Abstract:
A system of variable color landscape lights illuminated by multiple light emitting diode chips provides the user a controllable spectral output. In its various configurations, the electronic control system allows a selection of various spectral light radiation. The color output of the light emitting diode chips is electronically controlled and can be changed by means of a push button switch, radio frequency control, infrared control, signals impressed on line voltages, and other control system means.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit of priority from U.S. Patent Application entitled “Electronically Controlled, Variable Color Landscape Lighting Using Multiple Light Emitting Diode Chips on a Printed Circuit Support Member,” filed Oct. 23, 2002, application Ser. No. 10/278,699, now abandoned, which is incorporated herein by reference in its entirety. 
   BACKGROUND 
   The present disclosure relates generally to lighting systems and more particularly to landscape lighting systems. 
   Color enhancement of trees, planting beds, buildings, signage, driveways, sidewalks, landscaped paths, and the like may be desired for its aesthetically pleasing decorative effects and visual interest, as well as for seasonal accent. Red, white and blue colors may be favored for July 4 th  celebrations, red and green for end of the year holidays, pastels for Easter, and orange for Halloween. Also, as a replacement for glaring white light, when a choice is offered, muted colors may be preferred and equally effective in many safety related navigation-assisting applications around commercial and residential structures. Incandescent, fluorescent and T-1¾ LED assemblies are currently used in the illumination of landscape features, walkways, driveways, signage and buildings for decorative and safety enhancement purposes. Should color accent be desired, color control for white incandescent and fluorescent lights can be accomplished by bulb exchange or through the use of colored filters. Changing colors would require additional bulb and filter exchange. Such color control is labor intensive and requires the storage and handling of numerous spare/replacement parts. Using single or multiple light emitting diodes (LED) assemblies, color change can be achieved by means of multiple switches that control multiple colored LED assemblies. 
   BRIEF SUMMARY OF THE DISCLOSURE 
   The methods and techniques disclose an electronically controlled landscape lighting system that uses multiple light emitting diode chips to provide rapid color change. 
   The systems and techniques described here may provide one or more of the following advantages. The light emitting diode chips can provide for long life of the illumination system when compared to incandescent systems. The light emitting diode sources have lower energy consumption than standard incandescent lighting systems with equivalent light output. An electronic controller may change the radiated color without changing bulbs or lenses. The lighting system can provide nearly instantaneous electronically controlled color-changing capability. 
   The details of one or more implementations of the invention are set forth in the accompanying drawings and the description below. Other features and advantages of the invention will become apparent from the description, the drawings, and the claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of the present disclosure in one possible use configuration. 
       FIG. 2  is a view in partial section taken generally along line  2 — 2  of  FIG. 1 . 
       FIG. 3  is a view in partial section taken generally along line  3 — 3  of  FIG. 1 . 
       FIG. 4  is an enlarged view in partial section from circle  10  of  FIG. 2 . 
       FIG. 5  is a perspective view of the present disclosure in a second possible use configuration. 
       FIG. 6  is a view in partial section taken generally along line  31 — 31  of  FIG. 5 . 
       FIG. 7  is a view in partial section taken generally along line  22 — 22  of  FIG. 5 . 
       FIG. 8  is an enlarged view in partial section from circle  43  of  FIG. 6 . 
       FIG. 9  is a perspective view of the present disclosure in a third possible use configuration. 
       FIG. 10  is a view in partial section taken generally along line  45 — 45  of  FIG. 9 . 
       FIG. 11  is an enlarged view in partial section from circle  47  of  FIG. 9 . 
       FIG. 12  flow chart for adjusting the chromaticity of light output. 
   

