Patent Application
20130201680
1. Technical Field
The subject matter of the present disclosure relates to lighting and lighting devices and, more particularly, to embodiments of a lamp using light-emitting diodes (LEDs), wherein the embodiments exhibit an intensity distribution consistent with common incandescent lamps.
2. Description of Related Art
Incandescent lamps (e.g., integral incandescent lamps and halogen lamps) mate with a lamp socket via a threaded base connector (sometimes referred to as an “Edison base” in the context of an incandescent light bulb), a bayonet-type base connector (i.e., bayonet base in the case of an incandescent light bulb), or other standard base connector. These lamps are often in the form of a unitary package, which includes components to operate from standard electrical power (e.g., 110 V and/or 220 V AC and/or 12 VDC). In the case of incandescent and halogen lamps, these components are minimal, as the lamp comprises an incandescent filament that operates at high temperature and efficiently radiates excess heat into the ambient. Many incandescent lamps are omni-directional light sources. These types of lamps provide light of substantially uniform optical intensity distribution (or, “intensity distribution”). Such lamps find diverse applications such as in desk lamps, table lamps, decorative lamps, chandeliers, ceiling fixtures, and other applications where a uniform distribution of light in all directions is desired.
Solid-state lighting technologies such as LEDs and LED-based devices often have performance that is superior to incandescent lamps. This performance can be quantified by its useful lifetime (e.g., its lumen maintenance and its reliability over time) and higher efficacy, e.g., measured in Lumens per Electrical Watt (LPW). For example, whereas the lifetime of incandescent lamps is typically in the range about 1000 to 5000 hours, lighting devices that use LED-based devices are capable of operation in excess of 25,000 hours, and perhaps as much as 100,000 hours or more; whereas the efficacy of incandescent and halogen lamps is typically in the range of 10-30 LPW, LED-based devices today can have efficacy of 40-100 LPW and even higher in the future.
Unfortunately, LED-based devices are highly directional by nature. Common LED devices are flat and emit light from only one side. Thus, although superior in performance, the intensity distribution of many commercially-available LED lamps intended as incandescent replacements is not consistent with the intensity distribution of incandescent lamps.
Yet another challenge with solid-state technology is the need to adequately dissipate heat. LED-based devices are highly temperature-sensitive in both performance and reliability as compared with incandescent or halogen filaments. These features are often addressed by placing a heat sink in contact with or in thermal contact with the LED device. However, the heat sink may block light that the LED device emits and hence further limits the ability to generate light of uniform optical intensity. Physical constraints such as regulatory limits that define maximum dimensions for all lamp components, including light sources, further limit that ability to properly dissipate heat.
The present disclosure describes lamps that disperse light from light emitting diodes (LEDs) in a manner that makes the lamps a suitable replacement for incandescent light bulbs. Embodiments of these lamps comprise a diffuser with a spheroid geometry defining a reflective area on top of the diffuser and a transmissive area subjacent the reflective area. The reflective area directs light from the LEDs to the transmissive area, where the light passes through the diffuser.
Other features and advantages of the disclosure will become apparent by reference to the following description taken in connection with the accompanying drawings.
Reference is now made briefly to the accompanying drawings, in which:
Where applicable like reference characters designate identical or corresponding components and units throughout the several views, which are not to scale unless otherwise indicated.
In addition to matching and/or exceeding both the ENERGY STAR® rating and L-PRIZE® specifications, embodiments of the LED lamp 100 are a favorable substitute, e.g., for incandescent bulbs, because the LED lamp 100 uses much less energy and provides adequate thermal dissipation to maintain operation of the LEDs 104 well beyond the operating life of incandescent bulbs. The LED lamp 100 likewise has a lamp profile, which is partially characterized by its maximum diameter 106. Values for the maximum diameter 106 of embodiments of the LED lamp 100 fit within profiles that meet various industry standards including ANSI and IEC standards. This lamp profile 106 makes the LED lamp 100 suitable for use as a replacement for a variety of incandescent light bulbs including A-type (e.g., A15, A19, A21, A23, etc.), G-type (e.g., G20, G30, etc.), as well as other profiles that various industry standards known and recognized in the art define. In examples of the lamp profile, the maximum diameter 106 can be from about 60 mm (e.g., typical of a GE A19 incandescent lamp) to about 69.5 mm (e.g., the maximum diameter allowed by ANSI for an A19 lamp). Artisans having skill in the relevant lighting arts can scale the dimensions of the lamp profile including the maximum diameter 106 to meet the dimensional specifications for the other A-line and G-type sizes.
