Pixel Circuit Initialization for Low-Frequency Screen Drag Reduction
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Solution Overview
Problem
Display devices experience screen drag and ghost phenomena due to hysteresis differences in threshold voltage shifts of adjacent pixels when driven at low frequencies, leading to reduced display quality.
Innovation Solution
A pixel structure and driving method that allows for various driving frequencies, utilizing a bias with a constant voltage to match driving current direction and bias direction, and separate initialization voltages for transistors and light emitting elements to reduce hysteresis deviation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If the display device is driven at a low frequency to improve driving efficiency and minimize power consumption, then power consumption is reduced, but hysteresis difference due to grayscale difference between adjacent pixels becomes severe, causing screen drag
Solution Approach 1:
The patent applies preliminary action by separately initializing the gate electrode and anode of the light emitting element before the low-frequency driving period. The gate electrode is initialized to a first initialization voltage and the anode is initialized to a second initialization voltage in advance, ensuring that both components start from known states when driving begins, thereby preventing hysteresis differences and screen drag during low-frequency operation
Solution Approach 2:
The patent segments the initialization process into separate steps: first initializing the gate electrode to a first initialization voltage, then initializing the anode to a second initialization voltage. This segmentation allows independent control and optimization of each initialization step, ensuring proper hysteresis compensation without causing unintended light emission, thus maintaining display quality during low-frequency driving
2Reliability
If separate initialization voltages are supplied for gate electrode and anode to reduce hysteresis deviation, then screen drag is reduced, but the complexity of the pixel structure increases
Solution Approach 1:
The patent applies universality by designing a pixel structure where the same transistor and capacitor components serve multiple functions: they are used for both the normal driving operation and for the separate initialization process. The transistor controls both data writing during driving and voltage supply during initialization, while the capacitor stores both driving voltage and initialization voltage, eliminating the need for dedicated initialization-only components and thus limiting the increase in structural complexity
Data Source
AI summary
A pixel of display device includes a light emitting element, a first transistor coupled between first power source and a second node and having a gate electrode connected to a first node N1, and the first transistor being configured to control a driving current supplied to the light emitting element in response to a voltage of the first node, a first capacitor including one electrode connected to the first node and another electrode connected to a third node, a second transistor coupled between the third node and a data line, a third transistor coupled between the first node and the second node, a fourth transistor coupled between the first node and an initialization power source, a fifth transistor coupled between a reference power source and the third node, and an eighth transistor coupled between a fourth node and an anode initialization power source.