Basic fais fab mov qauv ntawmthem ceev ceevQC siv flyback + ob sab (secondary) synchronous rectification SSR. Rau flyback converters, raws li cov tswv yim sampling txoj kev, nws yuav muab faib mus rau hauv: thawj sab (primary) kev cai thiab theem nrab (secondary) kev cai; raws li qhov chaw ntawm PWM maub los. Nws tuaj yeem muab faib ua: thawj sab (primary) tswj thiab theem nrab (secondary) tswj. Nws zoo nkaus li tias nws tsis muaj dab tsi cuam tshuam nrog MOSFET. Yog li ntawd,Olukeyyuav tsum nug: MOSFET nyob qhov twg? Nws ua lub luag haujlwm dabtsi?
1. Thawj sab (thawj) hloov kho thiab theem nrab (thib ob) hloov kho
Kev ruaj ntseg ntawm cov zis hluav taws xob yuav tsum muaj kev tawm tswv yim txuas los xa nws cov ntaub ntawv hloov pauv mus rau PWM tus tswj hwm lub ntsiab kom kho cov kev hloov pauv hauv cov khoom siv hluav taws xob thiab cov khoom tso tawm. Raws li cov kev tawm tswv yim sib txawv, nws tuaj yeem muab faib ua thawj sab (primary) kev hloov kho thiab theem nrab (thib ob) kev hloov kho, raws li qhia hauv daim duab 1 thiab 2.
Lub tswv yim teeb liab ntawm thawj sab (primary) kev cai tsis yog coj ncaj qha los ntawm cov zis voltage, tab sis los ntawm cov pab winding los yog thawj thawj winding uas tuav ib tug proportional kev sib raug zoo nrog rau cov zis voltage. Nws cov yam ntxwv yog:
① Indirect tawm tswv yim txoj kev, tsis zoo load tswj tus nqi thiab tsis zoo raug;
②. Yooj yim thiab tus nqi qis;
③. Tsis xav tau kev sib cais optocoupler.
Lub teeb liab tawm tswv yim rau sab theem nrab (secondary) kev cai yog coj ncaj qha los ntawm cov zis hluav taws xob siv lub optocoupler thiab TL431. Nws cov yam ntxwv yog:
① Txoj kev tawm tswv yim ncaj qha, kev tswj hwm tus nqi zoo, kev tswj hwm tus nqi, thiab siab precision;
②. Kev hloov kho Circuit Court yog complex thiab kim;
③. Nws yog ib qho tsim nyog los cais cov optocoupler, uas muaj teeb meem kev laus thaum lub sij hawm.
2. Secondary sab (secondary) diode rectification thiabMOSFETsynchronous rectification SSR
Qhov thib ob sab (secondary) ntawm flyback converter feem ntau siv diode rectification vim yog cov zis loj tam sim no ntawm kev them nyiaj ceev. Tshwj xeeb tshaj yog rau kev them nyiaj ncaj qha lossis flash charging, cov zis tam sim no siab li 5A. Txhawm rau txhim kho kev ua tau zoo, MOSFET yog siv los hloov lub diode ua lub rectifier, uas yog hu ua theem nrab (secondary) synchronous rectification SSR, raws li qhia hauv daim duab 3 thiab 4.
Cov yam ntxwv ntawm theem nrab (secondary) diode rectification:
①. Yooj yim, tsis tas yuav muaj kev tswj hwm tsav ntxiv, thiab tus nqi qis;
② Thaum cov zis tam sim no loj, qhov ua tau zoo yog tsawg;
③. Kev ntseeg siab.
Nta ntawm theem nrab (secondary) MOSFET synchronous rectification:
①. complex, yuav tsum tau ntxiv tsav tswj thiab tus nqi siab;
②. Thaum cov zis tam sim no loj, qhov ua tau zoo yog siab;
③. Piv nrog rau diodes, lawv kev ntseeg siab yog tsawg.
