System comprising a transformer and a heat sink

Abstract

The invention relates to a system comprising a heat sink (200) and a transformer (100), the transformer comprising an electronic circuit board (102) comprising an electrically conductive track, a first rigid electrical conductor (104, 106), a primary including at least the electrically conductive track of the electronic circuit board (102), a secondary including at least the first rigid electrical conductor (104, 106), and an electromagnetic coupling core (108) for electromagnetically coupling the primary to the secondary, the first rigid electrical conductor (104) comprising at least one open loop around a central leg (108C) of the electromagnetic coupling core (108) and at least one thermal connection (1041), the thermal connection (104) extending from the open loop towards the exterior of the open loop, the thermal connection (1041) being in thermal contact with the heat sink (200).

Description

Description TITLE: SYSTEM COMPRISING A TRANSFORMER AND A HEAT DISSIPATOR Technical field of the invention

[0001] The present invention relates to a system comprising a transformer and a heat sink.

[0002] The present invention also relates to a voltage converter, comprising such a system as well as a mobility device comprising such a system or such a voltage converter.

[0003] A mobility device is, for example, a motorized land vehicle, a train, an aircraft, or a drone. A motorized land vehicle is, for example, a car, a motorcycle, a motorized bicycle, or a motorized wheelchair.

[0004] The present invention can be applied in particular in the field of hybrid or electric motor vehicles. Technological background

[0005] A system comprising a heat sink and a transformer is known from the prior art, said transformer comprising: an electronic circuit board with an electrically conductive trace; a first rigid electrical conductor; a primary including at least the electrically conductive trace of the electronic circuit board; a secondary conductor including at least the first rigid electrical conductor; and an electromagnetic coupling core of the primary and secondary windings.

[0006] In the prior art, the first rigid electrical conductor of the transformer comprises at least one open loop around a central leg of the electromagnetic coupling core, and the transformer is cooled by bringing the open loop of the first rigid electrical conductor into thermal contact with the heat sink. However, when the transformer When the transformer is functioning, the open loop of the first rigid electrical conductor carries alternating currents which, particularly with high-frequency alternating currents and due to the interface with the heat sink, cause skin currents. These skin currents result in significant energy losses that negatively impact the transformer's efficiency.

[0007] By "open loop around a central leg" is meant that a part of the first rigid electrical conductor forms a curve, preferably planar, around the central leg, said curve not closing on itself.

[0008] By "high frequency currents" we mean alternating electrical currents with a frequency greater than 20kHz, or even greater than 100kHz.

[0009] By "thermal contact between part A and part B", we mean direct thermal and mechanical contact between the two parts or mechanical and thermal contact between the two parts through a thermally conductive and electrically insulating material.

[0010] It may therefore be desirable to provide a system that allows us to overcome at least part of the aforementioned problem. Summary of the invention

[0011] According to a first aspect of the invention, a system comprising a heat sink and a transformer is therefore proposed, said transformer comprising: an electronic circuit board with an electrically conductive trace; a first rigid electrical conductor; a primary including at least the electrically conductive trace of the electronic circuit board; a secondary conductor including at least the first rigid electrical conductor; and an electromagnetic coupling core of the primary and secondary windings; the first rigid electrical conductor comprising at least one open loop around a central leg of the electromagnetic coupling core and at least one thermal connection, said thermal connection extending from said open loop to the outside of said open loop, said thermal connection being in thermal contact with said heat sink.

[0012] Thus, thanks to the thermal connection, the thermal and mechanical interface between the heat sink and the first rigid electrical conductor is made on a portion of the first rigid electrical conductor which is not traversed by alternating currents, which reduces, or even eliminates, the occurrence of skin current and consequently improves the energy efficiency of the transformer.

[0013] The invention may further include one or more of the following optional features, in any technically feasible combination.

[0014] Optionally, the transformer is a planar transformer, that is, a transformer that uses flat windings, instead of conductive wires, for example copper.

[0015] Optionally, the open loop is also U-shaped.

