Patent Application
20140268720
1. Field of the Invention
The invention relates to lighting fixtures and, more particularly, to modular lighting fixtures that are well-suited for use with solid state lighting sources, such as light emitting diodes (LEDs).
2. Description of the Related Art
Troffer-style fixtures (troffers) are ubiquitous in commercial office and industrial spaces throughout the world. In many instances these troffers house elongated fluorescent light bulbs that span the length of the troffer. Troffers may be mounted to or suspended from ceilings or walls. Often the troffer may be recessed into the ceiling, with the back side of the troffer protruding into the plenum area above the ceiling. Typically, elements of the troffer on the back side dissipate heat generated by the light source into the plenum where air can be circulated to facilitate the cooling mechanism. U.S. Pat. No. 5,823,663 to Bell, et al. and U.S. Pat. No. 6,210,025 to Schmidt, et al. are examples of typical troffer-style fixtures.
More recently, with the advent of the efficient solid state lighting sources, these troffers have been used with LEDs, for example. LEDs are solid state devices that convert electric energy to light and generally comprise one or more active regions of semiconductor material interposed between oppositely doped semiconductor layers. When a bias is applied across the doped layers, holes and electrons are injected into the active region where they recombine to generate light. Light is produced in the active region and emitted from surfaces of the LED.
LEDs have certain characteristics that make them desirable for many lighting applications that were previously the realm of incandescent or fluorescent lights. Incandescent lights are very energy-inefficient light sources with approximately ninety percent of the electricity they consume being released as heat rather than light. Fluorescent light bulbs are more energy efficient than incandescent light bulbs by a factor of about 10, but are still relatively inefficient. LEDs by contrast, can emit the same luminous flux as incandescent and fluorescent lights using a fraction of the energy.
In addition, LEDs can have a significantly longer operational lifetime. Incandescent light bulbs have relatively short lifetimes, with some having a lifetime in the range of about 750-1000 hours. Fluorescent bulbs can also have lifetimes longer than incandescent bulbs such as in the range of approximately 10,000-20,000 hours, but provide less desirable color reproduction. In comparison, LEDs can have lifetimes between 50,000 and 70,000 hours. The increased efficiency and extended lifetime of LEDs is attractive to many lighting suppliers and has resulted in their LED lights being used in place of conventional lighting in many different applications. It is predicted that further improvements will result in their general acceptance in more and more lighting applications. An increase in the adoption of LEDs in place of incandescent or fluorescent lighting would result in increased lighting efficiency and significant energy saving.
Other LED components or lamps have been developed that comprise an array of multiple LED packages mounted to a (PCB), substrate or submount. The array of LED packages can comprise groups of LED packages emitting different colors, and specular reflector systems to reflect light emitted by the LED chips. Some of these LED components are arranged to produce a white light combination of the light emitted by the different LED chips.
In order to generate a desired output color, it is sometimes necessary to mix colors of light which are more easily produced using common semiconductor systems. Of particular interest is the generation of white light for use in everyday lighting applications. Conventional LEDs cannot generate white light from their active layers; it must be produced from a combination of other colors. For example, blue emitting LEDs have been used to generate white light by surrounding the blue LED with a yellow phosphor, polymer or dye, with a typical phosphor being cerium-doped yttrium aluminum garnet (Ce:YAG). The surrounding phosphor material “downconverts” some of the blue light, changing it to yellow light. Some of the blue light passes through the phosphor without being changed while a substantial portion of the light is downconverted to yellow. The LED emits both blue and yellow light, which combine to yield white light.
In another known approach, light from a violet or ultraviolet emitting LED has been converted to white light by surrounding the LED with multicolor phosphors or dyes. Indeed, many other color combinations have been used to generate white light.
Some recent designs have incorporated an indirect lighting scheme in which the LEDs or other sources are aimed in a direction other than the intended emission direction. This may be done to encourage the light to interact with internal elements, such as diffusers, for example. One example of an indirect fixture can be found in U.S. Pat. No. 7,722,220 to Van de Ven which is commonly assigned with the present application.