Hauv kev siv cov tswv yim, MOSFET ntawm synchronous rectification SSR feem ntau yog txav los ntawm qhov siab kawg mus rau qhov qis kawg kom yooj yim rau kev tsav tsheb, raws li qhia hauv daim duab 5.
Cov yam ntxwv ntawm high-end MOSFET ntawm synchronous rectification SSR:
①. Nws yuav tsum tau bootstrap tsav lossis ntab tsav, uas yog kim;
②. Nyob zoo EMI.
Cov yam ntxwv ntawm synchronous rectification SSR MOSFET tso rau ntawm qhov kawg:
① Tsav ncaj, tsav yooj yim thiab tus nqi qis;
②. Poor EMI.
3. Thawj sab (primary) tswj thiab theem nrab (secondary) tswj
PWM lub ntsiab tswj tau muab tso rau ntawm thawj sab (primary). Cov qauv no hu ua thawj sab (primary) tswj. Txhawm rau txhim kho qhov tseeb ntawm qhov tso zis hluav taws xob, kev tswj hwm tus nqi, thiab kev tswj hwm tus nqi, tus thawj sab (primary) tswj yuav tsum muaj cov optocoupler sab nraud thiab TL431 los ua ib qho kev tawm tswv yim txuas. Lub kaw lus bandwidth me me thiab cov lus teb ceev qeeb.
Yog hais tias lub PWM lub ntsiab tswj tau muab tso rau ntawm qhov chaw thib ob (thib ob), lub optocoupler thiab TL431 tuaj yeem raug tshem tawm, thiab cov zis hluav taws xob tuaj yeem tswj tau ncaj qha thiab kho nrog cov lus teb ceev. Cov qauv no hu ua theem nrab (secondary) tswj.
Nta ntawm thawj sab (primary) tswj:
①. Optocoupler thiab TL431 yuav tsum tau, thiab cov lus teb ceev yog qeeb;
②. Qhov ceev ntawm cov zis tiv thaiv yog qeeb.
③. Nyob rau hauv synchronous rectification nruam hom CCM, lub thib ob sab (secondary) yuav tsum tau ib tug synchronization teeb liab.
Cov yam ntxwv ntawm theem nrab (secondary) tswj:
①. Cov zis tau pom ncaj qha, tsis muaj optocoupler thiab TL431 xav tau, cov lus teb ceev ceev, thiab cov zis tiv thaiv ceev ceev;
②. Qhov thib ob sab (secondary) synchronous rectification MOSFET yog tsav ncaj qha yam tsis tas yuav tsum muaj cov teeb liab synchronization; Cov khoom siv ntxiv xws li pulse transformers, magnetic couplings lossis capacitive couplers yuav tsum xa cov cim tsav tsheb ntawm thawj sab (primary) high-voltage MOSFET.
③. Thawj sab (primary) xav tau ib lub voj voog pib, lossis sab thib ob (secondary) muaj lub zog pabcuam rau kev pib.
4. Nruam CCM hom lossis hom DCM tsis tu ncua
Lub flyback converter tuaj yeem ua haujlwm hauv hom CCM tsis tu ncua lossis hom DCM tsis tu ncua. Yog tias qhov tam sim no nyob rau theem nrab (thib ob) winding ncav cuag 0 thaum kawg ntawm lub voj voog hloov, nws yog hu ua discontinuous DCM hom. Yog tias qhov tam sim no ntawm theem nrab (secondary) winding tsis yog 0 thaum kawg ntawm lub voj voog hloov, nws yog hu ua CCM hom txuas ntxiv, raws li pom hauv daim duab 8 thiab 9.
Nws tuaj yeem pom los ntawm daim duab 8 thiab daim duab 9 tias lub xeev ua haujlwm ntawm synchronous rectification SSR yog qhov sib txawv hauv kev ua haujlwm sib txawv ntawm flyback converter, uas kuj txhais tau hais tias cov kev tswj ntawm synchronous rectification SSR kuj yuav txawv.
