Patent Application
20100187961
1. Field
The present disclosure relates to light emitting devices, and more particularly to phosphor housings for light emitting diode lamps.
2. Background
Light emitting diodes (LEDs) are attractive candidates for replacing conventional light sources such as incandescent and fluorescent lamps. LEDs have substantially higher light conversion efficiencies than incandescent lamps, and longer lifetimes than both types of conventional light sources. In addition, some types of LEDs now have higher conversion efficiencies than fluorescent light sources and still higher conversion efficiencies have been demonstrated in the laboratory. Finally, LEDs require lower voltages than fluorescent lamps, and therefore, provide various power saving benefits.
Unfortunately, LEDs produce light in a relatively narrow spectrum band. In order to provide a suitable replacement for conventional light sources, LED light sources must produce white light. A white light source may be constructed from a blue LED that is covered with a layer of phosphor. Such light sources will be referred to as “phosphor based white LEDs.” The blue light from the LED excites the phosphor at a high energy, which results in a portion of the blue light being converted to lower energy yellow light. The ratio of blue to yellow light may be chosen such that the LED light source appears to be white.
Phosphor based white LEDs present a technical challenge when used as a light source. The blue LED tends to generate a significant amount of heat. When the blue light strikes the phosphor, additional heat is generated due to stokes shift and quantum efficiency loss. The heat build up in the phosphor based white LED tends to degrade the performance of the blue LED and the phosphor, causing light output drop, color temperature shift, and shorter lifetime. Heretofore, heat sinks have been used to dissipate the heat generated by these phosphor based white LEDs.
Industry acceptance of LEDs as light sources may depend on the adaptability of these sources into existing lighting fixtures. By way of example, it would be desirable to construct an LED light source that is interchangeable with a standard light bulb so that it may be simply screwed into an existing light fixture. This may not be possible, however, if the LED light source is required to be mounted onto a heat sink. Accordingly, there is a need in the art for LED light sources with improved heat dissipation to facilitate designs that provide direct replacement for conventional light sources (e.g., incandescent and fluorescent light bulbs).
In one aspect of the disclosure, a light emitting apparatus includes a housing having a transparent bulb with phosphor, and at least one LED positioned within the housing to excite the phosphor and emit light through the transparent bulb.
In another aspect of the disclosure, light emitting apparatus includes a housing having a transparent bulb, and means, within the housing, for emitting light having a first wavelength, wherein the transparent bulb further comprises means for converting a portion of the light to a second wavelength.
In yet another aspect of the disclosure, light emitting apparatus includes at least one LED configured to emit light, and a housing containing said at least one LED, wherein the housing comprises a transparent bulb with phosphor positioned to receive at least a portion of the light emitted from said at least one LED.
In a further aspect of the disclosure, a method of fabricating a light emitting apparatus includes forming a housing having a transparent bulb with phosphor, and assembling the housing including positioning at least one LED within the housing to excite the phosphor and emit light through the transparent bulb.
It is understood that other aspects of the present invention will become readily apparent to those skilled in the art from the following detailed description, wherein it is shown and described only exemplary configurations of an LED lamp by way of illustration. As will be realized, the present invention includes other and different aspects of an LED lamp and its several details are capable of modification in various other respects, all without departing from the spirit and scope of the present invention. Accordingly, the drawings and the detailed description are to be regarded as illustrative in nature and not as restrictive.
Various aspects of the present invention are illustrated by way of example, and not by way of limitation, in the accompanying drawings, wherein:
The present invention is described more fully hereinafter with reference to the accompanying drawings, in which various aspects of the present invention are shown. This invention, however, may be embodied in many different forms and should not be construed as limited to the various aspects of the present invention presented throughout this disclosure. Rather, these aspects are provided so that this disclosure will be thorough and complete, and will filly convey the scope of the present invention to those skilled in the art. The various aspects of the present invention illustrated in the drawings may not be drawn to scale. Rather, the dimensions of the various features may be expanded or reduced for clarity. In addition, some of the drawings may be simplified for clarity. Thus, the drawings may not depict all of the components of a given apparatus (e.g., device) or method.