   Like reference numbers and designations in the various drawings indicate like elements. 
   DETAILED DESCRIPTION 
   This disclosure is for landscape lighting whereby electronically-controlled multiple light emitting diode chips  13  are mounted on a support member and controlled in such a manner to permit the selection of colors at will. Various input voltages, selected by the user (not shown), power the disclosure in its various configurations. Although the accompanying illustrations show the multiple light emitting diode chips  13  being mounted in housing configurations standard to the lighting industry such as pagoda-style ( FIGS. 1–4 ), spotlight ( FIGS. 5–8 ), and floodlight ( FIGS. 9–11 ), the housing configuration used is not critical and any type of landscape lighting fixture or other lighting fixture configuration that is made weather-resistant can be used. Color selection in the emitted light can be performed by various means, including a local push button, radio frequency controllers, signals impressed on the line voltages, infrared controllers, and/or any combination thereof. 
     FIG. 1  shows the standard apparatus  9  of the present disclosure in a first preferred embodiment of its use. As shown in  FIG. 2 , standard apparatus  9  comprises one or more light emitting diode chips  13  mounted upon at least one elongated support member  11 , support member  11  attached to an elongated heat sink  15  which provides attachment for one end of support members  11  to a cap  6 , a connector  14  attached to the opposing end of support member  11 , and an elongated screw  18  providing the attachment between heat sink  15  and connector  14 . As is further shown in  FIG. 3 , a single embodiment of the present disclosure can comprise more than one support member  11 . In  FIG. 1  standard apparatus  9  is housed within a vertically extending pagoda-like structure comprising a base  4  configured to house electronics  12  (shown in  FIG. 2 ), a substantially cylindrical lens  5 , cap  6 , and several intermediate rings  7  between cap  6  and base  4  that are evenly spaced apart from one another. The materials in the base  4 , cap  6 , and rings  7  are preferably plastic or metal and the material in the lens  5  is preferably plastic or glass, although each may also be made from other materials or combinations of materials. FIG.  1  further shows wires  8  entering the lower portion of base  4 . Wires  8  may be of any standard AWG sufficient to carry the current necessary to power the electronics  12  and the light emitting diode chips  13  (shown in  FIGS. 2–4 ) mounted on the support member  11  of standard apparatus  9 . The light emitting diode chips  13  used in the first preferred embodiment of the present disclosure are of the type whereby each chip  13  emits light of a given color, typically red, green, or blue. A full spectrum of color is achieved via excitation of differing combinations of the light emitting diode chips  13  present. Thus, color change in the total light output of the light emitting diode chips  13  is accomplished by means of programming electronics  12  to excite selected light emitting diode chips  13 . Although not limited thereto, in the present disclosure it is contemplated for such programming to be achieved through use of a momentary switch  19  that is actuated by a push button  20 , or by means electronics  12  that are sensitive to switch closure, radio frequency signals, signals imposed on the drive voltage or to infrared signals. The length, width, and height dimensions of lens  5 , cap  6 , and rings  7  are not critical, nor is the configuration of momentary switch  19  or push button  20 . Also, the configuration of base  4  is not critical as long as it provides sufficient support for lens  5  and interior space for electronics  12 . Further, the shape and size of support member  11  is not critical as long as it provides the necessary space required to support the light emitting diode chips  13 , and the shape and dimensions of heat sink  15  is not critical as long as it provides the necessary space and configuration necessary to accommodate support member  11 . 
     FIG. 2  shows the standard apparatus  9  of the first preferred embodiment of the present disclosure taken along the line  2 — 2  in  FIG. 1 , and positioning of electronics  12  and the light emitting diode chips  13  mounted on the support member  11 . As is shown in FIG.  3 , more than one support member  11  can be used. Support members  11  are preferably plastic or metallic, but not limited thereto, and held in place on one of its ends by a connector  14  and on its opposing end by a metallic heat sink  15 , which provides heat dissipation from the light emitting diode chips  13  mounted on the support member  11 . Metallic heat sink  15  and connector  14  are attached to one another by means of a screw  18 , or other mechanical means (not shown). Connector  14  provides electrical connection between the light emitting diode chips  13  mounted on the support member  11  and the electronics  12  mounted on a printed circuit board  16 . Wires  8  are connected between a remote power source (not shown) and the electronics  12  mounted on a printed circuit board  16 .  FIG. 2  also shows lens  5 , cap  6 , and intermediate rings  7 , as well as momentary switch  19  and push button  20 . The configuration of the connector  14  is not critical as long as it provides a method of electrically connecting support member  11  to the electronics  12  mounted on printed circuit board  16 . 
