Abstract: Fluorescent lamp ballasts and methods are disclosed in which a resonant impedance of a self-oscillating inverter is modified to control the inverter frequency to selectively preheat lamp cathodes using power from the inverter output during a preheating period after power is applied and to change the inverter frequency to a different range following ignition of the lamp.

Abstract: Fluorescent lamp ballasts and methods are disclosed in which a resonant impedance of a self-oscillating inverter is modified to control the inverter frequency to selectively preheat lamp cathodes using power from the inverter output during a preheating period after power is applied and to change the inverter frequency to a different range following ignition of the lamp.

Abstract: A transformer bobbin has a body with first and second ends spaced along a longitudinal axis. Conductive pins are mounted in the ends and dimensioned for electrical and mechanical connection with first and second wire windings received in the body. An opening in the body is dimensioned to receive a ferrous core, and an external winding surface on the body extends between the first and second ends. First and second margin barriers are provided inwardly of the first and second ends of the winding surface. The margin barriers have a height that extends a predetermined dimension that closely approximates the height of the first winding. The margin barriers electrically isolate the first winding from the second winding that is thereafter received over the body. Preferably, at least one of the first and second margin barriers includes channels therethrough dimensioned to receive the first winding wire for connection with the pins.