FR3045921B1

FR3045921B1 - INDUCTANCE CIRCUIT INCORPORATING A PASSIVE THERMAL MANAGEMENT FUNCTION

Info

Publication number: FR3045921B1
Application number: FR1562598A
Authority: FR
Inventors: Gerard Delette
Original assignee: Commissariat a lEnergie Atomique CEA; Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Current assignee: Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Priority date: 2015-12-17
Filing date: 2015-12-17
Publication date: 2019-07-12
Anticipated expiration: 2035-12-17
Also published as: CN108475574B; WO2017103074A1; EP3391393A1; JP2019504488A; FR3045921A1; KR20180095030A; ES2915837T3; JP6895967B2; PL3391393T3; EP3391393B1; CN108475574A

Abstract

L'invention concerne un circuit à inductance comprenant : a) un noyau (20) fait d'un matériau magnétique, monobloc comprenant un cadre (21), et une barre (30) disposée au centre du cadre (21) de manière à former deux boucles magnétiques rectangulaires, symétriques par rapport à la barre (30), contigus au niveau d'un plan de symétrie de la barre (30), et de longueur magnétique effective I, les parties droites des boucles magnétiques présentent une section transversale de surface A, b) une bobine (40) comprenant un nombre de N spires, c) des ailettes (50) exposées à l'environnement extérieur et destinées à dissiper de la chaleur, le circuit à inductance étant caractérisé en ce que les ailettes (50) sont comprises dans au moins une zone volumique du cadre (21), disposée dans le prolongement d'au moins une extrémité de la barre (30).An inductance circuit comprising: a) a core (20) made of a one-piece magnetic material comprising a frame (21), and a bar (30) disposed at the center of the frame (21) to form two rectangular magnetic loops, symmetrical with respect to the bar (30), contiguous at a plane of symmetry of the bar (30), and of effective magnetic length I, the straight portions of the magnetic loops have a surface cross-section A, b) a coil (40) comprising a number of N turns, c) fins (50) exposed to the external environment and intended to dissipate heat, the inductance circuit being characterized in that the fins (50 ) are included in at least one volume zone of the frame (21), arranged in the extension of at least one end of the bar (30).

Description

INDUCTANCE CIRCUIT INCORPORATING A PASSIVE THERMAL MANAGEMENT FUNCTION

DESCRIPTION

TECHNICAL FIELD AND PRIOR ART The invention relates to an inductance circuit comprising a monoblock core integrating a passive thermal management function.

FIG. 1 represents an inductance circuit known from the state of the art and described in US Pat. No. 6,920,039 B2, comprising: a) a core 1 made of a one-piece magnetic material having a volume dimension V, comprising a frame 2 , and a bar 3 arranged in the center of the frame 2 so as to form two rectangular magnetic loops, symmetrical with respect to the bar, contiguous at the plane of symmetry of the bar, and of effective length I, the straight portions of the magnetic loops have a surface cross section A, b) a coil 4 comprising N turns around the bar 3, c) fins 5 exposed to the external environment and intended to dissipate heat,

The fins are attached to the outer side surface of the core 1.

An induction circuit has an inductance L determined by the quantities A, I and N, as well as by the magnetic permeability μΓ of the core 1, and is given by the following relation:

In other words, the geometry of the core 1, and more particularly the ratio of the geometric factors I and A, determines the value of the inductance of the inductance circuit.

Such an induction circuit is, for example, used in power converters whose function is to adapt the voltage and the current delivered by a source of electrical power to power an electrical system.

A power converter also comprises electronic components functioning as switches (active components) switching at a given frequency f, and thus make it possible to supply the magnetic excitation coil 4.

In the case of DC / DC converters for example, the active components are transistors that are used to "cut" the input voltage in regular cycles. In order to deliver a DC output voltage, inductance circuits are used to store and destock the electrical energy on each cycle and to smooth the output voltage to its average value.

