An organic light emitting display includes an organic light emitting display panel, a temperature detecting unit for detecting a temperature of the organic light emitting display panel, a driving voltage determining unit for outputting voltage data by calculating the driving voltage of the organic light emitting display panel on the basis of the temperature data detected by the temperature detecting unit, and a DC/DC converter having a variable resistor determining unit for setting a variable resistor on the basis of the voltage data output from the driving voltage determining unit, the DC/DC converter supplying the driving voltage corresponding to the variable resistor to the organic light emitting display panel.