OLED Driver Voltage Adjustment for Luminance Uniformity
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Solution Overview
Problem
Organic EL display apparatuses face issues with inconsistent luminance due to temporal variations in the threshold value of thin-film transistors, leading to variations in current flow and poor display quality.
Innovation Solution
A display driver system that adjusts voltage by generating an adjustment voltage based on the characteristics of the pixel drive circuit, using a voltage comparison section to ensure accurate current supply and offset voltage modulation for each display pixel, thereby maintaining consistent luminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If voltage signal control is used for current control, then the display response speed is improved, but the luminance uniformity deteriorates due to threshold value variations
Solution Approach 1:
The patent applies preliminary action by measuring and storing the threshold voltage of each pixel's transistor before normal display operation. This pre-measurement allows the system to compensate for threshold variations during actual display by adjusting the drive voltage based on previously acquired transistor characteristics, thereby maintaining luminance uniformity while preserving the fast response speed of voltage-driven displays.
2Manufacturing precision
If current drive type light-emitting devices are used, then the display quality and luminance are improved, but the complexity of the pixel circuit increases
Solution Approach 1:
The patent extracts the threshold voltage measurement and compensation function from the normal display circuit operation. By separating the characterization phase (measuring transistor parameters) from the display phase (using stored data to drive pixels), the system achieves high display quality through current-driven devices while reducing operational circuit complexity, as the compensation uses pre-stored data rather than requiring complex real-time measurement circuits during display.
3Manufacturing precision
If threshold value compensation is implemented, then the luminance uniformity is improved, but the device complexity increases due to additional circuits
Solution Approach 1:
The patent implements preliminary action by performing threshold voltage measurement and storing compensation data before normal display operation. This approach eliminates the need for complex real-time compensation circuits during display, as the system uses pre-acquired transistor characteristics to calculate and apply appropriate drive voltages, thereby achieving luminance uniformity with minimal additional circuit complexity during operational phases.
Solution Approach 2:
The patent applies feedback by using the measured threshold voltage information to adjust and optimize the drive signal for each pixel. The system feeds back the characterized transistor parameters into the display drive circuitry, allowing dynamic compensation of threshold variations and achieving uniform luminance across all pixels while maintaining relatively simple circuit architecture.
Data Source
AI summary
A display apparatus includes: a light-emitting device; a pixel circuit which is connected to the light-emitting device; a display driver having a voltage adjustment section which adjusts the potential of an adjustment voltage such that the potential thereof is approximated to a potential which is changed in accordance with the change amount of the characteristics inherent to the pixel circuit when a reference current having a predetermined current value is supplied to the pixel circuit; and a data line which connects the display driver and pixel circuit.