FR3116372A1 - ELECTRICAL DEVICE WITH TWO GROUPS OF COUPLED COILS CARRIED BY A PRINTED CIRCUIT BOARD, VOLTAGE CONVERTER COMPRISING SUCH ELECTRICAL DEVICE AND METHOD FOR MANUFACTURING SUCH ELECTRICAL DEVICE - Google Patents

Abstract

This electric device comprises: a first group of coils (P1a, P1b, S1) wound around a leg (N1) of a magnetic core (N) to be magnetically coupled together; a second group of coils (P2a, P2b, S2) wound around a leg (N2) of a magnetic core (N) to be magnetically coupled together; electrical components (Q1, Q2, Cf, D1, D2, Cs); and - a printed circuit board (108) carrying the electrical components (Q1, Q2, Cf, D1, D2, Cs) and the groups of coupled coils and having conductive tracks (T1a, T1b, T2a, T2b, T1s, T2s , Ts, T) connecting at least one coil of the first group (P1a, P1b, S1) to at least one of the electrical components (Q1, Q2, Cf, D1, D2, Cs) and at least one coil of the second group (P2a , P2b, S2) to at least one of the electrical components (Q1, Q2, Cf, D1, D2, Cs). It further comprises at least one electrical connector (Ba, Bb, Bs) external to the printed circuit board (108) and connecting at least one coil (P1a, P1b, S1) of the first group to a coil (P2a, P2b, S2) of the second group, two respective second ends of these two coils being connected to the conductive tracks of the printed circuit board (108). Figure for abstract: Fig. 1

Description

ELECTRICAL DEVICE WITH TWO GROUPS OF COUPLED COILS CARRIED BY A PRINTED CIRCUIT BOARD, VOLTAGE CONVERTER COMPRISING SUCH ELECTRICAL DEVICE AND METHOD FOR MANUFACTURING SUCH ELECTRICAL DEVICE

The present invention relates to an electrical device with two groups of coupled coils carried by a printed circuit board, a voltage converter comprising such an electrical device and a method of manufacturing such an electrical device.

• un premier groupe de bobines enroulées autour d’une branche d’un noyau magnétique pour être couplées magnétiquement entre elles ;
• un deuxième groupe de bobines enroulées autour d’une branche d’un noyau magnétique pour être couplées magnétiquement entre elles ;
• des composants électriques ;
• une carte de circuit imprimé portant les composants électriques et les groupes de bobines couplées et présentant des pistes conductrices connectant au moins une bobine du premier groupe à au moins un des composants électriques et au moins une bobine du deuxième groupe à au moins un des composants électriques.

An electrical device of the type comprising:

• a first group of coils wound around a branch of a magnetic core to be magnetically coupled together;
• a second group of coils wound around a branch of a magnetic core to be magnetically coupled together;
• electrical components;
• a printed circuit board carrying the electrical components and the groups of coupled coils and having conductive tracks connecting at least one coil of the first group to at least one of the electrical components and at least one coil of the second group to at least one of the electrical components .

It may be desired to provide such an electrical device having reduced electrical losses.

An electrical device of the aforementioned type is therefore proposed, characterized in that it further comprises at least one electrical connector external to the printed circuit board and connecting a coil of the first group to a coil of the second group, two respective second ends of these two coils being connected to the conductive tracks of the printed circuit board.

Thus, thanks to the invention, the number of connections between the coils and the tracks of the printed circuit board is reduced compared to the case where each pair of coils having to be connected to each other are connected by tracks of the circuit board. printed circuit board. However, these connections are sources of electrical losses. Reducing their number therefore makes it possible to reduce electrical losses.

Optionally, each electrical connector comprises an electrical conduction bar, which in particular forms a rigid conductor.

Also optionally, the first group of coils comprises first, second and third coils and the second group of coils comprises first, second and third coils.

• un premier connecteur électrique connectant ensemble deux premières extrémités respectives des deux premières bobines ;
• un deuxième connecteur électrique connectant ensemble deux premières extrémités respectives des deux deuxièmes bobines ; et
• un troisième connecteur électrique connectant ensemble deux premières extrémités des deux troisièmes bobines.

Also optionally, the at least one electrical connector comprises:

• a first electrical connector connecting together two respective first ends of the two first coils;
• a second electrical connector connecting together two respective first ends of the two second coils; And
• a third electrical connector connecting together two first ends of the two third coils.

