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Imeko eqhelekileyo: Injineli yoyilo ifaka intsimbi ye-ferrite kwisekethe efumana iingxaki ze-EMC, ukufumanisa ukuba intsimbi yenza ingxolo engafunekiyo ibe mandundu.Ingenzeka njani le nto? Akufanelanga ukuba amaso e-ferrite aphelise amandla engxolo ngaphandle kokwenza ingxaki ibe mandundu?
Impendulo yalo mbuzo ilula ngobulungisa, kodwa isenokungaqondwa ngokubanzi ngaphandle kwabo bachitha ixesha elininzi besombulula iingxaki ze-EMI. Ukubeka ngokulula, amaso e-ferrite awayiwo amaso e-ferrite, hayi amaso e-ferrite, njl. itafile edwelisa inani labo lenxalenye, i-impedance kwi-frequency ethile enikiweyo (ngokuqhelekileyo i-100 MHz), ukuxhathisa kwe-DC (DCR), umlinganiselo ophezulu wangoku kunye nolunye ulwazi lwemilinganiselo (jonga iTheyibhile 1).Yonke into iphantse isemgangathweni.Yintoni engaboniswanga kwidatha Iphepha lulwazi lwemathiriyeli kunye neempawu ezihambelanayo zokwenziwa komsebenzi.
Amaso kaFerrite sisixhobo sokwenziwa esinokuthi sisuse amandla engxolo kwisekethe ngendlela yobushushu.Amaso kaMagnetic avelisa i-impedance kuluhlu olubanzi lwamaza, ngaloo ndlela ephelisa yonke okanye inxalenye yamandla engxolo engafunekiyo kolu luhlu lwamaza. njengomgca weVcc we-IC), kunqweneleka ukuba nexabiso eliphantsi lokumelana ne-DC ukuphepha ilahleko enkulu yamandla kwisignali efunekayo kunye / okanye i-voltage okanye umthombo wangoku (i-I2 x ilahleko ye-DCR) .Nangona kunjalo, kuyinqweneleka ukuba nayo I-impedance ephezulu kwiindidi ezithile ezichaziweyo zamaza.Ngoko ke, i-impedance inxulumene nezinto ezisetyenzisiweyo (ukungena), ubungakanani bentsimbi ye-ferrite, inani le-windings, kunye nesakhiwo esijikelezayo. , i-windings engaphezulu, i-impedance iphezulu, kodwa njengoko ubude bomzimba wekhoyili yangaphakathi ide, oku kuya kuvelisa ukuxhathisa okuphezulu kwe-DC.Umlinganiselo wangoku weli candelo uhambelana ngokungafaniyo nokumelana kwayo ne-DC.
Omnye wemiba esisiseko yokusebenzisa amaso e-ferrite kwizicelo ze-EMI kukuba icandelo kufuneka libe kwisigaba sokuchasa.Ithetha ukuthini? Ukubeka nje, oku kuthetha ukuba "R" (ukuxhathisa kwe-AC) kufuneka ibe mkhulu kune "XL" (inductive). kwi-reactance).Kwi-frequencies apho i-XL> R (i-frequency esezantsi), icandelo lifana ne-inductor kune-resistor. Kwi-frequency ye-R> XL, inxalenye iziphatha njenge-resistor, eluphawu olufunekayo lwamaso e-ferrite. i-frequency apho i-"R" iba nkulu kune "XL" ibizwa ngokuba yi-"crossover" frequency.Oku kuboniswa kuMfanekiso 1, apho i-crossover frequency yi-30 MHz kulo mzekelo kwaye iphawulwe ngotolo olubomvu.
Enye indlela yokujonga oku ngokubhekiselele kwinto eyenziwa licandelo ngexesha le-inductance kunye nezigaba zokuchasana.Njengoko kunye nezinye izicelo apho i-impedance ye-inductor ingahambelani, inxalenye yesignali engenayo ibonakaliswe emva komthombo. ukubonelela ngokhuseleko lwezixhobo ezibuthathaka kwelinye icala le-bead ye-ferrite, kodwa kwakhona yazisa "L" kwisekethe, enokubangela ukuba i-resonance kunye ne-oscillation (i-ringing) . Ngoko ke, xa amaso amagnetic asekho kwindalo, inxalenye I-eneji yengxolo iya kubonakaliswa kwaye inxalenye yamandla esandi iya kudlula, kuxhomekeke kwi-inductance kunye nexabiso le-impedance.
