer of the substrate, a respective primary electrically conductive winding is etched on both sides of the first prepreg sheet,

[0052] - then a third sheet of prepreg is placed on one side of the first sheet of prepreg,

[0053] - then, the secondary electrically conductive winding is placed on the free face of the said third prepreg sheet.

[0054] According to one embodiment, primary electrical connectors electrically connected to the primary electrically conductive windings are then incorporated into the substrate.

[0055] According to one embodiment, each secondary electrical conductor has at least one end portion protruding from the superposition of said substrates, in the continuity of the plane of the second layer, to form at least one connection terminal of the secondary circuit.

[0056] According to one embodiment, a ferromagnetic core is attached to the substrate, so as to magnetically couple the primary electrically conductive windings with the secondary electrically conductive windings and form an electrical transformer. The invention will be better understood upon reading the following description, given solely by way of example, and referring to the appended drawings given by way of non-limiting examples, in which identical references are given to similar objects and in which:

[0057] - figure 1 shows an example of an electrical assembly according to the invention, in perspective;

[0058] - figure 2 represents a top view of the same example of electrical assembly according to the invention; figure 3 represents a top view of a corresponding electrical transformer, that is to say with an added ferromagnetic core;

[0059] - figure 4 represents a front view of the same example of electrical transformer according to the invention;

[0060] - figure 5 is a diagram of a multi-layer architecture of an electrical transformer according to the invention;

[0061] - Figure 6 represents an example of a primary electrically conductive winding;

[0062] - figure 7 represents an example of a secondary electrically conductive winding;

[0063] - Figure 8 shows a perspective view of the electrical transformer equipped with a heat dissipation plate.

[0064] It should be noted that the figures set out the invention in detail to enable the invention to be implemented, said figures of course being able to serve to better define the invention where appropriate.

[0065] The invention relates, in substance, to the production of a planar electrical transformer, monolithic with the exception of the single ferromagnetic core, which is added.

[0066] The invention therefore resides, firstly, in a substrate incorporating in the mass of the substrate a stacked structure of at least a first layer integrating an electrically conductive winding of the primary circuit and at least a second layer integrating an electrically conductive winding of the secondary circuit. The substrate is obtained from pre-impregnated material, in other words prepreg, for example epoxy resin. In particular, said substrate therefore forms a printed circuit board, in other words a PCB.

[0067] The invention also relates to a corresponding manufacturing method.

[0068] With reference to figures 1 to 7, the electrical transformer 1 according to an example of the invention thus comprises, firstly, a monolithic electrical assembly 10, in particular integrated into a PCB.

[0069] The assembly comprises a substrate 5, in particular obtained from prepreg. The substrate comprises a second layer in which a secondary conductive winding 22 is integrated, that is to say intended to form at least part of a secondary circuit of an electrical transformer.

[0070] Above this secondary conductive winding 22, a thickness of substrate 50, in particular obtained from prepreg in this case, covers said secondary electrical conductive winding 22 and separates it from a first layer which integrates a primary conductive winding 12, that is to say intended to form at least part of a primary circuit of an electrical transformer.

[0071] Above this primary conductive winding 12, a thickness of substrate 50, in particular obtained from prepreg in this case, covers said primary electrical conductive winding 12.

[0072] The 50 substrate thicknesses obtained from prepreg provide electrical insulation.

[0073] The primary 12 and secondary 22 electrically conductive windings have in particular a thickness of between 0.4 mm and 4 mm, preferably between 0.8 mm and 2 mm.

[0074] According to one embodiment, the primary electrically conductive winding 12 may take the form of a spiral, plane winding, for example shown in FIG. 6. The secondary electrically conductive winding 22 may take the form of a flat electrical conductor, also referred to as a “leadframe”, in particular having an undulating shape in the plane of the flat conductor, as illustrated for example in FIG. 7. In particular, the primary electrically conductive winding 12 is formed of an electrical track, in particular having a thickness less than or equal to 0.25 mm and the secondary electrically conductive winding 22 is formed of an electrically conductive blade having a thickness greater than or equal to 0.4 mm and / or less than 2 mm.

[0075] In at least a first layer, the primary electrically conductive winding 12 is here an electrical track defining two spirals 30 connected in series. These two spirals 30 have in the example considered the same shape and they are symmetrical to each other with respect to an axis (X) intersecting the substrate 5. As shown in FIG. 6, this axis (X) here intersects the connection 31 in series between the two spirals 30.

