Load converter for converting an alternating current into a low-voltage direct current

Abstract

The invention relates to a load converter for converting an alternating current into a low-voltage direct current, the load converter comprising a transformer (100) comprising: - a plurality of adjacent cells (C1, C2, C3, C4), - a magnetic core (110) comprising a first leg (111, 121, 131, 141) and a second leg (112, 122, 132, 142) per cell, and in each cell (C1, C2, C3, C4): a primary winding (10), a secondary winding (20) and a tertiary winding (30) wound around the first leg and one of the primary winding and the secondary winding wound around the second leg, and an inductor (40) connected in series; the primary winding (10), and respectively the secondary winding (20), of one cell being connected in series with the primary winding, and respectively the secondary winding, of an adjacent cell, and the tertiary winding (30) of one cell being connected in parallel with the tertiary winding of the adjacent cell.

Description

[0001] DESCRIPTION

[0002] Title of the invention ■ Load converter for converting alternating current into low-voltage direct current

[0003] The present invention relates to the field of load converters for current conversion intended for use in electric or hybrid vehicles. More particularly, the invention relates to a converter for converting alternating current into low-voltage direct current.

[0004] An electric or hybrid vehicle includes an electric drive system and several auxiliary electrical components (such as the on-board computer, audio system, headlights, etc.). The electric drive system is powered by a high-voltage battery (typically between 100 and 900V). The auxiliary components are powered by a low-voltage battery (typically 12, 24, or 48V).

[0005] To ensure the charging of the high-voltage power supply battery and the low-voltage power supply battery, the vehicle is equipped with two converters.

[0006] The first converter is an on-board charger (also known as an OBC) which receives alternating current (AC) as input from an external power grid. The on-board charger outputs high-voltage direct current (DC).

[0007] The onboard charger comprises two magnetic power components: a power inductor, which is part of the circuit that converts alternating current (AC) to high-voltage direct current (DC), and a high-frequency transformer that transforms the high-voltage DC into isolated high-voltage DC (also called an isolated DC-DC HV-HV transformer). The onboard charger recharges the high-voltage power supply battery.

[0008] The second converter is a DC-DC converter that converts the isolated high-voltage direct current from the onboard charger into a low-voltage direct current (also called isolated high-voltage DC-DC). It includes a high-frequency transformer. This second DC-DC converter powers the low-voltage battery to supply the vehicle's auxiliary equipment, i.e., low-power equipment such as the onboard computer, headlights, etc.

[0009] Until now, the on-board charger and the DC-DC converter were installed in the vehicle as two separate, interconnected units, each with its own housing. For the sake of compactness, new solutions have emerged on the market in which the on-board charger and the DC-DC converter are housed in a single unit. This notably reduces the vehicle's overall size.

[0010] More specifically, in such a product of these new solutions, the onboard charger, which includes several magnetic components, and the DC-DC converter are integrated into a single housing. This is a rather complex mechatronic integration. While such a solution can be deployed quickly because the component parts already exist, the final product has high production costs and poor repeatability in the assembly process. Existing solutions are therefore not entirely satisfactory.

[0011] To improve this type of converter, it is desirable to reduce the number of semiconductors while ensuring a good level of current conversion performance, if possible with a reduced mass and size of the converter.

[0012] The present invention falls within this context and aims to provide a load converter to convert an alternating current into a low voltage direct current combining the functions of an on-board charger and an easy-to-manufacture DC-DC converter, comprising few parts and modular in terms of available power.

