Patent Publication Number: US-2015085466-A1

Title: Low profile led-based lighting arrangements

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This present application claims the benefit of priority to U.S. Provisional Application No. 61/881,886, filed on Sep. 24, 2013, which is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     This invention relates to LED-based lighting arrangements that utilize a remote photoluminescence wavelength conversion component to generate a desired color of light. In particular, although not exclusively, embodiments of the invention concern low profile LED lighting arrangements such as for example down lights or under cabinet lamps. 
     White light emitting LEDs (“white LEDs”) are known and are a relatively recent innovation. It was not until LEDs emitting in the blue/ultraviolet part of the electromagnetic spectrum were developed that it became practical to develop white light sources based on LEDs. As taught, for example in U.S. Pat. No. 5,998,925, white LEDs include one or more one or more photoluminescent materials (e.g., phosphor materials), which absorb a portion of the radiation emitted by the LED and re-emit light of a different color (wavelength). Typically, the LED chip or die generates blue light and the phosphor(s) absorbs a percentage of the blue light and re-emits yellow light or a combination of green and red light, green and yellow light, green and orange or yellow and red light. The portion of the blue light generated by the LED that is not absorbed by the phosphor material combined with the light emitted by the phosphor provides light which appears to the eye as being nearly white in color. Alternatively, the LED chip or die may generate ultraviolet (UV) light, in which phosphor(s) to absorb the UV light to re-emit a combination of different colors of photoluminescent light that appear white to the human eye. 
     Due to their long operating life expectancy (&gt;50,000 hours) and high luminous efficacy (70 lumens per watt and higher) high brightness white LEDs are increasingly being used to replace conventional fluorescent, compact fluorescent and incandescent light sources. 
     Typically the phosphor material is mixed with light transmissive materials, such as silicone or epoxy material, and the mixture applied to the light emitting surface of the LED die. It is also known to provide the phosphor material as a layer on, or incorporate the phosphor material within, an optical component, a phosphor wavelength conversion component, that is located remotely to the LED die (“remote phosphor” LED devices). 
     There are many types of lighting devices in modern lighting applications for which it may be desired to implement as LED-based lights. One type of lighting device is a downlight, which is often also referred to as a recessed light, pot light, or canister light. These lighting devices are implemented as light fixtures which are often installed into a ceiling and emit light in a downwards direction. 
     There are generally two main parts to conventional downlights, which include the housing and the trim. The housing is the portion of the fixture that is installed inside the ceiling and which contains the electronics and lighting elements for the downlight. The trim is the surrounding portion of the light fixture which is visible around the central opening of the downlight. 
     The problem with conventional downlights is that, to have enough room to contain all of the necessary electronics, heat sink and lighting elements, the housing for the downlight must be designed to have a significantly large interior volume. As a result, the downlight housing must usually be formed as a relatively large cylindrical shape. 
     From an installation point of view, the design of the conventional downlight therefore often limits the usability of the light. Given the size of the housing in a conventional downlight, ceilings must have sufficient clearance in their interior heights to be able to fit the downlight housing. As a result, it is impossible to install downlights in rooms having zero or minimal interior ceiling spaces. 
     In addition, additional costs are often required to install downlights. This is because the size of the housing for conventional downlights requires relatively more work, effort, time, and expense to plan and cut large-enough holes to fit the downlight. Moreover, the size and weight of the downlight often necessitates sturdy mounting brackets to be installed to support the downlight. 
     These problems are further exacerbated when the downlight is implemented as an LED-based lighting device. This is because, to handle the amount of heat to be generated by the LED components in the light, the lighting housing must be sized even larger and heavier to include sufficient amounts of heat sinks and other heat dissipation components. 
     Therefore, it should be clear that there is a need for an improved approach to implement downlight fixtures. 
     SUMMARY OF THE INVENTION 
     Embodiments of the invention concern LED-based lighting arrangements that include an integrated lighting component that includes both a photoluminescence wavelength conversion portion and a diffusing portion. The integrated lighting component can be used to implement low-profile lighting arrangements having very small installation space requirements. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order that the present invention is better understood LED-based lighting arrangements and integrated photoluminescence wavelength conversion lighting components in accordance with the invention will now be described, by way of example only, with reference to the accompanying drawings in which like reference numerals are used to denote like parts, and in which: 
         FIGS. 1A to 1F  respectively show: a perspective top view; a side view; a top view; a sectional side view through A-A; a bottom view; and an exploded perspective top view of an LED-based lamp in accordance with an embodiment of the invention; 
         FIG. 2  shows a perspective top view of a housing of the lamp of  FIGS. 1A to 1F ; 
         FIGS. 3A ,  3 B and  3 C respectively show side, bottom and perspective bottom views of an integrated photoluminescence wavelength conversion lighting component in accordance with an embodiment of the invention; 
         FIGS. 3D and 3E  respectively show a sectional and exploded sectional views through B-B of the integrated lighting component of  FIGS. 3A to 3C ; 
         FIGS. 4A and 4B  respectively show perspective and exploded perspective views of an LED array for the lamp of the invention; 
         FIG. 5A  is a sectional view of an integrated photoluminescence wavelength conversion component in accordance with an embodiment of the invention; 
         FIG. 5B  is a sectional view of an integrated photoluminescence wavelength conversion lighting component in accordance with an embodiment of the invention; 
         FIGS. 6A and 6B  respectively show a bottom view and a sectional view through C-C of an integrated photoluminescence wavelength conversion lighting component in accordance with an embodiment of the invention; and 
         FIGS. 7A and 7B  respectively show a bottom view and a sectional view through D-D of an integrated photoluminescence wavelength conversion lighting component in accordance with an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments of the invention concern LED-based lighting arrangements that include an integrated photoluminescence wavelength conversion lighting component that includes both a wavelength conversion portion and a diffusing portion. The integrated lighting component can be used to implement low-profile lighting arrangements having very small installation space requirements. 
