FR3004238A1 - LIGHT EMITTING DEVICE COMPRISING A THERMAL DISSIPATOR OF AN EMISSIVE COMPONENT DEPORTING FROM THE BACK OF A REFLECTOR - Google Patents

Abstract

The light emitting device (101) comprises: an emitting component (102) for emitting a light beam (103) into an operating configuration of said device (101); a reflector (104) provided with a wavelength converter (105) to which the light beam (103) is oriented; and a heat sink (106) of heat from the emissive component (102) in the operating configuration. In addition, at least a portion of the reflector (104) is disposed between the emissive component (102) and the heat sink (106).

Description

TECHNICAL FIELD OF THE INVENTION The invention relates to the field of lighting and more particularly indirect lighting by light emitting diode. The invention more particularly relates to a light emitting device comprising: an emissive component for emitting a light beam into an operating configuration of said device; a reflector provided with a wavelength converter to which the light beam is oriented; and a heat sink of heat from the emissive component in the operating configuration. STATE OF THE ART In the field of lighting, new technologies are applied so as to present products whose energy consumption is reduced. In particular, it is used so-called indirect lighting devices where the light beam from a diode is modified by phosphorus and reflected in a main direction of illumination of the device. FIG. 1 illustrates such a lighting device known from patent application PCT / US2009 / 002704. The lighting device 1 comprises a blue diode 2 generating a beam 3 modified by a lens 4 so as to converge in the direction of a phosphor layer 5, then to be emitted as main lighting via a reflector 6 in a the direction opposite the beam 3. The phosphor layer 5 and the diode 2 are respectively cooled by a first heat sink 7 and a second heat sink 8. The second heat sink 8 causes a partial occultation of the reflector 6, thus reducing the light power of the lighting device. In addition, the higher the power of the diode 2, the more this second heat sink 8 must be increased in size, decreasing all the light power of the lighting device. The heatsink 8 of the diode 2 is located under the phosphor layer.

Also, the heat dissipated by the dissipator 8 rises towards the phosphor layer and warms it, which reduces the conversion efficiency.

OBJECT OF THE INVENTION The object of the present invention is to propose a solution that makes it possible to improve the illumination that a light-emitting device can provide, especially in the context of an indirect lighting device.

This object is particularly aimed at by means of a light emitting device comprising: an emissive component intended to emit a light beam in an operating configuration of said device; a reflector provided with a wavelength converter to which the light beam is oriented; a heat sink of the heat emitted from the emissive component in the operating configuration; and in that at least a portion of the reflector is disposed between the emissive component and the heat sink. Advantageously, the reflector is thermally isolated from the emissive component. Preferably, the device comprises a thermal coupling member between the heat sink and the emissive component. According to one embodiment, at least a portion of the thermal coupling member passes through the reflector, preferably at a central optical axis of the reflector. This thermal coupling member may comprise a material whose thermal conductivity is greater than 50 W / m · K, especially copper or aluminum. Advantageously, the reflector is assembled to the rest of the device via a connecting element configured so as to thermally isolate the reflector from the heat coming from the emissive component in the operating configuration. For example, the connecting element is attached, on the one hand, to the reflector and, on the other hand, to the thermal coupling member or to a portion of the emissive component. This connecting element can be formed in a material whose thermal conductivity is less than 1W / m.K. According to one embodiment, the coupling member comprises a base supporting the emissive component, the base and the heat sink being kept at a distance by a spacer element of the thermal coupling member, said spacer element. crossing the reflector.

Advantageously, the spacer element comprises a heat pipe. The reflector may comprise a thermal dissipation member thermally dissociated from the heat sink and arranged on a face of the reflector opposite a reflective face of the reflector comprising the converter. In one embodiment, the wavelength converter is phosphor and the emissive component has one or more blue diodes. Preferably, the device comprises an optics configured so as to be traversed by the light beam after its at least partial conversion by the wavelength converter. Advantageously, the reflector comprises a first portion comprising the wavelength converter and a second portion forming a collimation reflector.

