Capacitive Touch Screen Driving Method for Rapid Scan
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Solution Overview
Problem
Capacitive touch screens face reduced frame rates and scan speeds due to increased resistances in large-sized devices and the need for rapid simultaneous display driving and touch detection, which existing methods fail to address effectively.
Innovation Solution
Simultaneously sending excitation signals through multiple channels with different frequencies on the driving side and processing these signals on the receiving side to achieve rapid scan and increased frame rates, including converting and amplifying charge signals into voltage signals, performing signal demodulation, and analog-to-digital conversion for accurate detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the number of TX channels is increased for large capacitive touch screens, then the coverage area increases, but the TX scan frequency decreases due to increased line resistance, resulting in reduced frame rate
Solution Approach 1:
The patent divides the touch screen detection into multiple sub-frames, with each sub-frame dedicated to detecting a specific group of TX channels. This segmentation allows the system to handle a large number of channels without requiring all to be scanned simultaneously, thereby maintaining high frame rates while supporting large screen areas.
Solution Approach 2:
The patent implements dynamic channel grouping where TX channels are divided into different groups that are activated in different sub-frames. The system dynamically selects which channels to detect in each sub-frame based on the detection requirements, allowing flexible adaptation to different screen sizes and maintaining optimal scan frequencies.
2Reliability
If display driving and touch detection are performed at different time slots to reduce noise, then the interference is reduced, but the scan speed must be increased to meet the timing requirements
Solution Approach 1:
The patent segments the detection process into multiple sub-frames, where each sub-frame is dedicated to detecting a specific group of channels. This time-division multiplexing approach allows display driving and touch detection to occur at different time slots without interfering with each other, while maintaining sufficient scan speed through parallel processing within each sub-frame.
Solution Approach 2:
The patent ensures continuous detection by overlapping the detection periods of different channel groups. While one group of channels is being detected in a sub-frame, the system prepares for the next group, ensuring that detection is continuous and no touch events are missed, thereby maintaining both reliability and speed.
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
This approach enhances the frame rate and meets the rapidity requirement for performing display driving and touch detection at different time slots, overcoming the limitations of increased resistances and channel numbers in large capacitive touch screens.
Implementation Method 1
Mutual capacitance occurs between the layers of TXs and RXs of the ITO overlay. For example, a coupling capacitance CP2,2 occurs at the intersection of TX<2> and RX<2>, forming a touch detection point 11.
Data Source
AI summary
A method of driving and detection for a capacitive touch screen and a device thereof are provided. The method includes: sending, from a driving side, excitation signals through a plurality of channels simultaneously during the same driving and detection time period; receiving, by each of receiving channels at a receiving side, a charge signal generated from the excitation signals through coupling capacitances at corresponding touch detection points, and performing detection, which includes: converting and amplifying the charge signal into a voltage signal, and performing signal demodulation and analog-to-digital conversion on the voltage signal; and storing digital signals obtained from the analog-to-digital conversion, and analyzing the digital signals by a controller to obtain a detection result. This can achieve rapid scan, increase frame rate in detection, and meet the rapidity requirement for performing display driving and touch detection at different time slots.