Thermal protection circuit for an LED bulb

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.