Touch Sensing Method Eliminates Shielding Layer Using Synchronized Control Signals
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Solution Overview
Problem
Conventional capacitive touch screens require a costly shielding layer to isolate panel control signals from sensing signals, leading to noise interference and incorrect position signals due to the common voltage signal Vcom.
Innovation Solution
A touch sensing method that eliminates the need for a shielding layer by using an in-phase sensing control signal with the common voltage signal Vcom, allowing the sensing circuit to determine sensing periods and detect signals within these periods to generate accurate position signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a shielding layer is added to isolate panel control signals from sensing signals, then noise interference is reduced, but manufacturing cost and device complexity increase
Solution Approach 1:
The patent extracts and removes the shielding layer from the touch panel structure. Instead of using a physical shielding layer, the invention uses signal processing techniques to eliminate noise interference, thereby simplifying the device structure while maintaining signal accuracy.
Solution Approach 2:
The patent introduces a sensing control signal as an intermediary to coordinate between the display controller and sensing circuit. This mediator signal enables synchronized operation and noise cancellation without requiring physical shielding, resolving the contradiction between signal isolation and structural simplicity.
2Measurement precision
If a shielding layer is used to isolate signals, then position signal accuracy is improved, but manufacturing cost increases
Solution Approach 1:
The patent replaces the expensive shielding layer with a software-based solution implemented through control signals. The sensing control signal acts as a virtual, costless barrier that achieves noise isolation through temporal coordination rather than physical materials, dramatically reducing manufacturing costs while maintaining precision.
Solution Approach 2:
The patent substitutes the mechanical/physical shielding layer with an electrical/software-based solution. By using the sensing control signal to coordinate sensing operations with display updates, the system achieves noise cancellation through signal processing rather than physical isolation, eliminating the need for additional manufactured components.
3Speed
If the sensing circuit operates continuously, then position detection responsiveness is improved, but noise interference from panel control signals increases
Solution Approach 1:
The patent implements periodic sensing operations synchronized with the display refresh cycle through the sensing control signal. The sensing circuit operates in periodic intervals coordinated with vertical blanking intervals, achieving both fast responsiveness and noise avoidance by timing sensing operations when panel control signals are stable.
Solution Approach 2:
The patent uses the sensing control signal to preliminarily coordinate sensing operations before actual touch detection occurs. By pre-synchronizing the sensing circuit with the display controller through control signals, the system prepares the sensing circuit to detect touches at optimal moments when noise interference is minimized, achieving both speed and accuracy.
Data Source
AI summary
A touch screen includes an LCD panel; a display controller for processing a video signal to generate a panel control signal and a sensing control signal, with the panel control signal controlling the LCD panel so that the LCD panel displays images according to the panel control signal; a touch panel, for generating the sensing signal in response to a touch; and a sensing circuit, coupled to the touch panel and the display controller, for receiving the sensing signal and the sensing control signal to generate a position signal with reference to the sensing control signal.