Abstract:
An LED lamp module designed to be easily retrofitted into existing incandescent based light fixtures with minimum modification is provided. The LED lamp module includes a generally circular metal core board including a first surface and a second surface; at least one LED disposed centrally on the first surface of the metal core board; and a flat annular printed circuit board including a current driver circuit for powering the at least one LED, the annular printed circuit board being disposed around the at least one LED and electrically coupled to the at least one LED, wherein the second surface of the metal core board is configured to contact a host fixture and heat generated by the at least one LED is conducted to the host fixture. The LED lamp module uses the host light fixture as a heat sink to transfer and dissipate heat to the external environment.

Description:
PRIORITY 
   This application claims priority to an application entitled “LED LAMP MODULE” filed in the United States Patent and Trademark Office on Feb. 21, 2006 and assigned Ser. No. 60/775,268, the contents of which are hereby incorporated by reference. 

   BACKGROUND 
   1. Field 
   The present disclosure relates generally to light bulb and lamp assemblies, and more particularly, to a light emitting diode (LED) lamp module configured to replicate the light output of a conventional incandescent light bulb. 
   2. Description of the Related Art 
   Incandescent light bulbs are used in a large variety of lighting products. Although inexpensive to purchase, incandescent light bulbs have several drawbacks. First, incandescent light bulbs use a relatively large amount of power compared to other lighting products which increase energy costs. Second, incandescent light bulbs have a short life causing repetitive replacement costs. Furthermore, since theses bulbs have a short life, labor costs will subsequently be effected by having maintenance personnel constantly replace the bulbs. 
   Recently, a trend in the lighting industry is to develop light emitting diode (LED) light modules that can be easily adapted to current light fixture products. LED technology offers more than twice the energy efficiency of traditional incandescent bulbs and has 20-30 times the reliability. A great deal of investment goes into the light fixture industrial design itself (e.g., housing, lens, etc.) and there is a great cost and time-to-market advantage in having modules that permit rapid conversion to LEDs. 
   Thus, a need exists for an LED lighting product having low power consumption and long life. Furthermore, a need exists for an LED lighting product to produce the same light output as a conventional incandescent bulb and have a similar form factor to the conventional lighting product to facilitate conversion. 
   SUMMARY 
   An LED lamp module designed to be easily retrofitted into existing incandescent based light fixtures with minimum modification is provided. The LED lamp module of the present disclosure permits lighting fixture manufacturers or end-user customers to realize the benefits of LED technology, e.g., more energy efficient and longer life than incandescent, while minimizing the impact to current light fixture designs. 
   The LED lamp module of the present discourse may be employed in place of a standard incandescent bulb via a plurality of connection means, e.g., hardwired or socket such as bi-pin, screw-in, etc. It is designed to accept the same power input and waveforms as the existing light fixtures (e.g. 10-30 VDC). The LED lamp module uses the host light fixture as a heat sink to transfer and dissipate heat to the external environment. Furthermore, the LED lamp module also works in conjunction with existing host fixture front lenses and reflectors with no or minimum modification. 
   According to one aspect of the present disclosure, an LED lamp module includes a generally circular metal core board including a first surface and a second surface; at least one LED disposed centrally on the first surface of the metal core board; and a flat annular printed circuit board including a current driver circuit for powering the at least one LED, the annular printed circuit board being disposed around the at least one LED and electrically coupled to the at least one LED, wherein the second surface of the metal core board is configured to contact a host fixture and heat generated by the at least one LED is conducted to the host fixture. The LED lamp module uses the host light fixture as a heat sink to transfer and dissipate heat to the external environment. 
   According to another embodiment, a lighting assembly is provided. The lighting assembly includes a host fixture including a generally cylindrical base configured to support a lighting module and a generally cylindrical cover including a parabolic reflector extending inside the cover from a first end of the cover to a second end of the cover, the reflector terminating in an annular rim; and the lighting module including a generally circular metal core board including a first surface and a second surface, the second surface being configured to contact the base of the host fixture, at least one LED disposed centrally on the first surface of the metal core board and a flat annular printed circuit board including a current driver circuit for powering the at least one LED, the annular printed circuit board being disposed around the at least one LED and electrically coupled to the at least one LED, wherein heat generated by the at least one LED is conducted to the host fixture. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other aspects, features, and advantages of the present disclosure will become more apparent in light of the following detailed description when taken in conjunction with the accompanying drawings in which: 
       FIG. 1  is perspective view of a LED lamp module in accordance with an embodiment of the present disclosure; 
       FIG. 2  is top view of an annular-shaped integrated electronics current driver board of the LED lamp module shown in  FIG. 1 ; 
       FIG. 2A  is a schematic diagram of a current driver circuit in accordance with the present disclosure; 
       FIG. 3  is a top plan view of a LED board according to an embodiment of the present disclosure; 
       FIG. 4  is a top plan view of the LED board shown in  FIG. 3  with an LED and optical element mounted thereon; 
       FIG. 5  is a top view of the current driver board coupled to the LED board; 
       FIG. 6  is an exploded view of the LED lamp module employed with a conventional lighting fixture housing; 
       FIG. 7  is a cross sectional view of the LED lamp module mounted in the housing of  FIG. 6 ; 
       FIG. 8  is a perspective view of a lighting fixture employing the LED light module of the present disclosure; and 
       FIG. 9  is an exploded view of the lighting fixture shown in  FIG. 8 . 
