Abstract:
An illumination device and method are disclosed. The device may have a discrete driver module comprising circuitry for supplying power to and controlling at least one light source. The device may also have a connector for electrically connecting to a source of power. The device may also have a discrete lighting module for electrical connection to but otherwise physically separate from the driver module. The lighting module may be configured to receive the light source. The lighting module may have (i) a mechanism for mounting the lighting module to a lighting fixture, and (ii) a temperature sensor for measuring a temperature of the light source.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 14/592,422, filed on Jan. 8, 2015 and entitled “RECESSED CAN DOWNLIGHT RETROFIT ILLUMINATION DEVICE,” which is a continuation of U.S. patent application Ser. No. 13/293,372, filed on Nov. 10, 2011, now U.S. Pat. No. 8,950,898 and entitled “RECESSED CAN DOWNLIGHT RETROFIT ILLUMINATION DEVICE,” which claims priority to U.S. Provisional Application No. 61/412,096, filed Nov. 10, 2010 and entitled “RECESSED CAN DOWNLIGHT RETROFIT ILLUMINATION DEVICE.” 
     
    
     FIELD OF THE INVENTION 
       [0002]    In various embodiments, the present invention relates to illumination devices, in particular illumination devices incorporating light-emitting diodes. 
       BACKGROUND 
       [0003]    One of the most common light fixtures is the recessed can downlight (RCD), which is an open-bottom can that contains a light bulb, most commonly an incandescent bulb. The fixture is typically connected into the power mains at 120 to 277 volts, 50/60 Hz. RCDs are generally installed during the construction of a building before the ceiling material (such as plaster or gypsum board) is applied. Therefore, they are not easily removed or substantially reconfigured during their lifetime. 
         [0004]    RCDs generally also accommodate incandescent light bulbs of various sizes (which, in a 4-inch-diameter RCD, include A19 (the common Edison-base bulb), PAR20, PAR16, R16, R20, etc., where the numerical designation refers to the diameter of the bulb and the letter to the bulb type or shape). These bulbs all have different overall dimensions (i.e., length, width, and diameter), and have varied light-distribution capabilities. For example, various bulbs have narrow, medium, or wide (flood) distributions. Therefore, the internal features of the RCD are constructed to accommodate many (if not all) various bulb types. Such features include mechanisms to adjust the vertical position of the bulb socket, as well as various “face plates” that cover the bottom of the fixture and provide a decorative finish that fits flush with the ceiling. Moreover, the face plate may contain a recessed reflector which channels and distributes the light. Because there are so many different light bulbs and finishes, there are a very large number of trim rings and optics combinations, in addition to the various spacers that accommodate the bulbs. Thus a complex arrangement of parts is needed for each RCD that is produced. 
         [0005]    Because LEDs have very high efficiency (e.g., 100 lumens per watt compared to 10-15 lumens per watt for incandescent or halogen lights) and a long lifetime (e.g., 10,000-100,000 hours), they are attractive for virtually all lighting applications. However, even a dedicated LED-based downlight would have the disadvantage of only being compatible with new construction (without a prohibitively costly overhaul of an entire lighting system and related infrastructure), and thus would be unavailable for retrofitting into the large host of existing incandescent-based RCDs. Moreover, because the LED technology itself is rapidly changing, LED-based fixtures become obsolete as the LED technology, as well as the optics and cooling technology vital to performance, improve. 
         [0006]    LED-based light bulbs represent a logical alternative. These products contain electronics, optics and heat sinks all in a form factor identical to that of the particular light bulb to be replaced. Such designs may be quite difficult to achieve, however, and generally necessitate strict control over power consumption in order to maintain low enough operating temperatures to avoid thermally-induced premature failure. Hence, the light output of such LED light bulbs is typically well below that of the incandescent light bulbs they replace. For example, a PAR20 LED lamp from Lighting Sciences has a rated output of 350 lumens while a conventional 50 watt PAR20 incandescent bulb has light output in the range of 600-750 lumens. Furthermore, replacement of the light bulb product means disposing and replacing the entire suite of electronics, optics, and heat sink—a costly and wasteful proposition. 
         [0007]    Thus, there is a need for retrofit devices for RCDs based on LEDs that are compatible with a wide range of differently sized and/or shaped RCD fixtures, and that are easily upgradable with different light sources and/or associated electronics. 
       SUMMARY 
       [0008]    Embodiments of the present invention advantageously enable retrofitting of a standard incandescent- or halogen-based RCD and also simplify and reduce the cost of eventual upgrades as the technology is improved. Such embodiments have some or all of the following advantages: 
         [0009]    1) Modularization of the electronics, optics and cooling elements. 
         [0010]    2) Backward compatibility to existing RCDs. 
         [0011]    3) Upgradable in the field as the technology evolves. 
         [0012]    4) Reduction in the number of products needed across platforms. 
