Direct current ballasting and starting circuitry for gaseous discharge

Abstract

Direct current ballasting and starting circuitry for efficiently operating a gaseous discharge lamp on direct current. Series-pass switching means in one of a pair of input lines alternatively switches between on and off states to periodically supply pulses of energy from a source of direct current voltage. During steady-state operation, current sensing means limits the maximum current conductable by said switching means such that the output of the circuitry is current regulated. Starting means, in series connection between the filter means and an output terminal, senses the nonionized state of the lamp and provides a voltage pulse of sufficient magnitude and duration to initiate ionization in the lamp. Various forms of control means or drive means for controlling the conductive state of the switching means are disclosed. An A.C. to D.C. power conversion circuit, for operating a plurality of ballasting and starting circuits therefrom, utilizes a portion of a primary winding of a transformer for connection to the A.C. voltage source. A stepped up A.C. voltage across the entire primary winding is applied to a rectification means, which rectifies the A.C. voltage and supplies the same to a filter means. The filter means provides a D.C. voltage for input to the ballasting and starting circuits. A center-tap on a secondary winding of the transformer is referenced to the second of a pair of input lines of the ballasting and starting circuit, and the ends of the secondary winding provide a small A.C. voltage to the cathodic heater element of the lamp.