Abstract:
A lamp assembly manages thermal energy output from solid state lighting elements. An aspect of the present disclosure provides a lamp assembly that achieves enhanced cooling of light elements within the assembly. Enhanced cooling is achieved, in this aspect, by providing a lamp assembly including a heat sink having a plurality of thermo bosses protruding therefrom on a first side, and a plurality of heat sink fins on a second side. A printed circuit board is secured to the first side of the heat sink, and has a plurality of through holes that correspond to the size and locations of the thermo bosses, such that when the printed circuit board is secured to the heat sink, the thermo bosses extend into the through holes.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority from U.S. Provisional Patent Application No. 60/949,459, filed on Jul. 12, 2007, and is a continuation of International Patent Application No. PCT/US08/70022, the entire disclosures of which are incorporated herein by reference in their entirety. 
     
    
     FIELD 
       [0002]    The present disclosure relates to solid state light units, and more specifically, to an LED-based light unit with a heat sink adapted to dissipate heat generated from LED elements. 
       BACKGROUND 
       [0003]    Lighting systems traditionally use various different types of illumination devices, commonly including incandescent lights, fluorescent lights, and, increasingly, solid state illumination devices such as Light Emitting Diode (LED) based lights. LED based lights generally rely on multiple diode elements to produce sufficient light for the needs of the particular light or lighting system. As an approach to offset increasing energy prices and make a meaningful indent to the production of greenhouse gases, solid state lighting offers great promise in this regard. With efficacies approaching 150 lumens per Watt, and lifetimes at over 50,000 Hours, LEDs and lighting products based on LED technology may potentially make significant inroads in the lighting market in residential and commercial, indoor and outdoor applications. 
         [0004]    LED based lights offer significant advantages in efficiency and longevity compared to, for example, incandescent sources, and produce less waste heat than many other types of lighting. For example, if perfect solid-state lighting devices were to be fabricated, the same level of luminance can be achieved by using merely 1/20 of the energy that an equivalent incandescent lighting source requires. LEDs offer greater life than many other lighting sources, such as incandescent lights and compact fluorescents, and contain no environmentally harmful mercury that is present in fluorescent type lights. LED based lights also offer the advantage of instant-on and are not degraded by repeated on-off cycling. Furthermore, LED based lights can withstand more extreme environmental conditions than many other types of lighting products, such as relatively high and low operating temperatures and/or applications having frequent shock or vibration. 
         [0005]    As mentioned above, LED based lights generally rely on multiple LED elements to generate light. An LED element, as is well known in the art, is a small area light source, often with associated optics that shape the radiation pattern and assist in reflection of the output of the LED. LEDs are often used as small indicator lights on electronic devices and increasingly in higher power applications such as flashlights and area lighting. The color of the emitted light depends on the composition and condition of the semiconducting material used to form the junction of the LED, and can be infrared, visible, or ultraviolet. 
         [0006]    Within the visible spectrum, LEDs can be fabricated to produce desired colors. For applications where the LED is to be used in area lighting, a white light output is typically desirable. There are two common ways of producing high intensity white-light LED. One is to first produce individual LEDs that emit three primary colors (red, green, and blue), and then mix all the colors to produce white light. Such products are commonly referred to as multi-colored white LEDs, and sometimes referred to as RGB LEDs. Such multi-colored LEDs generally require sophisticated electro-optical design to control the blend and diffusion of different colors, and this approach has rarely been used to mass produce white LEDs in the industry to date. In principle, this mechanism has a relatively high quantum efficiency in producing white light. 
         [0007]    A second method of producing white LED output is to fabricate a LED of one color, such as a blue LED made of InGaN, and coating the LED with a phosphor coating of a different color to produce white light. One common method to produce such and LED-based lighting element is to encapsulate InGaN blue LEDs inside of a phosphor coated epoxy. A common yellow phosphor material is cerium-doped yttrium aluminum garnet (Ce3+:YAG). Depending on the color of the original LED, phosphors of different colors can also be employed. LEDs fabricated using such techniques are generally referred to as phosphor based white LEDs. Although less costly to manufacture than multi-colored LEDs, phosphor based LEDs have a lower quantum efficiency relative to multi-colored LEDs. Phosphor based LEDs also have phosphor-related degradation issues, in which the output of the LED will degrade over time. Although the phosphor based white LEDs are relatively easier to manufacture, such LEDs are affected by Stokes energy loss, a loss that occurs when shorter wavelength photons (e.g., blue photons) are converted to longer wavelength photons (e.g. white photons). As such, it is often desirable to reduce the amount of phosphor used in such applications, to thereby reduce this energy loss. As a result, LED-based white lights that employ LED elements with such reduced phosphor commonly have a blue color when viewed by an observer. 
