Single-stage high power factor electronic ballast for fluorescent lamps with constant power operation

A single-stage high power factor electronic ballast is designed to operate fluorescent lamps at a constant power over a very wide input voltage range. The electronic ballast performs the constant power operation by adjusting the duty-ratio of the embedded power regulation circuit. With duty-ratio control, a preheating period for the cathode filaments can be provided before igniting the lamp. The operation of the electronic ballast is discussed by an illustrative example with experimental results.