EP1826785B1

EP1826785B1 - Transformer and circuit comprising said transformer

Info

Publication number: EP1826785B1
Application number: EP06425111A
Authority: EP
Inventors: Danilo Bizzarri
Original assignee: Power One Italy SpA
Current assignee: Power One Italy SpA
Priority date: 2006-02-23
Filing date: 2006-02-23
Publication date: 2010-09-08
Anticipated expiration: 2026-02-23
Also published as: DE602006016723D1; ATE480859T1; EP1826785A1

Abstract

The transformer for electrical or electronic circuits comprises a ferromagnetic core (3), combined with which are at least a first winding core (7)) and a second winding core (7) for winding conducting wire (F). Also provided are a first conducting foil (9) applied to the first winding core (7) and a second conducting foil (9) applied to the second winding core (7), said conducting foils forming part of at least one winding of the transformer.

Description

The present invention relates to a transformer for electrical and/or electronic circuits of the type comprising at least one winding formed by a bent conductive foil.
US-A-5,175,525 discloses a transformer including:

a ferromagnetic core;
combined with said ferromagnetic core, a winding core for winding a conducting wire, said core having a pair of connectors for the ends of the conducting wire wound therearound;
a conducting foil applied to said winding core and forming a secondary winding of the transformer, said conducting foil having two appendages forming electric connections for connecting the secondary winding to a circuit.

JP57063817 discloses a transformer incorporating a pair of switches, one on the primary side and one on the secondary side. The primary winding and the secondary winding are divided each in two portions. Respective switches are provided both in the primary as well as in the secondary winding. Said switches connect said winding portions to one another and to the outside electric connections with which the transformer is connected to the electronic or electric circuit. The switches can switch from one mode of operation to another mode of operation depending upon the load across the transformer. In one mode of operation both the portions of the primary winding as well as the portions of the secondary winding are arranged in parallel, for reducing the losses in case of large electric current crossing the transformer. In the second mode of operation they are both connected in series, to reduce the magnetic flux density through the core in case of a limited amount of current crossing the transformer.
The object of the present invention is to produce a particularly versatile transformer, suitable to be utilized in different configurations utilizing the same basic components. This object is achieved with a transformer according to claim 1. The dependent claims relate to preferred embodiments of the transformer according to the invention.
In substance, the invention relates to a transformer for electrical or electronic circuits comprising: a ferromagnetic core; combined with said ferromagnetic core at least a first winding core and a second winding core for winding conducting wire; a first conducting foil applied to the first winding core and a second conducting foil applied to the second winding core, said conducting foils forming at least part of a winding of the transformer.
With a configuration of this type it is possible to produce a compact and versatile transformer, which can, for example, be used to connect the conducting foils in series or in parallel on the printed circuit and similarly to connect the conducting wires wound around the two winding cores in series or in parallel with each other, in order to utilize the same transformer in different applications.
In a preferred embodiment, the winding cores each have a central body for winding the conducting wire and two flanges. Preferably, each of said conducting foils forms two winding turns which can be positioned on the outside of the respective winding core, resting on the outer face of the two flanges of said winding core.
To obtain efficient and accurate reciprocal positioning between winding core and foil, according to an advantageous embodiment of the invention, at least one of the flanges of each winding core has a seat for housing a portion of the respective conducting foil. In a possible embodiment, the portion of the conducting foil forms a connection between the first and the second turn formed by the respective conducting foil, and the seat is formed on the rim of one of the two flanges of the respective winding core, to receive said connecting portion.
According to a possible improvement of the invention, at least one flange and preferably both flanges of each winding core has reciprocal positioning stops between the winding core and the ferromagnetic core.
In a possible embodiment, each of the winding cores has a pair of connectors for the ends of the conducting wire wound therearound. The pairs of connectors of the two winding cores can preferably be superimposed on each other, to obtain an optimal configuration of the connections to the electronic circuit.
According to an improved embodiment of the invention, each winding core has an auxiliary connector for an auxiliary conducting wire forming a further winding. The auxiliary connectors of the two winding cores are also preferably superimposed when the transformer is assembled.
The invention also relates to an electrical or electronic circuit comprising a transformer of the aforesaid type.
Further advantageous features and preferred embodiments of the invention are indicated in the appended claims and will be described in greater detail with reference to an example of embodiment of the invention.
The invention will be better understood by following the description and accompanying drawing, which shows a non-limiting practical embodiment of the invention. More specifically, in the drawing:

