Display device and related operating method

An organic light emitting display device comprising:

• a display panel comprising a plurality of scan lines, a plurality of data lines, and a plurality of pixels connected to the plurality of scan lines and to the plurality of data lines;
• a power supply for supplying a first pixel voltage and a second pixel voltage to the plurality of pixels;
• and
• a display driver configured to control the display panel,
• wherein the display panel displays a first image in a first frame frequency during a first driving mode, and displays a second image in a second frame frequency that is lower than the first frame frequency during a second driving mode, according to a control by the display driver,
• wherein the power supply adjusts at least one level of the first pixel voltage and the second pixel voltage such that a voltage difference between the first pixel voltage and the second pixel voltage during the second driving mode is smaller than a voltage difference between the first pixel voltage and the second pixel voltage during the first driving mode, and
• wherein the first pixel voltage during the second driving mode is set to a lower voltage level than during the first driving mode, and the second pixel voltage during the second driving mode is set to a higher voltage level than during the first driving mode.