The present disclosure generally relates to illumination devices and, more particularly, to light emitting diode (“LED”) based illumination devices.
Most lighting applications utilize incandescent or gas-filled bulbs, particularly lighting applications that require more than a low level of illumination. Incandescent bulbs typically do not have long operating lifetimes and thus require frequent replacement. Gas-filled tubes, such as fluorescent or neon tubes, may have longer lifetimes, but operating using dangerously high voltages, are relatively expensive and include hazardous materials such as mercury. Further, both bulbs and gas-filled tubes consume substantial amounts of power.
In contrast, LEDs are relatively inexpensive, operate at low voltage, and have long operating lifetimes. Additionally, LEDs consume relatively little power, are compact, and do not include toxic substances. These attributes make LEDs particularly desirable and well suited for many applications.
Although it is known that the brightness of the light emitted by an LED can be increased by increasing the electrical current supplied to the LED, increased current also increases the junction temperature of the LED. Excessive heat reduces the efficiency and lifetime of the LED. Advances in LED technology have brought increasingly bright LEDs. However, such increased brightness is accompanied by increased heat generation.
Consequently, there exist a need for a solution for dissipating and otherwise transferring heat generated by the LEDs and their associated circuitry away from the LEDs themselves to increase the efficiency and lifetime of such products.
The invention will be more readily understood in view of the following description when accompanied by the below figures and wherein like reference numerals represent like elements.
Briefly stated, the present disclosure is directed to a reflector cover for use in connection with a light emitting diode (“LED”) illumination device and an LED illumination device that includes at least a reflector cover and circuit board.
In accordance with one embodiment of the present disclosure, the reflector cover includes an open air reflector having a reflector base. The LED illumination device includes a circuit board having an LED package coupled thereto. The immediate perimeter of the LED package defines a connectivity region that includes an electrical connectivity region and a thermal connectivity region. The LED package is mechanically and electrically coupled to the electrical connectivity region and mounted atop or in the vicinity of the thermal connectivity region.
The electrical connectivity region permits the actual mechanical coupling of the LED package to the circuit board and also functions as the live portion for electron flow to the cathodes and anodes of the LED package. The thermal connectivity region, often known as the head pad or slug, is made of copper or any other suitable material that is capable of supporting thermal heat transfer. Within in the thermal connectivity region are disposed a plurality of thermal vias that extend from the top portion of the circuit board to the bottom portion of the circuit board. In operation, the thermal vias transfer heat from the LED side of the thermal connectivity region to the opposite side of the board
The reflector base is dimensioned to cover at least a portion of the thermal connectivity region thereby defining a pressure zone. The reflector cover is capable of being mechanically coupled to the circuit board such that the reflector base applies pressure to the pressure zone.
In one embodiment, the reflector cover further includes a reflector fastener housing rigidly coupled to the reflector. The reflector cover is capable of being mechanically coupled to the circuit board by mechanically coupling the reflector fastener housing to the circuit board with a fastener such as a screw.
The present disclosure is further directed to an LED illumination device that includes both a reflector cover and the circuit board as generally described above. The LED illumination device further includes a reflector fastener housing rigidly coupled to the open air reflector and a fastener such as a screw. The reflector cover is mechanically coupled to the circuit board by mechanically coupling the reflector fastener housing to the circuit board with the fastener.
The present disclosure is further directed to an LED illumination device that includes a substantially rigid reflector cover comprising a plurality of open air reflectors and a plurality of reflector fastener housings. Each open air reflector of the plurality of open air reflectors includes a reflector base. Each reflector fastener housing of the plurality of reflector fastener housings defines a reflector fastener aperture. The LED illumination device includes a circuit board having a plurality of LED packages coupled thereto. The circuit board further includes a plurality of circuit board fastener apertures disposed within the circuit board.
Each LED package of the plurality of LED packages includes an LED and an LED substrate. The immediate perimeter of the LED package defines a connectivity region as generally described above. The reflector base of each open air reflector of the plurality of open air reflectors is dimensioned to cover at least a portion of the thermal connectivity region thereby defining a pressure zone. The reflector cover is capable of being mechanically coupled to the circuit board such that the reflector bases apply pressure to the pressure zones.
The LED illumination device further includes a mounting bracket comprising a plurality of fastener receptacles. Fasteners such as screws are utilized to couple the reflector cover to the circuit board and to couple the circuit board to the mounting bracket such that each open air reflector of the plurality of open air reflectors applies pressure to a corresponding pressure zone. In particular, individual fasteners are utilized to engage a corresponding reflector fastener aperture of the plurality of reflector fastener apertures, a corresponding circuit board fastener aperture of the plurality of circuit board fastener apertures and a corresponding fastener receptacle of the plurality of fastener receptacles.
