A power supply includes a transformer to transform an input voltage into an output driving voltage for one of a plurality of components of an image forming apparatus, and an output converter to detect the driving voltage being output from the transformer, to amplify the detected driving voltage according to a power control signal, and to output the amplified driving voltage to at least one remaining component in the plurality of components of the image forming apparatus. The power supply can not only control high voltage outputs individually, but also reduces the number of switching transformers being used, as it uses at least one shared switching transformer.