Organic Light Emitting Display Pixel Circuit Threshold Voltage Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Organic light emitting display devices face luminance deviations due to varying threshold voltages of driving transistors and have low luminous efficiency and durability due to high non-emission periods in simultaneous emission driving methods.
Innovation Solution
The organic light emitting display device employs a panel driver that provides specific gate and power signals to pixels, including PMOS and NMOS transistors, to compensate threshold voltages and adjust voltages during emission periods, reducing non-emission time and enhancing luminous efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If simultaneous emission driving method is used to secure threshold voltage compensation time, then threshold voltage compensation is improved, but luminous efficiency deteriorates due to high non-emission period ratio
Solution Approach 1:
The pixel circuit is segmented into multiple transistors (first transistor for threshold voltage compensation, second transistor for luminance control) that operate in different time periods. The first transistor handles threshold voltage compensation during non-emission periods while the second transistor controls luminance during emission periods, allowing parallel operation that resolves the contradiction between compensation time and emission time.
2Ease of manufacture
If conventional pixel circuit is used, then manufacturing is simpler, but luminance deviation occurs due to threshold voltage variations
Solution Approach 1:
The pixel circuit incorporates a feedback mechanism where the first transistor's gate electrode receives a feedback signal based on the voltage at its source electrode, which reflects the threshold voltage. This feedback loop automatically compensates for threshold voltage variations caused by manufacturing process errors, improving luminance uniformity without significantly complicating the manufacturing process.
3Productivity
If emission period is increased to improve luminous efficiency, then durability is improved, but threshold voltage compensation time is reduced
Solution Approach 1:
The pixel circuit dynamically switches between different operating modes using control signals (first control signal for threshold voltage compensation mode, second control signal for luminance control mode). This dynamic switching allows the circuit to adapt its function based on the current time period, ensuring both adequate compensation time and sufficient emission time without compromising either luminous efficiency or compensation accuracy.
Data Source
AI summary
An organic light emitting display device which secures a sufficient compensation time during which a threshold voltage of a driving transistor is compensated by driving a display panel using a simultaneous emission driving method by which a plurality of pixels simultaneously emit light. The organic light emitting display device may reduce a length (or, a time) of a non-emission period by storing a data signal of a current frame into a second capacitor of the pixel in an emission period of a previous frame and by adjusting a voltage at a gate electrode of a driving transistor of the pixel based on a voltage stored in the second capacitor in a data writing period of the current frame.