izindaba

Isimo esivamile: Unjiniyela wokuklama ufaka ubuhlalu be-ferrite kusekethe ehlangabezana nezinkinga ze-EMC, ukuze athole ukuthi ubuhlalu empeleni benza umsindo ongafuneki ube mubi nakakhulu. Kungenzeka kanjani lokhu? Akufanele yini ubuhlalu be-ferrite bususe amandla omsindo ngaphandle kokwenza inkinga ibe nzima nakakhulu?
Impendulo yalo mbuzo ilula, kodwa ingase ingaqondwa kabanzi ngaphandle kwalabo abachitha isikhathi esiningi bexazulula izinkinga ze-EMI. Kalula nje, ubuhlalu be-ferrite akubona ubuhlalu be-ferrite, akubona ubuhlalu be-ferrite, njll.Abakhiqizi abaningi be-ferrite bead bahlinzeka ithebula elibonisa ingxenye yenombolo yazo, ukuvimbela imvamisa ethile (imvamisa engu-100 MHz), ukumelana ne-DC (DCR), umkhawulo wamanje olinganiselwe kanye nobukhulu obuthile Ulwazi (bheka Ithebula 1).Yonke into icishe ifane.Yini engaboniswa kudatha ishidi liwulwazi olubalulekile kanye nezici zokusebenza ezihambisanayo zefrikhwensi.
Ubuhlalu be-Ferrite buwumshini ongenzi lutho ongasusa amandla omsindo kwisekhethi ngendlela yokushisa.Ubuhlalu bukabuthe bukhiqiza i-impedance ebangeni elibanzi lefrikhwensi, ngaleyo ndlela kuqedwe wonke noma ingxenye yamandla omsindo ongafuneki kuloluhlu lwamafrikhwensi. njengolayini we-Vcc we-IC), kuyinto efiselekayo ukuba nenani eliphansi lokumelana ne-DC ukuze kugwenywe ukulahlekelwa okukhulu kwamandla kusignali edingekayo kanye/noma i-voltage noma umthombo wamanje (ukulahlekelwa kwe-I2 x DCR). Nokho, kuyafiseleka ukuba nakho i-impedance ephezulu emazingeni athile achaziwe.Ngakho-ke, i-impedance ihlobene nezinto ezisetshenziswayo (permeability), ubukhulu be-ferrite bead, inani lama-windings, kanye nesakhiwo esimazombezombe.Ngokusobala, kusayizi wezindlu onikeziwe kanye nezinto ezithile ezisetshenzisiwe ezisetshenzisiwe. , uma ama-windings amaningi, i-impedance iyanda, kodwa njengoba ubude bomzimba bekhoyili yangaphakathi bubude, lokhu kuzophinde kukhiqize ukumelana okuphezulu kwe-DC.Umthamo wamanje olinganiselwe wale ngxenye uhambisana ngokuphambene nokumelana ne-DC yayo.
Esinye sezici eziyisisekelo zokusebenzisa ubuhlalu be-ferrite ezinhlelweni ze-EMI ukuthi ingxenye kufanele ibe esigabeni sokumelana. Kusho ukuthini? Kalula nje, lokhu kusho ukuthi “R” (ukumelana ne-AC) kufanele kube kukhulu kuno-“XL” (i-inductive ukusabela).Emafrikhwensi lapho i-XL> R (imvamisa ephansi), ingxenye ifana kakhulu ne-inductor kunesiphikisayo.Emvamisa ye-R> XL, ingxenye iziphatha njenge-resistor, okuyisici esidingekayo sobuhlalu be-ferrite. imvamisa lapho i-“R” iba nkulu kune-“XL” ibizwa ngokuthi i-“crossover” frequency.Lokhu kuboniswa kuMfanekiso 1, lapho imvamisa ye-crossover ingu-30 MHz kulesi sibonelo futhi imakwe ngomcibisholo obomvu.
