PATENT ABSTRACT
A dual LED and incandescent security lighting system uses a hybrid approach to LED illumination. It combines an ambient LED illuminator with a standard incandescent lamp on a motion control sensor. The LED illuminator will activate with the onset of darkness (daylight control) and typically remain on during the course of the night (“always on”). The LED illumination, typically amber, is sufficient to provide low to moderate level lighting coverage to the wall and ground area adjacent to and under the fixture. The incandescent lamp is integrated with a motion control circuit and sensor. When movement in the field of view is detected (after darkness), the incandescent lamp is switched on, providing an increased level of illumination to the area. Instead of an “always on” LED illuminator, the LEDs may also be switched off when the incandescent lamp is switched on.

PATENT DESCRIPTION
GOVERNMENT RIGHTS 
   The United States Government has the rights in this invention pursuant to Contract No. DE-AC03-76SF00098 between the United States Department of Energy and the University of California. 

   BACKGROUND OF THE INVENTION 
   The invention relates generally to LED lighting systems and more particularly to security lighting systems with LEDs. 
   As LED technology progresses, LEDs will be used for many lighting applications. White light LEDs are still in their infancy and questions regarding their color rendering and lifetime need to be resolved before wide scale commercial adoption. Colored LEDs, however, are a proven technology, and as outputs continue to increase, colored lighting opportunities will be further enabled. Exit signs and traffic signals are examples of colored lighting markets that have seen widespread commercial success by LEDs and soon may be dominated if not monopolized by LEDs. 
   Security lighting, particularly in outdoor environments, is a lighting application of great interest. LEDs are not the ideal choice because white light is generally needed and only colored LEDs are generally available. Incandescent lights can be used but consume much more energy. Thus a security lighting system with the advantageous features of both LEDs and incandescent lamps without their limitations is highly desired. 
   SUMMARY OF THE INVENTION 
   The invention is a dual Led and incandescent security lighting system that uses a hybrid approach to LED illumination. It combines an ambient LED illuminator with a standard incandescent lamp on a motion control sensor. The LED portion will activate with the onset of darkness (daylight control) and typically remain on during the course of the night (“always on”). The LED illumination, typically amber, is sufficient to provide low to moderate level lighting coverage to the wall and ground area adjacent to and under the fixture. The incandescent lamp is integrated with a motion control circuit and sensor. When movement in the field of view is detected (after darkness), the incandescent lamp is switched-on, providing an increased level of illumination to the area. Instead of an “always on” LED illuminator, the LEDs may also be switched off when the incandescent lamp is switched on. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a dual LED/incandescent security lighting system of the invention. 
       FIG. 2  shows a variation of the dual LED/incandescent security lighting system of FIG.  1 . 
       FIGS. 3-5  show other embodiments of the dual LED/incandescent security lighting system of the invention. 
       FIG. 6  shows another embodiment of the dual LED/incandescent security lighting system of the invention with a separate LED drop unit. 
       FIG. 7  is a block diagram of a control system for the dual LED/incandescent lighting system of the invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The invention may be Implemented in a number of different embodiments. The following are illustrative but not limiting. 
   As shown in  FIG. 1 , hybrid LED/incandescent light fixture  10  combines an LED array  12  and an incandescent lamp (A-lamp)  14  in a single housing  16 . The incandescent source or lamp  14  screws into a standard socket  15  and is held in a horizontal position. The LED array  12  is placed facing down from the top  22  of the housing  16 , near the front edge, and extending forward substantially beyond A-lamp  14 . The top  22  of housing  16  not only supports the LED array  12  but also provides a heatsink for the LED array  12  and provides a physical shield to prevent light from either the LED array  12  or A-lamp  14  from traveling upwards into the night sky. Housing  16  is attached to a wall mount/power supply unit  17 , which is attached to wall  20  and electrically connected to a power source, typically standard electrical wiring from a power line. Socket  15  and LED array  12  are electrically connected to unit  17  for power. A motion detector  18  is mounted below housing  16  (or elsewhere) and is also electrically connected to unit  17  for power. The control system for fixture  10  is contained in unit  17 . 
   Also forming a part of housing  16 , extending down from top  22  and surrounding or enclosing LED array  12  and A-lamp  14 , is a diffuser or lens  19 , which typically is a diffuser but also may be a clear lens. The front part  23  of diffuser/lens  19  is typically tapered inwardly from top to bottom. LED array  12  includes a plurality of LEDs  21 . The LEDs are typically amber or yellow in color, but may be other colors or even white. A-lamp  14  may be replaced by a halogen lamp, or compact fluorescent lamp, or other lamp. Diffuser/lens  19  allows the light from LED array  12  and from A-lamp  14  to pass to the local environment, generally illuminating the area around fixture  10 . Diffuser/lens  19  is typically formed of flat or roughened panes of clear or translucent glass or plastic. 
   In operation, a sensor detects the occurrence of darkness and turns on the LED array  12 . After that, whenever motion sensor  18  detects motion in the vicinity of fixture  10 , the A-lamp  14  is switched on, and remains on for a preset time. LED array  12  may remain on when A-lamp  14  is on, or it may shut off to conserve energy and to prevent color shadows. 
   The construction of the fixture  10  is such that the light output is directed down, mitigating light pollution issues. This fixture is intended as a replacement fixture: it either replaces a porch light in a retrofit application, or is used in new construction as an alternative to another porch light. 
