nkhani

Ma capacitors ndi amodzi mwazinthu zomwe zimagwiritsidwa ntchito kwambiri pama board ozungulira. Pamene chiwerengero cha zipangizo zamagetsi (kuchokera ku mafoni a m'manja kupita ku magalimoto) chikuwonjezeka, momwemonso kufunikira kwa ma capacitor. Mliri wa Covid 19 wasokoneza gawo lazinthu zapadziko lonse lapansi kuchokera ku ma semiconductors kupita kuzinthu zopanda pake, ndipo ma capacitor akhala akusowa1.
Zokambirana pamutu wa ma capacitors zitha kusinthidwa kukhala bukhu kapena dikishonale. Choyamba, pali mitundu yosiyanasiyana ya ma capacitors, monga electrolytic capacitors, film capacitors, ceramic capacitors ndi zina zotero. Ndiye, mumtundu womwewo, pali zida zosiyanasiyana za dielectric. Palinso makalasi osiyanasiyana. Ponena za kapangidwe ka thupi, pali mitundu iwiri ya ma terminal ndi atatu-terminal capacitor. Palinso mtundu wa X2Y capacitor, womwe kwenikweni ndi ma capacitor a Y omwe ali m'modzi. Nanga bwanji ma supercapacitor? Chowonadi ndi chakuti, ngati mutakhala pansi ndikuyamba kuwerenga maupangiri osankha capacitor kuchokera kwa opanga akuluakulu, mutha kuthera tsikulo mosavuta!
Popeza nkhaniyi ikukhudzana ndi zofunikira, ndigwiritsa ntchito njira ina monga mwachizolowezi. Monga tanena kale, maupangiri osankha ma capacitor atha kupezeka mosavuta patsamba la 3 ndi 4, ndipo akatswiri opanga zinthu amatha kuyankha mafunso ambiri okhudza ma capacitor. M'nkhaniyi, sindibwereza zomwe mungapeze pa intaneti, koma ndikuwonetsani momwe mungasankhire ndikugwiritsa ntchito ma capacitors kudzera mu zitsanzo zothandiza. Zina zosadziwika bwino pakusankhidwa kwa capacitor, monga kuwonongeka kwa capacitance, zidzafotokozedwanso. Mukawerenga nkhaniyi, muyenera kumvetsetsa bwino kugwiritsa ntchito ma capacitors.
Zaka zapitazo, pamene ndinkagwira ntchito mu kampani yopanga zipangizo zamagetsi, tinali ndi funso lofunsana ndi katswiri wa zamagetsi. Pachithunzi chazinthu zomwe zilipo, tifunsa omwe angakhale nawo "Kodi ntchito ya DC link electrolytic capacitor ndi yotani?" ndi "Kodi ntchito ya ceramic capacitor yomwe ili pafupi ndi chip ndi chiyani?" Tikukhulupirira kuti yankho lolondola ndi DC bus capacitor Yogwiritsidwa ntchito posungira mphamvu, ma capacitor a ceramic amagwiritsidwa ntchito posefa.
Yankho "lolondola" lomwe timafuna likuwonetsa kuti aliyense pagulu lokonzekera amayang'ana ma capacitor kuchokera kumayendedwe osavuta ozungulira, osati pamalingaliro am'munda. Malingaliro a chiphunzitso cha dera siwolakwika. Pafupipafupi (kuchokera pa kHz pang'ono mpaka MHz pang'ono), chiphunzitso cha dera nthawi zambiri chimatha kufotokozera vutoli bwino. Izi ndichifukwa choti pama frequency otsika, chizindikirocho chimakhala chosiyana kwambiri. Pogwiritsa ntchito chiphunzitso cha dera, titha kuwona capacitor yomwe ikuwonetsedwa mu Chithunzi 1, pomwe kukana kofanana kwa mndandanda (ESR) ndi inductance yofananira (ESL) kumapangitsa kuti kusintha kwa capacitor kusinthe pafupipafupi.