Enye indlela yokubheka lokhu ngokwemibandela yalokho ingxenye eyenzayo ngempela phakathi nezigaba zayo zokungeniswa nokumelana.Njengezinye izinhlelo zokusebenza lapho i-impedance ye-inductor ingafaniswa, ingxenye yesiginali engenayo iboniswa emuva emthonjeni. inikeza isivikelo esithile sezinto ezibucayi ngakolunye uhlangothi lobuhlalu be-ferrite, kodwa futhi yethula u-“L” kumjikelezo, okungabangela ukuzwakala kwe-resonance kanye nokunyakazisa (ukukhala).Ngakho-ke, lapho ubuhlalu kazibuthe busashintshashintsha ngokwemvelo, ingxenye amandla omsindo azoboniswa futhi ingxenye yamandla omsindo izodlula, kuye ngamavelu e-inductance kanye ne-impedance.
Uma ubuhlalu be-ferrite busesigabeni saso sokumelana, ingxenye iziphatha njenge-resistor, ngakho-ke ivimba amandla omsindo futhi imunca lawo mandla kusekethe, futhi iwamunce ngendlela yokushisa.Nakuba yakhiwe ngendlela efanayo njengamanye ama-inductors, isebenzisa. inqubo efanayo, umugqa wokukhiqiza kanye nobuchwepheshe, imishini, nezinye zezinto ezifanayo zengxenye, ubuhlalu be-ferrite busebenzisa izinto ezilahlekile ze-ferrite, kuyilapho ama-inductors asebenzisa ukulahlekelwa okuphansi kwensimbi ye-Oxygen impahla.Lokhu kuboniswa ijika ku-Figure 2.
Isibalo sibonisa i-[μ''], ebonisa ukuziphatha kobuhlalu obulahlekile be-ferrite.
Iqiniso lokuthi i-impedance inikezwa ku-100 MHz nayo iyingxenye yenkinga yokukhetha.Ezimweni eziningi ze-EMI, i-impedance kule frequency ayibalulekile futhi iyadukisa.Inani laleli "phuzu" alibonisi ukuthi i-impedance iyanda, iyancipha. , iba isicaba, futhi i-impedance ifinyelela inani eliphakeme kakhulu kule mvamisa, futhi noma ngabe okokusebenza kusesesigabeni sayo sokungena noma kushintshele esigabeni sazo sokumelana.Eqinisweni, abahlinzeki abaningi be-ferrite bead basebenzisa izinto eziningi zobuhlalu obufanayo be-ferrite, noma okungenani njengoba kukhonjisiwe eshidini ledatha.Bheka Umfanekiso 3.Wonke amajika ama-5 kulo mfanekiso awobuhlalu obuhlukile be-ferrite obuyi-120 ohm.
Bese, lokho umsebenzisi okufanele akuthole ijika le-impedance elibonisa izici zokuvama kobuhlalu be-ferrite.Isibonelo sejiko elijwayelekile le-impedance siboniswa kuMfanekiso 4.
Umfanekiso wesi-4 ubonisa iqiniso elibaluleke kakhulu.Le ngxenye iqokwe njengobuhlalu be-ferrite obungama-50 ohm obunobuhlalu obungu-100 MHz, kodwa imvamisa yayo ye-crossover imayelana nama-500 MHz, futhi ifinyelela ngaphezu kuka-300 ohms phakathi kuka-1 no-2.5 ​​GHz. Futhi, nje ukubuka ishidi ledatha ngeke kwazise umsebenzisi lokhu futhi kungase kudukise.
Njengoba kuboniswe emfanekisweni, izici zezinto ezisetshenziswayo ziyahlukahluka.Kunezinhlobonhlobo eziningi ze-ferrite ezisetshenziselwa ukwenza ubuhlalu be-ferrite.Ezinye izinto ukulahlekelwa okukhulu, i-broadband, imvamisa ephezulu, ukulahleka kokufakwa okuphansi nokunye.Umfanekiso 5 ubonisa ukuqoqwa okujwayelekile imvamisa yohlelo lokusebenza kanye ne-impedance.