     FIG. 3  shows the standard apparatus  9  of the first embodiment of the present disclosure taken along the line  3 — 3  in  FIG. 1 , and details of a top view of standard apparatus  9 , whereby the light emitting diode chips  13  are shown to be mounted on three evenly spaced-apart support members  11  and are covered with a transparent protection layer  17  that protects the light emitting diode chips  13  from physical damage. Although not limited thereto, protection layer is preferably made from a transparent silicone based material.  FIG. 3  also shows metallic heat sink  15  being attached to connector  14  by means of a screw  18 , although other mechanical connection means (not shown) are also contemplated for such attachment.  FIG. 3  further shows lens  5  surrounding support members  11 , heat sink  14 , and connector  14  of standard apparatus  9 , and lens  5  being supported upon base  4 . Although three support members  11  are shown in  FIG. 3 , the number used is not critical and can vary from one to twelve, or even more, depending on the intended application. 
     FIG. 4  is an enlarged view of the circle  10  in  FIG. 2  showing in detail standard apparatus  9  having support member  11  with multiple light emitting diode chips  13  attached thereto by means of whisker wires  21 , heat sink  15 , and screw  18 . The number of light emitting diode chips  13  is not critical and any embodiment of the present disclosure may comprise one or more light emitting diode chips  13 . As the number of light emitting diode chips  13  used increases, the intensity and spectrum of color that can be achieved is expanded. Support members  11  are held in place by the metallic heat sink  15  and screw  18  on one of its ends and connector  14  on the opposing one of its ends, with connector  14  being attached to the printed circuit board  16  holding electronics  12 .  FIG. 4  further shows wires  8  extending to printed circuit board  16 , electronics  12  attached to printed circuit board  16 , and momentary switch  19  and push button  20  connected to one another. 
     FIG. 5  shows the standard apparatus  28  of the present disclosure in a second preferred embodiment of its use.  FIGS. 6 and 7  show standard apparatus  28  comprising reflecting or refracting lens  29 , circular transparent layer  40 , light emitting diode chips  13 , hexagonal support member  33 , and heat sink  35  attached between support member  33  and printed circuit board  16 , as well as a connector and wiring harness  36  providing the electrical connection between the light emitting diode chips  13  mounted on hexagonal support member  33  and the electronics  37  mounted on printed circuit board  16 . In  FIG. 5  the outer structure for standard apparatus  28  is in the form of a spotlight consisting of a substantially cylindrical base support  24 , a substantially tubular housing  26 , an attachment and directional adjustment means  25  connected between base support  24  and tubular housing  26 , and a light shield  27 . The base support  24 , attachment and directional adjustment means  25 , tubular housing  26 , and light shield  27  are preferably constructed of plastic or metal, but not limited thereto as long as the material used is at least weather-resistant. Wires  8  are shown entering the lower portion of base support  24 . Wires  8  may be of any standard AWG sufficient to carry the current necessary to power the electronics  12  and the light emitting diode chips  13  (shown in  FIG. 7 ) mounted on the hexagonal support member  33  (shown in  FIGS. 6 and 7 ) of standard apparatus  28 . Color change in the total light output of the light emitting diode chips  13  is accomplished by means of programming electronics  12 , similar to that disclosed above for  FIG. 1 . Although not limited thereto, in the present disclosure it is contemplated for such programming to be accomplished through use of a momentary switch  19  that is actuated by a push button  20 , or by means of electronics  12  (shown in  FIGS. 6 and 8 ) that are sensitive to switch closure, radio frequency signals, signals imposed on the drive voltage, or infrared signals. The length, width, diameter, and/or height dimensions of cylindrical base support  24 , attachment and directional adjustment means  25  and, light shield  27  are not critical, nor is the configuration of momentary switch  19  or push button  20 . The hexagonal configuration of the support member  33 , shown in  FIGS. 6–8  and providing support for light emitting diode chips  13 , is also not critical and may be of any suitable shape such as round, square, oblong or other as long as sufficient area is present for the attachment of light emitting diode chips  13  in sufficient quantity to produce the desired light intensity and spectrum. 
