Kusintha kwamphamvu kwamphamvu sikungapeweke. Cholinga chathu chachikulu ndikuchepetsa ma ripples kuti apirire. Yankho lofunika kwambiri kuti mukwaniritse cholingachi ndikupewa kubadwa kwa ma ripples. Choyamba ndi chifukwa.
Ndi kusintha kwa SWITCH, panopa mu inductance L imasinthasinthanso mmwamba ndi pansi pamtengo wovomerezeka wa zomwe zimachokera. Chifukwa chake, padzakhalanso ripple yomwe imakhala yofanana pafupipafupi monga Sinthani pamapeto otuluka. Nthawi zambiri, ma ripples a riber amatanthauza izi, zomwe zimagwirizana ndi kuchuluka kwa capacitor ndi ESR. Mafupipafupi a ripple iyi ndi yofanana ndi magetsi osinthika, okhala ndi makumi khumi mpaka mazana a kHz.
Kuphatikiza apo, Switch nthawi zambiri imagwiritsa ntchito ma transistors a bipolar kapena ma MOSFET. Ziribe kanthu kuti ndi chiyani, padzakhala nthawi yokwera ndi yochepa pamene idzayatsidwa ndikufa. Panthawiyi, sipadzakhala phokoso mu dera lomwe liri lofanana ndi nthawi yowonjezera monga Kusintha kwa nthawi yocheperapo, kapena kangapo, ndipo kawirikawiri ndi makumi a MHz. Mofananamo, diode D imabwereranso kumbuyo. Dera lofanana ndi mndandanda wa ma capacitor otsutsa ndi ma inductors, omwe angayambitse kumveka, ndipo ma frequency a phokoso ndi makumi a MHz. Phokoso ziwirizi nthawi zambiri zimatchedwa phokoso lapamwamba, ndipo matalikidwe ake nthawi zambiri amakhala okulirapo kuposa phokosolo.
Ngati ndi chosinthira cha AC / DC, kuwonjezera pa ma ripples awiri omwe ali pamwambapa (phokoso), palinso phokoso la AC. Mafupipafupi ndi kuchuluka kwa magetsi a AC, pafupifupi 50-60Hz. Palinso phokoso la co-mode, chifukwa chipangizo chamagetsi chamagetsi ambiri osinthira magetsi chimagwiritsa ntchito chipolopolo ngati radiator, chomwe chimapanga mphamvu yofanana.
Kuyeza kwa kusintha ma ripples amagetsi
Zofunikira zofunika:
Kulumikizana ndi oscilloscope AC
20MHz bandwidth malire
Chotsani waya wapansi wa probe
Kuphatikizika kwa 1.AC ndikochotsa voteji ya superposition DC ndikupeza mawonekedwe olondola.
2. Kutsegula malire a 20MHz bandwidth ndikuletsa kusokoneza kwa phokoso lapamwamba komanso kupewa kulakwitsa. Chifukwa matalikidwe a mawonekedwe apamwamba kwambiri ndi akulu, ayenera kuchotsedwa akayezedwa.
3. Chotsani chidutswa cha pansi cha probe ya oscilloscope, ndipo gwiritsani ntchito muyeso wa nthaka kuti muchepetse kusokoneza. Madipatimenti ambiri alibe mphete zoyambira. Koma taganizirani mfundo imeneyi poweruza ngati ili yoyenerera.
Mfundo ina ndikugwiritsa ntchito terminal ya 50Ω. Malinga ndi chidziwitso cha oscilloscope, gawo la 50Ω ndikuchotsa gawo la DC ndikuyesa molondola gawo la AC. Komabe, pali ma oscilloscope ochepa okhala ndi ma probe apadera. Nthawi zambiri, kugwiritsa ntchito ma probes kuyambira 100kΩ mpaka 10MΩ amagwiritsidwa ntchito, zomwe sizikudziwika kwakanthawi.
Zomwe zili pamwambazi ndizodzitetezera poyesa kusintha kwamadzi. Ngati kafukufuku wa oscilloscope sanawonekere potuluka, ayenera kuyezedwa ndi mizere yopotoka kapena 50Ω zingwe za coaxial.
