The present invention provides a LED driver for controlling the brightness of the LED. An inductor and a switch are connected in series with the LED for controlling the current of the LED. A diode is coupled in parallel to the inductor for freewheeling the energy of the inductor through the LED. A control circuit is developed to generate a control signal for switching the switch in response a reflected signal of inductor and the LED current. The LED current is further adjusted in response to the reflected signal. The value of the reflected signal is correlated to the LED temperature. Therefore the LED current can be programmed in accordance with the LED temperature.