Electroluminescence (EL) is a form of light generation that relies on an electronic phenomenon known as radiative recombination which causes excited or activated electrons to release energy in the form of photons or visible light. In this electronic reaction, phosphorescent materials react to the introduction of small electrical charges by emitting a soft, cool, glare-free glow. EL materials are typically presented in a powder or film form, draw very little power, and can be formulated to produce a fairly wide range of different colors. EL is widely used in applications such as night lights, information displays, and automobile instrument panels.
The most common presentation of these phosphorescent materials is the thin film format. These materials are produced by spreading a thin film of phosphorous on a transparent film which is then covered with a conductive material. The power for the light source is introduced through aluminum or copper foil strips imbedded in the phosphorous layer. Power is then supplied to the EL lamp using an electroluminescent inverter.
These devices require relatively high alternating current (AC) operating voltages of between 60 and 600 volts with very little current drain. In battery operated applications, this voltage is converted from direct current (DC) to the required AC voltage by an internal electroluminescence inverter. In applications where an AC mains supply is used, the device may draw power directly from that supply. In either case, these electroluminescent lamps draw very little current, 0.08W at 230V for a 2.3 inch (60 mm) diameter night light for example, which makes them very cost effective light sources.
One common use of EL is in animated or flashing displays. In these applications a running light or flasher driver is used to control the flash or animation characteristics of the display. This driver is little more than an inverter which drives an integrated circuit (IC) chip connected to several different EL tapes or strips. This IC set-up illuminates the different EL strips in a controllable sequence which produces the animation or flashing.
The soft, glare-free nature of electroluminescence is ideally suited for children’s night lights and automobile instrument panels. EL materials can be manufactured to produce a fairly wide range of colors with the green range producing the greatest apparent light intensity for the least power consumption. Recent developments in EL technology have produced red, green, and blue electroluminescence sources which, when combined, are capable of producing full color, long life displays. These characteristics all make EL lighting one of the most versatile low voltage lighting sources available.