Patent ID: 8283877

Claim:
A light-emitting diode (LED) bulb comprising: a shell; an LED contained within the shell; a heat sink for dissipating heat generated by the LED; a driver circuit for providing current to the LED, the driver circuit having a thermal protection circuit that comprises: a first thermistor having a positive thermal coefficient and a first switching temperature; a switch-mode power supply (SMPS) controller having an input pin and an output pin, wherein the first thermistor is connected to the input pin; a MOS transistor having a gate terminal connected to the first thermistor and a drain or a source terminal connected to the input pin, wherein, when the first thermistor is at a temperature above the first switching temperature, the first thermistor is configured to cause the input pin of the SMPS controller to be at or below a first voltage, wherein, when the first thermistor is at a temperature below the first switching temperature, the first thermistor is configured to cause the input pin of the SMPS controller to be at or above a second voltage, wherein the second voltage is higher than the first voltage, wherein, when the input pin is at or below the first voltage, the SMPS controller is configured to supply a first signal with a first duty cycle on the output pin, and wherein when the input pin is at or above the second voltage, the SMPS controller is configured to supply a second signal with a second duty cycle on the output pin, and wherein the second duty cycle is higher than the first duty cycle; and a base attached to the shell for connecting the LED bulb to an electrical socket.