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Zomwe zimachitika wamba: Katswiri wokonza mapulani amayika mkanda wa ferrite mdera lomwe likukumana ndi mavuto a EMC, koma amapeza kuti mkandawo umapangitsa phokoso losafunikira kukhala loipitsitsa. Kodi izi zingatheke bwanji?
Yankho la funsoli ndi losavuta, koma silingamvetsetsedwe mochuluka kupatula omwe amathera nthawi yambiri kuthetsa mavuto a EMI. Mwachidule, mikanda ya ferrite si mikanda ya ferrite, osati mikanda ya ferrite, etc.Ambiri opanga mikanda ya ferrite amapereka tebulo lomwe limatchula gawo lawo, kulepheretsa nthawi zina (kawirikawiri 100 MHz), DC resistance (DCR), chiwerengero chapamwamba chamakono ndi miyeso ina Zambiri (onani Table 1).Chilichonse chiri pafupifupi chokhazikika.Zomwe sizikuwonetsedwa mu deta pepala ndi zambiri zakuthupi ndi mawonekedwe ofananira nawo magwiridwe antchito.
Mikanda ya Ferrite ndi chipangizo chopanda phokoso chomwe chimatha kuchotsa mphamvu ya phokoso kuchokera kumadera monga kutentha.Mikanda yamagetsi imapanga impedance mumtundu wambiri wafupipafupi, motero imachotsa mphamvu zonse kapena gawo la mphamvu zaphokoso zosafunikira mumtundu uwu. monga Vcc mzere wa IC), ndi zofunika kukhala ndi otsika DC kukana mtengo kupewa kutayika kwakukulu mphamvu mu chizindikiro chofunika ndi/kapena voteji kapena gwero panopa (I2 x DCR imfa).Komabe, ndi zofunika kukhala ndi Chifukwa chake, cholepheretsacho chikugwirizana ndi zinthu zomwe zimagwiritsidwa ntchito (permeability), kukula kwa mkanda wa ferrite, kuchuluka kwa ma windings, ndi mawonekedwe ozungulira. , ma windings ochulukirapo, amakhalanso okwera kwambiri, koma monga kutalika kwa thupi la coil yamkati ndi yaitali, izi zidzatulutsanso mphamvu yapamwamba ya DC.
Chimodzi mwa zinthu zofunika kwambiri pakugwiritsa ntchito mikanda ya ferrite mu ntchito za EMI ndikuti gawolo liyenera kukhala mu gawo lotsutsa. reactance).Pafupipafupi pomwe XL> R (mafupipafupi otsika), chigawocho chimakhala ngati inductor kusiyana ndi resistor.Pamafupipafupi a R> XL, gawolo limakhala ngati resistor, lomwe ndilofunika khalidwe la ferrite mikanda. pafupipafupi pomwe "R" imakhala yokulirapo kuposa "XL" imatchedwa "crossover" pafupipafupi. Izi zikuwonetsedwa mu Chithunzi 1, pomwe mafupipafupi a crossover ndi 30 MHz mu chitsanzo ichi ndipo amadziwika ndi muvi wofiira.
Njira ina yowonera izi ndi zomwe chigawocho chimachita kwenikweni panthawi ya inductance ndi kukaniza phases.Monga ndi ntchito zina zomwe impedance ya inductor sichikufanana, gawo la chizindikiro chomwe chikubwera chikuwonekera kumbuyo kwa gwero. kupereka chitetezo kwa zida tcheru mbali ina ya ferrite mkanda, koma imayambitsanso "L" mu dera, zomwe zingayambitse resonance ndi oscillation (kulira). mphamvu ya phokoso idzawonetsedwa ndipo gawo la mphamvu ya phokoso lidzadutsa, malingana ndi inductance ndi impedance values.
Pamene mkanda wa ferrite uli mu gawo lake lodziletsa, chigawocho chimachita ngati chotsutsa, kotero chimalepheretsa mphamvu ya phokoso ndikuyamwa mphamvuzo kuchokera kuderali, ndikuzitenga ngati kutentha. njira yomweyo, kupanga mzere ndi luso, makina, ndi zina mwa zinthu zofanana chigawo, mikanda ferrite ntchito lossy ferrite zipangizo, pamene inductors ntchito otsika kutaya chitsulo Oxygen zinthu.Izi zikuwonetsedwa pamapindikira pa Chithunzi 2.
