Touch Detection Chip With Baseline-Canceling Dual-Current Sensing
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Solution Overview
Problem
Capacitive touch circuits used in outdoor environments face significant challenges due to environmental parameter fluctuations and noise interference, leading to degraded detection accuracy.
Innovation Solution
A touch detection circuit that charges and discharges a detection capacitor using two different currents, canceling baseline counts and avoiding noise frequencies by adjusting charging and discharging currents, thereby improving detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional capacitive switch is used in outdoor environment, then the touch detection function is provided, but the detection correctness is degraded due to environmental parameter fluctuations
Solution Approach 1:
The patent uses dual-phase charging and discharging with different current values (first charging current ≠ second charging current, first discharging current ≠ second discharging current) to create variable electrical parameters. This allows the system to distinguish between environmental baseline changes and actual touch events by comparing measurements taken under different parameter conditions, thereby maintaining detection correctness despite environmental fluctuations.
Solution Approach 2:
The system performs multiple charging and discharging cycles with different currents and uses the counter to measure time intervals that are then processed by the processor. The processor compares these measurements to identify touch events while canceling out baseline environmental effects. This feedback mechanism allows the system to adapt to environmental changes and maintain reliable detection.
2Measurement precision
If a conventional capacitive switch is used in noisy environment, then the touch detection function is provided, but identification error occurs due to noise interference
Solution Approach 1:
By using different charging currents (first charging current and second charging current) and different discharging currents (first discharging current and second discharging current), the system measures the capacitor's charging and discharging characteristics under multiple parameter conditions. This allows the processor to identify and cancel noise-induced variations by comparing measurements taken at different electrical parameters, thereby improving measurement precision in noisy environments.
Solution Approach 2:
The system performs periodic charging and discharging cycles with the counter measuring time intervals for each cycle. By conducting multiple periodic measurements with different current parameters and processing these sequentially, the system can distinguish between periodic noise patterns and actual touch events, improving touch detection accuracy in noisy environments.
3Measurement precision
If single current charging and discharging is used, then the circuit structure is simple, but the detection accuracy is degraded due to baseline voltage effects
Solution Approach 1:
The patent employs four different current parameters (first charging current, second charging current, first discharging current, second discharging current) to charge and discharge the capacitor. This multi-parameter approach enables the processor to calculate time intervals under different conditions and identify touch events while canceling baseline voltage effects, significantly improving detection accuracy despite the increased circuit complexity.
Solution Approach 2:
The charging process is segmented into two distinct phases with different currents (first charging interval and second charging interval), and the discharging process is segmented into two distinct phases with different currents (first discharging interval and second discharging interval). The counter measures each interval separately, and the processor uses these segmented measurements to improve detection accuracy by eliminating baseline effects.
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 enhances detection accuracy by isolating noise interference and environmental changes, ensuring reliable touch event identification even in noisy and fluctuating conditions.
Implementation Method 1
a detection capacitor being charged and discharged using different currents
Implementation Method 2
a detection capacitor being charged and discharged using different currents
Data Source
AI summary
There is provided a detection chip including a charging circuit, a discharging circuit, a counter and a processor. The charging circuit provides a first charging current within a first charging interval, and provides a second charging current, smaller than the first charging current, within a second charging interval. The discharging circuit provides a first discharging current within a first discharging interval, and provides a second discharging current, smaller than the first discharging current, within a second discharging interval. The counter counts the second charging interval and the second discharging interval. The processor identifies a touch event according to the second charging interval and the second discharging interval.