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Lab power Eleltronics Lab.,HONG KONG University

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Course Overyiew

Electromagnetic interference (EMI) is an important issue for switching power supplyengincers. Switching Dower supply is a main contributor of Eivll in an electronicproduct. Many countries have regulations to ban electronic products l.vith high EMl.Al1 EiVIi problems must be solved beforc the product can be put to the market and thisoften becomes a bott le neck in the dcsign process.

EMi in switching power supply is often regarded as a difficult problem. There is alack of concept and understanding for switching power suppty EMI issues. Generaland convcntional concepts are not always applicable because of the specialenvironment in a switching power suppiy. Also EIvII components required often takeup space and increase the product cost. Ensineers often find it difficult to strike abaiance between EMI performance, cost and size of the product.

This course wili help you understand EMI problems in switching power supply. Youwill learn to solve the problem effectrvely wrthout using extravagant methods such asusing expensive hiter components. Very practical methods together wrrhcomprehensive theories are presented in thrs course.

Abottt the speakers

Franki N.K. Poon d&#ffi) started his career in Electronic Engineering in i985.After some experience in the industry he obtained a Degree in Elecffonic Engineeringin Ciry Universiry Hong Kong. Ile worked for ASTEC and Artesyn TechnologiesAsra Pacific Ltd on many switching power supply projects. He joined the PowerElectronics Laboratory in Hong Kong [-iniversity in 1999 and is now the TechnicalDirector of the Power Electronics Lab. His research interest includes electromagneticintert'erence, circuit topoiogres, PWM switches modeling, zero-voltage switchine,power f-actor correction and synchronous rectif-rcation. FIe is the inventor oiover 10US patents and a number of pending patents.

Bryan l t .H, Pong (/ f tEel jq$) received hrs BSc degree from the Universiry ofBinningham and his PhD ,tegrce tiom cambndge Unrversiry in the U.K. Attergraduation Dr. Pong spent a t'ew years in thc Eiectronrcs Industry. He worked iorNational Semiconductor Hong Kong and ,A.STEC International. Now he is anAssociate Prot'essor at the Hong Kong Universiry. He founded the Power ElectronicsLaboratory and is now leading a team to carry out research in switching powersupplies. His research interests include synchronous rectification, EMI issues, powerfactor correction, magnetic component design and soft switching. He has co-inventedmore than 10 US patents and a number of pendirlg patents..

Power.Lab HKU

1 Explanationof Electromagnetic Interferencejk (EMI) in Switching Power Supply

Speakers

Franki Poon, Bryan M.H. Pong

Preryred bv Ftanki Poon & Bnan Pong

EMI in Swilching Power Supply

PowereLabThe Power Electronics Lab., Hong Kong University

O copyr ight 2002

ww. ee e. hku. hUpo||er e l eclron i6 lob/

PowefLabHKu

t

I.!*|* 1 brief introduction to the POWef eLab

Our Mission : To advance switchinqpower converter tech noloqies

' To develop excellence in powerelectron ics tech no log ies

. To apply the technologies to productsand foster cooperation with industries

Contact Pemn : Dr, Bryan M.H, pongPower Electgnics Lab,, O€partrn€nt of €l€cbict & Elstronic Engineering,Hong Kong University, Pokfulam Road,Hong KongTel: (852) 2859 7099 Fax: (852) ZAS97O99 or 2559 8738€mail r mhp@e.hku,hk Web site t ww.#.hku.hvFnw_elxtonc_/ab/

Prepareti bv Franki Poon & Bruan PonsE'lll n Switchtng Power SuoDiv q\ew.lce.hku.hhurwet eiectronrcs lah/ l

Power.Lab HKtl

Ottr work in the Power e Lab

Hiqh Power l20WAC/DCadapter Platform

Half brick DCDCConverter Platform High current Converief

Platform ivs 2004

ACDC Convefter8atterv charger

Pladorm ivs 40A platform 12V 65W

Preporeu bv Franki Poon & Boan Pong

EMI in Stvirchinq Power Supply

4.5kVA Power AmpliFier

*vw. ee e. h k u - h lv po w e r _e I e c r r o n tcs-�i a b/

PowefLab ilKU

L!'hat :loLt are going to learn today. .

Easy - EMI Basics. What ancj iiow peopleiest your product.

Not so easy - General attitude cf an EMIengineer.

. Difficult - How EMI is Droduced.

. More difficult - How EMI comes and qoes.

ffi{:lr2 Ar \ . -eee.hku. tNDo\ r ' . r : t cc r ro rL . : ,dD/ J

I

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PoweFLab HKU

I=qlm Basic B locks

- |w

. Every EMI issue has the following 3basic blocks

ffi Ptepared hv F.anki Poon & Bnun Poaq

Ji* E.V/ in Swirchtnq Power Supply tww. ee e. h ku - h A powe r _e I e c t ron tcs.ml a b/

I'loise Sources

r--D+-r-

ts;-I-

+

i x aI

. Switchino voltaoe and ftirrent waveforms in aJ J ,

swrtcnrng power supply.1 - "no fe t t hv : "onxr zaon,_ t : lnan r , iq

EMI n Switchtng Power SuDoir' :n"w.eee.hku.hl4power 'tiectroncs iob/ 6

v@Ir'rAL{14"7

r++D"+w

100

0

r00Eridge

EMi in Switching Power Supply

Power"Lab HKIJ

It - - .-qlg WaveJbrm prodttces Jiequency spectnrm

r l&l lokHz iooMHz

. Continuous Flyback

10

/ ,/ : )l l 1t . :

1 ' : :

. Discont inuousFlyback

1 0 A 1

, /l_l L_Prepared hy Fronki Poon tl )ruan ?uq

[, l l ] in Switchinq Power Suoot, t .ww *e nku hiifpower tittrtrittt ,tD/

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Powerrlab l lKU

Effect of duQ q)cle

:r. Duty c/cle = 0.6

w\|.eee.hku.hly'power electronis lab/

Duty cycle = 0.2

Prepared bv Franki Poon & Bryan Pong

EMI in S\9itching Power Supply

'rfrt dvidt),oo

n i-r t,&.tl "t:l l l l ' � -

o l l l l

. 300ns rise and fall time

f i . ' - "nu.n, \ t F\nKt Paon & 3nun p,tny

IJ f .W tn j* t tcntnq I 'a*cr ;uca; ' . 'e\e\|.eee.hku.hkiu)\eer J/ectr!)htcs,ab/

IIIIIIIIIIIrIIIIIIIII

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tn-

PowercLabHKu

t

I

nls Snubber circuit reduces dv/dt* t *

tuh,\Wf G lA"fi)A

Prepored b.v Franki Poon & Brya Pong

EW in Switching Power Supply ne\9.eee.hku.hvpo\9er-electrcni6-lab/ ll

PowefLab HKU

I

I

I

I

It[otes on l{oise Sources

Voltage and current waveformsNoise sources in switching powe_r sup.ply haslittle effect beyond 200MHz Yg"Sbfrt ,Waveshape affect base band frequenciesRising and falling edges affect high frequencyspectrumDuty cycle has little efTect on the spectrum

H{!r??reparel hv Frcnh Poon & )n'un P.nq

E,lll in Switchtnq Power Suppiv ww eee h*u.hltoower :lcctronics ldb/

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, ^'NatLttt l"*|*, Coupling Paths

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Contact Coupling

.1 taur* l hv Franx t Pn"q & 3n n t , tn t

E , l l l i n Swtch ing Power Suoo iv

thl{W*w.'*w

PowereLahHKu

r Every EMI issue has the followingbasic blocks

Prepared b1' Ftanki Poon & Bean Pons

EMI in Switching Power Supply wweee.hku.hUpower_elecrrontulaht lJ

Basic Blocks

,6e\e cce hku hlvtN,wpr -lecrntnrc.; :ao,

Receiver B,rL

. Standard test equipment set up' Conducted Measurement set up. Radiated Measurement set up

t2+ E4g,%*d W-

Preparcd hy Frcnki Poon & Enan Pong

EW in Swilching Power Supply ww.eee.hku. hApower _electroniu _lab/ I 5

Power.Lab HKU

Electromagnetic Emission(Our Interest)'

at u] Pful fepdrcu .v r f lnx r ! ' tu ,n & 6AJn t 'on t

EMI in Swrtching Poqer SuDplv

Electromagnetic Immunity

EMI standards

,ww.eeehku.hbpower . : lec : rnn tcs- tb t l6

Power"Lab HKU

lil ?,1 *+t41 .(rft^*e'

t. inilr dnl nethollt , l nealtrehent oftd.ln uilelercnce chatoct.rft ict t)/ nilod ond Tv h.!Nd.a!t tutetw,r dnd I

dti lrctotcl.qrtnhent

Lthttt orl nciln'ds ol rn.diut.hen' itulb ut.rt ircnce.hdrocteiltt ic\ al 2l..tt i . 6oxt..percted onil lhenol

nptl ioilce.\r '.hot.eholJdnJ.\inii l tWtpo\as.rl.?ntchnltdndtinilorelz(tt i.oldrya.on6 !Latertrertsnta

Lihilt a^t n.tho& ofh.!ss,.d.rt oftilb 6t..l.t.,E..h..rct.tuncr ofinlotd.do, t.ch^otos.qrrya.rt.

LidB lir harilo,tc tilteht en'rsirn (<= I6A pet thai,)

Li^ilahon ot v' itdq. lhtcltotio, \ dnd l l ick r t n Io|' vohoa. .i l t pplv .tvst?6 I < - I 6/ p. t pha.. )

1

j i lqrc reiltund eaisna s&,.lailI

Genenc indusniol .6isson ilondolds

FCC tSB IJSA,Yotio,o! EMl Sb,erd

CISPR]2

/EN55022

Prepared bv Franki Poon & Bryu Pong

EMI in Swilching Power Supply ww. eee. h ku. hlu wwer pl ec | rcn t6 k tbi 1 7

Emission standards

Power.Lab HKU

(91 , ta)

Prepdred bv Fran|i Poon,l :lfron l>.nt

E,lll ln Switchinq Power Supor,'

Immuniv standards

i teto'ncc ietctlrto"tl i lhwtN Stdnloil.\ l

' t S t a ) t ) . 1 : , \ j 5 0 a 0 : - t d 1 ^ o n t d e t h o t \ , t n e o s i l . e n e n t n t t ^ a u n t b - . h o t . . t e i l s i l c . \ o t . r ! , l o n l i v r t @ d c o s t , e c e t , e , '

rnl n,\.a)ctote, euutDnenl

iEC6ltM)-1 2 ]iltxr,)eonc rtuilltce nnunilr !e\F.\61iilil) J l

iEC6 l0a0

:Ec6lti l i l)-r-r t le.n'.ul iult t,antteilt 1nnu,ilv e\l

E.\alat\),r I

iEc6i0oil-!'J Surt. xnnu"n tut

EN6l 00il-1-5

I EC6 I 0oa-1.6 innunt t! b . ontucle J ti (n,hoDcet is4rc.l bv til)o liequ.hcy fi.lls dhoe. 9 kHt

lEc6l0tnr-l 1 V,ltaE. Jip.t. thoil :"t.truptn'm onJ 6hog. vanotio,i 'n6u,tN tail,EN6tA0t ) -J - t I

8N50082 I Gen..t. t..tiJ.htbt tndu,ily tk "ldtd

E,\5lt)N: - i;eil.. ' . rru,trtal tdnntN \to,darl

'nvw eee. h ku. hll power -'4 ec rron rcs _i ab/

all

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Power"Lab HKU

Ivleasurement - Ltse what type of equipment 'J

Spectrum Analyzer

@ cheap

i O One is enough - 10kHz -1GHz

@ Less accurate

EMI Receiver

@ Expensive

Prepared by Franki Poon & Bruu Pong

EMI in Switching Power Supply

o rwo are needed - l8[Hl:tt#:t

@ More accurate

nvwlee.hku.hUpower _electronia -lab/ : 9

r\L ,

Powerlab HKU

Measurement Set Up - Conducted (< 30MHz)

Prcpared hv Fronxt P.on & Sn un Ponr

E,VI in Switchinq Pcwer Suooly

it** No Shield Room is Nceclcti rr

0.8m(CISPR)

Ground plane 2m x 2m(CISPR), 2.5m x 3m(FCC)

arw t:ee. nku. nidpo wer _.i ectft)n rcs.1t:rth/

Power"Lab HKu

Measurement Set Up - Radiated EMI(> 30MHz)

Measurement distance L = 3M or lOM

otrr

l m - 4 mto obtainMax.reading

To Re€eiveror Sp€cttumAnalyzerwithcortutionfador

Prepared hv Franki poon & BryM pon"

EMI in Switching power Supply w. eee. h ku. h Apow e r _e I ecrrcn i6 -l ah/

PowercLab HKu

i

i A: . I: l m l: *:

J " ' L

Boundary ofarea rto be free ofrellective objects

Max. antennadimension

Anechoig chamber rs Needed in practice!l

8 er.parpu i,v Frunxi p.t,n e Bnun pooq

V E,Vl in Suttchtng powlr japp11,'tww. eee. h ku-h lvpower jleclron rcs lab/

Power.LaO rrKU

Radiated Set Up - diagnosis

. Anechoic chamber fil led with ferrite absorbers toabsorb EM reflections

' Small TEM cell provides convenient way to diaqnoseEMi problem

w\|. eee. h ku. h klpower,e lecrron ru I aht

PowereLab uKu

fuIeasrtrement - Limit level

Can ;,tcu make anamplifier wh tch receivessignal from 150kl1z to1Gl-iz at 2A0uV srgnallevei ??

\b.4$

t ,< : r , t t t : t t , i r - ' J

ClSPR2l conducredemission linit

I v \ | . cee .hku.hVra \ r r r

PoweraLah HKU

Measurement - about errorv^k

According to "EMC for product Designers" - Tim Williams

RF meuurinq recei'er - +1- ).iciB (worse fitrspectrum analv:er)

I m p e d o n c c a i s m r r c h r . l d B

,4 nlennq /, ldB

Antenna cable +/- 2.5ciB

,4nechoic chamber +1- JdB

'""ifiiirllp-:nr.\ i,z)r''-'�dBe{(w ' ' '

,o,u, = L7 dB Iww. e e e. h ku. h U po|9e r -e I e c t ro n iu _l ab/

$A\Prepored by Franki Poon & Bmu Pong

EMI in Swilching Power Supply

'rv

/ , 2WM

b dhzu

Power"Lab HKU

I

I

r

Spectrum Analyzer is cheaper for inhouse pre-compliance test.Conducted measurement is rather simple.Radiated measurement is diff icult.Different test Laboratory will give youdifferent results.

tfl-r.t1 - L p d r 4 d \ " F r l n h P 1 " n . i 3 ^ t n ! ' ' n \

i . l l l tn Switching Ptwer Suoptt

luleasttrement - short summary

. *w eu nku a lupr twer ' ieer runns .aa

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n6-nZrf '

PowereLab HKU

Prcpare.l bv Franki Poon & Bryan pong

EMI in Switching Power Supplv nvw.eee.hku.hldpower_eiectoniq_lab/ )7

Mort I*portant Concept - LOG Ai t[ft

are in LOG scale,l ies in our mind that

Reading = 20Log(M"ot":nd )dBuv10-b

Can you imagine what a number wi l l becomewhen i t is d iv ided by 10-6, then take LOG, andf inal ly mult ip l ied by 20 ??

FI{_!,

PoweraLabHKu

Most Important Concept - LOG & Sum

500uV = 54 dBuV

1000uV = 60 dBuV

2000uV = 66 dBuV

500 uV + 1000 uV + 2000 uV = 3500 uV = 71 dBuVGeneric human intuitive comDarisonCompare linear result 3500 / 500 = 7 times

Compare LOG result 7US+ = 1.3 times

ffi ,-,oareahvF,unkipoon,i,"-"-what dogs i ';t ir:nes tell urs

'?

l?+ E '\ll Ln Swlchtnq Powcr ,lypply \| cee hku npy)||er etectonrcs tab/ )8

,NojAe r-l|*. Y4'/-&T-

PowefLab HKU

Most Important Concept - LOG & Subtract

3500uV = 71 dBuV

2000uV = 66 dBuV

1000uV = 60 dBuV

3500 uV - 2000 uV - 1000 uV = 500 uV = 54 dBuVGeneric human intuitive comparison tells us

Compare linear result 50.0 / 3500 = 0.143 times

o';;:,:;ffi o l*;p* :* \I- ?

{l} 6,,tZt i".S.trching Power Sr

Powel'Lab iIKU

P,cpared i t y F , nx t Pooa. l s^un Y,n \

Et l l l tn Swi tch ing Power Supotv a\!\.ccc.4ku.hlvpu|'cr !lcctronrca lah/

LOG Reading - an example

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PowercLabuKU

effect of the transformer

9 -fr'

MOSFET

PCB

Aux,

a

sr6 r rd r gd z rd zsd r rdFfrquency (Log scale)

- C|SPR?2 canductive class B Imit line- Oiginal Nois€ Lavel- Xfomer naise eliminatad

Prepared bv Frahki Poon & Bryu Pong

EMI in Switching Power Supply \w\9.eee.hku.hUpower _electronics _lab/ 3 I

Example - eliminate

Conclusion - Little effect

PowercLah HKU

effect of the I,IOSFET

l d ' l d . r d . : ' d z , s d r r dFBquency (Log scale)

-- C|SPR22 conductive class I limit line- Original Noise Level- MASF€T noise eliminated

, lF Example - eliminate

Conclusion - Very Little effect

'"6F€TPCB

Aux.