   

   DETAILED DESCRIPTION 
   Preferred embodiments of the present disclosure will be described hereinbelow with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail to avoid obscuring the invention in unnecessary detail. Throughout the drawings, like reference numerals represent like elements. 
   A light emitting diode (LED) lamp module  10  is provided as shown in  FIG. 1 . The LED lamp module  10  is composed of a metal core LED board  18  with an attached secondary optical element  14  and an electronics (“donut”) board  16  that mechanically attaches to the LED board  18  with two screws/standoffs  38 . The primary light source is a high power LED  12 . An exemplary LED is a Luxeon III, three watt light emitting diode commercially available from Lumileds Lighting, U.S., LLC of San Jose, Calif. 
   Referring to  FIG. 1 , the compact LED lamp module  10  in accordance with the present disclosure employs a single LED device  12  to produce an amount of light comparable to a 10 Watt incandescent (e.g., Halogen) bulb. The LED lamp module  10  generates approximately 80 lumens of white light but also may be configured for red, green, blue and other color variations depending on the LED device employed. In one embodiment, the LED lamp module  10  uses a secondary optical element  14  to efficiently collimate that light emitting from the LED  12  to emit the light in the direction the light is intended to be used. When used in combination with a host fixture&#39;s existing reflector and front lens, the aesthetic appearance of the light emitted looks similar to the incandescent version. 
   Referring to  FIG. 2 , an integrated electronics current driver board  16  provides constant current to the LED device  12  over the full design input voltage range of 10-30VDC. The driver board  16  consumes less than 4 Watts of power to produce approximately the same amount of light output as the conventional 10Watt bulb that it replaces. The LED lamp module  10  is a direct replacement for the incandescent light assembly. The electronic driver design, shown in  FIG. 2A , allows the LED light output to remain constant over the entire voltage range. The integrated electronics uses a switching regulator to efficiently convert (75% or greater) the input energy to the form required of the LED  12 . The electronic driver design also provides transient protection (to guard against input power fluctuations) and EMI (electromagnetic interference) filtering to prevent interference with other electrical equipment in the vicinity of the light fixture. An optional dimming feature via dimming circuit  19  is provided so that the operator can adjust the light level as desired. 
   The electronics board  16  is designed in a “donut” or annular form factor to “piggyback” on top of the LED board  18  and around the host fixture&#39;s reflector, as will be described below in relation to  FIGS. 6 and 7 , to maximize compactness, space efficiency so that no, or minimal, mechanical changes are required to the host fixture. As can be seen in  FIGS. 1 and 7 , the electronics board  16  is substantially the same size as the LED board  18 , i.e., have substantially the same size diameter and circumference. 
   A schematic diagram of the current driver board is illustrated in  FIG. 2A . The electronic board  16  employs a switching regulator approach (e.g., Supertex HV9910 as indicated in  FIG. 2A  as U 1 ) to efficiently convert input power to that required of the LED  12 , e.g., D 1 . The electronic design provides input power transient protection, e.g., via Z 1 , so that power fluctuations will not damage the circuit. A current driver design is used to provide constant current (typically 700 ma) to the LED, independent of the voltage (10-30VDC). EMI filtering components are provided (e.g., C 1 , C 2 , T 1 , L 2  and L 3  as indicated on  FIG. 2A ) to keep noise generated within the electronics board from traveling along the power leads P 1  and P 2 , as shown in  FIGS. 2 and 5 , to the LED board  18 . 
   The dimming feature is controlled by a potentiometer  17  either attached to, or remote from, the host light fixture and terminal to the dimming circuit  19  at terminals P 6  and P 7  as shown in  FIG. 2A . The potentiometer  17  and dimming circuit  19  provides a variable analog voltage to an input on the switching regulator U 1 . The switching regulator U 1  interprets this voltage level and reduces the current provided to the LED D 1  accordingly to dim the light output. 
   The nature of the LED semiconductor device and the supporting electronics will provide a mean time between failure of greater than 50,000 hours, more than 25 times that of the incandescent bulb it replaces. To ensure long life, the LED junction temperature must be maintained below 125 degrees C. This is accomplished by mounting the LED  12  on a metal core printed circuit board (PCB)  18 . The PCB  18  is directly mounted to the metal host light fixture to transfer the heat to the fixture and then to the ambient environment through radiation and convection methods. This technique eliminates the need for any other special heat sinking device. 