     Referring to  FIG. 1A  there is shown a LED-based lighting arrangement (lamp)  10  for a downlight in accordance with an embodiment of the invention. The lighting arrangement  10  is for generating light of a selected color and/or color temperature, such as for example, white light. The lighting arrangement  10  includes an integrated photoluminescence wavelength conversion lighting component  12 , hereinafter “integrated wavelength conversion component”, and a housing  14 . As can be seen in the side view of  FIG. 1B , the housing  14  comprises a low-profile structure having a very shallow depth. The interior of housing  14  includes a circular dish-shaped recess  16  having a generally planar bottom surface. The integrated wavelength conversion component  12  fits within the dished recess  16  on a top surface of the housing  14  ( FIG. 1D ). As shown in  FIG. 3A , a set of clips/tabs  18  exists on the underside of the integrated wavelength conversion component  10 , where the clips/tabs  18  extends through and resiliently engage with a set of corresponding apertures  20  ( FIG. 1F ) on the base of the dished shaped opening  16  to attach the integrated wavelength conversion component  12  to the housing  14 . 
     The housing  14  further includes a bezel  22  that extends outwards in an annular arrangement from the upper portion of the housing  14 . The  22  bezel may be integrally formed into the material of the housing  14 . Alternatively, the bezel  22  may be implemented as a component that is separately manufactured from housing  14 , but affixed to housing  14  as part of the overall lighting arrangement  10 . 
       FIG. 1C  is a top view of the lighting arrangement  10  and  FIG. 1D  is a sectional view at Section A-A. A plurality of LEDs  24  is placed in an annular array on the bottom surface of the dish shaped recess  16 . The array of LED chips  24  can be implemented, for example, using Gallium Nitride-based chips, which are operable to produce light, radiation, preferably of wavelength in a range 300 to 500 nm, and more preferably to generate blue light with a dominant wavelength of 455 nm-465 nm. The LEDs  24  can be configured as an array, e.g., in an annular array and/or oriented such that their principle emission axis is parallel with the projection axis of the lamp. 
     The LED chips  24  are mounted onto a substrate  26 . In some embodiments, the substrate  26  comprises an annular MCPCB (Metal Core Printed Circuit Board). As is known, a MCPCB comprises a layered structure composed of a metal core base, typically aluminum, a thermally conducting/electrically insulating dielectric layer and a copper circuit layer for electrically connecting electrical components in a desired circuit configuration. The metal core base of the MCPCB  26  is mounted in thermal communication with the floor of the recess  16 , e.g., with the aid of a thermally conducting compound such as for example a material containing a standard heat sink compound containing beryllium oxide or aluminum nitride. As shown in  FIGS. 4A and 4B , a light reflective annular mask  28  can be provided overlaying the MCPCB that includes apertures  30  corresponding to each LED  24  to maximize light emission from the lighting arrangement. 
       FIG. 1F  shows an exploded perspective top view of the LED lighting arrangement  10 , showing the order and configuration of components within the arrangement. The housing  14  includes a central depressed portion  16  with a toroidal/annular indentation  32  matching the shape of the circuit board  26 . The indentation  32  is configured such that when the circuit board is mounted within the indentation the top surface of the circuit board is flush with the floor of the depressed region  16 . The light reflective mask  28  is fitted over the circuit board  26 , where apertures  30  in the mask  28  are configured to allow each LED  24  to extend through a respective aperture  30 . The integrated wavelength conversion component  12  is also placed within the central recess  16  within the housing  14  and attached thereto by means of the tabs  18 . 
     A power supply housing (not shown) may be included to hold power electronics for the lamp  10 . The power supply housing could be located, for example, on the underside of housing  14  below clips  18 . Wiring from the power electronics in the power supply housing is routed to the terminal  35  on the MCPCB  26  ( FIG. 4A ) using the through-hole  33  on the housing  14  (as shown in  FIG. 2 ). 
