EP3391393B1 - Inductance circuit including a passive thermal management function - Google Patents

Inductance circuit including a passive thermal management function Download PDF

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Publication number
EP3391393B1
EP3391393B1 EP16823214.8A EP16823214A EP3391393B1 EP 3391393 B1 EP3391393 B1 EP 3391393B1 EP 16823214 A EP16823214 A EP 16823214A EP 3391393 B1 EP3391393 B1 EP 3391393B1
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EP
European Patent Office
Prior art keywords
frame
core
inductance
fins
bar
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EP16823214.8A
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German (de)
French (fr)
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EP3391393A1 (en
Inventor
Gérard DELETTE
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Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
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Commissariat a lEnergie Atomique CEA
Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/08—Cooling; Ventilating
    • H01F27/22—Cooling by heat conduction through solid or powdered fillings
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/24—Magnetic cores

Definitions

  • the invention relates to an inductance circuit comprising a one-piece core incorporating a passive thermal management function.
  • the fins are attached to the outer side surface of the core 1.
  • 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 an electrical power source to supply an electrical system.
  • a power converter also comprises electronic components operating as switches (active component) switching at a given frequency f, and thus make it possible to supply the magnetic excitation coil 4.
  • the active components are transistors which are used to "cut" the input voltage according to regular cycles.
  • inductor circuits are used to store and destore electrical energy on each cycle and to smooth the output voltage to its average value.
  • the magnetic flux originates in the bar 3 along the axis of symmetry, and flows symmetrically, from one end of the bar 3, in 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.
  • the volume of an inductance circuit can be reduced by the use of magnetic cores comprising a material with high magnetic permeability, for example ⁇ r > 50.
  • magnetic materials having a high magnetic permeability mention may be made of oxides of the ferrite type, and more particularly the materials: Mn 1-x Zn x Fe 2 O 4 and Ni 1-x Zn x Fe 2 O 4 .
  • inductor circuits can also be reduced by increasing the operating frequency of inductor circuits.
  • active components may include transistors made out of Gallium Nitride (GaN). The latter make it possible to reach switching frequencies above 1 MHz.
  • GaN Gallium Nitride
  • the flow of the magnetic flux in the core 1 is accompanied by magnetic losses, which result in heating of the core.
  • This heating of the core can degrade the performance of the inductance circuit, and ultimately render it inoperative.
  • Heat dissipation means are then added to the inductance circuit in order to better manage the quantity of heat created during the operation of the inductance circuit.
  • the heat dissipation means as shown in figure 1 , generally take the form of fins 1a arranged 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 arranged do not modify the geometric factors of the core 1, and therefore leave the value of the magnetic induction of the inductance circuit unchanged.
  • these heat dissipation means are not satisfactory. Indeed, the volume occupied by the dissipation means is added to the volume of the inductor, and also increases its mass. Furthermore, to be effective, the fins 5 must have a large exchange surface, and therefore occupy a relatively large volume with respect to the core.
  • Inductance circuits then require dissipation means operating more efficiently than those known from the state of the art, in particular, in the fields of aeronautics and automobiles.
  • the management of heat dissipation must also be optimized for induction circuits involving the use of cores magnetic 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 therefore to propose an inductance circuit having more effective heat dissipation means, and while limiting the increase in volume and mass of said circuit.
  • the inductance circuit when it is 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.
  • 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.
  • the fins are thus located in the volume of the core participating 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 only very little to the magnetic characteristics of the inductance circuit.
  • the Applicant therefore proposes using at least one of these zones in the core to form fins. Thanks to these provisions, the Applicant obtains a remarkable level of cooling.
  • the Applicant has been able to observe that the presence of fins, according to the invention, makes it possible to increase the temperature of the core of the inductance circuit in operation from 250° C. to 110° C. Furthermore, the presence of fins has little or no effect on the inductance of the inductance circuit with respect to the nominal inductance.
  • the fins are formed directly in the volume of the core.
  • the fins can also be formed without adding additional material, and therefore without affecting the volumetric size of the core.
  • the arrangement of the fins, in a volume zone of the core and arranged in the extension of the bar makes it possible to create a heat exchange surface as close as possible to the hottest zone of the core.
  • the fins are arranged in a bottom of at least one recess made in the at least one volume zone of the frame, said at least one recess opening onto an outer lateral surface of said frame, and crossing on either side starts from the frame in a direction perpendicular to the plane of the frame.
  • the shape of the recess makes possible more effective ventilation of the fins, and consequently better cooling of the core.
  • the at least one recess widens from its bottom towards the outer side surface of the frame.
  • 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, even more advantageously trapezoidal isosceles.
  • 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%.
  • the at least one volume 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.
  • the fins are parallel to the plane defined by frame.
  • the surface developed by each fin is between 10 and 100% of the surface A.
  • the fins arranged in the at least one volume zone leave the volumetric size of the frame unchanged.
  • additional fins are attached to the outer side surface of the frame.
  • the bar has a square section, and is crossed 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 part of the reel.
  • the space between the fins is filled with a metallic material, advantageously a metallic material chosen from: aluminium, copper.
  • the invention also relates to a power converter comprising the inductance circuit
  • additional fins are attached to the outer side surface of the frame.
  • step c) a step of c1) of filling the space between the fins with a metallic material is carried out.
  • step c) of manufacturing the core is carried out for powder injection molding.
  • Effective magnetic length I (effective magnetic path length):
  • An example of an effective magnetic path is given at picture 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 by cross section is meant the section resulting from the intersection of a plane perpendicular to the longitudinal axis of an elongated element.
  • an inductance circuit 10 is an inductance circuit 10 with an inductance L M defined by the geometric characteristics of the core and the number of turns N.
  • inductance circuit 10 In the rest of the description, an example of inductance circuit 10 will be described.
  • the inductance circuit 10 according to the invention comprises a core 20.
  • the core 20, according to the invention, is made of a one-piece magnetic material, of volumetric size V, 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 a plane of symmetry of the bar 30, and of effective length I, the straight parts of the magnetic loops have a cross section of surface A.
  • the frame 21 defines a plane, which we will call frame plane in the remainder of the description.
  • the surface footprint of the frame 21 (or even 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 parts of the frame 21 is the same for each straight part, and is advantageously rectangular.
  • the cross section of the bar 30 can be square, rectangular or circular.
  • the core 20 comprises a magnetic material with a magnetic permeability greater than 50 ( ⁇ r >50).
  • the magnetic material may comprise a ferrite-type oxide of spinel crystallographic structure.
  • the magnetic permeability of such materials is stable in the high frequency range.
  • the most common magnetic materials respond to the formulation: Mn 1-x Zn x Fe 2 O 4 and Ni 1-x Zn x Fe 2 O 4 .
  • a core 20 comprising Mn 1-x Zn x Fe 2 O 4 , with x between 0.3 and 0.6, the magnetic permeability ⁇ r evolves with x, and is between 500 and 1000.
  • a preferred embodiment for the core 20, and which will be presented later in the presentation, comprises injection molding of NiZn or MnZn ferrite powder ("PIM” or “Powder Injection Molding” according to the Anglo-Saxon terminology). Saxon).
  • materials of the ferrite type also have high electrical resistivity values, which makes it possible to limit the losses by induced currents.
  • the Mn 1-x Zn x Fe 2 O 4 and Ni 1-x Zn x Fe 2 O 4 materials also have the advantage of being available on an industrial scale.
  • the core 20 comprises a frame 21 of thickness e.
  • the straight parts of the frame 21 have a surface cross-section A.
  • the frame 21 also comprises four outer side faces drawing an outer side surface 22.
  • the outer side surface 22 is perpendicular to the plane of the frame.
  • the frame 21 comprises four interior faces drawing an interior surface 23, also perpendicular to the plane of the frame.
  • volumetric bulk V of frame 21 by its volumetric footprint. More particularly, the volumetric size V of the frame 21 is then the product of the thickness e and the area S. The volumetric size V of the frame 21 is also equal to the volumetric size V' of the core 20.
  • the core 20 comprises the bar 30 of surface cross-section 2A (the surface cross-sectional area 2A of the bar is therefore, substantially twice the surface cross-sectional area A of the straight parts 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 along 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' on the figure 4 ).
  • the configuration thus described is a typical case of a core 20 used in an inductor circuit 10, and it is generally referred to as an E-E type configuration, possibly a two-part E-E type configuration.
  • Each half part includes a half frame and a half bar.
  • the half bar is shorter than the two side half parts of the half frame.
  • the bar 30, formed by the two half bars has an air gap (“air gap” according to Anglo-Saxon terminology).
  • the inductance circuit 10 comprises a magnetic excitation coil 40 comprising a number of N turns.
  • the magnetic excitation coil 40 when a current passes through it, is intended to create a magnetic induction in the bar 30.
  • the N turns of the coil 40 can be formed around the bar 30.
  • the magnetic excitation coil 40 is made of 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.
  • Core 20 includes heat dissipation means.
  • the heat dissipation means can take the form of fins 50 exposed to the external environment.
  • the fins 50 are made of the same magnetic material as the core 20.
  • the fins 50 increase the heat exchange surface of the core 10 with the external environment, and thus make it possible to cool it more efficiently when the inductance circuit 10 is in operation.
  • 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 can comprise a first volume zone 24a, and a second volume zone 24b
  • 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 can be arranged symmetrically along a plane passing through the center of the bar 30, and perpendicular to the longitudinal axis of said bar 30.
  • the fins 50 are arranged in the bottom of at least one recess made in the at least one volume zone of the frame 21, said at least one recess opening onto the outer side surface 22 of the 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 comprised, respectively, in the first volume zone 24a and the second volume zone 24b.
  • each recess 25a and 25b transverse right through the frame 21 in a direction perpendicular to the plane of said frame 21.
  • 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 then projects from the bottom of each recess 25a and 25b.
  • the arrangement of the fins 50 on the bottom of at least one recess makes it possible to increase the exchange surface and to position the latter as close as possible to the bar 30.
  • the Applicant has found that the greatest temperature increase occurs in the bar 30 when the inductance circuit 10 is in operation.
  • the figure 6.a represents the temperature distribution of a core 1 of an inductance circuit, known from the state of the art, in operation, and devoid of heat dissipation means.
  • the general characteristics of the kernel considered are given in Table 1.
  • Table 1. Material Ni 1-x Zn x Fe 2 O 4 Total width 46.5mm core thickness 10.8mm Total height 29mm Center bar diameter 10.8mm air gap 4.4mm Core volume 9.8cm3 Number of N turns 19 Power 800W Current in the coil 5A Switching frequency 3MHz
  • the core 1 includes a hot zone B (at the level of the bar 3) for which a temperature of 250°C is reached, while a temperature lower than 170°C is observed in the lateral zones C1 and C2 of kernel 1.
  • the configuration of the fins 50 according to the invention does not impose a significant increase in volume.
  • the fins 50 can be perpendicular to the plane of the bottom on which they rest.
  • the fins 50 can be entirely included in the volume defined by the at least one recess.
  • the addition of heat dissipation means does not cause an increase in the volume of the core 20.
  • the volumetric size of the core 20 is not affected.
  • the fins 50 can extend beyond the volume defined by the at least one recess.
  • the first recess 25a and the second recess 25b flare out from their respective bottoms towards the outer side face on which they open.
  • better ventilation is ensured at the level of 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 isosceles trapezoid.
  • the fins 50 can be parallel or perpendicular to the plane defined by frame 21.
  • the recess may have, in a non-limiting manner, a V-shaped, U-shaped section.
  • the recess may also have a section conforming with the section of the volume zone, for example the recess can match the shape of the volume zone.
  • fins 50 extending from the side surface 22 in a volume zone of the frame 21, said first zone being arranged 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 core.
  • the figure 6b represents a simulated map of the temperature of an inductor circuit equipped with heat dissipation means according to another mode of implementation of the invention (the fins 50 protrude from 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.
  • fins 50 in the core 20 is carried out in such a way as to optimize their efficiency in terms of heat dispersion, while only moderately affecting the inductance of the inductance circuit.
  • the fins 50 are arranged to only moderately modify the inductance of the inductance circuit 10.
  • the inductance L M of an inductance circuit 10 has a deviation from the nominal inductance L lower at 5%, even more preferably, the difference is less than 2%.
  • 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 map of the magnetic flux lines in the core is then calculated with precision, using for example a finite element calculation code, by considering the reference geometry determined in the first step. Numerical simulations in two or three dimensions by finite elements are well known to those skilled in the art and are not detailed in this description. The areas of 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 on the figure 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 finely identify the zones of the volume of the core in which the fins 50 can be made in the core, and while modifying only moderately the inductance of the inductance circuit 10 considered.
  • the fins 50 are parallel to the field lines likely to be created when the inductance circuit 10 is in operation.
  • the difference between the inductance of said circuit and the nominal inductance can be reduced.
  • the surface developed by each fin can be between 10 and 100% of the surface A, for example 30%.
  • the depth of the fins 50 can be between 10 and 50% of the square root of the surface A, for example 30%.
  • the width of the fins 50 can be between 0.1 and 2 mm, for example 1 mm.
  • the spacing of the fins 50 can be between 0.1 and 0.5 mm, for example 0.2 mm.
  • the fins 50 can have a rectangular shape, or triangular or curved.
  • the space between the fins 50 can be, during a step c1), filled with a non-magnetic material which is a good thermal conductor such as copper or aluminium.
  • additional fins 51 can be attached to the outer side surface 22 of the frame 21 other than the recessed surface.
  • the additional fins 51 are made of the same magnetic material as the core 20.
  • Core 20 may include an air gap with a thickness of less than 5% of the effective magnetic length I.
  • the air gap is arranged in the center of the bar 30.
  • the formation of the core 20 can be carried out by injection molding of ferrite powder.
  • 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 Mn 1-x Zn x Fe 2 O 4 and Ni 1 - x Zn x Fe 2 O 4 ).
  • the masterbatch is then injected into a mold to give it the desired shape.
  • the molded part is then debinded (“debinded” according to Anglo-Saxon terminology) at a temperature of between 400 and 700° C. (for example 500° C.) so as to eliminate the organic matter.
  • the debinding step is then followed by a sintering step (“sintering” according to Anglo-Saxon terminology), carried out at a temperature between 900 and 1300°C (for example 1220°C for a ferrite oxide Mn 1 -x Zn x Fe 2 O 4 ) thus making it possible to increase the density of the part thus formed.
  • the core may be made in a single piece, or may comprise an assembly of several pieces (for example an assembly of two E-pieces, or an E-piece and an I-piece, or even a U-piece and a I). Depending on the embodiment of the core, one or more molds may be required.
  • step c1) 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].
  • the bar 30 may have a square section, and be crossed right through in a direction perpendicular to the plane of the frame 21 by cavities 41a and 41b close to the two side 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) in order 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 transfer of metal plates 42 on each of the faces of the bar 30 parallel to the plane of the frame 21. Said plates 42 each connect a cavity 41a to a cavity 41b so as to form a continuous winding adapted to generate magnetic induction in bar 30.
  • the turns of the coil partially pass through the volume of the bar.
  • the coil also being the seat of energy dissipation (by Joule effect)
  • the partial burial 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.
  • the heat dissipation means according to the invention make it possible to 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, or even not at all, the bulkiness of the induction circuit. Indeed, said heat dissipation means, contrary to the state of the art, are arranged in the volume of the core. In other words, contrary to the state of the art, the heat dissipation means require little or no addition of material.
  • the heat dissipation means are arranged in areas of the core where the magnetic induction is low compared to the rest of the volume of the core of an induction circuit in operation.
  • the dissipation means according to the invention also make it possible to envisage using inductance circuits at higher frequencies, advantageously greater than 1 MHz.

