Touch Panel Capacitance Difference Detection
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Solution Overview
Problem
Existing electrostatic capacitance coupling type touch panels face limitations in increasing resolution due to small coupling capacitances between electrode lines, hindering the detection of multiple touch positions effectively.
Innovation Solution
The implementation of a touch panel system that selectively applies high and reference voltages to electrodes, calculates capacitance differences using integration circuits, and employs time division techniques to detect capacitance variations between electrodes, thereby canceling parasitic capacitance and enabling higher resolution with more electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of electrodes is increased to achieve higher resolution, then the coupling capacitance between electrode lines becomes smaller, making it difficult to detect touch positions accurately
Solution Approach 1:
The patent changes the voltage parameters by applying high potential voltage to one electrode and reference voltage to the other electrode, creating a voltage difference that amplifies the detectable signal. This parameter change allows the detection circuit to measure capacitance differences effectively even when the absolute capacitance values are very small, thus resolving the contradiction between high resolution and small coupling capacitance
Solution Approach 2:
The patent uses a differential measurement approach where it copies the capacitance measurement process for both electrodes and compares the results. By measuring the capacitance from each electrode to the touch object and calculating the difference, the system can detect touch position accurately without being limited by the small absolute capacitance values, effectively copying the measurement process to overcome the capacitance magnitude limitation
2Measurement precision
If parasitic capacitance is present in the electrode lines, then the detection accuracy of small inter-electrode capacitances deteriorates
Solution Approach 1:
The patent converts the harmful effect of parasitic capacitance into a beneficial differential measurement. By applying different voltages to adjacent electrodes and measuring the capacitance difference to the touch object, the common-mode parasitic capacitance effects cancel out, transforming the harmful interference into a usable signal that enhances measurement accuracy
Solution Approach 2:
The patent introduces a differential measurement mechanism as an intermediary between the electrodes and the detection circuit. This intermediary process measures the capacitance difference rather than absolute capacitance values, effectively filtering out parasitic capacitance interference and allowing accurate detection of small inter-electrode capacitances
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
This approach allows for the detection of smaller inter-electrode capacitances, canceling parasitic effects and enabling a high-resolution touch panel with a larger number of electrodes, unaffected by manufacturing or environmental fluctuations.
Implementation Method 1
the detection circuit detects a capacitance difference (A−B) between a capacitor A between a selected one of the second electrodes and the first electrode to which the high potential voltage is supplied and a capacitor B between the selected second electrode and the first electrode to which the reference voltage is supplied
Data Source
AI summary
A touch panel includes plural first electrodes extending in a first direction, plural second electrodes extending in a second direction different from the first direction, a driving circuit, a detection circuit, and a coordinate-position calculating circuit. The driving circuit sequentially selects two first electrodes out of the plural first electrodes, supplies a high potential voltage higher than a reference voltage to one of the selected two first electrodes, and supplies the reference voltage to the other, the detection circuit detects a capacitance difference (A−B) between a capacitor A between a selected one of the second electrodes and the first electrode to which the high potential voltage is supplied and a capacitor B between the selected second electrode and the first electrode to which the reference voltage is supplied, and the coordinate-position calculating circuit calculates a touch position on the touch panel touched by the observer on the basis of positions of the selected first and second electrodes and the capacitance difference (A−B).