.g

u,l

rq

z-d

l . ! - i l . "eoar "d hv t . tnk i P ,x tn . i Baun ? . .n t

i * - , t .V t :n Jwt tchnq Pcwer Supptv .w (ce .hku ah Dowyt " lec r r ' tnus .ab ,

Power.LabHKu

effect of the PCB

srd ,.Ld srl z'6 z.s6 rrdFCquency (Loq scab)

- C|SPR22 conductive class B limit line- Original Noise Level-- PCB naisa eliminatad

Prepare<l by Franki Poon & Bryu Pong

EMI in Switching Power Supply ww. eee. h ku. hVpowe r _e I ect rc n i q _l a b/

Example - eliminate

Conclusion - No effect

PowercLab HKU

Example - eliminate the little and

Conclusion - Hopeless, stil l exceeds the

the very little

l im i t

ItrlrltI

Prepared hv Fnnki Poon & sflan ponq

[,lll u Switchtnq Power Suprti,,,

srd , .1d r sd rrd zcd rrdrequoncy (Log scate)

; C|SPR22 conductive ctass I timit tine- Onginal Noise Level

' Xformer & MOSFET noise eliminated

vrtw.eee.hku.h*/powert iecrmnrcslah/ _r l

LISN

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Powelrlab HKU

in a professional way ?

Prepare<l by Franki Poon & Bryan Pong

EW in Switching Power Supply ww. eee. h ku. h Apwer _e I ect rc n is _l ab/

Example already

So HoPtess

Power.LabHKu

Xformer

MOSFET

PC8

Aux.

s

trs9

l d ' l d u r d z , d t s dr@@tLq&*)

' C|SPR2? conouctw de$ I Id lhe| - OilEntt Mtse Levd

- Xlffier onlyMOSFET anly

- PCB onty

Prepared bv F,unn Paun & Sntn P na

EMI in Switchins Power Suppiv

minute.

LISN

'vrew tce nku.nkJdtwer 'l.crnntc\ 'Jh/ j6

tIll

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Power.Lab HKU

We're wrong fwice - eliminatethe No Effect

Preporey' by Fronki Poon & gryan Pong

EMI in Switching Power Supply

$ *l | | l lr li " i * I I l: t I' 1 I"liiliil'M[l!rin,,,

' l ' l l t l l i l i i ir r d ' r o , r , d

- C|SPR22 ctu&nw <- Ong,rdNoiseled- Aux. 6tY

w\|. ee e. h L\. h ld po\9 e r _e I ec ! ro n is

Power"Lab HKU

flantXformer

0I'4OSFET

ilPCBI

R i n n n I

e

PCB|l

J't(JJrtr |n&

XformerIl

R i nnn I" . ' Y '

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Xformer is importantPCB is important

Wrons three times ?

f f i P--oar"J w f , tnk; P,, tn Li d.on . \ )ai

r t : . t t t : n ; ^ r c h i n q P c w t r ; L D p r wwcee-nku.hAoower !lec!rontcs iab/

PoweFLabilKu

-tyyttilatp tfrl&

There is a dominant noise mechanismor path - Wrong!Some other noise mechanism can beignored as it shows no effect - Wrong!Yesterday EMI solution did not work intoday's problem - Wrong!

Prepared by Franki Poon & Bryan Pong

EMI in Switching Power Supply w. ee e. h Sr. h Upow e r _e I ec t ro n ics _l a b/

Wrong Concepts

Power.Lab HKU

r " You wil lyou haveproblem"

not see aelrminated

result untilthe LAST

ffir:!tPrepdred bv Frdnki Poon & Eoun Pony

EMI n Swtchinq Power Supptv

Peter Bardos

Right Concept

:vww.eee hku nivoower erectronrcs lobt

PowefLabHKu

I

4s Remember

r Two equal noise level add togetheronly make a 6 dB difference

Reading = 2lLog(Muot"nd * y"otured "^

u '-)dbuY

$Reading = (20 Lo g (yryry5 + 20 Log (z))dBuv

[ 1 0 - oI

Reading = (20 Log (ryT"!"d ) + 6) dBuV' 10-o

ffi PrepareJ bv Franki Poon & Bmu pong

Ql EW i, Snirching Power Suppty wu e e e. h ku. h Apone t -e I e ct ron i u -l ab/

PoweFLab HKU

l . - t ' l r 1-EL IaKe a break" l"x{-

' \ r

\ ; r i \ 1 , t r* i * ' , : l' 1 i i i . ; l t l i l i I l l l , r n t r n v t. ,,^, ".rv{r *{uuSLlllil ,

f i c - p a . * t r u . i , o n l i l a t , a i 3 r . - a ' , . 1

i ! r4 g.t l t : i l S* t tchnq Ptwtr . tanL. ' tw \9 .cee-hku.n tuoower l tec t ron t r lab / J2

Htlt \vww eee hlra-hUoower eiectronics lah/ .14

detail

Power.LabHKu

LISN - a little bit more

" " " ' u s N

5OuH

.T0",i l l ki l

50 Ohmrcelver

50 OhmrKeaver

'*'T'l itl

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_4

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Il - 'tl =Tt -Tl -Il =

Tl -Il a

t -

FFFI

Line Impedance Stabilization Network - ac Only

Prepared bv Franki Poon & Bryw Pong

EMI in Switching Power Supply w. eee. h ku. hUpower -e I ectrcnis -l a b/

Simple Mission -

5o a to Earth 5oo

Power.Lab HKU

Picking up the noise - LISN

PoweFLab HKU

to line noise

I n p u tL i n e l

To50Ohmreceiver

Termlnrted

by 50Ohm

Idif f

Differential modenoise

v

Esrth

q,

fu^ InPut

Prepared by Franki Pmn & Bryat Pong

EMI in Switching Power Supply wvw. e e e. h ku. h Upowe r _e I e c t r o n i u _l a bt'

LISN - detects

PowefLab HKU

*to earth noise

L i n e l

i

4LTo50O hnr€ceiver

Terminsted

by 500hm

l c o m l

Common mode noise

l> r "par .J 5 c -nh P " 'n * J r . r r r ) ' r c

E,VI in Swi tchnq : ' tqer Su7orv

- detects

*vw e ee. h ku. hidpower _c I ec tron tcs'�l u h/

T!TTTTITITTT!IITTllTTI

PowefLabHKU

Predicting noise to space- Absorption clampl l ove a lone the input c lb le

H l . r to rca h t F .anx t 1 . " ,n & 3^ .an ! . ,n t

l i4 r.t l l n Switthuq Power Suoort '"ww e*.hku.hUpower electn)nrcs lab/

PowercLabilKu

space - Antenna

ot " ' 8 l l

' : t r 1

7(E

300MHz (log scale)

Prepared by Franki Poon & gn-dn Pong

EtVl in Switching Power Supply w-eee. h ku.hApower el ect ron ie labt'

Picking up the noise

PowercLab rlKu

rime';ryins SttdAmolitude varyingFEglgn.y varying

It changed - After we havembasurio it r -:,ri3x EnAh {

Prepared bv Franki Poon & Bryan Pong

EMI in Switchinq Power Supoly ww. eee. h ku. h Upow er _e I e c r ron iu _l a b/

Nafure of EM Noise

PoweFLah HKU

Nature of EM noise-Worse, norrnal and good

P-gak measurement - the worse, measurethe peak noise within a period of t ime.Average measurement - the good,measure the averaged noise within a

H€t ,Nw. eee.hku- hApowet _eIectonrcs -lab/

oeriod of t ime

rnfiSqgg;.1n*k measurement - the normal,between peak and averagemeasurements. 4

, - ' " o u r - t t " v ' . t n k r . ' . , , 4 i , 1 r r n P , , a -

EL l l n Swt tch inq Power Suoo iv

Power.Lab ilKr

Noiseafterdetector

Peak result

Quasi-peakr€sult

Average result

4nb

Prepared bv Franki P@d &. |ry@ Pong

EMI in Switching Power Supply ww e e e. h ku. h Upawer _e I ec ! ron6 _l ab/ 51

Peak, Quasi-peak, average

Time

PowefLabHKu

Resoiut ionSandwrdth Amp

P:flk oa EnvelopeDeteclor

(}'{(h'0+

lF0$,040Sclcctine$unng

lrequencyX - r r i s

Simpl i f ied Peak EMI receiver

Prepared hv Franki Pnon & SNan Pong

E,lll in S*,tchinq Power Suppiv

Peak detector - simplified

"rww. c e e. h ku. hfu FD\| er _r I ec I r o n i c s,! o b/

PoweFLabHlKu

Quasi-peak detector - simplified

Mixer Resolul ion

Bandwidl.hQuoi-Peal

t

, t tA'{. 0 . 5 H 2

|\rerDetector

CI"0$"{}f

M{HDSclectmc6uringl'rcquency

X-uls

Preparc<l by Franki Poon & Bryan Pong

EMI in Switching Power Supply

Quoi-Peak EMI receiver

w. eee. h ku. hUpowe r _e I ec t ron ia _l a b/

PoweraLab HKU

y\otuqilRl

What happens if the noise occLtrrence time isless than the charge time ?

Prepared bv Fronkt Paon & gruon Pong

E,W in Switchnq Power Suopiy '

Quasi-peak constant

. \ww tep .hku .n fu pDwcr : lec t r , tnu t ,a i t i

Power.Lab ilKu

fv l ixcr Resolut ion envelop 0.5H2Bandwidth r{mP Detcctor LPF

Sq0@0+

MMSclcctmeaunng

lrcqucncy

X-rr ls

Prepared bv Fronki Poon & Bryan Pong

EMI in Switching Power Supplv ww. eee. h ku. h lt/ power _e I ect ro n i a -l ab/

Average detector - simplified

PoweraLab HKU

Dan't forget every detedor has a chargingtime constant.

Prepored bv Frunki i>oon & 8ruon Pong

E,l l l tn Switchng Ptwer Suooiv

constant

QP-letectar l 0 - l 5 1 k l l z t t 1 5 - . l q M l k j 0 - j ) o M H t 0 l - t c l l z

6dB handwdrh o.:kll: aill. l2qktlz l:1kllz

Chorget ime | , . l

Dischorge timc

ww eee. h Lz. hlv pawer r I ectron r cs _t ob/

Power"Lab ilKu

does a signal exist

Period for detection ata ceftain frequency

B WI = _ l' chsrge ' . tveep

r trop J lnt{rdl

tSo lc - -1oAFor conducted EMI rangeand sweep is ls

J = l l l u c' c h a t g e

' " ^ :7t { l4f t \L"A;A

ffi PreOare,J ty Fronk Poon & \Nn Pong

L;iA, EMI n Switching Power Supply ww. eee. h ku. h ltl powc r -c I e c t ro n | 6 -i db/

Detector - how

PoweFLabHKu

Detector - fast and slow sweep

Sweep time = 10 s

S w e e p t i m e = 1 s

Preporey' hv Fronki Poan & Saan P,)ng

EMI in Switchinq Power Suppit' M. e ee. h ku. h LJ g)we r -e I ec tr o n t 6 _i o b/

PowePLabHKu

Prepare<l by Franki Poon & Bdon Pong

EMI in Switching Power Suppllt ww. eee. h ku, h Upowe r _e I ec t ro n i q,l a bt

. LISN, spectrum/ receiver, antenna, absorption clampare introduced.Peak detector is used for screen display as it givesfastest response.

Quasi-peak and average are used in most standards.You can cheat the detector or display screen if thenoise pop out faster than the charge time.Don't be cheated by the screen if sweep time is toofast.

I

I

summary

PowefLabHKU

Any Short Question?

Prepored bv Franki Poon & Ennn i''tng

EMI in Switchinq Power Supplv

, , ' . , ' " , ] , t , t '

' . ^

i' iulr 'ri."l / ili {l1,.1l s0 ixj\t - , v v, . *

ffiv w|weee.nku.n lopowel_e lec tn , r rcs ldh / 60

Power'Lab lrKU

f ' . t I tInvisible coupling - capacitive

Jr%v* 1t5Og

Does a capacitive objed work like a capacitor in acircuit ?

Prepored bv Franki Poon & Brynn Pong

EMI in Switching Power Supplv w\9.eee.hku.hl</power electrcniq lob/

Power.Lab HKU

spectrumanalyzer

co

e r & . . . 1 r r r / t d z t ' dFqufrcy(Hz)

+ Simulatad result'' Measured rcsult

M ulu al Ca pac i tive Cou plinq

PrPporel hv Frcnn Pnon d Bruon P,nt

ELll n Sw,itchmg Power Suppiv

Capacitor is capacitor

.t\w cee hta.hk/po9|"r _zlcctn)nc\ _.,tb,

Powel€Lab HKU

I-qfry Capacitor of course is capacitor-

. The above experiment actually does not intendto prove a two plate structure is a capacitor.

r It proves two separate physical objects canhave effect very much like a simple capacitorcoupled together and can give accurate resulteven the two separate objects connected to amore complicated circuit.

. Don't forget a pow€r supply is a complicatedcircuit, with a lot of separate parts and traces.

-$ Prepared bv Franh Poon & Bnon Pong

# E.VI ' , Switching Power Supplv ww.eee.hku.hlvpower_electroniu -lab/ 6J

PowePLabHKu

Invisible coupling - inductrwNW

spectrum Do i pick upanalyzer SOmething

here ?

Prepurel bv F,onn t ,nn & Snon Puy

EMI in Swilchnq Power gupplv .61" lee hku ippu\rcr .lectronrts i,.til

Power.LabHKu

Mutual inductive coupling - transformer

o..l /->i ( . / \t \ r c m lv

M

r * z '

- " [ n , 7 ' ' . , t " lL*tM_trn"_,""0=%ltoo ihd

-hd I

Prepared hy Frmki Poon & Bryu Pong

EMI in Switching Power Supply ww.eee.hku.hUpower-electrcnis_lab/ 65

Power.Lab HKU

Prepar"d hv F.anki Poon & Boan Pong

EMI in Swilching Power Supplv ww. eee. h ku. h la power -el ec tron tcs _l ab/

Indttctive coupling - equivalent model

r|

Powertlab t{KU

tVutnal inductive coupling : transformer ?

Fqufficy(Hz)* Simulalad resultn' Measured result

R &&QhN,

Mutuat nductvecou,tins

Prepored hv Franki Poon & BryM Pong

EMI in Switching Power Supply w w. ee e. h ku. h Apo wer -e I ec t rc n i6 _l a b/

Powe-LabilKU

You don't see this You see this

+)" v{; ; . v < + ; +

"if-' * . Y A

Y A \ <

Preoaryd bv Fronki Poon & 8^,an Pt)nt

E,VI in Switching Power 5ror1,

EMI engineer

'av*' cee.hku. hk/power _electronrcs _ldb/

III

PowefLabHKU

Prepared hv Franki Poon & Bfraa Pong

EMI in Switching Power Supply w\| .eee.hku.hADowerelectroniqiab/ 69

Any two nodes/ two objects, two components,two traces ... etc/ has an invisible capacitanceand capacitive coupling effectAny two segments/ two loops, two traces, twopaths ...etc, produce an invisible transformerand have inductive coupling effect.is there any combination of capacitive-inductive effect?

g

Reminder

PowefLabHKu

Simple idea ofElectro-Mag neticwave propagation.

H Prepare.l ov Franki Paon ,j. Bddn ltt)ag

EMI in Switchinq Power Suopiv

C ap ac it iv e - I nd'u c tiv e ffi c t

.vww rce hku.nltpower rlectrontcs tbt

PoweFLab HKU

Capacitive couplirg - trace to trace

sayCt-z = 0.lpf

Vst = 300V

Cu,,ois blocked byInput circuit & Bridge

Prepored by Franki Poon & Bryan Pong

EMI in Switching Power Supply ww.eee.hku.hUpower_electrcniq_[ab/ 7l

usN

Line

Inputdrcuit&Bridge

i** 6. . . . . . . . . . . . . . !

r l i] J ;) _

Un€ 2

Powe.LabHKu

Line 7 ,,Cr., As

Ct-z = 0'1Pf

Vst = 300V

At 150kHz

VrtsN= 1400uV

EN55022 B limit at 150kHz is630uV

500.a(\

500Line 2

V,,

v*n

x 300

Afr€odyercooh ffiiN hcdne d0.1d

Capacitive coupling - trace to trace

fr Prepdre.l bv fuanki Poon & Boon Pong

Ql E.VI in S*itchinq Power Supplv \ww eee.hku. hvNver electraner !db/

Power.Lab HKU

L I

IN

ryI

Prepare<l hy Franki Poon & Brya Pong

EMI in Switching Power Supply

C,

Itu

wv. e e e h ku. h ll po|9 e r _e I ec t rcn tu -l a bt 73

Capacitive coupling

Power.LabHKu

Capacitive coupling - which is bigger

L t

Itury

I

Iffi

CI <t Cz

P.epanl hv F.onn Pn,'n ti Bddn P1n\

EMI in Swtchinq Power Supply

Imagine C, approximate as thesum of all the capacitors

tavweee.hku.hUpower_electroniu_lab/ 71

itive coLtpling - trace to ground

say

C, = 0'l7f

i Vst = 300V

; - C. has a considerabie length+

'' between the plates but the4 surface on eanh is very large

Prepored by Franki Poon & Bryan Pong

EMI in Switching Power Supply ww. e e e. h ku. h Apowe r _c I ec I ro n i 6 _[ a b/

Capacitive coupling - trace to ground

/,.,r, 5 0 f )5 0 o

Assume

C, = o.l?f

Vst = 300V

At 150kHz

Vrtsr,t= 700uVEN55022 B limit at 150kHz is630uV

ffitlt

"Hxffied limit again IPrcporeu hv Franki Poon & Bnan Pong

Elvll in Switching Power Suppl.v ,nv*.eee.hku.hlt/power elqtronics tltb/ ;6

HVHF circuits

Hish 4Voltage

(

HisnFrequency

Preparel hv Franki Poon & 9nn Pong

EMI in Switching Power Supply ww.eee.hku.hupower_electrcnis _lab/ 77

PowefLab HKU

HVHF circuits - reduce to a sizeAs Small As Possible ASAP

Htlt

Prepared bv Frohki Poon & 9ruan Pong

E,lll in Swtching Power Supplv

RIGHT Wrodg RIGHT

.qvu cee hit.hlvmwer -:tecrronrcr _;ah. -R

PoweFLabHKu

Capacitive coupl-ing- - PCB trace rule t?l\'

\1(

- H I' l

i*f, t f"vq6N*--- H T' | q

tlrGood - small trace area, Bad - large trace area, asymmetrical.not enough separation and long

. connection wire.ljlnnelgcal, goodseparation

g Prepared bv Franki Poon & Brym Pong

EMI in Switching Power Supply wit e e h k u. hk/ po w e r -e I ec I ro n | 6 _l ab/

PowereLabilKU

trr'rtY"Inductive coupling - trace to trace

Although the loop has loW voltage, it generatesother kind of noise.