Description

DOMAINE TECHNIQUE ET ART ANTÉRIEURTECHNICAL FIELD AND PRIOR ART

L'invention concerne un circuit à inductance comprenant un noyau monobloc intégrant une fonction de gestion thermique passive.The invention relates to an inductance circuit comprising a one-piece core incorporating a passive thermal management function.

La figure 1 représente un circuit à inductance connu de l'état de la technique et décrit dans le brevet US 7,920,039 B2 comprenant :

  1. a) un noyau 1 fait d'un matériau magnétique, monobloc, d'encombrement volumique V, comprenant un cadre 2, et une barre 3 disposée au centre du cadre 2 de manière à former deux boucles magnétiques rectangulaires, symétriques par rapport à la barre, contigus au niveau du plan de symétrie de la barre, et de longueur effective I, les parties droites des boucles magnétiques présentent une section transversale de surface A,
  2. b) une bobine 4 comprenant N spires autour de la barre 3,
  3. c) des ailettes 5 exposées à l'environnement extérieur et destinées à dissiper de la chaleur,
The figure 1 represents an inductance circuit known from the state of the art and described in the US patent 7,920,039 B2 including:
  1. a) a core 1 made of a one-piece magnetic material, of volumetric size V, comprising a frame 2, and a bar 3 arranged in the center of frame 2 so as to form two rectangular magnetic loops, symmetrical with respect to the bar , contiguous at the level of the plane of symmetry of the bar, and of effective length I, the straight parts of the magnetic loops have a cross-section of surface A,
  2. b) a coil 4 comprising N turns around bar 3,
  3. c) fins 5 exposed to the external environment and intended to dissipate heat,

Les ailettes sont rapportées sur la surface latérale extérieure du noyau 1.The fins are attached to the outer side surface of the core 1.

Un circuit à induction présente une inductance L déterminée par les grandeurs A, I et N, ainsi que par la perméabilité µr magnétique du noyau 1, et est donnée par la relation suivante : L = μ 0 μ r N 2 A l

Figure imgb0001
An induction circuit has an inductance L determined by the quantities A, I and N, as well as by the magnetic permeability µ r of core 1, and is given by the following relationship: I = μ 0 μ r NOT 2 AT I
Figure imgb0001

Autrement dit, la géométrie du noyau 1, et plus particulièrement le rapport des facteurs géométriques I et A, détermine la valeur de l'inductance du circuit à inductance.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.

Un tel circuit à induction est, par exemple, utilisé dans des convertisseurs de puissance dont la fonction est d'adapter la tension et le courant délivrés par une source de puissance électrique pour alimenter un système électrique.Such an induction circuit is, for example, used in power converters whose function is to adapt the voltage and the current delivered by an electrical power source to supply an electrical system.

Un convertisseur de puissance comprend également des composants électroniques fonctionnant comme des interrupteurs (composant actifs) commutant à une fréquence donnée f, et permettent ainsi d'alimenter la bobine 4 d'excitation magnétique.A power converter also comprises electronic components operating as switches (active component) switching at a given frequency f, and thus make it possible to supply the magnetic excitation coil 4.

Dans le cas des convertisseurs DC/DC par exemple, les composants actifs sont des transistors qui sont utilisés pour « découper » la tension d'entrée selon des cycles réguliers. Afin de délivrer une tension continue en sortie, des circuits à inductance sont utilisés pour stocker et déstocker l'énergie électrique sur chaque cycle et pour lisser la tension de sortie à sa valeur moyenne.In the case of DC/DC converters for example, the active components are transistors which are used to "cut" the input voltage according to regular cycles. In order to deliver a DC voltage at the output, inductor circuits are used to store and destore electrical energy on each cycle and to smooth the output voltage to its average value.

