Abstract:
A light module includes a light emitting diode assembly defining a front side light emitting diode array and a rear side. The rear side is in thermal communication with a thermally conductive spreader, and a thermally conductive core is in thermal communication with the conductive spreader. The thermally conductive core includes an electrical conductor in operative communication with the front side light emitting diode array, and a plurality of appendages are disposed about the thermally conductive core such that they are in thermal communication with the conductive spreader.

Description:
BACKGROUND OF INVENTION  
         [0001]    The present invention relates generally to light emitting diode (LED) technology for lighting applications. It finds particular application in conjunction with spot module illumination applications and will be described with particular reference thereto. It will be appreciated, however, that the invention is also amenable to other like applications.  
           [0002]    Current spot module lamp technology relies primarily on halogen-type lamps for miniature reflector (MR) and parabolic reflector (PAR) type lamp illumination. The use of halogen-type lamps for spot lighting, however, has some drawbacks. For example, excessive heating can limit the usage of these types of lamps for commercial and consumer applications. Existing LED solutions have utilized standard, off-the-shelf, epoxy encapsulated, through hole LED sources in the light source array. Such configurations severely limit the output intensity of the lamp. Therefore, the potential market penetration that may be realized. by LED technology is correspondingly limited.  
           [0003]    Until now efforts in this technology area have been primarily focused on multicolor digital control of output light in order to provide “color wash” capabilities in various styles of packages. LED-based lamps have been designed to mimic the MR lamp footprint. However, because the LEDs used to construct these lamps are not thermally conductive, the thermal resistivity of such lamps being about 300° C./W, these LED lamps produce excessive heat. Therefore, thermal loading is a critical issue for conventional LED-based MR lamps.  
           [0004]    One attempt at addressing the thermal issue has been to package surface mount devices onto a metal clad printed circuit board (PCB). However, this is merely a planar approach where the PCB is not directly integrated into a heat sink fixture included in the body of the lamp. Therefore, it has not been possible to incorporate high powered LED lamps into MR packages.  
           [0005]    The present invention provides a new and improved apparatus and method which overcomes the above-referenced problems and others.  
         SUMMARY OF INVENTION  
         [0006]    In accordance with one aspect of the present invention, a light module is provided.  
           [0007]    It includes a light emitting diode assembly defining a front side light emitting diode array and a rear side. The rear side is in thermal communication with a thermally conductive spreader, and a thermally conductive core is in thermal communication with the conductive spreader. The thermally conductive core includes an electrical conductor in operative communication with the front side light emitting diode array, and a plurality of appendages are disposed about the thermally conductive core such that they are in thermal communication with the conductive spreader.  
           [0008]    In accordance with another aspect of the present invention, a light emitting diode assembly includes a light emitting face supported by a body through which electrical connection elements pass. The body includes a thermally conductive core in thermal communication with the light emitting face. The thermally conductive core includes the electrical connection elements in electrical communication with light emitting diodes in the light emitting face. A plurality of thermally conductive attachments surround the thermally conductive core, and they are in thermal communication with the light emitting diode assembly.  
           [0009]    In accordance with yet another aspect of the present invention, a lamp is provided for use in connection with spot module platforms. The lamp includes a plurality of LEDs arranged in an LED assembly having opposing forward and rearward facing sides. The forward facing side selectively provides illumination from the LEDs when power is supplied thereto. A heat sink is in thermal communication with the rearward facing side of the LED assembly, and it is arranged to draw heat from the LEDs. Heat dissipating means is in thermal communication with the heat sink, and it dissipates heat from the heat sink via convection.  
           [0010]    One advantage of the present invention is that it will reduce the thermal resistivity of LED-based spot modules in MR or PAR-type lamps or other novel lamp configurations.  
           [0011]    Another advantage of the present invention is that it makes possible the use of high powered LEDs within spot modules in MR or PAR-type lamps or other novel lamp configurations. The number of LEDs in the array may vary as desired for particular applications.  
           [0012]    Another advantage of the present invention is that it produces an LED-based lamp that substantially mimics the footprint of conventional MR lamps. The same approach can also be used in the case of PAR-type lamps.  
           [0013]    Another advantage of the present invention is that it produces brightness levels that surpass conventional clip-on filtered MR lamps.  
           [0014]    Another advantage of the present invention is that either primary or a combination of primary and secondary lens configurations may be used to focus the light output to provide angular output from the spot module ranging from 10° to 65° full-width-half-maximum.  
           [0015]    Another advantage of the present invention is that the operating temperature of the LED is reduced, thus increasing the operating lifetime of the LED based lamp.  
           [0016]    Still further advantages of the present invention will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description of the preferred embodiments. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0017]    The invention may take form in various components and arrangements of components, and in various steps and arrangements of steps. The drawings are only for purposes of illustrating a preferred embodiment and are not to be construed as limiting the invention.  
         [0018]    [0018]FIG. 1 illustrates a first embodiment of a device suitable to practice the present invention.  