Xa i-ferrite bead ikwisigaba sayo sokumelana, icandelo liziphatha njenge-resistor, ngoko lithintela amandla engxolo kwaye lifunxa loo mandla kwisekethe, kwaye liwafunxa ngendlela yobushushu.Nangona yakhiwe ngendlela efanayo njengoko ezinye ii-inductors, zisebenzisa. inkqubo efanayo, umgca wokuvelisa kunye nobuchwepheshe, oomatshini, kunye nezinye zezinto ezifanayo zecandelo, amaso e-ferrite asebenzisa izinto ezilahlekileyo ze-ferrite, ngelixa i-inductors zisebenzisa ilahleko ephantsi ye-iron Oxygen material.Oku kuboniswe kwijika kwi-Figure 2.
Umzobo ubonisa [μ''], ebonisa ukuziphatha kwemathiriyeli yentsimbi yeferrite elahlekileyo.
Inyaniso yokuba i-impedance inikezelwa kwi-100 MHz nayo iyinxalenye yengxaki yokukhetha.Kwiimeko ezininzi ze-EMI, ukunyanzeliswa kwesi sihlandlo akunamsebenzi kwaye siyalahlekisa.Ixabiso le "ngongoma" alibonisi ukuba i-impedance iyanda, iyancipha. , iba tyaba, kwaye i-impedance ifikelela kwixabiso layo eliphezulu ngeli xesha, kwaye ingaba izinto zisekho kwinqanaba le-inductance okanye ziguqulelwe kwisigaba sokumelana. ubuncinane njengoko kubonisiwe kwiphepha ledatha.Jonga uMfanekiso 3.Zonke iigophe ezi-5 kulo mzobo zezahlukileyo 120 ohm amaso ferrite.
Emva koko, oko umsebenzisi kufuneka afumane ijika le-impedance elibonisa iimpawu ze-frequency bead ye-ferrite.
Umzobo 4 ubonisa into ebaluleke kakhulu.Le nxalenye imiselwe njenge-50 ohm ferrite bead kunye nokuphindaphinda kwe-100 MHz, kodwa i-crossover frequency yayo imalunga ne-500 MHz, kwaye ifezekisa ngaphezu kwe-300 ohms phakathi kwe-1 kunye ne-2.5 GHz. Kwakhona, nje ukujonga kwiphepha ledatha akuyi kuvumela umsebenzisi ukuba azi oku kwaye kunokuba kulahlekisa.
Njengoko kubonisiwe kumzobo, iipropati zezixhobo ziyahluka.Kukho iintlobo ezininzi ze-ferrite ezisetyenziselwa ukwenza ubuhlalu be-ferrite.Ezinye izinto zilahleko eziphezulu, i-broadband, i-frequency ephezulu, ilahleko ephantsi yokufaka kunye nokunye.Umfanekiso wesi-5 ubonisa iqela jikelele Ukusetyenziswa rhoqo kunye nokuphazamiseka.
Enye ingxaki eqhelekileyo kukuba abaqulunqi bebhodi yesekethe ngamanye amaxesha banqunyelwe ekukhetheni amaso e-ferrite kwisiseko sedatha yabo evunyiweyo. akukho mfuneko yokuvavanya nokuvumela ezinye izixhobo kunye namanani eenxalenye Isenokungasebenzi.Awukwazi ukulandela ngokulula isisombululo se-EMI seprojekthi yangaphambili, ngakumbi xa ukuphindaphindwa kophawu olufunekayo lutshintsha okanye ukuphindaphindwa kwamacandelo anokubakho okusasaza afana nokutshintsha kwezixhobo zewotshi.
Ukuba ujonga ii-curves ze-impedance kwi-Figure 6, unokuthelekisa imiphumo yezinto eziphathekayo zamacandelo amabini atyunjiweyo afanayo.
Kula macandelo amabini, i-impedance kwi-100 MHz yi-120 ohms. Kwinxalenye ekhohlo, usebenzisa "B" impahla, i-impedance ephezulu malunga ne-150 ohms, kwaye ifunyenwe kwi-400 MHz. , usebenzisa i-"D", i-impedance ephezulu yi-700 ohms, efumaneka malunga ne-700 MHz. , ngelixa i-frequency ephezulu kakhulu "D" imathiriyeli ihlala i-inductive malunga ne-400 MHz. Yeyiphi indawo echanekileyo ukuyisebenzisa?Kuxhomekeke kwisicelo ngasinye.
Umzobo 7 ubonisa zonke iingxaki eziqhelekileyo ezenzekayo xa amaso e-ferrite engalunganga ekhethelwe ukucinezela i-EMI.Isiginali engahluzwanga ibonisa i-474.5 mV undershoot kwi-3.5V, 1 US pulse.
Kwisiphumo sokusebenzisa uhlobo oluphezulu lwelahleko (isakhiwo esiphakathi), i-undershoot yokulinganisa inyuka ngenxa yobuninzi be-crossover frequency yecandelo.I-signal undershoot inyuke ukusuka kwi-474.5 mV ukuya kwi-749.8 mV.I-Super High Loss material ine- i-low crossover frequency kunye nokusebenza kakuhle.Iya kuba yinto efanelekileyo yokusetyenziswa kwesi sicelo (umfanekiso osekunene) .I-undershoot esebenzisa le nxalenye iyancipha ibe yi-156.3 mV.
