| 摘要 |
Direct current ballasting and starting circuitry for efficiently operating a gaseous discharge lamp on direct current. A series-pass switching transistor in one of a pair of input lines alternately 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 circuitry limits the maximum current conductable by the transistor such that the output of the circuitry is current regulated. A filter, in series with the transistor, smoothes the pulses of energy delivered by the transistor into direct current with a comparatively small alternating current component. Starting circuitry in series connection between the filter 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, but permits uninterfered passage of current through the filter to the output. Various forms of control or drive circuitry for controlling the conductive state of the transistor are disclosed, including a phase-corrected oscillator which is momentarily excited by a starting pulse delivered at the output terminal and oscillation is thereafter sustained by interaction with the transistor a resonant transformer capacitor circuit with a secondary winding of the transformer controlling the transistor; and a pulse-width modulation drive. Various starting circuits are disclosed, including a single starting circuit for sensing the nonionized state of any of a plurality of lamps.
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