Touch Pad Driving Device EMI Reduction via Channel Segmentation
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Solution Overview
Problem
Existing self-capacitance touch pads experience significant electromagnetic interference (EMI) due to the practice of providing the same touch driving signal to multiple sensing channels, which reduces parasitic capacitance but increases EMI, disrupting other circuits.
Innovation Solution
A touch pad driving device and method that includes a channel selection unit and controller to scan sensing channels, apply a touch driving signal to one selected channel, a shielding signal to adjacent channels, and a reference signal to the remaining channels based on position information, reducing the number of channels receiving the touch driving and shielding signals and thereby minimizing EMI.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the same touch driving signal is provided to multiple sensing channels to reduce parasitic capacitance, then signal variation during touch is improved, but electromagnetic interference increases and disturbs other circuits
Solution Approach 1:
The patent segments the sensing channels into different groups: one selected sensing channel receives the touch driving signal, adjacent sensing channels receive shielding signals, and remaining sensing channels receive reference signals. This segmentation reduces the number of channels simultaneously receiving touch driving signals, thereby reducing electromagnetic interference while maintaining signal variation in the selected channel.
Solution Approach 2:
Different sensing channels are assigned different signal types based on their positions and functions. The selected channel receives the touch driving signal for active sensing, adjacent channels receive shielding signals to reduce interference, and other channels receive reference signals. This local differentiation optimizes both signal quality and EMI reduction.
2Area of stationary object
If multiple sensing channels receive the touch driving signal simultaneously, then coverage area is improved, but electromagnetic interference increases
Solution Approach 1:
The controller sequentially selects different sensing channels to receive the touch driving signal at different time periods, rather than simultaneously activating all channels. This periodic activation maintains comprehensive sensing coverage over time while reducing instantaneous electromagnetic interference from multiple active channels.
Solution Approach 2:
The sensing channels are segmented into active (receiving touch driving signal), shielding (receiving shielding signal), and reference (receiving reference signal) groups. This segmentation allows comprehensive spatial coverage through multiple channels while limiting the number of simultaneously active channels to reduce EMI.
Data Source
AI summary
A touch pad driving device and a touch driving method are provided. The touch pad driving device is configured to scan a plurality of sensing channels of a touch pad, cause the selected sensing channel in the plurality of sensing channels receive a touch driving signal, cause the sensing channels adjacent to or around the selected sensing channel receive a shielding signal, and cause the remaining sensing channels receive a reference signal, so as to reduce electromagnetic interference generated by the touch pad.