Touch Sensing Circuit AC DC Mode Switching Power Saving
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Solution Overview
Problem
Capacitive touch sensing systems in electronic devices continuously consume power to maintain a driving voltage, leading to reduced battery life and vulnerability due to mechanical buttons, which are prone to failure and water/dust ingress.
Innovation Solution
Implementing a touch sensing circuit that switches between AC and DC voltage modes to conserve power, allowing detection of touch events without continuous AC voltage, thereby reducing the need for mechanical buttons and enhancing durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If continuous AC voltage is provided to conducting wires for capacitive touch sensing, then touch detection functionality is maintained, but power consumption increases
Solution Approach 1:
The patent implements periodic switching between AC voltage mode (for touch detection) and DC voltage mode (for power saving). The system periodically transitions to AC mode when touch events are detected and returns to DC mode for power conservation, resolving the contradiction between maintaining continuous functionality and reducing power consumption.
Solution Approach 2:
The patent dynamically adjusts the voltage mode based on operational needs. The system transitions from static continuous AC voltage to dynamic switching between AC and DC modes, optimizing power consumption while maintaining touch detection capability when needed.
2Ease of operation
If mechanical buttons are used for device control, then user input functionality is provided, but device reliability decreases due to water and dust ingress
Solution Approach 1:
The patent replaces mechanical buttons with a capacitive touch sensing system that uses electrical fields instead of mechanical contact. The touch sensing circuit detects finger proximity through capacitive coupling, eliminating moving parts and sealing requirements, thus improving device reliability while maintaining user input functionality.
3Ease of operation
If mechanical buttons with movable parts are used, then tactile feedback is provided, but component lifespan is reduced
Solution Approach 1:
The patent substitutes mechanical button structures with solid-state capacitive touch sensing. The touch sensing circuit provides tactile feedback through haptic actuators or visual feedback while eliminating mechanical wear, significantly extending component lifespan and eliminating the need for replacement.
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 power-saving mode extends the device's lifespan by minimizing button usage and reducing failure risks from water and dust ingress, while maintaining touch input functionality.
Implementation Method 1
capacitive touch control techniques... determine the location of a touch point by measuring a voltage drop of a driving voltage as a result of capacitive variation on a conducting wire touched or approached by the finger or stylus
Data Source
AI summary
A touch sensing circuit is provided. The circuit is configured to connect to a conducting wire in a touch area for measuring a signal variation. In a driving mode, the wire is coupled to AC voltage. If a first voltage variation which exceeds a first threshold is measured by the circuit, it is determined that something is approaching the touch area near the wire. In a passive mode, the wire is coupled to DC voltage. If a second voltage variation which exceeds a second threshold is measured by the circuit, it is determined that something is approaching the touch area near the wire. When measuring the second voltage variation, no AC voltage is coupled to the wire.