Wireless Charging Circuit Balun and Filter for EMI Reduction

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Solution Overview

Problem

Conventional wireless charging boards face issues with electromagnetic interference (EMI) and safety concerns due to residual energy storage in capacitors, leading to noise interference at specific frequencies, which affects the convenience and safety of wireless charging.

Innovation Solution

A wireless charging circuit incorporating a balun unit and a higher-order filter unit, where the balun converts differential signals and the higher-order filter unit attenuates and filters noise, reducing electromagnetic interference by converting and filtering signals to prevent energy storage in capacitors and eliminating noise at multiplied frequencies.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a conventional filter circuit with inductors and capacitors is used, then the circuit can filter signals, but the capacitors or inductors store energy causing noise interference at multiplied frequencies

Engineering Contradiction:

Improveelectromagnetic interferenceVSAvoidnoise interference at multiplied frequencies

Core Design Contradiction:

Object-affected harmful factorsVSObject-generated harmful factors

Solution Approach 1:

The patent extracts and removes the energy storage function from the filter circuit by eliminating capacitors and inductors. The resonant tank circuit is replaced with a configuration that processes signals without storing energy in reactive components, thereby eliminating the source of multiplied frequency noise while maintaining filtering capability.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces a resonant tank circuit as an intermediary between the oscillator and the transmission coil. This resonant tank circuit acts as a mediator that transfers energy without requiring traditional energy-storing capacitors or inductors in the filter path, thus filtering signals without generating multiplied frequency interference.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Use of energy by moving object

If residual energy is stored in capacitors during signal conversion, then the energy can be transmitted to the transmission coil, but the transmission coil transmits residual energy causing electromagnetic interference

Engineering Contradiction:

Improveenergy transmissionVSAvoidelectromagnetic interference

Core Design Contradiction:

Use of energy by moving objectVSObject-affected harmful factors

Solution Approach 1:

The patent extracts the harmful residual energy before it reaches the transmission coil by using a filter circuit positioned between the resonant tank and the transmission coil. This filter removes residual energy components without requiring energy storage in capacitors, preventing EMI while maintaining useful energy transmission.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent converts the potentially harmful residual energy into a beneficial filtering opportunity by designing the filter circuit to specifically target and remove only the harmful residual components while preserving the main signal energy for transmission to the coil.

Inventive Principle:

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

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 solution effectively attenuates noise at frequencies tripled, quadrupled, or quintupled, ensuring compliance with EMI safety regulations and enhancing the convenience and safety of wireless charging by reducing electromagnetic interference across a range of frequencies.

Implementation Method 1

the balun unit converts the differential signal into a converted signal to be transmitted to the higher-order filter unit

Methodology Applied

Scientific EffectSignal conversion:

Implementation Method 2

The higher-order filter unit filters the converted signal to output a filtered signal to the differential unit

Methodology Applied

Scientific EffectSignal filtering: Filter (electronic)

Implementation Method 3

The transmission coil Co is configured to deliver electric energy to wireless receiving devices

Methodology Applied

Scientific EffectElectromagnetic transmission: Electromagnetic Induction

Data Source

PatentUS10250065B2Wireless charging circuit and charging board thereof

Publication Date: 2019.04.02 DEXIN ELECTRONICS LTD

AI summary

A wireless charging circuit coupled to an oscillation unit. The wireless charging circuit includes a balun unit, a higher-order filter unit and a differential unit. The balun unit is coupled to the oscillation unit. The higher-order filter unit is coupled to the balun unit. The differential unit is coupled to the higher-order filter unit. The differential unit is coupled to a transmission coil. The oscillation unit issues a differential signal to the balun unit, and then the balun unit converts the differential signal into a converted signal to be transmitted to the higher-order filter unit. The higher-order filter unit filters the converted signal to output a filtered signal to the differential unit. The differential unit converts the filtered signal into a differential output signal to be outputted by the transmission coil.