       FIGS. 3A to 3D  are illustrations that show greater details regarding the integrated wavelength conversion component  12 . The integrated wavelength conversion component  12  comprises a light diffusive upper portion  34 , at least one wavelength conversion portion  36  including a photoluminescence material and optionally a light reflective base  38 . The base  38  includes a set of clips/tabs  18  extending from its underside. The clips/tabs  18  extends through a set of corresponding apertures  20  on the bottom of the recess  16  to attach the integrated wavelength conversion component  12  to the housing  14 . 
     In one embodiment, the light diffusive top portion  34  of the integrated wavelength conversion component  12  is integrally formed with the base  38 , e.g., where the integrated wavelength conversion component  12  is entirely formed of a plastics or polymer material. In an alternate embodiment, the light diffusive top portion  34  of the integrated wavelength conversion component  12  is separately formed from the base  38 , e.g., where it is desired to have the top portion  34  possess a different material from the base  38 . For example, the top portion  34  can be manufactured from a silicone material, while the base portion is formed using a more structurally stiff plastics or polymer material. This approach permits the top portion  34  to possess a “soft” feel to the human touch, while still allowing tabs  18  on base  38  to be rigid enough to supportively and affirmatively clip to housing  14 . 
     The bottom surface of the integrated wavelength conversion component  12  comprises a toroidal indentation  42  ( FIG. 3C and 3D ) having a profile that matches the arrangement of the plurality of LEDs  24 . As indicated the indentation  42  has a profile that is substantially semicircular such that the indentation is toroidal in form comprises a half torus. Provided in the indentation  42  within the integrated wavelength conversion component  12  is a layer of photoluminescence material  36 . 
     In some embodiments, the photoluminescence materials comprise phosphor materials. For the purposes of illustration only, the following description is made with reference to photoluminescence materials embodied specifically as phosphor materials. However, the invention is applicable to any type of photoluminescence material, such as either phosphor materials or quantum dots. A quantum dot is a portion of matter (e.g. semiconductor) whose excitons are confined in all three spatial dimensions that may be excited by radiation energy to emit light of a particular wavelength or range of wavelengths. 
     The one or more phosphor materials can include an inorganic or organic phosphor such as for example silicate-based phosphors, aluminate-based phosphors, aluminate-silicate phosphors, nitride phosphors, sulfate phosphor, oxy-nitrides and oxy-sulfate phosphors or garnet materials (YAG). Examples of silicate-based phosphors are disclosed in United States patents U.S. Pat. No. 7,575,697 B2 “Silicate-based green phosphors”, U.S. Pat. No. 7,601,276 B2 “Two phase silicate-based yellow phosphors”, U.S. Pat. No. 7,655,156 B2 “Silicate-based orange phosphors” and U.S. Pat. No. 7,311,858 B2 “Silicate-based yellow-green phosphors”. Examples of aluminate materials are disclosed in United States patents U.S. Pat. No. 7,541,728 B2 “Novel aluminate-based green phosphors” and U.S. Pat. No. 7,390,437 B2 “Aluminate-based blue phosphors”. An example of an aluminate-silicate phosphor is disclosed in United States patent U.S. Pat. No. 7,648,650 B2 “Aluminum-silicate orange-red phosphor”. Examples of nitride-based red or green phosphor materials include those disclosed in co-pending United States patent applications: US 2012/0043503 A1 “Europium-Activated, Beta-SiAlON Based Green Phosphors”, US2009/0283721 A1 “Nitride-based red phosphors”, US2013-0234589 “Red-Emitting Nitride-Based Phosphors”, US 2013/0168605 A1 “Nitride Phosphors with Interstitial Cations for Charge Balance” and United States patent U.S. Pat. No. 8,274,209 B2 “Nitride-based red-emitting in RGB (red-green-blue) lighting systems”. The entire content of each of the afore-referenced applications and patents is incorporated herein by way of reference thereto. It will be appreciated that the phosphor material is not limited to the examples described and can include any phosphor material as known in the art. 
     Quantum dots can comprise different materials, for example cadmium selenide (CdSe). The color of light generated by a quantum dot is enabled by the quantum confinement effect associated with the nano-crystal structure of the quantum dots. The energy level of each quantum dot relates directly to the size of the quantum dot. For example, the larger quantum dots, such as red quantum dots, can absorb and emit photons having a relatively lower energy (i.e. a relatively longer wavelength). On the other hand, orange quantum dots, which are smaller in size can absorb and emit photons of a relatively higher energy (shorter wavelength). Additionally, daylight panels are envisioned that use cadmium-free quantum dots and rare earth (RE) doped oxide colloidal phosphor nano-particles, in order to avoid the toxicity of the cadmium in the quantum dots. 