Yog tias lub sijhawm tuag tsis quav ntsej, thaum ua haujlwm hauv CCM txuas ntxiv, lub synchronous rectification SSR muaj ob lub xeev:
①. Thawj sab (primary) high-voltage MOSFET yog qhib, thiab lub thib ob sab (secondary) synchronous rectification MOSFET yog muab tua;
②. Thawj sab (primary) high-voltage MOSFET yog muab tua, thiab lub thib ob sab (secondary) synchronous rectification MOSFET yog qhib.
Ib yam li ntawd, yog tias lub sijhawm tuag tsis quav ntsej, lub synchronous rectification SSR muaj peb lub xeev thaum ua haujlwm hauv hom DCM tsis tu ncua:
①. Thawj sab (primary) high-voltage MOSFET yog qhib, thiab lub thib ob sab (secondary) synchronous rectification MOSFET yog muab tua;
②. Thawj sab (primary) high-voltage MOSFET yog muab tua, thiab lub thib ob sab (secondary) synchronous rectification MOSFET yog qhib;
③. Thawj sab (primary) high-voltage MOSFET yog muab tua, thiab lub thib ob sab (secondary) synchronous rectification MOSFET yog muab tua.
5. Secondary side (secondary) synchronous rectification SSR nyob rau hauv tas li CCM hom
Yog hais tias tus ceev ceev-them flyback converter ua haujlwm nyob rau hauv lub nruam CCM hom, thawj sab (primary) tswj txoj kev, lub thib ob sab (secondary) synchronous rectification MOSFET yuav tsum tau ib tug synchronization teeb liab los ntawm thawj sab (primary) tswj lub kaw.
Ob txoj hauv qab no feem ntau yog siv kom tau txais cov teeb liab synchronous tsav ntawm sab thib ob (secondary):
(1) Ncaj nraim siv qhov sib txuas (secondary) winding, raws li qhia hauv daim duab 10;
(2) Siv cov khoom sib cais ntxiv xws li pulse transformers kom xa cov teeb liab synchronous tsav los ntawm thawj sab (primary) mus rau sab thib ob (thib ob), raws li qhia hauv daim duab 12.
Ncaj nraim siv qhov thib ob (secondary) winding kom tau txais lub teeb liab synchronous tsav, qhov tseeb ntawm lub teeb liab synchronous tsav yog qhov nyuaj heev rau kev tswj, thiab nws yog ib qho nyuaj rau kev ua tiav kev ua tau zoo thiab kev ntseeg tau. Qee lub tuam txhab txawm siv digital controllers los txhim kho kev tswj kom raug, raws li qhia hauv daim duab 11 Qhia.
Siv lub mem tes transformer kom tau txais cov cim tsav tsheb synchronous muaj qhov raug siab, tab sis tus nqi kuj tseem siab.
Txoj kev tswj hwm theem nrab (secondary) feem ntau yog siv lub tshuab hluav taws xob hloov pauv lossis sib nqus sib nqus kom xa cov teeb liab synchronous tsav los ntawm theem nrab (thib ob) mus rau thawj sab (primary), raws li qhia hauv daim duab 7.v
6. Secondary side (secondary) synchronous rectification SSR nyob rau hauv discontinuous DCM hom
Yog hais tias tus ceev ceev flyback converter ua haujlwm nyob rau hauv discontinuous DCM hom. Txawm hais tias tus thawj sab (primary) tswj txoj kev los yog theem nrab (secondary) tswj txoj kev, lub D thiab S voltage tee ntawm lub synchronous rectification MOSFET tuaj yeem tshawb pom ncaj qha thiab tswj.
(1) Tig rau synchronous rectification MOSFET
Thaum lub voltage ntawm VDS ntawm lub synchronous rectification MOSFET hloov los ntawm qhov zoo mus rau qhov tsis zoo, lub sab hauv parasitic diode tig rau, thiab tom qab ib tug tej yam ncua sij hawm, lub synchronous rectification MOSFET tig rau, raws li qhia nyob rau hauv daim duab 13.