En fonctionnement, le courant électrique, délivré par les composants actifs, parcourt la bobine 4 d'excitation magnétique, et génère ainsi un flux magnétique, comprenant deux boucles symétriques fermées, dans le noyau 1.In operation, the electric current, delivered by the active components, travels through the magnetic excitation coil 4, and thus generates a magnetic flux, comprising two symmetrical closed loops, in the core 1.

Tel qu'illustré à la figure 2, le flux magnétique prend naissance dans la barre 3 selon l'axe de symétrie, et s'écoule de façon symétrique, d'une extrémité de la barre 3, dans le cadre 2 pour reboucler dans l'autre extrémité de la barre 3.As illustrated at figure 2 , the magnetic flux originates in the bar 3 along the axis of symmetry, and flows symmetrically, from one end of the bar 3, in the frame 2 to loop back into the other end of the bar 3.

Les circuits à inductance peuvent représenter jusqu'à 40 % du volume et du coût du convertisseur.Inductance circuits can represent up to 40% of the volume and cost of the converter.

Aussi, le volume d'un circuit à inductance peut être réduit par l'utilisation de noyaux magnétiques comprenant un matériau à forte perméabilité magnétique, par exemple µr > 50. Parmi les matériaux magnétiques présentant une perméabilité magnétique élevée, on peut citer les oxydes de type ferrite, et plus particulièrement les matériaux : Mn1-xZnxFe2O4 et Ni1-xZnxFe2O4.Also, the volume of an inductance circuit can be reduced by the use of magnetic cores comprising a material with high magnetic permeability, for example μ r > 50. Among the magnetic materials having a high magnetic permeability, mention may be made of oxides of the ferrite type, and more particularly the materials: Mn 1-x Zn x Fe 2 O 4 and Ni 1-x Zn x Fe 2 O 4 .

Le volume des circuits à inductance peut également être réduit en augmentant la fréquence de fonctionnement des circuits à inductance. Par exemple, les composants actifs peuvent comprendre des transistors faits sur du Nitrure de Gallium (GaN). Ces derniers permettent d'atteindre des fréquences de commutation supérieures à 1 MHz. A cet égard, l'homme du métier pourra consulter le document A. M. LEARY [2].The volume of inductor circuits can also be reduced by increasing the operating frequency of inductor circuits. For example, active components may include transistors made out of Gallium Nitride (GaN). The latter make it possible to reach switching frequencies above 1 MHz. In this regard, those skilled in the art may consult document AM LEARY [2].

L'écoulement du flux magnétique dans le noyau 1 s'accompagne de pertes magnétiques, qui se traduisent par un échauffement du noyau.The flow of the magnetic flux in the core 1 is accompanied by magnetic losses, which result in heating of the core.

Cet échauffement du noyau peut dégrader les performances du circuit à inductance, et à terme le rendre inopérant.This heating of the core can degrade the performance of the inductance circuit, and ultimately render it inoperative.

La diminution du volume du noyau, permise par l'utilisation de matériaux magnétiques constituant le noyau de perméabilité magnétique élevée et/ou par l'augmentation de la fréquence de fonctionnement du circuit à inductance, exacerbent cet échauffement.The reduction in the volume of the core, made possible by the use of magnetic materials constituting the core of high magnetic permeability and/or by the increase in the operating frequency of the inductance circuit, exacerbate this heating.

Des moyens de dissipation de chaleur sont alors ajoutés au circuit à inductance afin de mieux gérer la quantité de chaleur créée lors du fonctionnement du circuit à inductance.Heat dissipation means are then added to the inductance circuit in order to better manage the quantity of heat created during the operation of the inductance circuit.

Les moyens de dissipation de chaleur, tels que représentés à la figure 1, prennent généralement la forme d'ailettes la disposées à l'extérieur du noyau et rapportées sur la surface extérieur dudit noyau, de manière à augmenter la surface d'échange du noyau 1 avec l'air environnant.The heat dissipation means, as shown in figure 1 , generally take the form of fins 1a arranged 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.

Les ailettes 5 ainsi disposées ne modifient pas les facteurs géométriques du noyau 1, et laissent donc la valeur de l'induction magnétique du circuit à inductance inchangée. Cependant, ces moyens de dissipation de chaleur ne sont pas satisfaisants. En effet, le volume occupé par les moyens de dissipation vient s'ajouter au volume de l'inductance, et également augmenter sa masse. Par ailleurs, pour être efficaces, les ailettes 5 doivent présenter une surface d'échange importante, et donc, occuper un volume relativement important par rapport au noyau.The fins 5 thus arranged do not modify the geometric factors of the core 1, and therefore leave the value of the magnetic induction of the inductance circuit unchanged. However, these heat dissipation means are not satisfactory. Indeed, the volume occupied by the dissipation means is added to the volume of the inductor, and also increases its mass. Furthermore, to be effective, the fins 5 must have a large exchange surface, and therefore occupy a relatively large volume with respect to the core.

Or, pour certaines applications, il est souhaitable, voire primordial, que les circuits à inductance équipés de leurs moyens de dissipation de chaleur occupent le plus faible volume possible.However, for certain applications, it is desirable, even essential, that the inductance circuits equipped with their heat dissipation means occupy the smallest volume possible.

Les circuits à inductance requièrent alors des moyens de dissipation fonctionnant de manière plus efficace que ceux connus de l'état de la technique, notamment, dans les domaines de l'aéronautique et de l'automobile.Inductance circuits then require dissipation means operating more efficiently than those known from the state of the art, in particular, in the fields of aeronautics and automobiles.

Plus particulièrement, la gestion de la dissipation de la chaleur doit être également optimisée pour des circuits à induction impliquant l'utilisation de noyaux magnétiques 1 présentant une perméabilité magnétique supérieure à 50, et/ou des fonctionnements desdits circuits à des fréquences élevées, par exemple supérieures à 1 MHz.More particularly, the management of heat dissipation must also be optimized for induction circuits involving the use of cores magnetic 1 having a magnetic permeability greater than 50, and / or operations of said circuits at high frequencies, for example greater than 1 MHz.

Un but l'invention est alors de proposer un circuit à inductance présentant des moyens de dissipation de chaleur plus efficaces, et tout en limitant l'augmentation du volume et de la masse dudit circuit.An object of the invention is therefore to propose an inductance circuit having more effective heat dissipation means, and while limiting the increase in volume and mass of said circuit.

EXPOSÉ DE L'INVENTIONDISCLOSURE OF THE INVENTION

Le but de l'invention est alors atteint par un circuit à inductance comprenant :

  1. a) un noyau fait d'un matériau magnétique, monobloc, d'encombrement volumique V, comprenant un cadre, et une barre disposée au centre du cadre de manière à former deux boucles magnétiques rectangulaires, symétriques par rapport à la barre, contigus au niveau d'un plan de symétrie de la barre, et de longueur magnétique effective I, les parties droites du cadre présentent une section transversale de surface A, et la barre présente une section transversale 2A double de la section transversale A,
  2. b) une bobine comprenant un nombre de N spires destinées à générer une induction magnétique dans la barre,
  3. c) des ailettes exposées à l'environnement extérieur et destinées à dissiper de la chaleur, les ailettes étant faites du même matériau magnétique que le noyau,
les ailettes sont comprises, au moins en partie, dans au moins une zone volumique du cadre, disposée dans le prolongement d'au moins une extrémité de la barre.The object of the invention is then achieved by an inductance circuit comprising:
  1. a) a core made of a one-piece magnetic material, of volumetric size V, comprising 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 level of a plane of symmetry of the bar, and of effective magnetic length I, the straight parts of the frame have a surface cross-section A, and the bar has a cross-section 2A double the cross-section A,
  2. b) a coil comprising a number of N turns intended to generate a magnetic induction in the bar,
  3. c) fins exposed to the external environment and intended to dissipate heat, the fins being made of the same magnetic material as the core,
the fins are included, at least in part, in at least one volume zone of the frame, arranged in the extension of at least one end of the bar.

Le circuit à inductance, lorsqu'il est dépourvu d'ailettes dans la au moins une zone volumique du cadre, a une inductance égale à l'inductance nominale L définie par les grandeurs A, I et N.The inductance circuit, when it is 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.

Par ailleurs, pour un circuit à induction dépourvue d'ailettes, et en fonctionnement, l'au moins une zone volumique est également parcourue par des lignes d'induction magnétique.Moreover, for an induction circuit devoid of fins, and in operation, the at least one volume zone is also traversed by magnetic induction lines.

La section transversale dans les parties droites du cadre est la même pour chaque partie droite, et est rectangulaire.The cross section in the straight parts of the frame is the same for each straight part, and is rectangular.

Contrairement à l'état de la technique, les ailettes se trouvent ainsi dans le volume du noyau participant à la circulation des lignes d'induction magnétique.Contrary to the state of the art, the fins are thus located in the volume of the core participating in the circulation of the magnetic induction lines.

La Demanderesse a constaté qu'il existe des zones pour lesquelles l'induction magnétique locale est très faible, et ne contribuent que très peu aux caractéristiques magnétiques du circuit à inductance. La Demanderesse propose donc d'utiliser au moins une de ces zones dans le noyau pour former des ailettes. Grâce à ces dispositions, la Demanderesse obtient un niveau de refroidissement remarquable. Par exemple, le Demanderesse a pu observer que la présence d'ailettes, selon l'invention, permet de faire passer la température du noyau du circuit à inductance en fonctionnement de 250°C à 110°C. Par ailleurs, la présence d'ailettes affecte peu ou pas l'inductance du circuit à inductance par rapport à l'inductance nominale.The Applicant has found that there are areas for which the local magnetic induction is very low, and contribute only very little to the magnetic characteristics of the inductance circuit. The Applicant therefore proposes using at least one of these zones 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 increase the temperature of the core of the inductance circuit in operation from 250° C. to 110° C. Furthermore, the presence of fins has little or no effect on the inductance of the inductance circuit with respect to the nominal inductance.

