OLED Pixel Circuit Compensation Module for Brightness Uniformity
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Solution Overview
Problem
In OLED display panels, inconsistent threshold voltages of driving transistors lead to uneven brightness (mura) due to variations in carrier mobility caused by manufacturing processes, which worsens with increased resolution, reducing the effectiveness of threshold voltage compensation.
Innovation Solution
A pixel circuit with a compensation module, resetting module, writing module, driver module, and light emission enabling module, where the compensation module adjusts the pulse width of its output signal to extend threshold voltage compensation time, independent of scanning signal line pulse width, thereby reducing the impact of resolution on compensation time and improving brightness uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the resolution of OLED display panel is increased, then the definition of displayed image is improved, but the scanning time for each row of subpixels is decreased, which reduces the threshold voltage compensation time and worsens the brightness uniformity
Solution Approach 1:
The patent divides the control signals into separate independent lines: a scanning signal line for controlling the writing module and a compensation signal line for controlling the compensation module. This segmentation allows the compensation process to be independently timed and controlled, decoupling it from the scanning time constraints imposed by high resolution displays.
Solution Approach 2:
The compensation module performs threshold voltage compensation in advance during the compensation phase before the light emission phase begins. By using the compensation signal line to enable the compensation module independently, the compensation action is completed preliminarily, ensuring adequate time for compensation regardless of the scanning time available for data writing.
2Speed
If the pulse width of scanning signal line output signal is reduced to accommodate higher resolution, then the scanning speed is improved, but the compensation time becomes insufficient, worsening the threshold voltage compensation effectiveness
Solution Approach 1:
The patent segments the control signals into separate scanning signal and compensation signal lines, allowing independent optimization of their pulse widths. The compensation signal line can maintain a sufficient pulse width for accurate threshold voltage compensation even when the scanning signal line uses reduced pulse widths for high-speed scanning in high resolution displays.
Solution Approach 2:
The patent enables dynamic control of the compensation module through the compensation signal line, which can be independently adjusted in pulse width and timing. This dynamic control allows the system to adapt compensation duration to the specific requirements of different resolution displays, ensuring sufficient compensation time regardless of scanning speed requirements.
3Stability of the object's composition
If the threshold voltage compensation time is extended independently of scanning signal, then the brightness uniformity is improved, but the circuit complexity increases due to additional compensation signal line and control modules
Solution Approach 1:
The patent adds a compensation signal line and compensation module that work independently from the scanning signal path. This segmentation allows extended compensation time without affecting the scanning operation, improving brightness uniformity while keeping the additional circuitry focused and modular rather than distributed throughout the entire display circuit.
Solution Approach 2:
The compensation module controlled by the compensation signal line serves multiple functions: it compensates for threshold voltage variations across different subpixels, operates independently of the scanning rate, and can be adapted to various resolution requirements. This multi-functionality justifies the added circuit complexity by providing versatile compensation capabilities that improve overall display performance.
Data Source
AI summary
A pixel circuit includes a compensation module, a resetting module, a writing module, a driver module, a light emission enabling module, and a light emitting device. The resetting module is configured to reset the driver module and the light emitting device; the compensation module performs threshold voltage compensation on the driver module; the writing module is configured to write, to the driver module, a data voltage that is output by a data line; the light emission enabling module is configured to provide a voltage of a first supply voltage end to the driver module; the driver module is configured to provide, under action of the voltage output by the first supply voltage end, a drive current to the light emitting device; and the light emitting device is configured to emit light based on the drive current. The pixel circuit is configured to drive to display a subpixel.