[0013] To this end, the invention relates to a load converter for converting alternating current into low voltage direct current and high voltage direct current, comprising an alternating current to direct current converter and a transformer for converting direct current into low voltage direct current and high voltage direct current, characterized in that the transformer comprises: a plurality of adjacent cells, a magnetic core comprising a first leg and a second leg per cell, and in each cell: a primary winding, a secondary winding and a tertiary winding wound around the first leg and one among the primary winding and the secondary winding wound around the second leg and an inductor connected in series;and in that the primary winding, respectively the secondary winding, of a cell is connected in series with the primary winding, respectively the secondary winding, of an adjacent cell, and the tertiary winding of a cell is connected in parallel with the tertiary winding of the adjacent cell.;

[0014] Magnetic components are an important element in a load converter. Market requirements for power transmission are evolving. There is a desire to deliver more power while simultaneously miniaturizing the size of magnetic components. Furthermore, component assembly methods must be as simple as possible to reduce manufacturing costs. The converter of the invention meets all these requirements, as will become apparent from the description of the invention.

[0015] Thanks to the characteristics of the charge converter of the invention, the two high-frequency transformers of the on-board charger and the DC-DC converter are cleverly integrated into a single transformer. In other words, instead of having two high-frequency transformers as is the case in prior art solutions, the invention uses only one transformer with an innovative winding arrangement.

[0016] In the invention, the transformer is divided into several cells. On the high-voltage side, for the primary and secondary windings, the cells are connected in series. On the low-voltage side, for the tertiary winding, the cells are connected in parallel. Since the currents are higher, this parallel connection reduces copper losses in the windings.

[0017] Such a converter combines the transformer and the inductor. This results in a considerable reduction in the size of the components. The converter of the invention has the advantages of being small, lightweight, and easy to assemble.

[0018] In the load converter of the invention, the transformer comprises several cells. Each cell can provide a predetermined power, for example, 1 kW (kilowatt). It is thus possible to adapt the number of cells in the transformer according to the required output power of the converter. Since market demand is for a converter output power of 2 kW, the transformer in this case comprises at least two cells. The number of cells is a compromise between the maximum required output power and the converter's size. This number of cells could be, for example, six. The invention will be described hereafter with a non-limiting example of four cells.

[0019] According to an optional feature of the invention, the first and second legs are parallel to each other. The magnetic core extends between a lower wall and an upper wall, both in an XY plane of an orthonormal coordinate system defined by the X, Y, and Z axes. The lower and upper walls are parallel to each other. The magnetic core also includes two lateral walls that delimit it. The lateral walls extend between the lower and upper walls, perpendicular to the lower and upper walls. The lateral walls extend perpendicularly to the XY plane. In other words, they extend in an XZ plane.

[0020] The first and second legs extend from the bottom wall, perpendicular to it and parallel to the side walls. Each cell comprises a first and a second leg that are aligned. The cells are arranged side by side, parallel to each other. In other words, the cells are distributed between the two side walls of the magnetic core. Consequently, the first and second legs are parallel to each other within the same cell, and the first and second legs of different cells are also parallel to each other.

[0021] This parallel arrangement of the legs allows the primary, secondary, and tertiary windings of the transformer to be wound around the legs. In all embodiments of the invention, the primary, secondary, and tertiary windings are wound around the first legs. Depending on the embodiment considered, either the primary or secondary winding is wound around the second legs.

[0022] According to an optional feature of the invention, the primary, secondary, and tertiary windings are wound in a first direction within one cell and in a second direction, opposite to the first, in the adjacent cell. For example, to generate the desired inductance, the secondary winding must encircle the first and second legs of each cell. However, the winding around the legs in one cell is carried out in one direction, and the winding around the legs in the adjacent cell must be carried out in the opposite direction in order to generate a magnetic flux on the opposing magnetic material. This helps to reduce losses in the core in general at the transformer level.

[0023] According to an optional feature of the invention, the primary and secondary windings are interlaced around the first leg of each cell to form a primary interlacing, and the tertiary winding is wound on either side of the primary interlacing. This specific stacking is used to reduce copper losses in the component.

[0024] According to an optional feature of the invention, the transformer further comprises, in each cell, a shielding layer wound on either side of the main winding, between the main winding and the tertiary winding. The shielding layer may be made of copper traces. The shielding layer is connected to the product's ground. This improves performance in terms of electromagnetic noise.