Figure 1 shows an exploded view of a transformer according to the invention, in which for clarity of representation the winding formed by wire wound on the two winding cores has been omitted;
Figure 2 shows a front view from the side of the connections;
Figure 3 shows a plan view according to III-III in Figure 2;
Figure 4 shows an axonometric view of the assembled transformer;
Figure 5 shows, in three perspective views according to different orientations, one of the winding cores of the transformer;
Figure 6 shows a front view of the single winding core;
Figure 7 shows a plan view and partial section according to VII-VII of Figure 6;
Figure 8 shows a bottom view according to VIII-VIII in Figure 6;
Figure 9 shows a flat development of one of the foils forming the other winding of the transformer; and
Figure 10 shows one of the insulating elements applied to the conducting foils.

With reference in particular to Figures 1 to 4, the transformer as a whole is indicated with 1 and comprises a ferromagnetic core 3 formed of two portions 3A and 3B coupled with each other. The two portions 3A, 3B of the ferromagnetic core 3 each have a base 3C, side walls 3D and a central expansion 3E.
The transformer also comprises two winding cores made of a plastic material, indicated with 7, substantially identical to each other. Each winding core 7 (see in particular Figures 1, 5, 6 and 7) has a central body 7A and two flanges 7B, 7C. A conducting wire F (indicated in Figure 6 and omitted for clarity of the drawing in the remaining figures) is wound around the central body 7A and between the two flanges 7B, 7C. The wire F is suitably insulated, i.e. by a triple insulation.
In the assembled position, the central expansions 3E of the two portions 3A, 3B of the ferromagnetic core 3 are inserted in the hollow area inside the body 7A of the two winding cores 7. Each winding core 7 is enclosed superiorly and inferiorly by two respective turns 9A, 9B formed by respective conducting foils 9. The form of each conducting foil forming the turns 9A, 9B associated with each winding core 7 will be described in greater detail hereunder with reference to Figures 1 and 9.
The two turns 9A and 9B formed by each conducting foil 9 are joined by an intermediate connecting portion 9C, which is housed inside a seat 7E provided along the edge of one of the flanges of the respective winding core 7. With this arrangement the reciprocal angular position between each winding core 7 and the corresponding foil 9 forming the two turns 9A, 9B, is defined.
Each winding core 7 also has profiles 7F produced on the corresponding flanges 7B, 7C, which form a stop between the winding cores and the portions 3A, 3B of the ferromagnetic core 3. In this way the reciprocal angular position between each winding core 7 and the ferromagnetic core 3A, 3B is also defined.
Each winding core 7 has, in an expansion of the flange 7C, two connectors 13 to which the ends of the conducting wire F, wound around the respective winding core, are advantageously soldered. In practice, the plastic material forming each winding core 7 forms seats in which conducting pins (not shown), which form the actual connectors 13, are inserted.
An auxiliary connector 15 is provided on the opposed flange 7B of each winding core 7. In practice, the connectors 13 and 15 are on opposite sides of a median plane containing the axis of the winding core and orthogonal to the planes on which the flanges 7B, 7C lie. Once assembled, the transformer thus has two pairs of connectors 13 for two conducting wires F wound on two winding cores 7 and two auxiliary connectors 15 for an optional conducting wire forming an auxiliary winding, not shown. As can be observed in particular in Figures 2 and 4, in the assembled position the pairs of connectors 13 are superimposed on each other on the same side of a median plane of the transformer, while the auxiliary connectors 15, again superimposed, are positioned on the opposite side of said plane.
