1. Field
The present disclosure relates generally to light-emitting diode (LED) bulbs, and more specifically to using a laminate structure for mounting LEDS in a liquid-filled LED bulb.
2. Description of Related Art
Traditionally, lighting has been generated using fluorescent and incandescent light bulbs. While both types of light bulbs have been reliably used, each suffers from certain drawbacks. For instance, incandescent bulbs tend to be inefficient, using only 2-3% of their power to produce light, while the remaining 97-98% of their power is lost as heat. Fluorescent bulbs, while more efficient than incandescent bulbs, do not produce the same warm light as that generated by incandescent bulbs. Additionally, there are health and environmental concerns regarding the mercury contained in fluorescent bulbs.
Thus, an alternative light source is desired. One such alternative is a bulb utilizing an LED. An LED comprises a semiconductor junction that emits light due to an electrical current flowing through the junction. Compared to a traditional incandescent bulb, an LED bulb is capable of producing more light using the same amount of power. Additionally, the operational life of an LED bulb is orders of magnitude longer than that of an incandescent bulb, for example, 10,000-100,000 hours as opposed to 1,000-2,000 hours.
While there are many advantages to using an LED bulb rather than an incandescent or fluorescent bulb, LEDs have a number of drawbacks that have prevented them from being as widely adopted as incandescent and fluorescent replacements. One drawback is that an LED, being a semiconductor, generally cannot be allowed to get hotter than approximately 120° C. As an example, A-type LED bulbs have been limited to very low power (i.e., less than approximately 8 W), producing insufficient illumination for incandescent or fluorescent replacements.
One approach to alleviating the heat problem of LED bulbs is to use a thermally conductive liquid to cool the LEDS. To facilitate thermal dissipation, it may be advantageous to increase the thermal paths from the LED to the environment.
The following description is presented to enable a person of ordinary skill in the art to make and use the various embodiments. Descriptions of specific devices, techniques, and applications are provided only as examples. Various modifications to the examples described herein will be readily apparent to those of ordinary skill in the art, and the general principles defined herein may be applied to other examples and applications without departing from the spirit and scope of the various embodiments. Thus, the various embodiments are not intended to be limited to the examples described herein and shown, but are to be accorded the scope consistent with the claims.
Various embodiments are described below relating to LED bulbs. As used herein, an “LED bulb” refers to any light-generating device (e.g., a lamp) in which at least one LED is used to generate light. Thus, as used herein, an “LED bulb” does not include a light-generating device in which a filament is used to generate the light, such as a conventional incandescent light bulb. It should be recognized that the LED bulb may have various shapes in addition to the bulb-like A-type shape of a conventional incandescent light bulb. For example, the bulb may have a tubular shape, a globe shape, or the like. The LED bulb of the present disclosure may further include any type of connector; for example, a screw-in base, a dual-prong connector, a standard two- or three-prong wall outlet plug, bayonet base, Edison Screw base, single-pin base, multiple-pin base, recessed base, flanged base, grooved base, side base, or the like.
In some embodiments, LED bulb 100 may use 6 W or more of electrical power to produce light equivalent to a 40 W incandescent bulb. In some embodiments, LED bulb 100 may use 20 W or more to produce light equivalent to or greater than a 75 W incandescent bulb. Depending on the efficiency of the LED bulb 100, between 4 W and 16 W of heat energy may be produced when the LED bulb 100 is illuminated.
LED bulb 100 includes a shell 122 and base 124, which interact to form an enclosed volume 120 over one or more LEDs 102. As shown in
Shell 122 may be made from any transparent or translucent material such as plastic, glass, polycarbonate, or the like. Shell 122 may include dispersion material spread throughout the shell to disperse light generated by LEDs 102. The dispersion material prevents LED bulb 100 from appearing to have one or more point sources of light.
A thermally conductive liquid fills the volume 120. As used herein, the term “liquid” refers to a substance capable of flowing. Also, the substance used as the thermally conductive liquid is a liquid or at the liquid state within, at least, the operating, ambient-temperature range of the bulb. An exemplary temperature range includes temperatures between −40° C. to +40° C. The thermally conductive liquid may be mineral oil, silicone oil, glycols (PAGs), fluorocarbons, or other material capable of flowing. In the examples discussed below, 20 cSt viscosity polydimethylsiloxane (PDMS) liquid sold by Clearco is used as a thermally conductive liquid. It may be desirable to have the liquid chosen be a non-corrosive dielectric. Selecting such a liquid can reduce the likelihood that the liquid will cause electrical shorts and reduce damage done to the components of LED bulb 100.