BRIEF DESCRIPTION OF THE DRAWINGS Other advantages and features will become more clearly apparent from the following description of particular embodiments of the invention given by way of nonlimiting example and represented in the accompanying drawings, in which: FIG. 1 illustrates a light emitting device according to the prior art, - Figure 2 illustrates a first particular embodiment of the invention, - Figure 3 illustrates a second particular embodiment of the invention, - Figure 4 illustrates an improvement of the transmitter device implementing an optical system, - Figure 5 illustrates an alternative embodiment of the invention. DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION The light emitting device described below differs from the prior art in particular in that at least a portion of a reflector is disposed between an emissive component and a heat sink of the emissive component.

As illustrated in FIG. 2, a light emitting device 101 comprises an emitting component 102 intended to emit a light beam 103 in an operating configuration of said device 101. By "operating configuration" is meant a lit state of the transmitting device of light 101. Furthermore, the light emitting device 101 comprises a reflector 104 provided with a wavelength converter 105 to which the light beam 103 is oriented, and a heat sink 106 of the heat emitted from the emitting component 102 in the operating configuration.

The heat sink 106 is preferably made of a material of high thermal conductivity (that is to say of thermal conductivity advantageously greater than 50 W / m.K) such as aluminum or copper. The efficiency of the heat sink 106 is proportional to the exchange surface with the air. This heat sink 106 can be made by different machining techniques, such as extrusion. Schematically, it has a base 106a and fins 106b extending from the base 106a, and is formed of a single material or several materials. The heat sink 106 may be passive, that is to say simply comprise a radiator, or be active as a fan (not shown) associated or not with a radiator. The reflector 104 advantageously comprises a metallic element 107, preferably made of aluminum of high reflectivity. This metal element 107 may be made in one or more assembled parts. The wavelength converter 105 may be a material coated on at least a portion of the reflector 104 (in particular on the metal element 107), for example by spray or dipping technique. Of course, the wavelength converter 105 being part of the reflector 104, it is configured to allow the conversion of at least a portion of the light beam 103 and the reflection 103a of said at least one converted part. At least a portion of the reflector 104 is disposed between the emitting component 102 and the heat sink 106. In other words, the heat sink 106 is disposed behind the reflector 104 while the emitting component 102 is disposed in front of the reflector 104. This arrangement In particular, the heat sink 106 can be displaced in an area where it will not interfere with the reflector 104. The illumination efficiency of the light source formed by the emitting component 102 will thus be magnified. In fact, most of the emitting components 102 have a yield less than 1, which means that some of the electrical energy injected into the component, which is not useful for the desired function, produces heat. . The good dissipation of this heat in the system is necessary in order to avoid the heating of the emissive component. Preferably, the wavelength converter 105 is phosphorus and the emitting component 102 comprises one or more blue diodes, in particular for the purpose of creating white illumination by the emitting device. In the present description, the term "diode" means a light-emitting diode. It is preferentially chosen one or more blue diodes because they have a good yield. In fact, a white light based on blue diode (s) is advantageously constituted by a primary source (here one or more blue diodes) which excites a luminescent material (phosphorescent in English). The luminescent material absorbs a portion of the primary radiation and re-emits a secondary wavelength (typically yellow) in a longer wavelength. The combination of blue and yellow is then a source of white radiation. The problem related to the heat generated by the emitting component 102 is exacerbated in the context of an emissive component with one or more diodes in combination with phosphorus. Indeed, in the case of diodes only about 20% to 40% of the electrical energy injected is useful and produces light, the remainder being converted into heat. Too great a rise in the temperature of the light emitting device notably leads to a drop in yield, to color drifts, and to a reduction in reliability. The cooling of the emissive component 102 is therefore all the more important. On the other hand, in conversion-type emitters, in particular phosphorus, the conversion efficiency is itself less than 1, which also leads to localized heat production at the conversion zone and may in particular still decrease yield and, in extreme cases, degrade phosphorus. In this sense, the wavelength converter 105 associated with the reflector 104 makes it possible to shift the latter from the emissive component 102 and to limit the mutualized rise in temperature of the emissive component 102 and the wavelength converter 105. that in general, the reflector 104 is thermally insulated from the emissive component 102. This thermal insulation limits the influence of the rise in temperature of the emitting component 102 vis-à-vis the wavelength converter 105 and vice versa. As a result of what has been said above that the light emitting device comprises a main illumination direction F1 determined by the reflector 104 and substantially opposite to an initial illumination direction F2 determined by the orientation of the light beam 103 from the emitting component 102. In other words, the indirect illumination via the light emitting device 101 is done in at least three steps: the generation of a first beam 103 by the emitting component 102 in the direction of the reflector 104; the at least partial modification of the wavelength of the first beam 103 by the wavelength converter 105, - the generation of a second beam 103a from the reflector by reflection of the first beam 103. Advantageously, the device 101 comprises a thermal coupling member 108 between the heat sink 106 and the emissive component 102. This thermal coupling member 108 then makes it possible to transfer er the calories from the operation of the emissive component 102 to the heat sink 106 for their evacuation. It is therefore advantageous to promote the best transfer of calories. In other words, the thermal coupling member 108 comprises or consists of a material whose thermal conductivity is preferably greater than 50 W / m · K, in particular copper or aluminum. Thus, the invention makes it possible to minimize the heat dissipation at the emissive component 102, heat that would go up towards the wavelength converter 105 and heat it up. This optimizes the conversion efficiency of the converter 105 and thus the optical efficiency of the device 101. According to one embodiment, at least a portion 108a of the thermal coupling member 108 passes through the reflector 104, preferably at the level of a central optical axis Al of the reflector 104. Thus, the reflector 104 may comprise a hole through which said at least one portion 108a of the thermal coupling member 108 passes, said through hole connecting a reflection face of the reflector to a opposite side, said rear, said reflection face. The central optical axis Al defines the illumination direction of the transmitting device 101. This configuration makes it possible to limit the impact on the level of the illumination of the light emitting device.

