Wireless Power Coil Selection via Magnetic Coupling Coefficient

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Solution Overview

Problem

Wireless charging systems face inefficiencies in power transfer due to variations in magnetic coupling between transmit and receive coils, leading to suboptimal charging performance across different devices and positions.

Innovation Solution

A wireless power system that determines the magnetic coupling coefficient between transmit coils and a receive coil, using this information to selectively choose the most efficient coils for power transmission based on rectifier output voltages and other device characteristics, optimizing power transfer efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a single transmit coil is used in wireless charging, then the device structure is simple, but power transfer efficiency varies significantly with device position and coupling conditions

Engineering Contradiction:

Improvetransmit coil structureVSAvoidpower transfer efficiency

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

The transmit array is divided into multiple independent transmit coils instead of using a single coil. Each coil can be independently controlled and selected based on the receive device position and coupling conditions, allowing the system to optimize power transfer efficiency by activating only the most suitable coil.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system dynamically selects which transmit coil to activate based on real-time coupling coefficients and device positions. This dynamic adaptation allows the system to maintain high power transfer efficiency regardless of where the receive device is placed on the charging surface.

Inventive Principle:

Principle #15Dynamics

2Loss of energy

If multiple transmit coils are used to improve power transfer efficiency, then charging performance is optimized, but device complexity and coil selection control increase

Engineering Contradiction:

Improvepower transfer efficiencyVSAvoidcoil selection control

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The system measures the coupling coefficient between each transmit coil and the receive device, then uses this feedback information to determine which coil provides the optimal coupling. This feedback mechanism enables automatic optimization of power transfer efficiency without requiring complex manual configuration.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The control circuitry automatically performs coil selection based on measured coupling coefficients without requiring user intervention. The system self-optimizes by selecting the transmit coil with the highest coupling coefficient to the receive device, simplifying the user experience while maintaining high efficiency.

Inventive Principle:

Principle #25Self-service

3Loss of energy

If coil selection is based on coupling coefficient measurements, then power transfer efficiency is maximized, but measurement precision and control requirements increase

Engineering Contradiction:

Improvepower transfer efficiencyVSAvoidcoupling coefficient measurement

Core Design Contradiction:

Loss of energyVSMeasurement precision

Solution Approach 1:

Instead of requiring precise measurements across all possible operating conditions, the system performs coupling coefficient measurements only for the currently active transmit coil configuration. This partial measurement approach is sufficient to identify the optimal coil without requiring exhaustive precision across all scenarios.

Inventive Principle:

Principle #16Partial or excessive action

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 enhances wireless power transfer efficiency by ensuring the selection of coils with the highest magnetic coupling coefficients, thereby improving charging performance across various devices and positions.

Implementation Method 1

The coil receives alternating-current wireless power signals from a coil in the wireless charging mat

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

Each transmit coil has a respective magnetic coupling coefficient characterizing its magnetic coupling to the receive coil

Methodology Applied

Scientific EffectMagnetic coupling: Magnetic Field

Data Source

PatentUS11258311B2Wireless power system with coupling-coefficient-based coil selection

Publication Date: 2022.02.22 APPLE INC

AI summary

A wireless power system may have a wireless power transmitting device and a wireless power receiving device. The wireless power receiving device may have a receive coil that receives wireless power signals from the wireless power transmitting device and may have a rectifier that produces direct-current power from the received wireless power signals. The wireless power transmitting device may have an array of transmit coils. Each transmit coil has a respective magnetic coupling coefficient characterizing its magnetic coupling with the receive coil. The wireless power transmitting device may have control circuitry that uses the magnetic coupling coefficient values in selecting transmit coils to use in transmitting wireless power to the wireless power receiving device.