In operation, the electric current, delivered by the active components, flows through the magnetic excitation coil 4, and thus generates a magnetic flux, comprising two closed symmetrical loops, in the core 1.

As illustrated in FIG. 2, the magnetic flux originates in the bar 3 along the axis of symmetry, and flows symmetrically from one end of the bar 3 into the frame 2 to loop back into the other end of the bar 3.

Inductance circuits can represent up to 40% of the volume and cost of the converter.

Also, the volume of a circuit with inductance can be reduced by the use of magnetic cores comprising a material with high magnetic permeability, for example pr> 50. Among the magnetic materials having a high magnetic permeability, mention may be made of the oxides of ferrite type, and more particularly the materials: Mni-xZnxFe204 and Nii-xZnxFe204.

The volume of the inductance circuits can also be reduced by increasing the operating frequency of the inductor circuits. For example, the active components may include transistors made on Gallium Nitride (GaN). These allow to reach switching frequencies higher than 1 MFIz. In this respect, those skilled in the art will be able to consult the document AM LEARY [2]. The flow of the magnetic flux in the core 1 is accompanied by magnetic losses, which result in a heating of the core.

This heating of the core can degrade the performance of the inductance circuit, and ultimately render it inoperative.

Decreasing the core volume, enabled by the use of magnetic materials constituting the core of high magnetic permeability and / or by increasing the operating frequency of the inductance circuit, exacerbate this heating.

Heat dissipation means are then added to the inductor circuit to better manage the amount of heat created during operation of the inductor circuit.

The heat dissipation means, as shown in FIG. 1, generally take the form of fins disposed outside the core and attached to the outer surface of said core, so as to increase the exchange surface of the core. 1 with the surrounding air.

The fins 5 thus disposed do not modify the geometrical factors of the core 1, and thus leave the value of the magnetic induction of the inductance circuit unchanged. However, these means of heat dissipation are not satisfactory. Indeed, the volume occupied by the dissipation means is added to the volume of the inductor, and also increase its mass. Moreover, to be effective, the fins 5 must have a large exchange surface, and therefore occupy a relatively large volume relative to the core.

However, for some applications, it is desirable, even primordial, that the inductor circuits equipped with their heat dissipation means occupy the smallest possible volume.

Inductance circuits then require dissipation means operating more efficiently than those known from the state of the art, particularly in the fields of aeronautics and the automobile.

More particularly, the management of the heat dissipation must also be optimized for induction circuits involving the use of magnetic cores 1 having a magnetic permeability greater than 50, and / or operations of said circuits at high frequencies, for example greater than 1 MHz.

An object of the invention is then to provide an inductance circuit having more efficient heat dissipation means, and while limiting the increase in volume and mass of said circuit.

STATEMENT OF THE INVENTION

The object of the invention is then achieved by an inductance circuit comprising: a) a core made of a magnetic material, monobloc, volume compactness V, comprising a frame, and a bar disposed in the center of the frame so as to forming two rectangular magnetic loops, symmetrical with respect to the bar, contiguous at a plane of symmetry of the bar, and of effective magnetic length I, the straight portions of the magnetic loops have a surface cross-section A, b) a coil comprising a number of N turns intended to generate a magnetic induction in the bar, c) fins exposed to the external environment and intended to dissipate heat, the fins being included, at least in part, in at least one zone volume of the frame, arranged in the extension of at least one end of the bar.

The inductance circuit, when devoid of fins in the at least one volume zone of the frame, has an inductance equal to the nominal inductance L defined by the quantities A, I and N.

Furthermore, for an induction circuit without fins, and in operation, the at least one volume zone is also traversed by magnetic induction lines.

The cross section in the straight parts of the frame is the same for each straight part, and is rectangular.

Unlike the state of the art, the fins are thus in the volume of the core involved in the circulation of the magnetic induction lines.