Ainsi, les ailettes sont formées directement dans le volume du noyau. Les ailettes peuvent également être formées sans apport de matière supplémentaire, et par conséquent, sans affecter l'encombrement volumique du noyau.Thus, the fins are formed directly in the volume of the core. The fins can also be formed without adding additional material, and therefore without affecting the volumetric size of the core.

Par ailleurs, la disposition des ailettes, dans une zone volumique du noyau et disposée dans le prolongement de la barre, permet de créer une surface d'échange de chaleur au plus proche de la zone du noyau la plus chaude.Furthermore, the arrangement of the fins, in a volume zone of the core and arranged in the extension of the bar, makes it possible to create a heat exchange surface as close as possible to the hottest zone of the core.

De plus, le fonctionnement d'un circuit à inductance à des fréquences supérieures à 1 MHz n'est plus un frein. En effet, l'augmentation de la de température due à la montée en fréquence est parfaitement gérée par les ailettes selon l'invention.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.

Selon un mode de mise en œuvre, les ailettes sont disposées dans un fond d'au moins un évidement pratiqué dans la au moins une zone volumique du cadre, ledit au moins un évidement débouchant sur une surface latérale extérieure dudit cadre, et traversant de part en part le cadre selon une direction perpendiculaire au plan du cadre.According to one mode of implementation, the fins are arranged in a bottom of at least one recess made in the at least one volume zone of the frame, said at least one recess opening onto an outer lateral surface of said frame, and crossing on either side starts from the frame in a direction perpendicular to the plane of the frame.

Ainsi, la forme de l'évidement rend possible une ventilation plus efficace des ailettes, et par conséquent un meilleur refroidissement du noyau.Thus, the shape of the recess makes possible more effective ventilation of the fins, and consequently better cooling of the core.

Selon un mode de mise en œuvre, le au moins un évidement s'évase de son fond vers la surface latérale extérieure du cadre.According to one mode of implementation, the at least one recess widens from its bottom towards the outer side surface of the frame.

Selon un mode de mise en œuvre, le au moins un évidement a une section, parallèle au plan du cadre, présentant des dimensions constantes selon une direction perpendiculaire au plan dudit cadre, ladite section est avantageusement trapézoïdale, encore plus avantageusement trapézoïdale isocèle.According to one mode of implementation, 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, even more advantageously trapezoidal isosceles.

Selon un mode de mise en œuvre, les ailettes sont agencées de sorte que l'écart relatif entre l'inductance du circuit à inductance avec l'inductance nominale L est inférieur à 5%, de préférence inférieur à 2%.According to one mode of implementation, 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%.

Selon un mode de mise en œuvre, la au moins une zone volumique est une zone pour laquelle, lorsque le circuit à inductance est en fonctionnement, l'induction magnétique locale est inférieure à 5 % de la valeur de l'induction magnétique moyenne dans le noyau.According to one mode of implementation, the at least one volume 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.

Selon un mode de mise en œuvre, les ailettes sont parallèles au plan défini par cadre.According to one mode of implementation, the fins are parallel to the plane defined by frame.

Selon un mode de mise en œuvre, la surface développée par chaque ailette est comprise entre 10 et 100 % de la surface A.According to one mode of implementation, the surface developed by each fin is between 10 and 100% of the surface A.

Selon un mode de mise en œuvre, les ailettes disposées dans la au moins une zone volumique laissent l'encombrement volumique du cadre inchangé.According to one mode of implementation, the fins arranged in the at least one volume zone leave the volumetric size of the frame unchanged.

Selon un mode de mise en œuvre, des ailettes additionnelles sont rapportées sur la surface latérale extérieure du cadre.According to one mode of implementation, additional fins are attached to the outer side surface of the frame.

Selon un mode de mise en œuvre, la barre présente une section carrée, et est traversée de part en part selon une direction perpendiculaire au plan du cadre par des cavités, les cavités étant remplies par un conducteur électrique de manière à former une partie de la bobine.According to one mode of implementation, the bar has a square section, and is crossed 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 part of the reel.

Selon un mode de mise en œuvre, l'espace entre les ailettes est comblé par un matériau métallique, avantageusement un matériau métallique choisi parmi : aluminium, cuivre.According to one mode of implementation, the space between the fins is filled with a metallic material, advantageously a metallic material chosen from: aluminium, copper.

L'invention concerne également un convertisseur de puissance comprenant le circuit à inductanceThe invention also relates to a power converter comprising the inductance circuit

L'invention concerne également une méthode de fabrication d'un circuit à inductance comprenant les étapes :

  1. a) dresser une cartographie théorique des lignes de flux magnétiques dans le noyau du circuit à inductance en fonctionnement, ledit circuit à inductance présentant une valeur d'inductance prédéterminée L, le noyau est fait d'un matériau magnétique, monobloc, d'encombrement volumique V, le noyau comprenant un cadre, et une barre disposée au centre du cadre de manière à former deux boucles magnétiques rectangulaires, symétriques par rapport à la barre, contigus au niveau du plan de symétrie de la barre, et de longueur magnétique effective I, les parties droites du cadre présentent une section transversale de surface A, et la barre présente une section transversale 2A double de la section transversale A,
  2. b) identifier, à partir de la cartographie précédemment dressée, les zones de volume dudit noyau, du circuit à inductance en fonctionnement, pour lesquelles l'induction magnétique est inférieure à 5 % de la valeur de l'induction magnétique moyenne dans le noyau,
  3. c) fabriquer le noyau considéré à l'étape a), des ailettes étant comprises, au moins en partie, dans au moins une partie des zones de volumes identifiées à l'étape b) et les ailettes sont également disposées dans le prolongement d'au moins une extrémité de la barre, les ailettes étant faites du même matériau magnétique que le noyau,
  4. d) former une bobine d'un matériau conducteur autour d'une partie du noyau.
The invention also relates to a method of manufacturing an inductance circuit comprising the steps:
  1. a) draw up a theoretical map of the magnetic flux lines in the core of the inductor circuit in operation, said inductor circuit having a predetermined inductance value L, the core is made of a magnetic material, in one piece, of volumetric size V, the core comprising 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 level of the plane of symmetry of the bar, and of effective magnetic length I, the straight parts of the frame have a surface cross-section A, and the bar has a cross-section 2A double the cross-section A,
  2. b) identify, from the map previously drawn up, the areas of volume of said core, of the inductance circuit in operation, for which the magnetic induction is less than 5% of the value of the average magnetic induction in the core,
  3. c) manufacturing the core considered in step a), fins being included, at least in part, in at least part of the volume zones identified in step b) and the fins are also arranged in the extension of at least one end of the bar, the fins being made of the same magnetic material as the core,
  4. d) forming a coil of conductive material around part of the core.

Selon un mode de mise en œuvre, des ailettes additionnelles sont rapportées sur la surface latérale extérieure du cadre.According to one mode of implementation, additional fins are attached to the outer side surface of the frame.

Selon un mode de mise en œuvre, à la suite de l'étape c), une étape de c1) de comblement par un matériau métallique de l'espace entre les ailettes est réalisée.According to one mode of implementation, following step c), a step of c1) of filling the space between the fins with a metallic material is carried out.

Selon un mode de mis en œuvre, l'étape c) de fabrication du noyau est exécutée pour moulage par injection de poudre.According to one mode of implementation, step c) of manufacturing the core is carried out for powder injection molding.

BRÈVE DESCRIPTION DES DESSINSBRIEF DESCRIPTION OF DRAWINGS

D'autres caractéristiques et avantages apparaîtrons dans la description qui va suivre des modes de mise en œuvre circuit à inductance selon l'invention, donnés à titre d'exemples non limitatifs, en référence aux dessins annexés dans lesquels :

  • La figure 1 est une vue de dessus d'une représentation schématique d'un circuit à inductance connu de l'art antérieur.
  • La figure 2 est une représentation schématique du parcours du flux magnétique dans un circuit à inductance connu de l'art antérieur.
  • La figure 3 est une vue de dessus d'une représentation schématique du chemin magnétique effectif dans un noyau magnétique, compris dans un circuit à inductance connu de l'état de l'art.
  • La figure 4 est une vue de dessus d'une représentation schématique d'un circuit à inductance selon un exemple de réalisation de l'invention.
  • La figure 5 est une cartographie des lignes d'induction magnétique dans le noyau d'un circuit à inductance connu de l'art antérieur.
  • La figure 6.a est une simulation de la distribution en température dans un noyau dépourvu de moyens de dissipation de chaleur connu de l'art antérieur.
  • La figure 6.b est une simulation de la distribution en température dans un noyau selon un exemple de réalisation de l'invention.
  • La figure 7 est une vue de dessus d'une représentation schématique d'un circuit à inductance selon un exemple de réalisation de l'invention.
Other characteristics and advantages will appear in the following description of the inductance circuit implementation modes according to the invention, given by way of non-limiting examples, with reference to the appended drawings in which:
  • The figure 1 is a top view of a schematic representation of an inductor circuit known from the prior art.
  • The figure 2 is a schematic representation of the path of the magnetic flux in an inductance circuit known from the prior art.
  • The picture 3 is a top view of a schematic representation of the effective magnetic path in a magnetic core, included in a known state-of-the-art inductance circuit.
  • The figure 4 is a top view of a schematic representation of an inductance circuit according to an exemplary embodiment of the invention.
  • The figure 5 is a map of the magnetic induction lines in the core of an inductance circuit known from the prior art.
  • The figure 6.a is a simulation of the temperature distribution in a core devoid of heat dissipation means known from the prior art.
  • The figure 6.b is a simulation of the temperature distribution in a core according to an embodiment of the invention.
  • The figure 7 is a top view of a schematic representation of an inductance circuit according to an exemplary embodiment of the invention.

