xov xwm

Capacitors yog ib qho ntawm cov khoom siv feem ntau siv rau hauv Circuit Court boards. Raws li tus naj npawb ntawm cov khoom siv hluav taws xob (los ntawm cov xov tooj ntawm tes mus rau lub tsheb) tseem nce ntxiv, yog li qhov kev thov rau capacitors. Covid 19 kev kis thoob ntiaj teb tau cuam tshuam cov khoom lag luam thoob ntiaj teb los ntawm cov khoom siv hluav taws xob mus rau cov khoom siv tsis zoo, thiab cov khoom siv hluav taws xob tau poob qis 1.
Kev sib tham txog lub ntsiab lus ntawm cov capacitors tuaj yeem hloov tau yooj yim rau hauv phau ntawv lossis phau ntawv txhais lus. Ua ntej, muaj ntau hom capacitors, xws li electrolytic capacitors, zaj duab xis capacitors, ceramic capacitors thiab lwm yam. Tom qab ntawd, nyob rau hauv tib hom, muaj cov khoom sib txawv dielectric. Kuj tseem muaj cov chav kawm sib txawv. Raws li rau lub cev qauv, muaj ob-terminal thiab peb-terminal capacitor hom. Kuj tseem muaj X2Y hom capacitor, uas yog qhov tseem ceeb ntawm khub Y capacitor encapsulated hauv ib qho. Yuav ua li cas yog supercapacitors? Qhov tseeb yog, yog tias koj zaum thiab pib nyeem cov lus qhia xaiv capacitor los ntawm cov tuam txhab loj, koj tuaj yeem siv sijhawm ntev!
Txij li cov kab lus no yog hais txog cov hauv paus, kuv yuav siv lwm txoj hauv kev li niaj zaus. Raws li tau hais ua ntej, cov lus qhia xaiv capacitor tuaj yeem pom tau yooj yim ntawm cov chaw muag khoom lub vev xaib 3 thiab 4, thiab cov kws ua haujlwm hauv teb tuaj yeem teb cov lus nug feem ntau txog cov capacitors. Hauv tsab xov xwm no, kuv yuav tsis rov hais dua qhov koj tuaj yeem nrhiav tau hauv Is Taws Nem, tab sis yuav ua qauv qhia yuav ua li cas xaiv thiab siv cov capacitors los ntawm kev ua piv txwv. Qee qhov tsis paub tsawg dua ntawm kev xaiv capacitor, xws li kev degradation capacitance, kuj yuav raug them. Tom qab nyeem tsab xov xwm no, koj yuav tsum muaj kev nkag siab zoo ntawm kev siv cov capacitors.
Ntau xyoo dhau los, thaum kuv ua haujlwm hauv ib lub tuam txhab uas tsim cov khoom siv hluav taws xob, peb muaj lus nug rau ib tus kws tshaj lij hluav taws xob hluav taws xob. Ntawm daim duab schematic ntawm cov khoom uas twb muaj lawm, peb yuav nug cov neeg sib tw "Dab tsi yog qhov ua haujlwm ntawm DC txuas electrolytic capacitor?" thiab "Dab tsi yog kev ua haujlwm ntawm ceramic capacitor nyob ib sab ntawm lub nti?" Peb cia siab tias cov lus teb raug yog DC bus capacitor Siv rau lub zog cia, ceramic capacitor yog siv rau lim.
Cov lus teb "yog" peb nrhiav tau tiag tiag qhia tau tias txhua tus neeg ntawm pab pawg tsim saib ntawm cov khoom siv hluav taws xob los ntawm qhov yooj yim Circuit Court foundations, tsis yog los ntawm kev xav hauv cheeb tsam. Lub ntsiab lus ntawm qhov kev xav ntawm circuit theory tsis yog yuam kev. Ntawm qhov tsawg zaus (los ntawm ob peb kHz mus rau ob peb MHz), circuit theory feem ntau tuaj yeem piav qhia qhov teeb meem zoo. Qhov no yog vim hais tias ntawm qis frequencies, lub teeb liab feem ntau yog nyob rau hauv txawv hom. Siv cov kev xav hauv Circuit Court, peb tuaj yeem pom lub capacitor qhia hauv daim duab 1, qhov twg qhov sib npaug series tsis kam (ESR) thiab sib npaug series inductance (ESL) ua rau impedance ntawm lub capacitor hloov nrog zaus.
