EP0523588A1 - Transformer winding composed of an insulating tape comprising electrically conductive patterns for realizing a parallel arrangement of the patterns when zigzag folding this tape - Google Patents

Abstract

According to the invention, one side of the insulating tape (25) includes alternately one face (34; 36) with pattern (26; 27) and one face (35, 37) without pattern, each pattern (26, 27) including two tags for placing in parallel (28, 29; 30, 31) each extending by one of its ends beyond a line of separation (P1, P3) so as to cross over onto the face (35; 37) without pattern in such a way that the tags for placing in parallel (28, 29; 30, 31) of each pattern (26, 27) enter into electrical contact with the ends of the adjoining pattern (26, 27) when the tape (25) is folded into a zig zag, in such a way as to place the patterns (26, 27) in parallel. <??>The invention applies in particular to the production of high-frequency transformers used in chopped supplies. <IMAGE>

Description

The field of the invention is that of transformer windings and more precisely that of windings formed by strips of electrically conductive material included on an insulating tape.

In known manner, miniature electric windings, in particular those used in high-frequency transformers used in switching power supplies, are generally made from copper ribbons whose thickness is close to the depth of penetration of electric currents in the conductors, i.e. the thickness of the skin. These copper ribbons are arranged on a sheet of insulating material, the folding of which gives the possibility of winding. An intimate nesting of a sheet comprising ribbons constituting the primary of a transformer with a sheet comprising turns for the secondary makes it possible to give such a transformer good electrical efficiency.

However, in the case where high currents are required at the secondary of the transformer, it is necessary to proceed with a paralleling of the turns of the secondary to limit the width of these turns and thus reduce the size of the transformer.

Indeed, if we take the example of a transformer having 8 turns in series at the primary and 1 turn at the secondary, for an input voltage of 48 volts, the turn of the secondary will theoretically see 6 volts at its ends. For a primary current absorbed of 1 amp, the current circulating in the secondary coil is therefore 8 amps. It is therefore not possible to configure the secondary turn like the primary turns. The secondary turn must be thicker and wider than each of the primary turns.

On the other hand, if the secondary consists of 8 turns in parallel, the current flowing in each turn is no more than 1 ampere, a much more reasonable value, while the secondary voltage is always 6 volts.

We therefore understand the usefulness of a parallel connection of the secondary turns of a high-frequency transformer that must meet conditions of minimal bulk and high power.

Usually, the secondary turns of a transformer of this type are placed in parallel by a remote connection, for example using connection wires as shown in Figure 1. This figure was taken from the review POWER ELECTRONICS n ° 36 p. 46.

Figure 1 shows the principle of connection of primary and secondary turns of a transformer. The patterns 10 to 17 of the transformer consist of a continuous strip of copper. These patterns are in series and their folding makes it possible to obtain four turns in series. The patterns 10 and 17 constitute the ends and a primary voltage V1 can be applied to them. The transformer secondary consists of unit turns 19 to 22. Each of the transformer turns is crossed by a magnetic circuit, the axis of which is referenced 18.

For the reasons mentioned above, the secondary turns of the transformer thus produced are connected in parallel using wire portions 23, 24 to reduce the current flowing in the turns 19 to 22. A voltage V2 is thus obtained at the secondary when the primary and secondary turns are nested one inside the other.

The main drawback of this type of transformer is that the secondary turns are connected in parallel by welding and therefore limits the high-frequency performance. A wire connection also leads to heterogeneity in the secondary current flows. In addition, the parallel connection of the turns secondary is difficult to achieve, given the size of these turns and the distance between them once the insulating sheet is folded and fixed in the carcass of the magnetic circuit.

This heterogeneous connection principle is also found in transformers made up of open turns mounted in a case constituting the magnetic core, the connections of the turns being made using conductive tracks of an electronic card on which the magnetic core is fixed. The part of turns produced by the printed circuit is not in the same plane as the rest of the turn and the yield is therefore affected. Connecting one turn to the other further increases the length of the transformer secondary connections.

The present invention aims in particular to overcome these drawbacks.

More specifically, one of the objectives of the invention is to provide a transformer winding which allows the turns of this winding to be simply paralleled, which reduces the connection lengths outside the useful zones of the turns, these connections can be homogeneously, that is to say without additional soldering or connections.

