TFT-LCD Source Driver Asynchronous Odd-Even Column Charging
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Large-size TFT-LCDs face insufficient loading capacity and unfavorable display effects like artifacts and crosstalk due to significant differences in display data between adjacent rows, leading to unstable VCOM voltage and inefficient pixel charging.
Innovation Solution
A source driver with a data register, data latch, digital-to-analog converter, and output buffer, along with a data difference determination circuit, uses asynchronous loading pulses to manage gray-scale voltage output, ensuring odd and even columns are charged separately to prevent simultaneous charging and alleviate overloading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If simultaneous charging of all pixel units in a row is implemented, then display refresh speed is improved, but source driver loading capacity becomes insufficient and VCOM voltage becomes unstable
Solution Approach 1:
The pixel units in a row are segmented into odd and even columns, which are charged in separate time periods. This segmentation divides the simultaneous charging task into two sequential phases, reducing the instantaneous loading capacity requirement of the source driver and preventing VCOM voltage instability while maintaining display refresh speed.
Solution Approach 2:
The charging process is implemented as periodic action with two distinct time periods: a first time period for charging odd column pixel units and a second time period for charging even column pixel units. This periodic alternation ensures that the source driver operates within its loading capacity while achieving complete row refresh.
2Speed
If simultaneous charging of all pixel units in a row is implemented, then display refresh speed is improved, but insufficient loading capacity of source driver occurs
Solution Approach 1:
The pixel units in a row are segmented into odd and even columns, which are charged in separate time periods. This segmentation divides the simultaneous charging task into two sequential phases, reducing the instantaneous loading capacity requirement of the source driver and preventing VCOM voltage instability while maintaining display refresh speed.
Solution Approach 2:
The charging process is implemented as periodic action with two distinct time periods: a first time period for charging odd column pixel units and a second time period for charging even column pixel units. This periodic alternation ensures that the source driver operates within its loading capacity while achieving complete row refresh.
3Adaptability or versatility
If large difference in gray-scale voltages between adjacent rows occurs, then display data flexibility is improved, but artifact and crosstalk occur
Solution Approach 1:
The patent applies preliminary action by pre-charging pixel units in odd and even columns sequentially before completing the full row refresh. This preliminary staged charging approach allows the source driver to manage large gray-scale voltage differences between adjacent rows more effectively, preventing sudden voltage changes that cause artifacts and crosstalk while maintaining display data flexibility.
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
The present invention provides a source driver for use in a TFT-LCD, comprising: a data register, a data latch, a digital-to-analog converter and an output buffer. A first loading pulse is provided to the output buffer, such that the output buffer starts to output the gray-scale voltages of odd output ends to corresponding TFT sources in response to a second edge of the first loading pulse from the second level to the first level, which second edge immediately follows the first edge, and a second loading pulse is provided to the output buffer, such that such that the output buffer starts to output the gray-scale voltages of even output ends to corresponding TFT sources in response to a second edge of the second loading pulse from the second level to the first level, which second edge immediately follows the first edge. At least the second edge of the first loading pulse is not synchronous with the second edge of the second loading pulse. A driving circuit and a driving method are further provided. The source driver, the driving circuit and the driving method can alleviate adverse consequences resulting from too large difference between display data of two adjacent rows.