Also optionally, the electrical device further comprises a magnetic core comprising a first branch, a second branch and a third branch joining at their ends and having respective reluctances, the reluctance of the third branch being lower both than that of the first branch and that of the second branch.

Also optionally, at least one of the coils of the first group is designed to generate a first magnetic flux in the first branch, looping back through the third branch, at least one of the coils of the second group is designed to generate a second magnetic flux in the second branch, looping back through the third branch, and these coils generating the first and second magnetic fluxes are wound in respective winding directions such that the first and second magnetic fluxes traverse the third branch in opposite directions.

There is also proposed a voltage converter comprising an electrical device according to the invention. In particular, the converter forms a direct storage converter.

• l’obtention des premier et deuxième groupes de bobines couplées avec le ou les connecteurs électriques ;
• la fixation des premier et deuxième groupes de bobines couplées sur la carte de circuit imprimé ; et
• la connexion des bobines et des connecteurs électriques aux pistes de la carte de circuit imprimé.

A method for manufacturing an electrical device according to the invention is also proposed, comprising:

• obtaining the first and second groups of coils coupled with the at least one electrical connector;
• securing the first and second groups of coupled coils to the printed circuit board; And
• the connection of coils and electrical connectors to the tracks of the printed circuit board.

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 appended drawings in which:

there is a simplified view of an electrical system comprising a voltage converter according to an example of the invention,

there is a sectional view of a three-legged magnetic core with two coils wound respectively around two of the three legs, the magnetic flux resulting from an excitation of these coils being illustrated, and

there is a block diagram of a method of manufacturing the voltage converter of the .

With reference to the , an electrical system 100 comprising an electrical device 102 implementing the invention will now be described. Such an electrical system 100 can for example be used in a motor vehicle.

The electrical system 100 first comprises a voltage source 104 designed to supply an input voltage Ve which is continuous. The voltage source 104 comprises for example a motor vehicle battery.

Electrical system 100 further includes an electrical load 106, such as automotive electrical accessories or a voltage source of lower rated voltage than voltage source 104.

In the example described, the electrical device 102 is a DC-DC voltage converter designed to receive the input voltage Ve and to supply the electrical load 106 with a DC output voltage Vs. More specifically, in the example described, the electrical converter 102 is a flyback-forward converter, that is to say the combination of an accumulation converter (from the 'flyback converter') and a direct converter ('forward converter').

The electrical device 102 firstly comprises a printed circuit board 108 carrying various electrical components and on which extend conductive tracks connecting these components together.

The electrical device 102 comprises in particular, carried by the printed circuit board 108, a positive terminal (+) and a negative terminal (-) respectively connected to positive and negative terminals of the voltage source 104, as well as two switches Q1 , Q2 and a so-called fly capacitor Cf, connected between the two switches Q1, Q2, the assembly Q1, Q2, Cf being connected between the positive (+) and negative ( -).

The electrical device 102 further comprises a double transformer 110 intended for storing and restoring electrical energy in the example described.

The double transformer 110 firstly comprises a magnetic core N, for example made of ferrite material. The magnetic core N comprises three branches N1, N2, N3 meeting at their two ends, that is to say they have respective first ends meeting, as well as respective second ends meeting.

In the example described, branches N1, N2 are C-shaped, while branch N3 is I-shaped and extends between the other two.

Branches N1, N2, N3 have respective reluctances such that the reluctance of branch N3 is less, preferably at least ten times, preferably still a hundred times, both the reluctance of branch N1 and the reluctance of branch N2. In the example described, the branches N1, N2 respectively have air gaps E1, E2 ("air-gap" in English). Each of the air gaps E1, E2 can be left filled with air, or it can be filled with a material of low permeability (relative permeability of the air or of said material close to 1).

The double transformer 110 further comprises a first group of coils wound around the branch N1 to be magnetically coupled together. In the example described, the first group of coils comprises first, second and third coils P1a, P1b, S1. Thus, the magnetic core N and the coils of the first group form a first transformer, with the coils P1a, P1b forming primary coils and the coil S1 forming a secondary coil of the first transformer.