Chitsanzochi chikufotokozera bwino momwe dera limayendera pamene dera limasinthidwa pang'onopang'ono. Komabe, pamene mafupipafupi akuwonjezeka, zinthu zimakhala zovuta kwambiri. Nthawi zina, chigawocho chimayamba kusonyeza kusagwirizana. Kuchulukitsa kumawonjezeka, mtundu wosavuta wa LCR uli ndi malire ake.
Lero, ndikadafunsidwa funso lomwelo, ndimatha kuvala magalasi owonera zakumunda ndikunena kuti mitundu yonse ya capacitor ndi zida zosungira mphamvu. Kusiyana kwake ndikuti ma electrolytic capacitors amatha kusunga mphamvu zambiri kuposa ma capacitors a ceramic. Koma pankhani ya kufalitsa mphamvu, ma capacitor a ceramic amatha kufalitsa mphamvu mwachangu. Izi zikufotokozera chifukwa chake ma capacitor a ceramic ayenera kuyikidwa pafupi ndi chip, chifukwa chip chimakhala ndi ma frequency apamwamba komanso liwiro losinthira poyerekeza ndi dera lalikulu lamagetsi.
Kuchokera pamalingaliro awa, titha kungotanthauzira miyeso iwiri ya magwiridwe antchito a ma capacitor. Chimodzi ndi kuchuluka kwa mphamvu zomwe capacitor ingasunge, ndipo ina ndi momwe mphamvuyi ingasamutsire mofulumira. Zonsezi zimadalira njira yopangira capacitor, dielectric material, kugwirizana ndi capacitor, ndi zina zotero.
Pamene kusintha kwa dera kutsekedwa (onani Chithunzi 2), zimasonyeza kuti katunduyo amafunikira mphamvu kuchokera ku gwero la mphamvu. Liwiro lomwe kusinthaku kumatseka kumatsimikizira kuchuluka kwa mphamvu zamagetsi. Popeza mphamvu imayenda pa liwiro la kuwala (theka la liwiro la kuwala mu zida za FR4), zimatenga nthawi kusamutsa mphamvu. Kuphatikiza apo, pali kusagwirizana pakati pa gwero ndi chingwe chotumizira ndi katundu. Izi zikutanthauza kuti mphamvu sizidzasamutsidwa paulendo umodzi, koma maulendo angapo ozungulira5, chifukwa chake pamene kusinthako kusinthidwa mofulumira, tidzawona kuchedwa ndi kulira kwa mawonekedwe osinthika.
Chithunzi 2: Zimatengera nthawi kuti mphamvu zichulukane mumlengalenga; kusagwirizana kwa impedance kumayambitsa maulendo angapo ozungulira potengera mphamvu.
Mfundo yakuti kupereka mphamvu kumatenga nthawi komanso maulendo angapo ozungulira amatiuza kuti tifunika kusuntha mphamvu pafupi ndi katunduyo, ndipo tifunika kupeza njira yoperekera mwamsanga. Yoyamba nthawi zambiri imatheka pochepetsa mtunda wakuthupi pakati pa katundu, kusinthana ndi capacitor. Chotsatiracho chimapindula mwa kusonkhanitsa gulu la ma capacitor omwe ali ndi impedance yaying'ono kwambiri.
Field theory ikufotokozanso zomwe zimayambitsa phokoso lamtundu wamba. Mwachidule, phokoso lamtundu wamba limapangidwa pamene mphamvu ya katunduyo sinakwaniritsidwe panthawi yosintha. Choncho, mphamvu zosungidwa mu danga pakati pa katundu ndi kondakitala pafupi adzaperekedwa kuthandizira kufunikira kwa sitepe. Malo pakati pa katundu ndi oyendetsa pafupi ndi omwe timatcha kuti parasitic / mutual capacitance (onani Chithunzi 2).