Various aspects of the present invention will be described herein with reference to drawings that are schematic illustrations of idealized configurations of the present invention. As such, variations from the shapes of the illustrations as a result, for example, manufacturing techniques and/or tolerances, are to be expected. Thus, the various aspects of the present invention presented throughout this disclosure should not be construed as limited to the particular shapes of elements (e.g., regions, layers, sections, substrates, bulb shapes, etc.) illustrated and described herein but are to include deviations in shapes that result, for example, from manufacturing. By way of example, an element illustrated or described as a rectangle may have rounded or curved features and/or a gradient concentration at its edges rather than a discrete change from one element to another. Thus, the elements illustrated in the drawings are schematic in nature and their shapes are not intended to illustrate the precise shape of an element and are not intended to limit the scope of the present invention.
It will be understood that when an element such as a region, layer, section, substrate, or the like, is referred to as being “on” another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present. It will be further understood that when an element is referred to as being “formed” on another element, it can be grown, deposited, etched, attached, connected, coupled, or otherwise prepared or fabricated on the other element or an intervening element.
Furthermore, relative terms, such as “lower” or “bottom” and “upper” or “top,” may be used herein to describe one element's relationship to another element as illustrated in the drawings. It will be understood that relative terms are intended to encompass different orientations of an apparatus in addition to the orientation depicted in the drawings. By way of example, if an apparatus in the drawings is turned over, elements described as being on the “lower” side of other elements would then be oriented on the “upper” side of the other elements. The term “lower”, can therefore, encompass both an orientation of “lower” and “upper,” depending of the particular orientation of the apparatus. Similarly, if an apparatus in the drawing is turned over, elements described as “below” or “beneath” other elements would then be oriented “above” the other elements. The terms “below” or “beneath” can, therefore, encompass both an orientation of above and below.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and this disclosure.
As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The term “and/or” includes any and all combinations of one or more of the associated listed items.
Various aspects of an LED lamp with a phosphor housing will now be presented. However, as those skilled in the art will readily appreciate, these aspects may be extended to other light sources without departing from the scope of the invention. The LED lamp may be configured as a direct replacement for conventional light sources, including, by way of example, incandescent, fluorescent, halogen, quartz, high-density discharge (HID), and neon lamps or bulbs. The LED is well known in the art and therefore, will only briefly be discussed to provide a complete description of the invention.
In this example, the N-type semiconductor region 104 is formed on a substrate 102 and the P-type semiconductor region 108 is formed on the active layer 106, however, the regions may be reversed. That is, the P-type semiconductor region 108 may be formed on the substrate 102 and the N-type semiconductor region 104 may formed on the active layer 106. As those skilled in the art will readily appreciate, the various concepts described throughout this disclosure may be extended to any suitable layered structure. Additional layers or regions (not shown) may also be included in the LED 100, including but not limited to buffer, nucleation, contact and current spreading layers or regions, as well as light extraction layers.
The P-type semiconductor region 108 is exposed at the top surface, and therefore, the P-type electrode 112 may be readily formed thereon. However, the N-type semiconductor region 104 is buried beneath the N-type semiconductor layer 108 and the active layer 106. Accordingly, to form the N-type electrode 110 on the N-type semiconductor region 104, a cutout area or “mesa” is formed by removing a portion of the active layer 106 and the P-type semiconductor region 108 by means well known in the art to expose the N-type semiconductor layer 104 therebeneath. After this portion is removed, the N-type electrode 110 may be formed.
In a configuration of an LED lamp, an LED array 200 may be used to provide increased light output
Optionally, the LED array 200 may be encapsulated in an epoxy, silicone, or other thermally-conductive transparent encapsulation material. The encapsulation material may be used to focus the light emitted from the LEDs 100, as well as protect the LEDs 100 from the elements. By encapsulating the LEDs 100, the LED array 200 becomes extremely durable with no loose or moving parts. As a result, the LED array 200 becomes essentially an array of PN junction semiconductor diodes that emit light when a forward voltage is applied, resulting in a very reliable device.