     FIG. 6  shows the standard apparatus  28  of the second preferred embodiment of the present disclosure taken along the line  31 — 31  in  FIG. 5 , and positioning of electronics  12  and the hexagonal support member  33  upon which light emitting diode chips  13  are mounted. The hexagonal configuration of support member  33  is not critical and other configurations such as but not limited to triangular, pentagonal, round, oval, square, and octagonal are also contemplated. Hexagonal support member  33  is preferably plastic or metal, but not limited thereto, and held in place by means of screw  18  to metallic heat sink  35 , which provides heat dissipation from the light emitting diode chips  13  mounted on hexagonal support member  33 . Connector and wiring harness  36  provides electrical connection between light emitting diode chips  13  mounted on hexagonal support member  33  and the electronics  12  mounted on printed circuit board  16  set in an inferior position to metallic heat sink  35 . Wires  8  extend through base support  24  and the lower portion of tubular housing  26 , and are connected between a remote power source (not shown) and the electronics  12  mounted on a printed circuit board  16 . Refracting or reflecting lens  39  gathers the light (not shown) produced by the light emitting diode chips  13  and provides focusing as required by the application. Light shield  27  also assists in directing the light produced by the light emitting diode chips  13  according to the application. In addition, circular transparent protection layer  40  protects the light emitting diode chips  13  from moisture and other environmental contaminants.  FIG. 6  also shows momentary switch  19  connected to printed circuit board  16  and push button  20  poised and ready for activation contact with momentary switch  19 . The programming of electronics  12  by means of switch  19  is not critical, and such programming may also be accomplished by means of radio frequency signals, signals imposed on the drive voltage, infrared signals, and/or other local or remote programming methods (not shown). 
     FIG. 7  shows the standard apparatus  28  of the second preferred embodiment of the present disclosure taken along the line  22 — 22  in  FIG. 5 , and details of a top view of standard apparatus  28 , with multiple light emitting diode chips  13  mounted on hexagonal support member  33 .  FIG. 7  further shows light emitting diode chips  13  covered with a circular transparent protection layer  40  that protects the light emitting diode chips  13  from moisture and other environmental contaminants. Although not limited thereto, protection layer  40  is preferably made from a transparent, curable liquid silicone material. The number of light emitting diode chips  13  used is not critical, and may include one or more light emitting diode chips  13 , with color diversity being enhanced by use of more than one light emitting diode chip  13 .  FIG. 7  also shows metallic heat sink  35  being positioned within substantially tubular housing  26 , and hexagonal support member  33  attached to heat sink  35  via two screws  18 , although other mechanical connection means (not shown), including the use of additional screws  18 , are also contemplated for such attachment.  FIG. 7  further shows the light emitting diode chips  13  attached to hexagonal support member  33  via whisker wires  21 . 
     FIG. 8  is an enlarged view of circle  43  in  FIG. 6  showing in detail standard apparatus  28  having hexagonal support member  33 , heat sink  35  in an inferior position to hexagonal support member  33  between support member  33  and printed circuit board  16 , reflecting or refracting lens  39 , circular transparent protection layer  40  positioned over the top surface of hexagonal support member  33 , as well as electronics  12  mounted on printed circuit board  16  and a connector and wiring harness  36  providing the electrical connection between the light emitting diode chips  13  mounted on hexagonal support member  33  and printed circuit board  16 . The number of light emitting diode chips  13  used under circular transparent protection layer  40  is not critical and any embodiment of the present disclosure may comprise one or more light emitting diode chips  13 .  FIG. 8  further shows wire  8  extending to electronics  12 , and momentary switch  19  connected to printed circuit board  16  and push button  20  poised and ready for activation contact with momentary switch  19 . 
     FIG. 9  shows the standard apparatus  44  of the present disclosure in a third preferred embodiment of its use.  FIGS. 10 and 11  show standard apparatus  44  comprising, an elongated substantially rectangular support member  54 , light emitting diode chips  13  mounted on a substantially rectangular support member  54 , and substantially rectangular support member  54  attached to elongated heat sink  59 , as well as a connector and wiring harness  36  providing the electrical connection between the light emitting diode chips  13  mounted on substantially rectangular support member  54  and the electronics  12  mounted on printed circuit board  16 . In  FIG. 9  the outer structure for standard apparatus  44  is in the form of a floodlight consisting of a base support  48  having a substantially cylindrical lower portion, a substantially rectangular housing  49 , a reflector/refractor  50 , and a transparent lens  57  (shown in  FIG. 10 ). The base support  48 , substantially rectangular housing  49 , and reflector/refractor  50  are preferably constructed of plastic or metal but not limited thereto and transparent lens  57  is preferably constructed of plastic or glass, but not limited thereto, as long as the materials are at a minimum weather-resistant. Wires  8  are shown entering the lower portion of base support  48 . Wires  8  may be of any standard AWG sufficient to carry the current necessary to power the electronics  12  and the light emitting diode chips  13  (shown in  FIG. 11 ) mounted on substantially rectangular support member  54  (shown in  FIG. 11 ) of standard apparatus  44 . Color changes in the total light output of the light emitting diode chips  13  are accomplished by means of programming electronics  12 , similar to that disclosed above for  FIG. 1 . Although not limited thereto, in the present disclosure it is contemplated for such programming to be accomplished through the use of momentary switch  19  that is actuated by a push button  20  or by means of electronics  12  (shown in  FIG. 10 ) that are sensitive to switch closure, radio frequency signals, signals imposed on the drive voltage, or infrared signals. The length, width, diameter, and/or height dimensions of base support  48 , substantially rectangular housing  49 , and transparent lens  57  are not critical, nor is the configuration of momentary switch  19  or push button  20 . The non-energized end of standard apparatus  44  is held in place with substantially rectangular housing  49 , and in front of reflector/refractor  50 , by means of a mechanical fastener  63  and screw  18 , although other mechanical connection means (not shown), including the use of additional screws  18 , are also contemplated for such attachment. In broken lines  FIG. 9  shows printed circuit board  16 , as well as connector and wiring harness  36  connected between printed circuit board  16  and one end of standard apparatus  44 . 
     FIG. 10  shows the standard apparatus  44  of the third preferred embodiment of the present disclosure taken along the line  45 — 45  in  FIG. 9 , and details of the electronics  12  attached to printed circuit board  16  and the substantially rectangular support member  54  upon which the light emitting diode chips  13  shown in  FIG. 11  are mounted. The rectangular configuration of support member  54  is not critical and other configurations are also considered within the scope of the present disclosure. Substantially rectangular support member  54  is preferably plastic or metal, but not limited thereto, and although not shown in  FIG. 10  or  11 , support member  54  would preferably be held in place against metallic heat sink  59  (shown in  FIG. 11 ) by means of a mechanical fastener, such as one or more screws  18 , similar to the connection shown in  FIG. 3  or  7 . As in other embodiments, metallic heat sink  59  provides heat dissipation from the light emitting diode chips  13  mounted on substantially rectangular support member  54 . Connector and wiring harness  36  provides electrical connection between the light emitting diode chips  13  mounted on substantially rectangular support member  54  and the electronics  12  mounted on a printed circuit board  16  positioned rearward from metallic heat sink  59 . Wires  8  are connected between a remote power source (not shown) and the electronics  12  mounted on a printed circuit board  16 . A refracting/reflecting lens  50  gathers the light (not shown) produced by the light emitting diode chips  13  and provides focusing as required by the application. A transparent lens  57  also seals the front opening in substantially rectangular housing  49 , to protect light emitting diode chips  13 , support member  54 , refracting/reflecting lens  50 , printed circuit board  16 , momentary switch  19 , and the electronics  12  mounted on printed circuit board  16 . The substantially rectangular housing  49  can be adjusted in vertical orientation by loosening screw  18 , moving substantially rectangular housing  49  into a desired angular position relative to base support  48 , and then re-tightening screw  18  until substantially rectangular housing  49  is fixed relative to base support  48 .  FIG. 10  also shows momentary switch  19  connected to printed circuit board  16  and push button  20  poised and ready for activation contact with momentary switch  19 . 
     FIG. 11  is an enlarged view of the circle  47  in  FIG. 9  showing in detail standard apparatus  44  positioned within substantially rectangular housing  49  and having elongated substantially rectangular support member  54  in a longitudinally extending orientation relative to substantially rectangular housing  49 , multiple light emitting diode chips  13  each mounted via whisker wires  21  to substantially rectangular support member  54 , heat sink  59  positioned rearward from substantially rectangular support member  54 , printed circuit board  16  positioned behind metallic heat sink  59 , and reflector/refractor  50  positioned between printed circuit board  16  and heat sink  59 , as well as a connector and wiring harness  36  providing the electrical connection to printed circuit board  16 . The number of light emitting diode chips  13  held in place against substantially rectangular support member  54  is not critical and the third embodiment of the present disclosure may comprise one or more light emitting diode chips  13 .  FIG. 11  further shows light emitting diode chips  13  evenly spaced apart from one another, which is not critical. 
   In an implementation, the disclosed lamp having LEDs of red, blue and green may be switched between pre-selected colors. Table I illustrates the light emitting diode colors that may be energized to achieve a radiation of one of eight colors. As an example, to achieve a lamp that illuminates with a cyan color, an equivalent number of blue and green LEDs are energized. An orange color may be achieved by energizing red LEDs and green LEDs in a number of approximately 30% or the red LEDs. White may be achieved by illuminating an equivalent number of red, blue and green LEDs. 
   
