A new control method for electronic ballasts based on magnetic regulators

In this paper a new control method for electronic ballasts based on using magnetic regulators is presented. The main goal is to perform the complete control of the electronic ballast maintaining constant switching frequency and without using other parameters of the transistor bridge, as the input voltage or the duty cycle. The magnetic regulator is controlled by means of a dc current, which allows performing both lamp soft starting and dimming. Apart from the important advantage of keeping constant frequency during full electronic ballast operation, the proposed method presents additional benefits when compared with other control methods, as inherent isolated control, more linear control characteristics and higher efficiency. Experimental results from a 36 W linear fluorescent lamp prototype are presented.