     Examples of suitable quantum dots include: CdZnSeS (cadmium zinc selenium sulfide), Cd x Zn 1-x  Se (cadmium zinc selenide), CdSe x S 1-x  (cadmim selenium sulfide), CdTe (cadmium telluride), CdTe x S 1-x  (cadmium tellurium sulfide), InP (indium phosphide), In x Ga 1-x  P (indium gallium phosphide), InAs (indium arsenide), CuInS 2  (copper indium sulfide), CuInSe 2  (copper indium selenide), CuInS x Se 2-x  (copper indium sulfur selenide), Cu In x Ga 1-x S 2  (copper indium gallium sulfide), CuIn x Ga 1-x Se 2  (copper indium gallium selenide), CuIn x Al 1-x  Se 2  (copper indium aluminum selenide), CuGaS 2  (copper gallium sulfide) and CuInS 2x ZnS 1-x  (copper indium selenium zinc selenide). 
     The quantum dots material can comprise core/shell nano-crystals containing different materials in an onion-like structure. For example, the above described exemplary materials can be used as the core materials for the core/shell nano-crystals. The optical properties of the core nano-crystals in one material can be altered by growing an epitaxial-type shell of another material. Depending on the requirements, the core/shell nano-crystals can have a single shell or multiple shells. The shell materials can be chosen based on the band gap engineering. For example, the shell materials can have a band gap larger than the core materials so that the shell of the nano-crystals can separate the surface of the optically active core from its surrounding medium. In the case of the cadmiun-based quantum dots, e.g. CdSe quantum dots, the core/shell quantum dots can be synthesized using the formula of CdSe/ZnS, CdSe/CdS, CdSe/ZnSe, CdSe/CdS/ZnS, or CdSe/ZnSe/ZnS. Similarly, for CuInS 2  quantum dots, the core/shell nanocrystals can be synthesized using the formula of CuInS 2 /ZnS, CuInS 2 /CdS, CuInS 2 /CuGaS 2 , CuInS 2 /CuGaS 2 /ZnS and so on. 
     In operation, the light emitted by the LEDs  24  is converted by the photoluminescence material  36  into photoluminescence light. The color quality of the final light emission output of the lighting arrangement is based (at least in part) upon the combination of the wavelength of the photoluminescence light emitted by the photoluminescence material  36  with the wavelength of any remaining, unconverted, light from the LEDs  24  that passes through the photoluminescence material  36 . The color of light emitted from the lighting arrangement can be controlled by appropriate selection of the photoluminescence material composition as well as the thickness of the photoluminescence material layer which will determine the proportion of output light originating from the photoluminescence material. 
     The low-profile nature of LED lighting arrangement  10  solves the above-described problems inherent with conventional downlights. As discussed above, one problem with conventional downlights is that, to have enough room to contain all of the necessary electronics and lighting elements, the housing for the downlight must be designed to have a significantly large volume in its interior. As a result, the downlight housing must usually be formed as a relatively large cylindrical shape. This therefore limits the usability of the conventional downlight, in rooms having zero or minimal interior ceiling spaces. In contrast, the inventive embodiment of a downlight described herein provides a form factor having a very shallow depth. The inventive downright is therefore installable in almost any ceiling, even ceilings having the only minimal clearance spaces. 
     In addition, additional costs are often required to install conventional downlights, since extensively large holes must be planned and cut to fit the downlight. With the inventive downlight, only relatively small, shallow indentations are required to be formed to fit the small depth of housing to install the downlight. 
     Moreover, the size and weight of the downlight often necessitates sturdy mounting brackets to be installed to support the downlight. Here, the much smaller mass and size of the LED lighting arrangement  10  allows for much smaller brackets to be used to mount the LED lighting arrangement  10 . 
     Conventional downlights can often require the presence of very large heat sinks and other heat dissipation components. The relative size and configuration of the housing  14  with its bezel  22  permits these structures to adequately function as the heat dissipation components for the LED lighting arrangement  10 . In an alternate embodiment, additional heat sinks may also be included within the LED lighting arrangement  10 . 
     Another advantage of the present approach is that the integrated wavelength conversion component  12  can be formed as the final stage optic for the lighting arrangement  10 , which is directly visible to viewers of the light. This means that no additional lens or cover is needed to be manufactured and affixed over the arrangement to produce a final lighting product. 
     It is noted that the current embodiment functions as a remote phosphor lighting arrangement, whereby the photoluminescence (phosphor) material layer  36  is spaced apart from the LEDs  24 . This arrangement also serves to assist in effecting more efficient thermal management for the LED lighting arrangement  10 , since the heat generation is not concentrated at the circuit board  26 , as would be the case if a phosphor encapsulated LED located at the circuit board is provided to generate light. 
