21-09-2008, 10:30 AM
Definition
RF light sources follow the same principles of converting electrical power into visible radiation as conventional gas discharge lamps. The fundamental difference between RF lamps and conventional lamps is that RF lamps operate without electrodes .the presence of electrodes in conventional florescent and High Intensity Discharge lamps has put many restrictions on lamp design and performance and is a major factor limiting lamp life.
Recent progress in semiconductor power switching electronics, which is revolutionizing many factors of the electrical industry, and a better understanding of RF plasma characteristics, making it possible to drive lamps at high frequencies.The very first proposal for RF lighting, as well as the first patent on RF lamps, appeared about 100years ago, a half century before the basic principles lighting technology based on gas discharge had been developed.
Discharge tubes
Discharge Tube is the device in which a gas conducting an electric current emits visible light. It is usually a glass tube from which virtually all the air has been removed (producing a near vacuum), with electrodes at each end. When a high-voltage current is passed between the electrodes, the few remaining gas atoms (or some deliberately introduced ones) ionize and emit coloured light as they conduct the current along the tube. T
he light originates as electrons change energy levels in the ionized atoms. By coating the inside of the tube with a phosphor, invisible emitted radiation (such as ultraviolet light) can produce visible light; this is the principle of the fluorescent lamp. We will consider different kinds of RF discharges and their advantages and restrictions for lighting applications.