EXPOSÉ DÉTAILLÉ DE MODES DE RÉALISATION PARTICULIERSDETAILED DISCUSSION OF PARTICULAR EMBODIMENTS

Pour les différents modes de mise en œuvre, les mêmes références seront utilisées pour des éléments identiques ou assurant la même fonction, par souci de simplification de la description.For the different modes of implementation, the same references will be used for identical elements or providing the same function, for the sake of simplifying the description.

Définitions : Definitions :

Longueur magnétique effective I (longueur de chemin magnétique effective): La longueur magnétique effective (Leff) est définie comme la longueur du contour fermé pris dans le noyau magnétique sur lequel la circulation du champ magnétique moyen (Hmoy) est égale à la somme des courants (nb de spires N multiplié par le courant nominal I) traversant le circuit (théorème d'Ampère). En d'autres termes : Hmoy.Leff = N∗I. Un exemple de chemin magnétique effectif est donné à la figure 3. Dans cet exemple, le noyau forme une boucle rectangulaire, et le chemin magnétique effectif associé à cette configuration est représenté en trait interrompus. Effective magnetic length I (effective magnetic path length): The effective magnetic length (L eff ) is defined as the length of the closed contour taken in the magnetic core on which the circulation of the mean magnetic field (H moy ) is equal to the sum of the currents (number of turns N multiplied by the nominal current I) crossing the circuit (Ampère's theorem). In other words: H avg .L eff = N ∗ I. An example of an effective magnetic path is given at picture 3 . In this example, the core forms a rectangular loop, and the effective magnetic path associated with this configuration is shown in broken lines.

Section transversale : on entend par section transversale, la coupe résultant de l'intersection d'un plan perpendiculaire à l'axe longitudinal d'un élément de forme allongée. Cross section : by cross section is meant the section resulting from the intersection of a plane perpendicular to the longitudinal axis of an elongated element.

Inductance nominale L : valeur de l'inductance L définie par la longueur magnétique effective I, la surface A, et le nombre de spires N, et selon la relation : L = μ 0 μ r N 2 A l

Figure imgb0002
Nominal inductance L : value of the inductance L defined by the effective magnetic length I, the area A, and the number of turns N, and according to the relationship: I = μ 0 μ r NOT 2 AT I
Figure imgb0002

Sur la figure 4, on peut voir un exemple de réalisation d'un circuit à inductance 10 selon la présente invention. Il s'agit d'un circuit à inductance 10 d'inductance LM définie par les caractéristiques géométriques du noyau et du nombre de spires N.On the figure 4 , one can see an embodiment of an inductance circuit 10 according to the present invention. It is an inductance circuit 10 with an inductance L M defined by the geometric characteristics of the core and the number of turns N.

Dans la suite de la description, un exemple de circuit à inductance 10 sera décrit.In the rest of the description, an example of inductance circuit 10 will be described.

La circuit à inductance 10 selon l'invention comprend un noyau 20.The inductance circuit 10 according to the invention comprises a core 20.

Le noyau 20, selon l'invention, est fait d'un matériau magnétique, monobloc, d'encombrement volumique V, 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 effective I, les parties droites des boucles magnétiques présentent une section transversale de surface A.The core 20, according to the invention, is made of a one-piece magnetic material, of volumetric size V, 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 a plane of symmetry of the bar 30, and of effective length I, the straight parts of the magnetic loops have a cross section of surface A.

Le cadre 21 définit un plan, que nous appellerons plan du cadre dans la suite de la description. L'empreinte surfacique du cadre 21 (ou encore l'intersection du cadre avec un plan parallèle au plan du cadre) est un rectangle présentant une surface S.The frame 21 defines a plane, which we will call frame plane in the remainder of the description. The surface footprint of the frame 21 (or even the intersection of the frame with a plane parallel to the plane of the frame) is a rectangle having a surface S.

La section transversale dans les parties droites du cadre 21 est la même pour chaque partie droite, et est, avantageusement, rectangulaire.The cross section in the straight parts of the frame 21 is the same for each straight part, and is advantageously rectangular.

La section transversale de la barre 30 peut être carrée, rectangulaire ou circulaire.The cross section of the bar 30 can be square, rectangular or circular.

De manière avantageuse, le noyau 20 comprend un matériau magnétique de perméabilité magnétique supérieure à 50 (µr > 50).Advantageously, the core 20 comprises a magnetic material with a magnetic permeability greater than 50 (μ r >50).

Par exemple, le matériau magnétique peut comprendre un oxyde de type ferrite de structure cristallographie spinelle. En effet, la perméabilité magnétique de tels matériaux est stable dans la gamme des hautes fréquences. Les matériaux magnétiques les plus courants répondent à la formulation :

        Mn1-xZnxFe2O4 et Ni1-xZnxFe2O4.

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

Mn 1-x Zn x Fe 2 O 4 and Ni 1-x Zn x Fe 2 O 4 .

Par exemple, un noyau 20 comprenant du Mn1-xZnxFe2O4, avec x compris entre 0,3 et 0,6, la perméabilité magnétique µr évolue avec x, et est comprise entre 500 et 1000.For example, a core 20 comprising Mn 1-x Zn x Fe 2 O 4 , with x between 0.3 and 0.6, the magnetic permeability µ r evolves with x, and is between 500 and 1000.

Un mode de réalisation préférentiel pour le noyau 20, et qui sera présenté dans la suite de l'exposé, comprend le moulage par injection de poudre de ferrite NiZn ou de MnZn (« PIM » ou « Powder Injection Molding » selon la terminologie Anglo-Saxonne).A preferred embodiment for the core 20, and which will be presented later in the presentation, comprises injection molding of NiZn or MnZn ferrite powder ("PIM" or "Powder Injection Molding" according to the Anglo-Saxon terminology). Saxon).

De manière avantageuse, les matériaux de type ferrite présentent également des valeurs de résistivités électriques élevées, ce qui permet de limiter les pertes par courants induits.Advantageously, materials of the ferrite type also have high electrical resistivity values, which makes it possible to limit the losses by induced currents.

Les matériaux Mn1-xZnxFe2O4 et Ni1-xZnxFe2O4 présentent également l'avantage d'être disponibles à l'échelle industrielle.The Mn 1-x Zn x Fe 2 O 4 and Ni 1-x Zn x Fe 2 O 4 materials also have the advantage of being available on an industrial scale.

Le noyau 20 comprend un cadre 21 d'épaisseur e. Les parties droites du cadre 21 présentent une section transversale de surface A.The core 20 comprises a frame 21 of thickness e. The straight parts of the frame 21 have a surface cross-section A.

Le cadre 21 comprend également quatre faces latérales extérieures dessinant une surface latérale extérieure 22. La surface latérale extérieure 22 est perpendiculaire au plan du cadre.The frame 21 also comprises four outer side faces drawing an outer side surface 22. The outer side surface 22 is perpendicular to the plane of the frame.

Le cadre 21 comprend quatre faces intérieures dessinant une surface intérieure 23, également perpendiculaire au plan du cadre.The frame 21 comprises four interior faces drawing an interior surface 23, also perpendicular to the plane of the frame.

Nous définissons l'encombrement volumique V du cadre 21 par son empreinte volumique. Plus particulièrement, l'encombrement volumique V du cadre 21 est alors le produit de l'épaisseur e et de l'aire S. L'encombrement volumique V du cadre 21 est également égal à l'encombrement volumique V' du noyau 20.We define the volumetric bulk V of frame 21 by its volumetric footprint. More particularly, the volumetric size V of the frame 21 is then the product of the thickness e and the area S. The volumetric size V of the frame 21 is also equal to the volumetric size V' of the core 20.

Le noyau 20 comprend la barre 30 de section transversale de surface 2A (l'aire de la section transversale de surface 2A de la barre est donc, sensiblement, le double de l'aire de la section transversale de surface A des parties droites du cadre) et relie deux faces opposées de la surface intérieure 23 du cadre 21, de manière à former deux boucles magnétiques symétriques de longueur magnétique effective I, et contigus selon un plan de symétrie de la barre 30.The core 20 comprises the bar 30 of surface cross-section 2A (the surface cross-sectional area 2A of the bar is therefore, substantially twice the surface cross-sectional area A of the straight parts 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 along a plane of symmetry of the bar 30.

La barre 30 comprend un axe de symétrie s'étendant selon sa longueur (représenté par l'axe XX' sur la figure 4).The bar 30 comprises an axis of symmetry extending along its length (represented by the axis XX' on the figure 4 ).

La configuration ainsi décrite est un cas typique de noyau 20 utilisé dans un circuit à inductance 10, et on parle généralement de configuration de type E-E, éventuellement de configuration de type E-E en deux parties.The configuration thus described is a typical case of a core 20 used in an inductor circuit 10, and it is generally referred to as an E-E type configuration, possibly a two-part E-E type configuration.

Une telle configuration est généralement obtenue par l'assemblage de deux demies parties. Chaque demie partie comprend un demi cadre et une demie barre.Such a configuration is generally obtained by assembling two half parts. Each half part includes a half frame and a half bar.

Eventuellement la demie barre est plus courte que les deux demies parties latérales du demi cadre. Ainsi, la barre 30, formée par les deux demies barres, présente un entrefer (« air gap » selon la terminologie Anglo-Saxonne).Optionally, the half bar is shorter than the two side half parts of the half frame. Thus, the bar 30, formed by the two half bars, has an air gap (“air gap” according to Anglo-Saxon terminology).