The thermally conductive liquid is able to transfer heat away from the LEDs 102 and components in thermal connection with the LEDs 102. Typically, the thermally conductive liquid transfers the heat via conduction and convection to other, cooler components of the LED bulb 100, including the shell 122 and base 124. During typical operation, the temperature of the LEDs 102 is higher than that of the shell 122 and base 124. In some cases, the temperature difference between the LEDs 102 and the shell 122 results in passive convective flow of the thermally conductive liquid. The temperature difference between the LEDs 102 and the base 124 may also contribute to the induction of passive convective flow of the thermally conductive liquid. In general, the more heat that can be dissipated into the thermally conductive liquid, the greater the temperature difference between the components resulting in more passive convective flow.
LED bulb 100 also includes a laminate support structure 150 for mounting the plurality of LEDs 102. As shown in
In the present embodiment, a laser welded bond is used to attach the laminate support structure 150 to the hub 126. The laser weld forms a structural bond between the laminate support structure 150 and the hub 126. In the present embodiment, there is no threaded connection between the laminate support structure 150 and the hub 126. In addition to forming a structural bond between the two pieces, the laser weld also forms a thermal bond between the laminate support structure 150 and the hub 126. Thus, heat generated by the LED can be conducted through the laminate support structure 150 and dissipated to the hub 126 via the laser weld. Heat that is conducted to the hub 126 may also be conducted to base 124 and other components of the LED bulb 100. In an alternative embodiment, the laminate support structure 150 may be laser welded directly to a base to form a structural and thermal bond between the two pieces. In other embodiments, Other types of connections can also be used to attach the laminate support structure to the hub or base, including adhesive bonding, mechanical fastening, clamping, and the like.
In the present embodiment, the laminate support structure 150 is a laminate.
The flexible circuit layer 340 includes mounting pads for mechanically and electrically attaching the LEDs 102. (See, for example,
The mechanical support layer 330 of the laminate support structure 150 may be formed from a thermally conductive material, such as aluminum, copper, brass, magnesium, zinc, or the like. Since the mechanical support layer 330 is formed using a thermally conductive material, heat generated by LEDs 102 may be conductively transferred to other elements of the LED bulb 100. For example, because the laminate support structure 150 is at least partially immersed in the thermally conductive liquid, the mechanical support layer 330 is able to dissipate heat to the thermally conductive liquid. The mechanical support layer 330 is also connected to the base 124 via the hub 126/128. Depending on the type of connection between the components, the mechanical support layer 330 may conduct heat to the hub 126/128 and base 124.
In operation 502, a plurality of flange portions are formed in a laminate support structure.
In operation 504, the plurality of LEDs are attached to the flange portion of the laminate support structure. To utilize traditional surface mount or electronic assembly techniques, it may be advantageous to attach the LEDs to the flange portions of the laminate support structure 150 when the laminate is flat.
In an optional operation 506, the laminate support structure can be formed into a cylindrical or conical shape. This operation is not required if the laminate support structure is not flat and has already been formed into a cylindrical or conical shape. In some cases, the laminate support structure 150 is formed using a mandrel or round forming tool.
It may be advantageous to form the laminate support structure into a cylindrical or conical shape after the flange portions have been formed and LED components attached. However, it is not necessary that the laminate support structure 150 be attached to the LEDs or completely machined before forming. For example, the base of the laminate support structure may be machined flat or turned true after being formed into a cylindrical shape.
In another optional operation 508, the flange portions of the laminate support structure are bent to form a bent face. This operation is optional because some embodiments do not include a flange portion with a bent face. This operation is also not required if the flange portions have already been bent. Relief cuts 310 (shown in
In operation 510, the laminate support structure is connected to the base. As shown in
In operation 512, the shell is attached to the base to form an enclosed volume. As shown in
Although a feature may appear to be described in connection with a particular embodiment, one skilled in the art would recognize that various features of the described embodiments may be combined. Moreover, aspects described in connection with an embodiment may stand alone.
This application claims the benefit under 35 U.S.C. 119(e) of prior U.S. Provisional Patent Application No. 61/569,191, filed Dec. 9, 2011, U.S. Provisional Patent Application No. 61/579,626, filed Dec. 22, 2011, U.S. Provisional Patent Application No. 61/585,226, filed Jan. 10, 2012, and U.S. Provisional Patent Application No. 61/682,163, filed Aug. 10, 2012, each of which is hereby incorporated by reference in the present disclosure in its entirety.
Number | Name | Date | Kind |
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8277094 | Wheelock et al. | Oct 2012 | B2 |
8562185 | Wheelock et al. | Oct 2013 | B2 |
Number | Date | Country | |
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61569191 | Dec 2011 | US | |
61579626 | Dec 2011 | US | |
61585226 | Jan 2012 | US | |
61682163 | Aug 2012 | US |