Patent Grant
7997763
1. Field of Invention
The present invention relates to a lighting device and, more particularly, to a high-power light emitting diode (LED) lighting device with enhanced thermal management and a method of fabricating the same.
2. Description of Related Art
One of the key advantages of LED-based lighting is that it exhibits a higher efficiency in terms of light output per unit power input as compared to traditional incandescent lighting. Moreover, recent advances in LED-based lighting technology now make it possible for LED-based lighting to exhibit higher efficiency in such terms than standard fluorescent lighting. LED-based lighting is also less prone to damage due to vibration and has a longer service life.
Generally speaking, high-power LED's are required for general lighting applications. In the present specification and in the accompanying claims, the phrase “high-power LED” means an LED that is capable of continuous use at greater than or equal to one watt (≧1 W) of electrical power. It is often necessary to use two or more high-power LED's in an array to provide the desired light output.
The use of high-power LED's presents a problem. Unlike incandescent lighting sources, which radiate much of their energy as heat and are thus capable of operating at high temperatures, high-power LED's need to operate within a relatively narrow temperature range. And, because high-power LED's do not have perfect light-emission efficiency in converting electrical energy to light energy, some of the supplied electrical power is converted into heat. This heat, if not properly dissipated, can increase the operating temperature of the high-power LED, which can significantly alter and/or permanently degrade the operating characteristics of the high-power LED. There are four critical characteristics of a high-power LED that are affected by its operating temperature:
While the effects of improperly managed operating temperatures on the first two critical characteristics of a high-power LED are generally considered to be temporary, the last two critical characteristics affected by improperly managed operating temperatures are permanent. Thus, it is essential to dissipate heat from high-power LED lighting devices.
The present invention is directed to a high-power LED lighting device with enhanced thermal management and a method of installing the same. A lighting device according to the invention comprises a housing and a heat sink assembly received within the housing. The heat sink assembly comprises at least a first heat sink member and at least a second heat sink member. A printed circuit board is mounted to both of the first heat sink member and the second heat sink member. At least one high-power LED is provided on the printed circuit board. The lighting device according to the invention further comprises at least one and preferably a plurality of biasing members that bias an outer side of the first heat sink member and an outer side of the second heat sink member into contact with an inner side of the housing. Heat from the high-power LED is transferred through the heat sink assembly to the housing, where it is dissipated into the air.
The present invention also provides a method for manufacturing a lighting device according to the invention. The method comprises:
The foregoing and other features of the invention are hereinafter more fully described and particularly pointed out in the claims, the following description setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principles of the present invention may be employed.
With reference to
Preferably, the lighting device further comprises an optic 140 mounted to the printed circuit board 60 for the at least one high-power LED 90. An optic 140 can be used to shape or direct the beam of light emitted from the at least one high-power LED 90.
The lighting device 10 preferably further comprises a lens 150. The lens 150 is operatively associated with the housing 20 and covers the at least one high-power LED 90. The lens 150 protects the printed circuit board 60 and other components within the housing 20 from dust and debris. The lens 150 can optionally be reinforced by a metal cage, if desired, or as may be required for use in specific applications.
With reference to
In an alternate configuration shown in
It will be appreciated that the first and second heat sink members 40, 50, do not need to be aligned on or with respect to pins or fasteners 200. Alternatively, a feature such as a groove or ledge could be formed on the inner side of the housing, which would align with a flange or rib extending from the heat sink members. The biasing member 100 would thus press the outer sides 110, 120 of the first and second heat sink members 40, 50 into contact with the inner side 130 of the housing 20, with the aligned groove and flange maintaining the orientation of the heat sink members and housing. The opposite configuration is also possible (i.e., the heat sink members are provided with a groove or ledge, and the inner side of the housing is provided with a flange or rib).
It will be appreciated that the adapter plate 190 is optional, and that the pins or fasteners 200 on which the first and second heat sink members 40, 50 are pivotally or slidably arranged could be installed in or integrally formed as part of the housing 20. Further optional components can include, for example, one or more alignment plates, which can assist in properly aligning the first and second heat sink members 40, 50 within the housing 20.