         [0013]    5) Compatibility with existing light-bulb bases without being limited by them. 
         [0014]    6) Independent of the light bulb being replaced yet conforming to the volume of existing RCD fixtures. 
         [0015]    In one example, an illumination device is provided. The exemplary device may have a discrete driver module, a connector, and a discrete lighting module. The exemplary discrete driver module may have circuitry for supplying power to and controlling at least one light source. The connector may be for electrically connecting to a source of power. The discrete lighting module may be configured for electrical connection to but otherwise physically separate from the driver module. The lighting module may be configured to receive the at least one light source. The lighting module may have (i) a mechanism for mounting the lighting module to a lighting fixture, and (ii) a temperature sensor for measuring a temperature of the at least one light source. 
         [0016]    These and other objects, along with advantages and features of the invention, will become more apparent through reference to the following description, the accompanying drawings, and the claims. Furthermore, it is to be understood that the features of the various embodiments described herein are not mutually exclusive and can exist in various combinations and permutations. As used herein unless otherwise indicated, the terms “substantially” and “approximately” mean.+−0.10%, and, in some embodiments, .+−0.5%. The term “consists essentially of” means excluding other materials that contribute to function, unless otherwise defined herein. Nonetheless, such other materials may be present, collectively or individually, in trace amounts. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    In the drawings, like reference characters generally refer to the same parts throughout the different views. Also, the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. In the following description, various embodiments of the present invention are described with reference to the following drawings, in which: 
           [0018]      FIG. 1  is a schematic cross-section of an RCD fixture in accordance with the prior art; and 
           [0019]      FIG. 2  is a schematic cross-section of an LED-based illumination device in accordance with various embodiments of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0020]      FIG. 1  depicts a standard RCD fixture  100  in accordance with the prior art. The fixture  100  typically houses and supplies electrical power to an incandescent or halogen light bulb  110 , power being supplied via, e.g., an electrical conduit  120  connecting to the AC mains of the building in which the fixture  100  resides. The fixture  100  includes a can  130 , which is typically recessed into a ceiling  140 . The fixture  100  also includes an electrical socket  150  that is compatible with the electrical connector of the light bulb  110 . As detailed above, retrofitting the fixture  100  for compatibility with a different type or size of light bulb  110  is difficult or impossible due to the fixed dimensions of the fixture  100 . 
         [0021]      FIG. 2  depicts an illumination device  200  in accordance with various embodiments of the present invention. As shown, the illumination device  200  includes or consists essentially of a discrete driver module  210  and a discrete lighting module  220 . The driver module  210  and lighting module  220  are collectively sized to fit within the RCD fixture or can  130 , and may thus be utilized as a replacement lighting product for light bulb  110  shown in  FIG. 1 . The RCD fixture is typically cylindrical, and the cross-section of the fixture may be round, square, or have another shape. Generally the fixture is mounted to a structural element in a building, such as a ceiling beam, and may be connected to the building electrical system via electrical conduit  120  and an electrical junction box (not shown). 
         [0022]    In preferred embodiments of the present invention, the driver module  210  and lighting module  220  are electrically connected, e.g., via an electrical cable  230 , but are otherwise physically separate. The electrical cable  230  may thus be the only physical connection between modules  210 ,  220 . As shown, cable  230  generally has a length sufficient to position the lighting module  220  proximate the opening of the RCD fixture but may have shorter or longer lengths, thereby facilitating the removal of at least a portion of device  200  from the RCD fixture and subsequent placement within a different RCD fixture having different dimensions, e.g., a different depth (i.e., of recess into the ceiling  140 ). Thus, in many embodiments of the invention the cable  230  provides substantially no physical support to the lighting module  220 . Instead, the lighting module  220  is preferably positioned within the RCD fixture via a mounting mechanism  240 , which may include or consist essentially of, e.g., one or more springs or spring clips (that may be coated to enhance their friction against the inner surface of the RCD fixture). The modular design of preferred embodiments of the present invention obviates the need for a dedicated “sleeve” or other insert housing the modules  210 ,  220  within the RCD fixture. The electrical cable  230  may be detachable from the driver module  210  and/or the lighting module  220 , allowing for the replacement or upgrading of any of modules  210 ,  220  or cable  230 . For example, the cable  230  may terminate in removable snap-in connectors at one or both ends. 
         [0023]    The lighting module  220  features one or more LEDs  250 , which may be packaged (e.g., with integrated optics and/or encapsulation) and/or substantially unpackaged (e.g., bare dies), and which may individually and/or collectively emit any of a variety of colors of light, including white light. An optic  260  (e.g., a refractive, diffusive, or focusing lens) may be integrally or removably connected to one or more of the LEDs  250  in order to direct the light emitted from the LEDs  250  in a particular direction or to give the light a desired pattern or color. As mentioned above, the entire lighting module  220  may be mounted, e.g., gimbal mounted, to facilitate aiming of the light emitted therefrom in a desired direction. 