Modern lighting applications often demand high power LEDs for increased brightness. High power LEDs can draw large currents, generating significant amounts of heat that must be managed. Many systems utilize heat sinks which must be in good thermal contact with the heat-generating light sources. Troffer-style fixtures generally dissipate heat from the back side of the fixture that which often extends into the plenum. This can present challenges as plenum space decreases in modern structures. Furthermore, the temperature in the plenum area is often several degrees warmer than the room environment below the ceiling, making it more difficult for the heat to escape into the plenum ambient.
An embodiment of a modular light fixture comprises the following elements. A housing subassembly is removably attached to a lighting subassembly. The lighting subassembly comprises at least one light source. Driver electronics are connected to control said at least one light source.
An embodiment of a modular light fixture comprises the following elements. A housing subassembly and a lighting subassembly are removably attached. The lighting subassembly comprises a body, a back reflector at least partially surrounded by the body, a heat sink with a mount surface mounted proximate to the back reflector, a plurality of light sources on the mount surface positioned such that at least a portion of the light emitted initially impinges on the back reflector, and a lens attached to the body, the lens configured to transmit at least a portion of light from the at least one light source. Driver electronics are connected to control the plurality of light sources.
An embodiment of a modular light fixture comprises the following elements. A housing subassembly is removably amounted to a lighting subassembly. The housing subassembly comprises an external mount mechanism. The lighting subassembly comprises at least one light source and driver electronics.
An embodiment of an extendable linear fixture comprises the following elements. A plurality of modular fixtures each comprises a lighting subassembly that is removably attached to a housing subassembly. The housing subassembly comprises an external mount mechanism. The lighting subassembly comprises at least one light source. At least one joiner structure is between adjacent of said modular fixtures, connecting said modular fixtures together.
a is a perspective view of a lighting subassembly according to an embodiment of the present invention.
a-c show a top plan view of portions of several light strips that may be used in embodiments of the present invention.
a-c show perspective views of a modular light fixture according to an embodiment of the present invention during various stages of installation.
a-c are perspective views of a modular light fixture according to an embodiment of the present invention.
a-c show perspective views of an end cap that may be used in embodiments of present invention.
a-c shows an embodiment of an extended modular fixture according to an embodiment of the present invention.
Embodiments of the present invention provide an indirect modular troffer-style fixture that is particularly well-suited for use with solid state light sources, such as LEDs, to provide a surface ambient light (SAL). The fixture comprises two structural components: a housing subassembly and a lighting subassembly. These two subassemblies may be removably attached to operate as a singular fixture. Many different lighting subassemblies may be compatible with a single housing subassembly and vice versa. The housing subassembly comprises a body that is mountable to an external structure. The lighting subassembly comprises the light sources and optical elements that tailor the outgoing light to achieve a particular profile. Both the shape and the arrangement of these elements provide the desired light output distribution. Electronics necessary to power and control the light sources may be disposed in either the housing subassembly or the lighting subassembly. Structural elements, such as end caps, may be used to hold the fixture elements and the subassemblies in position relative to each other. Various mount mechanisms may be used to attach the fixture to a surface such as a ceiling or a wall.
In this embodiment, the driver electronic component boxes comprise a backup battery box 202a, a driver box 202b, and a step-down converter box 202c. The step-down converter box 202c is an optional element that may be included in models requiring a non-standard voltage, for example, models for use in Canada or another country. Many different mount arrangements are possible to accommodate the necessary electronic components within the housing subassembly 102, and many different combinations of electronic components may be used.