Turning to
Turning to
A plate 408 anchored to the base 404 provides support for the LED array 406. In one configuration of an LED lamp 400, standoffs 410 extending from the plate 408 are used to separate the LED array 406 from the plate 408. Examples include plastic standoffs with conical heads that can be pushed through holes in the substrate of the LED array 406 or hollow plastic standoffs with internal threads that allow the LED array 406 to be mounted with screws. Other ways to mount the LED array 406 will be readily apparent to those skilled in the art from the teachings presented throughout this disclosure. The plate 408 may be constructed from any suitable insulting material, including by way of example, glass.
A fan 412 may be used to cool the LED array 406. A non-limiting example of a fan that is well suited for LED lamp applications is an RSD5 solid-state fan developed by Thorm Micro Technologies, Inc. The RSD5 uses a series of live wires that produce an ion rich gas with free electrons for conducting electricity. The wires lie within uncharged conducting plates that are contoured into half-cylindrical shapes to partially envelope the wires. Within the electric field that results, the ions push neutral air molecules from the wire to the plate, generating air flow. The fan 412 may be mounted to the substrate of the LED array 406 as shown in
The plate 408 also provides a means for routing wires 414a and 414b from the LED array 406 to electrical contacts 416a and 416b on the base 404. In one configuration of an LED lamp 400, the wires 414a and 414b may be routed from the LED array 406 to the plate 412 through the plastic hollow standoffs previously described. In another configuration of an LED lamp 400, the wires 414a and 414b themselves can be used to separate the LED array 404 from the plate 408, thus eliminating the need for standoff. In the latter configuration, the wires 414a and 414b may be spot welded to feedthrough holes in the plate 408 with another set of spot welded wires extending from the feedthrough holes to the electrical contacts 416a and 416b on the base 404.
The arrangement of electrical contacts 416a and 416b may vary depending on the particular application. By way of example, the LED lamp 400 may have a base 404 with a screw cap configuration, as shown in
Power may be applied to the LED array 406 and the fan 412 Through the electrical contacts 416a and 416b. An AC-DC converter (not shown) may be used to generate a DC voltage from a lamp socket connected to a wall-plug in a household, office building, or other facility. The DC voltage generated by the AC-DC converter may be provided to a driver circuit (not shown) configured to drive both the LED array 406 and the fan 412. The AC-DC converter and the driver circuit may be located in the base 404, on the LED array 406, or anywhere else in the housing 402. In some applications, the AC-DC converter may not be needed. By way of example, the LED array 406 and the fan 412 may be designed for AC power. Alternatively, the power source may be DC, such as the case might be in automotive applications. The particular design of the power delivery circuit for any particular application is well within the capabilities of one skilled in the art.
The bulb 403 may include phosphor 418. The phosphor 418 may be formed on the inner surface of bulb 403 as shown in
By providing a bulb 403 with phosphor 418, the heat generated in the LED array 406 is reduced, and as a result, the LED array 406 outputs more light with improved reliability and longer lifetime. In addition, the heat generated by the phosphor 418 is widely distributed over the housing 402, and therefore, the phosphor 418 will experience less degradation, less color shift, better stability, and more light output. Finally, the light resulting from phosphor scattering that would otherwise be absorbed by the LED array 406 if it were completely encapsulated by the phosphor is no longer an issue, resulting in increased light output.
Various examples of a process for forming phosphor on a bulb as shown in
One example of a process for applying phosphor to the bulb will now be presented. In this example, the phosphor is mixed with a binder. Alternatively, a binder may be applied to the inner surface of the bulb 403. Next, the phosphor is introduced into the bulb 403. By way of example, in the bulb 403 configuration shown in
Another example of a process for applying phosphor to a bulb involves electro-deposition. In this example, the phosphor is deposited onto a plate. The plate and the bulb are then connected to a DC power supply or battery with the plate being connected to the positive terminal and the bulb being connected to the negative terminal. Both the plate and bulb may be immersed in an electrolyte solution. When power is applied, the metal molecules in the phosphor oxidize and are dissolved in the solution. At the bulb, the metal molecules dissolved in the electrolyte solution are reduced at the interface between the solution and the bulb such that they plate out onto the bulb. This process may be repeated as many times as necessary to achieve the desired amount of phosphor. As with the previous example, a binder may be mixed with the phosphor, or alternatively, a binder may be applied to the inner surface of the bulb.
