Patent ID: 8754594

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 configured to have a first switching temperature; a second thermistor configured to have a second switching temperature, wherein the second thermistor is connected in series with the first thermistor; a first resistor; a switch-mode power supply (SMPS) controller having an input pin and an output gate pin, wherein the first thermistor is connected to the input pin and the first resistor is connected to the output gate pin, wherein, when the first thermistor is at a first operating 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 second thermistor is at a second operating temperature above the second switching temperature, the second thermistor is configured to cause the input pin of the SMPS controller to be at or below the first voltage, wherein, when the first thermistor is at a third operating temperature below the first switching temperature and the second thermistor is at a fourth operating temperature below the second switching temperature, the first thermistor and the second thermistor are 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 gate 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 gate 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.