Liquid Crystal Display Pixel Circuit Arbitrary Voltage Control
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Solution Overview
Problem
Digital driven liquid crystal displays are limited in applying driving voltages other than ground potential and power-supply voltage to pixels, restricting their ability to display a wide range of grayscales.
Innovation Solution
A liquid crystal display system that includes pixel circuits capable of selectively holding and applying arbitrary driving voltages between the ground potential and power-supply voltage, using a combination of transistors and capacitors to manage sub-frame data and apply suitable voltages to liquid crystals for gradation display.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If ground potential and power-supply voltage are applied to both ends of a liquid crystal cell, then the liquid crystal cell can be driven, but any driving voltage other than ground potential and power-supply voltage cannot be applied to each pixel
Solution Approach 1:
The pixel circuit is divided into multiple functional units: a first hold unit for holding initial voltage levels, a second hold unit for holding final driving voltages, and a transfer control unit for voltage transfer. This segmentation allows independent optimization of each unit's function, enabling arbitrary voltage selection while maintaining manageable circuit complexity
Solution Approach 2:
The first hold unit pre-charges or pre-discharges capacitors to specific voltage levels before the actual display operation. By performing preliminary voltage preparation in advance, the circuit can switch between different driving voltages (including arbitrary voltages between ground and power-supply) without requiring complex real-time voltage generation circuits
2Manufacturing precision
If fixed driving voltages are used for liquid crystal cells, then the circuit design is simplified, but the grayscale display capability is limited
Solution Approach 1:
The pixel circuit incorporates dynamic voltage selection capability through the transfer control unit, which can selectively connect the second hold unit to different voltage sources based on sub-frame data. This dynamic switching enables precise grayscale control by applying different voltage levels (including arbitrary intermediate voltages) while maintaining ease of operation through automated control
Solution Approach 2:
The second hold unit acts as an intermediary between the fixed power-supply voltage and the liquid crystal cell, enabling arbitrary voltage levels to be applied to the pixel. This intermediary structure allows precise voltage control for grayscale display while the actual voltage generation still relies on the fixed power-supply, balancing precision and simplicity
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
Enables the application of a wider range of driving voltages to pixels, enhancing the dynamic range and grayscale capabilities of liquid crystal displays without increasing the size of the pixel circuit, thus improving image quality and efficiency.
Implementation Method 1
a pixel unit configured to drive a liquid crystal according to a potential difference between the higher or lower driving voltage held in the second hold unit and a voltage supplied to a common electrode thereof
Data Source
AI summary
A liquid crystal display includes a pixel circuit having a first hold unit, a second hold unit, a transfer control unit and a pixel unit. The first hold unit selectively holds a higher or lower driving voltage which is arbitrarily set between a ground potential and a power-supply voltage, according to a row selection signal from a vertical scanning unit and a logical value of data from a horizontal scanning unit. The second hold unit selectively holds the higher or lower driving voltage held in the first hold unit. The transfer control unit transfers to the second hold unit, the higher or lower driving voltage held in the first hold unit according to a trigger pulse. The pixel unit drives a liquid crystal according to a potential difference between the higher or lower driving voltage held in the second hold unit and a voltage supplied to a common electrode thereof.