Chithunzichi chikuwonetsa [μ''], chomwe chikuwonetsa machitidwe a zinthu zotayika za mikanda ya ferrite.
Mfundo yakuti impedance imaperekedwa pa 100 MHz imakhalanso gawo la vuto la kusankha.Nthawi zambiri za EMI, kulepheretsa maulendowa kumakhala kosafunika komanso kosokoneza. , imakhala yathyathyathya, ndipo cholepheretsacho chimafika pachimake pazifukwa izi, komanso ngati zinthuzo zikadali mu gawo la inductance kapena zasintha kukhala gawo lake lotsutsa. Ndipotu, ambiri ogulitsa ferrite bead amagwiritsa ntchito zipangizo zambiri za mkanda womwewo wa ferrite, kapena osachepera monga momwe zasonyezedwera mu pepala la deta.Onani Chithunzi 3.Zokhotakhota zonse 5 pachithunzichi ndizosiyana 120 ohm ferrite mikanda.
Kenako, zomwe wogwiritsa ntchito ayenera kupeza ndi njira yokhotakhota yomwe ikuwonetsa mawonekedwe afupipafupi a mkanda wa ferrite.
Chithunzi 4 chikuwonetsa mfundo yofunika kwambiri. Gawoli limasankhidwa ngati mkanda wa ferrite wa 50 ohm wokhala ndi mafupipafupi a 100 MHz, koma maulendo ake odutsa ndi pafupifupi 500 MHz, ndipo amakwaniritsa zoposa 300 ohms pakati pa 1 ndi 2.5 GHz. kuyang'ana pa pepala la deta sikulola wogwiritsa ntchito kudziwa izi ndipo kungakhale kosocheretsa.
Monga momwe tawonetsera m'chithunzichi, katundu wa zipangizozo amasiyana.Pali mitundu yambiri ya ferrite yomwe imagwiritsidwa ntchito popanga mikanda ya ferrite.Zinthu zina ndizotayika kwambiri, burodi, mafupipafupi, kutayika kochepa kolowetsa ndi zina zotero.Chithunzi 5 chikuwonetsa gulu lonse ndi pafupipafupi ntchito ndi impedance.
Vuto linanso lodziwika bwino ndilokuti opanga bolodi ozungulira nthawi zina amangosankha mikanda ya ferrite m'magawo awo ovomerezeka. sikoyenera kuyesa ndi kuvomereza zipangizo zina ndi manambala ena.Posachedwapa, izi zakhala zikupangitsa kuti mobwerezabwereza vuto la phokoso la EMI likhale lofotokozedwa pamwambapa.Njira yogwiritsidwa ntchito kale ingagwiritsidwe ntchito ku polojekiti yotsatira, kapena sizingakhale zogwira mtima.Simungathe kungotsatira njira ya EMI ya polojekiti yapitayi, makamaka pamene mafupipafupi a zizindikiro zofunikila akusintha kapena mafupipafupi a zigawo zomwe zingathe kuwunikira monga kusintha kwa mawotchi.
Ngati muyang'ana ma curve awiri a impedance mu Chithunzi 6, mukhoza kufananiza zotsatira zakuthupi za zigawo ziwiri zofanana.
Pazigawo ziwirizi, kusokoneza kwa 100 MHz ndi 120 ohms. Kwa mbali ya kumanzere, pogwiritsa ntchito "B" zakuthupi, kulepheretsa kwakukulu kuli pafupi ndi 150 ohms, ndipo kumadziwika pa 400 MHz. , pogwiritsa ntchito "D", kulepheretsa kwakukulu ndi 700 ohms, yomwe imapezeka pafupifupi 700 MHz. Koma kusiyana kwakukulu ndi maulendo odutsa. , pomwe ma frequency apamwamba kwambiri a "D" amakhalabe osavuta kuzungulira 400 MHz. Ndi gawo liti lomwe ndi lolondola kugwiritsa ntchito? Zimatengera pulogalamu iliyonse.
Chithunzi 7 chikuwonetsa zovuta zonse zomwe zimachitika pamene mikanda yolakwika ya ferrite yasankhidwa kupondereza EMI. Chizindikiro chosasefera chikuwonetsa 474.5 mV undershoot pa 3.5V, 1 uS pulse.
