Transmitter-Side WPT Control via Reflected Impedance

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing wireless power transfer (WPT) systems require knowledge of mutual inductance or wireless communication for effective power control between transmitter and receiver coils, which is impractical for applications like wireless charging of electric vehicles and consumer electronics where coil positions vary.

Innovation Solution

A WPT system that uses a decoupling switch and intermediate capacitor for primary-side control, regulating voltage or current without needing mutual inductance information or wireless communication, by utilizing the voltage or current of the intermediate capacitor as indicators for power flow control.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If wireless communication systems are used to feed information from receiver to transmitter for feedback control, then power control capability is improved, but device complexity and system cost increase

Engineering Contradiction:

Improvepower control capabilityVSAvoidsystem complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent extracts the feedback control function from the wireless communication channel and implements it entirely on the primary side by detecting reflected impedance changes. This removes the need for wireless feedback communication hardware and protocols, reducing system complexity while maintaining power control capability.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent makes the primary side detection circuit serve multiple functions: it detects both the power transfer status and the reflected impedance changes caused by decoupling switch operations. This multi-functionality eliminates the need for separate feedback communication systems.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Measurement precision

If mutual inductance information is required for primary control, then power flow control accuracy is improved, but ease of operation deteriorates due to position sensitivity

Engineering Contradiction:

Improvepower flow control accuracyVSAvoidoperation simplicity

Core Design Contradiction:

Measurement precisionVSEase of operation

Solution Approach 1:

The system uses the reflected impedance changes as natural indicators of power transfer status. The decoupling switch operations automatically create detectable impedance variations that the primary side circuit uses to infer receiver status without requiring explicit position or mutual inductance data.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent changes the control parameter from mutual inductance (which varies with position) to reflected impedance (which changes discretely with decoupling switch operations). This parameter transformation makes the system insensitive to coil position variations while maintaining control accuracy.

Inventive Principle:

Principle #35Parameter changes

3Loss of energy

If decoupling switch is used to isolate load, then power transfer efficiency is improved, but control complexity increases

Engineering Contradiction:

Improvepower transfer efficiencyVSAvoidcontrol complexity

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent implements feedback control where the primary side detects reflected impedance changes caused by decoupling switch operations and adjusts primary circuit parameters accordingly. This automatic feedback mechanism manages the control complexity while maintaining the efficiency benefits of load isolation.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

Instead of the secondary side controlling the decoupling switch based on local conditions, the patent inverts the control flow: the primary side detects the effects of decoupling operations and sends control commands back to the secondary side, reversing the traditional control direction.

Inventive Principle:

Principle #13The other way round (Inversion)

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 efficient and precise power control in WPT systems without requiring mutual inductance knowledge or wireless communication, improving energy efficiency and adaptability to varying coil positions.

Implementation Method 1

Energy is transferred wirelessly through magnetic coupling of magnetic flux between the transmitter winding and the receiver winding

Methodology Applied

Scientific EffectMagnetic coupling: Electromagnetic Induction

Data Source

PatentUS10305331B2Transmitter-side control of wireless power transfer systems without using mutual coupling information or wireless feedback

Publication Date: 2019.05.28 THE UNIVERSITY OF HONG KONG

AI summary

Wireless power transfer systems and methods are provided. No wireless communication system is necessary feedback output information from the receiver side to the transmitter side. Nor is any knowledge of the mutual coupling or mutual inductance between the transmitter side and the receiver side required. A system can include an intermediate capacitor in the receiver circuit as a power flow indicator and hysteresis on-off switching actions of a decoupling power switch in the receiver circuit to regulate the DC voltage of the intermediate capacitor (for voltage-control) and the load current (for current-control) at a rated value within a narrow tolerance band. The turn-on and turn-off times of the decoupling switch in the receiver circuit can be detected in the transmitter circuit from, for example, the primary winding current or voltage. This can be used to meet the power demand in the receiver circuit dynamically.