Another object of the invention is to simplify the manufacturing process of such a winding and therefore of a transformer using such a winding.

An additional objective is to limit the volumes of insulator of such a transformer, in order to reduce its size, while ensuring optimal nesting of the primary and secondary turns.

These objectives, as well as others which will appear subsequently, are achieved by means of a transformer winding, of the type consisting of an insulating tape comprising on one of its sides patterns consisting of strips of electrically conductive material, the ribbon insulator being folded in an accordion, to constitute the winding, according to equidistant separation lines delimiting faces of the insulating tape, each pattern included between two separation lines constituting a turn of the winding, this winding being characterized in that this side of the tape comprises alternately a face with a pattern and a face without a pattern, each pattern comprising two paralleling legs extending each of its ends beyond a dividing line to extend beyond the side without a pattern so that the matching legs parallel of each pattern come into electrical contact with the ends of the neighboring pattern when the insulating tape is folded in accordion, so as to achieve a parallelization of the patterns.

This paralleling of the patterns is therefore obtained by simple accordion folding of the ribbon and is accompanied by insulation between the turns, thanks to the faces without pattern.

The invention also relates to a transformer winding consisting of an insulating tape alternately comprising two faces carrying a group of two patterns in series and two non-patterned faces comprising connecting tabs of the groups of patterns, the connecting tabs extending from on either side of the dividing line delimiting the two faces without pattern, each group of patterns comprising two parallel tabs extending each of its ends beyond the dividing line located between the two patterns of the group, the tabs for paralleling each group of patterns coming into electrical contact with the ends of the group of neighboring patterns via the connecting tabs when the insulating tape is folded in an accordion fashion, so as to bring the groups of motives.

It is thus possible to carry out a paralleling of patterns in series.

Advantageously, one of the windings as identified above constitutes one of the windings of a transformer, the other side of the insulating tape comprising patterns constituting the other winding of the transformer when the insulating tape is folded in accordion. This provides optimal nesting of primary and secondary and minimized footprint.

The invention also relates to a transformer produced from such a winding.

• la figure 1 représente un principe connu de liaison en parallèle de spires d'un transformateur haute-fréquence ;
• la figure 2 représente un ruban isolant comportant sur l'un de ses côtés des motifs en matériau électriquement conducteur, selon un mode de réalisation de l'invention ;
• la figure 3 représente le pliage en accordéon du ruban isolant de la figure 2 ;
• la figure 4 est une vue latérale du ruban isolant des figures 2 et 3 entièrement plié ;
• la figure 5 est un exemple de réalisation d'une mise en parallèle de groupes de deux spires en série ;
• les figures 6 et 7 représentent les deux côtés d'un ruban isolant comportant des motifs selon un mode de réalisation du bobinage selon l'invention.

Other characteristics and advantages of the invention will appear on reading the following description of two preferred embodiments, given by way of illustration and not limitation, and the appended drawings in which:

• FIG. 1 represents a known principle of parallel connection of turns of a high-frequency transformer;
• 2 shows an insulating tape having on one of its sides patterns of electrically conductive material, according to one embodiment of the invention;
• Figure 3 shows the folding accordion of the insulating tape of Figure 2;
• Figure 4 is a side view of the insulating tape of Figures 2 and 3 fully folded;
• Figure 5 is an exemplary embodiment of a parallel connection of groups of two turns in series;
• Figures 6 and 7 show the two sides of an insulating tape having patterns according to an embodiment of the winding according to the invention.

Figure 1 has been described with reference to the state of the art.

FIG. 2 represents an insulating tape comprising on one of its sides patterns made of electrically conductive material, according to an embodiment of the invention.

An insulating tape 25, of which only a part is shown, has on one of its sides patterns 26, 27 of electrically conductive material. These patterns are for example produced by a chemical etching process. The insulating tape 25 is for example in capton and the patterns 26, 27 in copper. The ribbon 25 is intended to be folded along equidistant separation lines P1, P2, P3. Each pattern 26, 27 corresponds to a turn of the winding produced by folding the ribbon 25, as will be explained below.

