OLED Pixel Circuit Bias Compensation for Low-Refresh Flicker
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Solution Overview
Problem
Display panels using organic light-emitting technology experience abnormal brightness and screen smear due to changes in drive transistor characteristics during low refresh rate picture switching, leading to picture flicker and poor visual experience.
Innovation Solution
A display panel design with a pixel circuit that includes a drive circuit, data write circuit, and bias compensation circuit, featuring multiple bias compensation stages within a frame to dynamically adjust the bias effect of the drive transistor, reducing the need for driver chip architecture adjustments and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bias compensation is applied to improve drive transistor performance, then the bias effect is improved, but the device complexity increases due to additional circuits and stages
Solution Approach 1:
The bias compensation process is segmented into multiple stages: a first bias compensation stage after data writing and multiple second bias compensation stages during the retention stage. This segmentation allows the drive transistor to receive targeted bias compensation at different times, improving overall performance while managing circuit complexity through temporal division rather than simultaneous complex circuitry.
Solution Approach 2:
The first bias compensation stage is performed preliminarily after data writing but before the retention stage begins. This preliminary action prepares the drive transistor by establishing initial bias conditions, ensuring optimal performance at the start of the retention stage and reducing the burden on subsequent compensation stages.
2Reliability
If multiple bias compensation stages are implemented, then picture flicker is reduced, but the power consumption increases
Solution Approach 1:
Multiple second bias compensation stages are implemented periodically during the retention stage at predetermined time intervals. This periodic action maintains drive transistor performance throughout the retention period, reducing picture flicker while controlling power consumption by activating compensation only at specific intervals rather than continuously.
Solution Approach 2:
The bias compensation voltage signal parameters are dynamically adjusted based on the stage and timing. By optimizing voltage levels and pulse widths for each compensation stage, the system achieves effective flicker reduction while minimizing unnecessary power consumption from excessive or improperly sized compensation signals.
3Manufacturing precision
If bias compensation circuits are added, then manufacturing precision is improved, but manufacturing cost increases
Solution Approach 1:
The bias compensation circuit is designed to perform multiple functions: it provides threshold voltage compensation, maintains drive current stability, and reduces picture flicker. By making the circuit multi-functional, the patent achieves improved manufacturing precision without proportionally increasing complexity and cost, as a single circuit structure serves multiple compensation purposes.
Solution Approach 2:
The bias compensation circuit is integrated with the existing pixel circuit structure, merging compensation functions into the overall display panel architecture. This integration approach allows for shared manufacturing processes and reduces the need for completely separate compensation circuitry, thereby controlling manufacturing costs while achieving precise drive transistor control.
Data Source
AI summary
Provided is a display panel includes a pixel circuit and a light-emitting element. The pixel circuit includes a drive circuit, a data write circuit and a bias compensation circuit. The operation process of the pixel circuit includes a data write stage, a first bias compensation stage and a second bias compensation stage. In the data write stage, the data write circuit is turned on, and a data voltage terminal writes a data voltage signal to a first terminal of the drive circuit. In the first bias compensation stage, the data write circuit is turned on, and the data voltage terminal writes the data voltage signal to the first terminal of the drive circuit. In the second bias compensation stage, the bias compensation circuit is turned on, and a bias compensation voltage terminal writes a bias adjustment voltage signal to the first terminal of the drive circuit.