[0016] Optionally, the electronic circuit board also includes a first opening and the heat sink includes a plate and a flange, a portion of the flange being fixed to a first base of the plate, at least a part of said base and / or said portion of the flange being inserted into the first opening of the electronic circuit board, said thermal connection being in thermal contact with said flange and / or said first base.

[0017] Optionally, the flange is also in thermal contact with said electromagnetic coupling core.

[0018] Optionally, the electromagnetic coupling core also includes a side leg, a portion of the open loop is located between the side leg and the central leg of the electromagnetic coupling core, and at least a portion of said base and / or said portion of the flange is inserted into the first opening of the electronic circuit board, said at least a portion of said base and / or said portion of the flange is in thermal contact with said side leg.

[0019] Optionally, the electromagnetic coupling core is also in thermal contact with said plate.

[0020] Optionally, the heat sink includes a second rigid electrical conductor, the first and second rigid electrical conductors being located on either side of said electronic circuit board, said secondary of said transformer also including the second rigid electrical conductor, the second rigid electrical conductor including at least one thermal connection, said thermal connection of said second rigid electrical conductor being in thermal contact with said heat sink.

[0021] Optionally, the thermal connection of the second rigid electrical conductor is in thermal contact with a second base of said plate.

[0022] Optionally, the heat sink also includes a plate, said thermal connection being in thermal contact with a base of said plate.

[0023] According to a second aspect of the invention, a voltage converter is also proposed comprising a system according to the first aspect of the invention.

[0024] According to a third aspect of the invention, a mobility device is also proposed comprising a system according to the first aspect of the invention or a voltage converter according to the second aspect of the invention. Brief description of the figures

[0025] The invention will be better understood with the aid of the following description, given solely by way of example and made with reference to the accompanying drawings in which: Figure 1 is a view of a system comprising a heat sink thermally coupled to a transformer according to the invention; Figure 2 is a view of the transformer of the system of Figure 1; Figure 3 is a view of the transformer of Figure 2 without the electromagnetic coupling core of the primary and secondary windings. Figure 4 is a schematic view of another possible shape of the first rigid electrical conductor of the transformer in Figure 2. Figure 5 is a view of the electromagnetic coupling core of the primary and secondary windings of the transformer shown in Figure 2. Figure 6 is a view of the metallic support for the two rigid electrical conductors and the electronic circuit board of the transformer shown in Figure 2. Figure 7 shows the two rigid electrical conductors of the transformer in Figure 2 and plate 202 of the heat sink system in Figure 1, and Figure 8 is a schematic view of yet another possible form of the first rigid electrical conductor of the transformer in Figure 2. Detailed description of the invention

[0026] Figure 1 represents a first embodiment of a 300 system intended to equip, for example, a DC / DC voltage converter of an electric vehicle.

[0027] The system 300 comprises a transformer 100 according to the invention and a heat sink 200, the heat sink 200 being in thermal contact with the transformer 100 to cool the transformer 100.

[0028] Thermal contact between the transformer 100 and the heat sink is achieved either directly or via a thermally conductive and, preferably, electrically insulating material C. For example, the thermally conductive material C is advantageously a thermal grease, a thermal adhesive, or a thermal paste (also known as a gap filler).

[0029] The thermal conductivity of material C is, for example, between 1 and 4 Ω. 1 K -1 preferably between 3 and 4 w nr 1K -1 and / or the dielectric strength is between 200 and 400 V / m, preferably between 200 and 300 V / m.

[0030] With reference to Figure 2 and Figure 3, transformer 100 will now be described.

[0031] Transformer 100 is, in the example described here, a planar transformer, which has a stacking of parts in an arbitrary direction BH (for Bottom-Top) taken as the vertical direction.

[0032] The stack first includes an electronic circuit board bearing the reference 102 and extending in a principal plane perpendicular to the direction BH.

[0033] The electronic circuit board 102 includes an electrical insulating plate 102A having a top face 102A sup and a lower face 102Aj n f opposite each other. The 102A electrical insulating plate, for example, contains a prepreg (from the English "prepreg") or an FR4 PCB.

