Capacitive Sensor Button Periodic Scanning for Low Power
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Solution Overview
Problem
Conventional capacitive touch-sensor buttons consume more power than mechanical buttons due to the continuous operation of analog and digital circuits, even when not in use, which is inefficient for battery-powered devices.
Innovation Solution
A low power capacitance sensing module that operates independently of the main clock resources, using a low power oscillator and a sensing circuit that consumes minimal current for most of the time, allowing the CPU to enter a low power state and only briefly increasing power consumption for touch detection, thus minimizing overall current draw.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If capacitive sensor buttons use continuous monitoring circuits, then button responsiveness is improved, but power consumption increases
Solution Approach 1:
The patent implements periodic sampling of capacitive sensor buttons instead of continuous monitoring. The CPU wakes from idle state at scheduled intervals to scan button states, then returns to idle state. This periodic action maintains button responsiveness while dramatically reducing average power consumption, as the high-power CPU operation occurs only briefly during scanning intervals rather than continuously.
2Measurement precision
If CPU continuously scans button states, then detection accuracy is improved, but power consumption increases
Solution Approach 1:
The patent dynamically adjusts CPU operational states based on scanning needs. The CPU transitions between idle (low power) and active (high power) states depending on whether button scanning is required. This dynamic state management allows the system to maintain accurate touch detection capability while minimizing power consumption by keeping the CPU in low-power state most of the time.
Solution Approach 2:
The system performs button scanning at predetermined intervals before actual user interaction might occur. By proactively checking button states periodically, the system ensures detection accuracy is maintained while allowing the CPU to remain in low-power state between scans, rather than continuously monitoring and consuming power.
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 solution enables capacitive touch-sensor buttons to be used with minimal impact on power demand, allowing them to replace mechanical switches in battery-powered devices while maintaining responsiveness and reducing power consumption.
Implementation Method 1
One type of touch-sensor button operates by way of capacitance sensing, utilizing capacitance sensor electrodes. The capacitance detected by a capacitance sensor changes as a function of the proximity of a conductive object on or near the sensor electrode.
Data Source
AI summary
Systems and methods receive multiple of trigger signals and responsive to each trigger signal transition a sensing block from operating in a first mode to operating in a second mode by turning on power to one or more portions of the sensing block. Operating in the second mode includes performing multiple sensor scans during multiple sensing periods of a monitoring period. Based on performing a first scan during a first sensing period, systems and methods transition from operating the sensing block in the second mode to operating the sensing block in the first mode by turning off the power to the one or more portions of the sensing block. Based on performing a second scan during a second sensing period, of the plurality of sensing periods, systems and methods transition a processing module from operating in a first processing mode to operating in a second processing mode.