CIRCUIT FOR PROTECTING LED FROM SURGE

摘要

A circuit for protecting a Light-Emitting Diode (LED) from surge, including a discharging capacitor and LED load, is characterized in that the circuit further including a field-effect tube, a first resistor, a second resistor, a first transistor, a third resistor and a fourth resistor, wherein the resistance of the second resistor is bigger than or equal to the ratio between the threshold voltage of the first transistor and the maximum breakdown current of the LED load; the drain of the field-effect tube is connected to the negative electrode of the output power source of a LED driver; the source of the field-effect tube is connected to the negative electrode of the direct current power source of the LED driver via the second resistor and also connected to the base of the first transistor via the fourth resistor, and the emitter of the first transistor is connected to the negative electrode of the output power source of the LED driver; the grid of the field-effect tube is connected to the collector of the first transistor via the first resistor and also connected to the direct current voltage via the third resistor. A low voltage field-effect tube is used for limiting current in the present invention, so that the entire circuit has fast response speed with low circuit power consumption; and the surge current from the power source of the LED driver to the backward stage LED load is restrained effectively so as to extend the working life of the LED load.