The Applicant has found that there are areas for which the local magnetic induction is very low, and contribute very little to the magnetic characteristics of the inductance circuit. The Applicant proposes to use at least one of these areas in the core to form fins. Thanks to these provisions, the Applicant obtains a remarkable level of cooling. For example, the Applicant has been able to observe that the presence of fins, according to the invention, makes it possible to change the temperature of the core of the inductance circuit in operation from 250 ° C. to 110 ° C. Moreover, the presence of fins has little or no effect on the inductance of the inductance circuit with respect to the nominal inductance.

Thus, the fins are formed directly in the core volume. The fins may also be formed without additional material, and therefore without affecting the bulk volume of the core.

Furthermore, the arrangement of the fins in a volume zone of the core and arranged in the extension of the bar, allows to create a heat exchange surface closest to the hottest core zone.

In addition, the operation of an inductance circuit at frequencies above 1 MHz is no longer a brake. Indeed, the increase in temperature due to the rise in frequency is perfectly managed by the fins according to the invention.

According to one embodiment, the fins are disposed in a bottom of at least one recess formed in the at least one volume zone of the frame, said at least one recess opening on an outer lateral surface of said frame, and passing through apart from the frame in a direction perpendicular to the plane of the frame.

Thus, the shape of the recess makes possible a more efficient ventilation of the fins, and therefore a better cooling of the core.

According to one mode of implementation, the at least one recess flares from its bottom to the outer lateral surface of the frame.

According to one embodiment, the at least one recess has a section, parallel to the plane of the frame, having constant dimensions in a direction perpendicular to the plane of said frame, said section is advantageously trapezoidal, more advantageously isosceles trapezoidal.

According to one embodiment, the fins are arranged so that the relative difference between the inductance of the inductance circuit and the nominal inductance L is less than 5%, preferably less than 2%.

According to one embodiment, the at least one volumetric zone is a zone for which, when the inductance circuit is in operation, the local magnetic induction is less than 5% of the value of the average magnetic induction in the core.

According to one embodiment, the fins are parallel to the plane defined by frame.

According to one embodiment, the surface developed by each fin is between 10 and 100% of the area A.

According to one mode of implementation, the fins disposed in the at least one volume zone leave the space bulkiness of the frame unchanged.

According to one embodiment, additional fins are attached to the outer lateral surface of the frame.

According to one mode of implementation, the bar has a square section, and is traversed right through in a direction perpendicular to the plane of the frame by cavities, the cavities being filled by an electrical conductor so as to form a part of the coil.

According to one embodiment, the space between the fins is filled with a metallic material, preferably a metal material selected from: aluminum, copper. The invention also relates to a method of manufacturing an inductance circuit comprising the steps of: a) drawing up a theoretical map of the magnetic flux lines in a core of a circuit with inductance in operation, said inductance circuit having a predetermined inductance value L, b) identifying, from the mapping previously drawn up, the volume zones of said core, of the inductance circuit in operation, for which induction magnetic field is less than 5% of the value of the average magnetic induction in the core, c) manufacture the core considered in step a), fins being included, at least in part, in at least a part of the zones of volumes identified in step b), d) forming a coil of conductive material around a portion of the core.

According to one embodiment, in step a), the core is made of a magnetic material, one-piece, of bulk volume V, comprises a frame, and a bar arranged in the center of the frame so as to form two rectangular magnetic loops, symmetrical with respect to the bar, contiguous at the plane of symmetry of the bar, and effective magnetic length I, the straight portions of the magnetic loops have a surface cross-section A.

According to one embodiment, the fins formed in the core in step c) are arranged in the extension of at least one end of the bar.

According to one embodiment, following step c), a step of cl) of filling with a metallic material of the space between the fins is carried out.

According to one embodiment, the step c) of manufacturing the core is performed for injection molding powder.

