Capacitive Touch Scan Module for Low-Power Sleep Detection
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Solution Overview
Problem
Current capacitive touch sensor technologies require electronic devices to wake up from sleep mode to scan keypads, leading to increased power consumption or delayed response times, complicating user software and power management.
Innovation Solution
An automated scan module that operates independently of the device's power mode, using a state machine to sequence through capacitive touch sensors, perform analog-to-digital conversions, and generate interrupts only when a valid key press is detected, allowing the logic circuits to remain in sleep mode until necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the electronic device wakes up from sleep mode to scan the capacitive touch sensors, then the response time to detection is improved, but the power consumption increases
Solution Approach 1:
The system is divided into two independent scanning mechanisms: a continuous low-power scan that operates during sleep mode and a full-featured scan that operates during active mode. This segmentation allows the device to maintain touch sensitivity without requiring the entire system to wake up, thus resolving the contradiction between fast response time and low power consumption
Solution Approach 2:
A continuous preliminary scan is performed at low power during sleep mode to detect basic touch events. This preliminary action ensures that touch detection capability is maintained without requiring the device to fully wake up, thereby improving response time while minimizing power consumption
2Use of energy by moving object
If the electronic device remains in sleep mode to reduce power consumption, then the power consumption is reduced, but the response time to detection increases
Solution Approach 1:
The scanning function is segmented into a continuous minimal scan that runs during sleep mode and a complete scan that runs during active mode. The continuous minimal scan uses reduced resources to maintain basic detection capability, ensuring that the device can respond to touch events quickly even while in sleep mode, thus resolving the contradiction between power consumption and response time
Solution Approach 2:
The system implements periodic scanning at different intervals depending on the power mode. During sleep mode, a simplified periodic scan occurs at intervals sufficient to detect most touch events, while during active mode, scanning occurs more frequently. This periodic action maintains acceptable response time while minimizing power consumption during sleep mode
3Speed
If the device scans capacitive touch sensors during sleep mode, then the response time is improved, but the complexity of power management increases
Solution Approach 1:
The continuous scan module operates autonomously during sleep mode without requiring intervention from the main processor or complex power management logic. It independently performs basic capacitance measurements and generates wake-up events only when necessary, thereby improving response time while avoiding the addition of complex power management overhead
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 reduces overall power consumption by enabling continuous scanning of capacitive touch sensors without waking the power-consuming logic circuits, simplifying user software and maintaining low power consumption during idle or sleep modes.
Implementation Method 1
the respective one of the plurality of capacitive touch sensors is charged to a voltage value determined by the time period and the current value of the constant current source
Implementation Method 2
a voltage value determined by the time period and the current value of the constant current source
Data Source
AI summary
A scan module of an electronic device scans a capacitive keypad for detection of the actuation of any capacitive touch sensor. This scan module remains in operation even when major power consuming circuits of the electronic device are in a sleep mode, and will not wake up the major power consuming circuits until an action requiring the circuits is needed, thereby, reducing overall power consumption of the electronic device while still maintaining scanning of the capacitive keypad. Upon detection of a valid key press of a capacitive touch sensor, an interrupt to the electronic device brings it out of a sleep mode and into an operating mode for further processing and appropriate action commensurate with the actuation of the specific capacitive touch sensor.