According to the invention, in order to achieve a paralleling of the patterns of the ribbon, paralleling tabs 28, 29, 30, 31 each extend patterns 26, 27 of the ribbon 25, this extension being carried out up to beyond the separation lines P1 and P3, so that the paralleling tabs 28 and 29, extending the ends of the pattern 26, come into contact after folding the ribbon 25 with the ends 32 and 33 of the pattern 27. This comparison of the patterns will be better understood on reading the following description of FIG. 3.

FIG. 3 represents the folding in accordion of the ribbon of FIG. 2.

Accordion folding of the insulating tape 25 is carried out according to the folds P1 to P3, each folding being carried out in the opposite direction to the previous one. The face 34 comprises the turn 26, the face 35 the paralleling tabs 28, 29 of the turn 26, the face 36 the turn 27 and the face 37 the paralleling tabs 30, 31 of the turn 27. The faces 34, 36 comprising patterns are alternated with faces 35, 37 without pattern. During folding, carried out in one direction 38, the face 35 comes into contact with the face 36 and the lugs for paralleling 28 and 29 of the turn 26 come into contact with the ends 32 and 33 of the turn 27.

The parallelization of the turns is thus carried out automatically, without the need to add connection wires after folding. In addition, it is not necessary to insert an insulating tape between the faces when folding, this insulation being provided by the absence of patterns on the faces located between the faces having patterns. There is therefore obtained a smaller size of the winding than that presented by the windings of the prior art.

The paralleling lugs 30 and 31 of the turn 27 likewise come into contact with the ends of a turn located on a face with which the face 37 comes into contact by folding. It is thus possible to bring in parallel a large number of unitary turns of a transformer winding.

Figure 4 is a side view of the insulating tape of Figures 2 and 3 fully folded.

The folding accordion ensures the parallelization of the turns 26 and 27. Access to the windings of the winding is easy, since at the folds P1 and P3 the conductive tracks are visible.

The turns of the ribbon can either be kept in contact by pressure in a transformer, or welded after folding to ensure optimal contact between the turns.

According to a preferred embodiment, the insulating tape is in capton and measures between 50 and 75 μm in thickness and the copper has a thickness of approximately 75 μm.

Of course, the turns placed in parallel are not necessarily unitary. Thus, for a configuration of different turns, it is possible to put groups of several turns in parallel. FIG. 5 is an exemplary embodiment of a grouping of groups of two turns in series.

The insulating tape 25 includes screen-printed patterns consisting of two turns in series. Thus, the faces 50, 51, 54 and 55 each have a turn, respectively referenced 56, 57, 58 and 59. The turns 56 and 57 are in series, as well as the neighboring turns 58 and 59, this series of turns being provided by conductive tracks. The faces 52 and 53 of the ribbon 25 only comprise connecting tabs 60, 61 extending on either side of the fold P6.

The turns 56 and 57 form a group of turns, the ends of which are extended by paralleling lugs 62 and 63 extending beyond the fold P4 in opposite directions.

When the ribbon 25 is folded, the paralleling tab 62 comes into contact with the part of the connecting tab 60 located on the face 52 and the part of the connecting tab 60 located on the face 53 comes into contact with the end of the coil 58. The same applies to the paralleling tab 65 of the face 54 which comes into contact with the end of the coil 57 through the connecting tab 61.

The folding carried out, associated with a specific configuration of the turns, therefore makes it possible to put groups of two turns in parallel. The paralleling lugs 63 and 64 come into contact with connecting lugs located respectively above and below the turns shown.

It goes without saying that the number of turns in a group's series is not limited to two. Different configurations of the turns allow paralleling of groups made up of a large number of turns in series.

In this embodiment, the insulations between the turns are also automatically obtained by accordion-folding of the ribbon, since the faces 52 and 53 do not include a pattern constituting a turn.

The non-referenced holes drilled in the center of each face allow the passage of a magnetic circuit. These orifices are also present, but not shown in the first embodiment (fig. 2 and 3).

Of course, the overshoot of the fold by paralleling lugs can also be used for placing turns in series. This embodiment also allows a reduction in the lengths of the conductors. The reasons present more complex forms, however. It is then necessary to isolate certain copper surfaces to avoid short circuits, resulting in a more complex winding.

As previously described, the ribbon 25 comprising the patterns constituting turns is intended to be nested with another ribbon. This other strip may for example comprise turns in series, and constitute the primary of a transformer, the secondary being produced by placing turns in parallel in accordance with the invention.