[0025] According to an optional feature of the invention, the tertiary winding being the first tertiary winding, the transformer further comprises a second tertiary winding, the second tertiary winding of a cell being connected in parallel with the second tertiary winding of the adjacent cell, and the first tertiary winding is wound on one part of the main lay and the second tertiary winding is wound on the other part of the main lay.

[0026] The presence of the two tertiary windings around the primary and secondary windings allows for a balancing of the current in the two tertiary windings.

[0027] According to an optional feature of the invention, each of the windings being wound around a leg in a plurality of layers, the transformer comprises an electronic board having openings and superimposed tracks wound around the openings, the tracks forming the windings and each leg passing through an opening of the electronic board.

[0028] Thanks to electronic board technology, it is easy to implement the interlacing according to the specific arrangement of the invention, while still allowing for high power density. The electronic board contains all the transformer windings. Depending on the winding configuration, the same trace is wound around the openings of the electronic board. The stacking of the windings is made possible by vias that allow the connection between the different layers of the electronic board.

[0029] According to an optional feature of the invention, the magnetic core comprises: a lower wall from which the legs rise to a leg height, two lateral walls rising from the lower wall to a wall height greater than or equal to the leg height, and an upper wall in contact with the two lateral walls.

[0030] This arrangement of the magnetic core with first and second legs allows for windings around the legs with minimal bulk. Such a magnetic core is also easily adaptable to the required output power of the converter.

[0031] According to an optional feature of the invention, the wall height of the two side walls is greater than the leg height of the legs. This means that the upper surface of the first and second legs does not come into contact with the upper wall of the magnetic core. There is therefore a gap between the upper end of the legs and the upper wall of the core. The height of this gap can be adjusted to define an air gap. For example, epoxy resin can be applied to the upper end of the legs to adjust the height of the gap. A series of layers of epoxy resin and ferrite can thus be used. This variation in the height of the gap reduces copper losses in the windings around the legs and affects the resulting inductance value.

[0032] The invention also covers a motor vehicle comprising an on-board network configured to be powered by low-voltage direct current, the vehicle being configured to be connected to an alternating current network, the motor vehicle comprising such a load converter.

[0033] Other features and advantages of the invention will become apparent from the following description on the one hand, and from several illustrative and non-limiting examples of embodiments given with reference to the attached schematic drawings on the other hand, in which:

[0034] [Fig. 1] schematically represents a charge converter capable of converting an alternating current into a low-voltage direct current and into a high-voltage direct current according to the invention.

[0035] [Fig. 2] schematically represents a cross-sectional view of the magnetic core of the converter of the invention,

[0036] [Fig. 3] schematically represents one embodiment of the windings in the converter of the invention,

[0037] [Fig. 4] schematically represents a cross-sectional view of the magnetic core of the converter of the invention, indicating the directions of the windings.

[0038] [Fig. 5] schematically represents another embodiment of the windings in the converter of the invention,

[0039] [Fig. 6] schematically represents another embodiment of the windings in the converter of the invention,

[0040] [fig 7] schematically represents another embodiment of the windings in the converter of the invention,

[0041] [Fig. 8] schematically represents a view of the complete magnetic core of the converter of the invention,

[0042] [fig 9] schematically represents a motor vehicle comprising a converter of the invention.

[0043] The features, variations, and different embodiments of the invention, as described or as they will be presented in the detailed description that follows, can be combined in various ways, provided they are not incompatible or mutually exclusive. In particular, variations of the invention may be conceived comprising only a selection of features, described hereafter in isolation from the other described features, if this selection of features is sufficient to confer a technical advantage and / or to differentiate the invention from the prior art. For clarity, the same elements are designated by the same reference numerals in the various figures.