     One problem associated with LED lighting device that is addressed by embodiments of the invention is the non-white color appearance of the device in an “OFF-state”. During an “ON-state”, the LED chip or die generates blue light and some portion of the blue light is thereafter absorbed by the phosphor(s) to re-emit yellow light (or a combination of green and red light, green and yellow light, green and orange or yellow and red light). The portion of the blue light generated by the LED that is not absorbed by the phosphor combined with the light emitted by the phosphor provides light which appears to the human eye as being nearly white in color. However, in an OFF-state, the LED chip or die does not generate any blue light. Instead, light that is produced by the remote phosphor lighting apparatus is based at least in part upon external light (e.g. sunlight or room lights) that excites the phosphor material in the wavelength conversion component, and which therefore generates a yellowish, yellow-orange or orange color in the photoluminescence light. Since the LED chip or die is not generating any blue light, this means that there will not be any residual blue light to combine with the yellow/orange light from the photoluminescence light of the wavelength conversion component (e.g. phosphor  36 ) to generate white appearing light. As a result, the lighting device will appear to be yellowish, yellow-orange or orange in color. This may be undesirable to the potential purchaser or customer that is seeking a white-appearing light. 
     According to some embodiments, a light diffusing material can be distributed within the material of upper portion  34  the integrated wavelength conversion component  12 , providing the benefit of improving the visual appearance of the device in an OFF-state to an observer. In part, this is because the light diffusing material can substantially reduce the passage of external excitation light that would otherwise cause the wavelength conversion component to re-emit light of a wavelength having a yellowish/orange color. The particles of a light diffractive material are selected, for example, to have a size range that increases its probability of scattering blue light, which means that less of the external blue light passes through the light diffusing layer to excite the wavelength conversion layer. Therefore, the remote phosphor lighting apparatus will have more of a white appearance in an OFF-state since the wavelength conversion component is emitting less yellow/red light. 
     The light diffractive particle size can be selected such that the particles will scatter blue light relatively more (e.g. at least twice as much) as they will scatter light generated by the phosphor material. Such a light diffusing materials ensures that during an OFF-state, a higher proportion of the external blue light received by the device will be scattered and directed by the light diffractive material away from the wavelength conversion layer  36 , decreasing the probability of externally originated photons interacting with a phosphor material particle and minimizing the generation of the yellowish/orange photoluminescent light. However, during an ON-state, phosphor generated light caused by excitation light from the LED light source can nevertheless pass through the diffusing material layer with a lower probability of being scattered. Preferably, to enhance the white appearance of the lighting device in an OFF-state, the light diffractive material within the light diffusing layer is a “nano-particle” having an average particle size of less than about 150 nm. For light sources that emit lights having other colors, the nano-particle may correspond to other average sizes. For example, the light diffractive material within the light diffusing layer for an UV light source may have an average particle size of less than about 100 nm. 
     Therefore, by appropriate selection of the average particle size of the light scattering material, it is possible to configure the lamp such that it scatters excitation light (e.g. blue light) more readily than other colors, namely green and red as emitted by the photoluminescence materials. For example, TiO 2  particles with an average particle size of 100 nm to 150 nm are more than twice as likely to scatter blue light (450 nm to 480 nm) than they will scatter green light (510 nm to 550 nm) or red light (630 nm to 740 nm). As another example, TiO 2  particles with an average particle size of 100 nm will scatter blue light nearly three times (2.9=0.97/0.33) more than it will scatter green or red light. For TiO 2  particles with an average particle size of 200 nm these will scatter blue light over twice (2.3=1.6/0.7) as much as they will scatter green or red light. In accordance with some embodiments of the invention, the light diffractive particle size is preferably selected such that the particles will scatter blue light relatively at least twice as much as light generated by the phosphor material(s). 
     Another problem with remote phosphor devices that can be addressed by embodiments of the invention is the variation in color of emitted light with emission angle. This problem is commonly called COA (Color Over Angle). Remote phosphor layers allow a certain amount of blue light to escape as the blue component of white light. This is directional light coming from the LEDs. The RGY (Red Green Yellow) light coming from the phosphor is lambertian. Therefore the directionality of the blue light may be different than that of the RGY light causing a “halo” effect at the edges with color looking “cooler” in the direction of the blue LED light and  “ warmer” at the edges where the light is all RGY. The addition of nano-diffuser selectively diffuses blue light—causing it to have the same lambertian pattern as the RGY light and creating a very uniform color over angle. Traditional LEDs also have this problem which can be improved by remote phosphor using this technology. Remote phosphor devices are often subject to perceptible non-uniformity in color when viewed from different angles. Embodiments of the invention correct for this problem, since the addition of a light diffusing layer in direct contact with the wavelength conversion layer significantly increases the uniformity of color of emitted light with emission angle θ. 
