A driver for providing variable power to a LED array, which can be coupled through a dimmer to an AC power supply, comprises a filtering and rectifying unit, a switching power unit, and a control unit. The filtering and rectifying unit is adapted to attenuate EMI and convert an AC power from the AC power supply into a DC power output. The switching power unit is adapted to receive the DC power output and provide an output current to the LED array. The control unit is adapted to determine the output current in response to a comparison between a dim reference signal representing phase-modulating information of the AC power and a feedback signal representing an average value of the output current. The LED array can thus be controlled by a dimmer at the primary side so as to adjust its light output, and can further be utilized in currently existing lighting infrastructures.