Evaluation of a high efficiency boost stage to supply a permanent LED emergency lighting system

The first LED diode was made around 1962 (red LED by Holonyank & Bevacqua). These initial LEDs and posterior developments are widely used in very-low lighting level applications. Ternary and quaternary alloys are the bases of the present high-brightness LED's. Currently power LEDs are used in low-medium lighting applications: for instance, permanent emergency lighting systems (PELS), traffic lights, emergency exit indications, lighting in critical or strategic points, i.e. the limited lamp life in classical lamps 10.000-20.000 hours for fluorescent lamps implies short lamp-replacement times and, therefore, high maintenance costs. To overcome this situation a boost converter to supply a PELS system based in LED was developed. The topology and proposed control assure a constant current through LEDs for all the battery conditions. The long operation life (above 100.000 hours) of high efficiency LED's and a very simple electronics circuitry implies an interesting solution for this type of applications. Finally, a 30 lumens and 1 hour PELS has been built and tested.