A New IR-Drop Model That Improves Effectively the Brightness Uniformity of an AMOLED Panel

Abstract

A new model characterizing the IR drop in an active-matrix organic light-emitting diode (AMOLED) display is built successfully by this study, which can be used to effectively improve brightness uniformity by adjusting gray levels addressed accordingly to pixels in the panel. The IR-drop refers to the voltage drops along the thin power lines from the external driver at panel edge to internal pixels. The built IR-drop model is in a form of vector and matrix with parameters and variables such as equivalent resistances of horizontal/vertical power lines and the current through the drive thin film transistors (TFTs) and OLEDs in pixels. With precisely calibrated parameters, the model can be solved for the voltage drops at given sub-pixels in the AMOLED panel. Based on the solved dropped voltages at each pixel, the gray level assigned to the pixel $V_{data}$ can be adjusted accordingly to restore the desired pixel luminance. The proposed compensation was implemented in a 14-inch AMOLED panel with FHD resolution for performance validation. The experimental results show less than 2.5% of prediction error on voltage drops, leading to effective compensations that improves the measured pixel currents from 66.1% to 89.7%, 70.3% to 92.9%, and 48.8% to 85.1% of the desired, non-dropped currents, respectively, for red, green, and blue illuminance at the L255 gray level. Also from experiments are substantial improvements of 21.7%, 21.5%, and 35.3% on the brightness uniformity of the panel displayed for red-, green-, blue-images at L255 gray, respectively.

Keywords

• IR-drop
• brightness uniformity
• voltage drop
• compensation
• iterative numerical analysis
• drive thin film transistor (DTFT)