Cov qauv no piav qhia tag nrho cov kev ua haujlwm hauv Circuit Court thaum lub voj voog hloov maj mam. Txawm li cas los xij, raws li qhov ntau zaus, tej yam yuav nyuaj dua. Qee lub sij hawm, cov khoom siv pib qhia tsis yog linearity. Thaum qhov zaus nce, tus qauv LCR yooj yim muaj nws cov kev txwv.
Niaj hnub no, yog tias kuv raug nug tib lo lus nug sib tham, kuv yuav hnav kuv qhov kev tshawb xav tsom iav tsom iav thiab hais tias ob hom capacitor yog lub zog cia khoom. Qhov txawv yog tias electrolytic capacitor tuaj yeem khaws ntau lub zog ntau dua li ceramic capacitors. Tab sis nyob rau hauv cov nqe lus ntawm lub zog kis tau tus mob, ceramic capacitors yuav kis tau lub zog sai dua. Qhov no piav qhia vim li cas cov capacitors ceramic yuav tsum tau muab tso rau ib sab ntawm lub nti, vim tias cov nti muaj qhov hloov pauv ntau dua thiab hloov nrawm dua piv rau lub zog hluav taws xob loj.
Los ntawm qhov kev xav no, peb tuaj yeem txhais ob qho qauv kev ua haujlwm rau cov capacitors. Ib qho yog lub zog npaum li cas lub capacitor tuaj yeem khaws cia, thiab lwm qhov yog qhov ceev npaum li cas lub zog tuaj yeem xa mus. Ob leeg nyob ntawm txoj kev tsim khoom ntawm lub capacitor, cov khoom siv dielectric, kev sib txuas nrog lub capacitor, thiab lwm yam.
Thaum qhov hloov pauv hauv Circuit Court raug kaw (saib daim duab 2), nws qhia tau hais tias lub load xav tau lub zog los ntawm lub zog hluav taws xob. Qhov ceev ntawm qhov kev hloov no kaw txiav txim siab qhov ceev ntawm lub zog xav tau. Txij li thaum lub zog mus ntawm qhov ceev ntawm lub teeb (ib nrab ntawm qhov ceev ntawm lub teeb hauv FR4 cov ntaub ntawv), nws yuav siv sij hawm los hloov lub zog. Tsis tas li ntawd, muaj ib qho impedance mismatch ntawm qhov chaw thiab cov kab sib kis thiab cov load. Qhov no txhais tau hais tias lub zog yuav tsis raug xa mus rau hauv ib qho kev mus ncig, tab sis nyob rau hauv ntau qhov kev mus ncig 5, uas yog vim li cas thaum lub hloov pauv sai, peb yuav pom kev qeeb thiab lub suab nrov hauv qhov hloov pauv waveform.
Daim duab 2: Nws siv sijhawm rau lub zog los nthuav tawm hauv qhov chaw; impedance mismatch ua rau ntau qhov kev mus ncig ntawm lub zog hloov pauv.
Qhov tseeb tias kev xa hluav taws xob siv sijhawm thiab ntau qhov kev mus ncig qhia peb tias peb yuav tsum txav lub zog kom ze li sai tau rau lub nra, thiab peb yuav tsum nrhiav txoj hauv kev kom xa nws sai. Thawj yog feem ntau ua tiav los ntawm kev txo lub cev qhov deb ntawm lub load, hloov thiab capacitor. Cov tom kawg yog ua tiav los ntawm kev sib sau ua ke ib pawg ntawm cov capacitors nrog qhov tsawg tshaj plaws impedance.
