Capacitive Isolator With Inductive Ground Nodes

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Solution Overview

Problem

Capacitively coupled isolators face challenges in signal transmission due to parasitic ground capacitance, which leads to in-phase noise and electromagnetic interference, making it difficult to maintain proper signal transmission between input and output circuits.

Innovation Solution

Incorporating inductive elements between differential signal lines and the ground potential to suppress parasitic ground capacitance and reduce signal transmission loss, by configuring the inductive elements to be electrically connected to nodes between capacitive elements and the output side circuit, effectively creating an open circuit state for unwanted signals.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a capacitively coupled isolator is used to achieve electrical isolation between input and output circuits, then isolation effectiveness is improved, but parasitic ground capacitance causes in-phase noise and electromagnetic interference that degrades signal transmission quality

Engineering Contradiction:

Improveisolation effectivenessVSAvoidparasitic ground capacitance interference

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent introduces an inductive element as an intermediary component connected between the capacitive element and ground. This inductive element acts as a mediator that counteracts the parasitic ground capacitance effects, allowing the capacitive isolator to maintain its isolation effectiveness while reducing the harmful interference caused by parasitic capacitance.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent converts the harmful effect of parasitic ground capacitance into a beneficial effect by intentionally introducing an inductive element that creates a resonant circuit with the parasitic capacitance. This resonance effect at the operating frequency transforms the previously harmful parasitic capacitance into a useful component that enhances signal transmission while maintaining isolation.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Object-affected harmful factors

If inductive elements are added to suppress parasitic ground capacitance, then signal transmission quality is improved, but device complexity increases

Engineering Contradiction:

Improvesignal transmission qualityVSAvoidcircuit structure complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent merges the inductive element with the existing capacitive isolator structure, integrating multiple functions into a unified circuit configuration. The inductive element is positioned to work in conjunction with the capacitive elements, creating a compact arrangement that suppresses parasitic ground capacitance while maintaining the isolator's core functionality without requiring separate independent components.

Inventive Principle:

Principle #5Merging (Combining)

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 significantly reduces the influence of parasitic ground capacitance, improving signal transmission quality and reducing electromagnetic noise, thereby enhancing the effectiveness of signal isolation between the input and output circuits.

Implementation Method 1

Capacitively coupled isolators face challenges in signal transmission due to parasitic ground capacitance

Methodology Applied

Scientific EffectParasitic capacitance: Parasitic Capacitance

Implementation Method 2

Incorporating inductive elements between differential signal lines and the ground potential to suppress parasitic ground capacitance

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS11601108B2Isolator and communication system

Publication Date: 2023.03.07 KK TOSHIBA

AI summary

According to one embodiment, in an isolator, a first capacitive element is arranged on a first signal line. The first capacitive element has one end electrically connected to an input side circuit and having another end electrically connected to an output side circuit. A second capacitive element is arranged on a second signal line. The second capacitive element having one end electrically connected to the input side circuit and having another end electrically connected to the output side circuit. A first inductive element has one end electrically connected to a first node between the first capacitive element in the first signal line and the output side circuit. A second inductive element has one end electrically connected to a second node between the second capacitive element in the second signal line and the output side circuit.