Prepared hv Franki I'oDn d Bdan Pong

EMI n Switching Power Suoplv ww.cee hku.hlt/power ..lectrontcs idb/ ,90

Powe,.Lab HKU

Inductive coupling - trace to trace induction

Prepared bv Franki P@n & Bry@ Pong

EMI in Switching Power Supply

say

L, = lnH

I'= lA @ 150kHz

V, r4= I ' 2 t f L .

V,ro = 940 uV

C, gives a lowimpedance path for theinduced current to flow

ww.eee.hku.hApower-electrcniq-laA 8l

PoweFLab HKt)

Inductive coupling - trace to trace result

V

say

Cx = 0'1uF

At 150kHz

VtrsN= 460uV

EN55022 B limit at 150kHz is630uV

l lrr.,r, = l--L, lxeaouv

1 5 0 + 5 0 + iI 2dic., I Verydoseto limiU

50C]

5 0 o

c

r\

H Prepak.l hv F,unki Poon & Bruan Plng

fif, C,Ut tn Switchinq Power Supp|v Bew.cee.hku.hlcoo\9er tlectrontc:,ub/

Power.Lah ilKu

Prepared bv Franki Poon & Brym Pong

EMI in Switching Power Supply wv eee. h ku. h Apowe r _e t ec trcn iq -i a b/

Inductive coupling - the trace itself

. Self inductance

PowefLab uKu

' '.-DorPd bv Frantu Poon & Bman p,ng

E,lll in Swtching Power Supplv

Let say

L. = 10nH

I'= 1A @ 150kHz

Vra= I ' 2 r fLs

Vra = 9400 uV

8N55022 B limit at 150kHz is' 630uV

ls it honible ?wv cce. h ku. n H Daa { _e I ectron rs _. ab,

Inductive coupling - trace induced voltage

Ls

c.Y

Ls

Power.Lab I|KU

Good - small loop area, good separationbefween loops, node terminated atcapacitor terminals

Bad - large loop area, short separationbetween loops, nodes are not terminatedat capacitor terminals

Prepared hy Franki Poon & Boan Pong

EMI in Switching Power Supply ww.ee4 hku,hHpower _electroniq -lab/ I5

Power"Lab ilKU

Tvpical copacitor and inductor parametervalltes

C = 0.085A/d pf t = 0.002/(/n(21/r)-0.75) uH Lm = 0.C02/(/n(2//D)-1+D/) uH

"^ry,i{1,tt5cm

J--. - LL I " " ' 1nn4

t lcm

Jr-

fr6=0.0885pf Lawsts=5.8nH Lfrawgts =15nH

f f i , ' . ,o"reu ou f ,ankr Poun & Bnun i , . ,nc

Ek t . \ l t tn Swttchinq Power jupph, tuw uee h tu nbp, twer : tec tn )nrc - dD/

I

PowercLab HKU

I-qh Short conclusion-

Prepared hy Frcnki Poon & Bryan pong

EMI in Switching Power Supply

Very small capacitor may cause seriouscapacitive coupling effectVery small inductor may cause seriousinductive coupling effect, either mutual orself inductive coupling.Very small pieces of object may causedevastating magnitude of capacitance orinductance.

www. eee. hku. hUpower _elcctronix _lobl t7

Power"Lab HKU

I

* nny Short euestion?-

i t l to " '&" " i , " ' '

i ' + , ' , . ;

i 1L't^l -^\, i JU] i ' , , . r ' . ^ i ' , t l * i

i,rSii ilj diiii0tiJi

f f i Prypdred hv F,uxt p. \ ,n e J^dn . , .nt

V t .Vtt n 5*i lching I 'ower jupplr*1r\'cee.nku.hvpo\ver-etectronrc-t_!oh/ Xg

Polver.Lab HKU

An obvious noise source - input ripple cltrrent

L3

c2

l

c,' l!

_Fr

.,\ {w)-f well known

\ equrvarence

L3 RB

I,,

i ----

: _ :' L ISN 1" " ' . " . . ' . . . ' . ' . . '

Prepared bv Franki Poon & Bryan Pong

EMI in Switching Power Supplv ww. e e e. h ku. h Upower -e I ec t ron i q _l o b/

ll

i

1--rJf= c , " c B :

(k ' (

l R . . :

If" ,-

t a' 1 . ' l I

l o , \1-

Powe.LabHKu

Input ripple current - simulation

Don't be scared bycomplicated circuit.You don't need tocalculate for theanswer.You ONLY need tosimulate it's result.SPICE, Maths o f t w a r e . . . e t c m a yhelo

! c )

ffi Prepareu hv Fronkt Po,)n & Bryan P,,n!

6b E.ul n Swilchinq Power Supptv ww eee.hiu hHpower -eIectrontc.r -,obt

Power'Lab ltKU

Input ripple current - Qpical resttlt

a

ftr-^, = 0.5Afrr-**= 0,8At,=50 nsIFSO nst * = 2 u sT = 6 , 6 u s

r . r d r . , e r . r d r , dFrcquancy (Lq *al6)

- C|SPR2? conductive class B limit line-- VLISN nolse /svs/

Prepared bv Ftanki Poon & Bryan Pong

EMI in Swilching Power Supply ww eee h ku. hUpower _e I ecrroniu _! abi

200 uH 0,5

O.47 ut

5 n H

0.05

Power"Lab HKU

ideal C ,

L l

20O uH 0.5

3

Irr-,n, = 0'5AIrr-oo, = 0'8Atr=5&nstf=50 ns

r . r d r ' r d ' r d r r dFEquency (Log *ale)

-- C|SPR2? conductivg class I fimit line* YLiSNnoAslev€i

i'repored hv Franii Foon & Enoa Pong

liMl in Swilchinq Power Supoiv

Input ripple current

O.47 uf

5 n H

0.05

lww. eee. h ku. h L, power -e ! ec rro n t cs _ obt

PowercLab HKU

fr.-11 = 0.5AItt-r.., = 0'8Atr=50 nstf=50 ns

r . rd r rd r . rdFrcquenc/ (Lq &ale)

ClSPR22 conductive class B limit lineVLISN ,oEa /€y€l

Prepared hv Fronki Poon & Brvu Pong

EMI in Switching Power Supply ww. e ee. h ku. h Hpo wel -e I ec! ro n i 6 -l a b/

Input ripple current -ideal

200 uH 0.5

Power.LabHKu

\ l ) 'hf '?rfr

n?rW*"

I.r_,n, = 0.5AIrr-, = o'8Atr=S0 nstf=s0 ns

r r d r . r d . d r . r dF6q@ncy (Lq *ale)

- C|SPR22 conductive class I limit line....._ VLISN rols€ /€vel

Input ripple current - ideal L,

O.47 uf

5 n H 2 0 n H

0.0s

fi P,eoored hv Frankt Poon & 7ruan Ponq

V EMI rn S\9ilching Power Suppiv ww.cee.hku.hHpower clectrontc\ iab/

, frh*)

Powe,.Lab HKv

C,, C,

L, less rms currentC2 2oo uH o.s C t

Not much difference

f51-16 = 0'5AIrr.-* = 0.8Atr=so nstf=50 ns

r r d r . r d r . r dFdquoncy (Lq *aE)

C|SPR2Z conductive class I limit lineYLISN no6e /eyel

ffi Preparctl hv Fronti P@n & Boan Pong

$ tW in Snitching Power Supply ww. e e e. h ku. h Apow er -e I ectrcn iu -lab/

Input ripple current - swzp

100 uf

2 0 n H 5 n H

0.5

Power<LabHKu

c2 200 uH 0.5

var"-,

Irr-,n, = o'5A

\.-t = 0'8Atr=5Otrstf=so ns

t t 0 r . r d t . t dFoquency (Loq wlel

C|SPR2? conductiva class I limit linaYLISN nols€ /€vel

Input ripple'current - ideul C,.again

'fi P.eparel hv Franki Poon & ENon Prng

fi E.VI 'n S*ttchinq Power Supplv avw. cee. h ku. h lt/ power _c I ec Fon | 6 _l d b/

IIIIIItTrITTttTtIIItt

PowefLabHKu

Input ripple current - ideal C, again

C2 zooun o.s Ct 4*W* ' -

Is1-6 = 0'5Arr.--., = 0'8Atr=50 nstf=50 ns

' ' ' d - t ' 0 . . , . ' d r r dFrcquency {Loq wte)

- C|SPR22 conduclive class E limit line.* VllsNnoisa /evel

Prepared hv Franki Poon & BryM Pong

EMI in Switching Power Supply ww. eee. h ku. h lt powe r _e I ecto n ta -l a b/ 97

PowefLahHKu

Prepared bv Franki Poon & Bnan Pong

EMI n Swtchinq Power Supplv ww ue.hku hllpower _(iectront6 -lab/

Input ripple current - short summary

Realistic equivalent circuit has difference withideal elements.Equivalent series resistance of a capacitorcontribute to low frequenry EMI.Equivalent series inductance of a capacitorcontribute to high frequency EMI.Perfect the components with largest value isvery effective. E.g. 100 uf

IIIhltFThFh

FIl-

FF

PowePLab trKU

L3

c2:

r f

I-{E

LISN

Add one morestage ?

Wait aminute I

Prepare<l bv Franhi Poon & Bry@ Podg

EMI in Switching Power Supply w. eee. h ku. h Apowe r _e I ec t ro n r u _l abt

Inptrt ripple current - two stage design

c5 ,C , c1

LISN

Powet LabHKU

There is a CommonMode Choke (CMC)

Ffl{:!t

Make use ofit 's leakageinductance !

Prepared hv Franki Poon & Eoan Pong

EMI in Swtching Power Suppll'

Input ripple current - make use of leakage

' -r anvwav.

dqffiiw$-

)w.eee hku hApower _electrunics _lob/

Power.LabHKv

50 uH 0.5 Z0O uH 0.5

vrr*-t

5lIrr-, = o'8Atr=50 nstf=50 ns

Prepare<l hv Franki Poon ,9. Bryu Pong

EMI in Switching Power Supply ww.eee.hku.hVwwer electroniu lab/

l0.1 u f -

(5 n H )

o.osi

fLr.PfryI Jtoo "t

\ z o " n 5 n H

i l'''

p.+z ut

t at /( l

I \ J

i o.ou\

,.\

I-/= Q ,

PoweFLabHKu

S

o

r . r d r . r d r . r d r ' r dF@qu.ncy (Log scaL)

'-- CISPR22 conductiva class B limit line.* VllsNnoise/€val

Single Stage Filter

Prepored he Frcnki Poon ,9 Btuan Pong

EMI in Switchtng Power Supplv

r . rd r . rd r ' rd r . rdFrequency (Log scale)

-"- CISPR22 conductive class I limit line* YtlSN noise with P & CM filter

Two Stage Filter

Input ripple current - two stage result

*vw. eee. h ku. hl<,/pover -el ectn n cs _l db/

Power"Lab HKU

Input ripple current - common trick

r . r d _ r . r d : . . t i . l , dFrequency (Log sca/eJ 1 1 0

fs

r . r d r . r d r . r dFrequency (Log scale)

C(SPR?? conduc(ive c{ass B (imit iineVLISN nolse with P & CM filter

= 130kHz, 30 dB marginr - l - .b k-'YA'LY1,j.9--\

ClSPR22 conductive class B limit tine* VL)SN noise with P & CM filter'

fs = 150kHz, B dB marginPrepared hv Franki Poon & Bryan Pong

E,VI in Switching Power Supply w\9. e e e. h ku. h llpow e r _e I e c t ro n i cs -l a b/

.-_+_iJ.]Iii

i l

PowefLab HKU

Disappears

Hf..{'

Beyond conduction l ime t.* Tcon

Pr,.odred iv Fl1nki Poon & Soan Ponq

E.\l! ;n Switching !)ower Suopiv

During ccnduction time t=Tcon

avweee.hku.n i lpower : le l r . i l t c : i , , th / 104

Input ripple curcent -

rtTI

Power.Lab HKU

f

fsonllfroo rr ;i z o n x

s n x (

I o.s

p.+z urf , -

; ( Jlo.oJ-

iL

average result

Assuming conductiont i m e T c o n = 3 m s

vrrn s

I / _ f /r LIS,Y _peak - ' LISN _dc

l,/ - t/' LIS,Y _quasi-peak - ' LIS,Y _dc

r / _ L /' L |SN , t ve raqe - '

. . ^ . , , 2TconLlJt \ Llc --

Tlin"

Prepared bv Franki Poon & Boan Pong

EMI in Swilching Power Supply

r ' r d t t 0 r ' r d r . r dF@quency (Log scalo)

- C\SPR2? conductive class B limit line- VLISN noiso of DC supplyI a'< Averaged natse with ac supply

Voltaga picked up at LISN with P filter

ww. eee. h k u. h lr/ pow e r -e I ec r ro n ic s -l a b/

Input ripple current -

Power.Lab HKU

firc"T-T-] ftr-_-&tu_ts

Beyond conduction time 0<t<;rand t * Tcon

-_/n_-,

1 I ) nT T J ruZI l ' E

Beyond conduction time ;r<t<2;rand t * Tcon

Durinq conduction time 0<t<n

and t=Tcon

-

't'

Durino conduction time n<t<ZnApply to all and tlrconanalysis !!

:av\| eee.hku. hvpo\eer .-!i ectronct , db/ 1 06

IIrltrlt-ItI!TThh ilvt l{anr\

,rh

POweFLabHKu

Input ripple cltrfvrtt - stabiti4t

&*'t

fu++ *Y'/'4

As input of converter is apower source Pin.Approximate the differentialEqn.d ' r r , . l R , , p i n f dv . v . v i n

t ,2 - i , ----1;

d t - | L , v r , "C, ) d t L ,C, L rC,

Keep first order coefficient > 0t . - \

EI{!2

. big C, is good

. big Rfi is goodr smdll Vin is badr ldl'$€ L3 lS DaO

Preparel b.v Fran|i Potn & Bnan Ptng

EMI in Switching Power Supplv

lE t[ R^ - pin

.;: iht' u,:,{ \

ww.eee.hku.hUpower-electroniq_lab/ 107

POWE-LAi HKU

IL""Eb Input Jilter - stability issue

Vin = Vcr approximately

R,. PiN

14 ,rrt C,

R L 3 > 1 0 r ) ! !

Usual ly windingRL3 = 0.2 O

'r\ oqF!'

vrhk

resistance

Evew convefier should oscillate I I But . . .J

f i i ' - 'ooreu hv Fnnn Poon & Snun P..ns

tfal E.Vl :n 5'vtrchnq Pnwer Supolt ww. cee. h ku. hfu M\9er i ec tron rcs lob/

1OO uH R., = ?

;

*

ttII!T

/t-

Power.LabHKu

I| ' ^ 1-ql* Input filter - why usually stable ?

-

r Because skin effect increases thewinding resistance - WRONG

r Because proximity effect increasesthe winding resistance - WRONG

. Because parasitic capacitor inhibitsthe oscil lation - WRONG

. Because the inductor is no longer aninductor - Meaningless

Prepmd bv Franki Poon & Bryan Pong

EMI in Switching Power Supply ww.eee.hku.hldpower-electrcnis-lab/ 109

M 4?y

Powet LabHKU

I"qtt Input filter - what ac inductor is

tu{DResistor reflectingcore losses

Resistor reflecting Resistol reflecting

.ikin / proximity dc winding losseslos3es

Frequency Frequencydep€ndent dependent

/),/ ./</w,.-DOMINANT !

Depend onFrequency &winding structuf

/

{lr*rN'''* l

Wire slze

w#ofi

Prcprett hv f.onn Poon ,l 9ruun P,'ns

ft Ett l in S*,tchrnq Power Supptv 'ww. e ee. h ku. h l</ po w er,e ! ec t ron ic s,i ob/ i l0

Powertlab HKU

SSUe

cw:;i:*Every engineer know core losses is significant, don,tignore the ac resistor reflecting core losses.

Prepared hv Franki Poon & Bwan pong

EMI in Switching Power Supply ww eee. hku. h lv power jt ectrcn rcr _iab/

Input Jilter - core losses

Power'Lab ltKU

L A lqk Input Jilter - why usually stable ? again

. Eecause core losses of the filtering inductorprovide extra resistance - RIGHT.

. Because the higher the inductance, the higherthe core losses resistance - RIGHT.

' Because the capacitor C, is usually bigger thanthe example - RIGHT.

. Because the oscillating frequency may fall out ofregulating region of the convefter, and becomesa circuit with positive resistance - MAy BE.

f i . ' *rarLt r f , , tah ?,atn & Jruon r ,n,1

V S, l l t tn Jauchrnq i .cq,r Suoptt . '.*'' &e hku.hlau)vcr !l4trtrnrL.\ ,db/

tIIIttIr�|TIIIIIIITtITI

Power.LaO trKU

II-els Input filter : Input magnetic receiver

:r-td"

. Recall the idea of inductive coupling and mix itwith the filter.

lt I I l t t lMasnet ic l I I If i e l d L - j i l

L4-_

Magnetic Noisevoltage

, 4 \\,/vu pi"k up

Many loops to pick upnoise field

Prepared bv Franki Pmn & Bryu Pong

EMI in Switching Power Suppty ww. eee. h ku. h Apower -e I ec ton i6 _l a b/

PoweFLab uKu

I| ' ^ 1

%l# Input Jilter - Input electric receiver*ts*

. Recall the idea of capacitive coupling and mix itwith the filter.