Le circuit à inductance 10 comprend une bobine 40, d'excitation magnétique, comprenant un nombre de N spires. La bobine 40, d'excitation magnétique, lorsqu'elle est traversée par un courant, est destinée à créer une induction magnétique dans la barre 30. Les N spires de la bobine 40 peuvent être formées autour de la barre 30.The inductance circuit 10 comprises a magnetic excitation coil 40 comprising a number of N turns. The magnetic excitation coil 40, when a current passes through it, is intended to create a magnetic induction in the bar 30. The N turns of the coil 40 can be formed around the bar 30.

La bobine 40 d'excitation magnétique est en métal, par exemple en cuivre. La bobine 40 d'excitation magnétique comprend un fil continu enroulé autour de la barre 30, de manière à former les N spires.The magnetic excitation coil 40 is made of 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.

Le noyau 20 comprend des moyens de dissipation de chaleur.Core 20 includes heat dissipation means.

Les moyens de dissipation de chaleur peuvent prendre la forme d'ailettes 50 exposées à l'environnement extérieur.The heat dissipation means can take the form of fins 50 exposed to the external environment.

De manière particulièrement avantageuse, les ailettes 50 sont faites du même matériau magnétique que le noyau 20.Particularly advantageously, the fins 50 are made of the same magnetic material as the core 20.

Les ailettes 50 augmentent la surface d'échange thermique du noyau 10 avec l'environnement extérieur, et rendent ainsi possible son refroidissement plus efficace lorsque le circuit à inductance 10 est en fonctionnement.The fins 50 increase the heat exchange surface of the core 10 with the external environment, and thus make it possible to cool it more efficiently when the inductance circuit 10 is in operation.

Selon l'invention, les ailettes 50 sont comprises, au moins en partie, dans au moins une zone volumique du cadre 21, disposée dans le prolongement d'au moins une extrémité de la barre 30.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.

La au moins une zone volumique peut comprendre une première zone volumique 24a, et une deuxième zone volumique 24bThe at least one volume zone can comprise a first volume zone 24a, and a second volume zone 24b

Par exemple, le noyau est pourvu de deux jeux d'ailettes 50, compris, respectivement, au moins partiellement, dans la première zone volumique 24a, et la deuxième zone volumique 24b du cadre 21.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.

La première zone volumique 24a et la deuxième zone volumique 24b peuvent être disposées de manière symétrique selon un plan passant par le centre de la barre 30, et perpendiculaire à l'axe longitudinal de ladite barre 30.The first volume zone 24a and the second volume zone 24b can be arranged symmetrically along a plane passing through the center of the bar 30, and perpendicular to the longitudinal axis of said bar 30.

De manière avantageuse, les ailettes 50 sont disposées dans le fond d'au moins un évidement pratiqué dans la au moins une zone volumique du cadre 21, ledit au moins un évidement débouchant sur la surface latérale extérieure 22 dudit cadre 21.Advantageously, the fins 50 are arranged in the bottom of at least one recess made in the at least one volume zone of the frame 21, said at least one recess opening onto the outer side surface 22 of the said frame 21.

Le au moins un évidement peut comprendre un premier évidement 25a et un deuxième évidement 25b.The at least one recess may comprise a first recess 25a and a second recess 25b.

Le premier évidement 25a et le deuxième évidement 25b sont compris, respectivement, dans la première zone volumique 24a et la deuxième zone volumique 24b.The first recess 25a and the second recess 25b are comprised, respectively, in the first volume zone 24a and the second volume zone 24b.

De manière avantageuse, chaque évidement 25a et 25b transverse de part en part le cadre 21 selon une direction perpendiculaire au plan dudit cadre 21.Advantageously, each recess 25a and 25b transverse right through the frame 21 in a direction perpendicular to the plane of said frame 21.

Dans l'exemple présenté à la figure 4, chaque évidement 25a et 25b peut comprendre un fond plat parallèle à la face latérale extérieure du cadre 21 sur laquelle il débouche.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.

Un jeu d'ailettes 50 est alors en saillie par rapport au fond de chaque évidement 25a et 25b.A set of fins 50 then projects from the bottom of each recess 25a and 25b.

Ainsi, la disposition des ailettes 50 sur le fond d'au moins un évidement permet d'augmenter la surface d'échange et de positionner cette dernière au plus proche de la barre 30.Thus, the arrangement of the fins 50 on the bottom of at least one recess makes it possible to increase the exchange surface and to position the latter as close as possible to the bar 30.

En effet, la Demanderesse a constaté que la plus forte augmentation de température se produit dans la barre 30 lorsque le circuit à inductance 10 est en fonctionnement. Par exemple la figure 6.a représente la distribution en température d'un noyau 1 d'un circuit à inductance, connu de l'état de l'art, en fonctionnement, et dépourvu de moyens de dissipation de chaleur. Les caractéristiques générales du noyau considéré sont données dans le tableau 1. Tableau 1. Matériau Ni1-xZnxFe2O4 Largeur totale 46.5 mm Epaisseur du noyau 10.8 mm Hauteur totale 29 mm Diamètre barre central 10.8 mm Entrefer 4.4 mm Volume du noyau 9.8 cm3 Nombre de N spires 19 Puissance 800 W Courant dans la bobine 5 A Fréquence de commutation 3 MHz Indeed, the Applicant has found that the greatest temperature increase occurs in the bar 30 when the inductance circuit 10 is in operation. For example the figure 6.a represents the temperature distribution of a core 1 of an inductance circuit, known from the state of the art, in operation, and devoid of heat dissipation means. The general characteristics of the kernel considered are given in Table 1. Table 1. Material Ni 1-x Zn x Fe 2 O 4 Total width 46.5mm core thickness 10.8mm Total height 29mm Center bar diameter 10.8mm air gap 4.4mm Core volume 9.8cm3 Number of N turns 19 Power 800W Current in the coil 5A Switching frequency 3MHz

On peut alors constater le noyau 1 comprend une zone chaude B (au niveau de la barre 3) pour laquelle une température de 250°C est atteinte, tandis qu'une température inférieure à 170°C est observée dans les zones latérales C1 et C2 du noyau 1.We can then see the core 1 includes a hot zone B (at the level of the bar 3) for which a temperature of 250°C is reached, while a temperature lower than 170°C is observed in the lateral zones C1 and C2 of kernel 1.

Par ailleurs, contrairement aux solutions proposées par l'art antérieur et plus particulièrement US 6,920,039 B2 , la configuration des ailettes 50 selon l'invention n'impose pas une augmentation de volume importante.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.

De manière avantageuse, les ailettes 50 peuvent être perpendiculaires au plan du fond sur lequel elles reposent.Advantageously, the fins 50 can be perpendicular to the plane of the bottom on which they rest.

Toujours de manière avantageuse, les ailettes 50 peuvent être entièrement comprises dans le volume défini par le au moins un évidement. Dans l'exemple de la figure 4, l'ajout de moyen de dissipation de chaleur n'engendre pas d'augmentation de volume du noyau 20.Still advantageously, the fins 50 can be entirely included in the volume defined by the at least one recess. In the example of the figure 4 , the addition of heat dissipation means does not cause an increase in the volume of the core 20.

Ainsi, l'encombrement volumique du noyau 20 n'est pas affecté.Thus, the volumetric size of the core 20 is not affected.

De manière alternative, les ailettes 50 peuvent s'étendre au-delà du volume défini par le au moins un évidement.Alternatively, the fins 50 can extend beyond the volume defined by the at least one recess.

Ainsi, des ailettes plus longues augmentent la surface d'échange du noyau 20 avec l'environnement extérieur, rendant ainsi le refroidissement de dispositif à induction 10 plus efficace lorsque ce dernier est en fonctionnement.Thus, longer fins increase the exchange surface of the core 20 with the external environment, thus making the cooling of the induction device 10 more efficient when the latter is in operation.

Selon un exemple de réalisation particulièrement avantageux, le premier évidement 25a et le deuxième évidement 25b s'évasent de leur fond respectif vers la face latérale extérieure sur laquelle ils débouchent. Ainsi, tel qu'illustré sur la figure 6b, une meilleure ventilation est assurée au niveau des ailettes 50. Chaque évidement 25a et 25b a une section, parallèle au plan du cadre 21, présentant des dimensions constantes selon une direction perpendiculaire au plan dudit cadre 21. Ladite section peut être trapézoïdale, plus particulièrement trapézoïdale isocèle.According to a particularly advantageous exemplary embodiment, the first recess 25a and the second recess 25b flare out from their respective bottoms towards the outer side face on which they open. Thus, as illustrated in the figure 6b , better ventilation is ensured at the level of 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 isosceles trapezoid.

Les ailettes 50 peuvent être parallèles ou perpendiculaires au plan défini par cadre 21.The fins 50 can be parallel or perpendicular to the plane defined by frame 21.

En variante, l'évidement peut présenter, de manière non limitative une section en V, en U. L'évidement peut également avoir une section conforme avec la section de la zone volumique, par exemple l'évidement peut épouser la forme de la zone volumique.As a variant, the recess may have, in a non-limiting manner, a V-shaped, U-shaped section. The recess may also have a section conforming with the section of the volume zone, for example the recess can match the shape of the volume zone.

Ainsi, des ailettes 50, s'étendant de la surface latérale 22 dans une zone volumique du cadre 21, ladite première zone étant disposée dans le prolongement de la barre 30, permettent de créer une surface d'échange de chaleur au plus proche de la zone chaude du noyau.Thus, fins 50, extending from the side surface 22 in a volume zone of the frame 21, said first zone being arranged 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 core.

Selon un deuxième exemple, la figure 6b représente une cartographie simulée de la température d'un circuit à inductance équipé de moyens de dissipation de chaleur selon un autre mode de mise en œuvre de l'invention (les ailettes 50 dépassent du volume V du noyau). Un température de 110°C est alors observée aussi bien dans la barre (zones C1 et C2) que dans le cadre (zone B). La température est non seulement beaucoup plus basse, mais également plus homogène dans le noyau.According to a second example, the figure 6b represents a simulated map of the temperature of an inductor circuit equipped with heat dissipation means according to another mode of implementation of the invention (the fins 50 protrude from 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.

