An organic light emitting display includes a first power block for receiving a first input voltage to output a first output voltage and configured to be driven in a normal operation mode corresponding to an enable signal, a second power block for receiving a second input voltage to output a second output voltage and configured to be driven in an alternate operation mode corresponding to the enable signal, and a voltage input unit for transmitting the first input voltage to the first power block in the normal operation mode, and for transmitting the second input voltage to the second power block and stopping the transmitting of the first input voltage to the first power block in the alternate operation mode, corresponding to the enable signal.