Parallel Sensing Touch Control Device With Differential Noise Cancellation
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Solution Overview
Problem
Capacitive touch devices in mobile electronic devices face challenges in cancelling common-mode noise and reducing power consumption, leading to degraded signal-to-noise ratio and detection sensitivity due to reduced sampling points in low power modes.
Innovation Solution
A parallel sensing touch control device and method utilizing a differential sensing technique with multiplexers and a digital signal processor to concurrently connect multiple sensing electrodes, performing differential operations on detected signals to cancel common-mode noise and reduce power consumption by shortening scanning intervals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If the number of sampling points is decreased to reduce power consumption, then power consumption is reduced, but signal-to-noise ratio deteriorates
Solution Approach 1:
The sensing array is divided into multiple sensing units that can be independently controlled. Each sensing unit processes signals separately, allowing the system to reduce the number of active sensing units in low power mode while maintaining adequate sampling density in active units, thus reducing overall power consumption without severely degrading signal-to-noise ratio.
Solution Approach 2:
The system implements periodic scanning of sensing units with different duty cycles. In low power mode, not all sensing units are activated simultaneously, but rather in staggered periods. This reduces average power consumption while ensuring that when a sensing unit is active, it maintains proper sampling frequency for adequate signal-to-noise ratio.
2Measurement precision
If common-mode noise is present in the signal band, then detection accuracy is improved, but noise cancellation becomes difficult
Solution Approach 1:
A differential sensing architecture is employed where each sensing unit has two symmetric sensing electrodes that act as intermediaries. The differential measurement process uses these paired electrodes to cancel common-mode noise by subtracting the signals, while the liquid crystal display serves as an intermediary medium that can be driven in a symmetric manner to minimize introduced noise.
Solution Approach 2:
The system uses asymmetric switching sequences for the multiplexers connected to different sensing units. By introducing controlled asymmetry in the switching timing and sequences, the system can differentiate between symmetric common-mode noise from the liquid crystal display and asymmetric touch signals, improving noise cancellation effectiveness.
3Use of energy by stationary object
If the scanning interval is shortened to reduce power consumption, then power consumption is reduced, but detection sensitivity deteriorates
Solution Approach 1:
The sensing array is segmented into multiple zones with different scanning frequencies. High-priority zones maintain longer scanning intervals for high detection sensitivity, while low-priority zones use shorter scanning intervals to reduce overall power consumption. This selective segmentation allows the system to optimize the power-sensitivity tradeoff across different regions.
Solution Approach 2:
The scanning interval is made dynamic rather than fixed. The system automatically adjusts the scanning interval based on detected activity levels, touch patterns, and power conditions. When touch is detected or suspected, the scanning interval increases to improve sensitivity. When no touch is detected, the interval decreases to reduce power consumption, creating a dynamic adaptation to operational requirements.
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 effectively improves detection sensitivity in normal modes and reduces power consumption by shortening scanning intervals while maintaining signal quality, even in low power modes, through the use of multiplexers and differential signal processing.
Implementation Method 1
The parallel sensing touch control device includes a differential unit coupled to the first and second multiplexers, and configured to perform a differential operation on the first and second detected signals to output a differential signal
Data Source
AI summary
There is provided a parallel sensing touch control device including a capacitive sensor array processed by differential unit. In one detection interval, the device is concurrently conducting more than one sensing electrode of the capacitive sensor array so as to reduce a scanning interval of the capacitive sensor array. The differential unit performs a differential operation on detected signals to cancel out common mode noise.