Output-Noise Reduction Device Using Segmented LC Filter
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Solution Overview
Problem
Conventional output-noise reduction devices fail to sufficiently reduce noise generated by switching operations in electronic devices embedded in metal casings, as noise is transmitted through signal wiring and ground wiring due to electromagnetic coupling, circumventing the designed noise reduction path and reaching the output terminal.
Innovation Solution
An output-noise reduction device incorporating an LC filter with capacitive and inductive elements, where the electromagnetic coupling between the electronic device and capacitive elements is prevented, and the ground potential is stabilized to block conductive noise, using a metal casing with low impedance to prevent voltage fluctuations and radiation noise from reaching the output terminal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional noise filter with conducting bar is used, then the device structure is simple, but noise is transmitted through signal wiring and ground wiring due to electromagnetic coupling, circumventing the noise reduction path
Solution Approach 1:
The device is segmented into distinct functional modules: a first module containing capacitive elements for filtering high-frequency noise, and a second module containing inductive elements for filtering low-frequency noise. This segmentation allows each module to specialize in specific frequency ranges, improving overall noise reduction effectiveness while maintaining a manageable structural complexity through modular design.
Solution Approach 2:
The patent introduces a spatial dimension to noise reduction by arranging capacitive and inductive elements in different physical locations and orientations. The capacitive elements are positioned to intercept electromagnetic fields at specific points, while inductive elements are arranged to counteract magnetic coupling effects, creating a multi-dimensional noise reduction approach that addresses electromagnetic coupling from multiple directions.
2Reliability
If electromagnetic coupling is not prevented, then the device structure remains simple, but voltage fluctuations occur and noise reaches the output terminal
Solution Approach 1:
Capacitive elements serve as intermediaries between the signal path and ground, providing a low-impedance path for high-frequency noise to bypass the signal path. Inductive elements act as intermediaries to block magnetic coupling by introducing opposing magnetic fields. These intermediary elements effectively isolate different parts of the circuit from electromagnetic coupling without requiring complete shielding of the entire device.
Solution Approach 2:
The patent changes the electrical parameters of the circuit by introducing capacitive and inductive elements with specific impedance characteristics. The capacitive elements provide frequency-dependent impedance that decreases at higher frequencies, while inductive elements provide impedance that increases at higher frequencies. This parameter change creates a frequency-selective noise reduction effect that targets electromagnetic coupling at different frequency ranges.
3Reliability
If ground potential is not stabilized, then the device structure is simple, but conductive noise is transmitted through ground wiring
Solution Approach 1:
The patent creates equipotential regions by connecting multiple ground points through low-impedance paths using conductive elements and grounding structures. The capacitive and inductive elements are referenced to a common ground potential, ensuring that voltage fluctuations at different points in the circuit do not create potential differences that would drive conductive noise through ground wiring.
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 prevents electromagnetic coupling and voltage fluctuations, reducing noise in the output signal and enhancing the reliability of the noise reduction device in harsh environments like automobiles.
Implementation Method 1
electromagnetic coupling between the electronic device and at least part of the capacitive element mounted on the first mounting board is prevented
Implementation Method 2
an output-noise reduction device that reduces noise mixed in an output signal output from an electronic device
Implementation Method 3
a noise filter for removing the noise flowing in the conducting bar
Data Source
Figure 1
Figure 2
Figure 3(A)~3(B)
AI summary
An object is to provide an output-noise reduction device that can prevent noise from an electronic device accommodated in a metal casing from being transmitted due to electromagnetic coupling. An output voltage output from a switching power supply 5 is extracted to the outside through a conducting bar 11 having one end portion serving as a connection terminal connected to an output end of the switching power supply 5 and the other end portion serving as an output terminal VO. A magnetic body core 13 includes a through hole through which the conducting bar 11 is inserted. A chip capacitor 37 is mounted on a mounting board 17 and connects between the output terminal VO and ground potential GND. A section from the output terminal VO to at least part of the chip capacitor 37 mounted on the mounting board 17 is isolated from the electromagnetic coupling from the electronic device. Thus, the electromagnetic coupling from the switching power supply 5 is prevented. Thus, the electromagnetic coupling between a part of a capacitor C1 on a side of the output terminal VO and the switching power supply 5 is prevented, whereby noise is prevented from being transmitted to the output terminal VO.