This known embodiment however has the drawback of having a variable yield, depending on whether the interweaving of the ribbons is more or less well performed.

This is why the primary and secondary of the transformer are preferably made on the same insulating tape. One side of the insulating tape comprises the turns constituting the primary winding and the other side those constituting the secondary winding. During the manufacture of the ribbon, it is then easy to arrange the turns so that an optimal primary-secondary nesting is ensured.

In addition, the orifices for passage of the magnetic circuit need only be made once.

Figures 6 and 7 show the two sides of such an insulating tape.

On a first side of the ribbon 25, shown in Figure 6, the patterns are placed in series by extending the conductive tracks from one pattern to another. Each pattern consists of a turn which will be crossed by a cylindrical bar constituting the magnetic circuit. The ribbon 25 is intended to be folded according to the folds P10 to P15.

The opposite side of the ribbon 25 includes the patterns shown in Figure 7. These patterns are intended to be connected in parallel by folding and consist of unitary turns.

It can be seen, with reference to FIG. 6, that the folds P10 to P15 produced allow the paralleling tabs to extend beyond the ends of the patterns in FIG. 7. In addition, as shown by the broken lines 70, the patterns of FIG. 7 are opposite a pattern, each of the two patterns in FIG. 6.

When inserting the folded insulating tape 25 into a magnetic circuit, the folds P10, P12, P13 and P15 are accessible from the outside of the transformer, in particular for carrying out a welding operation of the turns if the tape is not sufficient compressed, to ensure sufficient and permanent contact of the superimposed turns.

The transformer winding according to the invention therefore allows a maximum reduction in the lengths of the conductors, essential when the working frequencies are high, an absence of solder connections when the folded strip is sufficiently compressed, a simplification of the transformer assembly and limitation of insulation volumes.

Claims (4)

Transformer winding, of the type made up of an insulating tape (25) comprising on one of its sides patterns (26,27) made up of strips of electrically conductive material, said insulating tape (25) being folded in an accordion, for constitute said winding, according to equidistant separation lines (P1-P3) delimiting faces of said insulating tape (25), each pattern (26, 27) lying between two separation lines (P2, P3) constituting a turn of said winding,
characterized in that said side alternately comprises a face (34; 36) with pattern (26; 27) and a face (35; 37) without pattern, each pattern (26,27) comprising two paralleling tabs (28, 29; 30,31) extending each of its ends beyond a dividing line (P1, P3) to extend beyond said face (35; 37) without pattern so that said paralleling tabs (28, 29; 30,31) of each pattern (26; 27) come into electrical contact with the ends of the neighboring pattern (26,27) when said insulating tape (25) is folded in accordion fashion, so as to make a paralleling of said patterns patterns (26,27). Transformer winding, of the type consisting of an insulating tape (25) comprising on one of its sides patterns (56,57,58,59) consisting of strips of electrically conductive material, said winding being produced by folding in accordion said insulating tape (25) along equidistant dividing lines (P4-P9) delimiting faces (50-55) of said insulating tape (25), each pattern (56,57,58,59) lying between two dividing lines ( P4-P9) constituting a turn of said winding,
characterized in that said side alternately comprises two faces (50,51; 54,55) carrying a group of two patterns (56,57; 58,59) in series and two unmodified faces (52,53) having tabs bond (60.61) said groups of patterns (56.57; 58.59), said connecting tabs (60.61) extending on either side of the separation line (P6) delimiting said two faces without pattern (52.53 ), each group of patterns (56.57; 58.59) comprising two paralleling tabs (62.63; 64.65) extending each of its ends beyond the dividing line (P4; P8) located between the two patterns (56,57; 58,59) of said group, said paralleling tabs (62,63; 64,65) of each group of patterns coming into electrical contact with the ends of the group of patterns (56, 57; 58,59) neighbor via said connecting tabs (60,61) when said insulating tape (25) is folded in accordion fashion, so as to bring said groups of patterns into parallel (56,57; 58 , 59). Winding according to one of claims 1 and 2, characterized in that it constitutes one of the windings of a transformer, the other side of said insulating tape (25) comprising patterns constituting the other winding of said transformer when said insulating tape (25) is folded like an accordion. Transformer, characterized in that it comprises a winding according to one of claims 1 to 3.

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