OLED Pixel Circuit Timing Compensation for Color Dragging
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Solution Overview
Problem
In OLED displays, the difference in capacitance between sub-pixels of different colors leads to a time difference in light emission, causing the phenomenon of color dragging, where one color is perceived as leading while another lags, due to varying electric current requirements and timing discrepancies.
Innovation Solution
The implementation of a driving circuit with timing compensating capacitors in each sub-pixel, connected to control and light emitting signal lines, ensures synchronized light emission by adjusting the anode voltage levels, thereby minimizing the delay time between signal supply and actual light emission across different sub-pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If different driver circuits are designed for different color sub-pixels to match their specific electrical characteristics, then each sub-pixel can achieve optimal light emission, but the capacitance differences cause time differences in light emission timing leading to color dragging
Solution Approach 1:
The patent applies parameter changes by introducing timing compensating capacitors with specific capacitance values into the pixel circuits of different color sub-pixels. These capacitors adjust the charge storage and discharge characteristics, thereby modifying the timing parameters of light emission to synchronize across all color sub-pixels, eliminating color dragging while maintaining optimized driver circuit designs for each color.
2Loss of time
If timing compensating capacitors are added to each sub-pixel pixel circuit to synchronize light emission timing, then color dragging is reduced, but the device complexity and manufacturing steps increase
Solution Approach 1:
The patent implements preliminary action by incorporating timing compensating capacitors into the pixel circuits during the manufacturing process. These capacitors are pre-installed with calculated capacitance values that compensate for the inherent timing delays of different color sub-pixels. This preliminary configuration ensures that when the display operates, all sub-pixels emit light simultaneously without requiring additional active timing control mechanisms, thus reducing the actual operational complexity despite the increased component count.
3Device complexity
If the same driver circuit is used for all color sub-pixels to simplify design, then device complexity is reduced, but the different capacitance values of different color OLEDs cause timing differences and color dragging
Solution Approach 1:
The patent applies local quality by maintaining a unified driver circuit design for all color sub-pixels while introducing local timing compensating capacitors specific to each sub-pixel's requirements. This approach preserves the simplicity and standardization benefits of a common driver circuit architecture while addressing the individual timing needs of red, green, and blue sub-pixels through localized capacitor additions, thereby achieving both design simplicity and emission synchronization.
Data Source
AI summary
An organic light-emitting diode (OLED) display is disclosed. In one aspect, the OLED display includes a display unit and a plurality of pixels over the display unit. Each of the pixels comprises first and second sub-pixels each comprising an OLED and a pixel circuit. Each pixel circuit is connected to a first node and a first control line that is configured to supply a first control signal having a rising edge prior to a time when the OLED emits light in a frame. Each pixel circuit is further connected to a second node and a light emitting signal line that is configured to supply a light emitting signal having a falling edge prior to a time when the OLED emits light in the frame. The pixel circuit of the first sub-pixel comprises a first timing compensating capacitor connecting the first node and an anode of the OLED.