Patent ID: 8076868

Claim:
A power control circuit, adapted for controlling a power converter to drive a light emitting diode series, wherein the power converter receives a driving pulse outputted from the power control circuit to generate a driving voltage to a first terminal of the light emitting diode series, the power control circuit comprising: a constant current control circuit, coupled to a second terminal of the light emitting diode series to control the current flowing through the light emitting diode series; a feedback circuit, coupled to the second terminal of the light emitting diode series to generate a feedback voltage; an error amplifier circuit, for receiving a first reference voltage and the feedback voltage to generate an error voltage; a saw-tooth generator, comprising: a variable current source, for generating a time variant current according to a time variant function; and a peak detector, for generating a time variant saw-tooth voltage corresponding to the value of the time variant current, wherein the time variant saw-tooth voltage is reset when the time variant saw-tooth voltage is larger than a second reference voltage; and a power converter driving circuit, for receiving the time variant saw-tooth voltage and the error voltage to generate the driving pulse.