Field theory kuj piav qhia txog dab tsi ua rau lub suab nrov nrov. Nyob rau hauv luv luv, hom suab nrov yog generated thaum lub zog thov ntawm lub load tsis tau raws li thaum lub sij hawm hloov. Yog li ntawd, lub zog khaws cia hauv qhov chaw nruab nrab ntawm cov khoom thauj thiab cov neeg nyob ze yuav raug muab los txhawb cov kauj ruam thov. Qhov chaw nruab nrab ntawm cov khoom thauj thiab cov neeg ua haujlwm nyob ze yog qhov peb hu ua parasitic/mutual capacitance (saib daim duab 2).
Peb siv cov piv txwv hauv qab no los ua kom pom kev siv cov khoom siv hluav taws xob electrolytic, multilayer ceramic capacitors (MLCC), thiab zaj duab xis capacitors. Ob qho tib si Circuit Court thiab teb txoj kev xav yog siv los piav qhia qhov ua tau zoo ntawm cov khoom siv hluav taws xob xaiv.
Electrolytic capacitor feem ntau yog siv hauv DC txuas ua lub zog loj. Kev xaiv ntawm electrolytic capacitor feem ntau nyob ntawm:
Rau EMC kev ua tau zoo, cov yam ntxwv tseem ceeb tshaj plaws ntawm cov capacitors yog impedance thiab zaus yam ntxwv. Tsawg zaus ua emissions ib txwm nyob ntawm qhov ua tau zoo ntawm DC txuas capacitor.
Lub impedance ntawm DC txuas tsis tsuas yog nyob ntawm ESR thiab ESL ntawm lub capacitor, tab sis kuj nyob rau thaj tsam ntawm lub voj voog thermal, raws li pom hauv daim duab 3. Qhov loj dua thermal voj cheeb tsam txhais tau hais tias lub zog hloov mus ntev dua, yog li kev ua tau zoo. yuav raug cuam tshuam.
Ib kauj ruam-down DC-DC converter tau tsim los ua pov thawj qhov no. Kev teeb tsa ua ntej EMC kuaj pom nyob rau hauv daim duab 4 ua ib qho kev ntsuas emission ntawm 150kHz thiab 108MHz.
Nws yog ib qho tseem ceeb kom ntseeg tau tias cov capacitors siv nyob rau hauv cov ntaub ntawv kawm no yog tag nrho los ntawm tib lub chaw tsim tshuaj paus kom tsis txhob muaj qhov sib txawv ntawm impedance yam ntxwv. Thaum soldering lub capacitor ntawm PCB, xyuas kom meej tias tsis muaj cov hlau lead ntev, vim qhov no yuav ua rau ESL ntawm lub capacitor nce. Daim duab 5 qhia txog peb qhov kev teeb tsa.
Cov txiaj ntsig tau ua tawm ntawm peb qhov kev teeb tsa no tau pom hauv daim duab 6. Nws tuaj yeem pom tau tias, piv nrog ib qho 680 µF capacitor, ob lub 330 µF capacitors ua tiav lub suab nrov txo qhov kev ua tau zoo ntawm 6 dB dhau qhov ntau zaus.
Los ntawm txoj kev xav hauv Circuit Court, nws tuaj yeem hais tau tias los ntawm kev txuas ob lub capacitors nyob rau hauv parallel, ob qho tib si ESL thiab ESR yog halved. Los ntawm qhov kev xav ntawm qhov kev xav, tsis yog tsuas yog ib lub zog xwb, tab sis ob lub zog tau muab rau tib lub sijhawm, txo cov sijhawm sib kis ntawm lub zog tag nrho. Txawm li cas los xij, ntawm ntau zaus, qhov sib txawv ntawm ob 330 µF capacitor thiab ib qho 680 µF capacitor yuav ntsws. Qhov no yog vim lub suab nrov nrov qhia tsis txaus cov kauj ruam lub zog teb. Thaum tsiv lub 330 µF capacitor los ze zog mus rau qhov hloov, peb txo lub sij hawm hloov lub zog, uas ua rau kom cov kauj ruam teb ntawm lub capacitor.