Timagwiritsa ntchito zitsanzo zotsatirazi kusonyeza momwe tingagwiritsire ntchito ma electrolytic capacitors, multilayer ceramic capacitors (MLCC), ndi mafilimu capacitors. Onse ozungulira ndi gawo lachidziwitso amagwiritsidwa ntchito pofotokozera momwe ma capacitors amasankhidwa.
Electrolytic capacitors amagwiritsidwa ntchito makamaka mu ulalo wa DC ngati gwero lalikulu lamphamvu. Kusankhidwa kwa electrolytic capacitor nthawi zambiri kumadalira:
Pakuchita kwa EMC, mawonekedwe ofunikira kwambiri a ma capacitor ndi kusakhazikika komanso mawonekedwe pafupipafupi. Kutulutsa kwapang'onopang'ono komwe kumachitika nthawi zonse kumadalira magwiridwe antchito a DC link capacitor.
Kuwonongeka kwa ulalo wa DC sikungodalira ESR ndi ESL ya capacitor, komanso kudera la loop yotentha, monga momwe tawonetsera pa Chithunzi 3. Malo okulirapo otentha amatanthauza kuti kutengera mphamvu kumatenga nthawi yayitali, kotero magwiridwe antchito zidzakhudzidwa.
Chosinthira chotsika cha DC-DC chidapangidwa kuti chitsimikizire izi. Kukonzekera koyeserera kwa EMC kusanachitike komwe kukuwonetsedwa pachithunzi 4 kumapanga sikani yotulutsa mpweya pakati pa 150kHz ndi 108MHz.
Ndikofunika kuonetsetsa kuti ma capacitor omwe amagwiritsidwa ntchito mu phunziro ili onse amachokera kwa wopanga yemweyo kuti apewe kusiyana kwa makhalidwe a impedance. Mukagulitsa capacitor pa PCB, onetsetsani kuti palibe njira zazitali, chifukwa izi zidzakulitsa ESL ya capacitor. Chithunzi 5 chikuwonetsa masinthidwe atatu.
Zotsatira zotulutsidwa za masinthidwe atatuwa zikuwonetsedwa mu Chithunzi 6. Zitha kuwoneka kuti, poyerekeza ndi capacitor imodzi ya 680 µF, ma capacitor awiri a 330 µF amapeza ntchito yochepetsera phokoso la 6 dB pamlingo wokulirapo.
Kuchokera ku chiphunzitso cha dera, tinganene kuti pogwirizanitsa ma capacitor awiri mofanana, ESL ndi ESR zili ndi theka. Kuchokera pamalingaliro amalingaliro akumunda, palibe gwero limodzi lokha lamphamvu, koma magwero awiri amphamvu amaperekedwa ku katundu womwewo, mothandiza kuchepetsa nthawi yonse yotumizira mphamvu. Komabe, pama frequency apamwamba, kusiyana pakati pa ma capacitor awiri a 330 µF ndi capacitor imodzi ya 680 µF kudzachepa. Izi zili choncho chifukwa phokoso lafupipafupi limasonyeza kusakwanira kwa mphamvu ya sitepe. Tikasuntha capacitor ya 330 µF pafupi ndi chosinthira, timachepetsa nthawi yosinthira mphamvu, zomwe zimawonjezera kuyankha kwa capacitor.