Chifukwa cha kugwiritsira ntchito mtundu wamtundu wotayika kwambiri (chiwembu chapakati), kutsika kwa muyeso kumawonjezeka chifukwa cha maulendo apamwamba a crossover ya gawolo. ma frequency otsika a crossover komanso magwiridwe antchito abwino. Idzakhala zinthu zoyenera kugwiritsa ntchito mu pulogalamuyi (chithunzi kumanja) .The undershoot ntchito gawoli wachepetsedwa kukhala 156.3 mV.
Pamene mphamvu yachindunji kupyolera mu mikanda ikuwonjezeka, chinthu choyambirira chimayamba kukhutitsidwa.Kwa inductors, izi zimatchedwa saturation current ndipo zimatchulidwa ngati kutsika kwa chiwerengero cha mtengo wa inductance. zotsatira za machulukitsidwe akuwonetsedwa ndi kuchepa kwa mtengo wa impedance ndi pafupipafupi.Kutsika kumeneku kumachepetsa mphamvu ya mikanda ya ferrite komanso kuthekera kwawo kuthetsa phokoso la EMI (AC).
Pachiwerengero ichi, mkanda wa ferrite umayikidwa pa 100 ohms pa 100 MHz. Ichi ndi chiwongoladzanja choyezera pamene mbaliyo ilibe magetsi a DC. input), mphamvu ya impedance imatsika kwambiri. Pamwambapa pamapindikira, kwa 1.0 A pakali pano, mphamvu yolepheretsa imasintha kuchokera ku 100 ohms kupita ku 20 ohms. 100 MHz. Mwina osati yovuta kwambiri, koma chinthu chomwe injiniya wojambula ayenera kumvetsera. Mofananamo, pogwiritsa ntchito deta yokha yamagetsi za gawo lomwe lili patsamba la data la ogulitsa, wogwiritsa ntchito sangadziwe izi za DC kukondera.
Monga ma inductors a RF apamwamba kwambiri, njira yokhotakhota ya koyilo yamkati mu mkanda wa ferrite imakhudza kwambiri mawonekedwe afupipafupi a mkanda. Pachithunzi 9, mikanda iwiri ya 1000 ohm ferrite ikuwonetsedwa ndi kukula kwa nyumba ndi zinthu zomwezo, koma ndi masinthidwe awiri osiyana.
The coils wa kumanzere chilonda pa ndege ofukula ndi zakhala zikuzunza m'miyoyo mu malangizo yopingasa, amene umatulutsa apamwamba impedance ndi apamwamba pafupipafupi kuyankha kuposa mbali kumanja bala mu ndege yopingasa ndi zakhala zikuzunza m'miyoyo mu ofukula direction.Izi ndi zina chifukwa. kumunsi kwa capacitive reactance (XC) yokhudzana ndi kuchepetsedwa kwa parasitic capacitance pakati pa mapeto otsiriza ndi coil yamkati. A XC yotsika idzatulutsa maulendo apamwamba amadzimadzimadzimadzimadzimadzimadzimadzimadzimadzimadzimadzimadzimadzimadzimadzimadzimadzimadzimadzimadzimitsa, kenako amalola kuti kutsekedwa kwa mkanda wa ferrite kupitirize kuwonjezeka mpaka imafika pamtunda wodziwoneka bwino kwambiri, womwe ndi wapamwamba kuposa mawonekedwe a ferrite bead Mtengo wa impedance.Mapiritsi a mikanda iwiri yapamwamba ya 1000 ohm ferrite ikuwonetsedwa mu Chithunzi 10.
Kuti tipitirize kuwonetsa zotsatira za kusankha kolondola komanso kolakwika kwa ferrite mikanda, tinagwiritsa ntchito njira yosavuta yoyesera ndi mayeso kuti tisonyeze zambiri zomwe takambirana pamwambapa. "A", "B" ndi "C", zomwe zili patali kuchokera pa chipangizo cha transmitter (TX).
Kukhulupirika kwa chizindikiro kumayesedwa kumbali yotulutsa mikanda ya ferrite mu malo onse atatu, ndipo imabwerezedwa ndi mikanda iwiri ya ferrite yopangidwa ndi zinthu zosiyanasiyana. "A", "B" ndi "C" .Kenako, "D" yafupipafupi idagwiritsidwa ntchito.Zotsatira za mfundo ndi mfundo pogwiritsa ntchito mikanda iwiri ya ferrite ikuwonetsedwa mu Chithunzi 12.
