Alternating Polarity Pixel Driver Circuit for OLED Grayscale Stability
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Solution Overview
Problem
Conventional pixel driver circuits in OLED display devices face challenges in maintaining consistent grayscale brightness over time due to changes in the characteristics of driving transistors, leading to uneven grayscale and brightness issues.
Innovation Solution
A pixel driver circuit with two identical pixel driving units, each comprising a driving transistor and a driving control module, where the gate electrodes of the transistors alternate in polarity between frames to mitigate the effects of long-term changes in transistor characteristics, using a data voltage with opposite polarities on separate data lines to control the potential at the gate electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single pixel driver circuit with a driving transistor is used to control OLED brightness by changing gate voltage, then the device structure is simple and easy to manufacture, but the grayscale brightness changes and becomes uneven after long-term operation due to DC bias accumulation
Solution Approach 1:
The patent divides a single pixel driver circuit into two separate pixel driver circuits. Each circuit includes its own driving transistor and control module. By segmenting the driver circuit, the patent enables alternating operation modes where one circuit operates while the other is off, preventing DC bias accumulation in any single transistor and maintaining grayscale consistency over time.
Solution Approach 2:
The patent implements periodic action by alternating the operation of the two pixel driver circuits. During even frames, the first circuit operates with its driving transistor in the on-state; during odd frames, the second circuit operates. This periodic switching prevents continuous DC bias accumulation, maintaining transistor characteristics and grayscale brightness consistency throughout operation.
2Ease of operation
If the driving transistor remains in on-state for long periods to control brightness, then the brightness control is straightforward, but the threshold voltage and mobility change due to DC bias, causing grayscale unevenness
Solution Approach 1:
The patent applies periodic action by switching between two pixel driver circuits on alternating frames. Each driving transistor remains in the on-state for only half the time (even frames or odd frames), preventing continuous DC bias accumulation. This periodic operation maintains transistor threshold voltage and mobility stability, ensuring grayscale uniformity while preserving simple brightness control through gate voltage modulation.
3Reliability
If two pixel driver circuits with alternating polarity are used, then the grayscale brightness consistency is improved by preventing DC bias accumulation, but the device complexity increases
Solution Approach 1:
The patent segments the pixel driver circuit into two identical or similar sub-circuits, each handling half the frames. This segmentation approach maintains grayscale consistency by preventing DC bias accumulation while keeping each individual circuit relatively simple. The modular design allows for systematic implementation that balances reliability improvement with acceptable device complexity.
Solution Approach 2:
The patent changes the operational parameters by implementing alternating polarity operation. During even frames, the first driving transistor has a positive gate voltage; during odd frames, the second driving transistor operates with opposite polarity. This parameter change prevents continuous DC bias in the same direction, maintaining transistor characteristics and grayscale consistency while managing device complexity through parameter alternation rather than structural complexity.
Data Source
AI summary
The present disclosure provides a pixel driver circuit, a pixel circuit, a display panel and a display device. The pixel driver circuit includes two pixel driving units having an identical structure. Each pixel driving unit includes a driving transistor and a driving control module. A gate electrode of the driving transistor is connected to the driving control module, a first electrode thereof receives a first power voltage, and a second electrode thereof is connected to the driving control module and a light-emitting element. The driving control module is connected to a data line, a gate line, and the gate electrode and the second electrode of the driving transistor, and controls a potential at the gate electrode of the driving transistor in accordance with a data voltage applied to the data line under control of a gate driving signal from the gate line, so as to turn on/off the driving transistor.