Resistive Touch Panel Current Detection for Low-Resistance Multi-Touch
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Solution Overview
Problem
Resistive film-type touch panels face reduced sensitivity and effective resolution in detecting multi-touch due to decreasing panel resistance, making it difficult to accurately detect fluctuations in current caused by touch events.
Innovation Solution
A control circuit is designed for a touch panel with a driving circuit and current detection circuit that subtracts a predetermined current from the panel current, allowing for the removal of constant components and enhancing the detection of fluctuation components, thereby improving accuracy. This includes a current copy circuit, variable current source, I/V conversion circuit, and A/D converter, which can be integrated on a semiconductor substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If panel resistance is reduced, then power consumption is decreased, but sensitivity and effective resolution in detecting multi-touch fluctuation components deteriorate
Solution Approach 1:
The patent extracts the constant component from the panel current by subtracting a predetermined current value, isolating only the fluctuation component that contains multi-touch information. This allows the system to maintain low panel resistance while still detecting touch fluctuations accurately by focusing measurement on the extracted variable component rather than the total current.
Solution Approach 2:
Instead of measuring the complete panel current, the patent applies partial measurement by subtracting a predetermined current to capture only the necessary fluctuation portion. This partial action approach maintains sensitivity for multi-touch detection while allowing the overall panel resistance to be reduced for lower power consumption.
2Ease of manufacture
If panel resistance is reduced, then manufacturing cost is decreased, but sensitivity in detecting current fluctuations caused by touch events deteriorates
Solution Approach 1:
The patent extracts the meaningful fluctuation signal from the total panel current by subtracting a predetermined current value. This extraction method enables the use of lower resistance panels (which are cheaper to manufacture) while maintaining detection sensitivity by focusing on the extracted fluctuation component rather than being limited by the overall low current levels.
3Stability of the object's composition
If constant current component is present in panel current, then stable operation is maintained, but detection accuracy of fluctuation components is reduced
Solution Approach 1:
The patent removes the constant current component from the panel current measurement by subtracting a predetermined current value. This extraction process eliminates the stable baseline that masks fluctuation signals, allowing the system to maintain stable operation while simultaneously achieving high detection accuracy for touch-induced current variations.
Solution Approach 2:
The predetermined current subtraction acts as an intermediary processing step between the raw panel current and the final detection. This intermediate action filters out the constant component, allowing the system to benefit from both the stability of the constant current and the detection accuracy of the extracted fluctuation component.
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 solution effectively increases the accuracy of detecting fluctuation components in the panel current, enhancing the sensitivity and effective resolution of touch detection, even with reduced panel resistance.
Implementation Method 1
When detecting the X coordinate, a constant voltage (driving voltage) VDRV is applied between the pair of X electrodes 106, and a potential Vx obtained by dividing the constant voltage VDRV by resistors Rx1 and Rx2 is generated at the contact point PT
Implementation Method 2
a current detection circuit configured to generate a digital current detection value that indicates a current amount obtained by subtracting a predetermined current from a panel current flowing between the first terminal and the second terminal
Data Source
AI summary
There is provided a control circuit configured for a touch panel. The touch panel includes: a first resistive film and a second resistive film installed with a gap between the first resistive film and the second resistive film; and a first terminal and a second terminal that extend from two opposing sides of the first resistive film. The control circuit includes: a driving circuit configured to apply a driving voltage between the first terminal and the second terminal; and a current detection circuit configured to generate a digital current detection value that indicates a current amount obtained by subtracting a predetermined current from a panel current flowing between the first terminal and the second terminal.