Capacitive Touch Sensing with Peak Voltage Sampling
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Solution Overview
Problem
Existing touch input detection systems are burdensome and inefficient, particularly when rapid measurements are required, as they digitally process each electrode output, consuming significant computing resources.
Innovation Solution
The system measures peak voltage at electrodes over a measurement period and defers digital signal processing until after peak electrode capacitance is sampled, using a capacitive sensor with a driver circuit, measurement circuit, and signal processing circuit, suitable for both self-capacitance and mutual capacitance, to determine touch inputs efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If digital signal processing is performed on each electrode output in real-time, then touch input detection accuracy is improved, but computing resource consumption increases significantly
Solution Approach 1:
The patent applies preliminary action by performing analog-to-digital conversion and peak detection before full digital signal processing. The measurement circuit captures peak voltage values and converts them to digital signals in advance, so that subsequent processing only requires comparing pre-processed data rather than analyzing raw continuous signals, thereby reducing computing resource consumption while maintaining detection accuracy
Solution Approach 2:
The patent extracts only the essential information (peak voltage values) from the electrode outputs using dedicated measurement circuits. By extracting and storing only the peak values rather than processing the entire signal waveform digitally, the system reduces the data volume requiring digital processing while preserving the critical touch detection information
2Speed
If rapid measurements are performed on multiple electrodes simultaneously, then response time is improved, but device complexity increases
Solution Approach 1:
The patent segments the measurement function into dedicated measurement circuits, each responsible for a specific electrode or electrode pair. This segmentation allows simultaneous independent measurement of multiple electrodes without requiring complex centralized control logic, as each measurement circuit operates autonomously to capture peak voltages
Solution Approach 2:
The measurement circuits are designed to autonomously perform peak detection and voltage measurement without requiring complex external control. Each measurement circuit self-manages its measurement cycle, capturing peak values and outputting digital signals independently, which simplifies the overall system architecture while enabling rapid parallel measurements
3Use of energy by moving object
If peak voltage measurement is deferred until after sampling, then computing resources are conserved, but measurement precision may be compromised
Solution Approach 1:
The patent replaces complex digital signal processing mechanisms with simpler analog measurement circuitry that directly detects peak voltages. The measurement circuits use analog comparators and peak detection circuits to identify and hold peak voltage values, converting them to digital signals only when peaks are detected, thereby avoiding continuous digital processing while maintaining precise peak measurement
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 conserves computing resources and enables rapid measurement of electrode capacitance, reducing power draw and response time while maintaining high signal fidelity and accuracy in detecting touch inputs.
Implementation Method 1
The driver circuit is adapted to providing a stimulus voltage, for example a repeating square wave, to a capacitive coupling
Implementation Method 2
The measurement circuit includes a peak detector and provides an output proportional to the peak voltage across the capacitive coupling over a measurement period
Implementation Method 3
The measurement circuit includes a strobe electrode and a sense electrode defining a capacitive coupling therebetween, the capacitive coupling being adapted to vary in response to a touch input
Data Source
AI summary
Systems and methods for determining a touch input are provided. The systems and methods generally include measuring the peak voltage at an electrode over a measurement period and determining a touch input based on the peak voltage. The systems and methods can conserve computing resources by deferring digital signal processing until after a peak electrode capacitance has been sampled. The systems and methods are suitable for capacitive sensors using self-capacitance and capacitive sensors using mutual capacitance. The systems and methods are also suitable for capacitive buttons, track pads, and touch screens, among other implementations.