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The main disadvantage of single-stage electronic ballasts is the high stress that should withstand at least one of the converter switches. This drawback narrows the application range of this kind of solutions to lamps below 70 W due to the high-cost transistors needed. In the present paper, a new four-switch single-stage topology is described. This topology comes from the integration of a full-bridge resonant inverter and a double-switch buck converter. Low-cost transistors can be used for supplying lamps up to 250 W thanks to the low stress on all switches. Also, a new low-cost self-oscillating control circuit is proposed and analyzed. The basic design guidelines are also given in this paper and experimentally verified using a laboratory prototype implemented for a 125 W high-pressure-mercury lamp.