Zotsatira zake zikutiuza phunziro lofunika kwambiri. Kuchulukitsa mphamvu ya capacitor imodzi sikungathandizire kufunikira kwamphamvu kwamphamvu. Ngati n'kotheka, gwiritsani ntchito zigawo zing'onozing'ono za capacitive. Pali zifukwa zambiri zochitira zimenezi. Choyamba ndi mtengo. Nthawi zambiri, pamlingo womwewo wa phukusi, mtengo wa capacitor umakwera kwambiri ndi mtengo wa capacitance. Kugwiritsa ntchito capacitor imodzi kungakhale kokwera mtengo kuposa kugwiritsa ntchito ma capacitor angapo ang'onoang'ono. Chifukwa chachiwiri ndi kukula. Cholepheretsa pakupanga mankhwala nthawi zambiri chimakhala kutalika kwa zigawozo. Kwa ma capacitor akuluakulu, kutalika nthawi zambiri kumakhala kwakukulu, komwe sikuli koyenera kupanga mankhwala. Chifukwa chachitatu ndi machitidwe a EMC omwe tidawona mu kafukufukuyu.
Chinthu chinanso choyenera kuganizira mukamagwiritsa ntchito electrolytic capacitor ndikuti mukalumikiza ma capacitor awiri pamndandanda kuti mugawane voteji, mudzafunika choletsa chowongolera 6.
Monga tanena kale, ma capacitor a ceramic ndi zida zazing'ono zomwe zimatha kupereka mphamvu mwachangu. Nthawi zambiri ndimafunsidwa funso "Ndikufuna capacitor ingati?" Yankho la funso ili ndiloti kwa ma capacitors a ceramic, mtengo wa capacitance suyenera kukhala wofunika kwambiri. Chofunikira apa ndikuzindikira kuti liwiro losamutsa mphamvu ndi liti lomwe likukwanira pakugwiritsa ntchito kwanu. Ngati kutulutsa kochitidwa kulephera pa 100 MHz, ndiye kuti capacitor yokhala ndi cholepheretsa chaching'ono kwambiri pa 100 MHz idzakhala chisankho chabwino.
Uku ndi kusamvetsetsa kwina kwa MLCC. Ndawonapo mainjiniya akugwiritsa ntchito mphamvu zambiri posankha ma capacitor a ceramic okhala ndi ESR yotsika kwambiri ndi ESL asanalumikizane ndi ma capacitor ku RF reference point kudzera m'mipata yayitali. Ndikoyenera kutchula kuti ESL ya MLCC nthawi zambiri imakhala yotsika kwambiri kuposa yolumikizira pa bolodi. Connection inductance akadali gawo lofunikira kwambiri lomwe limakhudza kufalikira kwa ma frequency a ceramic capacitors7.
Chithunzi 7 chikuwonetsa chitsanzo choipa. Kutsata kwautali (0.5 mainchesi kutalika) kumabweretsa osachepera 10nH inductance. Zotsatira zoyeserera zikuwonetsa kuti kutsekeka kwa capacitor kumakhala kokwera kwambiri kuposa momwe amayembekezera pafupipafupi (50 MHz).
Limodzi mwavuto la ma MLCC ndilakuti amakonda kugwirizana ndi kachitidwe ka inductive pa board. Izi zitha kuwoneka pachitsanzo chowonetsedwa pa Chithunzi 8, pomwe kugwiritsa ntchito 10 µF MLCC kumayambitsa kumveka kwa pafupifupi 300 kHz.
Mukhoza kuchepetsa resonance posankha chigawo chimodzi ndi ESR yokulirapo kapena kungoyika chopinga chaching'ono (monga 1 ohm) mndandanda ndi capacitor. Njira yamtunduwu imagwiritsa ntchito zida zotayika kuti zipondereze dongosolo. Njira ina ndiyo kugwiritsa ntchito mtengo wina wa capacitance kusuntha resonance kumalo otsika kapena apamwamba.
Ma capacitor opanga mafilimu amagwiritsidwa ntchito pazinthu zambiri. Ndiwo ma capacitor omwe angasankhidwe pa otembenuza amphamvu kwambiri a DC-DC ndipo amagwiritsidwa ntchito ngati zosefera za EMI pamizere yamagetsi (AC ndi DC) komanso masinthidwe amtundu wamba. Timatenga X capacitor mwachitsanzo kuti tifotokoze mfundo zazikuluzikulu zogwiritsira ntchito mafilimu opangira mafilimu.