I I l l , , "o , . , . r iera i IV t + r - r - , -& _j/-\A_Lu Et -'--v t r + *

Noisevoltage

H(!tPn,porel rv Franki Poon & qruan Pcng

E.l l l inSwrchinq Power Suoplv

Vt ot* uo

.tuw. e e e. h ku. h l</ pow e r _e l ec rr o n ics -i o h/

I

PoweFLab ilKu

I

I-qls Input filter - summary-

. Leakage inductance can be made used forripple current f i l tering.

. Choose low ESR for big capacitor.

. Conduction angle or boost PFC yield loweraverage value than seen on screen.

r Input filtering circuit is also a receivercircuit.

' Core losses resistor is introduced

Prepared hv Franki Poon & Bnan Pong

EMI in Swttching Power Supply ww.eee.hku.hl</power electroniu lab/ ltj

Power.LabHKu

Invisible path - drain to earth capacitor

Simplified circuit showingdrain to earth capacitorcausing invisible currentflow

Prcpared hv Fmnh Poon tl 3r,on i' ,tg

EMI in Swtchinq Pc*er :iuooit,

Equivalent circuit usingequivalent input resistance

. and equivalent voltagesource

'w\9 lee.hku hllpower elecioncs :Ltb/ I 16

t

0*hATQ

Power'Lab ltKU

Drain to earth capacitor - equivalent model

Inputcapacitoris large

Conductionperiod only

Input l inesareparalleled

P'eparcJ hv Franh Poon & Bruan pony

E,Vl in Switching Power Supply ww. eee. h ku. h Upo'9c | _clectronrs ldb/

POWEFLAbIIKU

Drain to earth capacitor - how large?

| | .AlusNt---{ : Frl _ t \ - / l

I | 0.31ef

I T

Let the total surfacearea attach to the drainis equal to a spherewith lcmr surface area.

Equivalent radius r

r= 0.28cm

As the self capacitanceof a sphere of rcm

Csph",c=4rt.0885rpf

The equivalent drainself capacitance is

Cdr"in = O.37 pf

f f i : ' . r" ,"u 1' , Pdnkr PiDn d 3non p,ns

Qp) t-,llt tn S*rtchug Power Supprv \Nw.eee.hku.hupower elecrrontu loht

Power.Lab HKU

Drain to earth copacitor - simltlation

Vpeak =400 V

T r = 5 0 n s

T f = 5 0 n s

P w = 2 u s

Per = 6.6 us

Preparel hv Franh Poon & Brum Pong

EMI in Switching Power Supply ww. e e e. h ku. h Apower -e I ec t r on ics _l a b/

3.0uV200KHz 400KHE00KHz 2.oMHr.oMHr.oMtlt lftoMHz' r V l R s : 1 )

Power.Lab HKU

Filtering - doesn't work ?

What's wrong? It mustbe the CMC straycapacitor.

0.31pf

25 uH

2 5 n

Prepared hv Franki Poon & Brvan Pong

El,ll in Swttching Power Supolv

T r = 5 0 n s

T f = 5 0 n s

P w = 2 u s

Ptr = 6.6 us

-Lvu ee. n ku. nUpowe | _( I c c I r,,n i..\ _: ahl l : 0

PoweFLabHKU

What's wrong? Bewareof the LISN impedance

25 uH

25f i

Prepored hv Franki Poon & Bd@ pong

EMI in Switching Power Supply

Filtering - parasitics not crucial

I"-qh Filtering - right filter design fl' " Ot' W''

f;H ,h&boNE I50 pf pw: 2 us 4 ' I -

Power4Lab HKU

25 uH

25r l

2x47OO pt

1

1O nH

PowefLab HKU

Don't always blame theparasitic elements

5 0 0 p f P w = 2 u s

0.3lPf rlot

Jt( t . t0t t t0rt i l - tI t i l ! : : l

ww. ee e - h ku. h li powe r _e I e c t r o n tu _! ab/

{I i sl .!r . l f, ir

Prepared bv Fran*i Poon & Bruun Pong

EMI in Switching Power Supply

2x47OO pf

10 nH

Power"LabHKu

h.rtrd 5 p f

Vp€ak =aoo V

T r = 5 0 i l s

T f = 5 0 n s

P w = 2 u s

A very small fi lter canfilter out the noise !!

Per = 6.6 us

0.31pf r l

25 uH

25r l

Prepared bv Franh Poon,i tsnon Pons

El"ll in Swttchmg P.\'er iuDpl| v*w eee hku hltloower clcctronrc: iah/

Filtering - how small it can be ?

2x22OO

1

PowepLabilKu

I=tk Filtering - simplified view-

r) ) i l +-l- r H t t

Prepored bv Franki Poon & Bryu pong

EMI in S\9itching Power Supply ww eee. h ku. h lUpowr e I cctrcn ics lab/

a . n i l

Power"Lab HKu

P.eparetl bv Fronki Poon & Enan pow

E'Vl rn S*.itchinq Power Suoplv

During bridge conductionperiod Tcon

ID

Filtering - get back to the reql circuit , i l i ' l *\ - t

.1\

'avu Lee.nku hlonrwtr,.4cctrrnt6 ab/

Powel.Lab HKU

During bridge conductionperiod Tcon

Prepared bv Franki Poon & 9ryu Pong

EMI in Switching Power Supply ww. ee e. h ku. h l<./ powe r -e I e c t ro n i6 -l a b/

Filtering - get back to the real cirait

Practical Look

PowereLab HKU

Filtering - are the two practical circuiteguivalent ?

During bridge non-conductionDeriod t * Tcon

P-eoarcd hv frunti Poon & Bnun ?ont:

E,llt in Swichinq Power Supoiv

Practical Look

Po$/er.Lab HKU

I'qf* Two dffirent fi lters - go to their equivalence- t *

r--r-^-tFa$-l t l + - rr ? | T

During bridge non-conductionperiod t ;e Tcon

rr*'l-€4 -ALrtJ l l + r ' r -, / t l I

I T I TPrepored bv Franki Poon & Bwan Pong

EMI in Swttching Power Supply ww. e e e. h ku. h l</ powe r _e I ec tro n iu -l a b/

Power.Lab ilKu

2 pl -..,r__r*,.\.\_rrF( = )-_.r\ f ' t | \ 7 I< t t r - |/ t t I +I t / l - T '

Not bad during non-conduction Deriod

,,2 ffr F

Cy: ; i : r l j

l0lir lilil :.ill il : r, l:x, iift

L"namJ hv Fran*t P^un.\ 8^'tn P,'ng

E.lll in Switchinq Pow.er Supoiv "w' eee hku.hlspower _clectronics,!ait/ | )0

PoweraLab HKv

z pf ./__--.\A-_lr_J i If7_

__,1_\f1< i l r I/ l l T - - r -i T I T

Better during non-conduction period

:0 ! .1 S( l i y r r : { l . t r a . rc r : :$ : : f ,nl ; r l i : 1 1

Prepred hv Franki Poon & Bryan Pong

EMI in Switching Power Supplv ww. eee. h ku. h Vpo wer _e I ec t ro n i 6 _i a h/

Powel'Lab ltKU

7iI'tn' 'L"n' (ftfu

t filters - Itft and right

High Z loop High Z loop High Z loop

l r : r : l i l i i i ' r . l l : , 1 r . t i r : { l JC/ r r ' l i , l ) t1 , f l . t ! t l r ;u r , : l r r

wwweee-hku.hLJoower leclronrc! ldh/ ll:

fi ;,-'uo,"u nu ,-,r, ,ou, ,ir'U*un ,*rI# t.ttt tn Snilcning Power Supptt

Power.Lab HKU

Invisible path - Secondary to earthcapacitor

Prepared bv Franki Poon & Bryan Pong

EMI in S\|itching Power Supply ww. eee. h ku h Apo'9cr _cl ec r ron ts _lah/ 1 3 3

LISN t- rT

:t-E

Power.LabHKu

Sec. to earth capacitor - circuit model

Prepnred bv Franki Poon & Enan l,ong

EMI in Switchinz Power Supplv

LISI{ 'FIT I{E

I F

,re\+ cee. hku. n lu power _el ec tn tn ru -l ab/ ! i 4

Power.Lab HKU

capacitor - how big ?

C = 0.085A/d pft C* | _ [-----7 O.r5cr'

) --tt-( .-t"7 /7 + C**=53pt/

" \

- / //- i

r = 7.5cm

Cspnere= 4to,0885rpf

CsE : 1.67 pf

Prepared bv Franki Poon & Brym Pong

EMI in Switching Power Supply ww.eee.hku-hlawwer electroniu lab/

PoweFlab HKU

VpEak =4O0 V

T r = 5 0 n s

T f = 5 0 n s

P w = 2 u s

Per = 6,6 us

- rare noise

Greatly exceeds limit -usually come across inbad designs.

Preparpd hv Frann Poon & gruun .\'nt

EtVI in Switchins Power Suppiv *ww eee. hku.hlt power jlectronrcs ,iab/

capGCitor

t i 6

Power.Lab HKU

Still exceeds limit evenafter filter is added.

Prepored bv Franki Poon & Bom Pong

EMI in Switching Power Supply ww.eee.hku.hApower-electroni6_!ab/ 137

to earth capacitor - with filter

Vpeak =400 V

T r = 5 0 n s

T f = $ g n "

P w = 2 u s

Per = 5.6 us5

2x22OO pt

2 5 u H 1

2 5 n

10 nH

PowefLab$Ku

Sec. to earth capacitor - Pri.Capacitor

To Sec.

H#

The primary to secondary capacitor can by pass,Ih 5,,f; p)fr ,g,S15g1j",gen e rated f ro m th e p r i m a ry s i d e.E,Vl in $witchinq Power Supolv avw Lee.hku.hvpowar -electrontu-loh/ l J8

Power.Lab fiKU

-\ Pri. To Sec. Capacitor - circuit model

Provide a lowimpedance path toshunt or by passthe current flowingto earth

Or you caninterpreter Cps asdividing down thenoise voltage

Prepared by Franfi Pan & Bryon Pong

EMI in Switching Power Suppiy ww.eee.hku. hL/power -electronig -iab/ | J9

PoweFLabHKu

To Sec. Capacitor - save power

Much better soiutionas no eKra Dowerlosses is produced.

-rir xtr . tl :;$ :rli

Vpeak =4OO VT r = 5 0 n sT f = 5 0 n sP w = 2 u s

Per = 6,5 us

2x22OO pt

2 5 u H 1

25r l

10 nH

fi P."ooreu hv F.anki P.o, & Bwon p,ns

# t,Vt in Swilching Power Supplv svw. tee.hku.hvpo*er _electrontcs -!ab/ i l0

Power.LabHKU

To Sec. Capacitor - drawback

HI{ttPrepareel by Franki Pmn & Brynn Pong

EMI in Switching Power Supplv w w. ee e. h ku. h fu pow er -e I ec I ro n i c5 -l ab/

Increase leakage current !Capacitance is limited.

PoweFlab ITKU

I

: . . - . . . . . . . . . , . . . . . . . . . . . .

Any point on this sideprovides by pass effect

Q! C.vtt tn Swtrchrnq Power Supp} .t ttw,: ee i ku. n ll lnwer,. i cclro n tc-t.�i.th/

(d,h c''xf

Wfa'n:u't

How to split the straycaDacitor ?

Sec. to earth capacitor - by pass inside ?

Fi{stPrepared by Franki Poon & Boan Pong

EMI in Switching Power Supply ww. eee. h ku. h Upowe r -e I ec to n is _l abt

Power.Lab rrKU

I

I

i

capacitor - F.5 physics

I-T-

T

Powel.LabHKu

III

-T-II

ie\. lee hku hlapo\'er tlectntntcs ldh/

H ,,"uur"u ou rrankt Poon <i Stuon pong

E* EMI ,n \wilchmq Power Suoplv

Power.LabHKu

to earth capqcitor - qdd one more plate

Fil

ffi Preparerl bv Franki Poon & Bruon Pong

5., EMI i, S*ttching Power Supplv ww.eee.hku.hVpower _electrontq -lab/ 1 15

PoweFlab HKU

to earth capacitor - better way to by poss

ffi ."<oared hv F,un* Poon & Brydn P,)n\

&) e .Ut m Swrtchuq Power Supolv 'urtw. cee hku. nlv power lleclrontcs idb/

PowePLabHKU

Preparcd bv Franki Poon & Bryan Pong

EMI in Switching Power Supply w w. eee. h ku. h la power _e ! ec I ro n rcs _l aol

PoweFlab HKU

capacitor - another noise source

Fi

HSecondary winding alsoact as a noise source

Prt'pared hv Franki Poon & Bryon !)ong

EtVl in Swrrchins Power Suppiv

LISN +f II +[

r : I^�\

v \ !wcee.hku.hvDo\9er , i l cc t ron tcs 'dh / l l l

Power.Lab lrKU

Sec. to eorth capacitor - noise source on Sec.side

Preparcd bv Franki Poon & Bryu Pong

EMI in Switching Power Supply w\e. e e e. h k u. h l,Jpo \9 e r _e I e c t r o n i q _l a b/

Power.Lab HKU

capncitor - final solution

By pass shielding By pass shieldingcapacitor connectedto secondary quietnode or 0V

capacitor connectedto primary quietnode or 0V

l'reparet! hv Franki Putn & Bruan Ponc

EMI in Sttitching Power Supniv $rw cee rku hl!po\|cr :lectrann:s obt

Powe-LabHKu

B1t pass or simply short circuit

By pass any noisegoing r ight

By pass anY noisegoing left

Prepared by Franki Poon & Bryan Pong

EW in Swilching Power SUPPIY ww. eee nku. hfu power -e lec rrunit -[abl

Power'Lab HKU

Iqlk Don't forget the leakage capacitors

ffi P,eorct ht F-nkt P't,tn & Bnon l','ng

{t f f . t t l ,n Sui lchng Po*er SuPPlt sr w eee. h ku. h lJ Do\eer I I ec I n ) n tcs -i ab/

Shielding, by pass or short circuit 7

Fiqla

Does it "shi€ild" all the noisegoing out ? qtuQ'ffifu:

Prepared hy Franki Poon & Bryan Pong

EMI in Switching Power Supply wvw.eee.hku.hly'power_electroniu_lob/ t5J

Pawer.Lab HKU

/i\- 1 J F -

\-l __.] L_l l

,4hp'il--

Large Metal

Prqared hv Frunki Poon & Erran l>onc

EMI in S*itchinq i)ower \upplv

i.-:-_)

r i"r--J\,1JL- --ll--r L "

i l l ;--:E::--

'"*w eee hltu.hlloower':leorontcs loht

Rer-ision again - I

Power.Lab HKU

rwv It #

I -

TLarge Metal

ITI

AvI

Prepared bv Fronki Poon & Bruan Pong

E'Vl in Switching Power Supply

-.rA--rLJL[�-l\ 7 r r L - - - - : j

'*w. eee. h k u. h lo power -cl ec! ron t 6 _lah/

Revision again - 2

Power.LabHKU

II

I

4W Don't float the metal plate/:__

Nc l / - .| / h l

h'Ae \7 -JF

Larse Metar -'1F

--:-i W\'tti tr - lt.I.1.'r..I-"l.]--ffi.I-

r-lt l

\Z| ,-., lou , r:::r,

-lv q : ! - J ! J F l " l I

\ i / " ' _ :

HH

'.Tarcd hv Frdnh Pmn .J Bnun P ny

# t.Ut .n S*ttcntnq I 'tuer Supplv 'avw cee hku.hApower _4lcctronics _lah/ i 5 6

T

Power.Lab HKU

By pass all thenoise currentback to 0V

| ^ 11 [g:Zt-; -l

rhevictimwourdovL{:}- itr -ll- |

" j see any noise\-./ | | Curlent IIOW ln

--]"]..].]Ttr].ffifEE-

The victim wouldonly see the 0Vof the noisesource

ww.eee.hku.hk/power electroniu lab/

By pass and short circuit

Prepared bv Franki Poon & Bftan Pong

EMI in Switching Power Supply

POweFLabHKu

-aaShielding -Usually come acrosscharacteristic impedance,attenuation, refl ectionlosses

The Truth is -Plane wave propagation, or noise source is located at a far distancefrom the shield.

Prepared hv Frotki Poon & Eoun Pong

E,lll i.n Switching Power Supplv

Wait a minute

N|| eee.hku-hupower electronrcs .'uot i58

Power.LabHKU

Sttll Ltse by pass and short circuit concept

r l l w V 1

.:I

T c'arf

If far enough,C*17)) C*o1"

\+ ) 0 -tF

Prepared bv Franki Poon & Bdan Pong

EMI in Switching Power Supplv w\|. eee. h ku. hk/lb'9er _e I ec I ro n i6 -l a b/

€-

Power.LabHKu

Prepored bv Franki Poon & Bnan h)nr

Elvll in Switchins Power Supol.v '"ww eee.hku.hk/powcr jlectrontcs,lab/ I 60

Short summary. Lump element circuit is possible to simulate EMi

behavior,' Parasitic elements is not enough to explain all

cases. (More concept will be introduced.). So call electric field shielding rnust be

terminated one end to a quiet node or 0V of thenoise source. NO FLOATING I

. So call electric field shielding is a kind of bypass/ shunt or Sbcd-Cjrcuit equivalent in a lumpelement modell

H,*

Power.Lab t|KU

Prepared bv Franki Poon & Bnaa Pong

EMI in Switching Power Supply ww.eee.hku.hUpowerelectrcni t lab/ 16l

iil|]fi qufl$t10fi

H

PoweTLaO HKU

Duringperiod

Prcpaftd hv F,anki Poon & Snun Pong

E,Vl in Switching Power Supoiv

bridg€ conductiont = Tcon

:vtvw cca nku hllpwer t:leoronrc-t labt

Input terminal - conduction period

! 6 2

Power.Lab ItKU

During Oiiage non-conductionperiod t * ' [con

Prepared by Franki Poon & Bryan Pong

EMI in Swrtching Power Supply

Input terminal - non-conduction period

Power.Lab HKU

Input terminal - coupling capacitor

=0 .01 cm I

0 .1 cm

Inputtrace

oo

H ' - . .Dar (u . t f ' r D tk t i> ,Dn. i Bn 'un t "ns

-$ r . l l l tn " * i t ch tnq Pcwer Supp l . t ' 'mvw. eec. h ku. h lv power -: i 4 | rt ) n tc i _ db/

IIIIIIIIItIIIIIIIIIII

Power.Lab HKU

Input terminal - coupling capacitor value

" lrace lrace -

0.0885a(e , + l ) / :l 0 - r 4

z (

/ t n ( - )' W + t '

5 1 = 5 c m

52 = 5.4 cm

W = 0 , 1 c m

t = 0 .01 cm

E r = 4

Prepare<l bv Franki Poon & Bryan Pong

EMI in Swtching Power Supply w. eee. h ku. h Apowe r _e I ec r ro n t u _l a bi

0.0056 pf

PowefLabilKu

:

0.0055 pf

Vpeak =4OO vT r = 5 0 n sT f = 5 0 n s

s o a / l50uH x2

P w = 2 u sPtr = 6.6 us

:ww eee. h ku. hA power ! | ectron tLs - oh/

terminal - simulation

0.0055 pf

ffi !',cpar.tt hv Fnnti "oon & 8^an Poa\:

Ss+} f j . !11 n Swrchtnq Power Suoptv t 6 6

IIL .