         [0008]    Various other types of solid state lighting elements may also be used in various lighting applications. Quantum Dots, for example, are semiconductor nanocrystals that possess unique optical properties. The emission color of quantum dots can be tuned from the visible throughout the infrared spectrum. This allows quantum dot LEDs to create almost any output color. Organic light-emitting diodes (OLEDs) include an emitting layer material that is an organic compound. To function as a semiconductor, the organic emitting material must have conjugated pi bonds. The emitting material can be a small organic molecule in a crystalline phase, or a polymer. Polymer materials can be flexible; such LEDs are known as PLEDs or FLEDs. 
       SUMMARY 
       [0009]    The present disclosure provides a lamp assembly that manages thermal energy output from solid state lighting elements. An aspect of the present disclosure provides a lamp assembly that achieves enhanced cooling of light elements within the assembly. Enhanced cooling is achieved, in this aspect, by providing a lamp assembly including a heat sink having a plurality of thermo bosses protruding therefrom on a first side, and a plurality of heat sink fins on a second side. A printed circuit board is secured to the first side of the heat sink, and has a plurality of through holes that correspond to the size and locations of the thermo bosses, such that when the printed circuit board is secured to the heat sink, the thermo bosses extend into the through holes. 
         [0010]    Light elements are mounted to the printed circuit board such that the through holes are located beneath a substantial portion of the surface area of the light element, thereby allowing the thermo bosses to contact the back side of the light elements to provide an enhanced thermal conductive path between the light elements and the heat sink. The printed circuit board, in one embodiment, is secured to the heat sink by a retaining spring that presses against a ring on one or more LED light elements, and enhanced the contact between the back side of the LED element and the corresponding thermo boss. 
         [0011]    A reflective surface may be in place on the opposite side of the retaining spring that may reflect light to a lens of the light assembly. A power supply may be attached to the housing, and provides power to the PCB and light elements. Such a power supply may be interconnected to an external power supply, and/or may have an internal battery or other power supply that is used to provide power to the PCB and light elements. 
         [0012]    In another aspect, the present disclosure provides a method for managing thermal output of a solid state lamp assembly. In an exemplary embodiment, steps for thermal management include providing a mounting substrate with one or more through holes corresponding to location(s) where solid state light element(s) are mounted to the substrate. A heat sink assembly is coupled to the mounting substrate such that bosses that protract from the heat sink extend into the through hole(s) of the mounting substrate and contact a portion of the solid state light element(s). In one embodiment, the method also includes securing the heat sink to the mounting substrate with a retaining spring. In other embodiments, the method may also include interconnecting optical elements with the lamp assembly, such as reflectors, lenses, and/or diffusers. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a perspective view of a solid state lamp of an exemplary embodiment of the present disclosure; 
           [0014]      FIG. 2  is a top plan view of a solid state lamp of an exemplary embodiment of the present disclosure; 
           [0015]      FIG. 3  is an end plan view of a solid state lamp of an exemplary embodiment of the present disclosure; 
           [0016]      FIG. 4  is a bottom plan view of a solid state lamp of an exemplary embodiment of the present disclosure; 
           [0017]      FIG. 5  is a side plan view of a solid state lamp of an exemplary embodiment of the present disclosure; 
           [0018]      FIG. 6  is a bottom plan view of a solid state lamp of an exemplary embodiment of the present disclosure that a lens element removed; 
           [0019]      FIG. 7  is a cross-sectional view of a solid state lamp of the embodiment of  FIG. 6  along the section  7 - 7 ; 
           [0020]      FIG. 8  is an exploded view of a solid state lamp of an exemplary embodiment of the present disclosure; 
           [0021]      FIG. 9  is a top plan view of a solid state lamp of an exemplary embodiment of the present disclosure; 
           [0022]      FIG. 10  is a cross-sectional view of a solid state lamp of the embodiment of  FIG. 9  along the section  10 - 10 ; 
           [0023]      FIG. 11  is a side plan view of a solid state lamp of another exemplary embodiment of the present disclosure; 
           [0024]      FIG. 12  is a cross-sectional view of a solid state lamp of the embodiment of  FIG. 11  along the section  12 - 12 ; 
           [0025]      FIG. 13  is an end plan view of a solid state lamp of the embodiment of  FIG. 11 ; and 
           [0026]      FIG. 14  is an cross-sectional view of a solid state lamp illustrating exemplary ray paths for an embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0027]    The present disclosure recognizes that providing solid state lamp assemblies, such as LED lamps, is desirable in many situations, and that the presence of multiple LEDs in an assembly can result in heating issues related to LED operation. Such problems have been addressed in the past by using printed circuit boards (PCBs) with metal cores, with an LED mounted to the PCB, and the metal core helping dissipate heat generated from the LED. Such PCBs are relatively expensive, and may still have heating issues related to heat generated from LEDs. The present disclosure provides a thermal path for heat generated by solid state light elements to be dissipated in an efficient manner using a thermo boss interconnected to a heat sink, which contacts at least a portion of the solid state lighting element. The solid state light element is interconnected to a circuit board that includes a through hole aligned to the thermo boss. The heat sink may include fins that radiate heat into ambient air exterior of the lamp assembly. 