According to a particular embodiment, the reflector 104 is assembled, in particular mechanically, to the rest of the device 101 by means of a connecting element 109 configured so as to thermally isolate the reflector 104 from the heat emitted from the emitting component 102 in the operating configuration. The connecting element 109 thus has two functions: a function of mechanical retention of the reflector and a thermal insulation function of the reflector 104 vis-à-vis the emissive component 102. Preferably, as shown in Figures 2 and 3, the connecting element 109 is fixed, on the one hand, to the reflector 104 and, on the other hand, to the thermal coupling member 108 (FIG. 2) or to a part of the emitting component 102 (FIG. a printed circuit of the emissive component (or PCB in English for "Printed Circuit Board"). In other words, the connecting element 109 can be in contact with the reflector 104 and the coupling member 108, or be in contact with the reflector 104 and said portion of the emissive component 102. In the case where the connecting element 109 and the thermal coupling member 108 (or possibly the portion of the emitting component 102) are in contact, they are further configured so that the thermal resistance between the reflector 104 and the heat sink 106 is at least ten times greater than that between the emissive component 102 and the heat sink 106. In a particular example, the connecting element 109 is formed of a material whose thermal conductivity is preferably less than 1W / mK For example, the connecting member 109 is made of plastic or glass. According to a particular embodiment that can be seen in FIGS. 2 and 3, the coupling member 108 comprises a base 110 supporting the emissive component 102, the base 110 and the heat sink 106 being held at a distance by a spacer element 111 of FIG. the thermal coupling member 108. In the example of Figures 2 and 3, the spacer element 111 passes through the reflector 104. The base 110 is advantageously made of a highly heat-conducting material such as copper or aluminum. 'aluminum. The role of the base 110 is to collect a maximum of calories from the emitting component 102 during its operation. The bracing element 111 makes it possible to transfer these calories to the heat sink 106. The base 110 can also be integrated in a printed circuit of the emissive component 102, in this case the printed circuit is of metallic type, also known as the acronyms. MCPCB (Metal Core Printed Circuit Board) or IMS (English "Insulated Metal Substrate") so as to form the base 110 of the thermal coupling member 108.