[ -

IIIIIIIIIIIIIIIIItr

PoweFLab HKU

Input terminal - imbalance impedance

Prepared by Franki Poon & Bman Pong

EW in Switching Power Supply qw\| cec. hku. hvpo\'er _e I ec t ron er -l ab/

Powe-LabuKu

Input imbalanc e impedance- simulation

Limit Exceeded !! .,; t - t t n - u h v i . ; t t h / > . " n < i 3 r . n . ' o y

E,Vl i.n Swrtching Power Supolv

0.0055 pf

100 uH 0.5 Q 0 '

5O uH 0 .2Q

Power.Lab HKU

Input imbalance impedance - sohttion

Pass in s!ffrulation ?Prepmred by Franki Poon & Bryan Pong

EMI in Switching Power Supply ww.eee.hku.hVpowerAecrronics-lab/ 169

0,0055 pf

1OO uH 0.5 n 0.005

50 uH 0 .2O

Power.Lab HKU

Input imbalance impedance solution - Real?

w|| cee hku hfupo\|er zlectrontc\ lttb/ i1A

0.1 uf - Q.47 ut

tItITIIIIttIIttI

Powef Lab Hriu

-T3fr Input imbalance impedance solutiorl -_hence

'f'P'th t-' b l4t3q2oo'

@\{fur

ff i ,ta",,u,'v;.,nn Po,n & Btuun p,)nt

V E.ll l .n j*uchtnq Pcwer Suppiv 'w* .cee.hhu.n lonwer : tec t ron tcs , th r

0.1 uf - O.47 uf

Power'Lab lrNU

*i= Dont forget* l -

llllis,'.*''U l*J Magnetic Noisevoltage

: / \l--\ -,^/-=-

-'- \,/Vu pi"k uo

EMI in Switching Power Supply ww.eee.hku.hk/power-elrctronis_lab/ f 7t

I I l" 1r,"o,.,. o.,o | |7 t + i + r N o i s e

& ;.-I--&H tst --r/ ----,/!0"--Scffirrri eoon & Bruu Pong

vr pitk up

PowereLab vKU

Input imbalance impedance - bad CMC

A filter is formed by the leakage inductance ofthe CMC to provide extra attenuation cln thenoise picked up by CMC

Prepared bv Franki Poon & Bnan Ponq

EW in Switchinq Power Supply twteeehku.hk/power_electronics_lab/ l7J

0.1 uf - O,47 uf

Power.LabilKu

Input again - is everything fine?The large input X-capacitorprovides a final lowimpedance loop with theLISN. Magnetic couple wil lcontribute to noise pick upby the LISN

Prepared bv Fruilki Poon d 8^vn ['')n\

eMl in Swtchinq Power Suopil' .6t9' tec.hku.hlrlpo*er -lectrontct lttb/

PowereLab HKU

1 c m

5 c m

2 c m

2 c m

- - l -

-Ll-

f

f:Z^| . . .1 { . ' \ y

ffi Preparetl bv Franki Poon & Boan Pong

V EM! n Switching Power Supply ww.eee.hku. hupower electront6 lab/

Input again - mutual inductance

Power'Lab HKU

I l cm

I

Ioop mutual inductance

W'= 7 cm

W = 5 c m

L = 2 c m

Ltine_top = 0.73 nH

Ll' * W'L I ir, - t n,, p = 0'00: I ( ln(--------- ) u H'

W'= 7 cm

W = 7 c m

L = 2 c m

Ltinc_toop = 0,53 nH

T -Lline_loop_Eqv. -

,''repared hv Frunki Poon,i 9ryan Pong

E.lll in Swtchrnq Power Suoolv

O.2 nH

t 7 6

Approximated line to

M eee- h ku. h *! powe r _el ec tron rcs -i tb/

Prepared bv Franki Poon & Bman Pong

EMI in Switching Power Supply

fs = 150 kHz

uww. eee. h ku. h fu power _e I ec t ro n i u _l ab/

Input loop noise - example

Power'Lab HKU

LIS!I I AVi 'F

{E

TI

Ip€ak =25AI in i =15 AT r = 5 0 n sT f = 5 0 n sP w = 2 u s

Exceed limit becauseof small input loop.

Input loop noise - magnetic tnduction

0.1 ufPer = 5.5 us

Power.Lab HKU

a\v||- eee. hku. h Apo\|er _c I ectron rcs ! ob/

ffi ,'r"oareu hv Frank P'nn 3 Brydn p.nq

t j EVI inS*ttchrng Power Suoolv

r|IIIh

PoweFLabHKu

Prepared bv Frunki Poon & Boan Pong

e Ml in Switchinq Power Supplv '^ew eee.hku ie Dower _ 1ccnonrcs, ahl

Converter to

Power.Lab ilKU

Zvo-rt

Prepared bv Franki Prcn & Bman Pong

EMI in Switching Power Supply ww. eee h ku hupower _c I cc tron i6 _l abi t79

Other noise loop ?

iI

I

IIThtrhhhhtttttIIr|r|r|

PoweraLabHKu

Loop - capacitor

+

Let the total surfacearea of the wholeconverter is equal to asphere with equivalentradius r

r= 5cm

As the self capacitanceof a sphere of rcm

Croh"r.=4x0.0885rpf

The equivalent drainself capacitance is

Cdrrio = 5,5 pf

Prepared by Franki P@n & Bryu Pong

EMI in Switching Power Supply \ww.eee-hku.hupo'|er -electront6 _lab/ t ll I

Converter

Powe.LabuKU

- Qpical value

r = 1 c m

R = 2 c m'V ,,r" -,u,,,

R i R r ._ - / { _ ) - _ t _ ) -

r 0 0 ! ' r o o ' ' 1 0 0 '

The mutual inductance is

Z,^.-rjo!. =3,3 nH

fr P.'parel hv Flnk Pd,,a & Bnan P,ns

l# E.lll n Swtchtnq Power Suoplv

Converter earth Loop

, rw , :pe .hku .hLouvc , le t ! ron ic t ieb /

Converter to eartlt Loop - resonate loop

Fh

ELTF

h

EhIt!I

Prepared ov Frunki Poon & qruan P'tng

ELll in Switching Power -iupply, ww eee.hku.hlopower .4ectronrcs ,ab/

Converter to earth Loop - raw noise

25A still can'tfail it!

Be careful,,***,r*8"3.[[y;[oseEMI in Swilching Power Supplv

!w\9. eee. h ku. h Apowe r _e I ec I ro n i 6 _! a b/

Ip€ak = 25AI in i =15 AT r = 5 0 n sT f = 5 0 n sP w = 2 u sPs = 6,6 qs

300 uA fail it by30 dB

Fail, much worse :rii r/r !

than the 25A case !

L1 Lz c r lF * "7

,7 t , r6

',|tft'E '

[* t- \ IE'h "

r *

ttItIIthhtrhhhtrTrIII

Power.LabHKu

sto'\ l l i; i.: '

L 3.3 nH 11

22O pt

00 nH vn

vp€ak =400 VT r = 5 0 n sT f = 5 0 n sP w = 2 u s

t ,

Atrnductor only di ift theresonate point.

Prepared hv Franki Poon & Boan Pong

EMI in Switchine Power Supplv

gt't('Nw. eee. h ku. h Apo w e r _e I ec t r o n i6 -! a b/ Iil5

(

Resonate loop - CMC c

Power.Lab HKU

Resistor reflectingcoae loss€s

Resistor reflecting Resistor reflectingskin / proximity dc winding losseslosses

Frequencydependence

Frequencydependence

Frequencydependence &windingstructure

Wire sizedependence

Remember this ?Prcpareci hy Fnnkr Paon & ?rudn Ptn{

E,Vl in Swtching Power Suppiv

Resonate loop - RES/STOR

'ttvw ece.hltu.hlvpuwer clettft)nics ub/

PowefLab ilKU

Resonate loop - increase resistance

1OO uH +10l / L p f

Unfortunately, notmuch better.

Prepare<l bv Franki Poon & Bryan Pong

EiVI in Swilching Power Supply www. e e e. h k u. h Apower _e I ec t ro n t cs.�i a b /

22O pt

Vp€ak =400 VT r = 5 0 n sT f = 5 0 n sP w = 2 u s

Power.Lab HKU

Increasing resistance - at. ,

- ' . r | |tne rtgnt place

Much better, but how ?

! i i ! lr;r ' i ir, :..!t j f^lr . Llr ::!.1 j$' : :

!'repared bv Fronn Poon d Bnon Pony

E,lll Ln Swirchnq Power Supplv

22O pf

Vpsk =4O0 VT r = 5 0 n sT f = 5 0 n sP w = 2 u s

tww eee.hku.hloDo||er riectrontct iab/ i88

hIInI

'r{ d"' Pt LS

PowefLab HKU

Prepared hv franki Poon & Bryan pong

EMI in Switching Power Supply

II

p c n

\r- a

ww. eee. h ku. hHDower e I ecrrcnis labt

Increasing resistance - lossy ferrite

22o pt

i',tuarea hv irukt Pnon & Boun l,on\

E,l/l in Switchins Power Supolv

Power.Lab tlKU

Ferrite beads

'ww.eee hku.hh,power cledronrcs lob/

FtIhhtthhhhhhtIII-t

IIIr|I

PowePLab HKt)

Invisible loop - inside xformer

Xformer is tightly packed and has large stray capacitor tointroduce many loops inside.

Prepared bv Franki Poon & Boan Pong

EMI in Switching Power Supply ww. eee. hku. hApower -e I ec r ron rcs -l ab/

PoweFLabrrKU

I"qk Short summary

. Capacitive coupling to input terminal causes EMI.

. Solutions for capacitive coupling lead to moremagnetic coupling effect.

. The whole convefter to earth has a large capacitor.

. Magnetic coupling causes EMI due to the loop formby the convefter to earth capacitor.

,j;if, Resonance causes unexpected EMI level.. Damping/not inductor, is the solution for resonance.

+6-tv ttad . 4{ r;l r Q fit g-'? I"4 t t ld--'

ffi P-eparet hv Ftunxt P.on d 7tudn P,,n\

i f i S,Vt n Swilchng Pnwer Supplv *rw.eee.hku-nlapoler_t lectrcntcs_labt i92

I|I

t

III

Power.LabfiKU

finy $mqtle$tiun?FH{!a

Prepare<l hv Franki Poon & 9ryil Pong

EMI in Switching Power Supply ww.eee.hku. hvpowcr _electronia _lab/ 193

Power.LabAKu

How does EMI come out?Contacted -

can be understood

through circuit diagram

Non-Contacted -

Mufual invisiblecapacitor & Mufualinvisible inductor

avw ree hku hioAner 'lecrntnrc.t !ah, ,94

httIIIIrll

PowePLab HKU

Preporerl bv Franh Poon & Bnon Pong

EMI in Switching Power Supply ww eee. h ku. hApower -eI ecton iu _!ab/

V & I O n l y

Power.Lab HKU

Only LISN terminals voltage are

L1

LISN

G L ,

l,^,l v , ) I

f f i .I I,:'' A

-'tI z.

r No matter howcomplicated a circuit,EMI are voltagemeasuremenB, VL,r",and VLine2, across LISNterminals.

. Vlinet = VL1-VG

. Vtine2 = VL2 - VG

r Is there a simple wayto look at it?

ffi P'eutr.a hv F,an<t i','on & 3nun Ponq

l!|. t.Vtt tn S\rilcnmq, Pnwer Supph' *vw.eee.hku-hl</powerelectronrcs lab/ 196

t*rhhhhhtttIIIFI

tttIIIIt

PoweFLabHKU

r - S / , ' Y l , ll t t - / /

t t f l f l

l . ^ = T Y , - Y L :' L t / -

, L t 1 ,t = l

' t f / f ,

r - Y Y i - ' Gr c - /" ? 2 . ,

Pr.psred hv Franki Poon & Bmm Ponu

EMI in Switching Power Supply ww.eee.hku. hUpawer _electroniu -lab/ 197

vL1

LTSN

G L z

\tV* V'u

t n o u " " i

\Ir

PowefLabHKu

Zn-u-

r / ' V t / l,

' e q - ' L l r l - Y L lr / t = -

7 7L L l veq - L l v t )

. v ' ; o - v r = v , u _ v t :f - ' t ' -

ZL7 , "0 Zra , ,

a' , i ' : - : t , , V'"r-VO V',)-VCu0,., i .Zt:-uo j . i zc-uo t . = -

L, i Lr i c.; "

26 _req Zc _r,t

One voltage source and six mutual.impedances

i'rypareol hv Funkt Poon ,7 Bnan Ponr

EMI in Switching Power Supplv .ww.eee.hku.hk/power clectrcnrcs !ob/ t98

PoweraLab tlKU

vr-rr-r, t , / - \ - r z' . " 1 _ L l . L : -

L t r L . r l - l . l _ L : , i

m

t r ' - \ - r z' V _ L l - G -

L . ' i u . U _ L l . G _ r

m

t . / - \ - l z' . u - G -

/ r r i L , v _ G _ i

f. . . - - t

i it . . ' . . :

Prepare<l bv Franki Poon & Bnoa Pong

EMI in Switching Power Supply w\9. eee hku. hupower -electroni6 _lab/

Power.Lab ltKU

source

l / - I 7' v . L t - L :

- t . q . \ t L t . L 2 - t e q

' , V - C - r e q L . V G l e q

\; t - "Ddr (d rv Fr ' i l t k t P . "n , i Bnan P, tny

E,Vl in Switchtnq Power Suopiv

' . V L l G - l e o L \ 4 L l G l e o

One current source and threemutual impedance

ww.eee.hku.hk/powerelectrontcsiab/ :ll0

Equivalent current

tI-1'

!-

E

Powet LabHKv

Total 9 eguivalent mutual coupling impedances

1 equivalent voltage source

1 equivalent current source

Prepwred bv Franki Poon & Bnon Pong

EMI in Switching Power Supply www. eee.hku. hUpower _electroni* -lab/ 20 I

PowefLabHKu

0%-utn'Hot switchingnode to eafthequivalentcapacitor

HF'

Prepared bv Frcnki i>oon & Bn-an Pong

EMI in Switchinq Power Supplv

Physical meaning

,nw. e e e. h ku. h kl pow er _e l ec t ro n r cs.�l ab/

hhhIIhIIIII

Power.Lab HKU

Crr-r.o&Ctz-ves-

Hot switching nodeto input tracesrepresented byequivalentcapacitors

Prepared hv Franki Prnn & Bryan Pong

EMI in Switching Power Supply ww. eee. h ku. h lo power _e I ecrrun tcs _la bt

Power.Lab fiKU

LVo & Cr'-no

Preparetl nv Franki Poon d Bnan Pong

E,Vl in S\litchinq Power Suopiy

Ctt-no&Ctr-vo-

0V node to inputtraces haveequivalentcapacitors

e

Absorbed in theinput impedance.

'ww eee.hku-hL/g)wer -Llectronrcs _,an/ :01

Physical meaning - Ct

t;

t;

;

;

tr|tI|ttttttttttt

Power"Lab tr(u

Ce-ro-

Converterto eafthequivalentcapacitor

Prepared bv Franki Pooh & Bnan Pong

EMI in Swrtchinq Power Supplv twtr - e e e- h ku - h Apow e r _e I ect r o n ics _l a b t'

Power.Lab ilKu

aLttt_tl_Lz_req-

Input l ines loopmutual inductiveimpedance

i ) r "pare , l t v F . .nx t i ' , rn * . lnan P n t

E,lll in Switchinq I'cwer Suoplv t\'\r v r ec. il tu. n B Do |9er -!l ectro n Lct _idb/

V,vr - S r zC

- / J ' t L , \ l _ G _ i

7L M_G_req

Earth toconverter loopmutual inductiveimpedance

Prepared hv Fraaki Poon & Bryon Pong

EMI in Switching Power Supply ww. eee. h ku. h Apo w e r -e I ec r ro n r c s -l a b/

Power'LaD HKU

I+r+rtI

I

tIIttr|ttr|tt

' \ l - L l i - t L q L . l l _ L l , , i l e q Zr-tt-n-req-

Cross section ofLine 1, l ine 2 andeafth loop mutualinductiveimpedance

Preparecl bv Franki Poon & ]ruon Pong

E.Vl in Switching Power Suoplv

PoweFLab HKU

wttw. eee. h ku. hlo powe r -.i ec Iron ics _l db/

Power.Lab ilKu

vp = 4oovtr = 75O ns

t f=20ns

D = 0 . 2

Fs = 75O kHz U = ISO ns

ffi PrepareJ hv Franki Paon & Bdok Ponq

$f, t.Ut ,, Switchinq Ptwer Supplv

fs = 15O kHz

twv. eee. h ku. h Apower -e I ec tron iu -lab/

Overall simulation

O = 0 . 2 n s

PoweraLab HKU

4 c m II o.1 cm

I l-TIr I n

l l\z

) o'rr.^

420.085I - - n f-sphere-

| YJ

Prepared hv Franki I'oon & Enun Pong

E,Vl m Svitchtng Power Supplv

Cn_ruo = 0,2 pf'qvwcee.hku.nhpower-"l""rror,r.r-tnllrt 2t0

Powel.Lab HKU

Realistic palameter - Crr_vuq & Cu_r",t = 0,01 cm

+

0 .1 cm

oo

5 c m

0.4 cm

C trace rroce0,0885a(e . + i ) /2

zSl l n (

- - )

W + t '

l o - ' '

5 1 = 5 c m

52 = 5.4 cm

W = 0 . 1 c m

t = 0,01 cm

ef = 4

Crr_rn = 0.0056 pf

Crr_r* = 0.0055 pfi>repared bv Franki Poon & Soan Pong

EMI in Swttching Power Supplv wts.eee.hku.hApower_electonrq_lab/ 2ll

Powe,-Lab vKU

Errl@ parameter - Cr, ,o & Cr, ,o

Absorbed ininputimpedance.