In one embodiment the electronic components comprise a step-down converter 102a, a driver circuit 102b, and a battery backup 102c. At the most basic level a driver circuit may comprise an AC/DC converter, a DC/DC converter, or both. In one embodiment, the driver circuit comprises an AC/DC converter and a DC/DC converter both of which are located in the housing subassembly 102. In another embodiment, the AC/DC conversion is done in the housing subassembly 102, and the DC/DC conversion is done in the lighting subassembly 104. Another embodiment uses the opposite configuration where the DC/DC conversion is done in the housing subassembly 102, and the AC/DC conversion is done in the lighting subassembly 104. In yet another embodiment, both the AC/DC converter and the DC/DC converter are located in the lighting subassembly 104. It is understood that the various electronic components may distributed in different ways in one or both of the subassemblies 102, 104.
a is a perspective view of an embodiment of a lighting subassembly 400.
Information from the sensor 408 is used to control the on/off state of the internal light sources to conserve energy when lighting in a particular area is not needed. The sensor may also be used to regulate the brightness of the sources, allowing for high and low modes of operation. In one embodiment, a passive infrared (PIR) sensor 408 is used to determine when a person is in the vicinity of the fixture and thus would require light in the area. When the sensor detects a person, a signal is sent to the driver circuit and the lights are turned on, or if the lights remain on at all times, then the lights are switched to the high mode of operation. When the heat signature is no longer present, then the sources switch back to the default state (e.g., off or low mode). Many other types of sensors may be used such as a motion detector or an ultrasonic sensor, for example.
b is a cross-sectional view of the lighting subassembly 400. In this embodiment, at least one LED 410 on a light strip 412 is mounted on an internal surface 414 of the heat sink 402. The LEDs 410 can also be mounted to other internal surfaces inside the optical chamber. When powered, the LEDs 410 emit light in a direction such that it is incident on a back reflector 416. The back reflector 416 then redirects at least a portion of the light out of the optical chamber through the lenses 404.
In this embodiment, the back side of the heat sink 402 functions as an internal surface of the lighting subassembly 400. The heat sink 402 can be constructed using many different thermally conductive materials. For example, the heat sink 402 may comprise an aluminum body. Similarly as the back reflector 416, the heat sink 402 can be extruded for efficient, cost-effective production and convenient scalability. In other embodiments, the heat sink 402 can be integrated with a printed circuit board (PCB), for example. Indeed the PCB itself may function as the heat sink, so long as the PCB is capable of handling thermal transmission of the heat load. Many other heat sink structures are possible.
The heat sink 402 can be mounted to the lighting subassembly 400 using various methods such as, screws, pins, or adhesive, for example. In this particular embodiment, the heat sink 402 comprises an elongated thin body with a substantially flat area internal surface 414 on which one or more light sources can be mounted. The flat area provides for good thermal communication between the heat sink 402 and the light sources 410 mounted thereon. In some embodiments, the light sources will be pre-mounted on light strips.
Many industrial, commercial, and residential applications call for white light sources. Embodiments of lighting subassemblies may comprise one or more emitters producing the same color of light or different colors of light. In one embodiment, a multicolor source is used to produce white light. Several colored light combinations will yield white light. For example, it is known in the art to combine light from a blue LED with wavelength-converted yellow (blue-shifted-yellow or “BSY”) light to yield white light with correlated color temperature (CCT) in the range from 5000K to 7000K (often designated as “cool white”). Both blue and BSY light can be generated with a blue emitter by surrounding the emitter with phosphors that are optically responsive to the blue light. When excited, the phosphors emit yellow light which then combines with the blue light to make white. In this scheme, because the blue light is emitted in a narrow spectral range it is called saturated light. The BSY light is emitted in a much broader spectral range and, thus, is called unsaturated light.
Another example of generating white light with a multicolor source is combining the light from green and red LEDs. RGB schemes may also be used to generate various colors of light. In some applications, an amber emitter is added for an RGBA combination. The previous combinations are exemplary; it is understood that many different color combinations may be used in embodiments of the present invention. Several of these possible color combinations are discussed in detail in U.S. Pat. No. 7,213,940 to Van de Ven et al.
