US Patent 7812544 Fluorescent light control

Circuitry, which is compatible with incandescent light dimmers, is disposed within the screwbase of a compact fluorescent light, and sets driving frequencies for a mercury plasma, based, at least in part, on sensing the duty cycle of the incoming AC supply waveform. In this way, existing lighting infrastructure, including phase-cut dimmer circuits for incandescent light bulbs, may be preserved, and incandescent bulbs can be replaced with compact fluorescent lights equipped with circuitry in accordance with the present invention. In a further aspect, the circuitry synchronizes the bulb drive signals with the AC power line frequency.