         [0028]      FIGS. 1 through 14  illustrate various embodiments of a lamp assembly. With reference first to  FIGS. 1-3 , and  8 , a lamp assembly  20  of an exemplary embodiment is described.  FIG. 1  is a perspective view of the lamp assembly  20 ,  FIG. 2  is a top plan view,  FIG. 3  is an end plan view, and  FIG. 8  is an exploded view of the lamp assembly  20  illustrating various components that are included in the lamp assembly  20  of this embodiment. The lamp assembly  20 , as illustrated, comprises a housing  28  that includes heat sink elements.  24  on each side of the housing  28 , and between flanges  34  on each end of the housing  28 . Heat sink  24  may be further secured by to the housing  28  with a heat sink retainer screw  40  extending through screw aperture  140  and into a screw slot formed into heat sink  24 . The heat sinks  24 , in this embodiment, include a heat dissipating surface that includes heat dissipating fins and a heat collecting surface that includes a number of thermo bosses that protrude from the heat sink  24 . Fins and thermo bosses of heat sinks  24  of this embodiment are described in more detail below. As best illustrated in  FIG. 8 , end caps  32  are attached to flanges  152  on housing  28  by retainer tabs  120  clipping through retainer tab slots  124 . End caps  32  may further secured by end cap retainer screw  44  through a screw aperture on the housing  28 . With reference to  FIGS. 4 and 5 , the lamp assembly  20  includes a lens  48  that is secured to the lamp assembly  20 . Solid state light elements, such as Light Emitting Diodes (LEDs) are located in the interior of the housing  28 , and, when illuminated, provide light through the lens  48 . Lens  48  may include optics that act to diffract, diffuse, or focus the light from the light elements. 
         [0029]    Referring to  FIGS. 6 ,  7 , and  8 , solid state light elements and associated components located on the interior of the housing  28  are now discussed for this exemplary embodiment. Included, in this embodiment, is a printed circuit assemblies  112  (best illustrated in  FIG. 8 ) comprised of printed circuit boards  60  and a plurality of light emitting diodes  52 . The printed circuit boards  60  are attached to heat sinks  24  by means of retaining springs  56  and  180  that are interconnected with the heat sinks  24  and assert pressure against a rings  64  on light emitting diodes  52 . The printed circuit boards  60  include through holes that are aligned adjacent to the light emitting diodes  52 . In this embodiment, the light emitting diodes  52  are interconnected with metal interconnect traces (not shown) on the printed circuit boards that are adjacent to the through holes in the printed circuit boards  60 . The heat sinks  24 , in this embodiment, include thermo bosses  68  that, when aligned with the through holes on the printed circuit boards  60 , extend at least partially into the through holes of the printed circuit boards. When retaining springs  56 ,  180 , are interconnected to the heat sinks  24 , pressure is applied against the LEDs  52  and printed circuit boards  60  to place a bottom side of each LED  52  into contact with an associated thermo boss  68  on the heat sinks  24 . In this manner, the assembly forms a thermal path from light emitting diodes  52  through thermo bosses  68  to the heat sinks  24 . Heat generated through the operation of light emitting diode  52  is conducted through this path and continuing to a plurality of heat sink fins  72  formed on the heat sinks  24 . The fins  72  provide surface area for natural convection to dissipate the heat load generated from the operation of the LEDs  52 . Retaining springs  56 ,  180 , are held in bias by retainer slot  100  on the proximal side and retainer notch  104  on the distal side. Relief slots  184  may be includes that allow mechanical force to normalize across retaining springs  56 ,  180 , for each light emitting diode  52 . A reflective surface may be included on the side of retaining springs  56 ,  180 , interior to the lamp assembly to reflect back scatter from rear surface of lens  48  and any light from LEDs  52 , onto on lens  48 . 