Ngati chiwombankhanga chichitika, chimathandizira kuchepetsa kupanikizika kwapamwamba kwambiri pamzere, choncho nthawi zambiri amagwiritsidwa ntchito ndi transient voltage suppressor (TVS) kapena metal oxide varistor (MOV).
Mwinamwake mukudziwa kale zonsezi, koma kodi mumadziwa kuti mtengo wa capacitance wa X capacitor ukhoza kuchepetsedwa kwambiri ndi zaka zogwiritsidwa ntchito? Izi ndi zoona makamaka ngati capacitor ikugwiritsidwa ntchito pamalo a chinyezi. Ndawona mtengo wa capacitance wa X capacitor ungotsika mpaka pang'ono peresenti ya mtengo wake wovotera mkati mwa chaka chimodzi kapena ziwiri, kotero dongosolo lomwe poyamba linapangidwa ndi X capacitor linataya chitetezo chonse chomwe capacitor kutsogolo angakhale nacho.
Ndiye chinachitika n’chiyani? Mpweya wonyezimira ukhoza kulowa mu capacitor, pamwamba pa waya ndi pakati pa bokosi ndi epoxy potting compound. The aluminiyamu metallization ndiye kuti oxidized. Alumina ndi insulator yabwino yamagetsi, motero imachepetsa mphamvu. Ili ndi vuto lomwe ma capacitors onse amakumana nawo. Nkhani yomwe ndikunenayi ndi makulidwe a mafilimu. Mitundu yodziwika bwino ya ma capacitor imagwiritsa ntchito mafilimu okhuthala, zomwe zimapangitsa ma capacitor akulu kuposa mitundu ina. Filimu yowonda kwambiri imapangitsa kuti capacitor ikhale yochepa kwambiri kuti ichulukitse (magetsi, magetsi, kapena kutentha), ndipo sizingatheke kudzichiritsa yokha.
Ngati X capacitor sinalumikizidwe kwathunthu ndi magetsi, ndiye kuti simuyenera kuda nkhawa. Mwachitsanzo, kwa mankhwala omwe ali ndi chosinthira cholimba pakati pa magetsi ndi capacitor, kukula kungakhale kofunikira kwambiri kuposa moyo, ndiyeno mukhoza kusankha capacitor woonda.
Komabe, ngati capacitor ilumikizidwa kwamuyaya ndi gwero lamagetsi, iyenera kukhala yodalirika kwambiri. The makutidwe ndi okosijeni wa capacitors si mosalephera. Ngati capacitor epoxy material ndi yabwino ndipo capacitor nthawi zambiri imakhala yotentha kwambiri, kutsika kwa mtengo kuyenera kukhala kochepa.
M'nkhaniyi, poyamba adayambitsa chiphunzitso cha munda wa capacitors. Zitsanzo zothandiza ndi zotsatira zofananira zikuwonetsa momwe mungasankhire ndikugwiritsa ntchito mitundu yodziwika bwino ya capacitor. Tikukhulupirira kuti chidziwitsochi chingakuthandizeni kumvetsetsa bwino ntchito ya ma capacitor pakupanga zamagetsi ndi EMC.
Dr. Min Zhang ndi amene anayambitsa komanso mlangizi wamkulu wa EMC wa Mach One Design Ltd, kampani ya uinjiniya yochokera ku UK yomwe imagwira ntchito popanga upangiri wa EMC, kuthetsa mavuto ndi kuphunzitsa. Chidziwitso chake chakuya mumagetsi amagetsi, zamagetsi zamagetsi, magalimoto ndi mapangidwe azinthu zapindulitsa makampani padziko lonse lapansi.
Mu Compliance ndiye gwero lalikulu la nkhani, zambiri, maphunziro ndi kudzoza kwa akatswiri opanga zamagetsi ndi zamagetsi.
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