BRIEF DESCRIPTION OF THE DRAWINGS Other features and advantages will appear in the following description of the embodiments of an inductance circuit according to the invention, given by way of nonlimiting examples, with reference to the appended drawings in which: FIG. 1 is a view from above of a schematic representation of an inductive circuit known from the prior art. FIG. 2 is a schematic representation of the path of the magnetic flux in an inductance circuit known from the prior art. - Figure 3 is a top view of a schematic representation of the effective magnetic path in a magnetic core, included in a known inductive circuit of the state of the art. - Figure 4 is a top view of a schematic representation of an inductive circuit according to an embodiment of the invention. FIG. 5 is a map of the magnetic induction lines in the core of an inductive circuit known from the prior art. FIG. 6.a is a simulation of the temperature distribution in a core devoid of heat dissipation means known from the prior art. FIG. 6.b is a simulation of the temperature distribution in a core according to an exemplary embodiment of the invention. FIG. 7 is a view from above of a schematic representation of an inductance circuit according to an embodiment of the invention.

DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

For the different modes of implementation, the same references will be used for identical elements or ensuring the same function, for the sake of simplification of the description. Definitions:

Effective magnetic length I (effective magnetic path length): The effective magnetic length (Leff) is defined as the length of the closed contour taken in the magnetic core on which the mean magnetic field flow (Hmoy) is equal to the sum of the currents (number of turns N multiplied by the nominal current I) crossing the circuit (Ampère theorem). In other words: Hmoy.Leff = N * l. An example of an effective magnetic path is given in FIG. 3. In this example, the core forms a rectangular loop, and the effective magnetic path associated with this configuration is shown in broken lines.

Cross Section: cross section means the section resulting from the intersection of a plane perpendicular to the longitudinal axis of an elongated element.

Nominal inductance L: value of the inductance L defined by the effective magnetic length I, the surface A, and the number of turns N, and according to the relation: L =

In Figure 4, we can see an embodiment of an inductor circuit 10 according to the present invention. It is a circuit with inductance 10 of inductance Lm defined by the geometrical characteristics of the core and the number of turns N.

In the remainder of the description, an example of an inductance circuit 10 will be described.

The inductor circuit 10 according to the invention comprises a core 20.

The core 20, according to the invention, is made of a magnetic material, monobloc, of bulk volume V, comprising a frame 21, and a bar 30 disposed in the center of the frame 21 so as to form two rectangular magnetic loops, symmetrical relative to the bar 30, contiguous at a plane of symmetry of the bar 30, and effective length I, the straight portions of the magnetic loops have a surface cross-section A.

The frame 21 defines a plane, which we will call plan of the frame in the following description. The surface imprint of the frame 21 (or the intersection of the frame with a plane parallel to the plane of the frame) is a rectangle having a surface S.

The cross section in the straight portions of the frame 21 is the same for each straight portion, and is advantageously rectangular.

The cross section of the bar 30 may be square, rectangular or circular.

Advantageously, the core 20 comprises a magnetic material of magnetic permeability greater than 50 (pr> 50).

For example, the magnetic material may comprise a ferrite oxide of spinel crystallography structure. Indeed, the magnetic permeability of such materials is stable in the high frequency range. The most common magnetic materials respond to the formulation:

For example, a core 20 comprising Mni-xZnxFe204, where x is between 0.3 and 0.6, the magnetic permeability μΓ changes with x, and is between 500 and 1000.

A preferred embodiment for the core 20, which will be presented in the remainder of the disclosure, comprises the injection molding of ferrite powder NiZn or MnZn ("PIM" or "Powder Injection Molding" according to the terminology

Anglo-Saxon).

Advantageously, the ferrite type materials also have high electrical resistivity values, which makes it possible to limit the losses due to induced currents.

The materials Mni-xZnxFe204 and Nii-xZnxFe2C> 4 also have the advantage of being available on an industrial scale.

The core 20 comprises a frame 21 of thickness e. The straight portions of the frame 21 have a surface cross-section A.

The frame 21 also includes four outer lateral faces defining an outer lateral surface 22. The outer lateral surface 22 is perpendicular to the plane of the frame.

The frame 21 comprises four inner faces defining an inner surface 23, also perpendicular to the plane of the frame.