Qhov tshwm sim qhia peb ib zaj lus qhia tseem ceeb heev. Kev nce lub peev xwm ntawm ib lub capacitor feem ntau yuav tsis txhawb cov kauj ruam thov kom muaj zog ntxiv. Yog tias ua tau, siv qee cov khoom me me capacitive. Muaj ntau qhov laj thawj zoo rau qhov no. Thawj yog tus nqi. Feem ntau hais lus, rau tib lub pob loj, tus nqi ntawm lub capacitor nce exponentially nrog tus nqi capacitance. Siv ib lub capacitor yuav kim dua li siv ob peb lub capacitor me. Qhov thib ob yog vim li cas loj. Qhov kev txwv ntawm cov khoom tsim feem ntau yog qhov siab ntawm cov khoom. Rau qhov loj-tswj capacitors, qhov siab yog feem ntau loj heev, uas tsis haum rau cov khoom tsim. Qhov thib peb yog vim li cas EMC qhov kev ua tau zoo uas peb tau pom hauv cov ntaub ntawv kawm.
Lwm qhov tseem ceeb uas yuav tsum tau xav txog thaum siv lub tshuab hluav taws xob electrolytic yog tias thaum koj txuas ob lub capacitor hauv series los qhia qhov voltage, koj yuav xav tau qhov ntsuas qhov ntsuas 6.
Raws li tau hais ua ntej, ceramic capacitors yog cov khoom siv me me uas tuaj yeem muab lub zog sai. Kuv feem ntau nug cov lus nug "Kuv xav tau capacitor npaum li cas?" Cov lus teb rau lo lus nug no yog tias rau ceramic capacitors, tus nqi capacitance yuav tsum tsis yog qhov tseem ceeb. Qhov kev txiav txim siab tseem ceeb ntawm no yog los txiav txim seb qhov twg zaus lub zog hloov pauv ceev txaus rau koj daim ntawv thov. Yog tias qhov kev tso tawm ua tsis tiav ntawm 100 MHz, lub capacitor nrog qhov tsawg tshaj plaws impedance ntawm 100 MHz yuav yog qhov kev xaiv zoo.
Qhov no yog lwm qhov kev nkag siab yuam kev ntawm MLCC. Kuv tau pom engineers siv ntau lub zog xaiv ceramic capacitors nrog qis tshaj ESR thiab ESL ua ntej txuas cov capacitors rau RF siv taw tes los ntawm cov kab ntev. Nws yog tsim nyog hais tias ESL ntawm MLCC feem ntau qis dua qhov kev sib txuas inductance ntawm lub rooj tsavxwm. Kev sib txuas inductance tseem yog qhov tseem ceeb tshaj plaws uas cuam tshuam rau lub siab zaus impedance ntawm ceramic capacitors7.
Daim duab 7 qhia ib qho piv txwv phem. Cov kab ntev (0.5 ntiv tes ntev) qhia tsawg kawg 10nH inductance. Cov txiaj ntsig simulation qhia tau hais tias qhov impedance ntawm lub capacitor ua ntau dua qhov xav tau ntawm qhov zaus taw tes (50 MHz).
Ib qho ntawm cov teeb meem nrog MLCCs yog tias lawv zoo li resonate nrog cov qauv inductive ntawm lub rooj tsavxwm. Qhov no tuaj yeem pom hauv qhov piv txwv qhia hauv daim duab 8, qhov twg kev siv 10 µF MLCC qhia txog kev sib tw ntawm kwv yees li 300 kHz.
Koj tuaj yeem txo qis resonance los ntawm kev xaiv cov khoom siv nrog ESR loj dua lossis tsuas yog tso tus nqi me me (xws li 1 ohm) hauv koob nrog lub capacitor. Hom kev siv no siv lossy Cheebtsam los suppress lub system. Lwm txoj hauv kev yog siv lwm tus nqi capacitance txav lub resonance mus rau qhov qis dua lossis siab dua resonance point.
Zaj duab xis capacitors yog siv nyob rau hauv ntau daim ntawv thov. Lawv yog cov capacitors ntawm kev xaiv rau high-power DC-DC converters thiab yog siv raws li EMI suppression lim nyob rau hauv lub hwj chim kab (AC thiab DC) thiab ntau hom lim configurations. Peb coj ib qho X capacitor ua piv txwv los piav txog qee cov ntsiab lus tseem ceeb ntawm kev siv zaj duab xis capacitor.
