A driving circuit for controlling power of a light-emitting diode (LED) light source includes a transformer, a switch controller, and a dimming controller. The transformer has a primary winding that receives input power from an AC/DC converter and a secondary winding that provides output power to the LED light source. The switch controller coupled between an optical coupler and the primary winding receives a feedback signal indicative of a target level of a current flowing through the LED light source from the optical coupler, and controls input power to the primary winding according to the feedback signal. The dimming controller coupled to the secondary winding receives a switch monitoring signal indicative of an operation of a power switch coupled between an AC power source and the AC/DC converter, and regulates the output power by adjusting the feedback signal according to the switch monitoring signal.