We define the bulk volume V of the frame 21 by its volume footprint. More particularly, the bulk volume V of the frame 21

is then the product of the thickness e and the area S. The bulk volume V of the frame 21 is also equal to the bulk volume V 'of the core 20.

The core 20 comprises the surface cross-section bar 2A (the area of the surface cross section 2A of the bar is therefore substantially twice the area of the cross-sectional area A of the straight portions of the frame ) and connects two opposite faces of the inner surface 23 of the frame 21, so as to form two symmetrical magnetic loops of effective magnetic length I, and contiguous in a plane of symmetry of the bar 30.

The bar 30 comprises an axis of symmetry extending along its length (represented by the axis XX 'in FIG. 4).

The configuration thus described is a typical case of core 20 used in an inductance circuit 10, and is generally referred to as an EE configuration, possibly a two-part EE configuration.

Such a configuration is generally obtained by assembling two half parts. Each half game includes a half frame and a half bar.

Possibly the half bar is shorter than the two half side portions of the half frame. Thus, the bar 30, formed by the two half bars, has an air gap ("airgap" according to the terminology Anglo-Saxon).

The inductor circuit 10 comprises a magnetic excitation coil 40 comprising a number of N turns. The coil 40, of magnetic excitation, when traversed by a current, is intended to create a magnetic induction in the bar 30. The N turns of the coil 40 may be formed around the bar 30. The coil 40 Magnetic excitation is metal, for example copper. The magnetic excitation coil 40 comprises a continuous wire wound around the bar 30, so as to form the N turns.

The core 20 includes heat dissipation means.

The heat dissipation means may take the form of fins 50 exposed to the external environment.

The fins 50 increase the heat exchange surface of the core 10 with the external environment, and thus make it possible to cool more efficiently when the inductor 10 is in operation.

According to the invention, the fins 50 are included, at least in part, in at least one volume zone of the frame 21, arranged in the extension of at least one end of the bar 30.

The at least one volume zone may comprise a first volume zone 24a, and a second volume zone 24b

For example, the core is provided with two sets of fins 50, included, respectively, at least partially in the first volume zone 24a, and the second volume zone 24b of the frame 21.

The first volume zone 24a and the second volume zone 24b may be arranged symmetrically along a plane passing through the center of the bar 30, and perpendicular to the longitudinal axis of said bar 30.

Advantageously, the fins 50 are arranged in the bottom of at least one recess formed in the at least one volume zone of the frame 21, said at least one recess opening on the outer lateral surface 22 of said frame 21.

The at least one recess may comprise a first recess 25a and a second recess 25b.

The first recess 25a and the second recess 25b are included, respectively, in the first volume zone 24a and the second volume zone 24b.

Advantageously, each recess 25a and 25b transverse through the frame 21 in a direction perpendicular to the plane of said frame 21.

In the example shown in Figure 4, each recess 25a and 25b may comprise a flat bottom parallel to the outer side face of the frame 21 on which it opens.

A set of fins 50 is then projecting from the bottom of each recess 25a and 25b.

Thus, the arrangement of the fins 50 on the bottom of at least one recess increases the exchange surface and position the latter as close to the bar 30.

Indeed, the Applicant has found that the greatest temperature increase occurs in the bar 30 when the inductor circuit 10 is in operation. For example, Figure 6.a shows the temperature distribution of a core 1 of an inductance circuit, known in the state of the art, in operation, and devoid of heat dissipation means. The general characteristics of the nucleus considered are given in Table 1.

Table 1.

It can then be seen that the core 1 comprises a hot zone B (at the level of the bar 3) for which a temperature of 250 ° C. is reached, whereas a temperature below 170 ° C. is observed in the lateral zones C1 and C2 of the core 1.

Furthermore, unlike the solutions proposed by the prior art and more particularly US 6,920,039 B2, the configuration of the fins 50 according to the invention does not impose a significant increase in volume.

Advantageously, the fins 50 may be perpendicular to the plane of the bottom on which they rest.

