AMOLED IR Drop Compensation via Brightness-Voltage Scaling
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Solution Overview
Problem
Large scale AMOLED display devices experience uneven brightness due to power supply voltage drop (IR Drop), which existing compensation methods, such as internal and external compensation, fail to effectively address in real-time.
Innovation Solution
A method that measures brightness values along each light-emitting element line, calculates and applies voltage compensation values based on a scaling factor to adjust data voltages for adjacent lines, eliminating the need for additional compensation circuits and allowing direct voltage addition to each light-emitting element line.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing internal compensation or external compensation methods are used, then threshold voltage or channel mobility can be compensated, but IR Drop cannot be effectively compensated in real-time
Solution Approach 1:
The patent measures brightness values in advance during a test phase, stores them in a lookup table, and uses these pre-calculated values for real-time compensation during normal operation. This preliminary measurement and storage of brightness data enables fast compensation without complex real-time calculations.
Solution Approach 2:
The patent replaces complex hardware compensation circuits with a software-based lookup table approach. Instead of using additional compensation circuits, the system stores brightness values and their corresponding compensation values in memory, then retrieves and applies them through simple data access operations.
2Illumination intensity
If optical compensation is used to compensate IR Drop, then brightness uniformity can be improved, but real-time compensation cannot be achieved
Solution Approach 1:
Brightness values and compensation values are measured and calculated in advance during a test phase, then stored in a lookup table. During normal display operation, the system simply retrieves the pre-calculated compensation values based on the current display grayscale value, achieving real-time compensation without time-consuming calculations.
Solution Approach 2:
The patent creates a dynamic lookup table that can be updated with different brightness measurements for different display conditions. The compensation values are dynamically selected based on the current grayscale value being displayed, allowing the system to adapt to different operating conditions while maintaining real-time performance.
3Illumination intensity
If additional compensation circuits are added to compensate IR Drop, then brightness uniformity can be improved, but circuit area increases and aperture ratio decreases
Solution Approach 1:
The patent replaces physical compensation circuits with a software-based lookup table implementation. Brightness measurements and compensation values are stored in memory, and the compensation is applied through data retrieval and addition operations rather than additional hardware circuits, thereby eliminating the need for extra circuit area.
Solution Approach 2:
The patent creates a digital copy of the brightness characteristics in the form of a lookup table. Instead of using physical circuits to compensate for IR Drop, the system uses stored brightness data and its corresponding compensation values, which are then applied through software processing.
Data Source
AI summary
The present invention provides a method of compensating AMOLED power supply voltage drop, comprising: step 1, measuring a brightness value L of each light-emitting element line of a panel by starting from a COF end of the AMOLED; step 2, drawing a brightness variation curve of the each light-emitting element line caused by IR Drop according to the brightness value L of the each light-emitting element line measured in the step 1; step 3, calculating a voltage value for compensation of every two adjacent light-emitting elements from difference values between the brightnesses of every two adjacent light-emitting elements according to a ratio conversion between a brightness difference ΔL and a voltage difference ΔV, i.e. ΔV=α·ΔL, wherein α is a scaling factor; step 4, making no compensation to a data voltage of the first light-emitting element line, and adding the first compensation value ΔV1 to a data voltage of the second light-emitting element line, and adding a sum (ΔV1+ΔV2) of the first and the second compensation value to a data voltage of a third light-emitting element line and so on to the last light-emitting element line when a sequence controller transmits data voltage signals for showing images. The method can solve the issue of uneven brightness caused by IR Drop in a large scale AMOLED display device.