Symmetrical Wearable Charging Interface for Reversible Power and Control

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Solution Overview

Problem

Wearable devices such as glasses and watches face challenges due to limited space and power resources, requiring specialized charge and control systems that differ from those used in other environments, and existing solutions like USB form factors are often too complex for these devices.

Innovation Solution

A symmetrical interface with contact pads and field effect transistors that allow for reversible charging and communication, using a custom cable with magnetic fastening to ensure proper alignment and manage charging and communication states efficiently, thereby simplifying the charging and control process while preventing damage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a standard USB charging interface is used, then charging functionality is achieved, but the device complexity and space requirements increase

Engineering Contradiction:
Improvecharging functionalityVSAvoidinterface complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The charging interface is designed to perform multiple functions: it serves as both a charging port and a wired control/communication port. The same physical interface and contact pads are used for both power transmission and data communication, eliminating the need for separate USB connectors and reducing overall device complexity while maintaining reliable charging functionality

Inventive Principle:
Principle #6Universality (Multi-functionality)

2Ease of operation

If a symmetrical reversible interface is implemented, then ease of operation is improved, but circuit complexity increases

Engineering Contradiction:
Improveconnector alignmentVSAvoidcircuit symmetry requirements
Core Design Contradiction:
Ease of operationVSDevice complexity

Solution Approach 1:

While the physical connector interface is made symmetrical for ease of insertion, the underlying circuit implementation uses asymmetrical field effect transistor configurations with specific polarity assignments. This allows the simple symmetrical external interface to mask the complex asymmetrical circuit requirements, achieving both ease of operation and functional reliability

Inventive Principle:
Principle #4Asymmetry

3Volume of moving object

If wired control and charging are combined in one interface, then device space is reduced, but signal interference increases

Engineering Contradiction:
Improvedevice spaceVSAvoidsignal interference
Core Design Contradiction:
Volume of moving objectVSObject-affected harmful factors

Solution Approach 1:

The combined interface is segmented into separate contact pads for power, ground, and data signals. By physically separating these signal paths on the connector and using dedicated FETs for each function, the design reduces signal interference while maintaining a compact single-interface form factor. The segmentation allows independent optimization of each signal path

Inventive Principle:
Principle #1Segmentation

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 efficient charging and control of wearable devices with limited circuitry, ensuring damage-resistant connections and effective communication, even with complex form factors, by using a reversible and symmetrical interface that adapts to different orientations and states.

Implementation Method 1

using a custom cable with magnetic fastening to ensure proper alignment

Methodology Applied
Scientific EffectMagnetic fastening: Magnetism

Data Source

PatentEP3926787B1Circuits and methods for wearable device charging and wired control
Publication Date: 2024.05.22 SNAP INC
  • EP3926787B1 patent drawingFigure 1
  • EP3926787B1 patent drawingFigure 2
  • EP3926787B1 patent drawingFigure 3

AI summary

Methods and devices for wired charging and communication with a wearable device are described. In one embodiment, a symmetrical contact interface comprises a first contact pad and a second contact pad, and particular wired circuitry is coupled to the first and second contact pad to enable charging as well as receive and transmit communications via the contact pads as part of various device states.