Touch Detection Circuit Using Dual Currents to Cancel Noise Baseline
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Solution Overview
Problem
Capacitive touch circuits used in outdoor environments or noisy conditions suffer from significant errors due to environmental parameter fluctuations and noise interference, affecting detection accuracy.
Innovation Solution
A touch detection circuit that uses two different currents for charging and discharging a detection capacitor, canceling baseline counts and avoiding noise frequencies by identifying touch events based on variations in the second charging and discharging intervals, while considering the first intervals as baseline times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single charging current is used in conventional capacitive touch circuits, then the circuit structure is simple, but the detection accuracy is degraded due to environmental parameter fluctuations and noise interference
Solution Approach 1:
The charging process is segmented into two distinct phases: a first charging interval using a first charging current, and a second charging interval using a second charging current. This segmentation allows the system to capture different baseline characteristics that can be processed to eliminate environmental interference and noise, thereby improving detection accuracy without requiring complex additional hardware
Solution Approach 2:
The patent changes the charging current parameter between the two charging intervals. By using different charging currents (first charging current and second charging current) and processing the resulting time intervals through subtraction, the system can eliminate the effects of environmental parameter fluctuations and noise, improving measurement precision
2Reliability
If conventional single-current charging is used, then the circuit operation is simple, but the detection reliability is poor in noisy environments due to baseline shifts
Solution Approach 1:
The first charging interval and first discharging interval are performed as preliminary actions to establish baseline time measurements. These baseline measurements are then subtracted from the second charging and discharging intervals to eliminate baseline shifts caused by noise and environmental factors, improving detection reliability
Solution Approach 2:
The system uses feedback by measuring the time intervals during charging and discharging, processing these measurements through subtraction to eliminate baseline shifts, and using the resulting corrected intervals for touch detection. This feedback mechanism continuously compensates for environmental interference and noise
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 approach enhances detection accuracy by mitigating environmental changes and noise interference, improving the reliability of touch detection in challenging conditions.
Implementation Method 1
a detection capacitor (20), a charging circuit (21c), a discharging circuit (21d)
Data Source
AI summary
There is provided a touch detection circuit including a charging circuit, a discharging circuit, a counter and a processor. The charging circuit charges a detection capacitor within a charging interval using different currents. The discharging circuit discharges the detection capacitor within a discharging interval using different currents. The counter counts the charging interval and the discharging interval. The processor subtracts a baseline time from a counted charging time and a counted discharging time to cancel the noise interference.