The double transformer 110 further comprises a second group of coils wound around the branch N2 to be magnetically coupled together. In the example described, the second group of coils comprises first, second and third coils P2a, P2b, S2. Thus, the magnetic core N and the coils of the second group form a second transformer, with the coils P2a, P2b forming primary coils and the coil S2 forming a secondary coil of this second transformer.

Coils are sometimes also called “chokes”. A first end of the coil P1a is connected between the switch Q1 and the capacitor Cf by a conductive track T1a and a first end of the coil P2a is connected to the second switch Q2 by a conductive track T2a, in particular between the second switch Q2 and the negative (-) terminal of the voltage source.

The electrical device 102 further comprises an electrical connector Ba connecting together the second ends of the coils P1a, P2a.

A first end of the coil P1b is connected to the first switch Q1 by a conductive track T1b, in particular between the first switch Q1 and the positive terminal (+) of the voltage source 104; and a first end of coil P2b is connected between switch Q2 and capacitor Cf by a conductive track T2b.

The electrical device 102 further comprises an electrical connector Bb connecting together the second ends of the coils P1b, P2b.

First ends of coils S1, S2 are connected together by an electrical connector Bs.

The electrical device 102 further comprises, carried by the printed circuit board 108, an output capacitor Cs having the output voltage Vs, and two diodes D1, D2 connected respectively between the second ends of the coils S1, S2 by conductive tracks. T1s, T2s and a first terminal of the output capacitor Cs by a conductive track T. The diodes D1, D2 can be replaced by switches.

Furthermore, electrical connector Bs is connected to a second terminal of output capacitor Cs by a conductive track Ts.

The electrical connectors Ba, Bb, Bs are external to the printed circuit board 108 and each comprise, for example, an electrical conduction bar (“busbar”). The electrical connectors Ba, Bb, Bs make it possible to limit the number of connections between the double transformer 110 and the conductive tracks of the printed circuit board. In the example described, this number is limited to seven, whereas it would be twelve if the coils were connected to each other via electrical tracks on the printed circuit board 108.

When the switches Q1, Q2 are alternately closed and open, the coils of the first group generate a magnetic flux in the branch N1, looping back through the branch N3, and the coils of the second group generate a magnetic flux in the branch N2, looping back through the third branch N3.

The coils are wound in respective winding directions such that the magnetic fluxes traverse the branch N3 in opposite directions. Thus, the total magnetic flux in the branch N3 is very low compared to the flux traversing the other branches N1, N2. In particular, the total magnetic flux in the branch N3 has an average value or an almost zero alternating value. This effect is visible on the which represents the magnetic field in a three-pronged N' magnetic core, similar to the N magnetic core of the , with two coils wound so as to respectively generate two magnetic fluxes of opposite directions in the third branch.

Back to the , because of this relatively low total magnetic flux, the branch N3 may have a small section, in any case smaller than the section of two adjoining branches of two magnetic cores of the state of the art. As the branch N3 is small, the coils P1a, P2a are relatively close to each other, so that the length of the electrical connector Ba can be reduced. Similarly, the length of the electrical connectors Bb and Bs is also reduced. This reduced length of the electrical connectors Ba, Bb, Bs makes it possible to reduce losses.

The operation of the electrical system 100 is for example similar to the direct storage converter described in the patent application publication FR3042661 A1, the content of which as regards the function of each coil P1a, P1b, S1, P2a, P2b, S2 in depending on the configuration of switches Q1, Q2 is included in this application.

Furthermore, the currents leaving the coils S1, S2 in the direction of the output capacitor Cs are each mainly alternating and are added in the conductive track Ts to form a mainly direct current.

However, the electrical connector Bs can have a much larger section than that of the electrical tracks of the printed circuit board 108 and is therefore much more advantageous for the transport of alternating currents. In particular, the thickness of the electrical connector Bs can exceed 1 mm, while the thickness of a conductive track is generally limited to a hundred μm and the use of several stacked conductive tracks to increase the thickness leads to high losses due to interactions between the conductive tracks.

With reference to the , a method 300 of manufacturing the voltage converter 102 will now be described.

During a step 302, the double transformer 110 is obtained, with the coils P1a, P1b, S1 and P2a, P2b, S2 wound around the magnetic core N, as illustrated in the , and the electrical connectors Ba, Bb, Bs connected to the coils as shown in the .

During a step 304, the double transformer 110 is fixed on the printed circuit board 108.

