Magnetic Biasing to Shift Core Deformation Frequency
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Solution Overview
Problem
Switching power supplies generate audible noise due to mechanical deformation of ferromagnetic cores caused by magnetostriction, which is not effectively addressed by existing technologies.
Innovation Solution
A magnetic component is introduced to offset the magnetomotive force in the magnetic circuit, shifting the frequency of mechanical deformation outside the audible range by selecting or manufacturing the component based on the circuit's operating conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a magnetic circuit is used to transfer energy in a switching power supply, then energy transfer efficiency is improved, but audible noise is generated due to magnetostriction
Solution Approach 1:
The patent applies parameter changes by introducing a magnetic bias component that shifts the operating point of the magnetic core. This changes the magnetic flux density parameters to operate on a more linear portion of the B-H curve, reducing magnetostriction effects and thereby decreasing audible noise while maintaining energy transfer efficiency
Solution Approach 2:
The magnetic bias component acts as an intermediary element in the magnetic circuit. It provides a DC bias flux that mediates the AC flux variations, reducing the peak-to-peak flux swing and consequently reducing the mechanical deformation and audible noise generated by magnetostriction
2Object-generated harmful factors
If the magnetic flux density swing is reduced to decrease magnetostriction, then audible noise is reduced, but energy transfer capability may be compromised
Solution Approach 1:
The patent changes the operating parameters by introducing a DC bias flux that shifts the magnetic operating point. This allows the AC flux swing to be reduced (decreasing magnetostriction and noise) while the bias flux maintains the magnetic circuit's energy transfer capability through the controlled permeability region
3Object-generated harmful factors
If a magnetic bias component is added to offset magnetomotive force, then audible noise is reduced, but device complexity increases
Solution Approach 1:
The patent merges the magnetic bias function with existing magnetic circuit components. The bias is implemented using a winding on the same core that also carries the energy transfer function, combining multiple functions into a single integrated magnetic structure rather than adding separate components
Solution Approach 2:
The magnetic circuit components are designed to serve multiple functions: the same core and windings that perform energy transfer also provide the magnetic bias function. This multi-functionality reduces overall device complexity by eliminating the need for separate biasing components
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 reduces audible noise by ensuring the magnetic circuit's mechanical deformation occurs at frequencies outside human hearing range, improving the operational silence of switching power supplies.
Implementation Method 1
Ferromagnetic materials, including ferrites, respond mechanically to magnetic fields according to a process of magnetostriction. Magnetostriction is a property giving rise to variation in a magnetic material's shape (e.g., length) in response to variations of an applied magnetic field.
Data Source
AI summary
Presented herein are methods and apparatus for biasing magnetic circuits to reduce audible noise from a switching power supply. A magnetic component (e.g., a magnet) is constructed and provided to a core (e.g., a ferromagnetic core) to offset (i.e., bias) an applied magnetomotive force. By selecting and/or manufacturing the magnetic component based on a circuit operating condition, the offset may be tailored to advantageously shift a frequency of mechanical deformation outside the audible noise range. In a switching power supply with fixed peak current, the offset to the applied magnetomotive force may be determined, at least in part, by the fixed peak.