Yog tias muaj qhov tshwm sim tshwm sim, nws yuav pab txo qhov siab tshaj qhov siab ntawm txoj kab, yog li nws feem ntau yog siv nrog lub zog hluav taws xob hloov pauv (TVS) lossis hlau oxide varistor (MOV).
Tej zaum koj twb paub tag nrho cov no, tab sis koj puas paub tias tus nqi capacitance ntawm X capacitor tuaj yeem txo qis nrog ntau xyoo? Qhov no yog qhov tseeb tshwj xeeb yog tias lub capacitor siv nyob rau hauv qhov chaw ntub dej. Kuv tau pom tus nqi capacitance ntawm X capacitor tsuas yog poob rau ob peb feem pua ​​​​ntawm nws cov nqi ntsuas nyob rau hauv ib xyoos lossis ob xyoos, yog li lub kaw lus pib tsim nrog X capacitor tiag tiag poob tag nrho cov kev tiv thaiv uas lub hauv ntej-kawg capacitor yuav muaj.
Yog li, ua li cas? Cov huab cua noo tuaj yeem nkag mus rau hauv lub capacitor, nce cov hlau thiab nruab nrab ntawm lub thawv thiab cov epoxy potting compound. Tom qab ntawd lub aluminium metallization tuaj yeem oxidized. Alumina yog ib qho hluav taws xob zoo hluav taws xob, yog li txo qis capacitance. Qhov no yog ib qho teeb meem uas txhua zaj duab xis capacitors yuav ntsib. Qhov teeb meem kuv tab tom tham txog yog zaj duab xis thickness. Reputable capacitor hom siv cov yeeb yaj kiab tuab, ua rau cov capacitor loj dua li lwm hom. Cov zaj duab xis nyias ua rau lub capacitor tsis tshua muaj zog kom dhau (voltage, tam sim no, lossis kub), thiab nws tsis zoo li kho nws tus kheej.
Yog tias X capacitor tsis txuas mus tas li rau lub hwj chim, ces koj tsis tas yuav txhawj xeeb. Piv txwv li, rau ib yam khoom uas muaj ib tug nyuaj hloov ntawm lub hwj chim mov thiab lub capacitor, qhov luaj li cas tej zaum yuav tseem ceeb tshaj lub neej, thiab ces koj muaj peev xwm xaiv ib tug nyias nyias capacitor.
Txawm li cas los xij, yog tias lub capacitor txuas mus tas li rau lub zog hluav taws xob, nws yuav tsum muaj kev ntseeg siab heev. Lub oxidation ntawm capacitors yog tsis tsim nyog. Yog tias cov khoom siv capacitor epoxy yog qhov zoo thiab lub capacitor tsis feem ntau raug rau qhov kub thiab txias, qhov poob ntawm tus nqi yuav tsum tsawg.
Hauv tsab xov xwm no, thawj zaug tau qhia txog qhov kev xav pom ntawm cov capacitors. Cov qauv ua piv txwv thiab cov txiaj ntsig simulation qhia yuav ua li cas xaiv thiab siv hom capacitor feem ntau. Vam tias cov ntaub ntawv no tuaj yeem pab koj nkag siab lub luag haujlwm ntawm cov khoom siv hluav taws xob hauv hluav taws xob thiab EMC tsim kom paub meej ntxiv.
Dr. Min Zhang yog tus tsim thiab tus thawj coj EMC tus kws pab tswv yim ntawm Mach One Design Ltd, lub tuam txhab ua haujlwm hauv UK tshwj xeeb hauv EMC kev sab laj, kev daws teeb meem thiab kev cob qhia. Nws qhov kev paub tob hauv hluav taws xob hluav taws xob, digital electronics, motors thiab cov khoom tsim tau muaj txiaj ntsig zoo rau cov tuam txhab thoob ntiaj teb.
Hauv Kev Ua Raws Cai yog qhov tseem ceeb ntawm cov xov xwm, cov ntaub ntawv, kev kawm thiab kev tshoov siab rau cov kws tshaj lij hluav taws xob thiab hluav taws xob engineering.
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