     Embodiments of the present invention can be used to reduce the amount of phosphor materials that is required to manufacture an LED lighting product, thereby reducing the cost of manufacturing such products given the relatively costly nature of the phosphor materials. In particular, the addition of a light diffusing material can substantially reduce the quantity of phosphor material required to generate a selected color of emitted light. This means that relatively less phosphor is required to manufacture a wavelength conversion component as compared to comparable prior art approaches. As a result, it will be much less costly to manufacture lighting apparatuses that employ such wavelength conversion components, particularly for remote phosphor lighting devices. In operation, the diffusing layer increases the probability that a photon will result in the generation of photoluminescence light by reflecting light back into the wavelength conversion layer. Therefore, inclusion of a diffusing layer with the wavelength conversion layer can reduce the quantity of phosphor material required to generate a given color emission product, e.g. by up to 40%. 
     Alternative approaches can be taken to improve the off-state white appearance of the lamp. For example, texturing can be incorporated into the exterior surface of the integrated component  10  to improve the off-state white appearance of the lamp. 
     Further details regarding an exemplary approach to implement scattering particles are described in U.S. patent application Ser. No. 11/185,550, filed on Oct. 13, 2011, entitled “Wavelength Conversion Component With Scattering Particles”, which is hereby incorporated by reference in its entirety. 
     A cavity is formed in the space between the LEDs  24  and the phosphor layer  36 , which is hereby referred to herein as a “mixing chamber”. The volume of the mixing chamber is large enough to permit the LED  24  to be located, wholly or partially, within the interior of the mixing chamber. A benefit provided by this arrangement is that the chamber provides for mixing of light within highly transparent solid with minimal loss. An example of this occurs when a lamp includes both red and blue LEDs in the chamber, and the chamber allows the light from these LEDs (e.g., the red light) to be uniformly distributed. 
     There are various reasons for the advantages provided by the internal mixing chamber. For example, one reason is because the arrangement of the internal mixing chamber provides for cross-wall emissions of light. Even though a light reflective surface  28  are still provided on the “floor” of the lighting arrangement, much of the light that moves through the mixing chamber will cross from one wall of the phosphor to another wall without needing to reflect from the reflectors, improving the efficiency of the lamp for its light production. Another benefit provided by the arrangement is that it removes the point source impact of having individual LEDs in the lighting arrangement. Each LED is a point source of light (e.g., blue or red light), but because the LEDs are within the chamber that has its walls covered with phosphor, the light emitted by the phosphor will visibly obscure the point source effects of the LEDs. Yet another advantage is the directionality provided by the current arrangement. Since the inventive lighting arrangement  10  will likely be inserted into ceiling or wall fixtures, it is likely that the emitted light will be provided in a desired direction, e.g., away from the ceiling or wall. The present embodiment of using the lens and internal chamber configuration enhances the directionality of the emitted light in the desired directions. Another benefit provided by embodiments of the invention is that the amount of phosphor needed to manufacture the lamp can be minimized for a given size of the lighting arrangement. Even though the external dimensions of the lighting arrangement may be quite large due to the size of the lens, the smaller surface area of the internal chamber means that a much smaller amount of phosphor is actually required for the lighting arrangement. A further benefit of the small internal chamber is that it reduces the apparent size of the phosphor component  36  when viewing the lighting arrangement in an OFF-state. 
     Each of the LEDs  24  may be covered or otherwise encapsulated or the mixing chamber  42  filled with a light extracting cover/encapsulant  44 . The light extracting cover  44  reduces the mismatch between the index of refraction of the LEDs  24  and the index of refraction of the air within the interior mixing chamber  42  between the LEDs  24  and the phosphor layer  36 . Any mismatch in the indices of refraction can cause a significant portion of the LED light to be lost from the total LED light output. By including light extracting cover  42 , this helps to reduce excessive mismatches in the indices of refraction, facilitating an increase the overall light conversion efficiency of lighting arrangement  10 . 
     In some embodiments, the light diffuser portion  34  in direct contact with photoluminescence material region  36  within the integrated wavelength conversion component  12 . The mean refractive index of the light diffuser portion  34  and photoluminescence regions  36  is approximately 1.4 to 1.55 in some embodiments. The refractive indices of the two regions  34  and  36  preferably match within 0.2, where the refractive index of polymer materials that can be used is in the in typical range 1.35 to 1.6 in some embodiments. 
     Assume that the surface area of the exterior light emitting surface of the light diffusive portion  34  is represented as SA 1  mm 2 . Further assume that the total exterior light emitting surface area of photoluminescence regions  36  is represented as SA 2  mm 2  (e.g., the area that is in contact with the diffuser portion). To ensure good OFF-State white appearance SA 1  is at least three times the amount of SA 2 , and is preferably at least five times the amount in some embodiments. The minimum distance t between the exterior of the phosphor region  36  and exterior surface of diffuser portion  34  (shown in  FIG. 3D ) is at least 3 mm, where the minimum is typically at least 5 mm in some embodiments. 
