LCD Pixel Circuit With Auxiliary Electrode for Low-Refresh Flicker
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Solution Overview
Problem
Liquid crystal display apparatuses driven at low refresh rates experience increased charge leakage, leading to voltage decreases and flicker issues due to longer image refresh intervals.
Innovation Solution
The liquid crystal display apparatus incorporates a TFT substrate with a pixel structure that includes a pixel electrode, a common electrode, an auxiliary electrode, and three TFTs connected to gate bus lines, allowing for interlaced driving and charge compensation between the capacitors to maintain voltage and reduce flicker.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the refresh rate is reduced to lower power consumption, then power consumption decreases, but charge leakage increases causing voltage drops and flicker
Solution Approach 1:
The gate bus lines are divided into two separate sets (first gate bus lines and second gate bus lines) that are driven alternately. This segmentation allows the pixel circuit to maintain voltage stability during interlaced scanning by charging the liquid crystal capacitor in one field and compensating for leakage in the next field, thereby reducing flicker at low refresh rates
Solution Approach 2:
The liquid crystal capacitor is pre-charged during the first field period before the image is fully refreshed. This preliminary charging action ensures that sufficient voltage is stored to maintain display stability during the extended refresh interval, preventing voltage drops and flicker that would otherwise occur at low refresh rates
2Duration of action of moving object
If the refresh rate is reduced to extend image refresh interval, then power consumption decreases, but charge leakage from pixel increases causing voltage applied to liquid crystal to decrease
Solution Approach 1:
The display system uses interlaced scanning with periodic action, where odd and even fields are displayed alternately. During odd fields, one set of gate bus lines is activated to charge the liquid crystal capacitor, and during even fields, the other set is activated to compensate for charge leakage. This periodic alternation maintains voltage stability throughout the extended refresh interval
Solution Approach 2:
The system recovers from charge leakage by applying compensatory voltage during alternating fields. When charge leakage causes voltage drop during one field, the subsequent field applies a compensatory signal through the alternate gate bus lines to recover the voltage level, effectively discarding the leaked charge's negative effect and recovering display quality
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
This configuration effectively compensates for charge leakage by transferring charge from the auxiliary electrode to the pixel electrode, reducing voltage drops and minimizing flicker even at low refresh rates, thereby enhancing display stability and power efficiency.
Implementation Method 1
the voltage applied to the liquid crystal may decrease and, and thus, the transmittance of the pixel may vary
Data Source
AI summary
A liquid crystal display apparatus includes a TFT substrate including first and second gate bus lines, source bus lines, and pixels and a liquid crystal layer. The pixel includes a pixel electrode, a common electrode, an auxiliary electrode, and first to third TFTs. The gates of the first and second TFTs are connected to one of the first and second gate bus lines, and the drains are connected to the pixel electrode and the auxiliary electrode, respectively. The gate of the third TFT is connected to the other of the first and second gate bus lines, and the source and drain of the third TFT are connected to the pixel electrode and the auxiliary electrode, respectively. Gate signals are applied to the first and second gate bus lines so that the TFTs connected to the first and second gate bus lines are turned on at different points in time.