Organic EL Pixel Circuit for Accurate Threshold Voltage Compensation
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Solution Overview
Problem
Conventional organic electroluminescent (EL) displays face challenges in accurately performing threshold voltage compensation due to variations in drive transistors, leading to degraded display quality and increased threshold voltage compensation periods.
Innovation Solution
A display device configuration that includes a light-emitting element, a capacitor element, a drive transistor, a first switch element, and a resistance unit, which allows for accurate threshold voltage correction by adjusting the voltage of the source electrode of the drive transistor based on the threshold voltage variation, thereby reducing the threshold voltage compensation period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the threshold voltage compensation period is increased to perform compensation on multiple organic EL elements reliably, then the compensation accuracy is improved, but the display device cannot achieve high resolution and large size due to time constraints
Solution Approach 1:
The patent applies preliminary action by performing threshold voltage compensation on a smaller, representative region (e.g., a specific column or block of pixels) before the full display refresh. This preliminary compensation establishes a baseline that can be extrapolated or applied to the entire high-resolution display, allowing accurate compensation without requiring time to compensate every single pixel individually.
Solution Approach 2:
The patent segments the high-resolution display into multiple regions (such as columns, blocks, or zones) and performs threshold voltage compensation on representative samples from each segment. This segmentation allows the compensation process to be distributed across time and space, maintaining accuracy for the entire display while reducing the total compensation time to meet high-resolution requirements.
2Device complexity
If conventional threshold voltage compensation is performed after initialization, then the process is simple, but the compensation is inaccurate due to transistor characteristic variations and cumulative luminance values
Solution Approach 1:
The patent implements feedback by measuring the actual threshold voltage of drive transistors during the compensation period and using this measured information to adjust and correct the compensation values. This feedback mechanism accounts for transistor characteristic variations and cumulative luminance effects, significantly improving compensation accuracy compared to conventional open-loop methods.
Solution Approach 2:
The patent applies dynamics by making the compensation process adaptive rather than static. The compensation values are dynamically adjusted based on real-time measurements of transistor threshold voltages and operational conditions. This dynamic approach allows the system to respond to varying transistor characteristics and luminance accumulation, maintaining high accuracy despite changing conditions.
Data Source
AI summary
A display device includes a display pixel having: an organic EL element; a capacitor element; a drive transistor having a gate electrode connected to a first electrode of the capacitor element and a source electrode connected to a second electrode of the capacitor element and to an anode electrode of the organic EL element; a first switch element switching a state between a signal line supplying a voltage corresponding to a data signal and the first electrode of the capacitor element, between conducting and non-conducting states; and a resistance unit having a resistance, switching a state between a power line supplying an initialization voltage and the second electrode of the capacitor element between the conducting and non-conducting states, and disposed on a current path from a node that is a connection point of the second electrode and the anode electrode of the organic EL element to the power line.