         [0019]    [0019]FIG. 2 illustrates a second embodiment of a device suitable to practice the present invention.  
         [0020]    [0020]FIG. 3 illustrates a third embodiment of a device suitable to practice the present invention.  
         [0021]    [0021]FIG. 4 illustrates a fourth embodiment of a device suitable to practice the present invention.  
         [0022]    [0022]FIG. 5 illustrates another embodiment of a device suitable to practice the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0023]    With reference to FIG. 7, a device  8  includes an integrated array of high power LEDs  10 ,  12 ,  14  mounted to respective electrically insulative submounts  20 ,  22 ,  24 .  
         [0024]    The submounts  20 ,  22 ,  24  are secured to a metallic, rear side substrate  26  within respective wells  30 ,  32 ,  34 . Optionally, the LEDs  10 ,  12 ,  14  are directly secured to the metallic substrate  26 , thereby eliminating the use of submounts. The wells  30 ,  32 ,  34  in which the LEDs  10 ,  12 ,  14  reside are typically stamped or drilled directly into the substrate material to preferably form “reflector” shapes. However, other LED and well configurations are also contemplated. The submounts  20 ,  22 ,  24  (or optionally the LEDs  10 ,  12 ,  14 ) are secured to the rear side substrate  26 , which acts as a heatsink, via a highly thermally conductive material (e.g., solder, filled epoxies, heat tape and/or other thermally advantageous adhesives). The LEDs  10 ,  12 ,  14  are connected to electrical contacts  36  via conductors  38 .  
         [0025]    Lenses  40 ,  42 ,  44  cover the respective LEDs  10 ,  12 ,  14 . Optionally, a cap including a secondary optical lensing array is secured over the LEDs in the wells. In this case, the respective lenslets within the lensing array are mapped in a one-to-one relationship to the LEDs and the wells.  
         [0026]    The substrate  26  is secured to a heat spreader  60 , which includes a thermally conductive material such as metal. During use, heat generated by the LEDs  10 ,  12 ,  14  is passed to the substrate  26  and then transferred to the heat spreader  60 . The heat is distributed relatively evenly across the spreader  60 . The spreader  60  is secured to a thermally conductive core  62 . Thermally conductive fins  64  surround and extend from the core  62 . In the illustrated embodiment, the fins  64  form an independent assembly that is interference fit with the core  62 . In one embodiment, a tight interference fit is ensured by shrinking the core  62  and expanding the fins  64  prior to assembly. More specifically, the core&#39;s outer diameter is temporarily shrunk by cooling (e.g., freezing) the core  62  and the inner diameter of the heatsink fins  64  is temporarily expanded by heating the fins  64 . Then, the fin assembly is slid or otherwise positioned around the core  62 . Once the parts return to an ambient temperature, a tight interference fit is created between the fin assembly and the core  62 . Because the fins  64  contact the core  62 , heat is conducted from the core to the external environment via the fins  64 . Alternately, the heat spreader  60  and finned heat sink  64  may be cast as a single piece of thermally conductive material. Electrical conductors  68 ,  70  pass through the core  62  and the heat spreader  60  to supply power received by pins  72 ,  74  to the LEDs  10 ,  12 ,  14 . Finned heat sink shapes other than the one shown are contemplated in order to increase the outer surface area for improved thermal management, as well as providing a more aesthetically pleasing look to the “lamp”.  
         [0027]    It is understood to those skilled in the art that the number of LEDs in the array may vary according to the lamp output desired.  
         [0028]    FIGS.  2 - 5  illustrates alternate embodiments of the present invention. Components in these embodiments that correspond to the respective components of the embodiment illustrated in FIG. 1 are given the same numerical references followed by a primed (′) symbol. New components are designated by new numerals.  
         [0029]    With reference to FIG. 2, a device  77  includes a substantially flat substrate  78 , onto which the high power LEDs  10 ′,  12 ,  14 ′ are mounted. A cover  80  is secured over the substrate  78 . The cover includes recesses  82 ,  84 ,  86  that map in a one-to-one relationship to the LEDs  10 ′,  12 ′,  14 ′. The recesses  82 ,  84 ,  86  are shaped for forming respective reflectors (e.g., honeycomb shaped) that may be conic, parabolic or an alternately contoured shape to provide the desired light output beam pattern.  
         [0030]    With reference to FIG. 3, another embodiment of the present invention includes a device  90  having a plurality of high power LEDs  100 ,  102 ,  104  mounted on a metallic slug (e.g., a heat spreader)  110 . Optionally, each of the LEDs is mounted to the slug  110  via an electrically insulated submount. In this embodiment, each of the LEDs  100 ,  102 ,  104  is individually packaged as a discrete unit. Furthermore, each of the packages includes a single primary optic (e.g., a lens)  112 ,  114 ,  116 . The packages are electrically connected utilizing a circuit board  120 . The circuit board  120  is designed for optimum thermal dissipation from the discrete package, such as with a metal core printed circuit board. Optionally, the board incorporates through holes  122 ,  124 ,  126  to allow direct connection of a heatsink included in the package to the slug  110 , which acts as a heatsink for the assembly. The LEDs  100 ,  102 ,  104  are secured to the slug  110  via a thermally conductive adhesive or solder (e.g., heat tape). Alternatively, the thermally conductive adhesive or solder secures the LEDs  100 ,  102 ,  104  to the respective submounts and, furthermore, secures the submounts to the slug  110 . A circuit (not shown) on the board  120  electrically connects the LEDs  100 ,  102 ,  104  to a power source. The circuit is preferably formed from standard metallic and ceramic materials; however, other materials are also contemplated.  