During a step 306, the coils P1a, P1b, S1, P2a, P2b, S2 and the connector Bs are connected to the tracks of the printed circuit board 108.

It will be appreciated that the double transformer 110 is obtained from a single block in the example described, which simplifies its handling and its integration. On the contrary, in the state of the art, two separate blocks (one block for each transformer) must be managed or a support must be provided to group the two transformers together. In particular, the fixing and connection steps are carried out only once in the invention whereas they must be duplicated in the method of the state of the art, when two independent transformers are used.

It is clear that an electrical device such as the one described above makes it possible to reduce electrical losses by reducing the number of connections between the coils of the transformers and the tracks of the printed circuit board.

It will also be noted that the invention is not limited to the embodiments described above. It will indeed appear to those skilled in the art that various modifications can be made to the embodiments described above, in the light of the teaching which has just been disclosed to them.

In particular, third and/or fourth branches could be provided on the outer sides of the magnetic core N.

In the detailed presentation of the invention which is made above, the terms used must not be interpreted as limiting the invention to the embodiments set out in the present description, but must be interpreted to include therein all the equivalents whose provision is within the reach of those skilled in the art by applying their general knowledge to the implementation of the teaching which has just been disclosed to them.

Claims (9)

Electrical device comprising:

• a first group of coils (P1a, P1b, S1) wound around a branch (N1) of a magnetic core (N) to be magnetically coupled together;
• a second group of coils (P2a, P2b, S2) wound around a leg (N2) of a magnetic core (N) to be magnetically coupled together;
• electrical components (Q1, Q2, Cf, D1, D2, Cs); And
• a printed circuit board (108) carrying the electrical components (Q1, Q2, Cf, D1, D2, Cs) and the groups of coupled coils and having conductive tracks (T1a, T1b, T2a, T2b, T1s, T2s, Ts , T) connecting at least one coil of the first group (P1a, P1b, S1) to at least one of the electrical components (Q1, Q2, Cf, D1, D2, Cs) and at least one coil of the second group (P2a, P2b , S2) to at least one of the electrical components (Q1, Q2, Cf, D1, D2, Cs);

characterized in that it further comprises:

• at least one electrical connector (Ba, Bb, Bs) external to the printed circuit board (108) and connecting at least one coil (P1a, P1b, S1) of the first group to a coil (P2a, P2b, S2) of the second group, two respective second ends of these two coils being connected to the conductive tracks of the printed circuit board (108).

Electrical device according to Claim 1, in which each electrical connector (Ba, Bb, Bs) comprises an electrical conduction bar. An electrical device according to claim 1 or 2, wherein the first group of coils comprises first, second and third coils (P1a, P1b, S1) and wherein the second group of coils comprises first, second and third coils (P2a, P2b, S2). Electrical device according to Claim 3, in which the at least one electrical connector (Ba, Bb, Bs) comprises:

• a first electrical connector (Ba) connecting together two respective first ends of the two first coils (P1a, P2a);
• a second electrical connector (Bb) connecting together two respective first ends of the two second coils (P1b, P2b); And
• a third electrical connector (Bs) connecting together two first ends of the two third coils (S1, S2).

Electrical device according to claim 1 or 2, further comprising a magnetic core (N) comprising a first branch (N1), a second branch (N2) and a third branch (N3) joining at their ends and having respective reluctances, the reluctance of the third branch (N3) being lower both than that of the first branch (N1) and that of the second branch (N2). Electrical device according to any one of Claims 1 to 5, in which at least one of the coils of the first group is designed to generate a first magnetic flux in the first branch (N1), looping back through the third branch (N3), in which at least one of the coils of the second group is designed to generate a second magnetic flux in the second branch (N2), looping back through the third branch (N3), and in which these coils generating the first and second magnetic fluxes are wound in opposite directions respective windings such that the first and second magnetic fluxes traverse the third branch in opposite directions. Voltage converter comprising an electrical device according to any one of claims 1 to 6. Voltage converter according to the preceding claim, forming a direct storage converter. Method of manufacturing a device according to any one of Claims 1 to 6, comprising:

• obtaining (302) the first and second groups of coils coupled with the at least one electrical connector (Ba, Bb, Bs);
• securing (304) the first and second groups of coupled coils to the printed circuit board (108); And
• connecting (306) the coils and electrical connectors (Ba, Bb, Bs) to the traces of the printed circuit board (108).