Ainsi, la formation d'ailettes 50 dans le noyau 20, selon l'invention, est réalisée de manière à optimiser leur efficacité en terme de dispersion de chaleur, tout en n'affectant que modérément l'inductance de circuit à inductance.Thus, the formation of fins 50 in the core 20, according to the invention, is carried out in such a way as to optimize their efficiency in terms of heat dispersion, while only moderately affecting the inductance of the inductance circuit.

Avantageusement, les ailettes 50 sont agencées pour ne modifier que de façon modérée l'inductance du circuit à inductance 10. De préférence, l'inductance LM d'un circuit à inductance 10 présente un écart par rapport à l'inductance nominal L inférieur à 5%, encore plus préférentiellement, l'écart est inférieur à 2%.Advantageously, the fins 50 are arranged to only moderately modify the inductance of the inductance circuit 10. Preferably, the inductance L M of an inductance circuit 10 has a deviation from the nominal inductance L lower at 5%, even more preferably, the difference is less than 2%.

Afin de minimiser l'écart entre l'inductance d'un circuit à inductance 10 selon l'invention par rapport au même circuit à inductance 10, mais dépourvu de moyens de dissipation de chaleur, le protocole suivant peut être adopté :
Dans une première étape, un circuit à inductance, dépourvu de moyens de dissipation de chaleur, caractérisé par les paramètres géométriques A et I de son noyau, et du nombre de spires N de la bobine, est considéré.In order to minimize the difference between the inductance of an inductance circuit 10 according to the invention compared 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.

Une cartographie des lignes de flux magnétique dans le noyau est ensuite calculée avec précision, à l'aide par exemple d'un code de calcul par éléments finis, en considérant la géométrie de référence déterminée dans la première étape. Les simulations numériques en deux ou trois dimensions par éléments finis sont bien connues de l'homme du métier et ne sont pas détaillées dans cette description. Les zones du noyau où l'induction magnétique locale reste inférieure à 5 % de la valeur de l'induction magnétique moyenne dans ledit noyau sont identifiées en noir sur la figure 5.A map of the magnetic flux lines in the core is then calculated with precision, using for example a finite element calculation code, by considering the reference geometry determined in the first step. Numerical simulations in two or three dimensions by finite elements are well known to those skilled in the art and are not detailed in this description. The areas of 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 on the figure 5 .

Dans l'exemple illustré à la figure 5, le première partie du volume du noyau est, avantageusement, identifiée à la zone où l'induction magnétique reste inférieure à 5% de la valeur de l'induction magnétique moyenne dans le noyau, et disposée dans le prolongement d'au moins une extrémité de la barre.In the example shown in figure 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.

Cette méthode permet d'identifier de manière fine les zones du volume du noyau dans lesquelles les ailettes 50 peuvent être réalisées dans le noyau, et tout en ne modifiant que de manière modérée l'inductance du circuit à inductance 10 considéré.This method makes it possible to finely identify the zones of the volume of the core in which the fins 50 can be made in the core, and while modifying only moderately the inductance of the inductance circuit 10 considered.

De manière particulièrement avantageuse, les ailettes 50 sont parallèles aux lignes de champ susceptibles d'être créées lorsque le circuit à inductance 10 est en fonctionnement. Ainsi, l'écart entre l'inductance dudit circuit et l'inductance nominale peut être réduit.Particularly advantageously, the fins 50 are parallel to the field lines likely to be created when the inductance circuit 10 is in operation. Thus, the difference between the inductance of said circuit and the nominal inductance can be reduced.

Par ailleurs, la surface développée par chaque ailette peut être comprise entre 10 et 100 % de la surface A, par exemple 30%.Furthermore, the surface developed by each fin can be between 10 and 100% of the surface A, for example 30%.

La profondeur des ailettes 50 peut être comprise entre 10 et 50 % de la racine carrée de la surface A par exemple 30%.The depth of the fins 50 can be between 10 and 50% of the square root of the surface A, for example 30%.

Pour un noyau dont la barre 30 est cylindrique et de diamètre égal à 6 mm.For a core whose bar 30 is cylindrical and of diameter equal to 6 mm.

La largeur des ailettes 50 peut être comprise entre 0,1 et 2 mm, par exemple 1 mm.The width of the fins 50 can be between 0.1 and 2 mm, for example 1 mm.

L'espacement des ailettes 50 peut être compris entre 0,1 et 0,5 mm par exemple 0,2 mm.The spacing of the fins 50 can be between 0.1 and 0.5 mm, for example 0.2 mm.

Les ailettes 50 peuvent avoir une forme rectangulaire, ou triangulaire ou courbe.The fins 50 can have a rectangular shape, or triangular or curved.

De manière particulièrement avantageuse, l'espace entre les ailettes 50 peut être, lors d'une étape c1), comblé par un matériau non magnétique et bon conducteur thermique tel que le cuivre ou l'aluminium. Ainsi, selon ce mode de mise en œuvre permet de réaliser un pont thermique permettant de refroidir efficacement le noyau 20.In a particularly advantageous manner, the space between the fins 50 can be, during a step c1), filled with a non-magnetic material which is a good thermal conductor such as copper or aluminium. Thus, according to this mode of implementation, it is possible to produce a thermal bridge making it possible to effectively cool the core 20.

Afin d'augmenter encore la surface d'échange du noyau, des ailettes additionnelles 51 peuvent être rapportées sur la surface latérale extérieure 22 du cadre 21 autre que la surface évidée.In order to further increase the exchange surface of the core, additional fins 51 can be attached to the outer side surface 22 of the frame 21 other than the recessed surface.

De manière particulièrement avantageuse, les ailettes additionnelles 51 sont faites du même matériau magnétique que le noyau 20.Particularly advantageously, the additional fins 51 are made of the same magnetic material as the core 20.

Le noyau 20 peut comprendre un entrefer d'épaisseur inférieure à 5% de la longueur magnétique effective I.Core 20 may include an air gap with a thickness of less than 5% of the effective magnetic length I.

De manière avantageuse, l'entrefer est disposé au centre de la barre 30.Advantageously, the air gap is arranged in the center of the bar 30.

Tel que mentionné précédemment, la formation du noyau 20 peut être exécutée par moulage par injection de poudre de ferrite. A cet égard, l'homme du métier trouvera le détail de la méthode de moulage par injection de poudre dans le brevet FR2970194 [3 ]. Cette technique comprend une première étape de formation d'un mélange maître comprenant une matière organique (par exemple, des polyoléfines tels que le polyéthylène, le polypropylène), et des poudres inorganiques (par exemple, pour l'application visée, des oxydes de type ferrite, par exemple Mn1-xZnxFe2O4 et Ni1-xZnxFe2O4).As mentioned previously, the formation of the core 20 can be carried out by injection molding of ferrite powder. In this regard, the person skilled in the art will find the detail 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 Mn 1-x Zn x Fe 2 O 4 and Ni 1 - x Zn x Fe 2 O 4 ).

Le mélange maître est ensuite injecté dans un moule afin de lui conférer la forme voulue. La pièce moulée est alors déliantée (« debinded » selon la terminologie Anglo-Saxonne) à une température comprise entre 400 et 700°C (par exemple 500°C) de manière éliminer la matière organique. L'étape de déliantage est alors suivie d'une étape de frittage (« sintering » selon la terminologie Anglo-Saxonne), conduite à une température comprise entre 900 et 1300°C (par exemple 1220°C pour un oxyde de ferrite Mn1-xZnxFe2O4) permettant ainsi d'augmenter la densité de la pièce ainsi formée. Le noyau peut être réalisé en un seule pièce, ou peut comprendre un assemblage du plusieurs pièces (par exemple un assemblage de deux pièces en E, ou une pièce en E et une pièce en I, ou encore une pièce en U et une pièce en I). En fonction du mode de réalisation du noyau, un ou plusieurs moule peut être nécessaire.The masterbatch is then injected into a mold to give it the desired shape. The molded part is then debinded (“debinded” according to Anglo-Saxon terminology) at a temperature of between 400 and 700° C. (for example 500° C.) so as to eliminate the organic matter. The debinding step is then followed by a sintering step (“sintering” according to Anglo-Saxon terminology), carried out at a temperature between 900 and 1300°C (for example 1220°C for a ferrite oxide Mn 1 -x Zn x Fe 2 O 4 ) thus making it possible to increase the density of the part thus formed. The core may be made in a single piece, or may comprise an assembly of several pieces (for example an assembly of two E-pieces, or an E-piece and an I-piece, or even a U-piece and a I). Depending on the embodiment of the core, one or more molds may be required.

Le comblement de l'espace entre les ailettes 50, lors de l'étape c1), par un matériau conducteur est exécuté par une technique de surmoulage bien connu de l'homme du métier et décrite dans le document Ruh et al. [4].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].

Tel que représenté à la figure 7, la barre 30 peut présenter une section carrée, et être traversée de part en part selon une direction perpendiculaire au plan du cadre 21 par des cavités 41a et 41b à proximité des deux faces latérales 31 et 32 du noyau, respectivement. Les cavités 41a et 41 b sont alors comblées (par exemple par surmoulage) par un matériaux conducteur (par exemple du cuivre ou de l'aluminium) afin de constituer une partie du bobinage 40 destiné à être noyé dans la barre 30. Le bobinage 40 est alors complété, par exemple, par report de plaquettes métalliques 42 sur chacune des faces de la barre 30 parallèle au plan du cadre 21. Lesdites plaquettes 42 relient chacune une cavité 41a à une cavité 41b de manière à former un bobinage continu adapté pour générer une induction magnétique dans la barre 30.As depicted at figure 7 , the bar 30 may have a square section, and be crossed right through in a direction perpendicular to the plane of the frame 21 by cavities 41a and 41b close to the two side 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) in order 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 transfer of metal plates 42 on each of the faces of the bar 30 parallel to the plane of the frame 21. Said plates 42 each connect a cavity 41a to a cavity 41b so as to form a continuous winding adapted to generate magnetic induction in bar 30.