Enye inkinga evamile ukuthi abaklami bebhodi lesifunda ngezinye izikhathi banqunyelwe ukukhethwa kobuhlalu be-ferrite ku-database yabo yezingxenye ezigunyaziwe.Uma inkampani inobuhlalu obumbalwa kuphela obuvunyelwe ukusetshenziswa kweminye imikhiqizo futhi bubhekwa njengobanelisayo, ezimweni eziningi, akudingekile ukuhlola nokugunyaza ezinye izinto kanye nengxenye yezinombolo.Esikhathini esidlule, lokhu kuye kwaholela kaningi emiphumeleni emibi yenkinga yomsindo we-EMI yasekuqaleni echazwe ngenhla.Indlela eyayisebenza ngaphambilini ingase isebenze kuphrojekthi elandelayo, noma kungenzeka kungasebenzi.Awukwazi ukumane ulandele isixazululo se-EMI sephrojekthi yangaphambilini, ikakhulukazi uma imvamisa yesiginali edingekayo ishintsha noma imvamisa yezingxenye ezikhipha imisebe ezingaba khona njengemishini yewashi ishintsha.
Uma ubheka ama-curve amabili e-impedance ku-Figure 6, ungaqhathanisa imiphumela yezinto ezibonakalayo yezingxenye ezimbili ezifanayo ezikhethiwe.
Kulezi zingxenye ezimbili, i-impedance ku-100 MHz yi-120 ohms. Ngokwengxenye engakwesobunxele, usebenzisa "B", i-impedance ephezulu imayelana ne-150 ohms, futhi ibonakala ku-400 MHz. Ngokwengxenye engakwesokudla. , kusetshenziswa into ethi "D", i-impedance ephezulu ingu-700 ohms, efinyelelwa cishe ku-700 MHz.Kodwa umehluko omkhulu kakhulu imvamisa ye-crossover.I-ultra-high loss "B" ukuguqulwa kwezinto ezibonakalayo ku-6 MHz (R> XL) , kuyilapho imvamisa ephezulu kakhulu ethi "D" isalokhu ishintshashintsha cishe ku-400 MHz. Iyiphi ingxenye efanele ongayisebenzisa?Kuncike kuhlelo lokusebenza ngalunye.
Umfanekiso 7 ukhombisa zonke izinkinga ezijwayelekile ezenzeka uma ubuhlalu be-ferrite obungalungile bukhethwa ukucindezela i-EMI.Isiginali engahlungiwe ikhombisa i-474.5 mV ishoot engaphansi ku-3.5V, 1 US pulse.
Emphumeleni wokusebenzisa uhlobo lokulahlekelwa okukhulu (isakhiwo esimaphakathi), i-undershoot yokulinganisa iyanda ngenxa yemvamisa ephezulu ye-crossover yengxenye.I-signal shot undershoot inyuke isuka ku-474.5 mV yaya ku-749.8 mV. I-Super High Loss impahla ine-a imvamisa ephansi ye-crossover nokusebenza okuhle.Kuzoba into efanele ukusetshenziswa kulolu hlelo lokusebenza (isithombe esingakwesokudla).I-undershoot esebenzisa le ngxenye yehliselwe ku-156.3 mV.
Njengoba i-current eqondile ngokusebenzisa ubuhlalu ikhula, i-core material iqala ukugcwala.Kuma-inductors, lokhu kubizwa ngokuthi i-saturation current futhi kucaciswa njengokwehla kwephesenti enani le-inductance.Ngobuhlalu be-ferrite, lapho ingxenye isesigabeni sokumelana, i umphumela wokugcwalisa ubonakala ekwehleni kwevelu ye-impedance nge-frequency.Lokhu kwehla kwe-impedance kunciphisa ukusebenza kahle kobuhlalu be-ferrite kanye nekhono labo lokuqeda umsindo we-EMI (AC).
Kulesi sibalo, ubuhlalu be-ferrite bulinganiselwa ku-100 ohms ku-100 MHz. Lokhu ukuvimbela okujwayelekile okulinganiselwe uma ingxenye ingenayo i-DC yamanje.Nokho, kungabonakala ukuthi uma i-DC current isetshenziswa (isibonelo, ku-IC VCC okokufaka), i-impedance esebenzayo yehla kakhulu.Kujika elingenhla, ku-1.0 A yamanje, i-impedance esebenzayo ishintsha kusuka ku-100 ohms kuya ku-20 ohms. 100 MHz.Mhlawumbe akuyona into ebucayi kakhulu, kodwa into okufanele unjiniyela wokuklama anake. Ngokufanayo, ngokusebenzisa idatha yesici sikagesi kuphela. yengxenye eshidini ledatha lomphakeli, umsebenzisi ngeke azi ngale nto yokuchema kwe-DC.
