A power supply device supplying power to a data driver of a light emission display device. The power supply device includes: an external reference voltage supply supplying an external reference voltage; a reference voltage generator converting external power into a regulated direct current (DC) reference voltage and outputs the regulated DC reference voltage when the external power is changed. A reference voltage selector selects one of the reference voltages output from the external reference voltage supply and the reference voltage generator and outputs a selected reference voltage. A voltage converter converts the regulated reference voltage output from the reference voltage selector into a plurality of internal DC power sources to be supplied to the drivers.