Capacitive Touch Screen Self-Test for Drive and Read Line Faults
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Solution Overview
Problem
Existing touch screens face challenges in reliably detecting faults in drive electronics, read lines, or receivers, which can lead to improper detection of touch events, particularly in safety-critical applications, and existing self-testing methods are complex or inadequate.
Innovation Solution
A self-test method for touch screens that involves modifying the amplitude of drive signals and analyzing frequency content at receivers to identify faults in drive lines, read lines, or receivers by comparing expected and actual signal responses, allowing for continuous fault detection during normal operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complex re-characterisation methods are used to test the touch screen, then fault detection capability is improved, but device complexity and testing time increase
Solution Approach 1:
The touch screen system performs self-diagnosis by monitoring its own drive signals and receiver responses. The control electronics generates test signals through the drive lines and analyzes the corresponding responses from receivers, enabling the system to detect faults in its own components without external testing equipment or complex re-characterisation procedures.
Solution Approach 2:
The system continuously monitors the operational status of drive lines and receivers during normal operation by comparing actual signal responses against expected responses. This preliminary detection allows faults to be identified before they cause complete system failure, maintaining reliability without requiring complex post-manufacturing testing.
2Reliability
If continuous fault detection is implemented during normal operation, then reliability is improved, but use of energy and processing resources increase
Solution Approach 1:
The fault detection function is merged with the normal operational function of the touch screen. The same drive lines and receivers used for touch sensing are utilized for fault detection, eliminating the need for separate testing hardware and reducing overall energy consumption. The control electronics performs dual functions: normal touch signal processing and fault detection through response analysis.
3Reliability
If fault detection methods are added to ensure safety in safety-critical applications, then reliability is improved, but device complexity increases
Solution Approach 1:
The system implements feedback monitoring where the control electronics receives responses from receivers and compares them against expected responses. This feedback mechanism provides continuous information about the operational status of drive lines and receivers, enabling automatic fault detection and ensuring safety in critical applications without requiring complex additional hardware.
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
Enables reliable and efficient detection of faults in touch screens, ensuring accurate touch event detection even during normal operation, thereby maintaining functionality and safety in safety-critical applications.
Implementation Method 1
capacitive coupling between two galvanically isolated electrodes
Implementation Method 2
The capacitance between two electrodes is affected by the nature of the dielectric material between them. If the dielectric is modified, for instance by introducing a finger or other object touching the panel, the capacitance between the electrodes is changed
Data Source
Figure 1~2
Figure 3a~3c
Figure 4a~4c
AI summary
A touch screen assembly and method of testing a capacitive touch screen are disclosed, during operation thereof in which a respectively unique drive signal is applied to each of a first plurality of lines, and each of a second plurality of lines is responsive thereto, wherein a change in a response on a one of the second plurality of lines to a one of the unique drives signals is indicative of a touch event at a crosspoint of the respective ones, the method comprising: modifying an amplitude of the respective unique drive signal applied to each of the first plurality of lines; and in the event of identifying a response to each modified amplitude, on each of the second plurality of read lines, determining that the touch screen does not have a fault, and otherwise determining that the touch screen has a fault.