Circuit for dimming compact fluorescent lamps

Abstract

A dimming control circuit provides power from an ac source to a compact fluorescent lamp. The circuit generally includes a resonant half-bridge inverter driven by a pulse-duration-modulated voltage, for providing a high-frequency ac voltage between the lamp electrodes. A combination inductive and capacitive snubber circuit reduces switching losses in the inverter and increases the efficiency of the dimming circuit. A low-voltage transformer connected across the resonant portion of the inverter provides voltage to heat the lamp filaments. The filament voltage is substantially constant over a range of pulse-durations providing a dimming range from about 100% to 1% of full light output. A power supply circuit having a power factor of about 0.95 provides both high-voltage and low-voltage dc power to the dimming circuit with minimal losses. A shutdown circuit is provided to shut off power to the lamp if the dimming circuit is miswired or a ground fault occurs.

Dependencies are inferred from the claim text.