This paper presents a high power factor electronic ballast used in fluorescent lamps with a single power stage and a single-switch. This topology has been obtained by combining the boost topologies and a new inverter topology with coupled inductors. The use of a single active switch allows a reduction in the number of components used in the control and power circuits. The equations used in the proposed reactor design and also in the choice of the semiconductor devices have been presented. A prototype with switching frequency equal to 50 kHz has been built to startup 40 W fluorescent lamps.