20090200960 | Methods and Apparatus for Self-Starting Dimmable Ballasts With A High Power Factor - Methods and apparatus for self-starting dimmable ballast circuits are disclosed. In the described examples, a dimmable ballast circuit includes a rectifier, an energy storage device, a driver circuit, and a resonant circuit that are configured to actuate the light source such as a fluorescent lamp. The power source is coupled to the light source via a single resonant circuit that includes power factor correction therein. Further, the resonant circuit is selectively configured to start the light source without requiring a separate starter circuit. Further, energy storage device is a capacitor that stores high frequency energy and continually recycles energy in the circuit, resulting in a circuit with a large power factor. Because the current flowing in the circuit is substantially sinusoidal, the described examples generally have an ideal power factor. | 08-13-2009 |