OLED Pixel Circuit Brightness Uniformity via Horizontal Power Source Line Initialization
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Solution Overview
Problem
Organic light emitting displays face challenges in achieving uniform brightness due to the initialization of gate electrodes of driving transistors by voltages that are not adjusted for different gray levels, leading to variations in displayed images.
Innovation Solution
The implementation of a scan driver and data driver system that supplies specific voltages to pixels through horizontal power source lines, using storage capacitors to control the gate electrodes of driving transistors, and employing switching elements to manage these voltages, ensuring that the gate electrodes are initialized by voltages corresponding to data signals, thereby maintaining uniform brightness across different gray levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If gate electrodes are initialized by fixed voltages, then the circuit structure is simple, but brightness uniformity deteriorates
Solution Approach 1:
The patent applies preliminary action by initializing the gate electrode voltage to match the data signal voltage before the pixel operates. The scan driver proactively sets the horizontal power source line voltage to correspond to the data signal voltage in advance, ensuring that when the pixel begins operation, the gate electrode is already at the correct potential to maintain uniform brightness across different gray levels.
2Illumination intensity
If additional initializing wiring lines are added, then brightness uniformity is improved, but device complexity increases
Solution Approach 1:
The patent applies universality by making the horizontal power source line serve multiple functions. This line not only supplies power to the pixels but also acts as an initialization line that sets the gate electrode voltage to match the data signal voltage. By combining these functions into a single existing line, the patent achieves brightness uniformity without adding separate initializing wiring.
Solution Approach 2:
The patent applies self-service by enabling the horizontal power source line to automatically initialize itself and the gate electrodes to the correct voltage levels. The scan driver controls this line to proactively establish the proper voltage correspondence with data signals, eliminating the need for external or additional initialization circuits.
3Use of energy by moving object
If gate electrode voltages are not adjusted for different gray levels, then power consumption is low, but image quality deteriorates
Solution Approach 1:
The patent applies preliminary action by pre-adjusting the horizontal power source line voltage to correspond to the data signal voltage before pixel operation begins. This proactive voltage matching ensures that gate electrodes are initialized to the correct levels for different gray levels, enabling high image quality without requiring continuous power adjustment during operation.
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
This solution allows for the display of images with improved uniform brightness by ensuring that the gate electrodes of driving transistors are initialized with voltages matching the data signals, regardless of gray levels, and eliminates the need for additional initializing wiring lines.
Implementation Method 1
organic light emitting displays display images using organic light emitting diodes (OLEDs) that generate light by re-combination of electrons and holes
Implementation Method 2
The storage capacitors included in the pixels charge voltages corresponding to the data signals
Data Source
AI summary
An organic light emitting display capable of displaying an image with desired brightness. The organic light emitting display includes a scan driver for supplying a first scan signal to first scan lines, for supplying a second scan signal to second scan lines, and for supplying emission control signals to emission control lines, a data driver for supplying data signals to data lines, horizontal power source lines extending in parallel with the first scan lines at horizontal lines, and configured to receive a fourth voltage in a first period of a period in which the first scan signal is supplied, and configured to receive a third voltage that is lower than the fourth voltage in a second period excluding the first period, and pixels positioned at crossing regions of the first scan lines and the data lines. Each of the pixels includes an OLED, a first transistor, and a storage capacitor.