[0076] It is also observed in Figures 2 and 3 that, from one end of a spiral 30 to the other, including at the level of the connection 31 in series between the two spirals 30, the electrical track defining the primary electrical conductive winding 12 can retain the same width.

[0077] It is also observed in Figures 2, 3 and 6 that each spiral 30 may have at its free end a primary connection terminal 32. These primary connection terminals 32 here allow the connection of the primary electrical conductive winding 12 with the high voltage part of the on-board network. Each primary connection terminal 32 comprises, for example, two pads allowing distribution of the current in the connection with the high voltage part of the on-board network.

[0078] It can be seen in Figures 2 and 3 that these primary connection terminals 32 extend here on the same side 33 of the substrate, this side 33 being rectilinear in the example considered.

[0079] We also observe that, from one spiral 30 to the next, the same number of turns is present, this number of turns being here equal to 5.

[0080] In at least a second layer, the secondary electrically conductive winding 22 is in the examples considered an electrically conductive blade having a wavy shape.

[0081] It can be seen in Figures 2, 3 and 5 that, in a stacking axis perpendicular to the plane of Figures 2 and 3 along which the first layer(s) are stacked with the second layer(s), the electrically conductive blade 22 and the electrical track defining two spirals 30 connected in series partially overlap.

[0082] As seen in Figures 2, 3 and 7, the electrically conductive blade may have a W shape when viewed along this stacking axis. This blade here defines two round trips, each round trip comprising two straight parts connected 36 to each other by an angled part 37. In this embodiment, the first round trip extends between a first secondary terminal 38 for connecting the secondary electrically conductive winding to the outside and a second secondary terminal 38 for connecting this secondary electrically conductive winding to the outside. This connection is for example made with the low voltage part of the on-board network. Still in this embodiment, the second round trip extends between the second secondary connection terminal 38 and a third secondary connection terminal 38.

[0083] It is also observed in Figures 1 to 3 that the secondary connection terminals 38 can protrude from the same side 39 of the substrate 5 and which is here rectilinear. This side 39 is opposite the side 33 with respect to which the primary connection terminals 32 protrude.

[0084] It can also be seen in Figure 2 that each straight part 36 of the electrically conductive blade is superimposed on the straight part of a spiral 30 along the stacking axis.

[0085] According to one embodiment, as for example shown schematically in Figure 5, the electrical assembly 10 of the electrical transformer 1 has a stacked structure, according to which a succession of second and first layers, in other words of secondary 22 and primary 12 electrical conductive windings, alternate, in the mass of the substrate 5.

[0086] Thus, with reference to Figure 5, the electrical assembly comprises, incorporated in the mass of the substrate 5, an alternation of second and first layers. The electrical assembly 10 and a ferromagnetic core 6 attached to the electrical assembly 10 form an electrical transformer 1. Each second layer comprises at least one secondary electrically conductive winding portion 22 and each first layer comprises at least one primary winding portion 12. The primary winding portions 12 together form a primary circuit of the electrical transformer 1. The secondary winding portions 22 together form a secondary circuit of the electrical transformer 1. The second layers are separated from the first layers by a substrate thickness 50. In particular, as already indicated previously, the substrate 5 is obtained from prepreg. In particular, the primary winding portions 12 are interconnected with each other by superposition and contact.The secondary winding parts 22 are interconnected with each other by superposition and contact outside the volume of the substrate 5.

[0087] By construction, preferably, there is no air gap between the first and second layers. Preferably, there is no air layer in the mass of the substrate 5. To produce the planar electrical assembly 10, the manufacturing method described below is further proposed.

[0088] First, a first layer is formed comprising a first prepreg sheet on one face of which a primary electrically conductive winding 12 is etched, which is intended to form at least a portion of the primary circuit of the electrical transformer 1. A secondary electrically conductive winding 22 is placed on a prepreg face of the first layer. The secondary electrically conductive winding 22 is intended to form at least a portion of the secondary circuit of the electrical transformer 1. A second prepreg sheet is then deposited on the secondary electrically conductive winding 22.

[0089] In particular, in the formation of the first layer of the substrate 5, a primary electrically conductive winding 12 can be etched on each face of the first prepreg sheet. A third prepreg sheet is then deposited on one face of the first prepreg sheet. After which, the secondary electrically conductive winding 22 is deposited on the free face of said third prepreg sheet.

