Hover Detection Sensitivity via Frequency-Adjusted Drive Signals
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Solution Overview
Problem
Conventional capacitive touch panels face challenges in accurately detecting the proximity (hover) of an object due to low sensitivity, particularly at different locations on the screen, caused by variations in drive signal attenuation and parasitic capacitance, leading to inconsistent hover detection sensitivity.
Innovation Solution
A proximity detection device with a capacitive touch panel that includes sensor lines on the X and Y axes, a planar GND layer, and a connection portion, where the detection unit applies a drive signal with a frequency adjusted according to the sensor line's position, reducing apparent capacitance and improving sensing accuracy by minimizing parasitic capacitance effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a TP-GND layer is arranged parallel to the sensor pattern to detect hover using self-capacitance method, then hover detection capability is enabled, but detection sensitivity becomes insufficient due to large parasitic capacitance
Solution Approach 1:
The patent changes the frequency parameter of the drive signal applied to the TP-GND layer. By applying a drive signal at a different frequency than the sensor line, the patent reduces the apparent parasitic capacitance effect and improves hover detection sensitivity. This parameter change allows the system to maintain hover detection capability while significantly improving measurement precision.
2Measurement precision
If the same frequency drive signal is applied to both sensor line and TP-GND layer, then parasitic capacitance effect is minimized, but sensitivity differences occur at different screen locations due to signal attenuation
Solution Approach 1:
The patent applies different frequency drive signals to different regions of the TP-GND layer corresponding to different sensor line locations. By making the drive signal frequency dependent on the local position on the screen, the patent compensates for signal attenuation variations and ensures consistent hover detection sensitivity across the entire display area.
3Adaptability or versatility
If capacitance change of several 10 fF is detected against baseline capacitance of several 100 pF, then hover detection is achieved, but detection accuracy is insufficient due to 1/10,000 ratio requirement
Solution Approach 1:
The patent changes the frequency parameter of the drive signal to reduce the apparent parasitic capacitance. By operating at an optimized frequency, the system can detect the small capacitance change (several 10 fF) against the larger baseline capacitance (several 100 pF) with improved accuracy, making the measurement feasible with existing technology.
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 adjusted frequency of the drive signal enhances the accuracy of hover detection by reducing sensitivity differences across the screen, ensuring consistent detection performance regardless of the object's location.
Implementation Method 1
detects the proximity (hover) of an object using a capacitive touch panel... a change in capacitance Cp between each sensor pattern (Sxi, Syj) and the TP-GND layer is detected
Implementation Method 2
describes a technique for suppressing a decrease in detection sensitivity due to the influence of a parasitic capacitor
Data Source
AI summary
A proximity detection device includes a detection controller and a touch panel. The detection controller includes a drive unit that drives a sensor line on an X side or a Y side, a measurement unit that measures capacitance Cm, Cpx, and Cpy formed by the sensor line on the X side or the Y side, and a detection unit that performs touch detection or hover detection based on the capacitance Cm, Cpx, and Cpy measured by the measurement unit. When detecting a hover, the drive unit changes a frequency of the drive signal that drives the sensor line on the X side or the Y side and this improves a hover detection sensitivity.