   Referring to  FIGS. 3-5 , the LED board  18  includes a first, top surface  13  and a second, bottom surface  15  and is circular in shape. Generally, the LED board is small in diameter and is configured to easily mount within an existing spotlight or reading light type fixture. As can be seen in  FIGS. 1 ,  5  and  7 , the LED board  18  is configured to be substantially the same size as the electronics board  16 . The LED board  18  has four threaded holes  20  which are used to attach the LED lamp module  10  to the host fixture. There are two other holes  22  in the center of the LED board  18  to channel power leads through the base of the host fixture to the electronics board  16 . Two additional threaded holes  24  are provided to mount the electronics boards  16 . The LED board  18  has an aluminum backing  21 , or coating on the second bottom surface, that mates with the host fixture  26  to transfer heat from the LED  12 , as shown more clearly in  FIG. 7 . 
   The LED  12  is mounted to the first surface  13  of the LED board  18  and the secondary optical element  14  is placed (e.g., epoxied) over the LED  12 . An exemplary optical element is an L 2  Optics Series Lens commercially available from Lumidrives of Knaresborough, UK. This optical element efficiently captures (75% or greater) the light exiting the LED device  12  and directs it toward its intended target. The optical element  14  will create a spot with a total angle of 5, 10 or 25 degrees, depending on the properties of the lens selected. This optical system is designed to fit within the host system front reflector and lens with no, or minimal modification, as will be described in relation to  FIGS. 6 and 7 . 
   Referring to  FIGS. 6 and 7 , a host lighting fixture  26  for supporting the LED lamp module  10  is illustrated. The fixture  26  will include a generally cylindrical cover  28  and generally cylindrical base  30  which are mated together, in one embodiment, with a screw-type connection. The base will include a bottom portion  35  and surrounding side wall  37  to support the LED lamp module  10 . The cover  28  will include a parabolic reflector  32  extending inside the cover from a first end of the cover to a second end of the cover. The reflector  32  will terminate in an annular rim  33 . Furthermore, the cover  28  will include a front window lens  34 . The front window lens  34  may be clear plastic or glass, but will optionally have a diffusing surface or prismatic lens structure to diffuse the light, widen the pattern and contribute to the aesthetic look of the front of the fixture  26 . Light emanating from the optical element  14  will then pass through the front lens  34 . Some light will also reflect back from the front lens, back to the reflector  32 , before being transmitted back out the front lens. This effect provides the aesthetic affect of broadening the perceived light pattern width when looking into the light fixture as illustrated in  FIG. 8 . 
   The electronics board  16  is “donut” or annular shaped having an inner circumference  37  and outer circumference  39 . The annular board  16  is configured to mount on top of the LED board  18  and around the optical element  14 , while also allowing clearance for the reflector  32  of the host fixture  26  (see  FIG. 7 ). As can be seen in  FIGS. 6 and 7 , the electronics board  16  and  18  are of substantially the same size. Furthermore, the inner circumference  37  of the electronics board  16  is greater than an outer circumference of the optical element  14  allowing the optical element  14  to pass therethrough. In other embodiments, the optical element  14  is not employed and the reflector is configured to extend down closer to the LED  12 . The rim of the reflector will extend into the inner circumference of the electronics board  16  and come into close proximity of the LED  12 . 
   The electronics board  18  is mounted to the LED board  16  by standoffs  38  which prevent the circuitry of the electronics board  16  from coming into contact with the LED board  18 . The standoffs  38  are made form an electrically conductive and thermally conductive material. Heat generated by the circuitry of the electronics board will be conducted via the standoffs  38  to the LED board  18  and subsequently to the host fixture. The overall electronics design is very compact to fit within the available space, having no additional impact on the host fixture. 
   The electronics board  16  is grounded to the host light fixture housing  26  via screws and/or standoffs  38  that mates the electronics board  16  to the LED board  18 , and then, the LED board  18  is grounded to the host light fixture  26  by mounting screws  40 . It is to be appreciated that the screws and/or standoffs are made from an electrically conductive material. This design allows the host fixture metallic housing  26  to act as a Faraday shield for suppression of radiated EMI. The LED board  18  and electronics board  16  are electrically connected as shown in  FIG. 5  to drive the LED  12 . Two additional wires  36  bring power from the base  30  of the host fixture to the electronics board. 
   The fully assembled LED lamp module  10  is connected to the host light fixture  26  using four screws  40  as show in  FIG. 9 . 
   The design of the LED lamp module  10  of the present disclosure facilities heat dissipation away from the LED  12  which ensures long life of the LED. This is done by mounting the LED  12  on the metal backed printed circuit board (PBC)  18  which conducts the heat generated by the LED  12  away from the LED  12 , through the metal backed PCB  18  to the host light fixture  26 . The second surface  15  of the LED board  18  is configured to being in substantial contact with the bottom portion  35  of the host fixture&#39;s base  30  to allow heat generated by the LED  12  to be conducted through the backing  21  of the LED board  18  to the host fixture  26 . The metal backed PCB  18  is also the mounting mechanism to the host fixture that is secured with  4  screws along with a layer of thermally conductive material to improve the heat transfer from the metal backed PCB  18  to the host fixture  26 . This thermal management system then transfers the heat from the host fixture to the ambient environment through primarily convection. By keep the junction temperature of the LED below its design maximum value, its long service life is ensured. 
   While the disclosure has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the disclosure.