[0090] For example, the primary circuit has ten turns formed by the primary electrical conductive winding 12 and the secondary circuit has one turn of secondary conductive winding 122. Of course, the transformation ratio, and therefore the number of turns of the primary 12 and secondary 22 electrical conductive windings, is adapted to the desired use.

[0091] These operations are repeated, if necessary, to form a multi-layer substrate base.

[0092] The prepreg layers are pressed together with the primary 12 and secondary 22 electrically conductive windings, and the temperature is increased. Thus compressed, the electrical assembly 10 forms a PCB incorporating the stack of primary 12 and secondary 22 electrically conductive windings, respectively separated and therefore electrically insulated from each other by a thickness 50 obtained from prepreg. At least one free end of the secondary electrically conductive windings 22 projects from the substrate 5 to form an electrical connection terminal 23 of the secondary circuit.

[0093] It is noted that the material for producing the substrate 5, from pre-impregnated material (“prepreg”) in epoxy resin, is chosen from the materials usually used to form PCB substrates. The chosen material has a malleability, in other words a viscosity, suitable for the manufacturing method described above. In particular, it is capable of integrating in its face the primary 12 and secondary 22 electrical conductive windings and of covering them completely. In the manufacturing phase, the different layers are pressed against each other, so that the material of the substrate 5 intrudes over and between the electrical conductive windings, in particular within the first or second layer, so that there is no air layer or air cavity remaining in the mass of the substrate 5 of the electrical assembly 10.Once the planar electrical assembly 10 comprising the stack of at least the second layer and the first layer has been produced, with respectively at least one portion of primary electrically conductive winding 12 and at least one portion of secondary electrically conductive winding 22, the ends of the secondary electrically conductive windings forming secondary electrical connectors 23 are brought into contact, to electrically connect the layers of the stack of secondary electrically conductive windings 22 to each other.

[0094] This gives a monolithic planar electrical assembly 10 integrated into a PCB. To produce a complete electrical transformer 1, it is sufficient to add a ferromagnetic core 6, in particular made of ferrite, to said electrical assembly 10. The ferromagnetic core 6 can be a single piece or comprise two or more elements.

[0095] The planar electrical assembly 10 has the advantage, due to its planar structure, of facilitating its cooling, i.e. the cooling of the at least one primary electrically conductive winding 12 and the at least one secondary electrically conductive winding 22. The monolithic electrical assembly 10 can in fact be easily pressed against a heat dissipation plate 30, in particular a fluid circulation cooling plate, as for example illustrated in FIG. 8. In addition, by being pressed against a heat dissipation plate 30, in particular a fluid circulation cooling plate, the planar electrical assembly 10 also makes it possible to press one face of the core 8 against the heat dissipation plate 30, in particular the fluid circulation cooling plate, to cool the core 8.

[0096] Furthermore, in the case of a stacked structure of several second layers and several first layers, in which the primaries are interposed between the secondaries, better electromagnetic performances are obtained compared to the structures of the prior art.

Claims

Demands 1. Planar electrical assembly (10) comprising a substrate (5), in particular formed from prepreg sheets, and comprising, incorporated into the mass of the substrate (5): - at least one primary electrically conductive winding (12), in a first layer of the substrate (5), and forming at least part of a primary circuit for an electrical transformer (1), and, on the other hand - at least one secondary electrically conductive winding (22), in a second layer of the substrate (5) superimposed on the first layer, and forming at least part of a secondary circuit for the electrical transformer (1) the primary electrically conductive winding (12) being formed of an electrical track defining two spirals (30) connected in series and the secondary electrically conductive winding (22) being formed of an electrically conductive blade having a corrugated shape, in a stacking axis according to which the first layer is stacked with the second layer, the electrically conductive blade (22) and the electrical track defining two spirals (30) connected in series overlapping at least partially.

2. Planar electrical assembly (10) according to claim 1, the two spirals (30) having the same shape and being symmetrical to each other with respect to an axis (X) cutting the substrate.

3. Planar electrical assembly (10) according to any one of the preceding claims, the electrically conductive blade (22) having a W shape when viewed along the stacking axis.

4. Planar electrical assembly (10) according to claim 3, the electrically conductive blade (22) defining two round trips, each round trip comprising two straight parts (36) connected to each other by an angled part (37).

