A lighting apparatus includes a light source, a rectifier circuit, a DC-DC converter, an adjustment circuit and a controller. The rectifier circuit converts an AC power to a raw direct current. The adjustment circuit provides an adjustment signal corresponding a light intensity setting of the light source. The controller is coupled to the DC-DC converter and the adjustment circuit. The controller receives the adjustment signal for generating a first PWM signal. The DC-DC converter receives the first PWM signal. The DC-DC converter converts the raw direct current to an output current according to a first duty ratio of the first PWM signal. The output current is supplied to the light source corresponding to the light intensity setting.