a dimming method for led driving circuit is proposed . by temporary switching a pin that is originally used for the input / output of other electric signals to a high impedance node , the dimming control signal may be inputted to dim leds . the dimming method comprises the steps of : floating the pin every a period of time to pull the pin &# 39 ; s voltage being equal to the dimming control signal ; detecting the pin &# 39 ; s voltage ; and retrieving the dimming control signal in accordance with the detected pin &# 39 ; s voltage and thereafter dimming the leds .