Variable Inductor Feedback Control for Core-Safe Resonance Tuning

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Solution Overview

Problem

Wireless power transfer systems face efficiency reduction due to parasitic variations affecting the resonant frequencies of the wireless power transfer device and target device, and magnetic cores in variable inductors can be permanently degraded by influences like DC magnetic flux, AC magnetic flux, temperature, and physical shock.

Innovation Solution

A control system for a variable inductor with a magnetic core, a control coil, and a sensor coil, which adjusts inductance via a DC control current and monitors permeability to prevent degradation, maintaining operation within a linear range to avoid permanent changes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the inductance of the variable inductor is adjusted to compensate for parasitic variations, then the resonant frequency matching and power transfer efficiency are improved, but the magnetic core may be permanently degraded due to operating outside the linear range

Engineering Contradiction:

Improvepower transfer efficiencyVSAvoidmagnetic core stability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The system continuously monitors the inductance of the variable inductor and adjusts the DC control current to maintain operation within the linear range. This feedback mechanism ensures that the magnetic core operates reliably while still allowing inductance adjustment to compensate for parasitic variations and maintain power transfer efficiency.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The variable inductor dynamically adjusts its inductance by varying the DC control current through the control coil, allowing the system to adapt to changing conditions (parasitic variations) while the control system ensures the adjustment remains within safe operational limits to prevent core degradation.

Inventive Principle:

Principle #15Dynamics

2Adaptability or versatility

If the permeability of the magnetic core is allowed to drop below a certain level, then the inductance can be reduced to adjust resonant frequency, but the magnetic core becomes permanently degraded through whapping

Engineering Contradiction:

Improveinductance adjustment rangeVSAvoidmagnetic core integrity

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The control system monitors the inductance and the DC control current, and uses feedback to determine when the slope exceeds the linearity error. This prevents the permeability from dropping below the level that causes whapping while still allowing sufficient inductance adjustment for resonant frequency matching.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system changes the operating parameters (DC control current) to adjust inductance, but constrains these changes to remain within the linear range where the slope of inductance versus control current does not exceed the linearity error, thereby maintaining magnetic core integrity.

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If the slope of inductance change relative to DC control current is allowed to increase, then greater inductance adjustment capability is achieved, but the linearity error increases causing unpredictable behavior

Engineering Contradiction:

Improveinductance control capabilityVSAvoidinductance linearity

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The system calculates the slope of inductance change relative to DC control current and uses feedback to maintain this slope below a threshold determined by the linearity error. This ensures predictable, linear behavior while still providing sufficient inductance adjustment capability for resonant frequency matching.

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 maintains efficient power transfer by adjusting the inductance of the variable inductor to compensate for parasitic variations and prevents degradation of the magnetic core, ensuring consistent performance.

Implementation Method 1

a control coil wound around the magnetic core... configured to provide a DC control current to the control coil

Methodology Applied

Scientific EffectElectromagnetism: Electromagnet

Implementation Method 2

a sensor coil wound around the magnetic core... an oscillation frequency of the oscillator, an inductance of the variable inductor

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS20250308767A1Variable inductor and control system for the variable inductor

Publication Date: 2025.10.02 ALFRED E MANN FOUND FOR SCI RES

AI summary

A control system includes a variable inductor including a magnetic core, a first coil wound around the magnetic core, and a control coil wound around the magnetic core; and a sensor coil wound around the magnetic core, wherein the first coil wound around the magnetic core is coupled between first and second terminals and has a variable inductance across the first and second terminals.