Abstract: A constant light output ballast circuit capable of regulating lamp current to a substantially constant level independent of the number of fluorescent lamps on load. The circuit incorporates a power factor control circuit and an electronic ballast circuit having a secondary winding on its output transformer. The voltage on the secondary winding, which is proportional to the ballast circuit's output voltage, is fed back to the power factor control circuit to regulate the DC output voltage supplied to the electronic ballast circuit and thereby maintain a constant lamp current.

Abstract: A low in-rush current power factor control circuit that provides near unity power factor, is capable of controlling and limiting the in-rush current that occurs when the circuit is initially supplied with an AC mains input voltage and is further capable of controlling the DC output voltage of the circuit from a level above to below the peak AC mains input voltage.