AMOLED Data Voltage Control Circuit for Uniform Light Output
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Solution Overview
Problem
In organic electroluminescent displays, the voltage supplied to driving transistors varies due to losses along the electric path, causing inconsistent light intensities across different positions in the display, even when the same data voltage is applied, leading to undesirable variations in light emission.
Innovation Solution
A control circuit that adjusts the extreme data voltages VGMA_H and VGMA_L using an auxiliary operational amplifier to compensate for voltage fluctuations by generating a common voltage based on the difference between the effectively supplied voltage ELVDD′ and a reference voltage, ensuring consistent light intensity across the display without requiring information about the pixel's position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If data voltages are applied to driving transistors in high-resolution AMOLED displays, then light emission is achieved, but voltage losses along the electric path cause inconsistent light intensity across different positions
Solution Approach 1:
The patent implements a feedback mechanism by sensing the actual voltage ELVDD' supplied to the electroluminescent component and using this information to adjust the data voltages. The control circuit monitors the voltage drop along the electric path and compensates for it by modifying the data voltages accordingly, ensuring consistent light intensity across all pixel positions despite voltage losses.
Solution Approach 2:
The patent changes the parameters of the data voltages (VGMA_H and VGMA_L) based on the sensed voltage ELVDD'. By adjusting these voltage parameters dynamically according to the actual supply voltage conditions, the system compensates for voltage losses and maintains uniform illumination intensity across the display.
2Illumination intensity
If voltage compensation is implemented to correct light intensity inconsistencies, then illumination uniformity improves, but control circuit complexity increases
Solution Approach 1:
The control circuit performs self-adjustment by automatically sensing the voltage ELVDD' and correcting its own data voltage outputs without requiring external intervention or complex external compensation circuits. This self-service approach maintains illumination uniformity while minimizing additional circuit complexity.
Solution Approach 2:
The patent merges the voltage sensing function and the data voltage generation function into a single integrated control circuit. By combining these functions, the system achieves voltage compensation without requiring separate complex compensation circuits, thus improving light intensity uniformity while controlling overall device complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively compensates for voltage drops along the supply path, maintaining consistent light intensity across the display, even for high-resolution AMOLED displays, without altering the desired range of data voltage variations, and can be implemented in a simple and integrated form.
Implementation Method 1
They exploit the phenomenon of electroluminescence, in which differential energy is discharged as light when the electronic state of a material (typically an organic electroluminescent component) is changed from a ground state to an excited state by an electric field and the electronic state is returned from an unstable excited state to a stable ground state.
Data Source
AI summary
A control circuit is for generating upper and lower voltages that define a range of a data voltage for controlling a driving transistor of an electroluminescent component coupled to a supply line through the driving transistor. The control circuit may include a first input terminal configured to have a common voltage, and a pair of amplifiers coupled together at the first input terminal and configured to generate the upper voltage and the lower voltage to correspond to a difference between the common voltage and, respectively, first and second analog intermediate voltages representing respective threshold values of the upper voltage and of the lower voltage. The control circuit may include an auxiliary amplifier configured to adjust the upper voltage and the lower voltage based upon fluctuations of an input voltage, and generate the common voltage to correspond to the difference between the input voltage and a reference voltage.