     FIG. 2  shows a dual LED/incandescent fixture which is very similar to fixture  10  of  FIG. 1  except for the position of LED array  12  relative to A-lamp  14 . In fixture  11 , LED array  12  is recessed into housing  16  so that it is over A-lamp  14 . Most of the light from LED array  12 , then passes through A-lamp  14 , which acts as a diffuser, so lens  19  is then typically clear. The remaining components are the same as in FIG.  1 . 
     FIG. 3  shows an alternate embodiment of the invention with the incandescent lamp  14  in a lamp down orientation. The LEDs  21  are mounted in a ring around the base of the A-lamp  14 . Dual LED/incandescent fixture  25  incorporates many of the same components as fixtures  10 ,  11  but in a different arrangement. Fixture  25  hangs down from a wall or overhang  20 . Power supply/wall mount unit  17  is attached under wall  20  and contains the electrical connections to the power source and the control system. Socket  15 , into which A-lamp  14  screws, is mounted under and electrically connected to unit  17 . LEDs  21  are mounted on and electrically connected to unit  17 , forming an array  12 . Motion sensor  18  is integrated into unit  17 . Diffuser/lens  19  extends down from unit  17  and encloses and surrounds LEDs  21  and A-lamp  14 . 
     FIG. 4  shows another embodiment of the invention that is intended as a screw-in retrofit. In the dual fixture  30 , the LEDs  21  and associated electronics are integrated into a screw-in A-lamp type base  32 . This base  32  then receives a standard A-lamp,  14  in A-lamp socket  33 . Base  32  screws into a standard socket in a wall which is connected to electrical power, e.g. in a standard porch light fixture. A-lamp  14  and LEDs  21  are thereby electrically connected to a power source. A light guide or cover lens  34  that attaches to the base  32  may be necessary to control the light distribution, as well as mitigate direct glare from the LEDs  21 . LEDs  21  are arranged in an array  12  around the edge of base  32  and are aligned with an input section  35  of light guide/lens  34 . 
   In an alternate embodiment shown in  FIG. 5 , dual LED/incandescent system  40  separates the LED lighting component from the incandescent lighting fixture. There are separate side-by-side fixtures, LED fixture  42  and A-lamp fixture  44 . A-lamp fixture  44  is essentially a standard porch light fixture. LED fixture  42  attaches to wall  20 , e.g. at an outdoor junction box. An array  12  of LEDs  21  is mounted in LED fixture  42 , facing downward, and enclosed or surrounded by a diffuser/lens  43 . LED fixture  42  is built to receive an A-lamp fixture  44  on its front surface, as shown by arrows  45 . A-lamp fixture  44  includes a downward facing incandescent lamp  14 , which screws into electrical socket  15 . A diffuser/lens  46  encloses and surrounds A-lamp  14 . The electronics, including the motion sensor, are typically mounted in LED fixture  42 . 
   Another embodiment of the invention, shown in  FIG. 6 , also separates the LED light component from the incandescent fixture. But instead of having the LED, motion sensor, and control electronics in the same box, dual LED/incandescent system  50  has an LED “drop”unit  52  under the main incandescent unit control box  54 . Control box  54  is configured to mount onto a wall. The front surface is configured to receive a standard “porch light” type fixture  55  (similar to fixture  44  in FIG.  5 ). Control box  54  typically contains the LED driver circuit, the motion control circuit, and the daylight sensing circuit. Drop unit  52  contains the LEDs and the motion-sensor, which operates through motion sensor window  53 . Drop unit  52  is connected to main unit  54  by drop arm  56 . The drop arm could have an adjustable length, and could be set by the end user according to the particular installation environment. This “drop” feature accomplishes several things. It lowers the LED emitters, reducing the problem of direct glare from the LEDs and increasing the illuminance on the ground below the fixture. It allows the motion sensor unit, also incorporated into the drop unit, to clear the porch light fixture and see the appropriate field of view for proper motion sensing operation. It also separates the heat generating LEDs from the rest of the unit, keeping this heat away from the control electronics. 
     FIG. 7  illustrates a control system  60  for the dual LED/incandescent lighting system of the invention. A detector  61  detects the onset of darkness and actuates a switch  62  which turns on LED array  63 . During darkness, when motion sensor  64  detects motion, its output signal is combined with the output signal from detector  61 , e.g. in AND gate  65 , to actuate a second switch  66  to turn on A-lamp  67 . Once A-lamp  67  is turned on, a timer  68  which is also actuated by switch  66  may be used to turn off A-lamp  67  after a preset and selectable period of time. Switch  66 , when turned on, may also turn off switch  62  to shut off the LED array  63  when A-lamp  67  is on. 
   This type of hybrid approach to LED illumination has the following advantages and benefits.
     1) The LED source (one or more LEDs in an array) consumes a relatively small amount of power compared to the incandescent source, yielding substantial energy savings without a loss in functionality.   2) The LED source provides ambient illumination to the area, eliminating the “all-or-nothing” effect of traditional motion sensor fixtures.   3) The LED source will have a very long lifetime, ensuring at least some illumination to the control area when the incandescent lamp fails.   4) With colored LED sources, the motion activated incandescent lamp will provide a color change when triggered, increasing the conspicuousness of the motion activation and increasing the security benefit of the trigger.   5) With colored LED sources, different nighttime aesthetics can be achieved.   6) The combination of the LED source(s) and the incandescent source yields the best dollars per lumen ratio for the target applications. The number of (expensive) LEDs is kept to a minimum while, at the same time, the incandescent lamp provides a high lumen output for good visibility when the application area is occupied.   

   Changes and modifications in the specifically described embodiments can be carried out without departing from the scope of the invention which is intended to be limited only by the scope of the appended claims.