Light control for electronic ballast powered by a DC power supply

This work presents the development of an electronic ballast based on the Class E resonant inverter, which controls directly the radiated light intensity, instead of the lamp current. The control proposed in this paper improves the settling time of the output light and compensates the wearing out of the electrodes of fluorescent lamps, since, even if the luminous efficacy of the lamps decays as they age, a higher power will be applied to maintain the desirable light intensity. As the system is powered by a DC voltage, the light control compensates the input voltage variations and executes the preheating and ignition stages varying the switching frequency.