Mukayesa phokoso lapamwamba kwambiri, gulu lonse la oscilloscope nthawi zambiri limakhala mazana a mega mpaka GHz. Zina ndi zofanana ndi zomwe zili pamwambazi. Mwina makampani osiyanasiyana ali ndi njira zoyesera zosiyanasiyana. Pomaliza, muyenera kudziwa zotsatira za mayeso anu.
Za oscilloscope:
Ma oscilloscope ena a digito sangathe kuyeza ma ripples molondola chifukwa cha kusokoneza ndi kuya kwa kusungirako. Panthawi imeneyi, oscilloscope iyenera kusinthidwa. Nthawi zina ngakhale kayeseleledwe akale oscilloscope bandiwifi ndi makumi a mega, ntchito ndi bwino kuposa digito oscilloscope.
Kuletsa kusintha ma ripples amagetsi
Kwa kusintha ma ripples, mwamalingaliro komanso alipo. Pali njira zitatu zochepetsera kapena kuchepetsa:
1. Wonjezerani inductance ndi linanena bungwe capacitor kusefa
Malinga ndi mawonekedwe a magetsi osinthira, kukula kwa kusinthasintha kwapano ndi mtengo wa inductance wa inductance inductance umakhala wofanana, ndipo ma ripples otulutsa ndi ma capacitor otulutsa amakhala molingana. Chifukwa chake, kuwonjezera ma capacitor amagetsi ndi zotulutsa kumatha kuchepetsa ma ripples.
Chithunzi chomwe chili pamwambapa ndi mawonekedwe apano mu chosinthira magetsi chosinthira magetsi L. Ripple current △ nditha kuwerengedwa kuchokera munjira iyi:
Zitha kuwoneka kuti kukulitsa mtengo wa L kapena kukulitsa ma frequency osinthira kumatha kuchepetsa kusinthasintha komwe kulipo pa inductance.
Momwemonso, ubale pakati pa ma ripples otulutsa ndi ma capacitors otulutsa: VRIPPLE = IMAX / (CO × F). Zitha kuwoneka kuti kuwonjezeka kwa mtengo wa capacitor kumatha kuchepetsa ripple.
Njira mwachizolowezi ndi ntchito zotayidwa electrolytic capacitors kwa linanena bungwe capacitance kukwaniritsa cholinga chachikulu mphamvu. Komabe, ma electrolytic capacitors sakhala othandiza kwambiri popondereza phokoso lapamwamba, ndipo ESR ndi yayikulu, motero imalumikiza capacitor ya ceramic pafupi nayo kuti ipangitse kusowa kwa ma capacitors a aluminium electrolytic.
Panthawi imodzimodziyo, pamene magetsi akugwira ntchito, voliyumu ya VIN ya malo olowera sikusintha, koma kusintha kwamakono ndi kusintha. Panthawiyi, magetsi olowetsamo samapereka chitsime chamakono, nthawi zambiri pafupi ndi malo olowera panopa (kutenga mtundu wa buck monga chitsanzo, pafupi ndi Switch), ndikugwirizanitsa mphamvu kuti ipereke panopa.
Mutagwiritsa ntchito chotsutsa ichi, magetsi a Buck switch akuwonetsedwa pachithunzi pansipa:
Njira yomwe ili pamwambayi ndi yochepetsera ma ripples. Chifukwa cha malire a voliyumu, inductance sidzakhala yaikulu kwambiri; capacitor linanena bungwe kumawonjezera pa mlingo winawake, ndipo palibe zotsatira zoonekeratu kuchepetsa ripples; kuwonjezeka kwa kusintha kwafupipafupi kudzawonjezera kutaya kwa kusintha. Choncho pamene zofunikazo ndi zokhwima, njira imeneyi si yabwino kwambiri.
Pazinsinsi zosinthira magetsi, mutha kuloza mitundu yosiyanasiyana yosinthira makina opangira magetsi.
