Variable Reactive Element in Resonant Converter Circuit

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Solution Overview

Problem

Resonant converters in Inductively Coupled Power Transfer (ICPT) systems face significant inefficiencies due to undesirable frequency shifts caused by load or circuit parameter variations, which are difficult to manage with existing complex and costly designs.

Innovation Solution

A resonant converter with phase sensing and switch control mechanisms that selectively connect or disconnect a reactive element, such as an inductor or capacitor, to vary the effective reactance and maintain the resonant frequency, using phase and frequency sensing to adjust the timing of the reactive element's connection to the resonant circuit.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If multiple individual capacitors are switched in or out of the resonant circuit to control frequency, then the resonant frequency can be adjusted in steps, but the circuit complexity and cost increase significantly

Engineering Contradiction:

Improvefrequency adjustment capabilityVSAvoidcircuit complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent applies dynamics by making the reactance of the reactive element variable rather than fixed. The reactive element's reactance is dynamically adjusted based on the sensed phase or frequency to maintain resonance, replacing the static multiple-capacitor switching approach with a continuous variable reactance mechanism controlled by timing adjustments.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the parameter being controlled from discrete capacitor values to the timing (phase) of switching a single reactive element. By varying the turn-on/turn-off timing of the second switching means relative to the resonant cycle, the effective reactance is continuously adjustable, maintaining frequency adaptability while reducing circuit complexity.

Inventive Principle:

Principle #35Parameter changes

2Device complexity

If load variations are limited to make the system function effectively with stepwise frequency control, then system simplicity is maintained, but the adaptability to real-world applications is reduced

Engineering Contradiction:

Improvesystem simplicityVSAvoidload variation tolerance

Core Design Contradiction:

Device complexityVSAdaptability or versatility

Solution Approach 1:

The patent implements feedback by sensing the phase or frequency of the resonant circuit and using this information to control the timing of the second switching means. This closed-loop feedback mechanism automatically adjusts the reactive element's effective reactance in response to load variations, maintaining resonance without requiring complex circuit design or limiting load ranges.

Inventive Principle:

Principle #23Feedback

3Reliability

If complex LC converting networks are used to overcome frequency shifts, then frequency stability is improved, but the manufacturing cost and design complexity increase

Engineering Contradiction:

Improvefrequency stabilityVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent applies self-service by enabling the resonant converter to automatically maintain its own resonant frequency through internal phase or frequency sensing and automatic adjustment of the reactive element's timing. This self-regulating mechanism eliminates the need for complex external LC converting networks or third-generation power supply architectures, reducing manufacturing cost while maintaining frequency stability.

Inventive Principle:

Principle #25Self-service

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 solution stabilizes the resonant frequency, enhancing power transfer efficiency and reducing the impact of load variations, thereby maintaining system performance across different operating conditions.

Implementation Method 1

a reactive element which may be an inductor or a capacitor

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

a reactive element which may be an inductor or a capacitor

Methodology Applied

Scientific EffectInductance: Inductor

Implementation Method 3

phase sensing means to sense the phase of a voltage or current in the resonant circuit

Methodology Applied

Scientific EffectPhase detection:

Implementation Method 4

switch control means operable to control the second switching means to vary the effective reactance of the reactive element

Methodology Applied

Scientific EffectResonance: Resonance

Data Source

PatentUS8050068B2Variable reactive element in a resonant converter circuit

Publication Date: 2011.11.01 AUCKLAND UNISERVICES LTD

AI summary

A resonant converter is provided which may be used for supplying power to the primary conductive path of an inductively coupled power transfer (ICPT) system. The converter includes a variable reactive element in the resonant circuit which may be controlled to vary the effective inductance or capacitance of the reactive element. The frequency of the converter is stabilised to a nominal value by sensing the frequency of the converter resonant circuit, comparing the sensed frequency with a nominal frequency and varying the effective inductance or capacitance of the variable reactive element to adjust the converter frequency toward the nominal frequency.