Lim capacitors ua lub luag haujlwm tseem ceeb hauv kev hloov cov khoom siv hluav taws xob. Yuav ua li cas kom raug xaiv lim capacitors, tshwj xeeb tshaj yog xaiv cov zis lim capacitors, yog ib qho teeb meem uas txhua tus engineer thiab cov kws tshaj lij muaj kev txhawj xeeb heev. Peb tuaj yeem pom ntau yam ntawm cov capacitors nyob rau hauv lub hwj chim lim Circuit Court, 100uF, 10uF, 100nF, 10nF txawv capacitance qhov tseem ceeb, yog li cov kev ntsuas no tau txiav txim siab li cas? Tsis txhob qhia kuv tias kuv tau theej lwm tus schematic, huh.
Cov electrolytic capacitor siv nyob rau hauv 50Hz fais fab zaus Circuit Court muaj ib tug pulsating voltage zaus ntawm tsuas yog 100Hz, thiab lub sij hawm them thiab tawm yog nyob rau hauv qhov kev txiav txim ntawm milliseconds. Yuav kom tau txais ib qho me me pulsation coefficient, qhov yuav tsum tau muaj peev xwm yog siab li ntau pua txhiab tus μF, yog li lub hom phiaj ntawm cov khoom siv hluav taws xob tsawg tsawg ntawm txhuas electrolytic capacitors yog ua kom muaj peev xwm. Lub ntsiab parameter ntawm pros thiab cons. Cov zis lim electrolytic capacitor nyob rau hauv cov khoom siv hluav taws xob hloov pauv muaj cov sawtooth yoj voltage zaus siab li kaum tawm kHz lossis txawm kaum ntawm MHz. Lub sijhawm no, lub capacitance tsis yog nws qhov taw qhia tseem ceeb. Tus qauv ntsuas qhov zoo ntawm high-frequency aluminium electrolytic capacitors yog "impedance-Frequency" yam ntxwv, yuav tsum muaj qhov sib npaug qis dua nyob rau hauv kev khiav hauj lwm zaus ntawm kev hloov hluav taws xob, thiab tib lub sij hawm muaj kev lim dej zoo ntawm qhov siab- zaus cov teeb liab tshwm sim thaum cov khoom siv semiconductor ua haujlwm.
Ordinary low-frequency electrolytic capacitors pib qhia inductance nyob ib ncig ntawm 10kHz, uas tsis tuaj yeem ua tau raws li qhov xav tau ntawm kev hloov khoom siv hluav taws xob. Lub high-frequency txhuas electrolytic capacitors nplooj siab rau switching fais fab mov muaj plaub terminals. Tam sim no ntws los ntawm ib qho zoo kawg ntawm plaub-terminal capacitor, dhau los ntawm sab hauv ntawm lub capacitor, thiab tom qab ntawd ntws los ntawm lwm qhov kawg mus rau qhov load; tam sim no rov qab los ntawm lub load kuj ntws los ntawm ib tug tsis zoo kawg ntawm lub capacitor, thiab ces ntws los ntawm lwm yam tsis zoo kawg mus rau qhov tsis zoo kawg ntawm lub hwj chim mov.
Txij li thaum plaub lub davhlau ya nyob twg capacitor muaj cov yam ntxwv siab zaus, nws muab ib qho txiaj ntsig zoo heev rau kev txo cov pulsating tivthaiv ntawm qhov hluav taws xob thiab suppressing lub suab nrov ntawm lub suab nrov. High-frequency aluminium electrolytic capacitors kuj muaj ntau daim ntawv, uas yog, cov ntawv txhuas txhuas tau muab faib ua ob peb ntu luv, thiab ntau cov ntawv txhuas tawm tau txuas nrog rau qhov sib npaug los txo cov impedance tivthaiv hauv capacitive reactance. Thiab cov khoom uas tsis tshua muaj resistivity yog siv los ua cov hlau lead-tawm davhlau ya nyob twg, uas txhim kho lub peev xwm ntawm lub capacitor kom tiv taus cov dej loj.
Lub tshuab hluav taws xob digital yuav tsum ua haujlwm ruaj khov thiab ntseeg tau, cov khoom siv hluav taws xob yuav tsum "huv", thiab cov khoom siv hluav taws xob yuav tsum tau raws sijhawm, uas yog, lim thiab decoupling yuav tsum zoo. Dab tsi yog lim decoupling, yooj yim muab, nws khaws lub zog thaum lub nti tsis xav tau tam sim no, thiab kuv tuaj yeem rov ntxiv zog rau lub sijhawm koj xav tau tam sim no. Tsis txhob qhia kuv tias lub luag haujlwm no tsis yog lub luag haujlwm ntawm DCDC thiab LDO? Yog lawm, lawv tuaj yeem ua haujlwm ntawm qhov tsawg zaus, tab sis cov tshuab digital ceev sib txawv.
