Resonant Rectifier Capacitor Sensing Zero Crossing

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Solution Overview

Problem

Conventional resonant wireless power transfer systems face inefficiencies due to glitches and inaccuracies in zero crossing detection, leading to degraded power efficiency and output regulation, primarily caused by current sensing methods that introduce delays and jitters.

Innovation Solution

The system employs a resonant rectifier circuit with capacitor sensing, where the voltage across the capacitor is monitored instead of current through the inductor, and a 90° phase-shifted signal is used to control bridge FETs, avoiding switching noise and glitches, thereby enhancing synchronous rectification.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If current sensing method is used to detect zero crossings, then zero crossing detection can be implemented, but delays and jitters occur leading to degraded power efficiency and output regulation

Engineering Contradiction:

Improvezero crossing detection accuracyVSAvoidpower efficiency

Core Design Contradiction:

Measurement precisionVSLoss of energy

Solution Approach 1:

The patent introduces a capacitor as an intermediary element in the resonant circuit. Instead of directly sensing current through the inductor, the system senses voltage across the capacitor, which serves as a mediator that provides accurate zero crossing information without the delays and jitters associated with direct current sensing. This intermediary approach resolves the contradiction by maintaining measurement precision while eliminating energy losses.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces the conventional current sensing method with a voltage sensing method across the capacitor. This substitution changes the sensing mechanism from direct electrical current measurement to voltage measurement, which eliminates the delays and jitters inherent in current sensing circuits while maintaining accurate zero crossing detection capability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If conventional current sensing is used, then zero crossing detection is achieved, but glitches and inaccuracies occur degrading output regulation

Engineering Contradiction:

Improveoutput regulationVSAvoidzero crossing detection accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The capacitor acts as an intermediary that provides a clean voltage signal for zero crossing detection. By sensing voltage across the capacitor rather than current through the inductor, the system eliminates glitches and inaccuracies that degrade output regulation, while maintaining high measurement precision for timing control.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent extracts the zero crossing detection function from the current sensing path and relocates it to the capacitor voltage sensing path. This separation removes the source of glitches and inaccuracies from the detection mechanism, thereby improving both reliability of output regulation and precision of timing information.

Inventive Principle:

Principle #2Taking out (Extraction)

3Power

If switching frequency is increased to facilitate power transfer over longer distances, then power transfer capability is improved, but size of system passive components must be reduced

Engineering Contradiction:

Improvepower transfer capabilityVSAvoidpassive component size

Core Design Contradiction:

PowerVSVolume of stationary object

Solution Approach 1:

The patent employs precise timing control based on accurate zero crossing detection from capacitor voltage sensing. This enables optimal switching frequency and phase control, allowing the system to operate at higher frequencies for extended power transfer distances while maintaining efficient power transfer and enabling reduction of passive component sizes through optimized operating parameters.

Inventive Principle:

Principle #35Parameter changes

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 provides a more robust and efficient wireless power transfer by eliminating glitches and improving zero current detection accuracy, resulting in improved power efficiency and output regulation.

Implementation Method 1

the frequency of operation of wireless charging systems is increasing to facilitate power transfer over longer distances

Methodology Applied

Scientific EffectResonance: Resonance

Implementation Method 2

The synchronous rectifier is configured to identify zero crossings of alternating current flowing through the inductor based on voltage across the capacitor, and control synchronous rectification of the alternating current

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS11283361B2Resonant rectifier circuit with capacitor sensing

Publication Date: 2022.03.22 TEXAS INSTRUMENTS INC

AI summary

A wireless power transfer system using a resonant rectifier circuit with capacitor sensing. A wireless power transfer system includes a power receiver resonant circuit and a synchronous rectifier. The power receiver resonant circuit includes an inductor and a capacitor connected in series with the inductor. The synchronous rectifier is configured to identify zero crossings of alternating current flowing through the inductor based on voltage across the capacitor, and control synchronous rectification of the alternating current based on timing of the zero crossings.