Njengama-inductors e-RF anemvamisa ephezulu, isiqondiso esijikayo sekhoyili yangaphakathi kubuhlalu be-ferrite sinethonya elikhulu ezicini zefrikhwensi yobuhlalu.Indlela yokumayo ayithinti nje kuphela ubudlelwano phakathi kwezinga le-impedance nefrequency, kodwa futhi ishintsha impendulo yemvamisa. Emfanekisweni 9, ubuhlalu obubili be-ferrite obungu-1000 ohm buboniswa obunobukhulu obufanayo bezindlu nezinto ezifanayo, kodwa nezindlela ezimbili ezihlukene zokusonta.
Amakhoyili engxenye yesokunxele alinyazwa endizeni eqondile futhi anqwabelene ohlangothini oluvundlile, okukhiqiza i-impedance ephakeme kanye nokusabela kwemvamisa ephakeme kunengxenye engakwesokudla kwenxeba endizeni evundlile futhi anqwabelene ngendlela eqondile. Lokhu kubangelwa ngokwengxenye. kuya ku-low capacitive reactance (XC) ehambisana nokuncishiswa kwe-parasitic capacitance phakathi kwetheminali yokugcina kanye nekhoyili yangaphakathi.I-XC ephansi izokhiqiza i-self-resonance frequency ephakeme, bese ivumela ukuvinjelwa kobuhlalu be-ferrite ukuthi kuqhubeke kwanda kuze kube yilapho ifinyelela i-self-resonance frequency ephezulu, ephakeme kunesakhiwo esijwayelekile sobuhlalu be-ferrite Inani le-impedance.Amajika obuhlalu obubili obungenhla obuyi-1000 ohm ferrite akhonjisiwe kuMfanekiso 10.
Ukuze siqhubeke sibonise imiphumela yokukhetha okulungile nokungalungile kobuhlalu be-ferrite, sisebenzise isifunda sokuhlola esilula kanye nebhodi lokuhlola ukuze sibonise okuningi kokuqukethwe okukhulunywe ngakho ngenhla. Emfanekisweni 11, ibhodi lokuhlola libonisa ukuma kobuhlalu obuthathu be-ferrite kanye namaphuzu okuhlola amakiwe. “A”, “B” kanye no-“C”, atholakala ebangeni le-transmitter output (TX) device.
Ubuqotho besignali bulinganiswa ohlangothini oluphumayo lobuhlalu be-ferrite endaweni ngayinye kwezintathu, futhi ziphindwa ngobuhlalu obubili be-ferrite owenziwe ngezinto ezihlukene.Into yokuqala, into elahlekelwa yi-low-frequency "S" elahlekile, ihlolwe ezindaweni “A”, “B” kanye “C”.Okulandelayo, kusetshenziswe into engu-“D” yokuvama okuphezulu.Imiphumela yephoyinti nephuzu kusetshenziswa lobu buhlalu obubili be-ferrite iboniswa kuMfanekiso 12.
Isiginali engahlungiwe "edlula" iboniswa emgqeni ophakathi, ikhombisa ukudubuleka okungaphezulu nangaphansi emaphethelweni akhuphukayo nawayo, ngokulandelanayo.Kungabonakala ukuthi uma kusetshenziswa into elungile yezimo zokuhlola ezingenhla, imvamisa ephansi elahlekelwayo ikhombisa ukudlula okuhle. kanye nokuthuthukiswa kwesignali ye-undershoot emaphethelweni akhuphukayo naphansi.Le miphumela ikhonjiswe kumugqa ophezulu woMfanekiso 12.Umphumela wokusebenzisa izinto ezinemvamisa ephezulu ungabangela ukukhala, okukhulisa izinga ngalinye futhi kwandise isikhathi sokungazinzi.Le miphumela yokuhlolwa iwukuthi kuboniswe emgqeni ongezansi.
Uma ubheka ukuthuthukiswa kwe-EMI nemvamisa engxenyeni engenhla enconyiwe (Umfanekiso 12) ekuskeneni okuvundlile okuboniswe kuMfanekiso 13, kungabonakala ukuthi kuwo wonke amafrikhwensi, le ngxenye inciphisa kakhulu ama-EMI spikes futhi inciphisa izinga lomsindo lilonke ku-30. kuya cishe Kububanzi obungu-350 MHz, ileveli eyamukelekayo ingaphansi kakhulu komkhawulo we-EMI ogqanyiswe umugqa obomvu.Leli izinga elijwayelekile lokulawula lemishini Yekilasi B (i-FCC Ingxenye 15 e-United States). Into ethi “S” esetshenziswa kubuhlalu be-ferrite isetshenziswa ngokukhethekile kulawa maza aphansi. Kuyabonakala ukuthi uma ifrikhwensi isingaphezu kuka-350 MHz, Okubalulekile kwe-“S” kunomthelela olinganiselwe kuzinga lomsindo we-EMI yasekuqaleni, engahlungiwe, kodwa yehlisa i-spike enkulu ku-750 MHz cishe ngo-6 dB. Uma ingxenye eyinhloko yenkinga yomsindo we-EMI ingaphezu kuka-350 MHz, udinga cabanga ngokusetshenziswa kwezinto ezisetshenziswayo ze-ferrite ephakeme kakhulu lapho i-impedance yayo ephezulu iphezulu ku-spectrum.
Yiqiniso, konke ukukhala (njengoba kuboniswe ejikeni elingezansi loMfanekiso 12) ngokuvamile kungagwenywa ukuhlola ukusebenza kwangempela kanye/noma isofthiwe yokulingisa, kodwa kuthenjwa ukuthi lesi sihloko sizovumela abafundi ukuba badlule amaphutha amaningi avamile futhi banciphise isidingo khetha ubuhlalu obulungile be-ferrite Isikhathi, futhi unikeze indawo yokuqala “efundiswe” lapho ubuhlalu be-ferrite budingeka ukusiza ukuxazulula izinkinga ze-EMI.
Okokugcina, kungcono kakhulu ukugunyaza uchungechunge noma uchungechunge lobuhlalu be-ferrite, hhayi inombolo yengxenye eyodwa kuphela, ukuze uthole ukukhetha okwengeziwe nokuvumelana nezimo. , ikakhulukazi uma kuthengwa okuningi kwephrojekthi efanayo.Kulula ukwenza lokhu okokuqala, kodwa uma izingxenye sezifakwe kusizindalwazi sengxenye ngaphansi kwenombolo yokulawula, zingasetshenziswa noma kuphi.Okubalulekile ukuthi ukusebenza kwemvamisa yezingxenye ezivela kubahlinzeki abahlukene kufana kakhulu ukuze kuqedwe ukuthi kungenzeka kwezinye izinhlelo zokusebenza esikhathini esizayo Inkinga yenzeka.Indlela engcono kakhulu yokuthola idatha efanayo kubahlinzeki abahlukene, futhi okungenani ube nejika le-impedance. Lokhu kuzoqinisekisa futhi ukuthi ubuhlalu obulungile be-ferrite busetshenziswa ukuxazulula inkinga yakho ye-EMI.
UChris Burket ubesebenza e-TDK kusukela ngo-1995 futhi manje usengunjiniyela omkhulu wesicelo, osekela inani elikhulu lezingxenye ezingenzi lutho.Ube nesandla ekwakhiweni komkhiqizo, ekuthengisweni kobuchwepheshe nasekukhangiseni.UMnu.UBurket ubhale futhi washicilela amaphepha ezobuchwepheshe ezinkundleni eziningi.UMnu.UBurket uthole amalungelo obunikazi amathathu ase-US ekushintsheni kokubona/kwemishini kanye nama-capacitor.
I-In Compliance ingumthombo oyinhloko wezindaba, ulwazi, imfundo kanye nogqozi lwabachwepheshe bezobunjiniyela bakagesi kanye nobuchwepheshe.
I-Aerospace Automotive Communications Consumer Electronics Education Amandla kanye Nomkhakha Wamandla Wolwazi Lobuchwepheshe Ezokwelashwa Kwezempi Nezokuvikela Kazwelonke