a filter tuner connected to a manual switch and an external AC power, wherein the filter tuner changes a conductive angle of the external AC power to an adjusted AC input;

a bridge rectifier receiving the adjusted AC input to generate a DC output;

multiple types of LED modules for emitting lights of multiple color temperatures;

a monitor circuit for monitoring the conductive angle to generate a control signal; and

a current source, according to the control signal, for generating multiple corresponding driving currents respectively supplied to the multiple types of LED modules to mix a desired color temperature, wherein the desired color temperature is associated with the conductive angle according to a predetermined relation, wherein a total light intensity of the multiple types of LED modules is increased when the conducting angle is increasing and is below a first threshold.