Built-In Self-Test Circuit for Capacitive Touch Panel Fault Detection
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Solution Overview
Problem
Capacitive touch sensors are prone to manufacturing defects and wear, leading to impaired performance and defective interfaces, with existing fault detection methods being unreliable and costly due to increased system complexity and mechanical or optical scanning errors.
Innovation Solution
A Built-In Self-Test (BIST) circuit and method that uses a mutual capacitance measurement system to detect faults in touch panels by measuring self and mutual capacitance between electrodes, allowing for real-time calibration and fault identification during manufacturing or operation, reducing reliance on external circuitry and mechanical tests.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If optical scanning or mechanical test equipment is used to detect defects, then manufacturing quality control is improved, but system complexity and cost increase
Solution Approach 1:
The patent merges the sensing function and test function into a single integrated system. The same controller and sensing circuitry used for normal touch panel operation are also used to perform capacitance measurements for defect detection, eliminating the need for separate external test equipment and reducing system complexity.
Solution Approach 2:
The touch panel system performs self-diagnosis by using its own sensing circuitry to measure capacitance values and detect defects. The controller automatically compares measured capacitance against reference values and identifies defective regions without requiring external mechanical test equipment or optical scanning systems.
2Difficulty of detecting and measuring
If external circuitry and mechanical test structures are used for fault detection, then fault location capability is improved, but reliability decreases due to additional failure mechanisms
Solution Approach 1:
The patent extracts the test function from external equipment and integrates it directly into the touch panel's existing circuitry. By removing external test structures and using only the panel's native sensing elements and controller, the system eliminates additional failure mechanisms while maintaining fault detection and location capabilities.
Solution Approach 2:
The sensing circuitry is designed to serve multiple functions: normal touch operation and defect detection. The same electrodes, capacitive sensing elements, and controller used for touch input also perform capacitance measurements for quality control, reducing the need for dedicated test components and improving overall system reliability.
3Manufacturing precision
If mechanical detection methods are used, then defect identification is improved, but productivity decreases due to low throughput
Solution Approach 1:
The patent replaces mechanical detection methods with electrical capacitance measurements. Instead of using physical probes or mechanical scanning systems, the system uses electronic capacitance sensing to detect defects, enabling faster measurement speeds and higher production throughput while maintaining detection accuracy.
Solution Approach 2:
The capacitance measurement process can be performed continuously during manufacturing without requiring physical contact or mechanical movement. The electrical measurement process allows for rapid sequential testing of multiple panels, significantly increasing productivity compared to mechanical detection methods.
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
The BIST circuit effectively identifies and locates faults in capacitive touch panels, enhancing manufacturing quality control and operational reliability while reducing production costs by integrating fault detection directly into the touch panel system.
Implementation Method 1
measuring self and mutual capacitance between electrodes
Data Source
AI summary
A method, system and apparatus is described for measuring a sensor, comparing measured values of a sensor to a reference value, adjusting a calibration parameter in response to the comparing of measured values to a reference value and determining sensor integrity based on the value o the adjusted parameter.