Shielding Capacitance Control for Higher-Sensitivity Capacitive Sensing
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Solution Overview
Problem
Conventional capacitive detection devices face challenges in enhancing sensitivity and signal-to-noise ratio (SNR) due to internal parasitic capacitance limitations and noise interference, particularly in mobile terminals and laptops, where consumption current is a concern.
Innovation Solution
A capacitive detection device and method that modifies internal parasitic capacitance to apply driving voltage, incorporates a shielding area to block noise, and reduces driving voltage, utilizing a conductive body, capacitive detection area, operational amplifier, and shielding capacitance to improve sensitivity and SNR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If internal parasitic capacitance is used for capacitive detection, then device complexity is reduced, but sensitivity and signal-to-noise ratio deteriorate due to noise interference and capacitance limitations
Solution Approach 1:
The patent introduces a shielding electrode as an intermediary element between the sensing electrode and the parasitic capacitance source. This shielding electrode acts as a mediator that blocks noise interference from coupling into the sensing signal line, thereby improving sensitivity without adding complex external shielding structures. The shielding electrode is integrated into the existing capacitor structure, maintaining device simplicity while enhancing measurement precision.
Solution Approach 2:
The patent modifies the electrical parameters of the internal parasitic capacitance by applying a specific driving voltage to the shielding electrode. This voltage application changes the electrical state of the parasitic capacitance, transforming it from a noise source into a controlled component that contributes to the detection signal. By changing the voltage parameter, the system improves sensitivity while using the existing parasitic capacitance structure.
2Measurement precision
If driving voltage is applied to internal parasitic capacitance, then sensitivity improves, but consumption current increases
Solution Approach 1:
The patent applies driving voltage locally and selectively - only to the shielding electrode during specific detection phases, rather than continuously to all capacitances. This localized voltage application improves sensitivity when needed while minimizing overall power consumption. The voltage is applied only to the specific region (shielding electrode) that requires it for noise cancellation, leaving other parts of the system at lower power states.
Solution Approach 2:
The patent employs periodic voltage application to the shielding electrode, alternating between voltage application phases (for sensitivity enhancement) and relaxation phases (for current reduction). This periodic action allows the system to achieve high sensitivity during detection intervals while reducing consumption current during non-detection intervals, effectively resolving the contradiction between sensitivity and power usage.
3Measurement precision
If shielding area is added to block noise, then signal-to-noise ratio improves, but device complexity and area increase
Solution Approach 1:
The patent makes the shielding electrode multi-functional by integrating it into the existing capacitor structure where it serves both as part of the capacitive element and as a noise-shielding component. This shielding electrode is not a separate added component but rather a functional element that performs dual roles: maintaining capacitance function and providing noise shielding. This universality improves signal-to-noise ratio without proportionally increasing device area.
Solution Approach 2:
The patent implements a nested structure where the shielding electrode is positioned within or adjacent to the existing capacitor structure, effectively nesting the shielding function inside the existing device footprint. The shielding electrode is integrated into the layered capacitor architecture, allowing noise protection to be embedded within the existing area rather than requiring additional external space.
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 enhances sensitivity and reduces consumption current by effectively detecting additional capacitance and improving signal quality, making it suitable for mobile devices.
Implementation Method 1
Cprs is 'internal parasitic capacitor' formed between the detection (or Sensing) signal line and the semiconductor substrate inside the Semiconductor IC or the Sensing Signal Line and other signal lines
Implementation Method 2
detecting additional capacitance added to a capacitive detection area by supplying charge according to the application of driving voltage to multiple capacitances
Data Source
AI summary
The present invention involves driving multiple capacitors, including a shielding capacitance (Cin_sd), to minimize voltage fluctuations detected on the CDA signal line 200, thereby enhancing the resolution of the ADC. The additional capacitance (Cobj) generated between the CDA 100 and the object 20 due to the appearance of the object 20 is detected in the form of voltage. By analyzing with an ADC of improved resolution, it is possible to detect the presence of the object 20 more reliably.