Some lighting apparatuses using light emitting diodes produce emotion lighting to create unique atmospheres as well as perform their inherent lighting function. White light emitted from lighting apparatuses can be divided into warm white and cool white by its correlated color temperature (CCT). Warm white gives a warm feeling whereas cool white gives a cool feeling. White light having a correlated color temperature of 3000 K or less and white light having a correlated color temperature of 5000 K or more are commonly called “warm white” and “cool white”, respectively, although their correlated color temperatures are slightly different depending on the classification criteria. FIG. 1 illustrates a conventional lighting apparatus capable of switching warm white to and from cool white to change the lighting effect and an atmosphere. In the lighting apparatus illustrated in FIG. 1, a first light emitting unit 10 emitting warm white light and a second light emitting unit 20 emitting cool white light are arranged simultaneously. The correlated color temperature of light can be controlled by optionally operating either the first light emitting unit 10 or the second light emitting unit 20. The light emitting units are selectively connected to a direct current power supply unit 1 through switches S1 and S2.
However, the use of either of the two light emitting units 10 and 20 for warm white or cool white light emission instead of both the light emitting units is costly and causes poor efficiency. Thus, there is a need in the art for an approach that can provide a solution to the problems of the prior art.