Capacitive Lid Closure Sensing for Low-Power Electronic Devices
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Solution Overview
Problem
Existing electronic devices face challenges in cost-effectively detecting lid closure due to the use of mechanical switches, which add manufacturing costs and electrostatic discharge risks, and magnetic sensors, which require separate devices and are not cost-efficient.
Innovation Solution
The implementation of capacitive sensors, including transmitter and receiver traces connected to an excitation source, which measure capacitance changes to detect lid closure, utilizing materials that affect sensors in a predictable manner to ensure accurate detection without additional sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mechanical switches are used to detect lid closure, then lid closure detection is achieved, but manufacturing cost increases and electrostatic discharge risks are introduced
Solution Approach 1:
The patent replaces mechanical switches with capacitive sensors to detect lid closure. The capacitive sensor system uses electrical fields rather than mechanical contact, eliminating electrostatic discharge risks while maintaining detection reliability. The sensor traces are integrated into the display assembly, using capacitance changes caused by the proximity of conductive materials when the lid is closed.
Solution Approach 2:
The patent introduces an intermediary material (conductive or capacitive material) between the capacitive sensor and the lid closure event. This material mediates the detection by creating a capacitive coupling when the lid closes, allowing detection without direct mechanical contact or electrostatic discharge pathways.
2Reliability
If magnetic sensors are used to detect lid closure, then lid closure detection is achieved, but device complexity and cost increase due to requiring separate switch devices
Solution Approach 1:
The patent merges the lid closure detection function with the existing display assembly by integrating capacitive sensor traces into it. This eliminates the need for separate magnetic sensors and associated components, reducing device complexity while maintaining detection capability. The sensor traces are formed as part of the display circuitry rather than as a separate subsystem.
Solution Approach 2:
The capacitive sensor traces serve multiple functions: they are part of the display assembly circuitry and simultaneously function as lid closure sensors. This multi-functionality reduces the overall component count and system complexity compared to dedicated magnetic sensor systems.
3Ease of manufacture
If capacitive sensors are used to detect lid closure, then manufacturing cost is reduced and electrostatic risks are eliminated, but sensor accuracy may be affected by environmental factors
Solution Approach 1:
The patent applies local quality by using specific materials with known capacitive properties in strategic locations. The intermediary material is selected to provide consistent capacitive coupling when the lid closes, and the sensor traces are designed with specific geometries to optimize the measurement zone. This localized material selection and geometry control improve measurement precision despite environmental variations.
Solution Approach 2:
The patent utilizes parameter changes in the capacitive system - specifically, the change in capacitance value that occurs when the lid closes and brings conductive materials into proximity. The system is designed to detect this specific parameter change while filtering out other variations, maintaining measurement accuracy through careful threshold selection and signal processing.
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 allows for reliable detection of lid closure without additional sensors, reducing manufacturing costs and electrostatic risks, enabling the device to enter a sleep state or perform sequences of events based on closure, such as turning off the display.
Implementation Method 1
The capacitive sensor may include a transmitter trace (e.g., a metal trace of a printed circuit board) connected to an excitation source (e.g., from an excitation signal, possibly using 250 kHz, among other values). An electric field may form between the transmitter trace and a receiver trace. The field strength at the receiver may be measured and/or transmitted to signal processing/controller.
Implementation Method 2
An electric field may form between the transmitter trace and a receiver trace. The field strength at the receiver may be measured and/or transmitted to signal processing/controller.
Data Source
AI summary
System and method for determining closure of an electronic device. The electronic device may include a top portion and a bottom portion, and may be connecting via a hinge or other closing mechanism. The top portion and/or the bottom portion may include one or more capacitive sensors which provide signals corresponding to physical contact and a controller coupled to the one or more capacitive sensors. The controller may operate to receive the signals from the one or more capacitive sensors, determine if the electronic device has been closed based on the received signals, and initiate a sequence of events corresponding to the closure of the electronic device. The sequence of events may result in the device entering a low power state.