[0034] The electronic circuit board 102 further comprises at least one electrically conductive trace 102B extending along one of its upper face 102A sup and the lower face 102Aj n f of the electrical insulating plate 102A. Track 102B is for example made of copper.

[0035] For example, the electronic circuit board 102 has a thickness of at most 2 mm, for example 1.3 mm.

[0036] The stack also includes at least one rigid electrical conductor (from the English "busbar"), preferably flat. In the example shown here, the stack includes a first rigid electrical conductor 104 and a second rigid electrical conductor 106. The two rigid electrical conductors 104 and 106 are each located on opposite sides of the electronic circuit board 102.

[0037] Each rigid electrical conductor is, for example, made of copper. Each rigid electrical conductor extends, for example, in a plane perpendicular to the direction BH and parallel to the main plane defined by the electronic circuit board 102.

[0038] In addition, the rigid electrical conductors 104, 106 each have a thickness of between 1 mm and 3 mm, preferably between 1 mm and 2 mm.

[0039] In the example described here, the rigid electrical conductors 104, 106 have an axis of symmetry.

[0040] To insulate the rigid electrical conductors 104 and 106 from the trace of the electronic circuit board 102, the transformer 100 may further include at least one electrical insulation film (not shown in Figures 1 and 2). In particular, the transformer 100 may further include as many electrical insulation films as there are rigid electrical conductors 104, 106, each insulation film electrical thus being interposed between a rigid electrical conductor 104, 106 and the electronic circuit board 102.

[0041] Optionally, the electrical insulation film interposed between the electrically conductive track of the electronic circuit board and the rigid electrical conductor 104, 106 comprises an electrically insulating layer and two adhesive layers on two opposite faces of the insulating layer, the two adhesive layers being pressed against the electrically conductive track 102B of the electronic circuit board 102 and the rigid electrical conductor 104, 106, respectively. Thus, in addition to providing electrical insulation, the electrical insulation films also allow the electronic circuit board 102 and the rigid electrical conductors 104, 106 to be held together to form a unit block that is easier to handle.

[0042] Alternatively, the electrical insulation film interposed between the electrically conductive track of the electronic circuit board 102 and the rigid electrical conductor 104, 106 can be replaced by a rigid insulating piece, for example made of plastic, interposed and fixed between the rigid electrical conductor 104, 106 and the electrically conductive track of the electronic circuit board 102.

[0043] The transformer 100 further includes a primary P including at least the electrically conductive track 102B of the electronic circuit board 102 and a secondary S including at least a first rigid electrical conductor 104, 106.

[0044] In the example described here, the secondary of transformer 100 comprises the two rigid electrical conductors 104, 106.

[0045] The transformer 100 further comprises an electromagnetic coupling core 108 of the primary and secondary described with reference to Figure 5. The electromagnetic coupling core 108 is for example made of ferromagnetic material.

[0046] In the example described here, this electromagnetic coupling core 108 comprises, in the stack, an upper part 108A and a lower part 108B, framing the electronic circuit board 102 and the rigid electrical conductors 104, 106. The electromagnetic coupling core 108 generally includes vertical portions (references 108C, 10D and 108 E (in figure 5) passing through the electronic circuit board 102 through openings Oi, O2, O3 made in the latter for this purpose.

[0047] The electromagnetic coupling core 108 comprises, in the example described here, a central leg 108C around which an open loop of each of the two electrical conductors 104 and 106 is at least partially wound. In other words, each of the two rigid electrical conductors comprises at least one open loop around the central leg 108C of the electromagnetic coupling core 108. In the example described here, the open loop is U-shaped.

[0048] Furthermore, the central leg 1080 is located at the axis of symmetry of the rigid electrical conductors 104, 106 and passes through the electronic circuit board 102 through the opening Oi.

[0049] The electromagnetic coupling core 108 further comprises, in the example described here, a first lateral leg 108D and a portion of the open loop of each of the rigid electrical conductors 104, 106 is located between the first lateral leg 108D and the central leg 108C of the electromagnetic coupling core 108. The electromagnetic coupling core 108 also comprises a second lateral leg 108E and a portion of the open loop of each of the rigid electrical conductors 104, 106 is located between the second lateral leg 108E and the central leg 108C of the electromagnetic coupling core 108. Moreover, the first lateral leg 108D (respectively the second lateral leg 108E) passes through the electronic circuit board 102 via the opening O2 (respectively via the opening O3).

