Hf Operation Of Fluorescent Tubes

36 EE June 1988 HF OPERATION OF FLUORESCENT TUBES A circuit is described that enables HF control of fluorescent tubes. This not only increases the already high luminous efficacy of these lamps, but also enables them to be dimmed gradually. Although fluorescent tubes have a much higher luminous efficacy* (80-90 Im/W) than ordinary, vacuum light bulbs (about 15 1m/W), and have a much longer life expectancy, they are nowhere near as popular for use in the home. This unpopularity is caused by the "cold" character of the light, the difficulty of controlling (dimming) the light, and the objectionable behaviour (flickering) im- mediately after switch-on. Although the present circuit cannot alter the character of the light (manufacturers are already producing much "warmer" fluorescent tubes), it does obviate the other two undesirable aspects. Economy of HF control High-frequency control units for fluorescent lamps have been available for some time, but so far these are mainly used in fact...