In
The dissipating elements 118 are spaced apart from the outer surface of the diffuser 108. The spacing forms an air gap 120, which improves the ability of the LED lamp 100 to dissipate heat by natural or forced convection to the air by allowing for freer flow of air along the dissipating elements 118. The base assembly 114 also includes a body 122 that terminates at a connector 124. The body 122 and the connector 124 may house a variety of electrical components and circuitry that drive and control the light source 102. Examples of the connector 124 are compatible with Edison-type lamp sockets found in U.S. residential and office premises as well as other types of sockets and connectors that conduct electricity to the components of the lamp 100.
In operation, light from the LEDs 104 travels directionally toward the top of the diffuser 108 along the central axis C much more strongly than in any other direction. As discussed more below, the diffuser 108 exhibits optical properties in the upper portion 110 and the lower portion 112 to generate intensity distributions having uniformity of ±20% at distribution angles θ in the range of 0° to 135° or greater relative to the central axis C despite the directionality of the light the LEDs 104 emit. In the upper portion 110, for example, the diffuser 108 can reflect light downwardly at distribution angles θ of 90° or more, reaching in one example from 135° to 150° and, in another example, up to 150° or more. The reflected light transmits through the diffuser 108 in the lower portion 112. To promote effective intensity distribution of light, the shape and location of the dissipating elements 118 reduce interference with the transmitting light.
In the cross-section of
The diameters (e.g., diameter D and diameter d) along with the optical properties of the diffuser 200 in the transmissive area 204 and the reflective area 206 determine the intensity distribution of the LED lamps contemplated herein. Examples of the transmissive area 204 predominantly allow light to transmit from the interior volume 202 out through the diffuser 200. Examples of the reflective area 206 predominantly reflect light into the interior volume 202 and out through the transmissive area 204. However, the transmissive area 204 and the reflective area 208 may also exhibit combinations of light-reflecting and/or light-transmitting properties to provide intensity distributions consistent with the look and feel of incandescent light bulbs as well as to meet the various industry standards discussed herein. In one example, the intensity distribution of light through the transmissive area 204 is greater than the intensity distribution of light through the reflective area 206.
Variations in the contour 212 of the inner surface 210 can influence the intensity distribution the diffuser 210 exhibits, e.g., by defining the features of the spheroid geometry in one or both of transmissive area 204 and the reflective area 206. The contour 212 may cause the spheroid geometry to have a generally flatter shape than a sphere, e.g., having a shape of an oblate spheroid, thus the inner surface 210 will exhibit the flattened (or substantially flattened) top and peripheral radial curvatures as shown in
Examples of the diffuser 200 may be formed monolithically as a single unitary construction or as components that are affixed together. Materials, desired optical properties, and other factors (e.g., cost) may dictate the type of construction necessary to form the geometry (e.g., the spheroid geometry) of the diffuser 200. One exemplary multi-component construction is discussed in connection with
In one embodiment, the diffuser 300 includes a plurality of elements (e.g., a reflective dome element 302 and a transmissive body element 304). The reflective dome element 302 forms the top of the spheroid geometry and provides the reflective area (e.g., reflective area 206 of
Exemplary diffusers (e.g., diffuser 108, 200, and 300) of the present disclosure may comprise one or more coatings and/or surface treatments (collectively, “coatings”) that cover areas of the inner surface to enhance the optical properties of the diffuser. Properties of such coatings may determine the relative scope, position, surface area, and optical properties of the transmissive area and the reflective area. These properties may result from the composition of the coatings including compositions with material optical properties that are, in whole or in part, reflective, transmissive, refractive, diffractive, specular, diffuse, emissive, and combinations and derivations thereof. Paints, frostings, enamels, powder coatings, gratings, lenslets, prisms, engineered surfaces, and materials of similar configurations are all suitable for use as coatings on the inner surface. These materials may include particles and other light-scattering media. Delineation between the transmissive area and the reflective area may require that the material coatings have different properties. In one example, coatings found in the reflective area may be more reflective than coatings found in the transmissive area.
Materials for use in construction of exemplary diffusers can also have properties that are determinative of optical properties in the reflective area and the transmissive area. Like the coatings discussed above, exemplary diffusers can comprise any number and combination of materials with different material optical properties. Exemplary materials include plastics, ceramics, quartz, composites, nano-structures, and glass. In one example, exemplary diffusers can comprise materials that are more reflective in the reflective area and materials that are relatively less reflective in the transmissive area. In other examples, exemplary diffusers can comprise the same material (or combination of materials) throughout, wherein use of one or more coatings on the surfaces of the exemplary diffusers causes the different optical properties associated with the transmissive area and the reflective area. In one example, the reflective area is opaque. The reflective area may also exhibit specular reflectivity, diffuse reflectivity, and/or combinations thereof. In one example, the diffuser comprises a low loss material.