(2) Tig tawm lub synchronous rectification MOSFET
Tom qab lub synchronous rectification MOSFET qhib, VDS = -Io * Rdson. Thaum qhov thib ob (thib ob) winding tam sim no txo qis rau 0, uas yog, thaum qhov hluav taws xob ntawm qhov ntsuas tam sim no VDS hloov ntawm qhov tsis zoo mus rau 0, lub synchronous rectification MOSFET tua, raws li qhia hauv daim duab 13.
Hauv kev siv cov tswv yim, lub synchronous rectification MOSFET tua ua ntej qhov thib ob (secondary) winding tam sim no mus txog 0 (VDS = 0). Qhov ntsuas tam sim no siv qhov ntsuas hluav taws xob tsim los ntawm cov chips sib txawv, xws li -20mV, -50mV, -100mV, -200mV, thiab lwm yam.
Qhov ntsuas tam sim no siv hluav taws xob ntawm qhov system yog tsau. Qhov ntau dua tus nqi ntawm qhov ntsuas tam sim no siv hluav taws xob, qhov cuam tshuam me me thiab qhov zoo dua qhov raug. Txawm li cas los xij, thaum cov zis load tam sim no Io txo qis, lub synchronous rectification MOSFET yuav tua ntawm qhov tso zis ntau dua tam sim no, thiab nws sab hauv parasitic diode yuav ua rau lub sijhawm ntev dua, yog li kev ua haujlwm tau txo qis, raws li pom hauv daim duab 14.
Tsis tas li ntawd, yog tias tus nqi tiag tiag ntawm qhov ntsuas tam sim no siv hluav taws xob tsawg dhau. Kev ua yuam kev thiab cuam tshuam yuav ua rau lub synchronous rectification MOSFET tua tom qab qhov thib ob (secondary) winding tam sim no tshaj 0, ua rau rov qab inflow tam sim no, cuam tshuam rau kev ua haujlwm thiab kev ntseeg tau ntawm lub cev.
High-precision tam sim no nrhiav tau cov teeb liab tuaj yeem txhim kho qhov ua tau zoo thiab kev ntseeg tau ntawm lub kaw lus, tab sis tus nqi ntawm cov cuab yeej yuav nce. Qhov tseeb ntawm lub teeb pom kev pom tam sim no muaj feem xyuam nrog cov hauv qab no:
①. Qhov tseeb thiab qhov kub thiab txias ntawm qhov ntsuas tam sim no siv voltage;
②. Qhov tsis zoo voltage thiab offset voltage, bias tam sim no thiab offset tam sim no, thiab kub drift ntawm tam sim no amplifier;
③. Qhov tseeb thiab kub drift ntawm on-voltage Rdson ntawm synchronous rectification MOSFET.
Tsis tas li ntawd, los ntawm qhov kev xav ntawm lub cev, nws tuaj yeem txhim kho los ntawm kev tswj hwm digital, hloov pauv qhov ntsuas tam sim no siv hluav taws xob, thiab hloov pauv synchronous rectification MOSFET tsav voltage.
Thaum cov zis load tam sim no Io txo, yog hais tias tus tsav voltage ntawm lub hwj chim MOSFET txo, tus coj MOSFET tig-on voltage Rdson nce. Raws li pom nyob rau hauv daim duab 15, nws yog ib qho ua tau kom tsis txhob raug kaw thaum ntxov ntawm lub synchronous rectification MOSFET, txo lub sij hawm conduction ntawm parasitic diode, thiab txhim kho cov efficiency ntawm lub system.
