Wireless Power Feeder Overcurrent Protection via Phase Detection

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Solution Overview

Problem

Existing wireless power feeding systems face challenges in effectively protecting electronic circuits from overcurrent, particularly in magnetic field resonance type systems, where high current flows can lead to increased temperatures and delayed responsiveness in overcurrent detection, potentially damaging the circuit.

Innovation Solution

A wireless power transmission system that includes a feeding coil, a power transmission control circuit, a phase detection circuit, and a protection circuit, which monitors current flow and adjusts the drive frequency to reduce power transmission efficiency when overcurrent is detected, thereby preventing damage to the electronic circuit.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If temperature sensor monitoring is used to detect overcurrent, then overcurrent protection is achieved, but responsiveness is low and device complexity increases

Engineering Contradiction:

Improveovercurrent protectionVSAvoidresponsiveness

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent replaces the temperature-based detection mechanism (thermal effect) with a current-based detection mechanism using a current sensor. This substitution allows direct electrical measurement of current flow, eliminating the time delay inherent in thermal response and providing immediate overcurrent detection and protection.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces a current sensor as an intermediary device that directly measures current flow in the feeding coil. This intermediary provides real-time current information to the control circuit, enabling rapid response without the intermediate step of temperature measurement and conversion.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If temperature sensor is mounted to the coil, then overcurrent detection is possible, but device complexity increases

Engineering Contradiction:

Improveovercurrent detectionVSAvoidconfiguration complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent substitutes the mechanical/thermal measurement approach (mounting temperature sensors to the coil) with an electrical measurement approach using a current sensor. This simplifies the configuration by eliminating the need for physical sensor mounting while providing more direct and reliable overcurrent detection.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Loss of energy

If high current flows in feeding coil, then power transmission efficiency is high, but electronic circuit damage risk increases

Engineering Contradiction:

Improvepower transmission efficiencyVSAvoidovercurrent damage risk

Core Design Contradiction:

Loss of energyVSObject-affected harmful factors

Solution Approach 1:

The patent implements a feedback control mechanism where the current sensor continuously monitors current flow in the feeding coil and provides real-time information to the control circuit. When overcurrent is detected, the control circuit adjusts the drive frequency to reduce power transmission efficiency, thereby reducing current flow and preventing circuit damage while maintaining efficient operation under normal conditions.

Inventive Principle:

Principle #23Feedback

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

The system provides effective protection against overcurrent in wireless power feeding with a simple configuration, ensuring the safety and longevity of electronic circuits by suppressing high current flow and reducing power transmission efficiency when necessary.

Implementation Method 1

The type (A) utilizing electromagnetic induction has generally been employed in familiar home appliances such as an electric shaver

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

The type (C) utilizing resonance phenomenon of magnetic field (for intermediate range)

Methodology Applied

Scientific EffectMagnetic field resonance: Resonance

Data Source

PatentUS9356474B2Wireless power feeder and wireless power transmission system

Publication Date: 2016.05.31 TDK CORP

AI summary

A feeding coil circuit 120 feeds power by wireless from a feeding coil L2 to a receiving coil L3 based on a magnetic field resonance phenomenon between the feeding coil L2 and receiving coil L3. A transmission power control circuit 200 supplies AC power at a drive frequency to the feeding coil L2 to make the feeding coil L2 feed the AC power to the receiving coil L3. A phase detection circuit 114 measures a phase difference between a current phase of the AC power and a voltage phase thereof. The power transmission control circuit 200 adjusts the drive frequency in accordance with the phase difference. A protection circuit 122 adjusts the phase difference in an increasing direction when the current flowing in the feeding coil L2 increases.