A projection device includes a plurality of solid-state lighting sources driven by a DC drive power to sequentially provide a first light generated by a first number of light sources, a second light generated by a second number of light sources and a third light generated by a third number of light sources within a response cycle; and a color wheel having a first block, a second block and a third block, respectively corresponding to the first to third lights, so that the projection device sequentially outputs a first color light with a first brightness, a second color light with a second brightness and a third color light with a third brightness. The brightness of the first to third lights is controlled by number of light sources to be turn on.