Njengoko i-current ngqo ngokusebenzisa amaso inyuka, i-core material iqala ukuhlutha.I-inductors, oku kubizwa ngokuba yi-saturation current kwaye icaciswe njengepesenti yokuhla kwexabiso le-inductance.Kumahlalu e-ferrite, xa inxalenye ikwisigaba sokumelana, i Isiphumo sokuhlutha sibonakala ekunciphiseni kwexabiso le-impedance kunye ne-frequency.Olu kwehla kwi-impedance kunciphisa ukusebenza kwamaso e-ferrite kunye nokukwazi ukuphelisa ingxolo ye-EMI (AC).
Kulo mzobo, i-ferrite bead ilinganiswe kwi-100 ohms kwi-100 MHz. Le yi-impedance eqhelekileyo xa inxalenye ingenayo i-DC yangoku. Nangona kunjalo, kunokubonwa ukuba xa i-DC isetyenziswa (umzekelo, kwi-IC VCC). igalelo), i-impedance esebenzayo yehla ngokukhawuleza.Kwigophe elingasentla, i-1.0 A yangoku, utshintsho olusebenzayo lwe-impedance ukusuka kwi-100 ohms ukuya kwi-20 ohms. 100 MHz. Mhlawumbi ayibalulekanga kakhulu, kodwa into ekufuneka injineli yoyilo inikele ingqalelo. Ngokufanayo, ngokusebenzisa kuphela idatha yeempawu zombane. yecandelo ledatha sheet yomthengisi, umsebenzisi akayi kuba nolwazi ngale DC bias phenomenon.
Njenge-high-frequency inductors RF, indlela ejikajikayo yekhoyili engaphakathi kwi-ferrite bead inempembelelo enkulu kwiimpawu eziphindaphindayo ze-bead.Ulwalathiso olujikelezayo aluchaphazeli nje kuphela ubudlelwane phakathi kwe-impedance kunye nenqanaba le-frequency, kodwa lukwatshintsha ukuphendula rhoqo. KuMzobo 9, amaso amabini e-1000 ohm ferrite aboniswa ngobukhulu obufanayo bezindlu kunye nezinto ezifanayo, kodwa ngolungelelwaniso oluhlukeneyo lokujika.
Iikhoyili zecala lasekhohlo zingxwelerheka kwinqwelomoya ethe nkqo kwaye zibekwe kwicala elithe tye, elivelisa i-impedance ephezulu kunye nempendulo yamaxesha amaninzi kunenxalenye kwicala lasekunene inxeba kwinqwelomoya ethe tye kwaye ibekwe kwicala elithe tye. ukuya kwi-capacitive reactance ephantsi (XC) ehambelana nokunciphisa i-parasitic capacitance phakathi kwesiphelo sesiphelo kunye ne-coil yangaphakathi. I-XC ephantsi iya kuvelisa i-self-resonance frequency frequency, kwaye emva koko ivumele i-impedance ye-ferrite bead ukuba iqhubeke ikhula de ibe ifikelela kwi-self-resonance frequency ephezulu, ephezulu kunesakhiwo esiqhelekileyo se-ferrite bead Ixabiso le-impedance.Ii-curves ezimbini ezingentla ze-1000 ohm ferrite bead ziboniswe kuMfanekiso we-10.
Ukubonisa ngakumbi imiphumo yokukhetha okuchanekileyo kunye nokungalunganga kwe-ferrite bead, sasebenzisa isiphaluka esilula sovavanyo kunye nebhodi yokuvavanya ukubonisa uninzi lomxholo oxutyushwa ngasentla.KuMzobo we-11, ibhodi yokuvavanya ibonisa izikhundla zamaso amathathu e-ferrite kunye namanqaku okuvavanya aphawulwe. "A", "B" kunye ne "C", ezibekwe kumgama ukusuka kwisixhobo sokuhambisa (TX).
Ingqibelelo yesignali ilinganiswa kwicala lokuphuma kweentsimbi ze-ferrite kwisigxina ngasinye sesithathu, kwaye iphinda iphindwe ngeentsimbi ezimbini ze-ferrite ezenziwe ngezinto ezahlukeneyo.Impahla yokuqala, ilahleko ephantsi ye-"S" impahla, yavavanywa kumanqaku. "A", "B" kunye ne "C" .Okulandelayo, i-frequency ephezulu "D" isetyenzisiwe.Iziphumo ze-point-to-point zisebenzisa ezi zimbini ze-ferrite beads ziboniswe kwi-Figure 12.