Still advantageously, the fins 50 may be entirely within the volume defined by the at least one recess. In the example of Figure 4, the addition of heat dissipation means does not cause an increase in volume of the core 20.

Thus, the bulk volume of the core 20 is not affected.

Alternatively, the fins 50 may extend beyond the volume defined by the at least one recess.

Thus, longer fins increase the exchange surface of the core with the external environment, thus making induction device cooling more efficient when the latter is in operation.

According to a particularly advantageous embodiment, the first recess 25a and the second recess 25b widen from their respective bottom to the outer lateral face on which they open. Thus, as illustrated in FIG. 6b, better ventilation is provided at the fins 50. Each recess 25a and 25b has a section, parallel to the plane of the frame 21, having constant dimensions in a direction perpendicular to the plane of said frame. 21. Said section may be trapezoidal, more particularly trapezoidal isosceles.

The fins 50 may be parallel or perpendicular to the plane defined by frame 21.

As a variant, the recess may have, in a nonlimiting manner, a U-shaped section. The recess may also have a cross section in accordance with the section of the volume zone, for example the recess may conform to the shape of the zone. volume.

Thus, fins 50, extending from the lateral surface 22 in a volume zone of the frame 21, said first zone being disposed in the extension of the bar 30, make it possible to create a heat exchange surface as close as possible to the hot zone of the nucleus.

According to a second example, FIG. 6b represents a simulated map of the temperature of an inductance circuit equipped with heat dissipation means according to another embodiment of the invention (the fins 50 exceed the volume V of the core ). A temperature of 110 ° C. is then observed both in the bar (zones C1 and C2) and in the frame (zone B). The temperature is not only much lower, but also more homogeneous in the core.

Thus, the formation of fins 50 in the core 20, according to the invention, is performed so as to optimize their efficiency in terms of heat dispersion, while only moderately affecting the inductance inductance circuit.

Advantageously, the fins 50 are arranged to modify only moderately the inductance of the inductance circuit 10. Preferably, the inductance Lm of an inductance circuit 10 has a deviation from the nominal inductance L less than 5%, even more preferentially, the difference is less than 2%.

In order to minimize the difference between the inductance of an inductance circuit 10 according to the invention with respect to the same inductance circuit 10, but devoid of heat dissipation means, the following protocol can be adopted:

In a first step, an inductance circuit, devoid of heat dissipation means, characterized by the geometric parameters A and I of its core, and the number of turns N of the coil, is considered.

A mapping of the magnetic flux lines in the kernel is then calculated accurately, using for example a finite element calculation code, considering the reference geometry determined in the first step. Numerical simulations in two or three dimensional finite elements are well known to those skilled in the art and are not detailed in this description. The zones of the core where the local magnetic induction remains less than 5% of the value of the average magnetic induction in said core are identified in black in FIG.

In the example illustrated in FIG. 5, the first part of the volume of the core is advantageously identified with the zone where the magnetic induction remains less than 5% of the value of the average magnetic induction in the core, and arranged in the extension of at least one end of the bar.

This method makes it possible to identify in a fine manner the areas of the core volume in which the fins 50 can be made in the core, and while modifying only moderately the inductance of the inductor circuit 10 considered.

Particularly advantageously, the fins 50 are parallel to the field lines that can be created when the inductor 10 is in operation. Thus, the difference between the inductance of said circuit and the nominal inductance can be reduced.

Moreover, the surface developed by each fin may be between 10 and 100% of the area A, for example 30%.

The depth of the fins 50 may be between 10 and 50% of the square root of the surface A, for example 30%.

For a core whose bar 30 is cylindrical and of diameter equal to 6 mm.

The width of the fins 50 may be between 0.1 and 2 mm, for example 1 mm. The spacing of the fins 50 may be between 0.1 and 0.5 mm, for example 0.2 mm.

The fins 50 may have a rectangular shape, or triangular or curved.

Particularly advantageously, the space between the fins 50 may be, during a step c), filled with a non-magnetic material and good thermal conductor such as copper or aluminum. Thus, according to this embodiment allows to achieve a thermal bridge to effectively cool the core 20.