     
       
             
             
             
             
             
           
             
             
             
             
             
           
         
             
                 
               TABLE I 
             
             
                 
                 
             
             
                 
               Color 
               Red Ratio 
               Blue Ratio 
               Green Ratio 
             
             
                 
                 
             
           
           
             
                 
             
           
        
         
             
               1. 
               White 
               1 
               1 
               1 
             
             
               2. 
               Red 
               1 
               0 
               0 
             
             
               3. 
               Orange 
               1 
               0 
               0.3 
             
             
               4. 
               Yellow 
               1 
               0 
               1 
             
             
               5. 
               Green 
               0 
               0 
               1 
             
             
               6. 
               Cyan 
               0 
               1 
               1 
             
             
               7. 
               Blue 
               0 
               1 
               0 
             
             
               8. 
               Magenta 
               1 
               1 
               0 
             
             
                 
             
           
        
       
     
   
   Switching between colors is accomplished by changing the duty cycle (pulse width) of a pulse width modulator that energizes the respective colors. Binary colors (orange, yellow, cyan and magenta) are produced by setting the duty cycle of one of the primary colors (red, blue, green) colors to zero. The only time that all of the die are active is for the ternary color (white). 
   In an implementation, the switching may be between radiation of two colors. The two colors may be white and red or white and yellow, for example. The white light can be produced by a combination of energized LEDs as in Table I, above. Alternatively, a white LED can be used. The two colors may be selected for any reason. In some implementations, the white light may be used for landscape illumination some times during the year and the alternate color at other times of the year. For example, the alternative color may selected so as not to be visible to certain animal species. The alternate color may be used so as to lessen the attraction to that species. 
   The present disclosure also may be used to mitigate the variability in the peak wavelength of light radiated by an energized LED. The manufacturing process of high brightness LEDs can lead to relatively large variations in emission wavelength and power levels for devices. While it is possible to purchase LEDs with tight specifications on wavelength and power level, tight specifications lead to higher unit costs for the LEDs. When binary and ternary colors are desired, these variations can result in shifts in the perceived colors of the binary and ternary colors. This is most evident for white colors where the human eye is particularly sensitive to small changes in hue. Small differences in the emission wavelength or power levels of LEDs can make the difference between seeing light that is a pure white, pink, yellow, green, blue, purple or tinted some other color. 
   Control over the duty cycle of pulses applied to the LEDs in the present disclosure may enable the use of LEDs having wider wavelength and power specification variation than tight tolerance LEDs and still obtain a consistent white light as well as binary and ternary colors. This may be accomplished by adjusting the duty cycle for each color LED. Adjustment of the duty cycle can result in a perceived change in brightness as seen by the human eye. Thus, a change in wavelength output of an LED that results in a tinting of the white light may be overcome by adjusting the duty cycle of the energizing pulses to the LED. Once these parameters are set, binary and ternary colors can be obtained by adjusting the output according to the ratios given in Table I above. These adjustments can be made by measuring the chromaticity coordinates of the device while it is set to “white” light. If the light is in fact white, then no adjustment is necessary. If the light is reddish, then the duty cycle of the red is decreased until the light is white. If the light is bluish, then the duty cycle for the blue is decreased until the light appears white, etc. 
     FIG. 12  is a flow diagram  100  for adjusting the color of light radiated by the lamp of the present disclosure by adjusting the duty cycle of the pulses used to energize the LEDs. The lamp is energized to radiate a white light. The chromaticity of the white light is measured  102  using any standard method including a spectrograph or the human eye. If the chromaticity is found to be white, then the lamp is satisfactorily set and the method ends  130 . If the chromaticity of the white light is found to be red  106 , then the duty cycle of the pulses energizing the red LEDs is reduced  108  and the chromaticity of the white light is again measured  104 . If the chromaticity of the white light is found to be yellow (or orange)  110  then the duty cycle of the pulses energizing the red and green LEDs is reduced  112  and the chromaticity of the white light is again measured  104 . If the chromaticity of the white light is found to be green  114 , then the duty cycle of the pulses energizing the red LEDs is reduced  116  and the chromaticity of the white light is again measured  104 . If the chromaticity of the white light is found to be cyan  118 , then the duty cycle of the pulses energizing the blue and green LEDs is reduced  120  and the chromaticity of the white light is again measured  104 . If the chromaticity of the white light is found to be blue  122 , then the duty cycle of the pulses energizing the blue LEDs is reduced  124  and the chromaticity of the white light is again measured  104 . If the chromaticity of the white light is found to be purple  126 , then the duty cycle of the pulses energizing the blue and red LEDs is reduced  128  and the method is done  130 . 
   Other implementations are within the scope of the following claims.