In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding the present disclosure. It will be apparent to one of ordinary skill in the art, however, that these specific details need not be used to practice the present disclosure. In other instances, well-known structures, interfaces and processes have not been shown or described in detail in order to avoid obscuring the instant disclosure.
With reference to
As discussed in more detail below, reflector cover 101 is for use in connection with a light emitting diode (“LED”) illumination device. Reflector cover 101 includes one or more open air reflectors 102 and one or more reflector fastener housings 104. Each open air reflector 102 is rigidly coupled to either another reflector 102 or to a reflector fastener housing 104. In one embodiment, rigid connecting members 106 rigidly couple the open air reflectors 102 to the reflector fastener housings 104, thereby forming the reflector cover 101.
Each open air reflector 102 includes at least one wall 202 that defines a reflector aperture 204. The walls 202 have a thickness associated therewith, thereby establishing a reflector base 302. In one embodiment, the thickness of the walls 202 of each reflector 102 vary such that the thickness of the walls 202 is greater at the reflector base 302 than at the top of the reflector 102 (i.e., at the top of
In one embodiment, the open air reflectors 102 include four side walls 202, forming a parallelogram when viewed from the top as illustrated in
Each of the plurality of reflector fastener housings 104 define a reflector fastener housing aperture 208. In one embodiment, the reflector fastener housings 104 are cylindrical housings. Other shapes, however, are contemplated by the present disclosure. The reflector fastener housings 104 also have a base 304. In one embodiment, the reflector fastener housing bases 304 are on a separate, but parallel plane as the reflector bases 302. In particular, reflector bases 302 are on a lower plane than the reflector fastener housing bases 304 (i.e., the reflector bases 302 extend past the reflector fastener housing bases 304 when the reflector cover 101 is viewed from the side as illustrated in
As explained in more detail below, the reflector fastener housings 104 function to permit the reflector cover 101 to be mechanically fastened to a circuit board and mounting bracket. The reflector fastener housing 104 also function to center or align the open air reflectors 102 to LEDs 602 (see
In one embodiment, each of the open air reflectors 102, the reflector fastener housings 104 and the rigid connecting member 106 have top portions that are on the same plane (i.e., the top portions of the open air reflectors 102, the reflector fastener housings 104 and the rigid connecting member 106 are at the same height). As previously noted, the reflector bases 302 may extend beyond the reflector fastener housing bases 304. In one embodiment, the rigid connecting members 106 may be of height that is more shallow than the reflector fastener housing bases 304 when viewed from the side and illustrated in
Reflector cover 101, in one embodiment, is made of plastic. The plastic may be coated or painted in a reflective material to permit light from an LED to reflect off the interior walls 202 of the reflectors 102. In one embodiment, the reflector cover 101 is substantially rigid so that suitably resists being deformed. As is recognized, the reflector cover 101 is capable of being deformed under suitable conditions as described below.
Reflector cover 101 is designed to be used in connection with a circuit board such as the printed circuit board (“PCB”) illustrated in
The electrical connectivity region permits the actual mechanical coupling of the LED package 603 to the PCB 601 and also functions as the live portion for electron flow to the cathodes and anodes of the LED package 603. The thermal connectivity region, often known as the head pad or slug, is made of copper or any other suitable material that is capable of supporting thermal heat transfer. Within in the thermal connectivity region are disposed a plurality of thermal vias that extend from the top portion of the PCB 601 to the bottom portion of the PCB 601. In operation, the thermal vias transfer heat from the LED side of the thermal connectivity region to the opposite side of the PCB 601. (See
The reflector base 102 is dimensioned to cover at least a portion of the thermal connectivity region portion of the connectivity region 608, thereby defining a pressure zone. The reflector cover is capable of being mechanically coupled to the circuit board such that the reflector base applies pressure to the pressure zone.
In one embodiment, the reflector bases 302 are dimensioned to cover at least a portion of the pressure zone when the reflector cover 101 is mechanically coupled to the circuit board 601. When the reflector cover 101 is mechanically coupled to the circuit board 601, as discussed below, each reflector 102 corresponds to a corresponding LED package 603. Reflectors 102 are open air reflectors that concentrate the volume of the light produced by LEDs 602 while allowing exposure of the LEDs 602 to the atmosphere. As such, reflectors 102 are not traditional optics that have a cover dimensioned to cover the LEDs 602. While such traditional optics are capable of distorting the light produced by an LED and protect the LED from external elements, they do not permit the dissipation of heat from an LED (such as LED 602) into the atmosphere.
