Patent ID: 7750616

Claim:
A buck converter LED driver circuit, comprising: a buck power stage comprising an LED and providing a first signal directly proportional to the current through the LED; a rectified AC voltage source coupled to the buck power stage for driving the buck power stage; a voltage waveform sampler coupled to the rectified AC voltage source for providing a second signal directly proportional to the voltage provided by the rectified AC voltage source; an SR flip-flop with an output end coupled to the buck power stage for turning on and turning off the buck power stage; a clock generator coupled to the SR flip-flop for providing a clock signal to a setting end of the SR flip-flip; and a comparator with a positive end coupled to the buck power stage for receiving the first signal, a negative end coupled to the voltage waveform sampler for receiving the second signal, and an output end coupled to a resetting end of the SR flip-flop.