[0050] In the example described here and as shown in Figure 3, the rigid conductor 104 has two thermal connections 104i and 1042. The thermal connection 104i comprises a first portion 104i-i intended to be in thermal contact with the heat sink 200 and a second portion 104i-2 connecting the first portion 104i-i to the open loop of the rigid conductor 104. Similarly, the thermal connection 1042 comprises a first portion 1042-1 intended to be in thermal contact with the heat sink 200 and a second portion 1042-2 connecting the first portion 1042-1 to the open loop of the rigid conductor 104. Each of the two thermal connections 104i and 1042 extends outward from the open loop in the plane defined by the rigid electrical conductor 104, that is, in a plane substantially parallel to the principal plane defined by the electronic circuit board 102. In the example described here, where the open loop is in in the shape of a "U", the two thermal connections 104i, 1042 extend from the base of this "U".

[0051] Similarly, in the example described here, the rigid conductor 106 has two thermal connections 1061 and 1062. The thermal connection 106i comprises a first part 1061-1 intended to be in thermal contact with the heat sink 200 and a second part 106i_2 connecting the first part 1061-1 to the open loop of the rigid conductor 106. Likewise, the thermal connection 1062 comprises a first part 1062-1 intended to be in thermal contact with the heat sink 200 and a second part 106 2.2connecting the first part 1062-i to the open loop of the rigid conductor 106. Each of the two thermal connections 1061 and 1062 extends, outwards from the open loop, in the plane defined by the rigid electrical conductor 106, that is to say in a plane substantially parallel to the main plane defined by the electronic circuit board 102. In the example described here, where the open loop is in the shape of a "U", the two thermal connections 1061, 1062 extend from the base of this "U".

[0052] In the example described here, the assembly formed by the two parts of each electrical connection 104i, 1042, 106i and 1062 is L-shaped.

[0053] Alternatively, as shown schematically in Figure 4, the assembly formed by the two parts of each electrical connection 104i, 1042, 1061 and 1062 is T-shaped.

[0054] Furthermore, in the example of Figure 4, the first part 104i.-i, 1 O42.I and the second part 104I.2, 104 2.2 of each of the thermal connections 104i , 1042 have substantially rectangular shapes and extend in the same plane, but along different axes (the axes being the perpendicular bisectors of the two shortest sides of the rectangles represented in dotted lines).

[0055] In addition, each of the first parts 104i-i, 1 O42.I, 1061-1 and 1O62.I has a free end, i.e. not connected to another part of the rigid electrical connector to which it belongs.

[0056] Moreover, in the example described here, the first part (respectively the second part) of each of the thermal connections extends substantially parallel (respectively substantially perpendicular) to the lateral legs 108D, 108E and to the central leg 108C.

[0057] The two rigid electrical conductors 104, 106 are intended to be electrically connected together, for example by means of two screws 150, 160 or an equivalent fastening method, such as studs. The two screws 150, 160 thus constitute the two electrical supply terminals of the secondary winding S of the electrical transformer 100.

[0058] Furthermore, in the example described here and with reference to Figure 6, the two screws 150, 160 mechanically hold together the two rigid electrical conductors 104, 106 and the electronic circuit board 102.

[0059] Furthermore, for each screw, two connectors are soldered onto the electronic circuit board 102. These connectors are formed, for example, by conductive inserts of the nut or pin type. Thus, the screw 160 passes successively, in the vertical direction HB, through an opening in the rigid electrical conductor 104, through the first insert R1, through an opening in the electronic circuit board 102, through the second insert R2, and through an opening in the rigid electrical conductor 106 before being fixed to a nut E1.Thus, each of the two inserts is interposed between a rigid electrical conductor and the electronic circuit board 102, which not only ensures spacing between the rigid electrical conductor and the electronic circuit board 102, but also ensures an electrical connection between the rigid electrical conductor and a trace of the electronic circuit board 102 when part of the secondary of the transformer 100 is routed to the electronic circuit board 102.