A further example of a process for applying phosphor to a bulb 403 involves vapor deposition. In this example, a thin film of phosphor is deposited on the inner surface of the bulb 403 by the condensation of vaporized phosphor onto the glass. More specifically, the process is performed by vaporizing the phosphor and then filling the bulb 403 with the vaporized gas. Similar to the previous examples, the phosphor may be mixed with a binder, or the binder can be applied to the inner surface of the bulb. The gas is then cooled resulting in a layer of solidified phosphor on the inner surface of the bulb. This process may be repeated as many times as necessary to achieve the desired amount of phosphor.
As an alternative to forming the phosphor on the bulb, the phosphor may be embedded in the bulb as shown in
The various methods presented thus far for forming a bulb with phosphor are non-limiting examples intended to enable those skilled in the art to practice the full scope of the invention. It will be understood that other methods may be used without departing from the spirit and scope of the invention.
The LED lamp 400 may be assembled by mounting the LED array 406 and the fan 412 onto the plate 408 using standoffs 410 or some other suitable means. Once the LED array 406 and the fan 412 are mounted to the plate 408, the plate may be attached to the neck 407 of the bulb 403. In the case where the plate 408 is glass, the bulb 403 may be fused to the plate 408. The electrical wires 414a and 414b extending from the plate 408 may be connected to the electrical contacts 416a and 416b, respectively, and then the bulb 403 may be mounted to the base 404.
Power may be applied between to the LED arrays 608 and the fans 612 through any pair of electrical contacts. By way of example, one of the electrical contacts 614′ on one cap 606a may be connected to a voltage source and one of the electrical contacts 616′ on the other cap 606b may be connected to the voltage return. In higher current applications, the voltage source may be connected to both electrical contacts 614′ and 614″ extending from one cap 606a and the voltage return may be connected to both electrical contacts 616′ and 616″ extending from the other cap 606b. An AC-DC converter (not shown) and driver (not shown) may be used to generate a DC voltage and drive the LED arrays 608 and fans 612. The AC-DC converter and driver may be mounted onto the substrate 610 or located elsewhere in the LED lamp 600. Alternatively, the AC-DC converter and/or driver may be mounted outside the lamp, either inside or outside of the light fixture.
The various aspects of his disclosure are provided to enable one of ordinary skill in the art to practice the present invention Various modifications to aspects presented throughout this disclosure will be readily apparent to those skilled in the art, and the concepts disclosed herein may be extended to other LED lamp configurations regardless of the shape or diameter of the glass enclosure and the base and the arrangement of electrical contacts on the lamp. By way of example, these concepts may be applied to bulb shapes commonly referred to in the art as A series, B series, C-7/F series, ER, G series, GT, K, P-25/PS-35 series, BR series, MR series, AR series, R series, RP-11/S series, PAR Series, Linear series, and T series; ED17, ET, ET-18, ET23.5, E-25, BT-28, BT-37, BT-56. These concepts may also be applied to base sizes commonly referred to in the art as miniature candela screw base E10 and E11, candela screw base E12, intermediate candela screw base E17, medium screw base E26, E26D, E27 and E27D, mogul screw base E39, mogul Pf P40s, medium skirt E26/50×39, candela DC bay, candela SC bay B15, BA15D, BA15S, D. C. Bayonet, 2-lug sleeve B22d, 3-lug sleeve B22-3, medium Pf P28s, mogul bi-post G38, base RSC, screw terminal, disc base, single contact, medium bi-post, mogul end prong, spade connector, mogul pre-focus and external mogul end prong; admedium skirted, medium skirted, position-oriented mogul, BY 22 D, Fc2, ceramic spade series (J, G, R), RRSC, RSC; single pin series, bi-pin series, G, GX, 2G series. Thus, the claims are not intended to be limited to the various aspects of his disclosure, but are to be accorded the full scope consistent with the language of the claims. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 U.S.C. §112, sixth paragraph, unless the element is expressly recited using the phrase “means for” or, in the case of a method claim, the element is recited using the phrase “step for.”
