Capacitive Proximity Sensing in Wireless Power Systems

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing wireless power transfer systems lack efficient and safe methods to determine the location and presence of objects within their charging vicinity, particularly in capacitive proximity sensing, which is crucial for optimizing power transmission and ensuring safety around biological entities.

Innovation Solution

A wireless power transmission system that uses a capacitive presence detection method involving metallic plates and a transmit antenna to detect changes in capacitance, allowing for the determination of object location and varying the power transmission characteristics based on detected changes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If wireless power transmission is performed without object detection, then power transmission efficiency is maintained, but safety around biological entities cannot be ensured

Engineering Contradiction:

Improveelectromagnetic exposure to biological entitiesVSAvoiddetection system complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The metallic plates serve dual functions: they act as both shielding elements for the transmit antenna and as capacitive sensors for object detection. This multi-functionality eliminates the need for separate detection hardware, resolving the contradiction between safety requirements and device complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The system uses its own electromagnetic field to both transmit power and detect objects simultaneously. The capacitive coupling between the excited metallic plates and nearby objects provides automatic detection without requiring external sensing systems, allowing the system to serve its own safety needs.

Inventive Principle:

Principle #25Self-service

2Measurement precision

If capacitive proximity sensing is implemented to detect object location, then safety is improved, but system complexity increases

Engineering Contradiction:

Improveobject location determinationVSAvoidsensing system complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The same metallic plates that provide electromagnetic shielding also function as capacitive sensors. By measuring changes in capacitance between the excited plates and nearby objects, the system achieves precise location determination without adding separate sensing components.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The system replaces complex mechanical or optical detection systems with a simple capacitive sensing approach. The electromagnetic field naturally interacts with nearby objects through capacitive coupling, providing location information through electrical measurements rather than mechanical or optical systems.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Object-affected harmful factors

If the wireless power system uses metallic plates for shielding, then electromagnetic radiation is reduced, but the ability to detect object presence is compromised

Engineering Contradiction:

Improveelectromagnetic radiationVSAvoidobject presence detection

Core Design Contradiction:

Object-affected harmful factorsVSDifficulty of detecting and measuring

Solution Approach 1:

The metallic plates, which could be seen as creating electromagnetic shielding that might hide objects, actually create capacitive coupling effects that enhance detection. The excited plates generate an electric field that interacts with nearby objects, converting the shielding function into a beneficial sensing mechanism.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The metallic plates simultaneously provide electromagnetic radiation shielding and enable capacitive proximity sensing. The same structure that reduces harmful radiation also creates the electric field necessary for detecting object presence and location.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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

Enables precise location determination of objects within the charging area and adjusts power transmission to ensure efficient charging while ensuring safety by reducing electromagnetic exposure to biological entities.

Implementation Method 1

exciting a first part of a wireless power transmission system, via a wireless power transmitter

Methodology Applied

Scientific EffectElectromagnetic Induction: Electromagnetic Induction

Implementation Method 2

detecting, in the presence of a non-charging object, a first change in a first parameter. The first parameter is indicative of a coupling between the non-charging object and the first part

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentEP2885880B1Wireless power system with capacitive proximity sensing

Publication Date: 2020.11.25 QUALCOMM INC

Figure 1~3
Figure 4~5
Figure 6

AI summary

This disclosure provides systems, methods and apparatus for tuning a transmit coil for operation in a plurality of frequency bands. In one aspect, a method of wireless power transmission is provided. The method includes exciting a first part of a wireless power transmission system, via a wireless power transmitter. The method further includes detecting, in the presence of a non-charging object, a first change in a first parameter. The first parameter is indicative of a coupling between the non-charging object and the first part. The method further includes varying a characteristic of the wireless power transmission based on said first change.