[0044] Figure 1 schematically represents a load converter 300 capable of converting alternating current (AC) into low-voltage direct current (DC) and high-voltage direct current according to the invention. The load converter 300 comprises an AC-to-DC converter 310 and a transformer 100 for converting the DC output from converter 310 into low-voltage DC and high-voltage DC. As will become apparent from the description of the invention below, the converter of the invention combines the functionality of an on-board charger with that of a DC-DC converter by combining the transformers of the on-board charger and the DC-DC converter.To do this, it includes cells, a magnetic core and a particular arrangement of high voltage windings (primary and secondary windings) and low voltage windings (tertiary windings) explained below.

[0045] As shown in Figure 1, converter 310 receives an alternating current (AC) input. It is an AC / DC converter that includes a power factor corrector (PFC). A capacitive filtering device 311, also called a link capacitor, is connected to the output of converter 310. The capacitive filtering device 311 smooths the DC voltage supplied to transformer 100. Transformer 100 transforms this DC voltage into two DC voltages: a high voltage and a low voltage. Transformer 100 is described in detail below.

[0046] Figure 2 schematically represents an isometric view of the magnetic core 110 and a cross-sectional view in the transverse XY plane of the magnetic core 110 of the transformer 100 of the converter of the invention.

[0047] In the embodiment illustrated in Figure 2, the transformer comprises four cells C1, C2, C3, and C4. This is an illustrative example, and a different number of cells does not depart from the scope of the invention. Each cell delivers a specific power, for example, 1 kW. Since the transformer comprises four cells, it can deliver 4 kW at the output. This transformer configuration has the advantage of allowing the number of cells to be adjusted according to the required output power of the converter. For example, if a power of 8 kW is desired, the transformer will comprise eight cells, each delivering 1 kW.

[0048] The transformer 100 comprises a magnetic core 110, each cell consisting of a first leg 111, 121, 131, 141 and a second leg 112, 122, 132, 142. As shown in Figure 2, cell C1 comprises the first leg 111 and the second leg 112. Cell C2 is adjacent to cell C1, that is, it is located next to cell C1 in the XY plane. Cell C2 comprises the first leg 121 and the second leg 122. Similarly, cells C3 and C4 comprise the first legs 131, 141 and the second legs 132, 142, respectively.

[0049] Although represented in parallelepiped shape, the legs are not limited to this shape.

[0050] The magnetic core 110 is made of ferromagnetic material, for example ferrite.

[0051] In each cell C1, C2, C3, C4, the transformer 100 comprises a primary winding 10, a secondary winding 20, and a tertiary winding 30 wound around the first leg 111, 121, 131, 141, and one of the primary and secondary windings wound around the second leg 112, 122, 132, 142. It also comprises an inductor 40 connected in series. Furthermore, the primary winding 10 and the secondary winding 20 of one cell are connected in series with the primary winding 10 and the secondary winding 20 of an adjacent cell, and the tertiary winding 30 of one cell is connected in parallel with the tertiary winding 30 of the adjacent cell. These windings are shown in Figure 3.

[0052] Figure 3 schematically represents one embodiment of the windings in the converter of the invention. On the right of the figure, the series connection of the primary winding 10 and secondary winding 20 and of the inductor 40 between cells C1, C2, C3, C4 is shown. The parallel connection of the tertiary winding 30 is also visible.

[0053] The different windings per leg are illustrated on the left side of the figure. As shown, this represents the stacking of the windings according to the height of a leg, that is, along the Z-axis. At cell C1, the primary winding 10, the secondary winding 20, and the tertiary winding 30 are wound around the first leg 111. The secondary winding 20 is wound around the second leg 112. Similarly, at cell C2, the primary winding 10, the secondary winding 20, and the tertiary winding 30 are wound around the first leg 121. The secondary winding 20 is wound around the second leg 122. A winding is defined as at least one turn. Each winding thus comprises at least one turn wound around a leg. In the illustrated example, the secondary winding 20 around the second leg of one of the cells comprises a winding of three turns around the leg.This is yet another illustrative example to describe the invention, but it should not be understood as limiting.