As can be seen in the accompanying drawing, the connectors 13 and 15 of each winding core 7 are formed by protrusions made of the same basic material of the flanges 7B, 7C of the respective winding core 7. These protrusions form (Figures 3 and 4) further reciprocal angular positioning stops between the winding core 7 and the ferromagnetic core 3, 3A, 3B.
The turns 9A, 9B which externally enclose the two flanges 7B, 7C of each winding core 7 are formed by bending of a conducting foil the flat development of which is shown in Figure 9. This conducting foil, for example produced by die cutting from a sheet of copper or the like, has a first substantially annular portion 17A, and a second substantially annular portion 17B, each of said substantially annular portions 17A, 17B forming one of the turns 9A, 9B of the foil which, after bending, are positioned superimposed and coaxial.
Each annular portion 17A, 17B has interruptions at the level of a radial line 17C (Figure 9). Adjacent to the interruption line 17C each portion 17A, 17B has a projection 17D forming, once the foil has been bent to form the two coaxial turns 9A, 9B in a superimposed and axially staggered position, electrical connections towards an electronic circuit board (not shown), on which the transformer is assembled.
Extending between the two projections 17D is the connecting portion 9C, which joins the annular portions 17A, 17B. This connecting portion 9C is bent through 90° along the lines 9L (figure 1) so that the portions 17A, 17B of the conducting foil are superimposed in a coaxial position before enclosing the corresponding winding core 7.
A sheet of insulating material, the flat development of which is shown in Figure 10 and indicated therein with 21, is applied to the outer faces of each of the two conducting foils shown in Figure 9. The insulating sheet 21 applied to the outside of the turns 9A, 9B effectively insulates, with respect to each other, the turns 9B, 9A superimposed with and adjacent to each other positioned between the two winding cores 7 when the transformer is assembled.
Once completed and provided with the two windings, formed by the wires F around each winding core 7, and with the conducting foils forming the turns 9A, 9B, the transformer has at least four electrical connections towards the outside, formed by the projections 17D for electrical connection of the turns 9A, 9B and two pairs of connectors 13 for the wire F forming the winding on each winding core 7.
On the electronic circuit board on which the transformer is assembled there can be various types of electrical connections between these connectors. It is thus possible to connect the two wires forming the winding F around the two winding cores 7 in series or, alternatively, in parallel with each other. Likewise, the two pairs of turns 9A, 9B formed by the two conducting foils and which enclose the two winding cores 7 can be connected with each other in series or in parallel. It is thus possible with the same basic elements to produce transformers with various characteristics where the primary winding and secondary winding are formed by the two wires F and by the two pairs of turns 9A, 9B formed by the conducting foils in Figure 9, or vice versa.
This results in a highly versatile electronic component which, with the same dimensions and spaces occupied, can be utilized to produce transformers with characteristics differing even substantially from one another.
It is understood that the drawing only shows an example provided by way of a practical arrangement of the finding, which may vary in forms and arrangement without however departing from the scope of the concept on which said finding is based. Any reference numerals in the appended claims are provided purely for the purpose of facilitating reading of the claims with reference to the description and to the drawing and do not limit the scope of protection represented by said claims.

Claims

A transformer for electrical or electronic circuits, comprising:
- a ferromagnetic core (3);

- combined with said ferromagnetic core at least a first winding core (7) and a second winding core (7) for winding conducting wire (F), each of said winding cores having a respective pair of connectors (13) for the ends of the conducting wire (F) wound therearound;

