Touchscreen Power Mode Switching via Piezoelectric Sensing
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Solution Overview
Problem
Projected capacitance touch technologies consume higher power, particularly in battery-powered devices, leading to increased device performance impact and reduced battery life.
Innovation Solution
A method and apparatus for a projected capacitive touchscreen that switches between touch detect mode and scan mode, where in touch detect mode, no voltage is applied to transmitter channels, allowing for low-power touch detection by monitoring charge changes on sensor channels, and transitioning to scan mode for capacitance measurement upon detecting a touch event.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If continuous scanning mode is used for touch detection, then touch detection accuracy is improved, but power consumption increases
Solution Approach 1:
The system dynamically switches between two operational modes: touch detect mode for low-power operation and scan mode for high-accuracy detection. The controller activates touch detect mode during periods without touch events to minimize power consumption, and transitions to scan mode when a touch event is detected, thereby adapting the detection strategy to real-time conditions and resolving the contradiction between continuous accuracy and power savings.
Solution Approach 2:
Instead of continuous scanning, the system employs periodic touch detection through the piezoelectric layer at lower power intervals, then performs comprehensive scanning only when triggered by a detected touch event. This periodic approach replaces continuous high-power operation with intermittent low-power monitoring, achieving significant power reduction while maintaining detection capability.
2Use of energy by moving object
If touch detect mode is used with no voltage applied, then power consumption is reduced, but touch detection capability is limited
Solution Approach 1:
The piezoelectric layer serves as an intermediary sensing mechanism that operates independently of the conventional voltage-driven transmitter channels. It detects touch events through mechanical stress-induced electrical charge changes, enabling low-power touch detection without requiring voltage application to the transmitter network. This intermediary approach maintains detection reliability while dramatically reducing power consumption.
Solution Approach 2:
The system replaces the traditional electrical field-based continuous scanning mechanism with a mechanical stress-based detection system using the piezoelectric layer. This substitution allows touch events to be detected through physical pressure changes rather than continuous electrical field monitoring, enabling the system to operate in a ultra-low-power state while maintaining full touch detection capability through the mechanical-to-electrical conversion in the piezoelectric material.
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 reduces power consumption by enabling touch detection without continuous scanning, allowing for accurate touch event detection and location tracking with reduced power usage, enhancing battery life and device performance.
Implementation Method 1
A projected capacitive touchscreen having a stack-up which includes a piezoelectric layer
Implementation Method 2
monitoring an amount of charge on the at least one channel
Data Source
Figure 1
Figure 2A~2B
Figure 3A~4
AI summary
Switching of power modes for touch screens is disclosed. In example embodiments a touch detect mode may be activated for touchscreen operation. The touchscreen may be a projected capacitance screen that includes force sensing based on piezo electric sensors. The touch detect mode may be a low power mode in which at least one channel, but fewer than all channels of the touch screen are monitored. When is determined that a touch event has occurred a switch to a scan mode for touchscreen operation may be performed. Scan mode may be a higher power mode in which all channels of the touch screen are scanned at least for position sensing. The touch detect mode monitoring may be implemented by monitoring the total charge on the at least one channel and providing a voltage signal. When the voltage signal meets predetermined criteria an indication of a touch event may be generated.