     The overall diameter of the integrated wavelength conversion component  12  is preferably greater about 25 mm, and more typically is greater than about 50 mm. The depth of the integrated wavelength conversion component  12  can be configured to be in the range from 5-20 mm in some embodiments. In one embodiment, the integrated wavelength conversion component  12  has a diameter of approximately 76 mm (3 inches) and a depth of approximately 12 mm (0.47 inches) with a surface area of the diffusing portion at 11,850 mm 2  and the surface area of the phosphor region at 4475 mm 2 . 
     In one embodiment, the diffusion portion corresponds to the following: 
     Mass=40.11 grams 
     Volume=40109.31 cubic millimeters 
     Surface area=11851.31 square millimeters 
     In one embodiment, the phosphor portion corresponds to the following: 
     Mass=2.12 grams 
     Volume=2117.99 cubic millimeters 
     Surface area=4475.36 square millimeters 
     In some embodiments, as shown in  FIG. 5A , further operating efficiencies for the arrangement  10  are provided by filling the mixing chamber  42  with an optical medium  44 . The optical medium  44  within the chamber comprises a material, e.g., a solid material, possessing an index of refraction that more closely matches the index of refraction for the phosphor  36 , the LEDs  24 , and/or any type of encapsulating material  44  that may exist on top of the LEDs  24 . One reason for using the optical medium is to eliminate air interfaces that exist between the LEDs  24  and the phosphor  36 . The problem addressed by this embodiment is that there is a mismatch between the index of refraction of the material of the phosphor  36  and the index of refraction of the air within the interior volume of the mixing chamber. This mismatch in the indices of refraction for the interfaces between air and the lamp components may cause a significant portion of the light to be lost. As a result, lesser amounts of light and excessive amounts of heat are generated for a given quantity of input power. By filling the mixing chamber with an optical medium  44 , this approach permits light to be emitted to, within, and/or through the interior volume of the lamp without having to incur losses caused by excessive mismatches in the indices of refraction for an air interface. The optical medium may be selected of a material, e.g. silicone, to generally fall within or match the index of refraction for materials typically used for the phosphor  36 , the LEDs  24 , and/or any encapsulating material that be used to surround the LEDs  24 . Further details regarding an exemplary approach to implement the optical medium are described in U.S. application Ser. No. 13/769,210, filed on Feb. 15, 2013, entitled “Solid-State Lamps With Improved Emission Efficiency And Photoluminescence Wavelength Conversion Components Therefor”, which is hereby incorporated by reference in its entirety. 
     As shown in  FIG. 3D , the phosphor layer  36  is formed in the toroidal indentation in the top portion  34  of the integrated wavelength conversion component  12 , where the phosphor layer comprises a cross-sectional profile having a shape that is dome-like, generally ellipsoidal, candle-like, and/or conical shape. Each of these shapes provides advantageous performance benefits under different circumstances. For example, the approach of using the dome-shaped cross-sectional profile provides a more uniform pattern in the near field (at or near the tube surface) light distribution and better far field beam control. The conical sectional shape provides a greater distribution of light along the sides of the lamp. In contrast, the dome-shaped sectional profile of provides a greater distribution of light towards the top of the lamp. This highlights the ability to shape the light produced by the lamp by configuring the shape of the sectional profile of the phosphor/chamber. The approach of using the dome-shaped cross-sectional profile generally corresponds to less phosphor surface area than the cone-shaped sectional profile. 
     The arrangement of the lamp can also be configured to improve its light producing efficiency (also referred to herein as “System Quantum Efficiency” or SQE) and to reduce SQE light loss, where system quantum efficiency can be defined as the ratio of the total number of photons produced by the system to the number of photons generated by the LED. Many white LEDs and LED arrays are typically constructed of blue LEDs encapsulated with a layer of silicone containing particles of a powdered phosphor material or covered using an optical component (optic) including the phosphor material. The system quantum efficiency (SQE) of the known white LED and LED arrays is negatively affected by the loss of the total light output of the lamp during conversion of the blue LED light to white light, where the majority of light loss is not due to the photoluminescence conversion process but rather due to absorption losses for light (both photoluminescence and LED light) that is emitted back into the LED(s). Due to the photoluminescence conversion process being isotropic, photoluminescence light will be emitted in all directions and hence up to about 50% will be generated in a direction back towards the LED(s) giving rise to re-absorption and loss of photoluminescence light by the LED(s). Therefore, by appropriately configuring the aspect ratio of the phosphor portion  36 , it is possible to eliminate or significantly reduce the SQE losses of the lamp. The aspect ratio of the phosphor portion  36  is the ratio of the area of the phosphor layer to the area of the LED package. 