Chizindikiro cha "kupyolera" chosasefedwa chikuwonetsedwa pamzere wapakati, kusonyeza kupitirira ndi kutsika pansi pamphepete mwakukwera ndi kugwa, motsatira. ndi kupititsa patsogolo chizindikiro chapansi pazitsulo zokwera ndi zotsika.Zotsatirazi zikuwonetsedwa pamzere wapamwamba wa Chithunzi 12. Chotsatira chogwiritsira ntchito zipangizo zamakono zingayambitse kulira, zomwe zimakulitsa mlingo uliwonse ndikuwonjezera nthawi ya kusakhazikika. kuwonetsedwa pamzere wapansi.
Poyang'ana kusintha kwa EMI ndi mafupipafupi kumtunda wovomerezeka (Chithunzi 12) mu jambulani yopingasa yomwe ikuwonetsedwa mu Chithunzi 13, zikhoza kuwoneka kuti pamafupipafupi onse, gawo ili limachepetsa kwambiri ma spikes a EMI ndikuchepetsa phokoso lonse pa 30. mpaka pafupifupi Mumtundu wa 350 MHz, mulingo wovomerezeka ndi wotsika kwambiri kuposa malire a EMI owonetsedwa ndi mzere wofiira. Uwu ndiye mulingo wanthawi zonse wa zida za Gulu B (FCC Gawo 15 ku United States). Zolemba za "S" zomwe zimagwiritsidwa ntchito pamikanda ya ferrite zimagwiritsidwa ntchito makamaka pama frequency otsika awa. Zitha kuwoneka kuti ma frequency akapitilira 350 MHz, Zinthu za "S" zimakhala ndi mphamvu zochepa pamtundu wa phokoso la EMI loyambirira, losasefedwa, koma limachepetsa kukwera kwakukulu pa 750 MHz pafupifupi 6 dB. ganizirani kugwiritsa ntchito zipangizo zapamwamba za ferrite zomwe zimakhala zovuta kwambiri pamasewero.
Zachidziwikire, kuyimba konse (monga kuwonetseredwa m'munsi mwa Chithunzi 12) kumatha kupewedwa ndi kuyesa kwenikweni kwa magwiridwe antchito ndi / kapena pulogalamu yofananira, koma tikuyembekeza kuti nkhaniyi ilola owerenga kuti alambalale zolakwa zambiri zomwe wamba ndikuchepetsa kufunikira kusankha yoyenera ferrite mkanda Time, ndi kupereka kwambiri "ophunzira" poyambira pamene mikanda ferrite chofunika kuthandiza kuthetsa EMI mavuto.
Pomaliza, ndi bwino kuvomereza mndandanda wa mikanda kapena mikanda ya ferrite, osati gawo limodzi chabe, kuti musankhe zambiri komanso kusinthasintha kwa mapangidwe. , makamaka pamene kugula kangapo kumapangidwira pulojekiti yomweyi.Ndizosavuta kuchita izi nthawi yoyamba, koma mbalizo zitalowa mumsika wachigawo pansi pa nambala yolamulira, zikhoza kugwiritsidwa ntchito kulikonse. Chofunika kwambiri ndi chakuti maulendo afupipafupi a magawo ochokera kwa ogulitsa osiyanasiyana ndi ofanana kwambiri kuti athetse kuthekera kwa ntchito zina m'tsogolomu Vuto linachitika.Njira yabwino kwambiri ndiyo kupeza deta yofanana kuchokera kwa ogulitsa osiyanasiyana, ndipo osachepera kukhala ndi chopinga cha impedance. Izi zidzatsimikiziranso kuti mikanda yolondola ya ferrite imagwiritsidwa ntchito kuthetsa vuto lanu la EMI.
Chris Burket wakhala akugwira ntchito ku TDK kuyambira 1995 ndipo tsopano ndi injiniya wamkulu wa ntchito, akuthandizira chiwerengero chachikulu cha zigawo zopanda kanthu.Iye wakhala akugwira nawo ntchito yopanga mankhwala, malonda aukadaulo ndi malonda.Mr. Burket adalemba ndikusindikiza mapepala aukadaulo m'mabwalo ambiri.Mr. Burket wapeza ma patent atatu aku US pa ma switch optical/mechanical and capacitors.
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