Nws tuaj yeem pom los ntawm daim duab 14 tias thaum cov zis load tam sim no Io txo qis, qhov ntsuas tam sim no siv hluav taws xob kuj txo. Nyob rau hauv no txoj kev, thaum cov zis tam sim no Io loj, ib tug ntau dua tam sim no nrhiav kom tau siv voltage yog siv los txhim kho kev tswj qhov tseeb; Thaum cov zis tam sim no Io qis, siv qhov ntsuas hluav taws xob qis dua tam sim no siv. Nws tuaj yeem txhim kho lub sijhawm ua haujlwm ntawm synchronous rectification MOSFET thiab txhim kho kev ua haujlwm ntawm lub cev.
Thaum cov txheej txheem saum toj no tsis tuaj yeem siv rau kev txhim kho, Schottky diodes kuj tseem tuaj yeem txuas nrog tib lub sijhawm ntawm ob qho kawg ntawm synchronous rectification MOSFET. Tom qab lub synchronous rectification MOSFET yog muab tua ua ntej, ib tug sab nraud Schottky diode tuaj yeem txuas rau freewheeling.
7. Secondary (secondary) tswj CCM + DCM hybrid hom
Tam sim no, muaj ob qho kev daws teeb meem feem ntau siv rau lub xov tooj ntawm tes ceev them:
(1) Thawj sab (primary) tswj thiab DCM ua haujlwm hom. Secondary side (secondary) synchronous rectification MOSFET tsis xav tau lub teeb liab synchronization.
(2) Secondary (secondary) tswj, CCM + DCM sib xyaw ua haujlwm hom (thaum cov zis load tam sim no txo qis, los ntawm CCM rau DCM). Qhov thib ob sab (secondary) synchronous rectification MOSFET yog tsav ncaj qha, thiab nws txoj cai tig-rau thiab tig-tawm cov ntsiab lus tau qhia hauv daim duab 16:
Tig rau lub synchronous rectification MOSFET: Thaum lub voltage ntawm VDS ntawm lub synchronous rectification MOSFET hloov ntawm qhov zoo mus rau qhov tsis zoo, nws sab hauv parasitic diode tig rau. Tom qab ib qho kev ncua sijhawm, lub synchronous rectification MOSFET tig rau.
Tig tawm lub synchronous rectification MOSFET:
① Thaum cov zis hluav taws xob tsawg dua li tus nqi teev, lub teeb liab synchronous moos yog siv los tswj kev tig tawm ntawm MOSFET thiab ua haujlwm hauv CCM hom.
② Thaum cov zis hluav taws xob ntau dua li cov nqi teeb tsa, lub teeb liab synchronous moos tau tiv thaiv thiab txoj kev ua haujlwm yog tib yam li DCM hom. Lub VDS = -Io * Rdson teeb liab tswj kev kaw ntawm synchronous rectification MOSFET.
Tam sim no, txhua tus paub tias lub luag haujlwm MOSFET ua haujlwm li cas hauv kev them nyiaj ceev QC!
Hais txog Olukey
Olukey pab pawg tseem ceeb tau tsom mus rau cov khoom siv rau 20 xyoo thiab yog lub hauv paus hauv Shenzhen. Kev lag luam loj: MOSFET, MCU, IGBT thiab lwm yam khoom siv. Cov khoom lag luam tseem ceeb yog WINSOK thiab Cmsemicon. Cov khoom siv dav siv hauv kev lag luam tub rog, kev tswj hwm kev lag luam, lub zog tshiab, cov khoom siv kho mob, 5G, Internet ntawm Yam, cov tsev ntse, thiab ntau yam khoom siv hluav taws xob. Kev vam khom rau qhov zoo ntawm thawj tus neeg sawv cev thoob ntiaj teb, peb ua raws li kev lag luam hauv Suav teb. Peb siv peb cov kev pabcuam zoo tshaj plaws los qhia txog ntau yam khoom siv hluav taws xob siab tshaj plaws rau peb cov neeg siv khoom, pab cov tuam txhab tsim cov khoom zoo thiab muab cov kev pabcuam zoo.
Post lub sij hawm: Dec-14-2023
