US Patent 8698419 Circuits and methods for driving light sources

A circuit for driving a light-emitting diode (LED) light source includes a converter, a saw-tooth signal generator, and a controller. The converter includes a switch which is controlled by a driving signal. The converter provides a sense signal indicating the current through said LED light source. The saw-tooth signal generator generates a saw-tooth signal based on the driving signal. The controller generates the driving signal based on signals including the saw-tooth signal and the first sense signal to adjust the current through the LED light source to a target level and to correct a power factor of the driving circuit by controlling an average current of the input current to be substantially in phase with said input voltage.