Abstract: A dimming system provides power from a switch-controlled power source in series with a leakage auto-transformer to a compact fluorescent lamp. The system incorporates a high-frequency resonant converter that provides high voltages to strike and maintain an electric discharge in the lamp. The converter is loaded in parallel by the lamp, whose impedance damps the converter to stabilize lamp operation. An inductor, connected between the leakage auto-transformer and the resonant converter, isolates the switch-controlled power source from the high-frequency voltage. The system can be used with a variety of standard leakage reactance auto-transformers to provide full-range dimming of compact fluorescent lamps from 5 to 100 percent light output with minimal flicker.

Abstract: A dimming system, which provides a time-varying current from a power source between the electrodes of a gas discharge lamp, simultaneously provides high-frequency, low-level current between the electrodes to sustain an electric discharge in the lamp when the time varying current alone is insufficient. The system provides reduced starting stress in the lamp and, therefore, longer lamp life by delaying the formation of an arc discharge, during start-up, until the electrodes have been heated. The system can be used with standard magnetic ballasts to provide full-range dimming of gas discharge lamps from 3 to 100 percent light output with minimal striations, lamp drop out, and flicker.

Abstract: A dimming circuit provides power from an ac source to a compact fluorescent lamp. The circuit generally includes a resonant circuit driven by a high-frequency switching inverter and a current feedback control system. The circuit is essentially an ac current source of unusually high impedance and provides substantially symmetrical high-frequency current to the lamp. This allows flicker-free dimming of compact fluorescent lamps over a wide range with good light output stability. A small amount of dc or low-frequency ac current may be simultaneously provided to the lamp. The resulting composite current waveform flowing through the lamp substantially eliminates visible striations over a dimming range from about 100% to 1% of full light output.