In the embodiment shown in
In the preferred embodiment of the invention, the first heat sink member 40 and the second heat sink member 50 are formed of a thermally conductive material such as aluminum, which can be cast, extruded or machined. The outer sides 110, 120 are adapted to contact the inner side of the housing, when the first and second heat sink members 40, 50 are in a biased condition. Heat from the at least one high-power LED 90 provided on the printed circuit board 60 is thus able to migrate through the heat sink assembly 30 from the connecting portion 70, 80 of the first and second heat sink members 40, 50 to the outer sides 110, 120 and then to the housing 20 in contact therewith, where it is dissipated into the air. This allows the at least one high-power LED 90 to operate at the desired thermal temperature range, which limits color shift and minimizes temporary and permanent reductions in light output and efficiency. It will be appreciated that the outer sides 110, 120 of the first and second heat sink members 40, 50 may be “fluted” or “finned” such as depicted in
Thermal interface material (“TIM”) can be applied to the sides of the first and second heat sink members 40, 50 and/or to the inner side 130 of the housing 20 to increase thermal transfer efficiency between the first and second heat sink members 40, 50 and the housing 20. Furthermore, TIM can be applied between the printed circuit board 60 and the connecting portions 70, 80 of the first and second heat sink members 40, 50, respectively, to improve thermal transfer efficiency between the printed circuit board 60 and the first and second heat sink members 40, 50. Any TIM can be used including, but not limited to, thermal greases, oils, phase change materials and films.
In the embodiments of the invention illustrated in
It will be appreciated that other types of biasing members 100 can be used instead of slotted spring pins 250, 290. For example and with reference to
In the illustrated embodiment of the invention, two biasing members of the same size are utilized. It should be appreciated that two or more biasing members, each having a different size and/or type, could be utilized. Similarly, the grooves within which such biasing members are received could also be of different size and/or configuration. It will also be appreciated that the heat sink assembly could comprise more than two heat sink members and more than two biasing members, if desired (e.g., three heat sink members and three biasing members).
In another aspect, the present invention provides a method for manufacturing a lighting device. The method comprises:
The first and second heat sink members could be pivotally or slidably secured to an adapter plate, which is inserted with the first and second heat sink members and secured to the housing. Alternatively, the first and second heat sink members could be pivotally or slidably engaged with pins or fasteners extending from the housing.
Electrical connections can be made between the printed circuit board and the DC output side of the AC to DC driver using wires or harnesses extend from one or both thereof. The AC to DC driver can be secured to an inner side of one of the first heat sink member or the second heat sink member using fasteners.
Once the heat sink assembly has been biased against the housing, and the printed circuit board has been secured to the connecting portion of the heat sink assembly, an optic can be fastened to the printed circuit board using fasteners. It will be appreciated that depending upon the configuration of the optic, it may be possible to connect the optic to the printed circuit board before the printed circuit board is secured to the connecting portion of the first and second heat sink members. A lens is then preferably operatively associated with the housing for covering the at least one high-power LED. The lens can be reinforced with a metal cage, if desired.
The entire assembled unit can then be shipped to an installation site. The installer does not disconnect the lens from the housing, but merely electrically connects AC power from an AC power source to the input side of the AC to DC driver. When the lighting device fails, it is simply replaced with a new lighting device. The lighting device that failed can be returned to the factory to be reconditioned and returned to service, if desired.
Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and illustrative examples shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.
| Number | Name | Date | Kind |
|---|---|---|---|
| 5219221 | Yamaka et al. | Jun 1993 | A |
| 7748876 | Zhang et al. | Jul 2010 | B2 |
| 7758214 | Lee et al. | Jul 2010 | B2 |
| 7874702 | Shuai et al. | Jan 2011 | B2 |
| Number | Date | Country | |
|---|---|---|---|
| 20100246178 A1 | Sep 2010 | US |
