Display Driver Correction Circuit for Horizontal Gradation Lines
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Solution Overview
Problem
Display panels, such as OLED and liquid crystal display panels, experience visible defects due to variations in voltages supplied, leading to image quality issues like horizontal gradation lines when grayscale values change.
Innovation Solution
A display driver with correction circuitry that adjusts image data for each line based on the difference in currents between adjacent lines, using average picture level (APL) calculations and lookup tables to correct for voltage variations, thereby minimizing the impact of power supply voltage changes across the display panel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If grayscale values are changed to display different images, then display content variety is improved, but horizontal gradation lines appear due to voltage variations
Solution Approach 1:
The correction circuit pre-calculates and stores correction values in a lookup table before displaying images. When a grayscale value change is detected, the corresponding correction value is immediately applied without real-time calculation, preventing horizontal gradation lines before they can appear.
Solution Approach 2:
The system monitors grayscale value changes in display data and uses this feedback to select appropriate correction values from the lookup table. This closed-loop approach ensures that voltage variations are compensated in real-time based on actual display conditions.
2Manufacturing precision
If correction processing is applied to each line, then image quality is improved, but processing time increases
Solution Approach 1:
Correction values for all possible grayscale transitions are pre-calculated and stored in a lookup table during manufacturing or initialization. During actual display operation, the correction circuit only needs to retrieve the appropriate value from the table based on the current grayscale change, eliminating the need for time-consuming real-time calculations.
Solution Approach 2:
Instead of performing complex correction calculations for each line, the system uses a copied lookup table structure where correction patterns are stored once and reused repeatedly. This allows rapid retrieval of correction values without re-computing them for each display line.
3Illumination intensity
If voltage supply is increased to improve brightness, then illumination intensity is improved, but visible defects increase due to voltage variations
Solution Approach 1:
The correction circuit dynamically adjusts the grayscale values based on detected voltage variations. When voltage changes are detected, the lookup table provides corresponding correction parameters that modify the display data to compensate for the voltage fluctuation, maintaining consistent image quality across different brightness levels.
Data Source
AI summary
A display driver comprises correction circuitry configured to correct a first image data for a first line, based on a difference between a first current and a second current. The first current is for displaying the first line and the second current is for displaying a second line after the first line is displayed.