Touch Input Circuit With Reference Line for False Press Rejection
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Solution Overview
Problem
Existing electronic devices with touch screens face challenges in accurately distinguishing between valid user inputs and invalid inputs, particularly due to variations in capacitance caused by external factors like the device being pressed rather than a user's touch.
Innovation Solution
An electronic device with a touch unit, signal generating unit, and signal determining unit, utilizing a resistor-capacitor circuit where signals are transmitted through parallel signal lines to measure voltage differences and determine valid user inputs by comparing pulse widths, with capacitors on a flexible printed circuit board to differentiate between touch and non-touch inputs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a touch screen is used to detect user inputs, then user interaction capability is improved, but false detection from external pressure increases
Solution Approach 1:
The signal detection function is segmented into multiple independent signal lines (first signal line connected to touch display, second signal line as reference). Each line measures capacitance changes independently, allowing the system to compare and differentiate between genuine touch inputs and external pressure effects on specific segments of the display.
Solution Approach 2:
A reference signal line (second signal line) is introduced as an intermediary element that does not connect to the touch display but runs parallel to the first signal line. This reference line serves as a mediator to measure environmental interference and external pressure effects, enabling the system to distinguish these from actual user touches through comparison.
2Measurement precision
If capacitance-based touch detection is used, then touch sensitivity is improved, but susceptibility to external interference increases
Solution Approach 1:
The system implements feedback by continuously monitoring the reference signal line and using its measurements to adjust or filter the interpretation of signals from the touch display line. When external pressure affects the reference line, this information feeds back to the determination unit, which then adjusts its assessment of touch inputs to account for the environmental conditions.
Solution Approach 2:
The reference signal line acts as an intermediary that captures environmental interference (temperature changes, external pressure, electromagnetic noise) without being directly affected by user touches. This intermediary measurement allows the system to subtract or filter out these harmful factors from the final touch detection result.
3Measurement precision
If parallel signal lines with resistors and capacitors are added, then input detection accuracy is improved, but device complexity increases
Solution Approach 1:
The reference signal line performs multiple functions: it serves as a capacitance measurement path, an environmental interference sensor, and a reference for differential comparison. By making this single circuit element multi-functional, the system achieves improved accuracy without adding proportionally more complexity, as one component accomplishes what would otherwise require multiple separate systems.
Solution Approach 2:
The first and second signal lines are designed with homogeneous structure (both contain resistors and capacitors, both run parallel through the device), which simplifies the overall circuit design and analysis. This homogeneity allows the system to use the same measurement and comparison methodology for both lines, reducing the complexity of control logic and signal processing despite the added hardware.
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
Effectively differentiates between valid and invalid user inputs by analyzing signal changes, reducing false positives from external pressure and enhancing input detection accuracy.
Implementation Method 1
a signal generating unit (signal generator) configured to generate a signal and to transmit the signal to a first signal line and a second signal line
Implementation Method 2
a signal measuring unit (signal measuring device) configured to measure at least a part of modified signal based on the transmitted signal
Implementation Method 3
The measured signal may represent a difference between a voltage value of the node on the first signal line and a voltage value of the node on the second signal line
Implementation Method 4
The modified signal may be the signal modified based on charging and discharging operations
Data Source
AI summary
An apparatus and method for determining a valid user input in an electronic device is provided. The electronic device generally includes a touch unit included in a touch input circuit, wherein the touch unit corresponds to a touch area, a signal generator configured to transmit a signal to a first signal line and a second signal line by generating the signal, a signal measuring device configured to measure a part of a modified signal based on the transmitted signal, and a signal determiner configured to determine whether a user input is provided to the touch area based on the measured signal. The first signal line connects the signal generator and the touch unit, and the second signal line extends from the signal generator and is parallel with the first signal line.