Pixel Circuit Threshold Compensation for Afterimage-Free Displays
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Solution Overview
Problem
In existing pixel driving circuits, parasitic capacitors cause variations in the source electrode voltage of driving transistors due to different grayscale resets, leading to threshold voltage fluctuations and afterimages in display panels.
Innovation Solution
A pixel circuit design incorporating multiple control and resetting circuits, including a first resetting circuitry to write initial voltages, a data writing circuitry for data voltages, and a threshold compensation circuitry to stabilize the driving transistor's gate-to-source voltage, ensuring rapid hysteresis recovery and eliminating afterimages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a resetting phase is implemented to initialize the gate electrode voltage, then the transistor can be reset to a known state, but the parasitic capacitor causes coupled voltage changes in the source electrode that vary with different grayscale values, leading to threshold voltage fluctuations and afterimages
Solution Approach 1:
The patent applies preliminary action by resetting the source electrode voltage to a reference voltage before the data writing phase. The first resetting circuitry writes the first initial voltage into the first node (gate electrode) and the first control circuitry writes the power supply voltage into the second node (source electrode) during an initialization phase before data is written. This preliminary resetting eliminates the harmful coupled voltage changes from the parasitic capacitor that would otherwise cause afterimages during subsequent grayscale operations.
Solution Approach 2:
The patent extracts and separately controls the source electrode voltage through dedicated control circuitry. By using the first control circuitry to independently write the power supply voltage into the second node (source electrode), the patent separates the source electrode voltage control from the gate electrode control, preventing the parasitic capacitor from causing unwanted coupled voltage changes that would affect threshold voltage stability.
2Reliability
If multiple control circuits are added to stabilize gate-to-source voltage, then hysteresis recovery speed improves and afterimages are eliminated, but the pixel circuit complexity increases
Solution Approach 1:
The patent merges the resetting functions for both the gate electrode and source electrode into a unified initialization phase controlled by scanning signals. The first resetting circuitry and first control circuitry work together during the same initialization period, sharing the scanning signal control mechanism. This merging approach achieves stable gate-to-source voltage and fast hysteresis recovery while avoiding the complexity of completely separate control systems.
Solution Approach 2:
The scanning signal serves multiple functions: it controls both the first resetting circuitry to write initial voltages and the first control circuitry to write power supply voltage to the source electrode. This multi-functionality of the scanning signal reduces the need for additional dedicated control lines and circuits, achieving stable hysteresis recovery without proportionally increasing circuit complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively stabilizes the driving transistor's gate-to-source voltage, improving hysteresis recovery speed and eliminating afterimages, while maintaining normal display timing and ensuring stable pixel operation.
Implementation Method 1
there is a parasitic capacitor between a gate electrode and a source electrode of a driving transistor
Implementation Method 2
under the effect of a coupling effect of the parasitic capacitor, a voltage applied to the source electrode of the driving transistor also changes
Implementation Method 3
a threshold voltage of the driving transistor is adversely affected by the gate-to-source voltage Vgs
Data Source
AI summary
The present disclosure provides a pixel circuit, a driving method and a display device. The pixel circuit includes a light-emitting element, a driving circuitry, a first resetting circuitry, a first control circuitry and a second control circuitry. The first resetting circuitry writes a first initial voltage into a first node under the control of a first scanning signal. The first control circuitry controls a power supply voltage end to be electrically coupled to a second node under the control of a second light-emission control signal. The second control circuitry controls a third node to be electrically coupled a first electrode of the light-emitting element under the control of a first light-emission control signal. The driving circuitry controls the second node to be electrically coupled to the third node under the control of a potential at the first node.