Capacitive Voltage-Divider Touch Sensing for Fast Point Detection
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Solution Overview
Problem
Existing touch screen sensing circuits, both active and passive types, face challenges in accurately determining touch points with high precision and efficiency, leading to increased production costs and prolonged response times.
Innovation Solution
A touch sensing circuit comprising an AC source, a voltage division circuit with capacitive branches on a touch sensing glass, and a processing circuit that determines touch point positions based on voltage differences between adjacent branches, utilizing capacitors and resistors to directly proportion capacitance to touch point distance, allowing for rapid detection and reduced production costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an active sensing circuit uses high precision inductance coils to accurately determine touch points, then measurement precision is improved, but device complexity and production cost increase
Solution Approach 1:
The patent replaces the complex active sensing circuit with inductance coils and successive circuits with a simplified capacitive voltage division circuit. By using capacitive sensors and voltage division resistors instead of inductance coils, the system achieves touch point detection through voltage measurements rather than complex inductance measurements, thereby reducing circuit complexity while maintaining detection accuracy
Solution Approach 2:
The patent changes the sensing parameter from inductance measurement to capacitance measurement. By using capacitive sensors that change capacitance based on touch proximity, and measuring voltage division ratios instead of inductance values, the system simplifies the measurement process and reduces the complexity of successive circuits while preserving measurement precision
2Device complexity
If a passive sensing circuit uses simple voltage accumulation to detect touch points, then device complexity is reduced, but response time increases
Solution Approach 1:
The patent maintains continuous voltage division across the capacitive branches, allowing real-time detection of capacitance changes as touch points occur. The AC signal continuously charges and discharges the capacitors, enabling immediate detection of voltage changes without waiting for charge accumulation, thus reducing reactive time while keeping the circuit simple
Solution Approach 2:
The patent uses periodic AC signals to charge and discharge the capacitive branches, creating continuous oscillating voltages that respond immediately to touch events. This periodic charging mechanism allows the circuit to rapidly detect capacitance changes through voltage fluctuations, reducing response time compared to slow charge accumulation in traditional passive circuits
3Speed
If supplemental circuits are added to decrease reactive time of passive sensing circuit, then response speed is improved, but production cost increases
Solution Approach 1:
The patent pre-charges the capacitive branches using voltage division resistors and AC signals before touch events occur. The continuous voltage division setup ensures that capacitors are always charged and ready to respond to touch events, eliminating the need for supplemental charging circuits and achieving fast response with simple circuitry
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 enables economical and responsive touch sensing by simplifying circuit elements and rapidly reflecting capacitance variations, thereby lowering production costs and increasing response speed.
Implementation Method 1
a controlling board selects one of the inductance coils and delivers alternative current to the selected inductance coil
Implementation Method 2
resonance circuit of the electronic pen stores electric energy. After the electric energy is stored in the electronic pen, the controlling board stops delivering alternative current to the selected inductance coil. Meanwhile, resonance circuit of the electronic pen transforms the electric energy to signals by free oscillation
Implementation Method 3
the voltage division circuit receives an AC signal outputted from the AC source and includes a first branch and a second branch on a touch sensing glass, wherein the first and second branches are adjacent to each other. The processing circuit is connected to the voltage division circuit for determining position of a touch point according to the voltages of the first branch and the second branch
Data Source
AI summary
A touch sensing circuit includes an alternative current (AC) source, a voltage division circuit, and a processing circuit. The voltage division circuit receives an AC signal outputted from the AC source and includes a first branch and a second branch on a touch sensing glass, wherein the first and second branches are adjacent to each other. The processing circuit is connected to the voltage division circuit for determining position of a touch point according to the voltages of the first branch and the second branch. In a preferred embodiment, the first branch comprises a first capacitor and a first voltage division resistor connected to the first capacitor, and the second branch comprises a second capacitor and a second voltage division resistor connected to the second capacitor.