Common-Mode Filter with Planar Inductors and ESD Protection
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Solution Overview
Problem
Conventional common-mode filters rely on magnetic materials, which are difficult and expensive to integrate into semiconductor or isolating substrates, and lack electrostatic discharge (ESD) protection, limiting their application in miniaturized electronic circuits.
Innovation Solution
A common-mode filter design that eliminates magnetic materials by using positively coupled inductive elements and capacitive elements, including diodes for ESD protection, integrated in a planar winding structure with low series resistance to maintain signal integrity and miniaturization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If magnetic material is used in common-mode filter, then high inductance and high series impedance are achieved, but integration difficulty and cost increase
Solution Approach 1:
The patent extracts and eliminates the magnetic material from the common-mode filter structure, replacing it with planar inductive elements that achieve the same filtering function without requiring ferromagnetic layers, thus solving the integration difficulty while maintaining filtering performance
Solution Approach 2:
The patent substitutes the magnetic material-based inductive structure with a planar electromagnetic structure using deposited conductive layers, replacing the mechanical/magnetic system with an electrical field-based system that is compatible with semiconductor fabrication processes
2Reliability
If magnetic material is used in common-mode filter, then high inductance is achieved, but device size increases
Solution Approach 1:
The patent transitions from a three-dimensional magnetic core structure to a two-dimensional planar structure with spiral or meandering inductive elements, achieving high inductance through clever layout design in the planar domain rather than through vertical magnetic stacking, thus reducing overall device volume
Solution Approach 2:
The patent employs nested or interwoven trace patterns in the planar inductive elements where conductive paths are arranged in space-filling curves or interlaced patterns that maximize the effective inductance within a minimized footprint, allowing the inductive elements to be compactly nested within the filter structure
3Reliability
If conventional common-mode filter is used, then filtering function is provided, but ESD protection is lacking
Solution Approach 1:
The patent integrates multiple functions into the same filter structure: the planar inductive elements provide both common-mode filtering and ESD protection by serving dual roles as filter components and surge protection elements, eliminating the need for separate protection circuits and enabling integration in compact devices
Solution Approach 2:
The filter structure itself provides ESD protection through its inherent planar geometry and low-inductance ground connections, where the same conductive elements that form the filter also serve as ESD current paths, allowing the device to protect itself without additional external protection components
4Ease of manufacture
If planar winding structure is used, then integration is enabled, but series resistance increases
Solution Approach 1:
The patent uses composite conductive structures combining multiple metal layers with different properties (e.g., copper for low resistance, aluminum for planarity) in a stratified configuration, where the layered composite material approach reduces overall series resistance while maintaining planar geometry for integration compatibility
Solution Approach 2:
The patent divides the inductive path into multiple parallel segments or traces distributed across different metal layers, where each segment carries a portion of the current, effectively reducing the total series resistance through parallel conduction paths while maintaining the planar winding structure for integration
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
The solution effectively filters common-mode signals without magnetic materials, providing ESD protection and maintaining low series resistance, enabling integration in compact electronic devices while maintaining signal quality and bandwidth.
Implementation Method 1
inductances 31 and 33 are coupled by a magnetic material 35
Implementation Method 2
a first and a second positively coupled inductive elements; in series between a second input terminal and a second output terminal, a third and a fourth positively coupled inductive elements
Implementation Method 3
in series between each midpoint of said series connections of inductive elements and the ground, a capacitive element and a fifth inductive element
Data Source
AI summary
A common-mode filter including, in series between a first input terminal and a first output terminal, a first and a second positively coupled inductive elements; in series between a second input terminal and a second output terminal, a third and a fourth positively coupled inductive elements; and in series between each midpoint of said series connections of inductive elements and the ground, a capacitive element and a fifth inductive element.