708 uH O.tO

H , ' - 'o"r" , l n fntnxi Poon & dn,n p,,nt

t7r-h f:.Ul .n Swtrchrng P,rwer Suporv ,ww eee. hku.hltpower,:iectrenlcr l.b/

IIr|

PoweFLabHKU

Measured as

Co_no = 6 pf

Prepared hv Franki Poon & Bpan pong

EMI in Switchine Power Suppll, ww.eeehku.hUpower electrunis lab/ 2l l

Power"Lab HKu

r = 2 c m

R -- 7.9 cm

The mutual inductance is

Zn-c-r.q =77 nHfi

..-ea,.u ;v i,"^x, il,,i ';'j;",

,,.,,r$tl E,l// tn Swttchnq PawaT \ypoi, ,qew.cee.hku_nttoower elerronrcs lab/

r|

Power.Lab HKU

As the input loops are small and havingquite a high input impedance, hence forsimplicity,

Just set

Zr-rr-G-r.q = o

7 - 0aM_L2_G_feg - |

Prepcred hv Ftunki Poon & Bmm Pong

EMI in Switching Power Supply ww. eee. h ku. h A power -e I e c tr on iu -l ab/

PowefLabHKu

I'rk PSPICE Simulation

r $ : 1 . / { r o o 5 . o

i

/{'w

r b ).*v*.eee.hku.hAytwer clec,ronics iab/

f f i , ' r "ooret . \v ; . ,nxi . ' r tn & \ryun?ong

IJb tUt in iwilchnq l'ower Suoplv

IIIII

PowereLab UKU

Simulation & Measured Results -

ii,rril'frL,,,,1 *J'

tily6,ttiu'"ff* w-*6r'�{{a+ 4+"errp"e'- r'l

Line 1 measured result 51 open Line 2 measured result 51 open

Line 1 simulated result 51 open Line 2 simulated result 51 open

Prepared bv Franki Poon & Bryan Pong

E,VI in Switching Power Supplv w\r.eee.hku.hl4po*er-electronics-iab/ :17

51 open

PowefLab fiKU

Line 1 measured result 51 close Line 2 measured result 51 close

Line 1 simulated result S1 close

P,epared hy Frun*i Poon & Sdun Ponq

Etlll n jvtching Power gappiy'

Line 2 simulated result 51 close

.ww tee.hku.hloutwer :tectronrc: lab/ I lE

Simulat ion?: 51 closed

tIII

PoweraLab HKU

S1 open - Capacitive coupling only

Resonate behaviorbetween the inputequivalentimpedances

Prepared bv Franki Poon & Btuan Pong

EMI in Switching Power Supply

Line 1 measured result 51 open

ww.eee. hku. hlvytwer -electroncs _{ab/ : I9

Line 1 measured result 51 open

Power"Lab ilKu

51 close - Capacitive & inductive coupling

equivalent impedance-

Resonatebehaviors of thesource loop andmutual inductivecoupling

Line 1 measured result 51 close

f f i Pnpanu hv F,ann Ptnn. i dnon P.nt l

*4 E.Ul m Swtchng I 'o\9er SuDptv *s\9 eee.hku-n*/oo*er electronE\ idb/

Ir|

PowereLab AKU

Prepared hv Fronh Poon & Bn'an Pong

EMI in Swrtching Power Suppl.v

Minimum Coupling Model. A minimum of stx capacitive mutual

coupl ing impedance is concluded.r A minimum of three inductive mutual

coupl ing impedance is concluded.. Complicated EMI waveform can be

simulated by simple lump elementcircuit.

r I t is a minimum model, not maximum. Good for diagnosis purpose.

fT{t" @w.ece.hku.hlupowcr elecrranrcs labt -'-'/

Power.LaD HKU

Hr!'

^l^Sil|)fi nrrc '' 0'u*ur r tllltsll0il i

!'repored bv Frunki Poon & Bnnn i'ong

EMI in Swilchrnq Power Suppi,.' , v tswcee.hku.h t lpower 4ecr ronrcs .ob / )22

Power.LabHKU

Don't let anycurrent flowinto theLISN

ffi P.eoare,l h F,nnkt Poon & Bmun ponq

.t!:t t.t1l in Swuchinq Power Supplv \Nw. eee.hku. hlqpower _e[ecrroniu -lob/ :: ]

-1, Shielding - Purpose

Shield or being shielded

I lock upthe wholeWOrId, HE,h a , . *

i)reparel bv Franki Poon <,) ilruun pont

.i,lll in Swtchinq Power SuDplv ' v rvu eee h l iu .hk l *e r t l cc r r ,n ts lahr

Power"LabHKu

Fi{:?

Prepored bv Fronki Patn & Boon Pong

EMI in Switching Power Supply ^w w. eec. hk u. hkt pot e r _cl eer ron rcr -tab/

L1LISN L2

G

Put a metal enclosure to "shield"

noise from going out - Wrong

PowercLabHKU

I

"1k Shielding - total recall 1*l* tffil- :

tLarge Metal

No electricshield

IT

A(rL)I

Prepored hv Fronki Poon & gruan ?'tn(

E,Vl in Switching Power Supoiv

Actually, increasecoupl ing

-lF--tF "== IH{!? .uww tee.,:tku-nbttowar tlectn)nrcs lobl

hII

Power.Lab HKU

Preporcd b| Frcnki Poon & Bryan Pong

EMI in Switching Power Supply wlw.eee.hku.h lvpower . : lec t ran ics lab / : :7

L1LISN L2

+l l Gt_f

Put a earthed enclosure to "shield"

noise from going out - Wrong

PowercLabHlr(U

*k Shielding - total recatl 2*tr*

An eafthed enclosureactually increases theequivalent hot node toeafth capacitanceCn=*oand increasesnotse.

LISN 2, zvo Lt

f f i P-cpa,eu nv;rank / 'an & 7ruon P.,nt

I ! | , 5.ut 'n Swtchnq Ptwer Sunpn 't'v*' eee.eku.ngc,;wer ricctrlntcs db/

Ir|r|

Shielding

The vict im wouldonly see the 0Vof the noisesource

is all about bypassing or short circuit

ww e e e. h ku. h Hpower _e I ec tro n i 6 -i a b/

h'-V

By pass all thenoise current

back to 0V

Power.Lab HKU

Prepared bv Franki Poon & Bb^.1n Pong

EMI in Switching Power Suoply

IIl-

II

IT -

Ih

I

hh-

tIIrlIIIrIIIIII

Preared bv Franv Poon Li /)n'un Pong

E,V l in Swi tch tnq Power Suop l t ,

PowefLab HKU

L1LISN L2

GThe so cal l "shielding" should short to noise

source 0V to rdturn al l the noise coupling tooutside.

nvw eee.hku.h l tgwer ' i t c r r tn r t ,an t

fftthhhhhbItL-rhhtttttt!I

I

PoweFLab HKU

a[ 0V is the point - Xformer* t *

To secondaryequivalent 0V

I -t-ta-An-- W2

-I _/-t/-Y-Y-\_

To primaryequivalent 0V

To primary To secondaryequivalent 0V eguivalent 0V

Prepared hv Franki Poon & Bryan Pong

EMI in Switchine Power Supplv ww- ee e. h ku. h lr/ pow e r _e I ec t r on i u _l a bt

PoweraLab flKu

I

-lu 0V is the point - MOSFET

i, r l . . l . ! l . l . l

t . l t i l . . . 4; ;: a: -n . rdn l_ inp ! t

. Cra-tnprt

! . . . . . . . . . . . . . . . . . . . . . . . ::

Crct-ncaunr I

l1-vpar"u tr Frunn P nn .t Bn an l' ,ns

EMI in Swi tch tnq Power Suoo ly , @\ | ece .hku .h fu ! )wer lec th 'n rc , rn ,

r|IIII

hh

PoweraLab HKU

Grounded Case ?

Prepare<l by Fronki Poon & Bn'an Ponc

EMI in Swilching Power Supply avw ze e. h ku. h lo powe | _e I ec I rDn t6 ., ab/

L1LISN L2

G

The "shielding" to 0V wire is replaced by largecapacitor to provide ac short circuit effect.Then the case can be shorted to earth forsafety purpose.

Powe.LabHKU

Poor grounding wire or parasit ic impedance ofthe grounding capacitor force the couplingcurrent f low back to G terminal of LISN.

l'r?pored hv Fronii Poon & Boun i'ong

E,lll in Switchinq Power Supglv '""w ue nku.ak pt)wer lecrronrcs _ktb/

IItII

hIr|

PowereLabHKU

I

Ek Grounding choker&ls"

,+ww eee hku.hUpnwcr _'Iectrontcs -[ab/

A ground choke can be used to furtherincrease the impedance of the groundpath to avoid noise current flowing in.

PowefLabHKu

I,qk Magnetic shielding ?

-l*tCopper foil, Ae2=2cm2

Transformer

O""=,.-,r&1cm

ftScm

fi n,"oorru ru rranki Poon & Boon P,,ny

S E.Vl n S-trching Power Supplv .rww L'ee. h ku. h la po\| ( r -,, ecln rn rc.\ _i dh/

PoweFLab ltKU

I

=k Flux band modeling

I

' d . t ' S l . q

Itf{?

Prepared bv Franhi Poon & B4,an Pong

E,VI in Switching Power Supply ww ec e. hku. kvpo wc r _e I cc t r.n t6 | ab.j

Power"Lab nKu

InputtoLISN

Lrnpt,xrmcrr I Ilr..-rt"-*<

|lt"t ,ro*- | |z Z-rZ\ |

/I l r r l q| / \ |

Tror-

Prepared hv Frunki I,oon <l Bdon Pong

E,lll in Swtchinq Power Suppl.v

T,n-,-rro**

ww.cee.hku.hlvao\9er elecrronrcs iaar

3 Xformers

PowePLab uKtJ

-i* SimulationOnly 6 dBreduction !

2.5 nHi

0 .1 uH+

to.r nn

",;fEa,.my I I-.4 \(d. t

- CISI'R22 ."alu.ne. d^n I l ini l l inz

'- .\ok. *i lhou! uryFt bit thietdbtg

roi.\e wilh cqFt !i l I shieldinq

lndtctite.oilpic nd.te dttpled hn d.1, tdntrot

ffi P,eeare,l hv F,anh Pnn & Bruan Ponq

$j e,W n Switchinq Power Supplv rnvl. e ee. h ku. h k/ powe r -e I e c t ro n i u _l a b/

hhhtttt

PoweFLab HKU

*|* Flux concept - Believe it or Not?

. Bleakagel = Bt".kage2 ,.'; Elerasez

I|

ItII

Power€Lab HKr

I| - '-'tls Flux concept - air core is core,,. ---\...

il

You can't take it away ! Itexist even in emptyspace!!

v'v\. e e e. h ku. h lJp o || c r _e I e c r ro n i c.t,l o h i

Power"Lab HI'LI

Flux concept - air core and ferrite core

ur = 2000

,r7 7

Prryar(l br Frdnlit Pun 6 Baon puntr

EMI in Su{tching Power Supplt ,IHqlf veu .ee( -hku. hL/po\|er _elecIroni6 _lab/

PowePLabHKv

i:'�\-\,\'

iFerrite cannot /block or shieldthe magnetic jflux. It only jincrease flux Ilevel inside ithe ferrite Icore according\to ul

ww.eee.hku.hApowerelectroniuiab/ :4J

Flux concept - as a result

aQ*r..e"r

Power.LahHKU

I Flux concept -

3k general coupling-

Noise Source Pick upShort Ring

rH :'n'Darud hv Ft,nki f aun & ciilan pon\!

Q E.ll/ :n J,vttcnnq power Supplv qew eee.hku. hblb\9er elecrronrc..: tdb/

tIIIIII

Power'Lab HKU

Inlr General coupling - Xformer model

- l *

H Preporcd bv Franki Poon & Bruan Pong

EMI in Switching Power Supply ww. eee. h ku. h Upower _e I ec t ron iq -l a b/

PoweFLabHKU

Noise source is shorted

l'reparetl hv Franki Poon & Bryan Pong

EMI in S\9itchins Power Supply )6e'|.eee.hku.hklpo||er electronrcs lab/ :16

thhhhIlIIIIIItIttttt

PowetrLab ilKL

II-4* General coupling - close to pick up

.-t-

Pick up is shorted

Pn1,u,el t , , f ,ank, Putn & Bryan Ptn.

EM! n Swirching Pou,er Suppl.v vu,v.eee. h ku. hvpov,er _electronics _lobi 2 4,

Powel.Lab H N r

General coupling - somewhere in

Also a kind of bypassing circuit

[i{ P.elr,-i br Fran*t I'oort ti bnun Ponl

{ J r - ' f M t n S u t t c h t n g P o u e r S u p p l t

Or an impefectshort circuit

utLu.eee.hku.hApower_elecrronrct_lobt' 218

PowefLabHKu

I-ls Short Summary

-t*

. By pass or short circuit is a basicconcept for electric or magnetic"sh ie ld ing" .

. Easier to by pass capacitive couplingeffect.

. Surrounding the noise source withground or earth is f lOt a general"shielding" concept.

fr ,::r:*u

!, ,.antt Pt'n & 3n an Ponq

E'r E.VI in SwuLhinq i'ower Supplt' wvw. eee. h ku. h Apower _ei eclro n t6 _iob/

Power<Lab HKU

Aryshffiqun$tiorl?ffi{!�t

Prepared bv Fran*i Poon & 3n,un Pitnq

E,Vl in Switchinq Power Suppiv vr\ | .eeehku.hvDower,4ectronicsiab/ )50

||

I

Power"LabHKU

Inductor Model - not onlyparasitics

-/^\a\_

il lRr(o L(0

Thingschangewithoperatingfrequency

Itl$a

Prepared hv Franki Poon & Bn'an Pong

EMI in Switchins Power Supply ww. eee. h ku. hUpower -el ecr ron t cs I aht

PoweraLab HKU

Inductor Model - permeability u{0

No inductor-l .^^ l- .af hinhar ,^ .xrrafi#n r^tr *!?43t!ryger ?",$r" H , 4. t^frdguency.Not caused bystray u,

capacitor

Frequency (Log scale)

Prepared bv Franki Poon & 9ruan Pon.q

EIvII in Switchinq Power SupolvH tww eee.hku.hVpnwer _zlecrrontcs iabr ,'-l-'

Power"Lab trKu

Inductor Model - losses

Very smallresistor at lowerfrequency. Muchmuch biggerresistor at high u"

frequency.