Cia peb saib ntawm lub capacitor ua ntej. Lub luag haujlwm ntawm lub capacitor tsuas yog khaws cov nqi xwb. Peb txhua tus paub tias capacitor filtering yuav tsum tau ntxiv rau lub hwj chim mov, thiab ib tug {{{0}}}.1uF capacitor yuav tsum tau muab tso rau ntawm lub hwj chim mov pin ntawm txhua nti rau decoupling, thiab lwm yam. Vim li cas kuv thiaj li pom tias cov capacitor ntawm ib sab ntawm lub hwj chim mov tus pin ntawm qee lub board chips yog 0.1uF lossis 0.01uF Yog, nws puas tseem ceeb? Yuav kom nkag siab qhov no, nws yog ib qho tsim nyog yuav tsum nkag siab txog cov yam ntxwv ntawm cov capacitors. Ib qho zoo tagnrho capacitor tsuas yog ib qho chaw cia khoom xwb, C. Txawm li cas los xij, qhov tseeb tsim capacitor tsis yooj yim li. Thaum txheeb xyuas lub zog ncaj ncees, peb feem ntau siv cov qauv capacitor.
Yuav ua li cas xaiv cov lim capacitors hauv kev hloov hluav taws xob tsim?
ESR yog qhov sib npaug sib npaug ntawm lub capacitor, ESL yog qhov sib npaug inductance ntawm lub capacitor, thiab C yog qhov zoo tagnrho capacitor. ESR thiab ESL yog txiav txim los ntawm cov txheej txheem tsim khoom thiab cov khoom siv ntawm lub capacitor thiab tsis tuaj yeem raug tshem tawm. Ob yam no cuam tshuam li cas rau hauv Circuit Court? ESR cuam tshuam lub ripple ntawm lub hwj chim mov, thiab ESL cuam tshuam rau lub lim zaus yam ntxwv ntawm lub capacitor.
Peb paub tias lub capacitive reactance ntawm capacitor Zc =1 / ωC, inductive reactance ntawm inductor Zl =ωL, (ω=2πf), qhov nyuaj impedance ntawm lub capacitor tiag tiag yog Z=ESR plus jωL-1/jωC=ESR plus j2πf L-1/j2πf C. Nws tuaj yeem pom tau tias thaum qhov zaus tsawg heev, lub capacitance plays a lub luag hauj lwm, thiab thaum lub zaus nce mus txog ib theem, lub luag hauj lwm ntawm inductance yuav tsis raug ignored, thiab thaum lub zaus yog siab, lub inductance plays lub luag hauj lwm. Capacitors poob lawv cov nyhuv lim dej. Yog li nco ntsoov, capacitors tsis yog cov capacitors ntawm cov zaus siab.
Raws li tau hais los saum no, qhov sib npaug series inductance ntawm lub capacitor yog txiav txim siab los ntawm cov txheej txheem tsim khoom thiab cov khoom siv ntawm lub capacitor. ESL ntawm qhov tseeb nti ceramic capacitor ranges ntawm ob peb feem kaum ntawm nH mus rau ntau nH. Lub pob me me, qhov me dua ESL.
Ntawm lub lim nkhaus ntawm lub capacitor, peb kuj tuaj yeem pom tias nws tsis tiaj tus, nws zoo li 'V', uas txhais tau hais tias nws muaj cov yam ntxwv xaiv zaus. Qee zaum koj xav kom nws ua kom ntse li sai tau (filtered lossis notch). Dab tsi cuam tshuam rau tus yam ntxwv no yog qhov ua tau zoo Q ntawm lub capacitor, Q{{0}}/ωCESR. Qhov loj dua ESR, qhov me Q, thiab qhov nkhaus nkhaus. Ntawm qhov tsis sib xws, qhov me dua ESR, qhov loj dua Q, thiab qhov nkhaus nkhaus. Feem ntau, tantalum capacitors thiab txhuas electrolysis muaj qhov me me ESL thiab loj ESR, yog li tantalum capacitors thiab txhuas electrolysis muaj ntau zaus siv tau, uas yog qhov tsim nyog rau kev lim dej ua ntej-theem board-level filtering. Ntawd yog, theem nkag ntawm DCDC lossis LDO feem ntau lim nrog lub peev xwm loj dua tantalum capacitor. Thiab muab qee qhov 10uF thiab 0.1uF capacitors ze rau lub nti rau kev txiav, ceramic capacitors muaj ESR tsawg heev.