As noted above, the thermal connectivity region and the pressure zones include a plurality of thermal vias that are formed within the circuit board 601 and that connect the top surface of the circuit board 601 to the bottom surface of the circuit board 601. Thermal vias (also known as heat pipes) may include hollow, cylindrical copper pipes and function to transfer heat from one side of the circuit board 601 to the other side of the circuit board 601.
In accordance with one embodiment of the disclosure,
The mounting bracket 901 includes a plurality of heat sinking fins 906 coupled to the bottom side of the top surface 902. Heat sinking fins 906 are preferably exposed to the atmosphere to enable heat to readily dissipate from the fins 906 into the atmosphere.
The mounting bracket 901 includes a plurality of fastener receptacles 903 disposed therein (e.g., disposed within the top surface 902). In one embodiment, the number of fastener receptacles 903 is equal in number to the number of circuit board fastener apertures 610 and the number of reflector fastener housings 104. The location of the fastener receptacles 903 corresponds to the relative locations of the circuit board fastener apertures 610 and reflector fastener apertures 208. The fastener receptacles 903 are dimensioned to engage and secure a fastener (not shown). In one embodiment, the fastener receptacles 903 are threaded.
Exemplary mounting bracket 901 may further include mounting bracket apertures 910 that are disposed within the outside edges of the bottom surface 904 of mounting bracket 901. The mounting bracket apertures 910 are dimensioned to accept a fastener (not shown) such as a screw that engages the mounting bracket aperture 910 and is therefore capable of coupling or fastening the mounting bracket 901 to another surface (not shown). In one embodiment, the mounting bracket 901 may further include corresponding surface relief portions 908 disposed within the outside edges of the top surface 902 to permit a user access to the mounting bracket apertures 901 (e.g., with a screw driver or other tool).
Other shapes of the mounting bracket 901 are contemplated. Indeed, a one-dimensional (i.e., existing in a single plane) mounting bracket may be used in place of the three-dimensional (i.e., existing in multiple planes), triangular-shaped mounting bracket 901. Similarly, other triangular-shaped mounting bracket may be utilized having a different angle of the top surface relative to the bottom surface. Mounting bracket 901 is made of metal or other suitable material capable of supporting the weight of the LED illumination device and capable of pulling heat away from the LED illumination device and dissipating such heat into the environment.
As used herein, “mounting bracket” includes any bracket, heat sink device or heat or thermal transfer plate. The above-described and illustrated mounting bracket 901 is merely exemplary and is not intended to be limiting on the present disclosure.
With reference to
With further reference to
As illustrated, the reflector cover 101 is capable of being mechanically coupled to the circuit board 601 and to the mounting bracket 901. In particular, a plurality of mechanical fasteners (not shown) may be used to engage a reflector fastener aperture 208, a corresponding circuit board fastener aperture 610 and a corresponding fastener receptacle 903 (see dotted lines in
As a result of the foregoing, results have shown that it is possible to obtain less than a 2 degree Fahrenheit change from the top of the circuit board 601 (i.e., at the thermal connectivity region 1712) to the contact point on the mounting plate 901. By having such a small difference in temperature, thermal transfer is optimized between the LED package 603, the PCB 601 and the mounting plate 901.
An even-pressure distribution LED illumination device is contemplated in accordance with the present disclosure recognizes at least three benefits over the prior art: (1) the pressure applied to the plurality of vias 1704 creates a high rate of thermal transfer from the LED package 603 through the PCB 601 to the mounting bracket 901 (and plurality of heat sink fins 906); (2) using a reflector 102 that surrounds the LED package 603 results in a large pressure zone that not only supports a high rate of thermal transfer through the vias, but also more heat transfer at any given point in time; and (3) the open air reflectors permit the LED packages 603 to dissipate heat to the atmosphere simultaneously with the heat transfer to the mounting bracket 901 through the plurality of heat vias 1704. As such, the disclosure permits heat dissipation on both sides of the circuit board 601.
The foregoing benefits are substantial as compared to conventional LED illumination devices that use closed optics mounted to the top of a circuit board. In such conventional devices, the heat generated by the LED packages is only permitted to be pulled to the back of the circuit to a heat plate. Moreover, such conventional devices offer little or no compression of the circuit board. At best, the conventional prior art provided pressure where the optics cover attached to the circuit board, which generally corresponded to the periphery of the device (i.e., where heat dissipation is not needed) instead of the periphery of each LED package 603 The current disclosure overcomes each of these limitations by providing the foregoing even pressure distribution LED illumination device.
Other advantages will be recognized by one having ordinary skill in the art. It will also be recognized that the above description describes mere examples and that other embodiments are envisioned and covered by the appended claims. For example, it is contemplated that different patterns of reflector covers may be used to correspond to numerous different patterns of LED circuits.