[0054] According to an optional feature of the invention, the primary, secondary, and tertiary windings are interleaved. In other words, one turn of the secondary winding is sandwiched between two turns of the primary winding. Similarly, one turn of the primary winding is sandwiched between two turns of the secondary winding. This means that two turns of the same winding are not directly overlapped around their legs. This specific winding arrangement reduces the proximity effect and thus limits component losses.

[0055] For each cell C1, C2, C3, C4, the primary winding 10 and the secondary winding 20 are intertwined around the first leg 111, 121, 131, 141 of the cell. The stacking of the turns of the primary winding 10 and the secondary winding 20 forms a main intertwining 50. The tertiary winding 30 is wound on either side of the main intertwining 50.

[0056] The main interlacing 50 is thus arranged between at least two turns of the tertiary winding 30. This distribution of the tertiary winding 30 around the main interlacing 50 ensures a balancing of the current of the two tertiary windings 30.

[0057] Figure 4 schematically represents a cross-sectional view in the XY plane of the magnetic core 110 of the converter of the invention, indicating the winding directions. The primary winding 10, the secondary winding 20, and the tertiary winding 30 are wound in a first direction SI in one cell and in a second direction S2, opposite to the first direction SI, in the adjacent cell. The winding direction of each cell must be opposite to the winding direction of its adjacent cell(s) in order to generate an opposing magnetic flux between two adjacent cells. This ensures the cancellation of magnetic fluxes on the walls of the magnetic core, thus minimizing core losses.

[0058] The space between the first legs determines the value of the magnetizing inductance. The space between the second legs determines the value of the series inductance.

[0059] Based on Figures 3 and 4, and considering cell Cl, we understand that the primary winding 10 and the tertiary winding 30 are wound around the first leg 111. The secondary winding 20 is wound around the first leg 111 and the second leg 112. This creates an additional flux in the secondary winding that is independent of the primary and tertiary windings. This results in a series inductance of the secondary winding.

[0060] The second legs 112, 122, 132, 142 produce the inductances and the first legs 111, 121, 131, 141 have the role of current transformation.

[0061] Figure 5 schematically illustrates another embodiment of the windings in the converter of the invention. In this embodiment, the transformer 100 further comprises, in each of the cells C1, C2, C3, C4, a shielding layer 60 wound on either side of the main winding 50, between the main winding 50 and the tertiary winding 30. Inserting a shielding layer 60 in the winding stack reduces common-mode noise. This results in improved electromagnetic noise performance.

[0062] Figure 6 schematically illustrates another embodiment of the windings in the converter of the invention. In this embodiment, the transformer comprises two tertiary windings 31, 32. In a cell, the second tertiary winding 32 of one cell is connected in parallel with the second tertiary winding 32 of the adjacent cell. The first tertiary winding 31 is wound on one side of the main layup 50, and the second tertiary winding 32 is wound on the other side of the main layup 50. Put another way, the first tertiary winding 31 can be wound at the base of the stack around the first legs, and the second stack can be wound around the first legs, overlapping the main winding 50.

[0063] The arrangement of the main interlacing 50 between the first tertiary winding 31 and the second tertiary winding 32 ensures the balancing of the current in the tertiary windings. Figure 7 schematically represents another embodiment of the windings in the converter of the invention. This winding embodiment is identical to that shown in Figure 6, except for the winding around the second legs. In the embodiment shown in Figure 7, the primary winding 10 is wound around the second leg 122 (instead of the secondary winding 20 in the previous embodiment). Thus, the primary, secondary, and tertiary windings are wound around the first legs, and the primary winding is wound around the second leg. In this embodiment, it is understood that the primary winding 10 is wound around both legs of each cell. The inductor is located on the primary side.This results in a change in the converter's operating mode. The choice of variant is made according to the intended load mode for the converter.

[0064] The inductor's positioning on the primary or secondary side depends on the converter's specifications, i.e., the voltage range required to charge the high-voltage battery. For example, if the voltage range is wide, the inductor is placed on the secondary side.