Preferably, the bracing member 111 comprises, or consists of, a heat pipe. The use of a heat pipe is advantageous in the sense that it makes it possible to reduce the thermal resistance of the spacer element 111 by a factor of 10. According to a preferred exemplary embodiment, the emitting component 102 comprises a printed circuit 112 on which are disposed diodes 113, in particular blue, said printed circuit 112 resting on the base 110 and being traversed by the spacer element 111. In other words, the printed circuit 112 may comprise an opening hole connecting two opposite faces of the printed circuit 112, a first of the two opposite faces resting on the base 110 and a second of the two opposite faces having the diodes 113 is oriented towards at least a portion of the reflector 104.

In general, when the emitting component 102 rests on the base 110, there is interposed, between the emissive component 102 and the base 110, a material promoting heat exchange such as thermal grease or a thermal conductive polymer film also known under the acronym TIM for "Thermal Interface Material". In a manner applicable to all that has been said above, the reflector 104 is advantageously positioned so that the emitting component 102 does not illuminate live without reflection. In other words, all the light beam from the emitting component 102 is oriented towards the wavelength converter 105 of the reflector so as to be at least partially converted and totally reflected. It has been stated above that it is better to avoid or limit the rise in temperature of the wavelength converter 105, especially when the latter is based on phosphorus. For this, the reflector 104 can itself participate in the heat dissipation. In general, the reflector 104 optionally comprises a thermal dissipation member 114 thermally dissociated from the heat sink 106 (in other words the heat dissipating member 114 and the heat sink 106 are separate parts) and arranged on one face of the reflector 104 opposite a reflective face of the reflector 104 comprising the wavelength converter 105. As shown in Figures 2 and 3, the heat dissipating member 114 may comprise fins promoting cooling.

According to a particular embodiment illustrated in FIG. 4, the device comprises an optics 115 configured so as to be traversed by the light beam after its at least partial conversion by the wavelength converter 105. advantageously to obtain a main beam suitable for satisfying the desired lighting. Preferably, the reflector 104 includes a first portion 104a including the wavelength converter 105 and a second portion 104b forming a collimation reflector, advantageously, when optical 115 is present, it is disposed at the boundary between the first and second parts 104a, 104b. In other words, the reflector may comprise a reflection face delimiting a first portion 104a and a second portion 104b of the reflector 104 whose separation limit defines the placement of the optic 115. The first portion is covered, preferably, completely by the wavelength converter 105 and the second part preferably has only a reflection function.

It is therefore understood that it is possible for the device to comprise either optics 115, or an extension constituted by the second part 104b forming a collimation reflector, or the combination of optics 115 with second part 104b forming a reflector. collimation. Advantageously, the optics 115 is configured to modify the light beam after at least partial conversion by the wavelength converter 105 into a reflective or refractive beam through at least one lens of said optics 115. An example of an emissive component 102 with one or more diodes has been given. Optionally, the diodes may be blue or ultraviolet light emitting diodes phosphor exciter forming the wavelength converter 105. These diodes may also be placed side by side with diodes of other colors (red for example) , which may or may not excite phosphorus (the flux emitted by them may be diffused only by phosphorus) and thus allow an adjustment of the color of the light emitted by the system (as a function of the current applied to these diodes, for example ). It has been described above a reflector which was traversed by a portion of the thermal coupling member. Those skilled in the art will be able to implement different structures as long as there is indeed an interposition of at least a portion of the reflector between the emissive component and the heat sink of the emissive component. By way of example, FIG. 5 illustrates such an example where the thermal coupling member 108 transports the heat sink 106 out of the reflective field of the reflector 104. Although it makes it possible to improve the existing one, this embodiment does not will not be preferred because a portion of the thermal coupling member 108 is still obstructing a portion of the reflector 104. Advantageously, when the coupling member comprises a base and the bracing member, a judicious method of assembly can be the following: - provide a thermal coupling member provided with the base and an element intended to form a spacer with the heat sink, said member extending from the base so as to have a free end opposite to the base, - insert the emissive component via a hole opening of said emissive component through the free end of the element intended to form a spacer with the heat sink, - mount the ref reader, preferably by inserting it through a hole emerging from said reflector through the free end of the element intended to form a brace with the heat sink, and fix it either to the emissive element or to the element intended to form a brace with the heatsink - fix the heatsink at the free end to form the spacer. The emissive component can have any type of shape, for example circular or rectangular.

