Capacitive Touch Screen Self-Test Using Unique Drive Signals
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Solution Overview
Problem
Existing capacitive touch screens face operational faults due to issues in drive electronics, drive lines, read lines, or receivers, which can lead to improper detection of touch events, particularly in safety-critical applications, necessitating reliable self-testing methods.
Innovation Solution
A method and assembly for capacitive touch screens that apply unique drive signals to each line, modify their amplitudes, and analyze responses on read lines to identify faults, determining issues with drive or read lines, receivers, or drive circuits by detecting changes in signal responses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electrical characterisation is performed during final assembly and test process, then touch screen operation can be verified, but the testing process becomes complex requiring re-characterisation
Solution Approach 1:
The touch screen performs self-testing by utilizing its own drive electronics and signal processing capabilities to generate test signals and analyze responses, eliminating the need for external testing equipment and complex re-characterisation procedures
Solution Approach 2:
The drive electronics are designed to serve dual purposes: normal touch screen operation and self-testing functions, allowing the same hardware to perform both operational tasks and diagnostic verification without requiring separate dedicated testing components
2Reliability
If drive signals are modified during operation for testing, then fault detection capability is improved, but the risk of interfering with normal touch event detection increases
Solution Approach 1:
The self-testing is performed periodically during normal operation by temporarily modifying drive signals in a controlled manner, allowing the system to alternate between operational mode and testing mode without continuous interference
Solution Approach 2:
The system performs preliminary testing by analyzing the response of read lines to modified drive signals before declaring a fault, ensuring that normal touch detection is not falsely triggered by transient signal variations
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 self-testing of capacitive touch screens during operation, accurately identifying and localizing faults in drive or read lines, receivers, or drive circuits, ensuring proper touch event detection.
Implementation Method 1
One method of sensing touch on a panel or touch is based on capacitive coupling between two galvanically isolated electrodes. The capacitance between two electrodes is affected by the nature of the dielectric material between them.
Implementation Method 2
If the dielectric is modified, for instance by introducing a finger or other object touching the panel, the capacitance between the electrodes is changed, and this change in capacitance can be detected.
Data Source
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 cross-point 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.