In order to further increase the exchange surface of the core, additional fins 51 may be attached to the outer side surface 22 of the frame 21 other than the recessed surface.

The core 20 may comprise a gap of thickness less than 5% of the effective magnetic length I.

Advantageously, the air gap is disposed in the center of the bar 30. As mentioned above, the formation of the core 20 can be performed by injection molding of ferrite powder. In this respect, those skilled in the art will find the details of the powder injection molding method in the patent FR2970194 [3]. This technique comprises a first step of forming a masterbatch comprising an organic material (for example, polyolefins such as polyethylene, polypropylene), and inorganic powders (for example, for the intended application, oxides of the type ferrite, for example Mni-xZnxFe204 and Nii-xZnxFe204). The masterbatch is then injected into a mold to give it the desired shape. The molded part is then debinded (Anglo-Saxon terminology) at a temperature between 400 and 700 ° C (for example 500 ° C) to remove organic matter. The debinding step is then followed by a sintering step ("sintering" according to the Anglo-Saxon terminology), conducted at a temperature of between 900 and 1300 ° C. (for example 1220 ° C. for a ferrite oxide Mn). xZnxFe2C> 4) thus making it possible to increase the density of the piece thus formed. The core may be made in one piece, or may comprise an assembly of the several pieces (for example an assembly of two pieces in E, or a piece in E and an I-piece, or a U-shaped piece and a piece in I). Depending on the embodiment of the core, one or more molds may be required.

The filling of the space between the fins 50, during step c1), with a conductive material is carried out by an overmolding technique well known to those skilled in the art and described in the document Ruh et al. [4],

As represented in FIG. 7, the bar 30 may have a square section, and be traversed right through in a direction perpendicular to the plane of the frame 21 by cavities 41a and 41b near the two lateral faces 31 and 32 of the core , respectively. The cavities 41a and 41b are then filled (for example by overmoulding) with a conductive material (for example copper or aluminum) so as to constitute a part of the winding 40 intended to be embedded in the bar 30. The winding 40 is then completed, for example, by carrying metal plates 42 on each of the faces of the bar 30 parallel to the plane of the frame 21. The said plates 42 each connect a cavity 41a to a cavity 41b so as to form a continuous winding adapted to generate a magnetic induction in the bar 30.

Thus, the turns of the coil partially pass through the volume of the bar. As the coil is also the seat of energy dissipation (by Joule effect), the partial burying of the turns in the bar also makes it possible to better dissipate, via the fins 50 according to the invention, the heat emitted by the coil.

Thus, the heat dissipation means according to the invention can effectively dissipate the heat produced in an inductance circuit. The operating temperature of the inductance circuits is then reduced, and much more homogeneous in the core.

The implementation of the heat dissipation means according to the invention degrades only moderately, if at all, the bulk volume of the induction circuit. Indeed, said heat dissipation means, unlike the state of the art, are arranged in the core volume. In other words, contrary to the state of the art, the heat dissipation means require little or no addition of material.

More particularly, the heat dissipation means are arranged in areas of the core where the magnetic induction is low compared to the remainder of the core volume of an induction circuit in operation.

The dissipation means according to the invention also make it possible to envisage using the inductor circuits at higher frequencies, advantageously greater than 1 MHz.

REFERENCES

[1] US 6,920,039 B2.

[2] AM LEARY, "Soft Magnetic Materials in High-Frequency, High Power Conversion Applications," JOM, Volume 64, Issue 7, July 2012, Pages 772-781.

[3] FR2970194.