Frequency (Log scale)

Prepared hv Franki Poon & Bruan PonH

EMI in Switching Power Supply qww eee hku hlupower _elecrroncs _lab'

Frequency (Log scale)

hhIItIT

PoweFLabHKu

Permeability - interpolationInterpolate the permeabilityagainst frequency with thefollowingl relation

l r ,"( i f ' -1', , , t^ru). I u , . I

a.' j ! = '-----------.-----]' ; t t n f 4 j

JJ J ur l

t lWhere m should satisfy the

Frequency (Log scale)

From data sheet

following relation

liu*r'f',," - t,,,: ull-

I LJ,,:" - /* ' ' I

l r

Relative permeability

- (f,,' 'u,r)

f i nr"oor"4 rr r ,onkt Po,,n - i Bruun ?,tns

€l g. t l i Ln Swtchtnq Power Suoplv ww.eee.hku.hApower electmnrcs lab/

tItIIIhtIIIIl r

hhhlhhhl.tI

PowercLab Hxr

H5C2 TDK data is sampled fromdata sheet as

un = LOa,

ua = O,7XLOa, fn = O,Zxlos,

u,z= 22OO, /,.: = 0.55x106

Hence m can be calculated as

m = 7,47

I t f t r x , ' ' t o l T I o t | t c ' r . t o l ' t . t r ' : . t o r t . r o qFreguen.r (bs rcale)

- lnterpolalcd ur o[ a ]cn doneter MC) r troi t l

I nterpoia,ed peneabil ih'

Prepared by Fran*i Poon & Bryan Pohg

EMI in Switching Power Suppll' \ew h. ee c. h tu. h kl po |9e | _e I ec | rcn i c\ _l a b,

POMleFLab HXU

We start with lossesHysteresis losses -

Losses ccArea of B/H loop

Losses cB2

Or

Wn = khvro,Bf,

ffi, Prenored hL Frunh Poon & B+an Pong

V- tUt n Su'itchng Power Suppl.v uttu. ee c. h k u. h A ptwe r _e I e ct re n ics _l ab./

PoweFLabHKu

As

W,, = krVolrB,,r2 f

Approximate flux level is dominated by injecting current, or

A/n l r '. 5 = I l o l l , - 1

l"n

Hence

- , 1 - -. u^u-N-Vol

W , = k . - s f l 2' h ' ' h

, 1 J t r m St -'eq s

Prepared bv Franki Poon & B-ryan ponfl

E MI in Swirching Power Supply

trl n I lv v , = x , I

h - - h - r m s

ww. eee. h ku. h Upwr -e I ec t rcn iu _l a b/

hTtTItrrI

PoweFLabHKu

*k Eddy currentx Flux

OSSCS

Flux penetrate theferrite core

Induced currcntflowing round thecore

Equivalent voltagesource anddistributed resistor

X 1 xy X

X X

' i " : xX X X

X ; ffifi

Prepared bv frunki Poon & Bruan p,tnq

&*. t,Vt n Switching power Supptv w\9 eee.nLa.hvFbwer _rlccttunrcs loD/ _'J8

Power.Lab ltKU

l l_,*ll l"+ Il +\-jl--"llr s'1J - )

EquivalentXformer model

Transfer resistor toprimary side

Simplified From parallel toversion series

configuration

Prepared bv Franki Poon & Bnm Pong

EMI in Switching Power Supply ww.zee.hkt.hADwrelectrcnt* lab/ 259

Power.LabsKu

Cross section of a toroid

Prepared bv Franki Poln & Bruan Pong

EMI in Switchng Power Suppl.v

The equivalent voltagegenerated at the feruite ring dr

dd r" r2t / = - _' A r

t 1dt r;

Or

tB rzt f / q "

/ 1 , . = . a e . :- . . l i

For sine wave ercitation, theq rms equivalent voltage is

r -Vo,,r^, = AeraB,^" ---;

rl

rww. eee. hku.hVpower -electmntcs,lab/ :60H':!*

I

II

l -L

.a

It

th-t

ttt

ItIt

tItII

Powet4LabHKu

Prepared bv Fronki Poon & Boan Pong

EMI in Switchinq Power gypp!1'

w"=k,*++g.f,r,^,i' e q s

V[/" = R"I, ,

Eddy current series resistor is

Overall eddy current losses becomes

W" = k,Irol,AerB,^'f'

Approximate flux level is dominated by injecting current, or

MB = u o u r ! - l

I' e q

Hr9

PoweFLabHKu

The equivalent resistance of the ring can be described as

) r rn

r ) e l

1\.t, = -;-----; 1"" = e/fective length rdthe magnetic circuitK R l , ,s x d r

The overall losses is the summation of each ring, hence

Prepared hy Franki Poon & Boan Pong

EMI in Switching Power Supply wv eee. hku. hApwer _e learcnq -l ob/

'w\|.eee.hku.hApower:4eanhrca_iah/ :62

Power.Lab HKU

Total losses becomes

W, = (Rn+Ro) I , . . r 2

and, , , , , r r ]

D I t \ - t - ' t t ) L ' t " t V O I '

,t t 1 , \ J ) - Nh - - ] __ -7 - Jlu, - . r-

L(0

R,(J') = k"uou, .N2Vol . ,Ae. ,

, 1I nq -r-

J-).

Rn(O

fi P.epare<t hv Franki Pcon & Bman Ponq

*L t.Ut in Swtchtng Power Suppl.v \rw \|. eee. h ku. h ly'powe r _e I e c t m n t6 -! a b/

PoweFLabHKu

t.I te -

Wror"rfrB ,r'

: the coefficients

-Wroor. f rBr '

-f, fr 'B ort B or'Ae,vol,- -fr' -frB or' B or' Ae,vol,

k n =w ror"r fr' B p22 - w rorrrfr'� B r'�

-frfr'B or'B rr'vol, - -fr'"-frB or'B ortvol,

Fflr-!tPrepared bv Frcnki Pcon & gryan PonL

E'Vl in Swilching Power Supplv

Ferrite losses

'ee\|.cee. hku.hAtu\eer electbnics idb/

tI

Power'Lab HKU

Ferrite losses- some approximated idea

c € l ( a n d € F

Prepared bv Franki Poon & Bilan Pong

EMI in Swrtching Power Supply ww. eee. h ku. hUpoqr clec trcn i6, ab/

Power.Lab HKU

Series resistor can bemuch higher thanwinding resistance,

Inductance fall at around

N=707

HSCZ T0mmtorcid

A. = 0,07 cm2

L" = 2'2 cm

Prepred hv Franki Poon & iJnan Pong

EMI in Switchine Power Supplv

- lnlorwleld qu@bnl sfrt @ra bttat dgstafta- lntwlet& hdrctercc

S€das c@ bJs rusblrnct

\wweee.hku.hUFnwer_electmnrcs_lab/ :66

Ferrite losses resistor

0n

il6'

r r r f '

T

*.k

TI!Tt!FTFlFFFrBh

Fh

t '

h!t

Frequencydependent - any difference?

N=7OT

7Omm toroid

A. = 0,07 cmz

Le = 2.2 cm

1,000 times difference betweenfixed and frequency varyingparasitic

0.1

r . 1 d

r . r d

g r . r d

, 1 1 0

e r ' 1 0

Power*Lab HKU

Prepared by Franki Poon & Bdan Pons

EMI in Swtching Power Supplv

Power.Lab ilKu

Typical example

Power.Lab HKU

EMI is different - typical example

50 pfVpeak =4OO V

T r = 5 0 n s

T f = 5 0 n s

P w = 2 u s

Per = 5.6 us0.03 pf

Resonate occurs due to Land C, But you seldom seeresonance after adding

{01i ,i0{} : S L! i.rl i;Kr ii$r

269

Prepared hv Franh P,ton & Bryan Pong

EMI in Switching Power Supply ww. e ee. h k u. h A lnwe r -e I ec r rcn i t _! a b/

ground choke.2200 pf

2 5 u H I

25r l

0.5 pf

0.4 mH 0,1

htttIbI-

tITT

EMI is different - changing L and CThe inductor change it's value atwhere it should resonate. Dampingresistor increase at resonatefrequency

Prepared bv Franki Poon & Edan Pong

E,VI in Swtching Power Suopl.v

- shi€ld & tilteQd CM noise without FGq. paremateE

CM noise with Frcq. dependent lilter

vww eee-hku-hl</gtwer Jlectronrcs _iah/ :70

50 pf

2200 pf

2 5 u H 1

2:t n

o.5 pf

r|

ThI

-

PoweFLabHKu

Changing L and C - no more simple

Prepared hv Franki Poon & Bryan Pong

EMI in Swilching Power Supply ww. e ee. h * u. h l</powr _t I e c t rcn ru _l ab/ 271

prediction

22OO pf

2 5 u H 1

25 r l

0.5 pf

Filter designp 1 -

minate

. S t e p 2 -order

Power.LabHKu

I

+ Example 2 - ferrite beadRsirlo8e d hhctMel Log.tdlc)

oX

A small ferritebead givesalmost 1O flat 10O MHz,while keeping0.O1O only at10O kHz.

o r . r l , . r o o r . r o j r . r d ' r . t o 7 r . r o * t . r o )Fary(os@U

- Equiwlat con lw s*iq rcbtwc* E_futiye indactwc agai8t ftqu^cy

Core {oss seria rqisrance & lndrctmce agairetlrequency

ff i PrcW.i bv F.dnh Poon & Boan i 'onq

d]\, E,UI n Swtrchinq power Supplv tww. e ee. h ku. h A trnwer _e I e c t mh Es -l o b/

PowercLab ilKu

E x a m p l e 3 - s e r i e s C M C

5O pf 5 p f

High u,for high impedance atlow frequency

ffi Prepared hv Franki P,rcn & Bman Punq

E , EMI n Switchinq Power Supply

Low arfor high impedance athigh frequenry

www.eee.hku.hUptwerelectmniulab/ :73

PoweFLabHKU

Series CMC - cheap alternative

50 pf 5 p f

High n for high impedance atlow frequency

Prepored bv Franh i,oon & 9ruan Pon(

E,Vl in Swnching Power Suppllt

Low stray capacitpor formedium impedance at highfrequency

www tee.nku.hldwwer electnnics lab/ :71

rl

TI

r|I

hhttttt

PoweFLab HKU

I"'q[ Short SummaryPermeability of a high permeability ferrite usuallystart to roll off at around 200kHz.So it usually give maximum impedance at thatfrequency

. Resistive Losses can be very high depending onM and P.The equivalent loss resistor pay a great role infiltering design to provide damping effect.Magnetic material do not work on the way Iapproximate. It is more complicated and highlynon-l inear.

ffi P.ewrecl bv F.onki Poon & 3mun Ponq

I!, EMI in S.ttching Power Supptv \ww. e e e, h ku. h Apowr _e I ec r ro n i6 _l a b/

PoweFLabilKu

finy uhtfiqutntion?flB{lt

t>repared bv Franki Poon & Boan Pong

E.Vl in Switchinq Power Supplv 'n \|. eee. hku. hkrwwer jlecrmntcs _iab/ :76

Power"Lab HKU

Radiated emissionI

d sJrl - / , a l l

\ / [ ]

Radiated emissionis transmitted andreceived by anantenna.

Prepnred by Franki Poon & Bryan Pong

EMI in Switching Power Supply "vw. eee. h ku. hUpower el ect rcnt6 | abl

Power.LabHKU

I

5k Antenna theory 1

l lr 1 l

6-'.Jt'I

Il , orr"l= 1.261' f lJo'" uv / m

t. E

_LfrllilA

Hq!?Prcpared hv Fronh Pooh d EDdn pong

EMI in Switchiaq Power Supplv 'ww.eee.nku hhpwcr tlecrnnrs tab/

III

, d ,

I J rIl tt

-\I

t t nI t t t

. l = t ) 6 '' ' r c

tared bv Franki Poon

I in Switchng Pou

r|hhh

f l

hth

I

hhlhItIIIII

Antenna theory 2

| | , , , f l r t '

lu,,, , ,r l= l i l 6x lo-t ') | ' , ! ' t tv ' m

cl

I

9-Jq lt lt l

E

Preryred h)' Frcnki Poon & Bryon Ponq

EMI in Switching Power Supply ww. e ee - h ku. h Apowe r _e I ec t rc n tu -l a b/

Dipole - capacitive like antenna

rww.eee.hiu.hl4utwert lectrcnrcsluir / )80

o.31pf--/

ww. eee. h ku. h Apowr _e I e c t rc n i cr _l a b/

PoweraLab HKU

ol;;}__{ill l \ - / l- - l

I tPrepared hv Franki Poon & Bdan Ponta

EMI in Switching Power Suppll,EN.ila

r|r|tr|r|r|r|r|tIIIIIItttttt

Cable and converter - 10m simulation

lz o,r","l= t.zo I fli''" uv t *s rd r.rd r.nO z.d z.srf

FBq@rcy- C|SPR22 ndieted class B limit lins- 10m radidtad noise amt trcm dipole

10m rcdiated noise generated by cabte

rww cee.hku.hlapower _,4ecrmntcs _lob/ :82

Limit Exceeded !!Vp€ak =40O

T r = 5 0 n s

T f = 5 0 n g

h v = 2 u s

Ps = 5,6 us siq

*

r0.31pf

PowePLabHKu

fi P,epared bv Fronki ?oon,l Bruan I'ong

V, E.Ul n Swtchrnq Power Suoplv

Power.Lab HKU

tE

l - | , ^ t 2 . 1 1 'lE r " r l = l 3 l . 6x 1g - t v ! - - ! ! - uV t m

I P.eparetl bv Franki Pun & Bddn pong

) E,VI in Swtching Power Supplv 'Nw. cee. hku. hvwwcr c I ec I mn t6 I ub./

ttth-

IIT

Power.LabHKU

Loop antenna - current source excitation

f., ,-, = O.5A

C-*=o'ae 7tr=So ns A \tr=f lons (f l)r=o.oooz)t * = 2 u s \ 6 : /T= 6.6us

\.-/

Very very little noise isgenerated

| | . . t 2 l t '

, E n u o l = l i I . 6 ^ 1 0 - t ' t ' " " t t V i md

ssE

s.rf r.rd r.1rd z.i z.stl :.rdtsaq@ncy- C|SPR?2 nidatad clas I limit line- 10m radiatdd noise emittad frcm cui€nt source toop

10m radiated noise by loop antenna

'ww eee.hku.hAgtwer 4ectruntcs lob/ :81fi

PreOmd bv F,onki poon & Bruan pon!

V, E.Vll n Swiching Powvr Suopl.r,

Power.Lab nKU

Loop antenna - voltage source excitationLimited excessiveemission due toresonance of the loop

100 nHVpeak =40O V

...i,\rar.T r = 5 0 n s

rf = so ns f?f n=O.OOOZIP w = 2 u s Y t ' f

1OO pfPer = 6.6 us

0.5

, r , ^ l ' | l t '

lg , . .^- l = i i I .6 x 1g- to J '11 , ,v 1 .

| ' " " P 1 d

a

ili iltl l^i/y

Prepared hv Franki Poon & Bn'an Pong

EMI in Switching Power Supplv

s . rd r . rd r 5 rd 2 . f i : . : rd ; rdFrcquency

- C|SPR22 raidated class I limit line- 10m rcdiated noisa emilled frcm voltage source ioop

.1Om radiated noise by loop antenna

ww.eeehks.hupow.r_elecrrcnis-lab/ :8J

IIIItIrt

PowerlLab \KU

Converter cable will pick up thenoise current by mutualinductive couple.

fi l,rorur"q 5, p,anxr ltrn & Bnan pont

l#. t,Ut n Swilchmq Po\|er Suoplv

Dipole antenna - an amplif ier

ss

:

loop noise and becomes thedominant emission antenna

*1d tad r5rd z'rd 2s10 r.rdFEq@Ny

- C|SPR22 Ediatad class I limit line- Noise emilted frcm cable drivan by curent dnven loop

- Noise emittad by curenl diven i@p only

Cable ndiatad no6e by nductive couple)ww.eee.hku.hUpower-elecntnrcs_iuh/ :86

Power.Lab nKu

Cable and converter - suppression

l il r i1 . . . i . .

A iY i/ :

\ > i\ i

6 i

By passnoise \current

Small CMC

Prepared bv Franki Poon & Bman Ponq

EMI in Switching Power Supply ww. ee e. h ku. h Apow r -e I e c t rcn iu _l ab/

IIthItT

Power.LabHKu

Loop antenna - suppression

Ferritebead

Add ferrite bead atthe current loop

Ferrite bead

t'repsled hv Franki Poon & Bdon Pong

Elvll in Svtching Power Supp$, ^Nw cce.hku ntlpowcr ,:lcctronics ,tb/

PoweraLabHKU

I

Th Short summary. F

. Cables generally emit more noise than loop

. A loop can emit substantial noise atresonate condition.

' A cable acts as an amplif ier & picks up noisefrom a loop close by and emits at a muchgreater level.

' Impedance with small stray capacitance andhigh resistance can reduce radiated noise.

Preparerl bv Franki Poon & 9ryan Pong

EMI in Switching Power Supply rww.eee.hku.hk/power_electtuni6 _lab/ :89

Power"Lab HKU

radiated EMI

vii-t,

Predicting

I

ItIII

Assuming input and outputcable are the same and thereceiving antenna is 10maway

,, 254 E ti.,, , noY ttsN nF Linit =:=:-:-lu-L./.O Jl cabte

rfla

Arti f icial Limit l ine of CISPR22measured at LISN

rrd rril r.sd z.tt zsd^ FQq@rcy

- AtTificial class E limit line for 1m cabtee Aftificialclass B limit line lor 2m cable* Atlificial class B limit line for 3m cabla

Atlilicial rcdiated class E limlt lne

\!w. eee. h ku. h lq pow r -e I ec | rcn E\ _i a b /

so

s

r|IhhhI

Fh

nII

It

rrd

Power.Lab lrKU

Misc. - Predicting radiated EMI

J ,,,_o

As E field is generated by adipole

I t t ll - | , ^ . ' J ' n o l , '

lE Lir"ul= | '26--:--::::-uv I m

The corresponding current l imitf lowing in the input cable is

t r )| - u L t m r t " r n t lr | , - ; r - - t V

I .26 JI , obto

The corresponding voltage l imitmeasured at the USN

v'ri-i,

E6-1fi> r'u-it4 vii-i, t/E L',,,dZ L's,u ,_

1 0 6I .26 / l c ,b te

ffi Preporecl bv Franki Poon & Bdan p.nq

\fi E.Vl in Swrrching Power Supplr vww. eee. h ku. hUpower e lect rcni6 lab/

JqMrIz -230MHz

230MHz- tG

fuasi peak linit(l0n I SOaAuVclass 8) ',

im37dBuV/m

Prepored hv Franki Poon & Snan Pong

labi :92

Powel.Lab HKU

firry shufiqunntjon?H Preparecl by Franki Pnn & Bnan Pong

EMI in Switching Power Supply wveee.hku.hUpower_rlectrcnt*_lab/ :9J

Powet LabHKU

MISC - Cancellationv,

F

A full-bridge configuration has an inherentcancellation ofvoltagesring. The left leg will having an egud but opposite swing comparedwith the right leg.

H{t

Prepored bv Fronki l)oon & Bdan pong

EMI in Switchine Power Suoplv .ww aee. hku. hlvoower elecrrcnics ldb/

tI

II

Power.Lab HKU

I.,, ---\.,, C, * = Ca t- _ l _ | -

Then,

Vvictim = O

Prepnred bv Frann Poon & Bnon Pont

EMI in Switching Power Supplv w w. e ee. h ku. h Apowr _e I e c t rcn i u _l a b/

Power.Lab HIKU

MISC - capacitive coupling cancellation

A two wheeler forward or flybad< configuradon has an inherentcancellation of voltage swing, The leS leg has an equal but oppositeswing compared with the right leg.

ffi ?n'oarea bv Fronki P,,rn & Bnun t'nng

V E.VI :n Swtkhtnq P,twer Suppiv .w\9 ee.hku hvpower _,:lectmnics _loh/ )96

PowefLab HKU

A general method forvoltage cancellation canmake use of an anti phasewinding to complete thetask.

.1Tt^';'-L4.'-t^"\-

t- ,-- II lbooorn | |l 4 l

Prepore<l bv Fronki Poon & Bryan Pong

EMI in Swirching Power Supply w w - eee. h ku. h ll pow e r _e I e c r rcn i a _l a b/

PoweFLabHKu

MISC - capacitive coupling cancellationA 20 ns delay wil l el iminate thecancellation effect at 10 MHz

/5it) = Vs1(t+;0 ns)

Be careful withtime delay !

