OLED Pixel Circuit Sensing for Color Coordinate Stability
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Solution Overview
Problem
In OLED display apparatuses, image quality degradation phenomena such as color coordinate changes occur during driving, leading to a degradation of high image quality.
Innovation Solution
A pixel circuit and display apparatus that includes a transistor configured to receive a sensing signal, compensating for degradation of a light emitting element through sensing, thereby enhancing image quality. The pixel circuit comprises a light emitting element, a capacitor, and multiple transistors that work together to supply reference voltages, drive currents, and initialization voltages to maintain and improve image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If OLED light emitting elements are used to achieve self-luminous display with high contrast ratio and wide viewing angle, then display performance is improved, but image quality degradation such as color coordinate change occurs during driving
Solution Approach 1:
The pixel circuit performs preliminary sensing of the light emitting element's characteristics during the blanking period before actual image display. The sensing unit measures threshold voltage and mobility of the OLED element in advance, allowing the driving transistor to be pre-configured with appropriate drive voltages that compensate for expected degradation during operation.
Solution Approach 2:
The sensing unit continuously monitors the light emitting element's characteristics and provides feedback signals to the driving transistor. Based on this feedback about threshold voltage and mobility changes, the system dynamically adjusts drive voltages to maintain stable color coordinates and image quality throughout the display operation period.
2Reliability
If a sensing unit is added to detect and compensate for light emitting element degradation, then image quality is enhanced, but device complexity increases
Solution Approach 1:
The sensing unit is merged with the existing pixel circuit structure, sharing common components such as the transistor and capacitor. The sensing unit utilizes the same physical infrastructure as the driving circuit, with the sensing transistor and capacitor working in conjunction with the driving transistor to perform both sensing and driving functions without requiring entirely separate dedicated components.
Solution Approach 2:
The pixel circuit is designed with multi-functionality where the same transistor and capacitor components serve dual purposes: they function as both sensing elements for detecting OLED characteristics and as driving elements for controlling the light emitting element. This universal design reduces the overall component count while enabling both sensing and driving capabilities.
Data Source
AI summary
A display apparatus, a pixel circuit and a controlling method of pixel circuit are disclosed. The display apparatus includes a display panel with a plurality of data lines, a plurality of gate lines, and a plurality of pixels disposed thereon, the display panel being configured to operate in a display mode for displaying an image and a sensing mode for sensing degradation of the pixels, a gate driver configured to supply a scan signal and an emission control signal to the plurality of gate lines, a data driver configured to supply a data signal to the plurality of data lines, a power supply configured to apply an initialization voltage to the pixels in the sensing mode, and a sensing unit configure to sense degradation of the pixels in the sensing mode.