The lighting strips 500, 520, 540 each represent possible LED combinations that result in an output spectrum that can be mixed to generate white light. Each lighting strip can include the electronics and interconnections necessary to power the LEDs. In some embodiments the lighting strip comprises a printed circuit board with the LEDs mounted and interconnected thereon. The lighting strip 500 includes clusters 502 of discrete LEDs, with each LED within the cluster 502 spaced a distance from the next LED, and each cluster 502 spaced a distance from the next cluster 502. If the LEDs within a cluster are spaced at too great distance from one another, the colors of the individual sources may become visible, causing unwanted color-striping. The clusters on the light strips can be compact. In some embodiments, an acceptable range of distances for separating consecutive LEDs within a cluster is not more than approximately 8 mm.
The scheme shown in
The lighting strip 520 includes clusters 522 of discrete LEDs. The scheme shown in
The lighting strip 540 includes clusters 542 of discrete LEDs. The scheme shown in
The lighting schemes shown in
Again with reference to
The back reflector 416 is an example of one shape that may be used in the lighting subassembly 400. The back reflector 416 may be designed to have several different shapes to perform particular optical functions, such as color mixing and beam shaping, for example. The back reflector 416 may be rigid, or it may be flexible in which case it may be held to a particular shape by compression against other surfaces. Emitted light may be bounced off of one or more surfaces. This has the effect of disassociating the emitted light from its initial emission angle. Output color uniformity typically improves with an increasing number of bounces, but each bounce has an associated optical loss. In some embodiments an intermediate diffusion mechanism (e.g., formed diffusers and textured lenses) may be used to mix the various colors of light.
The back reflector 416 should be highly reflective in the wavelength ranges emitted by the source(s) 122. In some embodiments, the reflector may be 93% reflective or higher. In other embodiments it may be at least 95% reflective or at least 97% reflective.
The back reflector 416 may comprise many different materials. For many indoor lighting applications, it is desirable to present a uniform, soft light source without unpleasant glare, color striping, or hot spots. Thus, the back reflector 416 may comprise a diffuse white reflector such as a microcellular polyethylene terephthalate (MCPET) material or a Dupont/WhiteOptics material, for example. Other white diffuse reflective materials can also be used.
Diffuse reflective coatings may be used on a surface of the back reflector to mix light from solid state light sources having different spectra (i.e., different colors). These coatings are particularly well-suited for multi-source designs where two different spectra are mixed to produce a desired output color point. For example, LEDs emitting blue light may be used in combination with other sources of light, e.g., yellow light to yield a white light output. A diffuse reflective coating may eliminate the need for additional spatial color-mixing schemes that can introduce lossy elements into the system; although, in some embodiments it may be desirable to use a diffuse surface in combination with other diffusive elements. In some embodiments, the surface may be coated with a phosphor material that converts the wavelength of at least some of the light from the light emitting diodes to achieve a light output of the desired color point.
By using a diffuse white reflective material for the back reflector 416 and by positioning the light sources to emit light first toward the back reflector 416 several design goals are achieved. For example, the back reflector 416 performs a color-mixing function, effectively doubling the mixing distance and greatly increasing the surface area of the source. Additionally, the surface luminance is modified from bright, uncomfortable point sources to a much larger, softer diffuse reflection. A diffuse white material also provides a uniform luminous appearance in the output. Harsh surface luminance gradients (max/min ratios of 10:1 or greater) that would typically require significant effort and heavy diffusers to ameliorate in a traditional direct view optic can be managed with much less aggressive (and lower light loss) diffusers achieving max/min ratios of 5:1, 3:1, or even 2:1.
The back reflector 416 can comprise materials other than diffuse reflectors. In other embodiments, the back reflector 416 can comprise a specular reflective material or a material that is partially diffuse reflective and partially specular reflective. In some embodiments, it may be desirable to use a specular material in one area and a diffuse material in another area. For example, a semi-specular material may be used on the center region with a diffuse material used in the side regions to give a more directional reflection to the sides. Many combinations are possible.
