Abstract: A gas discharge lamp ballast provides near unity power factor simultaneously with high-frequency lamp ballasting in a single switching power conversion stage resulting in efficiency improvements, reduction in size and weight and reduced component count and cost. The single conversion stage comprises a fast-recovery diode connecting in series the input inductor, energy transfer capacitor and the resonant matching network, and switching means alternately connecting the first junction between the input inductor and energy transfer capacitor, or the second junction between the matching network and the other side of said capacitor to the return current path. The switching means comprises two current bidirectional switches driven out of phase, thus producing a square-wave high frequency voltage source, which is in turn converted by the resonant matching network into a sine-wave ac current source required by the gas discharge lamp.