         [0024]    A trim ring  270  may provide a decorative cover to the interface between the ceiling  140  and the RCD fixture and preferably covers the seam therebetween. The trim ring  270  may also facilitate the exchange of air with the outside via one or more vents  280 , e.g., louvers or a mesh grill, while obscuring portions of device  200  within the RCD fixture. In some embodiments, a decorative feature is created with such openings, e.g., an illumination pattern created from the light from one or more (in some embodiments dedicated) LEDs in the lighting module  220 . (Such decorative illumination is preferably distinct from the direct illumination emanating directly from the LEDs  250  out of the RCD fixture.) The trim ring  270  may be attached to the mounting mechanism  240  and may also provide mechanical support for the lighting module  220 . The lighting module  220  may be substantially flush-mounted to the trim ring  270  or may be recessed to reduce glare. The lighting module  220  may be removably attached to the trim ring  270  by one or more pins, clamps, or other suitable fasteners. As shown, the trim ring  270  typically overlaps the edge of the RCD fixture and at least a portion of the lighting module  220 . Although in some embodiments the LEDs  250  and/or the optics  260  are directly visible within the RCD fixture, in other embodiments the trim ring  270  incorporates a screen  285 , e.g., a diffusive screen, to reduce glare or to produce a desired lighting pattern and/or color. 
         [0025]    A heat sink  290  is preferably integrally or removably attached to the lighting module  220  in order to facilitate conduction and/or convection of heat away from the LEDs  250 . The heat sink  290  may have a plurality of fins or other projections that increase its surface area, and it may be supplemented or replaced by an active cooling element (e.g., a fan or a Synjet module available from Nuventix, Inc. of Austin, Tex.). Due to the physical separation between driver module  210  and lighting module  220 , the heat sink  290  is typically neither physically nor thermally connected to the driver module  210 . 
         [0026]    In various embodiments of the present invention, the lighting module  220  also incorporates one or more temperature sensors  295  (e.g., thermistors or other sensors) that sense the operating temperature of the LEDs  250  and/or the ambient temperature within or immediately outside the RCD fixture. Thus, a temperature sensor may be directly thermally coupled to one or more of the LEDs  250 . The sensed temperature may be utilized by the driver module  210  to control lighting module  220 , as described below. 
         [0027]    In other embodiments, one or more sensors  295  may be occupancy and/or ambient-light-level sensors, and lighting module  220  may feature these types of sensors instead of or in addition to the abovementioned temperature sensors. Such sensors  295 , as known to those of skill in the art, detect motion of and/or heat from occupants of the room in which illumination device  200  is installed, and/or the level of ambient light in the room. The output(s) of such sensors  295  may also be utilized by the driver module  210  to control lighting module  220 . For example, the driver module  210  may direct the LEDs  250  to illuminate when the level of ambient light decreases beyond a threshold level and/or when an occupant is detected in the room. Similarly, the driver module  210  may direct the LEDs  250  to dim or turn off entirely when the level of ambient light increases beyond a threshold level and/or when no occupant has been detected for a certain amount of time. 
         [0028]    As shown in  FIG. 2 , the driver module  210  incorporates a connector that connects directly to (e.g., screws or plugs into) electrical socket  150  and receives electrical power (e.g., from the AC mains). The driver module  210  preferably contains electronics that transform such electrical power into a form suitable to drive the LEDs  250  (e.g., DC current). Driver module  210  may also include dimmers, transformers, rectifiers, or ballasts suitable for operation with the LEDs  250 , as understood by those of skill in the art, and such components (and/or any other circuitry) of driver module  210  may be disposed on a printed circuit board. In preferred embodiments, the driver module  210  also provides for thermal feedback (or “foldback”) to protect the LEDs  250 , as described in, e.g., U.S. Pat. No. 7,777,430 and U.S. Patent Application Publication Nos. 2010/0320499, 2010/0176746 (the &#39;6746 application), and 2011/0121760, the entire disclosures of which are incorporated by reference herein. For example, the driver module  210  may utilize the temperature sensed at the lighting module  220  to provide over-temperature protection (i.e., reduction in the power supplied to the LEDs  250 ) and/or switch and control any active cooling system (e.g., a fan) incorporated within lighting module  220  via, e.g., thermal control electronics  297 . The driver module  210  may even incorporate features described in the &#39;6746 application to enable two-wire temperature sensing and, thus, the maintaining of the LEDs  250  within a safe operating temperature range. The driver module  210  also typically provides electrical isolation from the mains power, and is self-contained and may incorporate other features such as a fuse. As shown in  FIG. 2 , power is supplied from the driver module  210  to the lighting module via the electrical cable  230 . 
         [0029]    The terms and expressions employed herein are used as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed.