A display device includes a power supply generating a first power voltage, a second power voltage, and a third power voltage. The display device further includes a first power line to which the first power voltage is applied, a second power line to which the second power voltage is applied, and a readout line to which the third power voltage is applied. The display device further includes a display panel, which includes a pixel. The pixel includes a light emitting element connected between the first power line and the second power line, and a switching transistor connected between one electrode of the light emitting element and the readout line. The power supply changes a voltage level of the third power voltage based on a total current flowing from the power supply to the display panel according to the first and second power voltages.