[4] Ruh et al., "The development of two-component microparticle injection by molding and sinter joining", Microsyst. Technol., 2011.17: 1547-1556 B

Claims

An inductance circuit comprising: a) a core (20) made of a one-piece magnetic material of volume bulk V, comprising a frame (21), and a bar (30) disposed at the center of the frame (21) so as to form two rectangular magnetic loops, symmetrical with respect to the bar (30), contiguous at a plane of symmetry of the bar (30), and of effective magnetic length I, the straight portions of the magnetic loops of the frame (21) have a surface cross-section A, and the bar (30) has a double surface cross-sectional area 2A of the surface A, b) a coil (40) comprising a number of N turns intended to generate a magnetic induction in the bar (30), c) fins (50) exposed to the external environment and intended to dissipate heat, the inductance circuit being characterized in that the fins (50) are included, at least in part, in at least one volume zone of the frame (21), disposed e in the extension of at least one end of the bar (30), the fins (50) are arranged in a bottom of at least one recess (25a, 25b) formed in the at least one volume zone of the frame (21). ), said at least one recess (25a, 25b) opening on an outer side surface (22) of said frame (21), and passing right through the frame (21) in a direction perpendicular to the plane of the frame (21).

2. Circuit inductor according to claim 1, wherein the at least one recess (25a, 25b) flares from its bottom to the outer lateral surface (22) of the frame (21).

3. Circuit inductor according to claim 2, wherein the at least one recess (25a, 25b) has a section, parallel to the plane of the frame (21), having constant dimensions in a direction perpendicular to the plane of said frame (21) said section is advantageously trapezoidal, more advantageously isosceles trapezoidal.

4. Circuit inductor according to one of claims 1 to 3, wherein the fins (50) are parallel to the plane defined by the frame (21).

5. Circuit inductor according to one of claims 1 to 4, wherein the surface developed by each fin is between 10 and 100% of the surface A.

6. Circuit inductor according to one of claims 1 to 5, wherein additional fins are reported on the outer side surface (22) of the frame (21).

7. Circuit inductor according to one of claims 1 to 6, wherein the bar (30) has a square cross section, and is traversed from one side in a direction perpendicular to the plane of the frame (21) by cavities, the cavities being filled by an electrical conductor so as to form a portion of the coil (40).

8. Circuit inductor according to one of claims 1 to 7, wherein the space between the fins (50) is filled with a metal material, preferably a metal material selected from: aluminum, copper.

9. Power converter comprising the inductance circuit (10) according to one of claims 1 to 8.

10. Method of manufacturing an inductance circuit according to one of claims 1 to 8 comprising the steps of: a) drawing a theoretical map of the magnetic flux lines in the core (20) of the inductance circuit (10) in operation said inductance circuit (10) having a predetermined inductance value L, the core (20) is made of a one-piece magnetic material of volume bulk V, the core comprising a frame (21), and a bar (30) arranged in the center of the frame (21) so as to form two rectangular magnetic loops, symmetrical with respect to the bar (30), contiguous at the plane of symmetry of the bar (30), and of effective magnetic length I the straight portions of the frame 21 have a surface cross section A, and the bar (30) has a double surface cross-sectional area 2A of the surface A ,. b) identifying, from the mapping previously prepared, the volume zones of said core (20) of the inductance circuit (10) in operation, for which the magnetic induction is less than 5% of the value of the induction magnetic medium in the core (20), c) manufacturing the core (20) considered in step a), fins (50) being included, at least in part, in at least a portion of the volume zones identified at 1 step b) and the fins (50) are also arranged in the extension of at least one end of the bar (30) and in a bottom of at least one recess (25a, 25b) formed in the at least one zone volume of the frame (21), said at least one recess (25a, 25b) opening on an outer lateral surface (22) of said frame (21), and passing right through the frame (21) in a direction perpendicular to the plane of the frame (21) d) forming a coil (40) of conductive material around a portion of the core (20).

11. The method of manufacture of claim 10, wherein additional fins are attached to the outer side surface (22) of the frame (21).

12. The manufacturing method according to claim 10 or 11, wherein following step c), a step of cl) filling with a metallic material of the space between the fins (50) is carried out.

13. Manufacturing method according to one of claims 10 to 12, wherein the step c) of manufacturing the core (20) is performed for injection molding powder.