Pixel Circuit Charging Control for Liquid Crystal Displays
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Solution Overview
Problem
Conventional liquid crystal display technologies face challenges in achieving efficient gray scale voltage control, particularly in high-resolution displays, due to RC delay and insufficient pixel electrode charging, leading to increased power consumption and complex debugging processes.
Innovation Solution
A pixel circuit and driving method that utilize a selection unit, gray scale writing unit, and reset unit to control the charging of liquid crystal capacitors based on row and column control signals, allowing for precise application and duration of gray scale voltage signals, thereby determining the gray scale level displayed, and incorporating a timing controller to manage the charging duration across multiple pixel circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If progressive scanning or interlaced scanning is used to write gray scale voltage to pixel electrodes row by row, then the liquid crystal display can be driven, but RC delay occurs and the delay becomes particularly obvious for high resolution and ultra-high resolution displays
Solution Approach 1:
The pixel circuit is segmented into multiple independent charging paths through the selection unit, which can selectively connect different gray scale voltage sources to different pixel electrodes. This segmentation allows parallel charging operations, reducing the overall RC delay by eliminating the sequential row-by-row writing bottleneck.
Solution Approach 2:
The invention introduces a new control dimension by adding the selection unit that operates independently from the traditional row-column scanning mechanism. This selection unit provides an additional pathway for voltage writing, transforming the single-dimension sequential writing into a multi-dimension parallel operation, thereby reducing RC delay effects.
2Measurement precision
If conventional 1T1C pixel structure is used with external Gamma circuit and resistor string division, then gray scale control is achieved, but power consumption increases and control cost for 8-bit voltage value becomes high
Solution Approach 1:
The invention extracts and eliminates the power-consuming external Gamma circuit and resistor string division components from the system. By integrating the gray scale voltage generation directly into the pixel circuit through the selection unit and gray scale writing unit, the design removes the need for continuous power consumption in voltage division and conversion operations.
Solution Approach 2:
The pixel circuit becomes self-sufficient in generating and selecting gray scale voltages through its integrated selection unit and gray scale writing unit. Each pixel circuit can independently select and apply the required gray scale voltage without relying on external power-consuming conversion circuits, achieving self-service operation.
3Measurement precision
If FRC pixel dithering algorithm is used in timing controller to obtain 8-bit voltage value from 6-bit voltage value, then higher gray scale precision is achieved, but more defects occur and debugging period becomes longer
Solution Approach 1:
The invention performs preliminary action by pre-preparing multiple gray scale voltage values in the selection unit before they are needed. The gray scale writing unit can directly select and apply these pre-prepared voltages to pixel electrodes, eliminating the need for runtime dithering algorithms and their associated complexity and debugging requirements.
4Measurement precision
If resolution is increased in liquid crystal display, then display quality is improved, but RC delay becomes more obvious and pixel electrode charging becomes insufficient
Solution Approach 1:
The selection unit provides dynamic control over the charging process, allowing the circuit to adaptively select optimal charging paths and voltage values based on real-time requirements. This dynamic capability ensures complete pixel electrode charging even in high-resolution displays where RC delay would normally prevent sufficient charging within the available time.
Data Source
AI summary
A pixel circuit includes a liquid crystal capacitor, a selection unit, a gray scale writing unit, and a reset unit. The selection unit is configured to determine whether to charge the liquid crystal capacitor according to a row control signal and a column control signal. The gray scale writing unit is configured to apply a gray scale voltage signal to the liquid crystal capacitor, when the selection unit determines to charge the liquid crystal capacitor, and an application duration of the gray scale voltage signal controls a gray scale level displayed by the liquid crystal capacitor. The reset unit is configured to disconnect the gray scale writing unit and the liquid crystal capacitor to stop charging the liquid crystal capacitor upon receiving the reset signal, and reset the voltage of the liquid crystal capacitor to an initial state.