On-Vehicle Power Conversion Noise Reduction via Eddy Current Damping
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Solution Overview
Problem
On-board power conversion devices face challenges in reducing both common-mode and normal-mode noise in direct current power, with existing solutions either failing to effectively address a wide frequency band of normal-mode noise or leading to device enlargement.
Innovation Solution
An on-board power conversion device incorporating a noise reducer with a common-mode choke coil and smoothing capacitor, along with a damping portion that intersects with the magnetic path of leakage flux to lower the Q factor of the low-pass filter circuit, reducing both common-mode and normal-mode noise without the need for additional noise-reducing coils and minimizing device size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a wide frequency band of normal-mode noise is reduced, then noise reduction effectiveness is improved, but device size enlarges
Solution Approach 1:
The patent combines the common-mode noise reduction function and normal-mode noise reduction function into a single integrated noise reducer. The common-mode choke coil with its magnetic core structure simultaneously provides common-mode impedance and generates leakage flux that, when intersected by the damping portion, creates eddy currents to reduce normal-mode noise. This merging eliminates the need for separate dedicated coils for each noise type, preventing device enlargement while achieving wide frequency band noise reduction.
Solution Approach 2:
The damping portion acts as an intermediary element that converts the leakage flux from the common-mode choke coil into eddy currents. This intermediary mechanism enables normal-mode noise reduction without requiring additional active components or increasing device size. The damping portion mediates between the magnetic field and the noise reduction function, achieving versatile noise suppression across wide frequency bands.
2Object-affected harmful factors
If a damping resistor is used to lower Q factor, then normal-mode noise reduction is improved, but heat generation increases and device size enlarges
Solution Approach 1:
The patent replaces the conventional damping resistor (electrical component causing heat loss) with a damping portion that utilizes electromagnetic induction. The damping portion intercepts leakage flux and generates eddy currents that produce magnetic damping effects without the continuous resistive heating of a damping resistor. This substitution reduces energy loss as heat while achieving the same Q factor reduction and normal-mode noise reduction效果.
Solution Approach 2:
The patent changes the damping mechanism from resistive damping (damping resistor) to eddy current damping (damping portion). This parameter change in the damping approach fundamentally alters how energy is dissipated - from continuous resistive heating to transient eddy current effects that are more efficient and generate less heat. The damping portion's position intersecting with leakage flux paths optimizes the eddy current generation while minimizing energy loss.
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
Effectively reduces common-mode and normal-mode noise across a wide frequency band, enhancing versatility and preventing device enlargement, while minimizing heat generation and allowing for compact design.
Implementation Method 1
the common-mode choke coil reduces common-mode noise contained in direct current power that is the conversion subject
Implementation Method 2
The damping portion is located at a position intersecting with a magnetic path of a leakage flux produced from the common-mode choke coil and produces an eddy current with the leakage flux
Data Source
AI summary
This on-vehicle power conversion apparatus is provided with: a power conversion circuit to which DC power is inputted; and a noise reduction unit that is configured to reduce common-mode noise and normal-mode noise which are included in the DC power and that is provided to the input side of the power conversion circuit. The noise reduction unit is provided with: a core having a first core part and a second core part; a common-mode chalk coil having a first winding wire wound around the first core part and a second winding wire wound around the second coil part; and a smoothing capacitor that constitutes a low-pass filter circuit cooperatively with the common-mode chalk coil. The power conversion apparatus is further provided with a damping unit provided at a position intersecting the magnetic path of a magnetic flux leakage.