Capacitive Touch Sensor Circuit With Saw-Tooth Charge Transfer
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Solution Overview
Problem
Existing capacitive touch sensor circuits are costly to manufacture and lack reliability.
Innovation Solution
A capacitive touch sensor circuit utilizing discrete components such as transistors, diodes, and passive components, generating a saw-tooth-formed charging voltage to detect capacitance changes in a capacitive sensor element, which transfers charge to an accumulation capacitor for actuation detection without requiring specialized ICs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If specialized ICs are used for capacitive touch sensor circuits, then reliability is improved, but manufacturing cost increases
Solution Approach 1:
The circuit is divided into functional blocks using discrete components: charging voltage source, charge transfer transistor, accumulation capacitor, and detection device. This segmentation allows each component to be optimized independently while maintaining overall reliability without requiring a specialized integrated circuit.
Solution Approach 2:
Standard discrete components (transistors, diodes, capacitors, resistors) are used that can serve multiple functions within the circuit. For example, the charge transfer transistor serves both as a switch controlled by the saw-tooth voltage and as a charge transfer mechanism, eliminating the need for specialized ICs while maintaining reliability.
2Ease of manufacture
If discrete components are used instead of specialized ICs, then manufacturing cost is reduced, but device complexity increases
Solution Approach 1:
Multiple functions are merged into single components to reduce overall circuit complexity. The charge transfer transistor's switching state is directly controlled by the charging voltage without requiring separate control logic. Diodes are used to combine charging and discharging functions in a simplified manner.
Solution Approach 2:
The circuit components automatically perform their functions based on the saw-tooth voltage waveform without requiring external control signals. The charge transfer transistor self-regulates charge transfer based on its switching state, and the accumulation capacitor automatically integrates charge over time, reducing the need for complex control circuitry.
3Measurement precision
If a saw-tooth-formed charging voltage is used, then charge transfer precision is improved, but circuit complexity increases
Solution Approach 1:
The saw-tooth voltage is generated periodically using simple RC timing circuits or oscillators that are standard discrete components. This periodic waveform naturally provides the rising slope for charging and falling slope for discharge, achieving precise charge transfer without requiring complex voltage control circuitry.
Solution Approach 2:
The saw-tooth voltage waveform parameters (rising slope duration, voltage difference, plateau duration, falling slope duration) are optimized to achieve precise charge transfer. The specific parameter ranges mentioned in the patent (e.g., rising slope 0.001-10ms, voltage difference 3-48V) provide the necessary precision for capacitance detection while using simple voltage generation circuits.
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 reduces manufacturing costs significantly while maintaining high reliability and sensitivity to capacitance changes, enabling detection of small capacitance variations using a few discrete components.
Implementation Method 1
a capacitive sensor element (1), wherein a capacitance of the capacitive sensor element (1) depends on the actuation state of the capacitive sensor element (1)
Implementation Method 2
a charge transfer transistor (4) being configured to transfer electrical charge from the charged capacitive sensor element (1) to the accumulation capacitor (2)
Implementation Method 3
an actuation detection device (5) being configured to measure a voltage (VA) across the accumulation capacitor (2) to detect if the capacitive sensor element (1) is actuated or not actuated
Data Source
Figure 1~2
AI summary
Capacitive touch sensor circuit (100), comprising: - a capacitive sensor element (1), wherein a capacitance of the capacitive sensor element (1) depends on the actuation state of the capacitive sensor element (1), - an accumulation capacitor (2), - a charging voltage source (3) being configured to generate a charging voltage (VC) for charging the capacitive sensor element (1), - a charge transfer transistor (4) being configured to transfer electrical charge from the charged capacitive sensor element (1) to the accumulation capacitor (2), and - an actuation detection device (5) being configured to measure a voltage (VA) across the accumulation capacitor (2) to detect if the capacitive sensor element (1) is actuated or not actuated, - wherein the charging voltage source (3) is configured to generate a saw-tooth-formed charging voltage (VC) for charging the capacitive sensor element (1).