Noise Filter with Current Loop for Induced Noise Cancellation
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Solution Overview
Problem
Conventional noise filters in electric power conversion devices can generate noise currents due to alternating magnetic fields, which are then transmitted to external devices, posing a challenge in preventing these noise currents from mixing with output currents.
Innovation Solution
A noise filter design featuring a housing casing made of metal, with two capacitors connected in a current loop configuration, where one capacitor's electrode is connected to the external terminal and the other to the housing casing, allowing induced noise currents to cancel each other out when an alternating magnetic field penetrates specific areas within the loop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a conventional noise filter with capacitor and conducting wires is used, then noise current removal function is provided, but induced noise current is generated due to AC magnetic field interaction
Solution Approach 1:
The current loop is divided into two distinct areas (first area and second area) that are separately exposed to the AC magnetic field. This segmentation allows independent control of the magnetic flux penetration in each area, enabling the induced noise currents to be balanced and canceled effectively.
Solution Approach 2:
The invention converts the harmful AC magnetic field interaction into a beneficial effect by deliberately designing the current loop structure so that the AC magnetic field penetrates both areas, inducing equal and opposite noise currents that cancel each other out. The harmful magnetic field interaction is transformed into a noise cancellation mechanism.
2Ease of manufacture
If the noise filter structure is simplified with fewer components, then manufacturing cost is reduced, but noise filtering effectiveness is compromised
Solution Approach 1:
The housing casing serves multiple functions: it provides structural support, acts as a conductor for the current loop, and serves as a mounting structure for the capacitors. The external terminal also functions as both a connection point and a conductor in the current loop. This multi-functionality reduces the need for additional components while maintaining noise filtering effectiveness.
3Object-affected harmful factors
If the current loop area is increased to improve noise cancellation, then the filtering performance is enhanced, but the device size increases
Solution Approach 1:
The invention optimizes the local quality of the current loop by strategically positioning the first and second areas within a compact space. The loop is configured to expose these areas to the AC magnetic field while maintaining a small overall footprint. The housing casing and external terminal are arranged to form an efficient current loop that achieves effective noise cancellation without requiring a large device size.
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 effectively prevents large induced noise currents from being transmitted to external terminals by ensuring the first and second induced noise currents flow in reverse directions, thereby canceling each other and reducing residual noise currents.
Implementation Method 1
a magnetic flux of an alternating magnetic field generated in a part of the electric power conversion circuit penetrates in the first area and the second area. A first induced noise current is induced in the current loop when the magnetic flux of the generated magnetic field penetrates in the first area.
Data Source
AI summary
A noise filter is assembled to an electric power conversion device and has a metal housing casing and two capacitors connected to an external terminal of the device through which an electric power conversion circuit is connected to an external device. The two capacitors, the housing casing and the external terminal make a current loop. A magnetic flux of an alternating magnetic field generated in a part of the electric power conversion circuit penetrates in a first area and a second area formed in the current loop. A first induced noise current is induced in the current loop when the magnetic flux of the generated magnetic field penetrates in the first area. A second induced noise current is induced in the current loop when the magnetic flux penetrates in the second area so that the first induced noise current flows in a reverse direction to the second induced noise current.