[0065] Figure 8 schematically represents a view of the complete magnetic core 110 of the converter of the invention. The magnetic core 110 comprises a lower wall 150 from which the legs 111, 121, 131, 141, 112, 122, 132, 142 rise to a leg height hj. The lower wall 150 extends in the XY plane and provides support for the first and second legs.

[0066] The magnetic core 110 comprises two side walls 151, 152 extending from the lower wall 150 to a wall height hp greater than or equal to the leg height hj. The magnetic core 110 also comprises an upper wall 153 in contact with the two side walls 151, 152. There is no gap between the upper wall 153 and the two side walls 151, 152. The upper wall 153 rests completely on the two side walls 151, 152.

[0067] In one embodiment, the first and second legs can have a height hj equal to the height hp of the side walls 151, 152. In this case, the upper wall 153 also rests on the first and second legs, without any gaps between the upper wall and the upper surface of the legs. In another embodiment, the wall height hp of the side walls 151, 152 is greater than the leg height hj of the legs. This means that the upper wall 153 is in contact with both side walls 151, 152, but not with the upper surface of the legs. There is therefore an air gap between the legs and the upper wall 153 of the magnetic core. Epoxy resin can be sandwiched in this space between the leg and the upper wall 153. This is the air gap. It is also possible to have a successive stack of epoxy resin and ferrite.The difference between the wall height (hp) and the leg height (hj) allows you to adjust the desired inductance value. This adjustment helps reduce copper losses in the windings around the legs.

[0068] As explained previously, each winding comprises one or more turns. Each winding is wound around a leg 111, 121, 131, 141, 112, 122, 132, 142 in a plurality of layers. The windings can be made from magnetic wires or busbars.

[0069] According to an optional feature of the invention, the windings are formed by an electronic board, or PCB (short for Printed Circuit Board). In this case, the transformer comprises an electronic board 70 having openings 211, 221, 231, 241, 212, 222, 232, 242 and overlapping traces wound around the openings. The stacking of the traces on the electronic board and the connection between the different layers is achieved by vias. Thus, the traces form the windings. For example, considering cell C1, the primary, secondary, and tertiary windings are wound in the electronic board around opening 211 (illustrated in Figure 4), and the secondary winding is wound in the electronic board around opening 212.

[0070] Each leg of the magnetic core passes through an opening in the electronic board. As illustrated in Figure 4, leg 111 passes through opening 211 and leg 112 passes through opening 212. When the electronic board 70 is positioned within the magnetic core, that is, when its openings pass through the legs, the windings around opening 211 are thus positioned around the first leg 111, and the secondary winding around opening 212 is positioned around the second leg 112. The same principle applies to the legs of adjacent cells, with the windings around the openings provided for this purpose in the electronic board. It is therefore clear that each leg of the magnetic core corresponds to an opening in the electronic board. Using such an electronic board containing all the transformer windings offers numerous advantages.Thanks to the controlled manufacturing processes of PCB boards, it is easy to produce such an electronic board and it is possible to achieve different winding configurations as discussed in this document.

[0071] The transformer is thus obtained with only three components: the electronic board 70, which contains all the windings arranged in a specific configuration unique to the invention; the base of the magnetic core (formed by the lower wall 150, the side walls 151 and 152, and the legs); and the upper wall of the core. With its small footprint, such a transformer can be adapted to the power requirements of the load converter 300 in which it is installed. Numerous parameters are adjustable, such as the number of cells, the winding configuration, the leg spacing, and the spacing between the upper surface of the legs and the upper wall of the magnetic core.

[0072] Figure 9 schematically represents a motor vehicle comprising a charge converter 300 of the invention. The motor vehicle 400 includes an on-board network intended to be powered by a low-voltage DC (BT) current and to be connected to an AC (alternating current) network.

[0073] The invention effectively solves the problem it set out to address, namely providing a load converter combining the functions of an OBC and a DC-DC converter. Thanks to a specific winding arrangement within the transformer, the load converter of the invention offers high modularity to meet varying output power requirements, for example, 2, 4, or 6 kW. It has a small footprint and is easy to assemble.

[0074] Of course, the invention is not limited to the examples just described, and many modifications can be made to these examples without departing from the scope of the invention. In particular, the features of different embodiments of the invention can be combined to carry out the invention, provided that these embodiments are not incompatible with each other.

Claims

DEMANDS 1- Load converter (300) for converting alternating current (AC) into low-voltage direct current (LV DC) and high-voltage direct current (HV DC), comprising an AC-to-DC converter (310) and a transformer (100) for converting DC into low-voltage direct current (LV DC) and high-voltage direct current (HV DC), characterized in that the transformer (100) comprises: a plurality of adjacent cells (C1, C2, C3, C4), a magnetic core (110) comprising a first leg (111, 121, 131, 141) and a second leg (112, 122, 132, 142) per cell, and in each cell (C1, C2, C3, C4): a primary winding (10), a secondary winding (20), and a tertiary winding (30) wound around the first leg (111, 121, 131, 141) and one among the primary winding and the secondary winding wound around the second leg (112, 122, 132,142) and an inductor (40) connected in series; and in that the primary winding (10), respectively the secondary winding (20), of one cell is connected in series with the primary winding (10), respectively the secondary winding (20), of an adjacent cell, and the tertiary winding (30) of one cell is connected in parallel with the tertiary winding (30) of the adjacent cell. 2- Converter according to claim 1, in which the first legs and the second legs are parallel to each other. 3- Converter (300) according to claim 1 or 2, in which the primary winding (10), the secondary winding (20) and the tertiary winding (30) are wound in a first direction (SI) in one cell and in a second direction (S2), opposite to the first direction (SI), in the adjacent cell. 4- Converter (300) according to any one of claims 1 to 3, wherein the primary winding (10) and the secondary winding (20) are interlaced around the first leg (111, 121, 131, 141) of each cell (Cl, C2, C3, C4) so ​​as to form a main interlacing (50), and the tertiary winding (30) is wound on either side of the main interlacing (50). 5- Converter (300) according to claim 4, wherein the transformer further comprises in each cell (Cl, C2, C3, C4) a shielding layer (60) wound on either side of the main interlacing (50), between the main interlacing (50) and the tertiary winding (30). 6- Converter (300) according to claim 4 or 5, the tertiary winding (30) being the first tertiary winding (31), the transformer further comprising a second tertiary winding (32), the second tertiary winding (32) of a cell (Cl, C2, C3, C4) being connected in parallel with the second tertiary winding (32) of the adjacent cell, and the first tertiary winding (31) is wound on one part of the main interlace (50) and the second tertiary winding (32) is wound on the other part of the main interlace (50). 7- Converter (300) according to any one of claims 1 to 6, each of the windings being wound around a leg (111, 121, 131, 141, 112, 122, 132, 142) in a plurality of layers, the transformer comprising an electronic board (70) having openings (211, 221, 231, 241, 212, 222, 232, 242) and superimposed tracks wound around the openings, the tracks forming the windings and each leg passing through an opening of the electronic board. 8- Converter (300) according to any one of claims 1 to 7, in which the magnetic core (110) comprises: a lower wall (150) from which the legs (111, 121, 131, 141, 112, 122, 132, 142) rise to a leg height, two side walls (151, 152) rising from the lower wall (150) to a wall height (hp) greater than or equal to the leg height (hj), an upper wall (153) in contact with the two side walls (151, 152). 9- Converter (300) according to claim 8, wherein the wall height (hp) of the two side walls (151, 152) is greater than the leg height (hj) of the legs. 10- Motor vehicle (400) comprising an on-board network configured to be powered by low-voltage direct current (LV DC), the vehicle being configured to be connected to an alternating current (AC) network, the motor vehicle comprising a load converter (300) according to any one of the claims

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