Shielded Touch Pad Layout for Water Drop False-Touch Prevention
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Solution Overview
Problem
Existing touch sensor circuits struggle to distinguish between user touches and the settling of conductive foreign matter, such as water drops, due to similar capacitance changes, leading to misrecognition and malfunction.
Innovation Solution
A grounded shield region is disposed around the touch pad to form a capacitor with the touch pad, with a shield pad drive circuit applying the same signal to both terminals of the capacitor formed by conductive foreign matter, ensuring identical waveforms in touch and shield channels to differentiate between user touches and foreign matter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a typical touch sensor circuit is used to detect capacitance changes, then user touch detection is enabled, but conductive foreign matter such as water drops cannot be distinguished from user touches, causing misrecognition
Solution Approach 1:
The sensing area is divided into a touch pad region and a shield pad region. The touch pad detects capacitance changes from user touches, while the shield pad detects capacitance changes from conductive foreign matter. By segmenting the detection areas and analyzing signals from both regions, the system can distinguish between genuine touches and foreign matter interference.
Solution Approach 2:
The shield pad acts as an intermediary element that detects the presence of conductive foreign matter between the touch pad and ground. The shield pad's capacitance change serves as an indicator signal that helps differentiate foreign matter from actual user touches on the touch pad.
2Object-affected harmful factors
If the shield pad is connected to ground voltage, then electromagnetic shielding is provided, but capacitance changes from foreign matter between the touch pad and shield pad cause false touch signals
Solution Approach 1:
The system continuously monitors capacitance changes in both the touch pad and shield pad. When a capacitance change is detected in the shield pad region, this feedback information is used to adjust or invalidate corresponding touch detections in the touch pad, preventing false touch signals from being generated by foreign matter.
Solution Approach 2:
The shield pad is positioned and configured to preemptively detect the presence of conductive foreign matter before it can cause false touch signals. By establishing a monitoring zone around the touch pad and detecting foreign matter early, the system can prevent or correct false touch readings before they occur.
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
This design effectively distinguishes between user touches and conductive foreign matter, minimizing malfunctions by maintaining identical waveforms in touch and shield channels, thus preventing misrecognition.
Implementation Method 1
when conductive foreign matter settles between the touch pad and the shield pad, a capacitor is formed between the touch pad and the shield pad
Data Source
AI summary
The present invention provides a touch sensing device having a malfunction prevention function, in which a grounded shield region is further disposed around at least one touch pad, thereby minimizing influence of a water drop settling between the touch pad and the shield region on an actual user touch.