The invention also relates to a luminaire comprising at least one light emitting device as described or a plurality of light emitting devices 101 as described above. Such a luminaire can generate white light of very high power, typically greater than 5000 Im.

In general, the invention, by virtue of these various embodiments, makes it possible: to defer the wavelength converter in particular to phosphorus so as to prevent it from heating because of the emissive component, thus inducing a poor performance of the component emissive and vice versa (and less flux reabsorbed by the chip after conversion), - to cool the emissive component and the converter efficiently on dissociated thermal paths, - to simplify the assembly of the device, - to present a structure very well adapted to very bright light sources.

Claims (14)

REVENDICATIONS1. A light emitting device (101) comprising: - an emitting component (102) for emitting a light beam (103) in an operating configuration of said device (101), - a reflector (104) having a length converter wave (105) to which the light beam (103) is oriented, and - a heat sink (106) of heat from the emitting component (102) in the operating configuration, characterized in that at least a portion of the reflector (104) is disposed between the emissive component (102) and the heat sink (106). 2. Device according to claim 1, characterized in that the reflector (104) is thermally insulated from the emissive component (102). 3. Device according to claim 1 or claim 2, characterized in that it comprises a thermal coupling member (108) between the heat sink (106) and the emissive component (102). 4. Device according to the preceding claim, characterized in that at least a portion (108a) of the thermal coupling member (108) passes through the reflector (104), preferably at a central optical axis of the reflector ( 104). 5. Device according to one of claims 3 or 4, characterized in that the thermal coupling member (108) comprises a material whose thermal conductivity is greater than 50W / m.K, including copper or aluminum. 6. Device according to any one of the preceding claims, characterized in that the reflector (104) is assembled to the rest of the device (101) via a connecting element (109) configured to thermally insulate the reflector (104) of heat from the emissive component (102) in the operating configuration. 7. Device according to the preceding claim and claim 3, characterized in that the connecting element (109) is fixed, on the one hand, to the reflector (104) and, on the other hand, to the coupling member thermal (108) or part of the emissive component (102). 8. Device according to one of claims 6 or 7, characterized in that the connecting element (109) is formed of a material whose thermal conductivity is less than 1W / m.K. 9. Device according to claim 3 and any one of the preceding claims, characterized in that the coupling member (108) comprises a base (110) supporting the emissive component (102), the base (110) and the heat sink (106) being remotely maintained by a spacer member (111) of the thermal coupling member (108), said spacer member (111) passing through the reflector (104). 10. Device according to the preceding claim, characterized in that the spacer element (111) comprises a heat pipe. 11. Device according to any one of the preceding claims, characterized in that the reflector (104) comprises a heat dissipating member (114) thermally dissociated from the heat sink (106) and arranged on a face of the reflector (104) opposite to a reflective face of the reflector (104) including the converter (105). 12. Device according to any one of the preceding claims, characterized in that the wavelength converter (105) is phosphorus and in that the emitting component (102) comprises one or more blue diodes (113). 13. Device according to any one of the preceding claims, characterized in that it comprises an optical (115) configured to be traversed by the light beam after its at least partial conversion by the wavelength converter ( 105). 14. Device according to any one of the preceding claims, characterized in that the reflector comprises a first portion (104a) having the wavelength converter (105) and a second portion (104b) forming a collimating reflector.