AnalyzethevalidswitchpowersupplyelectromagnetisminterferencerepressesthemeasureTakeofftowant:Thistextanalyzestheswitchpowersupplytoproducethemechanismoftheelectromagnetisminterferencefirst,,afewvalidswitchespowersupplyelectromagnetisminterferencemeasurecarriedontheanalysiscurrentlycomparison,andputforwardthereferencesuggestionforthefurtherresearchoftheswitchpowersupplyelectromagnetisminterferenceKeyword:TheswitchpowersupplyelectromagnetisminterferencerepressesthemeasuretomatchCurrently,manyuniversitiesandtheresearchunitsallcarriedontheresearchoftheswitchpowersupplyEMI(theElectromagneticInterference),theywinsomemechanismthatproducesfromtheEMItosetout,somefromtheEMIproduceofinfluencesetout,allputforwardmanypracticalworthyprojects.Thehereisanalyticalwithcomparedafewvalidprojects,andrepressthemeasuretoputforwardthenewreferencesuggestionfortheswitchpowersupplyEMI.One，thecreationmechanismoftheswitchpowersupplyelectromagnetisminterferenceOutputinterferenceoftheswitchpowersupply,pressaninterferenceofsourcecategorytodivide,canisdividedintothediapasonaninterferenceofthepeakinterferencetwokindsof;ifmatchthethoroughfareaccordingtothetodivide,canisdividedintoconducttheinterferenceandradiationtheinterferenceistwokindsof.Pressaninterferenceofsourcetocometoexplainrespectivelynow:1,diodeofanti-towardtheinterferencethattheinstaurationtimecauseThehighcommutatesthebacktrackinofcommutateahourofpositiveguideofdiodetoisbiggerjustflowthroughtowardelectriccurrent,atitbesubjectedtoanti-bepartialtotheelectricvoltagebutchangedirectiontoclose,becausehavingtocarrytoflowthesub-backlogmorelyinthePNknot,asaresultincarryflowsub-disappearancepreviouslyofaperiodoftime,theelectriccurrentwouldbeanti-towardfluxion,causingcarrytoflowthesub-disappearanceanti-toreducetowardnastyplayoftheinstaurationelectriccurrentbuttakeplacetheverybigelectriccurrentvariety(di/dt).2,aninterferenceofthathourofworkproduceoftubeofswitchThepowerswitchtubeflowsthroughthebiggerpulseelectriccurrentwhilelead.Forexamplejustarousethetypeandpushaformoftheimportationelectriccurrentofthetypeofandthebridgetypetransformationmachineattheloadlooklikefortherectanglewave,amongthemimplyaweightofabundanthigh.Whenadoptzeroelectriccurrents,zeroelectricvoltageswitcheses,aninterferenceofthiskindofwillbeverysmall.Moreover,thepowerswitchtakecareofduringtheperiodofclose,thehightransformerofroundsanelectriccurrentmutationforleakingthefeelingtocause,alsowillproducethepeakinterference.3,exchangesimportationinterferenceofthebacktrackcreationTheswitchpowersupplyimportationthathavenoworktransformercarriestocommutatethetubeatanti-willcausethehightoreducetoflaptobecomebankrupttolivingtheinterferencetowardperiodofinstauration.Harmoniousinterferenceenergyoftheswitchpowersupplyoutputpeakinterference,theimportationthatpassestheswitchpowersupplyoutputsthelinedisseminationtogooutbuttheformativeinterferencecallitastoconducttheinterference;butwaveofandliveontheenergyofflapthe蕩,passtheimportationexportationlinedissemination,willproducetheelectricfieldandmagneticfieldsinthespace.Thiskindofiscalledtheradiationinterferencethroughanoutputinterferenceoftheelectromagnetismradiation.4,otherreasonAmachinepiecelivesontheparameter,theprinciplediagramoftheswitchpowersupplydesignnotenoughperfect,theprintingcircuitplank(PCB)walkthelineusuallyadoptsthehandicrafttoarrange,haveverybigatwillsex,thePCBaninterferenceisbig,andprinttheplankupthegearingofthemachinepiece,place,anddirectionsofnotreasonablewillresultintheinterferenceofEMI.Two,thecharacteristicsoftheswitchpowersupplyEMIBetheworkintheenergyconversiondeviceoftheswitchappearance,theelectricvoltage,theelectriccurrentvarietyrateoftheswitchpowersupplyisveryhigh,theinterferencestrengththatproducecomparegreatly;Theinterferencesourcemaintheconcentrationisinthepowerswitchperiodandspreadthehotmachineandhighandeventransformersconnectwitheachotherwithit,oppositecompareinthepositionofthenumericalelectriccircuitinterferencesourceclearly;Theswitchfrequencyisnothigh(fromseveral:,andthefewtrillionHertzs),themaininterferenceformistoconducttheinterferenceandaninterferences;buttheprintingcircuitplank(PCB)walkthelineusuallyadoptsthehandicraftclothline,havelargeratwillsex,thisdifficultythatincreasesthePCBtodistributetheparametertowithdrawtoestimatewithaninterference.Three,theEMItesttechniqueExamineapatientthreekindsofmethodsofthetotalmoldinterferenceofbadmoldcurrently:Theradiofrequencyelectriccurrentstretchforward,thebadmoldrepressesthenetwork,thevoicetoseparatethenetwork.Stretchforwardwiththeradiofrequencyelectriccurrentistomeasurebadmoldtotalthemostsimplemethodinthemoldinterference,butmeasureresultlimitvaluewithstandardtorelativelywanthasbeenconvertedcomplicatedlymore.Thebadmoldrepressesthenetworkstructuresimple(seethefigure1),measuretheresultandcanlimitthevaluecomparisonwithstandarddirectly,butcanmeasurethetotalmoldinterferenceonly.Thevoiceseparatesthenetworkisthemostidealmethod,butthemanufacturingofitskeypartstransformerhaveveryhighrequest..Four,repressafewmeasureoftheinterferencecurrentlyThreemainfactorsthatbecometheelectromagnetisminterferenceareinterferencessources,thedisseminationpathsandissubjectedtotheequipmentsof.Asaresult,repressingtheelectromagnetisminterferencealsoshouldbeginfromthesethreeaspects.Shouldrepresstheinterferencesourcefirst,thedirectcancellationinterferencereason;isathatremovestheinterferencesourceandisbytheequipmentsoftomatchandradiatethenextinorder,cutoffthedisseminationpath(seethefigure2)oftheelectromagnetisminterference;thethirdistheexaltationbesubjectedtotheequipmentsofoftheanti-ability,turndownittothesensitivedegreeofthevoiceof.Repressafewmeasureoftheinterferencecurrentlyisallathatusestocutofftheelectromagnetisminterferencesourceandbebytheequipmentsoftomatchthepassagebasically,theyarevalidwaythatgosindeed.Theincommonusemethodistoshield,connectthegroundandwaveof.Theadoptionshieldstheelectromagnetismradiationinterferencethatthetechniquecanrepresstheswitchpowersupplyavailably.Forexample,thepowerswitchtubeandtheexportationdiodesusuallyhavethebiggerpowertoexhaust,forspreadhotusuallyneedtoinstalltospreadthehotmachineordirectgearingsonthepowersupplyscaleboard.Needtotransmitheatthefunctiontolikewhenthemachinepieceinstallofinsulatetheslicetocarryoninsulate,thismakethemachinepieceandscaleboardandspreadthehotmachineofacreationdistributetheelectriccapacity,thescaleboardoftheswitchpowersupplyisalineoftheACpower,asaresultdistributetheelectriccapacitytomatchtheelectromagnetisminterferencetotheexchangesimportationtocarrythetotalmoldinterferenceofcreationthroughthemachinepieceandofthescaleboards,thewaythatresolvesthisproblemistoadopttwolayersinsulatethesliceofclipalayertoshieldtheslice,andshieldtheslicetoreceivethedirectcurrentgroundup,cutofftheradiofrequencyinterferencetowardthepathoftheimportationchargedbarbedwirenetdissemination.Forrepressingtheoutputradiationoftheswitchpowersupply,theelectromagnetisminterferenceastoit'stheinfluenceofhiselectronicsequipments,cancompletelyaccordingtoprocesstoshieldthecovertothemethodthatthemagneticfieldshield,thencarryonthewholemachinehullandaconjunctionsthatshieldsthecoverandsystemareanintegralwhole,abilitytotheelectromagnetismfieldeffectivelytoshield.Somepartsofpowersupplyandtheearthsconnectwitheachotherthefunctionthatcanrisetorepresstheinterference.Forexample,thestaticelectricityshieldthelayerconnectagroundofcanrepresstochangetheelectricfieldofinterference;theconductorthatelectromagnetismshieldstousecannotconnectthegroundinprinciple,butdon'tconnectthegroundtoshieldtheconductortooftenstrengthenthestaticelectricitytomatchbutproduceso-called"thenegativestaticelectricityshield"effect,sostilltakeconnectingthegroundastolike,makingelectromagnetismshieldthuscandevelopthefunctionthatstaticelectricityshieldatthesametime.Thepublicreferencepointandtheearthsoftheelectriccircuitconnectwitheachother,canprovidethestablereferenceelectricpotentialforthesignalbacktrack.Therefore,theprotectionalineofsafetyinthesystem,shieldtoconnectagroundoflineandalineofpublicreferenceseachafterformationconnectedagroundoffemaleline,endallconnectwitheachotherwiththeearth.Shouldfollowtheprincipleof"connecttheground1:00"intheelectriccircuitsystemdesign,iftheformationorderstoconnectthegroundmuch,willappeartoshuttomatchofconnectthegroundwreathroad,bethelineofmagneticforcetocutthroughthehourofthatbacktrackandwillproducethetorespondthevoiceof,theactuallyverydifficultrealization"connecttheground1:00".Therefore,inordertolowertoconnectagroundofresistance,thecancellationdistributestheinfluenceoftheelectriccapacitybutadoptstheflatsurfacetypeororderstoconnectthegroundmuch,makeuseofaconductselectricitytheflatsurface(scaleboardormanythelayerprintstomaketheplankelectriccircuittoconductelectricitytheflatsurfacelayeretc.)conductandactionsreferenceground,eachpartthatneedstoconnectthegroundreceivescloseathandandshouldconsultthegroundup.Inordertofurtherletuptoconnectagroundofbacktracktopresstodecline,canreduceavalueofreturntheelectriccurrentwiththebypasselectriccapacity.Intheelectriccircuitsystemthatlowfrequencyandhighcoexist,aftershoulddistinguishtolinkalineofthelowfrequencyelectriccircuit,highelectriccircuitof,thepowerelectriccircuitalone,thenlinkthepublicreferencetoorderup.Thewaveofisakindofgoodwaythatrepressestoconducttheinterference.Forexample,inputtocarrytomountthefilterinthepowersupply,canrepresstheswitchpowersupplycreationtocombinetowardinterferenceofthechargedbarbedwirenetfeedback,canalsorepressthevoiceofofcomefromthechargedbarbedwirenettoviolatetothepowersupply.Inanelectriccircuitof,stilladoptacomponentofalotofappropriative,ifweartheheartcapacitor,threecarrythecapacitor,theironoxygenbodywreath,theycanimproveacharacteristicofoftheelectriccircuit.Designorchoosethefilterfittingly,andinstallandusethefilterwithaccuracy,isatechnicalimportanceoftheanti-interferencetoconstitutethepart..AtechniqueoftheEMIisakindofvalidmeasurethatrepressesthesharppulseinterference,canwithinadditiontovariousconductioninterferencewithoutputreason.Figure3isakindoffilterofEMIthatbeconstitutebytheelectriccapacity,theelectricityfeeling,connectintheswitchpowersupplyofimportationcarry.Intheelectriccircuit,theC1,C5isthehighbypasselectriccapacity,usedforthedividedbytwotheimportationpowercableofbadmoldinterference;L1andC2,C4;theL2andC3,C4constitutesalinkofthetotalmoldinterference,usedingfortheinadditiontothepowercableandanotsymmetrytotalmoldinterferenceoftheground;thefirsttimeclassfullcirclenumberoftheL3,L4isequal,thepoleiscontrary,communicatetheelectriccurrentisinthetheoutputofiscontrary,asaresultcanrepressthetotalmoldinterferenceavailably.Thetestexpressthatwant～onlytheparameteroftheappropriatechoiceamachinepiece,cancomparetorepresstheoutputconductioninterferenceoftheswitchpowersupplygoodlythen.Five,theswitchpowersupplyEMIrepressestheplaceoftheshortageofthemeasurecurrentlyRepressthemeasureexistinglytomatchandradiatefromthethatremovetheinterferencesourceandbebytheequipmentsof擾mostly,thedisseminationpaththatcutsofftheelectromagnetisminterferencesetout,thisisthevalidwaythatrepresstheinterferenceakindoftogoindeed,butfewsomeoneinvolvesthedirectcontrolinterferencesource,thecancellationinterference,ortheexaltationbeanti-bytheequipmentsoftheability,hardlyrealizingthelatterstillhasmanyspacesofdevelopment.Six,thesuggestionoftheimprovementmeasureIthoughttosetouttorepresstheinterferencecurrentlyfromthedisseminationpathoftheelectromagnetisminterference,havealreadyenteredthematuritygradually.Weseetoordertoreturntotheswitchpowersupplymachinepiece.Practicedfromtheworkofmanyyearstosee,attheelectriccircuitwantstonoticethefollowingwhattime:(1)Whileprintingtomaketheplanklayout,wantwillimitatetheelectriccircuitareaandnumericalelectriccircuitareastoseparatereasonably,thepowersupplyandalinesarealonethederivation,thepowersupplysuppliestheplacetogathertogethertill1:00;theＰＣＢclothline,thenumericalsignallineofhighwantstousetheshortline,themainsignallineisbestconcentratedintheＰＣＢplankcenter,thepowercablekeepsoffthenumericalsignallineofhighpossiblyatthesametimeorpartitionswithaline.Thenextinorder,canmatchthecoefficienttocometotheclothlineaccordingtothe,reducetheinterferencetomatch(2)toprinttomaketheknotholepowercableandalinestoprinttomakeasfaraspossiblepossiblybreadth,toletupthelineresistance,thusletuptheinterferencevoicethatthepublicresistancecause.(3)Themachinepiecechoosestousetostickasliceofcomponentmuchandshortensthecomponenttoleadthefeetlengthpossibly,toletupthecomponenttodistributetheinfluenceofgiveorgetanelectricshockthefeeling.(4)CarrytoclosetothemachinepiecetoconnectintoanelectriccapacityofpossiblyintheVddandpowersupplyofVcc,toshortentheswitchelectriccurrenttocirculatethepath,suchasmergetoconnectonthepowersupplyfeetwith10μＦaluminumelectrolysisesand01electriccapacityofμＦss.Canreplacethealuminumelectrolysiselectriccapacitywiththeelectrolysiselectriccapacityforthepowersupplyofthehigh-speednumericalＩＣcarry,becausethe鉭electrolysisissmallerthanthealuminumelectrolysisandhavetohaveanothertoaresistance.KnottheoryFactorthatproducestheswitchpowersupplyelectromagnetisminterferencestillalotof,represstheelectromagnetisminterferencetostillhaveagreatdealofwork.Repressvariousvoiceofoftheswitchpowersupplyandwillmaketheswitchpowersupplygetthemoreextensiveapplicationcompletely