     According to some embodiments of the invention, SQE loss is significantly eliminated or reduced by implementing the following combination of factors: 
     i) remote phosphor—the phosphor portion is separated from the LEDs; 
     ii) a coupling optic—An optical material having a high refractive index material is coupled directly to LEDs and the phosphor conversion component. This material should have a refractive index of 1.4 or greater (&gt;1.5 preferred). Good optical coupling between the blue LEDs and the clear optic is used to ensure that it effectively acts as a light transport layer. By eliminating air interfaces and refractive index mismatches, virtually all light generated by the LEDs will travel with virtually no or minimal loss to the wavelength conversion component (phosphor layer). 
     iii) phosphor wavelength conversion layer with an aspect ratio for the cross-sectional profile that is greater than 1:1—the phosphor layer is separated from the blue LEDs by the clear coupling optic. Ideally the outer phosphor optic is the same refractive index as the clear layer and has no gap or other optical loss in the interface to the clear optic. The phosphor outer layer optic has an aspect ratio of 1:1 or greater such that the total surface area of the outer phosphor layer in contact with the clear coupling optic is at least three times the area of the LED package surface coupled to the clear coupling optic. 
     In operation blue light travels through the clear coupling optic with effectively no loss. When the blue light excites the phosphor layer and the photoluminescence light can now travel equally in any direction due to the elimination of the optical medium/air interface. Due to the high aspect ratio of the photoluminescence wavelength conversion component a majority of light (both phosphor generated light and scattered LED light) will not travel back to the LED package. Instead most light will travel through the clear optic to the other side and exit out of the phosphor layer on the opposing side. Once converted, YGR (Yellow, Green, Red) light easily passes through the phosphor layer. In summary, the majority of light is no longer re-cycled directly between the phosphor and the package/LEDs as it is in standard LED configurations. 
       FIG. 5B  illustrates an alternative embodiment. In this embodiment, the mixing chamber within indentation  42  is filled with a medium  40 , where the medium  40  includes phosphor material. Unlike the approach of  FIG. 5A , a separate layer of phosphor  36  is not used that is remote to the LEDs  24 . Instead, the phosphor material is distributed within the medium  40  that surrounds the LEDs  24 . 
     Both of the arrangements of  FIGS. 5A and 5B  result in a light engine in which the LEDs  24  are incorporated within the integrated wavelength conversion component. In particular, the LEDs  24  are positioned within the mixing chamber formed by toroidal indentation  42 . 
     Referring to  FIG. 3D  there is shown a preferred method of fabricating the integrated component  12  in accordance with some embodiments of the invention. The top light diffusing portion  34  is provided having an indented portion  42  on its underside. A layer of phosphor  36  is deposited or otherwise injection molded into the indented portion  42 . After the phosphor has been deposited, the top portion  34  can be affixed to the light reflective base  38 . 
     Any suitable manufacturing process may be employed to manufacture the integrated wavelength conversion component  12 . For example, a molding process can be used to form the light diffusive portion  34 . The phosphor layer  36  can be formed using any suitable approach. For example, a spray coating or printing process can be employed where ink is coated directly within the surface of the indentation  42  in the underside of the light diffusive portion  34 . Molding may also be used to mold the phosphor layer. Lamination can also be performed to manufacture the phosphor layer. 
     Numerous alternative configurations can be employed within the scope of the invention to implement the integrated wavelength conversion component  12 , housing  14 , and/or overall configuration of the lamp  10 . For example, the above-described embodiments disclose an integrated wavelength conversion component  12  where the phosphor  36  is incorporated in a single toroidal indentation  42  that forms a circular profile that matches the circular shape of the integrated wavelength conversion component  12 . However, the invention is also applicable to implement an integrated wavelength conversion component  12  that has a different configuration for the number, shape or orientation of the indentation  42  and/or phosphor layer  36 . 
       FIGS. 6A and 6B  illustrate an alternative form of integrated wavelength conversion component  12  having a plurality (e.g., eight) of photoluminescence wavelength conversion regions  36   a  to  3   h  in which each region extends in a radial direction similar to spokes of a wheel. Each of the regions  36   a  to  3   h  comprises an indentation  42  having a layer of phosphor deposited therein. The photoluminescence wavelength conversion regions  36   a  to  3   h  overlays a respective LED array. Within  FIG. 6A , solid dots  48  indicate the location of the LEDs  24 . 
       FIGS. 7A and 7B  illustrate an alternative form for the integrated wavelength conversion component  12 . In this embodiment, the integrated wavelength conversion component  12  includes multiple (e.g., two) concentric photoluminescence wavelength conversion regions  36   a  and  36   b.  As noted above, the photoluminescence wavelength conversion regions do not need to be circular in shape. Here, the photoluminescence wavelength conversion regions  36   a  and  36   b  within integrated wavelength conversion component  12  are shaped to be generally square in shape, and are concentric such that one is smaller and located within the boundaries of the other. Each of the regions  36   a  and  36   b  overlays a respective LED array. Within  FIG. 7A , the solid dots  48  indicate the location of the LEDs  24 . 
     It will be appreciated that the invention is not limited to the exemplary embodiments described and that variations can be made within the scope of the invention.