Isibonakaliso "ngesicwecwe" esingahluzwanga siboniswa kumqolo ophakathi, ebonisa ukugqithiswa kunye ne-undershoot kwimida ekhuphukayo kunye neyokuhla, ngokulandelanayo.Ingabonwa ukuba ukusebenzisa izinto ezichanekileyo kwiimeko zovavanyo ezingentla, izinto ezisezantsi ezilahlekileyo zibonisa ukugqithisa okulungileyo. kunye nokuphuculwa kwesignali ye-undershoot kwimida yokunyuka nokuwa.Ezi ziphumo ziboniswa kumqolo ophezulu woMfanekiso 12. Isiphumo sokusebenzisa izinto eziphakamileyo eziphezulu zingabangela ukukhala, okwandisa inqanaba ngalinye kunye nokwandisa ixesha lokungazinzi.Ezi ziphumo zovavanyo zibangelwa iboniswe kumqolo ongezantsi.
Xa ujonge ukuphuculwa kwe-EMI ngokuphindaphindiweyo kwinqanaba eliphezulu elicetyiswayo (Umfanekiso we-12) kwi-scan ethe tyaba eboniswe kwi-Figure 13, kunokubonwa ukuba kuzo zonke ii-frequencies, le nxalenye iyanciphisa kakhulu i-EMI spikes kwaye inciphisa inqanaba lengxolo jikelele kwi-30. ukuya malunga Kuluhlu lwe-350 MHz, inqanaba elamkelekileyo lingaphantsi kakhulu kumda we-EMI ophawulwe ngomgca obomvu.Lo ngumgangatho olawulayo jikelele wezixhobo zeKlasi B (i-FCC iNxalenye ye-15 e-United States) imathiriyeli “ye-S” esetyenziswa kumaso e-ferrite isetyenziswa ngokukodwa kula maza asezantsi. Izinto ze-"S" zineempembelelo ezilinganiselweyo kwinqanaba lengxolo ye-EMI yokuqala, engahluzwanga, kodwa iyanciphisa i-spike enkulu kwi-750 MHz malunga ne-6 dB. Qwalasela ukusetyenziswa kwezixhobo eziphakamileyo ze-ferrite ezinokuthi zithintele kakhulu kwi-spectrum.
Ewe, konke ukukhala (njengoko kubonisiwe kwigophe elisezantsi loMzobo 12) ngokuqhelekileyo kunokuphetshwa ngovavanyo lwangempela lokusebenza kunye / okanye isoftware yokulinganisa, kodwa sinethemba lokuba eli nqaku liya kuvumela abafundi ukuba badlule iimpazamo ezininzi eziqhelekileyo kwaye banciphise isidingo khetha i-bead ye-ferrite echanekileyo Ixesha, kwaye unikeze indawo yokuqala "efundileyo" xa amaso e-ferrite efunekayo ukunceda ukusombulula iingxaki ze-EMI.
Ekugqibeleni, kungcono ukuvuma uchungechunge okanye uchungechunge lwamaso e-ferrite, kungekhona nje inani lenxalenye enye, ukhetho oluninzi kunye nokuguquguquka koyilo. , ngakumbi xa ukuthengwa okuninzi kusenzelwa iprojekthi enye.Kulula ukwenza oku okokuqala, kodwa xa iinxalenye zifakwe kwisiseko sedatha yecandelo phantsi kwenombolo yolawulo, zinokusetyenziswa naphi na.Into ebalulekileyo kukuba ukusebenza rhoqo kweengxenye ezivela kubaboneleli abahlukeneyo kufana kakhulu nokuphelisa ukuba nokwenzeka kwezinye izicelo kwixesha elizayo Ingxaki yenzekile.Indlela engcono kakhulu kukufumana idatha efanayo kubaxhasi abahlukeneyo, kwaye ubuncinane ube ne-impedans curve. Oku kuya kuqinisekisa ukuba amaso e-ferrite achanekileyo asetyenziswa ukusombulula ingxaki yakho ye-EMI.
UChris Burket usebenze kwi-TDK ukususela ngo-1995 kwaye ngoku uyinjineli yesicelo esiphezulu, exhasa inani elikhulu lamacandelo angenayo.Uye wabandakanyeka ekuyilweni kwemveliso, ukuthengiswa kwezobugcisa kunye nokuthengisa.UMnu.UBurket ubhale kwaye wapapasha amaphepha obugcisa kwiiforamu ezininzi.UMnu.UBurket ufumene amalungelo awodwa omenzi wechiza amathathu e-US kwi-optical/mechanical switches kunye ne-capacitors.
Ukuthobela ngowona mthombo weendaba, ulwazi, imfundo kunye nenkuthazo yeengcali zobunjineli bombane kunye ne-elektroniki.
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