Patent ID: 8461767

Claim:
A light-emitting diode (LED) bulb comprising: a shell; an LED contained within the shell; a driver circuit for providing current to the LED, the driver circuit having a power factor control circuit that comprises: a tracking circuit connected to a supply line to the LED, wherein the tracking circuit is configured to produce a tracking signal indicative of the voltage of the supply line; a switch-mode power supply (SMPS) controller having an input pin and an output pin, wherein the tracking circuit supplies the tracking signal to the input pin, wherein, in response to the tracking signal being below a threshold voltage, the SMPS controller is configured to change a duty cycle of an output signal on the output pin based on the tracking signal, and wherein, in response to the tracking signal being above a threshold voltage, the SMPS controller is configured to provide the output signal on the output pin independent of the tracking signal; and a base attached to the bulb for connecting the LED bulb to an electrical socket.