         [0030]    With continuing reference to  FIGS. 6-8 , a power supply  84  is attached to housing  28 , in this embodiment, by power supply retaining screws. Power supply  84  provides power to the printed circuit boards  60  and light emitting diodes  52 . A positive and negative interconnect wire provides power to each of printed circuit boards assembly  112 . Power from an outside source is attached to power supply  84  through power supply input wires  92  routed through input wiring aperture  96  in housing  28  to an outside power source. Outside power source may be any suitable power source, such as commonly available residential, commercial, and industrial alternating current power, and/or direct current power. 
         [0031]    Referring now to  FIGS. 4 ,  7  and  9 - 10 , lens  48 , in this embodiment, is held in lamp assembly  20  by means of lens slot  76  and is captured longitudinally by end caps  32  on each end. Lens  48  is captured and a curve is formed in lens  48  through a curved retainer surface  148  and the curved surface of flanges  152 . The curving of lens  48  provides additional mechanical strength to the lamp assembly  20  and improves light scatter for light that is emitted through the lens. 
         [0032]    Referring to  FIGS. 1 ,  2 ,  5 ,  8  and  11 - 13 , interface bracket  36  provides a point to attach lamp assembly  20  to a mounting surface  156  through a plurality of interface bracket screws  144 . A hinge  160  is formed by catch surface  136  on housing  28  and angled surface  132  interface bracket  36 . Referring to  FIG. 13 , this hinge allows the lamp to hang from the mounting surface  156  at an angle, after interface bracket  36  is mounted, for ease of wiring power supply input wires  92 . Lamp assembly  20  is secured to interface bracket  36  by retainer screws  40 , as previously discussed, through retainer screw aperture  140  on housing  28 . 
         [0033]    With reference now to  FIG. 14 , a lamp angles for a lamp assembly  20  of an embodiment are now described. In this embodiment, a lamp angle  172  of 45 degrees allows an elliptical footprint of light energy across lens  48  rear surface using a typical light dispersion angle  164  of 75 degrees. This elliptical pattern when in conjunction with the plurality of light emitting diodes  52  forms a consistent bright illumination on lens  48 . 
         [0034]    It will be appreciated that, while embodiments of the present disclosure have been illustrated with respect to  FIGS. 1-14 , other embodiments may include fewer, additional, or alternate, components. For example, the lamp assembly may include one or more sensors that determine when an amount of ambient light is below a threshold level, and cause the lamp assembly to power on and provide light. Various embodiments may include one or more controllers, such as a microprocessor or other integrated circuit, that control the output of the lamp assembly and may, for example, cause fewer than all of the LEDs to illuminate based on a set of predefined criteria, such as ambient available light, power input to the lamp assembly (such as through a dimmer switch), or any other of various conditions. Furthermore, the present disclosure provides a method for managing the thermal management of a solid state lamp assembly. Such a method includes providing one or more light elements, a printed circuit board having a plurality of through holes, and a heat sink having a plurality of thermo bosses that are aligned to the through holes when the printed circuit board is placed adjacent to the heat sink. Light elements are mounted to the printed circuit board such that at least a portion of one or more of the light elements cover a through hole. The printed circuit board with attached light elements is placed adjacent to the heat sink such that the thermo bosses of the heat sink extend through the through holes and contact at least a portion of one or more of the light elements. A biasing member may be placed against the printed circuit board and/or light elements to provide pressure against the printed circuit board and/or light elements and place light elements in firm contact with an associated thermo boss. In embodiments where the lamp assembly includes a controller, temperature of the lamp assembly may be monitored and one or more of the light elements may be cycled on and off to reduce the heat generated by the assembly. 
         [0035]    While the instant disclosure has been depicted, described, and is defined by reference to particular exemplary embodiments of the disclosure, such references do not imply a limitation on the disclosure, and no such limitation is to be inferred. The embodiments recited in this disclosure are capable of considerable modification, alteration, and equivalents in form and function, as will occur to those ordinarily skilled in the pertinent arts. The depicted and described embodiments are examples only, and are not exhaustive of the scope of the invention. 
         [0036]    It will be understood by those within the art that each operation and/or component described and/or illustrated herein may be implemented, individually and/or collectively, by a wide range of hardware, software, firmware, or any combination thereof. The foregoing disclosure also describes embodiments including components contained within other components. Such architectures are merely examples, and many other architectures can be implemented to achieve the same functionality.