Ainsi, les spires de la bobine passent partiellement dans le volume de la barre. La bobine étant également le siège de dissipation d'énergie (par effet Joule), l'enterrement partiel des spires dans la barre permet également de mieux dissiper, via les ailettes 50 selon l'invention, la chaleur émise par la bobine.Thus, the turns of the coil partially pass through the volume of the bar. The coil also being the seat of energy dissipation (by Joule effect), the partial burial 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.

Ainsi, les moyens de dissipation de chaleur selon l'invention permettent de dissiper efficacement la chaleur produite dans un circuit à inductance. La température de fonctionnement des circuits à inductance est alors réduite, et beaucoup plus homogène dans le noyau.Thus, the heat dissipation means according to the invention make it possible to 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.

La mise en œuvre des moyens de dissipation de chaleur selon l'invention ne dégrade que de manière modérée, voire pas du tout, l'encombrement volumique du circuit à induction. En effet, lesdits moyens de dissipation de chaleur, contrairement à l'état de la technique, sont disposés dans le volume du noyau. Dit autrement, contrairement à l'état de la technique, les moyens de dissipation de chaleur ne nécessitent peu ou pas d'ajout de matière.The implementation of the heat dissipation means according to the invention degrades only moderately, or even not at all, the bulkiness of the induction circuit. Indeed, said heat dissipation means, contrary to the state of the art, are arranged in the volume of the core. In other words, contrary to the state of the art, the heat dissipation means require little or no addition of material.

Plus particulièrement, les moyens de dissipation de chaleur sont disposés dans des zones du noyau où l'induction magnétique est faible par rapport au reste du volume du noyau d'un circuit à induction en fonctionnement.More particularly, the heat dissipation means are arranged in areas of the core where the magnetic induction is low compared to the rest of the volume of the core of an induction circuit in operation.

Les moyens de dissipation selon l'invention permettent également d'envisager d'utiliser les circuits à inductance à des fréquences plus élevées, avantageusement supérieures 1 MHz.The dissipation means according to the invention also make it possible to envisage using inductance circuits at higher frequencies, advantageously greater than 1 MHz.

RÉFÉRENCESREFERENCES

  1. [1] US 6,920,039 B2 .[1] US 6,920,039 B2 .
  2. [2] A. M. LEARY, « Soft Magnetic Materials in High-Frequency, High-Power Conversion Applications », JOM, Volume 64, Issue 7, July 2012, Pages 772-781 .[2] AM LEARY, “Soft Magnetic Materials in High-Frequency, High-Power Conversion Applications”, JOM, Volume 64, Issue 7, July 2012, Pages 772-781 .
  3. [3] FR2970194 .[3] FR2970194 .
  4. [4] Ruh et al., « The development of two-component micro powder injection by moulding and sinter joining », Microsyst. Technol., 2011, 17:1547-1556 B .[4] Ruh et al., “The development of two-component micro powder injection by molding and sinter joining”, Microsyst. Technol., 2011, 17:1547-1556 B .

Claims (17)

  1. Inductance circuit, comprising:
    a) a core (20) made of a single-piece magnetic material with overall volume V, comprising a frame (21), and a bar (30) located at the centre of the frame (21) so as to form two rectangular magnetic loops symmetric about the bar (30), contiguous at a plane of symmetry of the bar (30), and with effective magnetic length I, the straight parts of the frame (21) have a cross-section with area A, and the bar (30) has a cross-section 2A equal to twice the cross-section A,
    b) a coil (40) comprising a number N of turns designed to generate magnetic induction in the bar (30),
    c) fins (50) exposed to the external environment and designed to dissipate heat, the fins being made of the same magnetic material as the core,
    the inductance circuit being characterised in that the fins (50) are at least partly within at least one volume zone (24a, 24b) of the frame (21), located along the prolongation of at least one end of the bar (30).
  2. Inductance circuit according to claim 1, in which the fins (50) are located in the bottom of at least one recess (25a, 25b) formed in the at least one volume zone (24a, 24b) of the frame, said at least one recess (25a, 25b) opening onto a lateral external surface (22) of said frame (21), and passing through the frame (21) from one side to the other along a direction perpendicular to the plane of the frame (21).
  3. Inductance circuit according to claim 2, in which the at least one recess (24a, 24b) tapers outwards from its bottom to the lateral external surface (22) of the frame (21).
  4. Inductance circuit according to claim 3, in which the at least one recess (25a, 25b) has a section parallel to the plane of the frame (21) with constant dimensions along a direction perpendicular to the plane (21) of said frame, said section is advantageously trapezoidal, and even more advantageously isosceles trapezoidal.
  5. Inductance circuit according to one of claims 1 to 4, in which the fins (50) are arranged such that the relative difference between the inductance of the inductance circuit (10) and the nominal inductance L is less than 5% and preferably less than 2%.
  6. Inductance circuit according to one of claims 1 to 5, in which the at least one volume zone (24a, 24b) is a zone in which, when the inductance circuit is in operation, the local magnetic inductance is less than 5% of the average value of the magnetic inductance in the core (20).
  7. Inductance circuit according to one of claims 1 to 6, in which the fins (50) are parallel to the plane defined by the frame (21).
  8. Inductance circuit according to one of claims 1 to 7, in which the area developed by each fin is between 10 and 100% of the area A
  9. Inductance circuit according to one of claims 1 to 8, in which the fins located in the at least one volume zone (24a, 24b) do not change the volume occupied by the frame (21).
  10. Inductance circuit according to one of claims 1 to 9, in which the additional fins (51) are added onto the external lateral surface (22) of the frame (21).
  11. Inductance circuit according to one of claims 1 to 10, in which the cross-section of the bar (30) is square and cavities pass through it from side to side along a direction perpendicular to the plane of the frame (21), the cavities being filled with an electrical conductor so as to form part of the coil (40).
  12. Inductance circuit according to one of claims 1 to 11, in which the space between the fins (50) is filled by a metallic material, advantageously a metallic material chosen from among aluminium and copper.
  13. Power converter comprising the inductance circuit (10) according to one of claims 1 to 12.
  14. Method of manufacturing an induction circuit according to one of claims 1 to 12, including the following steps:
    a) draw up 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 single-piece magnetic material with overall volume V, the core comprising a frame (21), and a bar (30) located at the centre of the frame (21) so as to form two rectangular magnetic loops symmetric about the bar (30), contiguous at the plane of symmetry of the bar (30), and with effective magnetic length I, the straight parts of the frame (21) have a cross-section with area A, and the bar (30) has a cross-section 2A equal to twice the cross-section A,
    b) use the previously drawn up map to identify zones within the volume of said core (20), of the inductance circuit (10) in operation for which the magnetic inductance is less than 5% of the average value of the magnetic inductance in the core (20),
    c) fabricate the core (20) considered in step a), the fins (50) being at least partly included in at least part of the zones of volumes identified in step b), and the fins (50) also being located along the prolongation of at least one end of the bar (30), the fins (50) being made of the same magnetic material as the core (20),
    d) form a coil (40) of a conducting material around a part of the core (20).
  15. Manufacturing method according to claim 14, in which the additional fins are added onto the external lateral surface (22) of the frame (21).
  16. Manufacturing method according to claim 14 or 15, in which a step c1) is performed after step c), to fill in the space between the fins (50) with a metallic material.
  17. Manufacturing method according to one of claims 14 to 16, in which step c) to fabricate the core (20) is done by powder injection moulding.
EP16823214.8A 2015-12-17 2016-12-16 Inductance circuit including a passive thermal management function Active EP3391393B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PL16823214T PL3391393T3 (en) 2015-12-17 2016-12-16 Inductance circuit including a passive thermal management function

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR1562598A FR3045921B1 (en) 2015-12-17 2015-12-17 INDUCTANCE CIRCUIT INCORPORATING A PASSIVE THERMAL MANAGEMENT FUNCTION
PCT/EP2016/081387 WO2017103074A1 (en) 2015-12-17 2016-12-16 Inductance circuit including a passive thermal management function

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EP3391393A1 EP3391393A1 (en) 2018-10-24
EP3391393B1 true EP3391393B1 (en) 2022-03-23

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EP (1) EP3391393B1 (en)
JP (1) JP6895967B2 (en)
KR (1) KR20180095030A (en)
CN (1) CN108475574B (en)
ES (1) ES2915837T3 (en)
FR (1) FR3045921B1 (en)
PL (1) PL3391393T3 (en)
WO (1) WO2017103074A1 (en)

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Publication number Priority date Publication date Assignee Title
CN113891544B (en) * 2021-08-26 2024-04-12 华为技术有限公司 Magnetic power device and power module using same

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US20090079528A1 (en) * 2007-09-25 2009-03-26 Flextronics Ap, Llc Thermally enhanced magnetic transformer

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Also Published As

Publication number Publication date
JP2019504488A (en) 2019-02-14
PL3391393T3 (en) 2022-07-11
WO2017103074A1 (en) 2017-06-22
FR3045921B1 (en) 2019-07-12
KR20180095030A (en) 2018-08-24
ES2915837T3 (en) 2022-06-27
CN108475574A (en) 2018-08-31
JP6895967B2 (en) 2021-06-30
CN108475574B (en) 2022-04-15
FR3045921A1 (en) 2017-06-23
EP3391393A1 (en) 2018-10-24

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