[0060] As shown in Figure 1, the heat sink 200 includes a plate 202.

[0061] Plate 202 is for example the bottom of a case (not shown in Figure 1), for example made of aluminum, inside which transformer 100 is positioned so that transformer 100 is in thermal contact with plate 202.

[0062] In the example described here, the plate 202 includes in its thickness a cooling channel (not shown) in which a coolant, for example water or ethylene glycol, circulates, intended to cool the transformer 100.

[0063] Alternatively, plate 202 includes on its external face (i.e. outside the case) fins separated by a space to allow the passage of an airflow between them in order to cool transformer 100.

[0064] As can be seen in Figure 1, the lower part 108B of the electromagnetic coupling core 108 is in thermal contact, for example via material C, with the plate 202.

[0065] The heat sink 200 also includes a flange 201. A first portion of the flange 201 is fixed to a base 203 of the plate 202 while a second portion of the flange 201 is fixed to a base 204 of the plate 202. The fixing of the flange 201 to the bases 203, 204 of the plate 202 is for example achieved by means of screws passing through smooth openings in the flange 201 to screw into threaded holes in the bases 203, 204.

[0066] In the example described here, part of the base 203 (respectively of the base 204) is inserted into the opening O3 (respectively into the opening O2) of the electronic circuit board 102.

[0067] The flange 201 is not only in thermal contact, for example via material C, with the upper face of the upper part 108A of the electromagnetic coupling core 108, but also with the upper part of the first part 104M of the thermal connection 104i of the first rigid electrical conductor 104 and with the upper part of the first part 1042-I of the thermal connection 1042 of the first rigid electrical conductor 104. Thus, thanks to the thermal connections 104i and 1042, the thermal and mechanical interface between the heat sink 200, via the flange 201, and the first rigid electrical conductor 104 is achieved on a portion of the first rigid electrical conductor 104 that is not traversed by alternating currents, which reduces, or even eliminates, the occurrence of skin current and consequently improves the energy efficiency of the transformer 100.

[0068] In addition, the part of the base 203 (respectively of the base 204) inserted in the opening O3 (respectively in the opening O2) is also in thermal contact, for example via the material C, with the lateral leg 108E (respectively the lateral leg 108D) of the electromagnetic coupling core 108.

[0069] Referring to Figure 7, the plate 202 of the heat sink 200 further comprises two bases 205, 206. These two bases 205, 206 are in thermal contact, for example via material C, with the lower part of the first section IO61-1 of the thermal connection 1061 of the second rigid electrical conductor 106 and with the lower part of the first section IO62-1 of the thermal connection 1062 of the second rigid electrical conductor 106. Thus, thanks to the thermal connections IO61 and 1062, the thermal and mechanical interface between the heat sink 200, via the bases 205, 206, and the second rigid electrical conductor 106 is established on a portion of the second rigid electrical conductor 106 that is not carrying alternating currents, which reduces, or even eliminates, the occurrence of skin currents and consequently improves the energy efficiency of the transformer 100.

[0070] In the example described here, the bases 203, 204, 205, 206 are made in the form of walls or protrusions projecting from the plate 202 towards the inside of the box of which the plate 202 is the bottom, i.e. towards the transformer 100. In particular, the bases 205, 206 project towards the lower part (in the vertical direction BH) of the thermal connection of the second rigid electrical conductor 106.

[0071] It should also be noted that the invention is not limited to the embodiments described above. Indeed, it will be apparent to those skilled in the art that various modifications can be made to the embodiments described above, in light of the information just disclosed to them.

[0072] For example, the electronic circuit board 102 may be a multilayer board, and the electrical conductive trace 102B may be located on an internal layer of the electronic circuit board instead of extending across one of the top faces 102A sup and the lower face 102Aj n f of the 102A electrical insulating plate.

[0073] In another example, the stack may include several electronic circuit boards extending one above the other in a principal plane perpendicular to the BH direction. Furthermore, these electronic circuit boards may include openings through which the vertical portions of the electromagnetic coupling core 108 pass, and / or a rigid electrical conductor may be interposed between at least two adjacent electronic circuit boards along the BH direction.

