Capacitive Sense Matrix Readout Circuit Compensation
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Solution Overview
Problem
Capacitive touch panels face challenges in accurately detecting touch and proximity due to variations in capacitance across the sense matrix, leading to inconsistent performance and reduced sensitivity.
Innovation Solution
Storing capacitance data representing the expected capacitance values across the capacitive sense matrix and configuring the readout circuit accordingly, using a differential amplifier and variable capacitors to compensate for these variations, allowing for improved touch detection and increased sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a capacitive sense matrix is used for touch detection, then the touch panel can detect touch and proximity, but variations in capacitance across the matrix lead to inconsistent performance and reduced sensitivity
Solution Approach 1:
The patent applies local quality by measuring and compensating for capacitance variations at different locations across the sense matrix. Each intersection or region is characterized by its specific capacitance properties, and individual compensation is applied to each location rather than using a uniform approach, thereby improving both measurement precision and detection consistency across the entire panel
Solution Approach 2:
The patent implements feedback by using measured capacitance values from the sense matrix to generate compensation data, which is then fed back into the readout circuit to adjust subsequent measurements. This closed-loop approach continuously refines the accuracy of touch detection by adapting to the actual capacitance distribution of the matrix
2Measurement precision
If capacitance variations are not compensated, then the readout circuit remains simple, but touch detection accuracy and sensitivity are reduced
Solution Approach 1:
The patent applies preliminary action by performing capacitance measurements and generating compensation data before actual touch detection operations. The readout circuit is pre-configured with compensation values derived from characterizing the capacitance distribution across the sense matrix, so that when touch detection occurs, the compensation is already in place and does not add real-time complexity
Solution Approach 2:
The patent uses copying by creating a digital model or representation of the capacitance distribution pattern and using this copy to guide the compensation process. Instead of physically modifying each capacitor, the system creates a virtual replica of the capacitance variations and applies compensation based on this model, reducing physical complexity while maintaining accuracy
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
Enhances the accuracy and sensitivity of touch detection by compensating for capacitance variations, enabling reliable detection of objects at various locations on the touch panel, including proximity detection before contact.
Implementation Method 1
Capacitive touch panels include a capacitive sense matrix including conductive rows and columns. In operation, the capacitance between each row and column of the matrix may be detected.
Implementation Method 2
a differential amplifier having an input and an output, wherein said input is coupled to the sense node
Implementation Method 3
said second capacitor comprises a variable capacitor having a variable capacitance value
Data Source
AI summary
A readout device for a capacitive sense matrix includes a computer readable storage medium configured to store capacitance data. The capacitance data represents capacitance values of the capacitive sense matrix. The readout device also includes a readout circuit configured to receive a signal from the capacitive sense matrix, the readout circuit being configured based upon the capacitance data. Also described are a readout method and a method of compensating for variations in capacitance.