解析有效的開關電源電磁干擾的抑制措施摘

要：

本文先分析了開關電源產生電磁干擾的機理,,就目前幾種有效的開關電源電磁干擾措施進行了分析比較，并為開關電源電磁干擾的進一步研究提出參考建議。關鍵詞：

開關電源

電磁干擾

抑制措施

耦合

目前，許多大學及科研單位都進行了開關電源EMI（ElectromagneticInterference）的研究，他們中有些從EMI產生的機理出發，有些從EMI產生的影響出發，都提出了許多實用有價值的方案。這里分析與比較了幾種有效的方案，并為開關電源EMI的抑制措施提出新的參考建議。

一、開關電源電磁干擾的產生機理

開關電源產生的干擾,按噪聲干擾源種類來分,可分為尖峰干擾和諧波干擾兩種;若按耦合通路來分,可分為傳導干擾和輻射干擾兩種。現在按噪聲干擾源來分別說明：

1、二極管的反向恢復時間引起的干擾

高頻整流回路中的整流二極管正向導通時有較大的正向電流流過,在其受反偏電壓而轉向截止時,由于PN結中有較多的載流子積累,因而在載流子消失之前的一段時間里,電流會反向流動,致使載流子消失的反向恢復電流急劇減少而發生很大的電流變化(di/dt)。

2、開關管工作時產生的諧波干擾

功率開關管在導通時流過較大的脈沖電流。例如正激型、推挽型和橋式變換器的輸入電流波形在阻性負載時近似為矩形波,其中含有豐富的高次諧波分量。當采用零電流、零電壓開關時,這種諧波干擾將會很小。另外,功率開關管在截止期間,高頻變壓器繞組漏感引起的電流突變,也會產生尖峰干擾。

3、交流輸入回路產生的干擾

無工頻變壓器的開關電源輸入端整流管在反向恢復期間會引起高頻衰減振蕩產生干擾。

開關電源產生的尖峰干擾和諧波干擾能量,通過開關電源的輸入輸出線傳播出去而形成的干擾稱之為傳導干擾;而諧波和寄生振蕩的能量,通過輸入輸出線傳播時,都會在空間產生電場和磁場。這種通過電磁輻射產生的干擾稱為輻射干擾。

4、其他原因

元器件的寄生參數，開關電源的原理圖設計不夠完美，印刷線路板（PCB）走線通常采用手工布置，具有很大的隨意性，PCB的近場干擾大，并且印刷板上器件的安裝、放置，以及方位的不合理都會造成EMI干擾。

二、開關電源EMI的特點

作為工作于開關狀態的能量轉換裝置，開關電源的電壓、電流變化率很高，產生的干擾強度較大；干擾源主要集中在功率開關期間以及與之相連的散熱器和高平變壓器，相對于數字電路干擾源的位置較為清楚；開關頻率不高（從幾十千赫和數兆赫茲），主要的干擾形式是傳導干擾和近場干擾;而印刷線路板(PCB)走線通常采用手工布線,具有更大的隨意性,這增加了PCB分布參數的提取和近場干擾估計的難度.

三、EMI測試技術

目前診斷差模共模干擾的三種方法：射頻電流探頭、差模抑制網絡、噪聲分離網絡。用射頻電流探頭是測量差模共模干擾最簡單的方法，但測量結果與標準限值比較要經過較復雜的換算。差模抑制網絡結構簡單（見圖1），測量結果可直接與標準限值比較，但只能測量共模干擾。噪聲分離網絡是最理想的方法，但其關鍵部件變壓器的制造要求很高。.

四、目前抑制干擾的幾種措施

形成電磁干擾的三要素是干擾源、傳播途徑和受擾設備。因而,抑制電磁干擾也應該從這三方面著手。首先應該抑制干擾源,直接消除干擾原因;其次是消除干擾源和受擾設備之間的