5. Planar electrical assembly (10) according to claim 4, each straight part (36) of the electrically conductive blade being superimposed on the straight part of a spiral (30) of the electrical track in a first layer along the stacking axis.

6. Planar electrical assembly (10) according to claim 4 or 5, the first round trip extending between a first secondary terminal (38) for connecting the externally facing secondary electrical conductive winding (22) and a second secondary terminal (38) for connecting this externally facing secondary electrical conductive winding (22), and the second round trip extending between the second secondary terminal (38) for connecting the externally facing secondary electrical conductive winding (22), and a third secondary terminal (38) connection of the secondary electrical conductor winding (22) to the outside.

7. Planar electrical assembly (10) according to claims 3 and 6, the primary connection terminals (32) projecting from the same first side (33) of the substrate and the secondary connection terminals (38) projecting from the same second side (39) of the substrate, these first (33) and second (39) sides of the substrate being opposite.

8. Planar electrical assembly (10) according to any one of the preceding claims, comprising a plurality of first layers and a plurality of second layers stacked alternately.

9. Planar electrical assembly (10) according to any one of the preceding claims, wherein the substrate (5) is obtained from a stack of several sheets of prepreg, thermoset together.

10. Planar electrical assembly (10) according to claim 9, wherein: - the first layer of the substrate (5) is obtained from at least one first sheet of prepreg on one face of which at least one primary electrically conductive winding (12) is etched, and - the second layer of the substrate (5) is obtained by bringing at least one secondary electrically conductive winding onto a prepreg face of the first layer and covering said secondary electrically conductive winding with a second sheet of prepreg.

11. Planar electrical assembly (10) according to claim 10, wherein: - the first layer of the substrate (5) is obtained from the first sheet of prepreg on each face of which a respective primary electrically conductive winding (12) is engraved, a third sheet of prepreg then covering one face of said first sheet of prepreg; - the second substrate layer (5) is obtained by bringing at least one secondary electrically conductive winding (22) onto the free face of the third prepreg sheet and covering it with said second prepreg sheet.

12. Planar electrical assembly (10) according to any one of the preceding claims, wherein the electrical track of the primary electrically conductive winding (12) has a thickness less than or equal to 0.25 mm; and the electrically conductive blade of the secondary electrically conductive winding (22) has a thickness greater than or equal to 0.4 mm and / or less than 2 mm.

13. Electrical transformer (1) comprising an electrical assembly (10) according to any one of the preceding claims, and a ferromagnetic core (6) attached to said substrate (5) so as to magnetically couple the primary electrically conductive windings (12) with the secondary electrically conductive windings (22).

14. A method for manufacturing an electrical assembly (10) comprising a primary circuit and a secondary circuit, said method comprising the following steps: - a first layer is formed comprising a first sheet of prepreg on one face of which a primary electrically conductive winding (12) is etched, said primary electrically conductive winding being intended to form at least part of a primary circuit of a electrical transformer (1), this primary electrically conductive winding (12) being formed of an electrical track defining two spirals connected in series; - we have a monolithic electrical conductor, called the secondary electrical conductor winding, this secondary electrical conductor winding (22) being formed of an electrically conductive blade having a corrugated shape; - the secondary electrical conductive winding (22) is deposited on a prepreg face of the first layer, said secondary electrical conductive winding (22) being intended to form at least part of a secondary circuit of the electrical transformer (1); - a second sheet of pre-impregnated material is placed on top; - the entire prepreg sheet and the primary (12) and secondary (22) electrically conductive windings are pressed and heated, so as to assemble the said sheets together along a stacking axis and to form the electrical assembly (10) comprising the stack of primary (12) and secondary (22) electrically conductive windings, and so that in the stacking axis, the electrically conductive blade (22) and the electrical track defining two spirals connected in series overlap at least partially.

15. Method according to claim 14, wherein: in the formation of the first layer of the substrate (5), a respective primary electrically conductive winding (12) is engraved on both faces of the first prepreg sheet, then a third prepreg sheet is deposited on one face of the first prepreg sheet, then the secondary electrically conductive winding (22) is deposited on the free face of said third prepreg sheet.

16. Method according to claim 14 or 15, wherein a ferromagnetic core (6) is brought onto the substrate (5), so as to magnetically couple the primary electrically conductive windings (12) with the secondary electrically conductive windings (22) and form an electrical transformer (1).

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