In one embodiment, the dissipating elements 408 have a body 410 with a pair of optically active surfaces (e.g., a first surface 412 and a second surface 414). The body 410 extends from the base element 406 and terminates at a diffuser end 416, which is proximate the diffuser (not shown) in the LED lamp. The diffuser end 416 includes an outer peripheral surface 418 and an inner peripheral surface 420, which is near the outer surface of the diffuser (not shown). In one example, the inner peripheral surface 420 has a contour shape that matches the shape of the proximate and corresponding portion of the diffuser (not shown).
Spacing between the inner peripheral surface 420 and the outer surface of the diffuser (e.g., diffuser 108, 200, and 300) forms an air gap (e.g., air gap 120 of
Thermal properties of the dissipating elements 408 can have a significant effect on the total energy that the thermal management system 404 dissipates and, accordingly, the operating temperature of the light engine 402 and any corresponding driver electronics. Since operating temperature can limit the performance and reliability of the light engine 402 and driver electronics, it is critical to select one or more materials for use in the thermal management system 404 with appropriate properties. The thermal conductivity of a material defines the ability of a material to conduct heat. When used in context of a component, the thermal conductivity of the material in a components, along with the dimensions and/or characteristics (e.g., shape) of the components, defines the thermal conductance of the component, which is the ability of the component to conduct heat. Since the light engine 402 may have a very high heat flux density, the thermal management system 404 should preferably comprise materials with high thermal conductivity, and components having dimensions providing high thermal conductance so that the generated heat can be conducted through a low thermal resistance (i.e., the inverse of thermal conductance) away from the light engine 402.
In various embodiments, the thermal management system 404 can comprise one or more high thermal conductivity materials. A high conductivity material will allow more heat to move from the thermal load to ambient and result in a reduction in temperature rise of the thermal load. Exemplary materials can include metallic materials such as alloy steel, cast aluminum, extruded aluminum, and copper. Other materials can include engineered composite materials such as thermally-conductive polymers as well as plastics, plastic composites, ceramics, ceramic composite materials, nano-materials, such as carbon nanotubes (CNT) or CNT composites. Exemplary materials can exhibit thermal conductivities of about 50 W/m-K, from about 80 W/m-K to about 100 W/m-K, 170 W/m-K, 390 W/m-K, and from about 1 W/m-K to about 50 W/m-K, respectively.
Practical considerations such as manufacturing process or cost may also affect the selection of materials and the effective thermal properties. For example, cast aluminum, which is generally less expensive in large quantities, has a thermal conductivity value approximately half of extruded aluminum. It is preferred for ease and cost of manufacture to use predominantly one material for the majority of the thermal management system 404, but combinations of cast/extrusion methods of the same material or even incorporating two or more different materials into construction of the thermal management system 404 can maximize cooling.
The thermal management system 404 may comprise 3 or more of the dissipating elements 408 arranged radially about the central axis C. The dissipating elements 408 can be equally spaced from one another so that adjacent ones of the dissipating elements 408 are separated by at least about 45° for an 8-element arrangement and 22.5° for a 16-element arrangement. Physical dimensions (e.g., width, thickness, and height) can also determine the necessary separation between the dissipating elements 408. For example, when used in conjunction with the multi-component diffuser (e.g., diffuser 300 of
Exemplary light engines (e.g., light engine 102 and 402) can comprise a planar LED-based light source that emits light having a nearly Lambertian intensity distribution, compatible with exemplary diffusers for producing omni-directional illumination distribution. In one embodiment, the planar LED-based Lambertian light source includes a plurality of LED devices (e.g., LEDs 104) mounted on a circuit board (not shown), which is optionally a metal core printed circuit board (MCPCB). The LED devices may comprise different types of LEDs. For example, exemplary light engines may comprise one or more first LED devices and one or more second LED devices having respective spectra and intensities that mix to render white light of a desired color temperature and color rendering index (CRI). In one embodiment, the first LED devices output white light, which in one example has a greenish rendition (achievable, for example, by using a blue- or violet-emitting LED chip that is coated with a suitable “white” phosphor). The second LED devices output red and/or orange light (achievable, for example, using a GaAsP or AlGaInP or other epitaxy LED chip that naturally emits red and/or orange light, or by selecting a phosphor that emits red or orange light). The light from the first LED devices and second LED devices blend together to produce improved color rendition. In another embodiment, the planar LED-based Lambertian light source can also comprise a single LED device or an array of LED emitters incorporated into a single LED device, which may be a white LED device and/or a saturated color LED device and/or so forth. In another embodiment, the LED emitter are organic LEDs comprising, in one example, organic compounds that emit light.
As used herein, an element or function recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural said elements or functions, unless such exclusion is explicitly recited. Furthermore, references to “one embodiment” of the claimed invention should not be interpreted as excluding the existence of additional embodiments that also incorporate the recited features.
This written description uses examples to disclose embodiments of the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.
