SEPIC converter to perform power factor correction in a ballast for fluorescent lamps

Due to their inherent advantages, electronic ballasts for gas discharge lamps have found widespread application in recent years. But, up to now, each ballast had to be tailored to fit a given lamp, resulting in a multitude of ballasts, that differ only by their operating parameters. One important requirement in order to operate different lamps with the same ballast was the availability of cost-effective microcontrollers which allow a great amount of flexibility. The second barrier to overcome was the restriction of a fixed bulk voltage given by a standard boost converter. This paper will point out how a SEPIC converter used as a power factor correction circuit will introduce a new degree of freedom to the ballast, resulting in multi-lamp ability. An introduction to the operating principles of the SEPIC will be given and the extra features, which are inherent to the SEPIC, will be discussed.