2. Awiri -level kusefa ndi kuwonjezera woyamba -level LC Zosefera
Zolepheretsa za fyuluta ya LC pa phokoso la phokoso ndizodziwikiratu. Malinga ndi ma ripple frequency oti achotsedwe, sankhani capacitor yoyenera inductor kuti mupange sefa yozungulira. Nthawi zambiri, imatha kuchepetsa ma ripples bwino. Pankhaniyi, muyenera kuganizira mfundo yachitsanzo cha voliyumu ya mayankho. (Monga zasonyezedwera pansipa)
Sampling point imasankhidwa pamaso pa LC fyuluta (PA), ndipo mphamvu yotulutsa idzachepetsedwa. Chifukwa inductance iliyonse imakhala ndi kukana kwa DC, pakakhala kutulutsa kwapano, pamakhala kutsika kwamagetsi mu inductance, zomwe zimapangitsa kuchepa kwamagetsi otulutsa magetsi. Ndipo kutsika kwamagetsi uku kumasintha ndi zomwe zimachokera.
Sampling point imasankhidwa pambuyo pa LC fyuluta (PB), kotero kuti voliyumu yotulutsa ndi voliyumu yomwe tikufuna. Komabe, inductance ndi capacitor zimayambitsidwa mkati mwa dongosolo lamagetsi, zomwe zingayambitse kusakhazikika kwadongosolo.
3. Pambuyo potulutsa mphamvu yosinthira magetsi, gwirizanitsani kusefa kwa LDO
Iyi ndiyo njira yabwino kwambiri yochepetsera phokoso ndi phokoso. Kutulutsa kwamagetsi kumakhala kosalekeza ndipo sikufunikira kusintha njira yoyambira, komanso ndiyotsika mtengo kwambiri komanso kugwiritsa ntchito mphamvu kwambiri.
LDO iliyonse ili ndi chizindikiro: chiŵerengero cha kuponderezana kwa phokoso. Ndi pafupipafupi-DB pamapindikira, monga momwe chithunzi pansipa ndi pamapindikira a LT3024 LT3024.
Pambuyo pa LDO, kusintha kosinthika kumakhala pansi pa 10mV. Chithunzi chotsatirachi ndikufanizira kwa ma ripples asanachitike komanso pambuyo pa LDO:
Poyerekeza ndi mapindikidwe a chithunzi pamwambapa ndi mawonekedwe ozungulira kumanzere, zitha kuwoneka kuti zoletsa za LDO ndizabwino kwambiri pakusuntha kwa mazana a KHz. Koma mkati mwa ma frequency apamwamba, zotsatira za LDO sizoyenera.
Chepetsani ma ripples. Ma waya a PCB amagetsi osinthira ndiwofunikiranso. Pakuti mkulu-pafupipafupi phokoso, chifukwa chachikulu pafupipafupi mkulu pafupipafupi, ngakhale positi-siteji kusefa ali ndi zotsatira zake, zotsatira si zoonekeratu. Pali maphunziro apadera pankhaniyi. Njira yosavuta ndiyo kukhala pa diode ndi capacitance C kapena RC, kapena kugwirizanitsa inductance mu mndandanda.
Chithunzi pamwambapa ndi gawo lofanana la diode yeniyeni. Pamene diode ndi mkulu -liwiro, magawo parasitic ayenera kuganiziridwa. Panthawi yobwezeretsanso diode, inductance yofanana ndi mphamvu yofananayo inakhala RC oscillator, yomwe imapanga oscillation yapamwamba kwambiri. Pofuna kupondereza oscillation apamwamba kwambiri, m'pofunika kulumikiza capacitance C kapena RC buffer network pamapeto onse a diode. Kukana nthawi zambiri kumakhala 10Ω-100 ω, ndipo mphamvu ndi 4.7PF-2.2NF.
Capacitance C kapena RC pa diode C kapena RC ikhoza kutsimikiziridwa ndi mayesero obwerezabwereza. Ngati sichinasankhidwe bwino, chimayambitsa kugwedezeka kwakukulu.
Nthawi yotumiza: Jul-08-2023
