GROUNDING DESIGN

GENERATION AND SUPPRESSION

EMV-FACHTAGUNG – 21. JANUAR 2015

GENERATION AND SUPPRESSION

OF COMMON MODE NOISE

Itaru Matsuda

Senior Staff EMC Engineering

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Yukio Kajita

Itaru Matsuda*

Kitagawa Industries Co., Ltd.http://www.kitagawa.de/

http://www.kitagawa-ind.com/

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Electronics life is filled with EM energy.

InterferenceMalfunction

Transmitter /Receptor

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Capacitive coupling

Heat-sink

Radiation of noise

High frequency RF current

(Floating metal)

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LSI

High speed signal

Common mode current is generated by mismatch of balancing which is

caused by different width of ground patterns on PC board.

The other example is between PCB trace and cable connected to the PCB.

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When transient current at switching flows into ground inductance, C.M. is caused.

dmG

dm

G ILjdt

dIL

cycle wave of signal is generated double

frequency noise wave.

Even times “f” noise wave will be generated.

Noise voltage fluctuations in a ground

plane sharing common-inductance return

from PCB.

2/1

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How to consider about

Grounding

At Higher Frequency

•It is not “0V”.

•It is influenced by disturbance

noise.

•It is not stabilized.

Common mode noise is mainly generated

by ground-related phenomena.

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Grounding Design with On-board contact

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Emission Level is improved

Large suppression is obtained

by multi point FG connection.

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Advantage

Suitable for surface mount process.

Small footprint for enhanced grounding.

Grounding placement near noise source.

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Without on board contact

With on board contact

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3 points GND

7 points GND

Connecting points to metal plate is varied.

On-board contact placed on PCB.

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Grounding Design

Current Driven Model & Return Path

Signal current

Return current

Separate return path results increasing GND inductance.

Return current

Return current

Signal current

Power plane

plane

GND plane

Increase GND inductance.

dt

diLL

dt

diLV MGG )(

Split aperture in GND plane Signal jumps over V-G planes

Pattern design with self and mutual inductance control is necessary.

Noise suppression by .

Reduce Increase

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Grounding Design

Multi point connection to Ground

It is necessary to make multi point grounding to GND plane.

Unbalanced GND potential is not accepted.

GND plane

Signal/GND plane

Signal/GND plane

Power/GND plane

To be enlarged ground area.

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Conducted emission from

power line is measured.

How to measure CE?

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Differential Mode Current ID)

Common Mode Current (IC)

)(50

)(50

DCN

DCL

IIV

IIV

Measurement system

Measuring total value of ID and IC

It is hard to separately observe DM current and CM current.

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Initial State

Power line: L,N,G

L+N+G--All lines are tuned around GRFC-13.

GRFC-13: KGS product

Initial level Initial level

Nothing changed. Why?

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LISN

Current Flow

EUT

DM current

CM current “1”

CM Current “2”

Insertion loss is effected against CM Current “2” only.

L

N

G

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Separately Measuring by Current Probe

CM Current 2 is observed. CM Current 1 is observed.

Both of DM and CM current are observed. CM Current “1” is observed.

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CM Current Measurement DM Current Measurement

Emission mode can be identified by Current Probe.

Current Probe Current ProbeCM Current

DM Current CM Current

DM Current

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EUTLISN

L

N

G

DM Current

CM Current “1”

Initial level Initial level

Initial level

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Recommendable Ferrite material is identified by disturbance frequency.

L N L N

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Materials

1

10

100

1000

0.01 0.1 1 10 100 1000

Imp

edan

ce (

)

Frequency (MHz)

Impedance vs Frequency

Suppression performance in Equipment

Initial level

Mg

1

10

100

1000

0.01 0.1 1 10 100 1000

Imp

edance

()

Frequency (MHz)

0.1

1

10

100

1000

0.01 0.1 1 10 100 1000

Imp

edan

ce (

)

Frequency (MHz)

Features

High impedance at lower frequency (kHz - 2 MHz)

'Cable guide'' contribute to workability when increasing

number of turns

RFCK2-M20 is designed to install by using screw

Applications

Inverter, Low frequency noise current from Motors

=> Air-conditioners, Washing machines, machine tools,

Medical equipment etc etc

Specification

AC-DCL.I.S.N

TRMH Low-cut High Ferrite

Present goods

TRM Low-cut Ferrite

GTR Soft ferrite

AC power cable(5T)

AWG14

Compressor cable(6T)

AWG16

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1. Grounding

It is measure to eliminate the noise source and

suppress the radiation.

2. Filtering

Suppression and Isolation of noise source

3. Shielding

Shielding barrier of noise

Front loading design

Engineering after

sample assembled

EMC technique to suppress noise

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Low-cut Core

Shielding Gasket Engineering

Support

Wire Mesh Gasket

Ferrite Clamp

Flat Cable Shield

On-board Clip

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Ferrite Clamp

MAGNEFILM

REMILESS

Shielding Gasket

MIC-HOLDER

LOSTOMER AG

On-board Clip

On-board Contact Cool Provide

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On-board Clamp

On-board Contact

On-board Plate

Cool Provide

REMILESS

SMARTPLY

MIC-DAMPER

On-board Clip MAGNEFILM

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Low cut Core

Ferrite Clamp

Shielding Gasket

Cable Shield

Cable Clamp

Dust Proof Bushing

MEFS

Click

Adjustable Clamp

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On-board Contact

Ferrite Clamp

On-board Terminal

MG Absorption Sheet

KG GEL

Fan Holder

Cool Provide

Re-use Clamp

Connector Clamp

• Automotive electronics

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Kitagawa Industries Co., Ltd.

http://www.kitagawa-ind.com/

Kitagawa GmbH

http://www.kitagawa.de/

Ihr KITAGAWA Vertragspartner für die Schweiz

VIELEN DANK FÜR IHRE AUFMERKSAMKEIT

AWAG Elektrotechnik AG

Sandbüelstrasse 2

CH-8604 Volketswil

info@awag.ch

www.awag.ch