As a result, the color representation capability of the corresponding light emitting device is degraded. Thus, if an image on a screen is changed, there occurs a burn-in phenomenon in which a screen is not displayed clearly as if an afterimage of a previous image remains or a screen is stained.

An afterimage compensation method is used for solving the problem that an afterimage of a previous image remains on a screen.

The afterimage compensation method compensates for brightness reduced by deterioration of pixels, and requires a cooling time which is a time for turning off a display panel for a predetermined time. If a cooling time is not ensured for a sufficient time, the temperature of the display panel increases, and thus a voltage is excessively sensed. Thus, the accuracy of afterimage compensation may be reduced.

If AC power is off, the processor of the OLED display apparatus cannot measure the cooling time. Thus, if AC power is turned on after the AC power is turned off, the screen may be turned off so as to secure the cooling time of the display panel.

In this case, a user cannot use the display panel for a predetermined time because the screen is turned off. In particular, in a case where the display panel must be immediately used for promotion, just like TVs displayed in stores, store users may suffer great inconvenience because the screen is turned off so as to secure the cooling time.

Meanwhile, a battery and a real time check (RTC) circuit have been used for measuring the cooling time. However, the configuration of the battery and the RTC circuit is expensive, and the use of the battery is not permanent.