Pixel Circuit Emission-Period Sampling for High-Resolution OLED
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Solution Overview
Problem
The diode connection type internal compensation circuit in organic electroluminescent display devices faces challenges with insufficient sampling time for threshold voltage due to high-speed driving and the addition of power lines, making high-resolution design difficult.
Innovation Solution
A pixel circuit design that includes a driving element, light-emitting element, and switch elements, with specific switch configurations and gate signals to reduce power lines and ensure sufficient threshold voltage sampling time, allowing for high-speed and high-resolution operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the diode connection type internal compensation circuit is used, then the threshold voltage loss of the driving element is reduced and compensation performance is improved, but the sampling time becomes insufficient in high-speed driving
Solution Approach 1:
The patent applies preliminary action by performing threshold voltage sampling during the emission period (when the light-emitting element is emitting light) rather than during the non-emission period. This is achieved by controlling the switch element to connect the sampling circuit to the holding node during emission, allowing threshold voltage sampling to occur in parallel with the light emission process. This resolves the time conflict by utilizing the emission period for sampling purposes, ensuring sufficient sampling time even in high-speed driving modes.
2Reliability
If power lines for setting voltages of respective nodes are added to the internal compensation circuit, then the compensation function is enhanced, but high-resolution design becomes difficult
Solution Approach 1:
The patent applies universality by making the power line that supplies the emission voltage serve multiple functions. The same power line is used both for supplying voltage during the emission period and for threshold voltage sampling during the non-emission period. This is achieved by controlling the switch element to connect the holding node to this power line during emission, allowing the power line to fulfill both voltage supply and sampling reference functions. This reduces the number of required power lines while maintaining the compensation function.
3Productivity
If the pixel circuit is driven at high speed with shortened horizontal period, then the productivity is improved, but the sampling time for threshold voltage becomes insufficient
Solution Approach 1:
The patent applies periodic action by utilizing the emission period (a periodic phase in the display operation cycle) for threshold voltage sampling. The switch element is controlled to perform sampling during the emission period when the light-emitting element is emitting light, and to connect to the power line for voltage supply during the non-emission period. This periodic switching allows the system to maintain high driving speeds while ensuring adequate sampling time by strategically placing sampling operations during the emission phase of each periodic cycle.
Data Source
AI summary
The present embodiment relates to a pixel circuit, a display panel, and a display device, and more particularly, to pixel circuit, a display panel, and a display device, which is capable of reducing the number of power lines and/or sufficiently securing the time for sampling a threshold voltage of a driving element in the pixel circuit.