Abstract: A d.c.-a.c. inverter circuit allows a standard type fluorescent lamp to be operated from a low-voltage source of d.c. power with a high degree of efficiency attributable in part to use of lamp current as base drive current for a power transistor controlling the energization of a transformer primary winding having two mutually connected secondary windings which apply voltages across the lamp through the power transistor. Additional efficiency is achieved by use of a second transistor under time delay control for supplying preheat current to the lamp and turn-on current to the power transistor only during the starting phase of lamp operation.