         [0031]    With reference now to FIG. 4, an alternate embodiment of an LED module  130  includes a plurality of thermally conductive pillars or shaped protrusions  132  extending from a back side of the LED array as opposed to extending from the thermally conductive core as described above. It is now apparent to those skilled in the art that the location of the heat dissipating extensions or protrusions on the lighting module is variable and that other equally functional placements are possible. Moreover, extension or protrusion shape, physical continuity and material may also be varied for specific applications.  
         [0032]    [0032]FIG. 4 also illustrates a housing  136 , made from plastic, metal or other material, attached around a periphery of the light emitting face. Opposite the LEDs, an optic  140  is attached to the housing  136 , preferably, by threads, snapping, clipping, screwing or the like. The optic  140  may be tinted as desired, or color matched to the underlying LEDs to provide a desired output color, or may be clear, and can be formed as a flat window, a lens or other optical adjusting system or beam shaper, a multiple fresnel optic system, a diffuser, or otherwise. Optionally, the optic  140  may comprise a lenticular plate or an array of lenslets having optical axes that align with the underlying LEDs. In any event, preferably, the optic  140  attaches to the housing  136  so that an assortment of different types thereof are readily interchangeable as desired to selectively tailor the module  130  for various applications. Additionally, the housing  136  is optionally height adjustable and/or interchangeable with an assortment of different height housings to select a desired distance between the optic  140  and the underlying LEDs. Artisans will appreciate that by having a variable separation between the LEDs and the optic  140  in this manner, lens of different focal lengths can be accommodated.  
         [0033]    With reference to FIGURE S, an alternate fixture  150  includes a metallic substrate  152  or heat-dissipating fixture that doubles as a housing of a lamp assembly. Included are high power LEDs  156 ,  158  with corresponding lenses  160 ,  162 . Such a body  152  is preferably produced from aluminum or other thermally conductive materials in a suitably cast or machined shape. A circuit  170  for interconnecting the LEDs to a power source (not illustrated) may be directly patterned on the housing assembly or consist of a printed wiring board affixed to the top surface of the housing. The circuit includes openings for the LEDs  156 ,  158  and optionally includes mechanical features for attaching the lenses  160 ,  162 . Electrical connection to the circuit  170  is made through contacts  174  in the central portion which may be adapted to receive a power supply or leads from an off-device power supply. Alternately, electrical connection may be had through vias or holes in the housing. The hollow central portion of the housing additionally may be used to contain other electrical control circuitry for the LEDs  156 ,  158  and the bottom of the housing may be attached to a suitable connector design for connection to a socket. Heat dissipating fins  178  surround the exterior of the assembly. It is understood to those skilled in the art that the number and color of LEDs in the array in a single housing may vary according to the lamp output desired. Moreover, the number and arrangement of attached heat dissipating fins is variable as desired.  
         [0034]    The mechanical designs disclosed in the devices of the present invention have thermal resistivities on the order of about 40° C./W or less (e.g., about 15° C./W). Furthermore, it is to be understood that the devices  8 ,  77 ,  90 ,  130 ,  150  may be designed to mimic the footprint of conventional lamps of the MR or PAR-type (e.g., MR-16 lamps).  
         [0035]    Preferably, the high power LEDs used in the present invention produce saturated colors (e.g., green, blue, cyan, red, orange, yellow, or amber) and/or white light such that the respective lamps produce at least about 60 lumens of light. Multiple colors within an array are also envisioned.  
         [0036]    Preferably, the lenses and lenslets of the present invention are of the refractive, diffractive or Fresnel lens variety and are designed to produce spot light beams ranging from about a 10° to about a 65° spread for use in spot light applications.  
         [0037]    It is also contemplated that power conversion components be included within the devices  8 ,  77 ,  90 ,  130 ,  150  for converting alternating current (AC) inputs (e.g., 12 VAC, 120 VAC, or 220 VAC) to the direct current, low voltage power used to power the LEDs. Power conversion components for universal AC inputs are also contemplated.  
         [0038]    It is also contemplated that the individual LEDs within the devices  8 ,  77 ,  90 ,  130 ,  150  be selectively operated. In this case, individual or group LED addressing can be accomplished either locally with suitable control circuitry located in the lamp assembly, or through communication means for selectively addressing the individual LEDs remotely.  
         [0039]    The invention has been described with reference to the preferred embodiment. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the invention be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.