Electrical control for an LED light source, including dimming control

#1. Field of the Invention

#The present invention is directed to an electrical control for light emitting diode (LED) light sources, and particularly to an electrical control that can provide a dimming control of the LED light source to simulate a dimming operation in a conventional incandescent light source.

#2. Background of the Invention

#FIG. 1 shows the dimming property of a conventional incandescent light source.

#FIG. 2 shows a comparison of the relative brightness of an LED light source versus input power in comparison with the non-linear brightness control of an incandescent light source shown in FIG. 1.

#FIG. 3 is block diagram of a background power source system used to provide power to LEDs from a given power source.

#The applicant of the present invention has recognized that one potential problem with replacing conventional incandescent light sources with LED light sources is that an LED light source differs in its dimming operation from that in an incandescent light source. This is a particular problem when LED light sources are used to replace incandescent light sources as the incandescent light sources bum out, which results in both LED light sources and incandescent light sources operating in the same system. As one concrete example, runway lights, taxiway lights, etc. at airports conventionally utilize incandescent light sources. If an airport operator wishes to switch to LED light sources, the airport operator would like to do so over time as the conventional incandescent light sources burn out, for the obvious economic reason to avoid having to replace every incandescent lamp with an LED light source at the same time, and to get the maximum usage out of the existing incandescent light sources. In such a situation both LED light sources and incandescent light sources will be part of the lighting system at the same time.

#The applicant of the present invention has recognized that an LED light source and an incandescent light source have different dimming properties. In this instance dimming is defined as reducing the output brightness of a light source by varying the input power. The different dimming properties make it difficult to replace the incandescent light sources with the LED light source.

#FIG. 1 shows the dimming property of a conventional incandescent light source, in this case an incandescent light L861T manufactured by Dialight Corporation. As shown in FIG. 1, the brightness of the noted incandescent light source relative to input power has an exponential function of ex, which is typical for all incandescent light sources. In contrast to such a brightness control, i.e. dimming property, of an incandescent lamp, a brightness control of an LED light source is substantially linear.