ELECTRICAL AND LIGHT CHARACTERISTICS OF RF-INDUCTIVE FLUORESCENT LAMPS

The authors have measured the external electrical characteristics (RF voltage, current, and phase angle) and the relative light output of inductively coupled fluorescent lamps driven at 13.56 MHz in a range of RF power levels between 9 and 37 W. The experiments have been carried out using glass envelopes having a spherical external shape with a re-entrant cylindrical cavity in the center. Measurements were taken of reentrant cavities of different diameters and of exciter coils having a different number of turns. RF-lamp power, power transfer efficiency, relative LPW, and effective RF field in the plasma have been inferred from measured electrical and light output characteristics. The condition of maximum RF power transfer efficiency to the plasma and the condition for maximum RF-lamp LPW were found for different lamps. The results of these measurements can be used in optimizing RF-driven inductively coupled fluorescent lamps and RF power converters needed to drive these lamps.