THERMAL PROTECTION CIRCUIT FOR AN LED BULB

摘要

A light-emitting diode (LED) bulb has an LED within a shell. The LED bulb also includes a driver circuit for providing current to the LED. The drive circuit has a thermal protection circuit, which includes a thermistor having a positive thermal coefficient and a switching temperature. The driver circuit also includes a switch-mode power supply (SMPS) controller with an input pin and an output pin. The thermistor is connected to the input pin. When the thermistor temperature is above the switching temperature, the thermal protection circuit causes the SMPS controller to produce a signal with a second duty cycle on the output pin. When the thermistor temperature is below the switching temperature, the thermal protection circuit causes the SMPS controller to produce a signal with a first duty cycle on the output pin. The second duty cycle is higher than the first duty cycle.