An OLED display is disclosed. The display includes a display panel having a luminance level of the display panel, a power supply unit providing first and second power voltages to the display panel, and a gamma reference voltage generator configured to i) generate a compensation gamma reference voltage, ii) detect a voltage level of the first power voltage at a detection point of the display panel, ii) change the compensation gamma reference voltage from a first voltage level to a second voltage level within a frame based at least in part on the detected voltage level, and iv) determine the first voltage level of the compensation gamma reference voltage based at least in part on the luminance level.