Active Common-Mode Filter Circuit for EMI Noise Suppression
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Solution Overview
Problem
Conventional methods for addressing electromagnetic interference (EMI) common-mode interference, such as passive filters, face challenges in balancing filtering performance with circuit costs and size, particularly in modern electronic devices where miniaturization and cost-effectiveness are crucial.
Innovation Solution
A filter apparatus incorporating a feedback active common-mode filter and a feed-forward active common-mode filter, both sharing a common-mode noise detection component, are sequentially connected between a device and an external power source to enhance filtering performance while reducing circuit costs through shared components and miniaturization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a passive common-mode filter is used to suppress EMI, then filtering performance is improved, but device size and cost increase
Solution Approach 1:
The patent replaces the traditional passive mechanical filter structure with an active filtering system using operational amplifiers and capacitors. The active filter uses electronic signal processing instead of passive electromagnetic components, achieving effective common-mode noise suppression while significantly reducing the physical size of the filter circuit.
Solution Approach 2:
The patent changes the filtering approach from passive component-based frequency selection to active feedback-based signal cancellation. By using operational amplifiers to generate anti-phase signals and feed them back through capacitors, the system dynamically cancels common-mode noise across a broad frequency range, improving filtering effectiveness while minimizing component size.
2Object-affected harmful factors
If a passive common-mode filter is used to suppress EMI, then filtering performance is improved, but circuit cost increases
Solution Approach 1:
The patent replaces expensive passive filter components (large inductors and capacitors) with more cost-effective active electronic components. The operational amplifier-based active filter uses standard electronic components that are cheaper and easier to manufacture, while achieving superior filtering performance through active signal processing.
Solution Approach 2:
The patent combines the filtering function with the existing power supply circuitry by integrating the active filter into the power input stage. The operational amplifiers and capacitors are strategically placed to utilize existing circuit nodes, reducing the need for separate filter components and lowering overall circuit cost.
3Object-affected harmful factors
If an active common-mode EMI filter is used, then filtering performance and size are improved, but it is difficult to balance filtering performance with circuit costs
Solution Approach 1:
The patent designs the active filter circuit to serve multiple functions: common-mode noise filtering, differential-mode noise suppression, and power input protection. The operational amplifiers and capacitors are configured to handle both common-mode and differential-mode interference, maximizing the utility of each component and reducing overall circuit complexity and cost.
Solution Approach 2:
The patent employs feedback mechanisms where the output of the operational amplifiers is fed back through capacitors to the input stage. This feedback loop dynamically adjusts the filtering action based on the detected noise levels, achieving adaptive noise cancellation that maintains high filtering performance across varying operating conditions without requiring complex additional circuitry.
Data Source
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AI summary
Embodiments of the present invention provide a filter apparatus and a power supply system, where the filter apparatus is connected between an external power source and a device, and includes a feedback active common-mode filter and a feed-forward active common-mode filter, the feedback active common-mode filter includes a common-mode noise detection component and a first filter circuit, and the feed-forward active common-mode filter includes the common-mode noise detection component and a second filter circuit, where the first filter circuit is connected between the common-mode noise detection component and the device, and performs feedback filtering on a first common-mode noise signal, to obtain a second common-mode noise signal; the common-mode noise detection component is connected between the first filter circuit and the second filter circuit, detects the second common-mode noise signal, and provides the second filter circuit with the second common-mode noise signal; and the second filter circuit is connected between the external power source and the common-mode noise detection component, and performs feed-forward filtering on the second common-mode noise signal. In the embodiments of the present invention, filtering performance for common-mode noise can be effectively improved to some degree.