Abstract: The LED driver includes a rectifier, a switching circuit and a feedback circuit. The rectifier connects an AC power source and outputting DC power. The switching circuit connects the DC power of the rectifier to switch the DC power with pulse width modulation (PWM) and has an output end for connecting a load and a feedback control end. The feedback circuit is connected between the output end and the feedback control end of the switching circuit for controlling a duty cycle of the switching circuit depending on an output current of the output end to keep the output current constant.