In this embodiment, a small percentage, if any, of the light emitted from the sources 410 is directly incident on the lenses 404. Instead, most of the light is first redirected off of the back reflector 416. This first bounce off the back reflector 416 mixes the light and reduces imaging of any of the discrete light sources 410. However, additional mixing or other kinds of optical treatment may still be necessary to achieve the desired output profile. Thus, the lenses 404 may be designed to perform these functions as the light passes through it. The lenses 404 can comprise many different elements and materials.
In one embodiment, the lenses 404 comprise a diffusive element. A diffusive exit lens functions in several ways. For example, it can prevent direct visibility of the sources and provide additional mixing of the outgoing light to achieve a visually pleasing uniform source. However, a diffusive exit lens can introduce additional optical loss into the system. Thus, in embodiments where the light is sufficiently mixed by the back reflector 416 or by other elements, a diffusive exit lens may be unnecessary. In such embodiments, a transparent glass exit lens may be used, or the exit lens may be removed entirely. In still other embodiments, scattering particles may be included in the exit lens 104. Some embodiments may include a specular or partially specular back reflector. In such embodiments, it may be desirable to use a diffuse exit lens.
Diffusive elements in the lenses 404 can be achieved with several different structures. A diffusive film inlay can be applied to the top- or bottom-side surface of the lenses 404. It is also possible to manufacture the lenses 404 to include an integral diffusive layer, such as by coextruding the two materials or by insert molding the diffuser onto the exterior or interior surface. A clear lens may include a diffractive or repeated geometric pattern rolled into an extrusion or molded into the surface at the time of manufacture. In another embodiment, the exit lens material itself may comprise a volumetric diffuser, such as an added colorant or particles having a different index of refraction, for example.
In other embodiments, the lenses 404 may be used to optically shape the outgoing beam with the use of microlens structures, for example. Microlens structures are discussed in detail in U.S. patent application Ser. No. 13/442,311 to Lu, et al., which is commonly assigned with the present application to CREE, INC. and incorporated by reference herein.
There are many different light subassembly configurations that can be used to provide an asymmetrical light output distribution. Several such configurations are discussed in U.S. patent application Ser. No. ______ titled “LINEAR SOLID STATE LIGHTING FIXTURE WITH ASYMMETRIC DISTRIBUTION” to Durkee et al., filed on [DATE], which is commonly owned with the present application by Cree, Inc. and incorporated by reference herein.
The two subassemblies 1102, 1104 are attached with a hook-and-eye mechanism with the lighting subassembly 1104 comprising a hook 1114 and the housing subassembly comprising the receiving eye 1116. In another embodiment, the hook can be a component of the housing subassembly, and the eye a component of the lighting subassembly.
a-c show perspective views of the fixture 1100 during various stages of installation. In
a-c are perspective views of an embodiment of a modular lighting fixture 1400. The fixture 1400 comprises a housing subassembly 1402 and a lighting subassembly 1404 that are removably attached. In this particular embodiment, the end caps 1406 are separate components rather than an integral part of either subassembly. The fixture 1400 can be mounted to a wall (
The driver electronics 1412 are mounted to an interior surface 1414 of the lighting subassembly 1404. The interior surface 1414 can accommodate other electronic components as necessary. When the subassemblies 1402, 1404 are attached, the components on the interior surface 1414 of the lighting assembly 1404 fold into the space hollow space within the housing assembly 1402. Several knockouts 1416 are disposed along the housing subassembly 1402. The knockouts 1416 can be removed to feed wiring into the housing subassembly 1402 for connection with the driver electronics 1412.
a-c show perspective views of an end cap 1700 that may be used in embodiments of present invention. The end cap 1700 attaches to the ends of fixtures similar to the fixture 1400. The end cap 1700 comprises knockout portions 1702 that may be removed to provide a pathway for wires running into the fixture housing.
a-c shows an embodiment of an extended modular fixture 1800.
It is understood that embodiments presented herein are meant to be exemplary. Embodiments of the present invention can comprise any combination of compatible features shown in the various figures, and these embodiments should not be limited to those expressly illustrated and discussed. Many other versions of the configurations disclosed herein are possible. Thus, the spirit and scope of the invention should not be limited to the versions described above.
