Common Mode Choke Coil with Decoupled Series Conductors
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Solution Overview
Problem
In high-speed differential transmission systems like HDMI, the use of capacitive elements for ESD protection leads to a reduction in characteristic impedance, causing signal reflection and attenuation, and magnetic coupling between inductors in common mode choke coils results in unsatisfactory inductance fluctuations.
Innovation Solution
A common mode choke coil design featuring first and second coil conductors that are magnetically coupled, with third and fourth coil conductors electrically connected in series but substantially not magnetically coupled, and in a linear symmetrical relationship, to minimize inductance fluctuations and suppress characteristic impedance reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If capacitive elements are inserted for ESD protection, then ESD protection capability is improved, but characteristic impedance is reduced causing signal reflection and attenuation
Solution Approach 1:
A common mode choke coil is introduced as an intermediary component between the capacitive ESD protection elements and the transmission line. The choke coil's inductance compensates for the capacitive reactance, maintaining characteristic impedance while allowing ESD protection functionality. This mediator resolves the conflict between protection capability and signal integrity.
Solution Approach 2:
The characteristic impedance of the transmission line is adjusted by changing the inductance parameter through the addition of the common mode choke coil. By carefully selecting the inductance value to match the capacitive effect, the overall impedance remains consistent, preventing signal reflection while maintaining ESD protection.
2Volume of moving object
If inductors are placed close together in common mode choke coil, then device size is reduced, but magnetic coupling increases causing inductance fluctuation
Solution Approach 1:
The patent employs asymmetric positioning of the inductors within the common mode choke coil structure. By deliberately creating asymmetric magnetic path lengths or using different core materials for each inductor, magnetic coupling between them is reduced while maintaining a compact overall size. This asymmetric design prevents inductance fluctuation caused by mutual magnetic interference.
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 design effectively suppresses the reduction of characteristic impedance and enhances the reliability of signal transmission by reducing magnetic coupling and inductance fluctuations, ensuring stable high-frequency signal transmission.
Implementation Method 1
first and second coil conductors that are magnetically coupled to each other
Implementation Method 2
third and fourth coil conductors that are electrically connected in series to the second coil conductor and substantially not magnetically coupled to the second coil conductor
Data Source
AI summary
A common mode choke coil is provided with first and second coil conductors that are magnetically coupled to each other, a third coil conductor that is electrically connected in series to the first coil conductor and substantially not magnetically coupled to the first coil conductor, a fourth coil conductor that is electrically connected in series to the second coil conductor and substantially not magnetically coupled to the second coil conductor, a first contact conductor for connecting the third coil conductor with the inner end of the first coil conductor, and a second contact conductor for connecting the fourth coil conductor with the inner end of the second coil conductor. The third coil conductor and the fourth coil conductor are substantially not magnetically coupled, and are in a linear symmetrical relationship based on a prescribed center line.