Liquid Crystal Display Pixel Static Memory Polarity Control
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Solution Overview
Problem
Liquid crystal display devices with pixel memory face issues of high power consumption due to large driving circuit sizes, voltage inversion requirements for AC operation, and potential display time lag from abrupt power changes, leading to increased frame size and decreased product value, as well as contrast and flicker issues.
Innovation Solution
A liquid crystal display device with a static memory in each pixel, incorporating a switch element, polarity control circuit, and driving voltage generator to control bit signals and alternate liquid crystal voltages, reducing power consumption and improving display quality by eliminating the need for simultaneous voltage inversion and allowing efficient discharge of pixel signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If voltages VLCa and VLCb are periodically inverted through driving circuits, then AC operation of liquid crystal layer is achieved, but power consumption of driver circuits increases and circuit size becomes large
Solution Approach 1:
The invention divides the voltage inversion function into two parts: (1) data signal polarity inversion performed by the static memory in each pixel, and (2) common voltage polarity inversion performed by a simple switching circuit. This segmentation allows each part to use a simpler, smaller circuit rather than requiring large driving circuits to handle the full inversion burden.
Solution Approach 2:
The static memory in each pixel automatically performs data signal polarity inversion as part of its normal operation. The pixel structure itself provides the inversion function through its switching elements, eliminating the need for external driving circuits to perform this function, thereby reducing overall circuit complexity and power consumption.
2Reliability
If voltages VLCa and VLCb are inverted simultaneously across all pixels, then proper AC operation is maintained, but driving circuits require high driving ability resulting in increased power consumption
Solution Approach 1:
The invention segments the inversion timing control so that data signals and common voltage can be inverted independently. The common voltage inversion is controlled by a simple switching circuit that can be designed with adequate driving ability, while data signal inversion is distributed across individual pixel static memories, reducing the burden on central driving circuits.
3Ease of manufacture
If N channel transistors are used to supply voltages VLCa and VLCb, then circuit implementation is simplified, but voltage shift occurs causing decreased contrast or flicker
Solution Approach 1:
The invention introduces a bootstrap capacitor as an intermediary element that stores the high-level voltage and releases it to compensate for the threshold voltage drop in N channel transistors. This intermediary mechanism ensures that the full high-level voltage is delivered to the liquid crystal capacitance without the voltage shift that would otherwise occur, maintaining contrast and eliminating flicker while keeping the transistor implementation simple.
4Stability of the object's composition
If pixel signals are held during abrupt power changes, then display continuity is maintained, but display time lag occurs reducing product value
Solution Approach 1:
The invention makes the pixel signal holding behavior dynamic rather than static. A switching element controlled by a control signal dynamically adjusts the pixel electrode connection: during normal operation, the pixel signal is held to maintain display continuity; during abrupt power changes, the switching element changes state to discharge the pixel signal, eliminating display time lag. This dynamic adaptability resolves the contradiction between continuity and responsiveness.
Data Source
AI summary
A liquid crystal display device includes a pair of substrates, a plurality of pixels arranged in a matrix and a static memory formed on the substrates. A bit signal corresponding to an image data is written and held in a static memory in the pixel. The polarity of the input bit signal is controlled. A liquid crystal voltage supplied to a liquid crystal layer arranged between the pair of substrates is generated by the bit signal. The polarity of the bit signal is controlled to alternate the liquid crystal voltage, and a transmittance of the liquid crystal layer is changed by supplying the alternated liquid crystal voltage.