Liquid Crystal Driver Staggering Drive Signals to Reduce Peak Currents
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Solution Overview
Problem
Conventional liquid crystal display drivers experience peak currents and electromagnetic interference (EMI) due to simultaneous driving of source lines, leading to image quality deterioration and increased power supply capacity requirements, especially in large panels and LTPS liquid crystal panels.
Innovation Solution
Divide drive signals for pixels of the same color into groups and stagger their output timings, extending the horizontal period to prevent current concentration and reduce EMI, while maintaining effective voltage uniformity across pixel electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If drive signals are supplied at the same timing from all output terminals, then the liquid crystal panel can be driven efficiently, but currents concentrate and cause spike-shaped noise and power voltage drops
Solution Approach 1:
The patent divides the source lines into multiple groups (e.g., odd-numbered and even-numbered groups) and supplies drive signals to each group at different timings. This segmentation of the driving process prevents current concentration while maintaining overall display efficiency.
Solution Approach 2:
The patent implements periodic staggering of drive signal output timings between different source line groups. By alternating the driving timing in a periodic manner, the system prevents simultaneous current peaks while ensuring all pixels receive their required drive signals within each frame period.
2Ease of operation
If source lines are driven at the same time, then the display operation is simplified, but large currents flow momentarily causing EMI
Solution Approach 1:
The patent segments source lines into multiple groups with different driving timings, reducing EMI while maintaining operational simplicity through automated control. The control device automatically manages the staggered timing without requiring complex manual intervention.
Solution Approach 2:
The control device automatically generates and manages the staggered drive signal timings internally, eliminating the need for external complex timing control. The system self-regulates the driving sequence to prevent EMI while maintaining simplicity of use.
3Area of stationary object
If the number of external terminals is increased to accommodate larger panels, then the panel size can be increased, but the chip area and package volume increase
Solution Approach 1:
The patent employs a single output terminal that sequentially supplies drive signals to multiple source line groups at different timings. This multi-functional use of one terminal replaces the need for multiple simultaneous terminals, reducing chip area and package volume while supporting larger panel sizes.
Data Source
AI summary
A display control/drive device (a liquid crystal controller driver and a semiconductor integrated circuit for driving liquid crystals) which can serve to reduce peak currents and thereby restrain the occurrence of EMI is to be provided. In a liquid crystal display control/drive device in which image signals to be applied to signal lines of a color liquid crystal panel are generated in response to display image data that are received, image signals for pixels of the same color are divided into a plurality of groups. And during a period in which the substantial frame frequency can be reduced, the period of a line clock matching one horizontal period is extended to slightly stagger the output timing of image signals from one to another of the groups and the sequence of outputs from the different groups is periodically varied.