Noise Filter Layout With Magnetic Coupling for Normal Mode Attenuation
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Solution Overview
Problem
Conventional noise filters fail to significantly enhance the attenuation characteristic for normal mode noise due to residual inductance in line-to-line capacitors, which limits the reduction of high-frequency noise.
Innovation Solution
The noise filter design includes two line-to-line capacitors with currents flowing in opposite directions, and parallel connection wires that are magnetically coupled, reducing the residual inductance of the capacitors and improving noise attenuation by increasing the inductance of the connection wires.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional noise filter configuration with two line-to-line capacitors is used, then magnetic coupling between capacitors is reduced, but residual inductance of capacitors cannot be reduced significantly
Solution Approach 1:
The patent introduces connection wires as an intermediary element between the two line-to-line capacitors. These wires are configured to generate magnetic fields that couple with the capacitors, acting as a mediator to transfer and cancel magnetic flux. This intermediary structure enables the reduction of residual inductance without altering the capacitors themselves, resolving the contradiction between maintaining magnetic coupling reduction and achieving inductance reduction.
Solution Approach 2:
The patent changes the physical parameters of the connection wires, specifically their length and arrangement, to optimize magnetic coupling effects. By adjusting these parameters, the magnetic fields generated by the wires are tuned to effectively cancel the residual inductance of the capacitors across a wide frequency range, achieving up to 8 dB improvement in attenuation characteristic.
2Object-affected harmful factors
If line-to-line capacitors are used to reduce normal mode noise, then magnetic coupling between capacitors is minimized, but attenuation characteristic cannot be significantly enhanced
Solution Approach 1:
The patent converts the harmful residual inductance effect into a beneficial cancellation mechanism. By introducing connection wires that generate opposing magnetic fields, the previously harmful magnetic coupling between capacitors is transformed into a useful flux cancellation effect. This converts the harmful residual inductance into a benefit, achieving enhanced noise attenuation without compromising the capacitor configuration.
3Device complexity
If conventional capacitor arrangement is used, then circuit simplicity is maintained, but noise attenuation performance is limited
Solution Approach 1:
The patent merges the function of noise attenuation with the existing capacitor structure by integrating connection wires into the filter circuit. Rather than adding separate inductance reduction components, the connection wires are combined with the capacitor arrangement, achieving both structural simplicity and enhanced performance. The wires are seamlessly integrated into the existing circuit layout, maintaining simplicity while improving attenuation by up to 8 dB.
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 configuration enhances the attenuation characteristic for normal mode noise by up to 8 dB across a wide frequency range, effectively reducing high-frequency noise interference.
Implementation Method 1
currents flowing through the first connection wire and the second connection wire are parallel to each other in the same direction. Thus, the present invention allows the connection wires and the line-to-line capacitors to be magnetically coupled together
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A noise filter (1) includes a first capacitor (16) and a second capacitor (17) which are two line-to-line capacitors. Currents flowing through the first capacitor (16) and the second capacitor (17) are in directions opposite to each other, and meanwhile, currents flowing through a first connection wire (12) and a second connection wire (15) are in the same direction and parallel to each other. Accordingly, magnetic coupling is caused between the connection wires and the line-to-line capacitors. Thus, the residual inductance of a line-to-line capacitor itself is reduced, whereby an attenuation characteristic for normal mode noise is further improved.