- a first conducting foil (9) applied to said first winding core (7) and a second conducting foil (9) applied to said second winding core (7), said conducting foils forming at least part of a winding of the transformer, each of said conducting foils (9) forming two winding turns (9A, 9B);
wherein said first and second conducting foils form four electrical connections towards the outside, formed by projections (17D) for electrical connection of said turns (9A, 9B) and wherein at least one of the flanges of each winding core has a seat (7E) for housing a portion (9C) of the respective conducting foil.
Transformer as claimed in claim 1, wherein said first and said second winding cores (7) each have a central body (7A) for winding the conducting wire and two flanges (7B; 7C).
Transformer as claimed in claim 2, wherein each of said conducting foils is applied to the outside of the respective winding core, with the two turns (9A, 9B) formed by each foil in contact with the outer surface of the flanges (7A, 7B) in the respective winding core.
Transformer as claimed in one or more of the preceding claims, wherein said four electrical connections formed by said first and second conducting foils and said pairs of connectors (13) for the ends of the conducting wire (F) wound around each winding core are arranged on the same side of the ferromagnetic core (3).
Transformer as claimed in one or more of the preceding claims, wherein: said portion (9C) of the conducting foil forms a connecting portion between the first and the second turn (9A, 9B) formed by the respective conducting foil, and said seat (7E) is formed on the rim of one of the flanges of the respective winding core (7), to receive said connecting portion.
Transformer as claimed in one or more of claims 2 to 5, wherein at least one flange (7B; 7C) of each winding core (7) has reciprocal positioning stops (7F) between the winding core (7) and the ferromagnetic core (3).
Transformer as claimed in one or more of the preceding claims, wherein the pairs of connectors (13) of two winding cores (7) are superimposed on each other.
Transformer as claimed in one or more of the previous claims, wherein each winding core (7) has an auxiliary connector (15).
Transformer as claimed in claim 8, wherein said auxiliary connectors (15) of the two winding cores (7) are superimposed on each other.
Transformer as claimed in claim 9, wherein said auxiliary connectors (15) and said pairs of connectors (13) are positioned on opposite sides of said seats (7E) for housing said portions (9C) of the conducting foils.
Transformer as claimed in one or more of claims 8 to 10, wherein in each winding core (7) the pair of connectors (13) is produced on a first flange (7B) and the auxiliary convector (15) is produced or a second flange (7C).
Transformer as claimed in one or more of claims 8 and 11, comprising an auxiliary winding, the ends of which are connected to said auxiliary connectors (15) of the two superimposed winding cores (7).
Transformer as claimed in one or more of the previous claims, wherein said connectors (13) and said auxiliary connectors (15) are produced in protrusions of the flanges (7B, 7C) of the winding cores (7).
Transformer as claimed in claim 13, wherein said protrusions form reciprocal positioning stops between the winding cores (7) and the ferromagnetic core (3).
Transformer as claimed in one or more of the previous claims, wherein each conducting foil has, in a flat development, a first annular portion (17A) and a second annular portion (17B), said annular portions each being interrupted in a radial section (17C) and being connected to each other by a connecting portion (9C), said connecting portion being bent to bring the two annular portions (17A, 17B) into a substantially coaxial position.
Transformer as claimed in claim 15, wherein each connecting portion (9C) is produced adjacent to said radial interruption section (17C).
Transformer as claimed in claim 15 or 16, wherein each annular portion has a projection (17D) forming an electrical connection positioned adjacent to said radial interruption section.
Transformer as claimed in claim 17, wherein in the bent and assembled position, the projections (17D) of each conducting foil (17A, 17B, 9C, 17D) are angularly staggered, the connecting portion (9C) being positioned in an intermediate position between said projections (17D).
Transformer as claimed in one or more of the previous claims, wherein each of said conducting foils has a face to which a sheet or foil of insulating material (21) is applied, said face facing towards the outside of the conducting foil when this is bent and assembled on the ferromagnetic core (3) and on the respective winding core (7).
An electrical or electronic circuit comprising a transformer as claimed in one or more of the previous claims, assembled on a circuit board.
Circuit as claimed in claim 20, wherein the windings of conducting wire wound around the two winding cores are connected to each other in series.
Circuit as claimed in claim 20, wherein the windings of conducting wire wound around the two winding cores are connected to each other in parallel.
Circuit as claimed in claim 20, 21 or 22 wherein the two conducting foils are connected to each other in series:
Circuit as claimed in claim 20, 21 or 22, wherein the two conducting foils are connected to each other in parallel.