[0074] In yet another example, a portion of the flange 201 is inserted into the Os opening of the electronic circuit board 102 instead of the base 203. Similarly, another portion of the flange 201 can be inserted into the O2 opening of the electronic circuit board 102 instead of the base 204.

[0075] In yet another example, the thermal connection 104i (respectively 1042) of the first rigid electrical conductor 104 is in thermal contact, via the material C, with the base 203 (respectively the base 204) without passing through the flange 201.

[0076] In yet another example shown in Figure 8, the first part 104-1-1 extends substantially perpendicularly to the lateral leg 108D and / or the central leg 108C and the second part 104I-2 extends substantially parallel to the lateral leg 108D and / or the central leg 108C.

[0077] In yet another example, the 300 system is intended to equip not a DC / DC voltage converter, but a DC / AC or AC / DC voltage converter of an electric vehicle.

[0078] In the detailed presentation of the invention given above, the terms used shall not be interpreted as limiting the invention to the embodiments set forth in this description, but shall be interpreted as including all equivalents which can be foreseen by a person skilled in the art by applying their general knowledge to the implementation of the teaching which has just been disclosed to them.

Claims

Demands [1] System comprising a heat sink (200) and a transformer (100), said transformer comprising: an electronic circuit board (102) comprising an electrically conductive track; a first rigid electrical conductor (104, 106); a primary including at least the electrically conductive trace of the electronic circuit board (102); a secondary including at least the first rigid electrical conductor (104, 106); and an electromagnetic coupling core (108) of the primary and secondary; the first rigid electrical conductor (104, 106) comprising at least one open loop around a central leg (108C) of the electromagnetic coupling core (108) and at least one thermal connection (104i, 1061), said thermal connection (104i, 1061) extending from said open loop outwards from said open loop, said thermal connection (104i, 1061) being in thermal contact with said heat sink (200). [2] System according to claim 1 wherein said electronic circuit board (102) further comprises a first opening (03) and wherein said heat sink (200) comprises a plate (202) and a flange (201), a portion of the flange (201) being fixed to a first base (203) of the plate, at least a part of said base (203) and / or of said portion of the flange (201) being inserted into the first opening (03) of the electronic circuit board, said thermal connection (104i) being in thermal contact with said flange (201) and / or said first base (203). [3] System according to the preceding claim in which said flange (201) is in thermal contact with said electromagnetic coupling core (108). [4] A system according to any one of claims 2 to 3, wherein the electromagnetic coupling core (108) further comprises a lateral leg (108E), wherein a portion of the open loop is located between the lateral leg (108E) and the central leg (108C) of the electromagnetic coupling core (108), and in of which at least a part of said base (203) and / or of said portion of the flange (201) is inserted into the first opening (03) of the electronic circuit board (102), said at least a part of said base (203) and / or of said portion of the flange (201) is in thermal contact with said side leg (108E). [5] System according to any one of claims 2 to 4 wherein the electromagnetic coupling core (108) is in thermal contact with said plate (202). [6] System according to any one of claims 1 to 5 wherein said heat sink (200) comprises a second rigid electrical conductor (106), the first (104) and the second rigid electrical conductor (106) being located on either side of said electronic circuit board (102), said secondary of said transformer (100) also including the second rigid electrical conductor (106), the second rigid electrical conductor (106) comprising at least one thermal connection (1061), said thermal connection (106i) of said second rigid electrical conductor (106) being in thermal contact with said heat sink. [7] System according to the preceding claim in which said thermal connection (1061) of said second rigid electrical conductor (106) is in thermal contact with a second base (205) of said plate (202). [8] System according to claim 1 in which said heat sink (200) comprises a plate (202), said thermal connection (1061) being in thermal contact with a base (205) of said plate (202). [9] Voltage converter comprising a system according to any one of claims 1 to 8. [10] Mobility device, for example a vehicle, comprising a system according to any one of claims 1 to 8 or a voltage converter according to claim 9.

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