1. Technical Field
The present disclosure relates to an organic light-emitting diode (OLED) display capable of driving at a low speed and a method of driving the same.
2. Discussion of the Related Art
An active matrix OLED display includes organic light-emitting diodes (OLEDs) capable of emitting light by themselves (i.e., self-emitting), and has advantages of a fast response time, a high emission efficiency, a high luminance, and a wide viewing angle. Each OLED includes an anode electrode, a cathode electrode, and an organic compound layer between the anode electrode and the cathode electrode. The organic compound layer includes a hole injection layer HIL, a hole transport layer HTL, an emission layer EML, an electron transport layer ETL, and an electron injection layer EIL. When a driving voltage is applied to the anode electrode and the cathode electrode, holes passing through the hole transport layer HTL and electrons passing through the electron transport layer ETL move to the emission layer EML and form excitons. As a result, the emission layer EML generates visible light.
To reduce power consumption of the OLED display when there is a small change in an input image of the OLED display, a technology for driving the pixels at a low speed has been known. Because a refresh cycle of display data lengthens during a low-speed drive, image quality of the OLED display may be reduced. A main cause of reduction in the image quality is because a voltage level of an emission control signal changes during a data holding period in the low-speed drive.
More specifically, the OLED display controls the emission of the pixels through the emission control signal, and the emission control signal is generated by an emission driver. The emission driver may be directly formed in a non-display area (e.g., a bezel area) of a display panel. The emission driver includes a shift register generating an anti-phase emission control signal and an inverter that inverts a phase of the anti-phase emission control signal and generates an emission control signal. Output lines of the shift register for outputting the anti-phase emission control signal are connected to input terminals of the inverter. In this instance, the output lines of the shift register are disposed to intersect clock lines of the inverter to prevent an increase in the size of the bezel area attributable to the emission driver. At least one insulating layer is positioned between the output lines of the shift register and the clock lines of the inverter. Thus, the output lines of the shift register and the clock lines of the inverter are connected to each other through a parasitic capacitor.
As shown in FIG. 1, a ripple is generated in an anti-phase emission control signal EMB applied to output lines of a shift register because of an influence of emission shift clocks through a parasitic capacitor during a data holding period in a low-speed drive. The ripple reduces off-characteristics of some switches included in an inverter, and thus, drops a voltage level of an emission control signal EM output from the inverter. A reduction in the voltage level of the emission control signal EM changes an amount of electric current applied to OLEDs of the pixels, leading to a luminance drop.