OLED Data Driver Using Shared DAC for Brightness Uniformity
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Solution Overview
Problem
The variation in TFT threshold voltage and mobility across different digital-to-analog circuits leads to non-uniform brightness across pixels in TFT-OLED panels due to errors in current output.
Innovation Solution
A data driver with multiple digital-to-analog current converters and voltage storing current copiers/mirrors that convert pixel data into output currents, with secondary converters generating regenerating currents to ensure uniform brightness across pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If separate digital-to-analog converters are used for each pixel column, then conversion can be performed in parallel for all pixels, but component variation in TFT threshold voltage and mobility causes error in current output leading to non-uniform brightness
Solution Approach 1:
The patent merges multiple separate digital-to-analog converter circuits into a single shared converter. Instead of having independent converters for each pixel column (which would cause component variation issues), one converter serves all columns sequentially. This eliminates the manufacturing precision problem while maintaining parallel display output through the pixel structure itself.
Solution Approach 2:
The patent implements periodic action by sequentially enabling different pixel columns at different time periods. The single digital-to-analog converter converts data for one column at a time in a systematic sequence, with each column receiving its drive signal during its designated time slot. This temporal multiplexing maintains productivity while ensuring uniform brightness through consistent conversion conditions.
2Manufacturing precision
If a single shared digital-to-analog converter is used for all pixels, then component variation error is reduced, but conversion must be performed sequentially rather than in parallel
Solution Approach 1:
The patent transitions from spatial parallelism (multiple converters operating simultaneously in different locations) to temporal parallelism (single converter serving multiple locations sequentially). By adding the time dimension to the conversion process, the system achieves both manufacturing precision through a single converter and effective productivity through the pixel structure's inherent parallel display capability.
3Adaptability or versatility
If digital-to-analog converters are distributed across different locations, then each pixel column can be driven independently, but TFT threshold voltage and mobility differences cause current output error
Solution Approach 1:
The patent creates a universal digital-to-analog converter that serves multiple functions - it converts data for all pixel columns sequentially rather than being dedicated to a single column. This multi-functional approach ensures that the same conversion circuitry and reference conditions are used for all columns, eliminating accuracy errors while still allowing independent control of each column through sequential operation.
Data Source
AI summary
A data driver for organic light emitting diode display is disclosed. A pixel data of K bits is divided into an N bits data and an M bits data. A number of N bits data are processed by a number of main digital-to-analog current converters and a number of main voltage storing current copier/current mirror so as to generate a number of main regenerating currents. Besides, a number of M bits data are processed by a number of secondary digital-to-analog current converters and a number of secondary voltage storing current copier/current mirror so as to generate a number of secondary regenerating currents. The brightness of the pixel is related to the sum of the corresponding main regenerating current and the corresponding secondary regenerating current. The invention can reduce the error resulted from the component variation of digital-to-analog converters.