P,"pur"d hv Fronki P^on & Btuon Pnns

E.Vll in S)eitchinq Power Suoolv

' . r ld r .rd rroT r.rdFaucty (LoE iut.)

- ,Yomalized spectrun o[Vg1

- .\lomolize<l specttun ol VSI(|)-r'St(tsTd)

Yonaii:e<i notse source spectrum

tw\|.eee.hku.hldpowerllectronrcs_iab/ )98

Powel'Lab HKU

A single frequency injection into to a receiver make the detector producea dc voltage output with ripple where the peak, quasi-peak and averageare the same

Prepnreu hv F.anh Poon & Bnnn Pong

EMI in Switching Power Suppl;t t*w- eee- hku. h Apowe r _e I ec trcn i6 _l ab/

PoweFLab HKL)

Misc - Frequency jitter-ingO.SHz

7,7fs

lower value.

Prepared bv Franki Poon tl B^,an Pong

Etr4l in Switching Power jupply,

avaragad valueforfrquanty.mdubdott

7/f_

A changing frequency injection into tbe receiver make the detectorproduce a pulsing output voltage where the averag€ value will have much

,ww.eee-hku.h l tDo\ |e r r lec tmncs \$ / j00

ItIIr|

I

PowereLab ilKu

, l| -----_I.t L . \ \ \ \ lr * - . l

Band pesJfilter movingalong thefreguency axis

f{t)=fs+l/2kpwx(t)

. . . . . . . . . . . . . . f t .

time for a frequency changing signal

: : : : : f: : : : :: : : : !

i i : i :

Envelop det&tor output against time for a t. frquency changing signal

rrepared Dv r fonkt roon & a^'on Ponp

EMI in Swtching Power Suppl.y |9w\9.eee.hku.hL/power-electrcni6-tab/ i0r

Frequency

Power.Lab HKU

Don(fBW) = normalized averagevalue at the detector output

' 8 Wi l + -

Donlf a*) = l ui, Pdf (f)dJf"J -_;

The frequency jitte? in a way

"f :.fs + l/2kpWsin(2nf^t)

The probability density functionof the operating frequency is

The average value undera sine wave modulationwill have a factor shownbelow

es

Pdf (f) =' - a s r f - . r s r d _ ' s s r d ' o r d6eno pass illeas centof trequency

Averaged Btio kf=2 BW=gkHz

I'reparel hv F tonkt Poon .l tJwan Ponq

EMI in.Switchtnq Power Suoplt,

Average ratio

'qvw.*e-hku.hkio,twerjlectronrcs,iob/ 102

PoweFLab fiKu

n n/ \ / \/ \ / \Linear type modulat ion

A A ^ l \A t \I V V V V V \

White noise modulat ion

t \ A ^ i lni \I V V V V V \

Chaotic type modulation

Prepared bv Franki Poon & Bryon Pong

EMI in Switching Power Supplv

Yield flat frequencydistribution

Aqflwww. ee e. h ku. h Upaw r _e I e c t rcn i t _l a b/

PowefLabHKu

Band ,ass ftItermovealongftquancyaxb

f{t)=b+Y21pg1rr,

tII

Frequency will overlap at high frequency range.

H l'rcFzreti bv F,ankr Phon & 3ryan pong

& E,Vfl :n iwttshinq Power \upplt 'ww eee.nku.nlopower _. lectrcnrcs _ ao/

Power.Lab HKU

Misc - Frequency' f itteringIf f- << time constant of peak orquasi-peak detector charge time

f,(t)=fs+l/2kpwx(t)

. . . . . . . . . . r i '

Band passftlter movealongfrequency axis

Don't be cheated by the spectrum screed !Prepored hy Franki Poon & Bryan Pong

EMI in Swttching Power Supply ww. eee. h *u. h A power _e I ec t mn iu _l a b/

Frcquen.y

' 1 . . . . . . . i . . ! . .

:

IIIIIII

Power.Lab HKU

I

3k Input cable*]*

Refresh

Cy = 22oo pf

Prepared hv Frunci Poon & gruan Pone

EMI in Swuchrng Power Supplv ww. eee. hku-n Hytwer _el ectmn tcs.�l ab/

No input cable parameteris considered.

No problem !

t . &

cMC = 20 mH +0.5n// sopf

*=

/'I

: t t i r, 1 ! i :

Hr:!t

Power.Lab ilKU

l -.-qh Input cableInput Cable

Input Cable

usN ZI

'F -4Cy O'37Pf

Consider theinductance ofeach wire

Prepare.l hy Franhi Poon & Brvon pong

EMI in Switching Power Supplv ww.eee.hku.hk/pwet etec,rcniq lab/ j07

L2 Z )} -d-tacv T ' o.3

Power.LabHKu

I

=b Input cable

A I

l, = 0.002/(ln (L - o.l r)"n" d

For a 1m cable

l = l O O a n

d =O.7 qn

hene

L = 7 , 5 u H

Input Cable

H ?rcpared hv F.onkt po(,n & Bruan pong

{ LVI in Swttchtnq power jupplv .vww eee nku nlowrver ,lcctntnrcs .,tnt

rtIIIIIIIIItIhhIIttIIr|

Power.Lab HKU

.sP! - rrR*tvfBi*o

ut cable - cEble inductance

: I i : N . t { 0 r r : . t x . K ,: I tS i i )

Prepnred bv Franki Poon & Boan Pong

EMI in Switching Power Supply

J0(! {0sr i08n i.Nr: {u l in i : t

tFtrrr

w. eee. hku h lupower -e lycrmn tu _, abi

f , t ' . i l t : i s l

J09

PoweFLabHKU

Consider themutual and selfinductance of theinput cable

2 t wLtz = 0.0021 (1n(:) - I + --)uH' ' w ' I 'Fora 1m cabl€

I = 7(XI otr

W= O,4cm

hence

L p = 7 u H

Input Cable

H P.eparea hv F.ann poon d Sryan pailq

$ E.VI n Swrrchnq Power Supptv wbree.hku.hfupo\'er,clecrmnta_lab/ II0

Power€Lab HKt

FIIr|r|IIIIIIIIIIIIItItI

ri l : , i l .r. i f i ,a i 0-r. I ft i : i h tryi. i I

: i L J , 5 r . . .

Preparel h.r' Franki Poon & BDan Pohg

EM m Switching Power Suppit w w u,. eec. h k u. h lu powe r _e I e c t rc n i ct _i o br--'it-€t

Consider themutual capacitor,mutual and selfinductance of theinput cable

Input cable - inductance & capacitor

r_ 0.08851 trc,c - ' n F

w rI / ^ .t n r / _ I

t la

ffi P.eforcd h, fronh Poon & Boan pong

$rr. - €,lZl i" Su itchtng Power Suppl.r

For a lm cable

l = l O O c m

W = O . 4 c m

hene t

C = 5 4 p f

w _

Input Cable

27 pfeach

Power.Lab HKL

27 pfeach

tlusNl i

lL2r-|..T.. :.

I c i '

+Z Z :I

-h

Z-T

cy T ' 0.37pfCy

wu eee. hku. h Alnwer _electrcn ics *lab I

PowefLabHKU

cable - inductance & capacitance

i0r,

i ! [ i

PoweFLabHKu

able - inductance & capacitance

frqu?rcDafea bv Frankr Prytn & Bruun t'onc

EMI in Switching Power gupply

Input c

Solution6vw eee. hku. hl(po\9er eiectrcnrcs lab/ J H

PowefLabHKu

I

ah Short SummaryI F

. An anti-phase noise source is a possiblesolution to eliminate noise.

r Frequency j ittering or modulation canreduce average reading.

r Input cable construction contributes tonoise distribution pick up by the LISN.

'ffi Prepared bv Franh Poon & Bnan Ponq

V EUt in S.itching Power Supply w.eee.hku.hupowr-electtuni6_lab/ I 15

PowefLabHKu

Faraday shield produceemore invisible loops

Prcpdred hv Franki i)oon & Snun l'ong

E:VI in Swtching Power Suoplv

Good or Bad ?

.t'ww.eee.itku.hlloower llectronics ;db/

Power{Lab HKU

D'courea hr F,anxt P.on d Brttn p ,ny

EMI in Switchinp Power Suopiv

Add choke or CMC will pick up more noisee

IIr|r|IIr|r|

PoweraLab |KU

Increase number of turns will increase straycapacitance

ffi Prepared hv F,anxt pun & Bn,an pong

Sj E,Vt in S-rching Po\9er Suppl.y w\'. eee. h ku. hApo|9e r _e I ec I m n i6 -l a b/

Good or Bad ?

Good or Bad ?

6ew tpe .nku Fboo\ tp r . re (mntc t ab j l ) l

.Lfg;+.=�ffi

MWffi*wwffiffi?

Power.Lab HKU

Pr'pared hv !1nil !'hn & 3Nrn ,,an\

E.lll in Switchinq Power.\upplv ,ww eee. h ku. hH N\9er t I ec tio nics I abl

Question ?

Ir|FhhhhhhhhtIIIthIII+l

ffiMffiffiffimm

ffi P.epared hv F,onki Puon & Bnan pong

$ t.Ut in Switcning Power Supplv wv eee. hku. hUpower clectroniu lab/ J I 9

PoweFLab nKU

PoweraLab HK:],

Statement 1 - All my corect solution doesn't work

Statement 2 - If there exist a solution

Logic derivation - The solution mustbe incorrect !

H Prcpared bv Franki Poon & Bman Pong

$ EUt i" Snirching Power Suppl.y w.eee.hku.hApowr_electrcnis_lab/ 321

Simple logic

PoweFLabHKIJ

Sometimes we have to

*$s$d*t

Preoored bv Franki Poon d Eoan Ponl

EMI in Switching Power Supplv

1:>j

ww. e ee. h ku. h A powe r -c I e c t mn rcs _l a b/

r|FF

IhI

IFFhhhtTtI

t

Pow€l'Lab HKU

Overall SummaryEMI behaviorsummation ofdiscussions.It is never anEMI result.

iS,a l l

at least, aof the above

I easy task to predict

Better understanding helpprevention and diagnosis.

g Ptepared hv Franki Poon & BNon Pong

EMI in Switching Power Supply w. ee. h ku. hApwr -e I ecttu ni6 -l aU

Power.LabAKU

Prepared bv Franki Poon & Bryon Pong

EW in Switching Power Supplv w eec.hku.hvpower clectrcntE lail

t1l, Tim Willlam, EMC for product Designers, Butterworth-Heinemann Ltd.1994

l2l. Jeffrrey P.Mill, Electro-magnetic Interference Reduction in ElectonicSystems, PTR Prentlce Hall, Engl€wood Cliffs, Ncw Jers€y 07632, 1993

t3l. Mark D. Herema, Designlng for Etectrrmagnedc Compatlbility, Hp1l949BH€wlett Packard.

t4l. Dongbing Zrangi Dan Chcri Sablc* D. NorlndnCc dlttbrenth&modG rotsocauscd by ground cur"entln anol?-ltnerpowersupptr. Irowcf,El€cEonb+adaltrtgCon ercnca; 1998; pESrC 9& R€co|tL 2g{t}Annual IEEE volumc3 2r feeC^ fag!(q;ltilt-ltlXlvolz j. .] -

I51. \tei Zhang; Zhang, M.T.; Leq F.C; RoudcG,Jt ChvchE,CondudElf!aralysb of a boost PFrcdrcl|it, Applt€d porH Fl€eb.onk*Con{brtncrandEqdtfonr1997. APEC'97 Confer€nce Proce€dlngs 1997., TWellUr Annual Volume-; t,';ggt ,Page(s): 2Il -229 vol.l,

Reference

hTTttI

PoweFLab rrKU

I-o[ Reference

i5l. Ferreira, J,A.; Willcock, P.R.; Holm, S.R., Sources, paths and traps ofconducted EMI in switch mode circuits, Industry Applications Conference, L997.,Thirty-Second IAS Annual Meeting, IAS '97.,Conference Record of the 1997 IEEE,Vofume: Z, L997, Page(s) : 1584 -1591 vol .2,

17l. Qing Chen, Electromagn€tic interference (EMI) design considerations fora high power AC/DC converter, Power Electronics Specialists Confer€nce, 1998,PESC 98 Record. 29th Annual IEEE volume: 2, 1998, Page(s) : 1159 -1164 vol .2,

t8l. Pong, B,M.H,; Lee. A.C,M., A method to measure EMI due to electric fieldcoupling on PCB, Power Conversion Conference - Nagaoka lgg7,,Proceedings ofthe Vofume: 2, L997, Page(s) : 1007 -1012 vol .2

tgl. Pong, M.H.; Lee, C.M.; Wu, X., EMI due to electric field coupling on pCB ,Pow€r Electronics Specialists Conference, 1998. PESC 98 Record, 29th AnnualIEEE, Volume: 2, 1998, Page(s) : 1125 -1130 vol ,2

[10]. David K. Cheng, Field and Wave Electromagnetics, Addison Wesleysecond edition,:1989

Prepared bv Fronki Poon & Bryan Pong

EMI in Swttching Power Supply ww.eee.hku.hlt/power_elecrrcniu-lab/ J25

Powet"Lab HKU

[11] , Ninomiya, T. ; Shoyama, M.; Chun-Feng l in; Ge Li , EMI issues in swi tchingpower converters, Power Semiconductor Devices & ICs, 2001, ISPSD '01.

Proceedings of the 13th International Symposium on , 2001, Page(s): 81 -86

[12]. Rossetto, L.; Buso, S,; Spiazzi, G., Conducted EMI issues in a 6OO-Wsingle-phase boost PFC design, Industry Applications, IEEETransactions on,Volumes 36 Issue: 2, March-April 2OO0, Page(s): 578 -585

t131, Gitau, M.N., Modeling conducted Ett{I nois€ gen€ration and propagadon inboost converters, Industrlal Electronics, 2000. ISIE 2OO0. Proce€dlngs of the 2OOOIEEE Internadonal Symposium on , Volume: 2 , 2OOt0, Page(s): 353 -358 vol.2

t141. Cacciato, M.; Cavallaro, C,; Scarcella, G.; Testa, A., Effects of connectioncable length on conducted EMI in electric drives, Electric Machines and Driv$, 1999,Int€rnational Conference IEMD '99, 1999, Pag€(s): 428 -430

[15]. loshl, M.; Agarwal,"'1r,, GdltGftlon and prcpagaHon of EMI way€r inpowe. electronic circuits, Power Electronics Specialists Conference, 1998. PESC 98Record, 29th Annual IEEE, Volume: 2 | L998, Page(s): 1165 -1171 vol.2

f i Prepar"a bv trdng o /)n, t 3oan P.ns

&5 f .W in Swuchtnq Power iuaprv \w\'.cee.hku.hldpo\|er electnnics !db/

Reference

PoweFlab HKU

Prepared bv Frunki Poon & Bruan Pong

E;VI in Swirching Power Supply ww.cee.hku.hluwwr electrcnts lab/

!rei. okyere, P,F.; Heinemann, L., computer-aided analysis and reduction ofconductedEMI in switched-mode power converter, Applied power El€ctronics conference andExposition' 1998, APEC '98. conference proceedings 199g., Thirteenth Annual , volume: 2,1998, Page(s) : 924 -928 vot .2

[17]. Ferreira, J.A,; Willcoclq p.R.; Holm, S.R., Sources, paths and traps of conductedEMI in switch mode circuits, Industry Applications conferenc€, 1997, Thirty-s€cond IAsAnnual Meeting, IAs '97., conference Record of the 1997 IEEE, volume3 z', LggTt page(s):1584 -1591 vol .2

i181. Wei Zhang; Zhang, M.T.; Lee, F.C,; Roudet, J.; Clavel, E., Conducted EMI analysis ofa boost PFC circuit, Applied power Electronics conference and Exposition, 1997. ApEc'97conference Proceedings 1997., Twelfth Annual , volume: | , tggT rage(sj: 223 -z2g vol.r,

!rg:. Bardos, P.' Predicting the EMc performance of high frequency inverters, AppriedPower Electronics conference and Exposition, 2o01. ApEc 2001. sixteenth Annual rEEE,Vofume: L ,2OOt, Page(s) : 213 -219 vol .1

Reference

PoweFLabHKu

Prcpared bv Frantt Poon & 7n,an ponc

E,VI in Switching Power Supplv ww. eee. hku.hlc/mwer -electonrcs _iab/ Jld

II

"- I P aforc' ? t t r l \ l s l t g l \ -rss rnce

t2ol. Laboure, E,; Costa, F.; Gautier, C.; Melhem, W., Accurate simulation ofconducted interferences in isolated Dc to Dc converters regarding to Er.rIstandards, Power Electronics specialists conference, tgg6, prscig6 Record.,27th Annual IEEE , Votume: 2 , !996, page(s): 1973 -1978 vol.2

!211, Knurek, D.F., Reducing EMt in switclr mode power supplles,lgt^aolmulications Energy conference, fggs. fNfeLiC ,ee., 16ih Inierna$onat ,1988, Page(s):411 -4ZO

l2Z!. Poon, R,K.; Liu, Cp.; pong, M.H, Leastcoupltng paths model fur non-contact EMI base on lump element approach ln swltch moie converter. pow€rElectronlcs speciarlsts conferenc€, 2ob1. pEsc, zoot rEEE 32nd Annuir, volumo.2 , 2AOt Page(s): 577 -SB2 vol.2

LZSI. .- _Paolo Tentl, Giorgio Spiazi, One-day Course ofi €l€ctromagnedcCompaUbility in Industrial Equipment: Stand#d, problems and Soluuon, IEEEHong Kong Joint Chapter of power Engineering, Industry Application, powerElectronics and Industrial Electronics Societies, 25 Feb. 2OO2

[e[e, lmlsspuallf,

Prepored bv Fr@hi Poon & |ru@ Pong

QI E,V] i, Sn rching Power Supplv ww.ue.hku.hvpowr_electtuni$_lav 329

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