The switching simba ripple haidzivisiki. Chinangwa chedu chikuru ndechekudzikisa ripple inobuda kusvika padanho rinogoneka. Iyo yakanyanya kukosha mhinduro yekuzadzisa chinangwa ichi ndeyekudzivirira chizvarwa chemaripples. Chekutanga uye chikonzero.
Nekuchinja kweiyo SWITCH, ikozvino mune inductance L zvakare inoshanduka ichikwira nekudzika pahukoshi hunoshanda hwekubuda ikozvino. Naizvozvo, pachave zvakare ne ripple iyo yakafanana frequency seSwitch pamagumo ekubuda. Kazhinji, ma ripples e riber anoreva izvi, izvo zvinoenderana nekugona kweiyo inobuda capacitor uye ESR. Kuwanda kweiyi ripple kwakafanana nekuchinja kwemagetsi, nehuwandu hwemakumi kusvika kumazana ekHz.
Mukuwedzera, Shandura kazhinji inoshandisa bipolar transistors kana MOSFETs. Hazvina mhosva kuti ndeipi, pachava nenguva yekusimuka nekudzikira painobatidzwa nekufa. Panguva ino, hapazove neruzha mudunhu rakafanana nenguva yekuwedzera seSwitch inokwira yekudzikira nguva, kana nguva shoma, uye kazhinji makumi eMHz. Saizvozvo, iyo diode D iri mukudzosera kumashure. Iyo yakaenzana dunhu ndiyo yakatevedzana yekupikisa capacitors uye inductors, izvo zvinokonzeresa resonance, uye ruzha frequency makumi emakumi eMHz. Idzi ruzha ruviri rwunowanzodaidzwa kunzi high-frequency noise, uye amplitude inowanzova yakakura kudarika ripple.
Kana iri AC / DC inoshandura, mukuwedzera kune ari pamusoro maviri ripples (ruzha), kune zvakare AC ruzha. Iyo frequency ndiyo frequency yekuisa AC magetsi ekupa, anenge 50-60Hz. Kune zvakare co-mode ruzha, nekuti simba mudziyo wevazhinji switching magetsi inoshandisa goko seradiator, iyo inoburitsa yakaenzana capacitance.
Kuyera kwekuchinja simba ripples
Basic zvinodiwa:
Kubatana neoscilloscope AC
20MHz bandwidth muganho
Bvisa tambo yepasi yeprobe
1.AC coupling ndeyekubvisa iyo superposition DC voltage uye kuwana chaiyo waveform.
2. Kuvhura 20MHz bandwidth muganhu ndeyekudzivirira kupindira kwepamusoro-frequency ruzha uye kudzivirira kukanganisa. Nekuti iyo amplitude ye-high-frequency composition yakakura, inofanirwa kubviswa kana kuyerwa.
3. Bvisa pasi clip ye oscilloscope probe, uye shandisa chiyero chekuyera pasi kuderedza kupindira. Madhipatimendi mazhinji haana maground rings. Asi funga nezvechinhu ichi pakusarudza kana inokodzera.
Imwe pfungwa ndeye kushandisa 50Ω terminal. Zvinoenderana neruzivo rweoscilloscope, iyo 50Ω module ndeyekubvisa iyo DC chikamu uye kuyera nemazvo chikamu che AC. Nekudaro, kune mashoma oscilloscopes ane akakosha probes. Muzviitiko zvakawanda, kushandiswa kweprobes kubva ku100kΩ kusvika ku10MΩ kunoshandiswa, izvo zvisingazivikanwi kwenguva pfupi.
Izvo zviri pamusoro ndizvo zvekutanga zvekuchengetedza pakuyera switching ripple. Kana iyo oscilloscope probe isina kuratidzwa zvakananga kune inobuda poindi, inofanirwa kuyerwa nemitsara yakamonyoroka kana 50Ω coaxial tambo.
Pakuyera ruzha rwepamusoro-frequency, bhendi rakazara reoscilloscope rinowanzoita mazana emamega kusvika kuGHz level. Zvimwe zvakafanana nezviri pamusoro apa. Zvichida makambani akasiyana ane nzira dzakasiyana dzekuedza. Mukuongorora kwekupedzisira, iwe unofanirwa kuziva mhinduro dzako dzebvunzo.
Nezve oscilloscope:
Imwe digital oscilloscope haigone kuyera ripples nemazvo nekuda kwekukanganisika uye kudzika kwekuchengetedza. Panguva ino, oscilloscope inofanira kuchinjwa. Dzimwe nguva kunyangwe iyo yekare simulation oscilloscope bandwidth ingori makumi e mega, kuita kuri nani pane yedhijitari oscilloscope.
Kudzivirirwa kwekuchinja simba ripples
Zvekuchinja ripples, theoretically uye zviripo. Pane nzira nhatu dzekudzikinura kana kudzikisira:
1. Wedzera inductance uye kubuda capacitor kusefa
Zvinoenderana neformula yemagetsi ekuchinja, saizi yekuchinja uye inductance kukosha kweiyo inductance inductance inove inversely proportional, uye inobuda ripples uye inobuda capacitor inopindirana. Naizvozvo, kuwedzera magetsi uye kubuda capacitors kunogona kuderedza ripples.
Mufananidzo uri pamusoro ndiwo wave wave wave mune inochinja magetsi inductor L. Ripple current △ ndinogona kuverengerwa kubva pane inotevera formula:
Zvinogona kuoneka kuti kuwedzera L kukosha kana kuwedzera switching frequency kunogona kuderedza kushanduka kwazvino mune inductance.
Saizvozvo, hukama pakati pezvinobuda ripples uye zvinobuda capacitors: VRIPPLE = IMAX / (CO × F). Zvinogona kuoneka kuti kuwedzera yakabuda capacitor kukosha kunogona kuderedza ripple.
Iyo yakajairika nzira ndeye kushandisa aluminium electrolytic capacitors yekuburitsa capacitance kuzadzisa chinangwa chehukuru hukuru. Zvisinei, electrolytic capacitors hainyanyi kushanda mukudzvinyirira high-frequency noise, uye ESR yakakura, saka ichabatanidza ceramic capacitor pedyo nayo kuti iite kushayikwa kwealuminium electrolytic capacitors.
Panguva imwecheteyo, kana simba rekushandisa riri kushanda, vheji yeVIN yemagetsi ekupinza haina kuchinjwa, asi ikozvino inoshanduka nekuchinja. Panguva ino, magetsi ekupinza haapi tsime razvino, kazhinji padyo neazvino yekuisa terminal (kutora iyo buck mhando semuenzaniso, iri pedyo Shandura), uye inobatanidza iyo capacitance yekupa ikozvino.
Mushure mekushandisa iyi countermeasure, iyo Buck switch yemagetsi inoratidzwa mumufananidzo uri pazasi:
Nzira iri pamusoro inongogumira pakuderedza ripples. Nemhaka yehuwandu hwehuwandu, inductance haizove yakakura kwazvo; iyo inobuda capacitor inowedzera kune imwe dhigirii, uye hapana pachena mhedzisiro yekudzikisa ripples; kuwedzera kwekuchinja kwekuchinja kuchawedzera kurasikirwa kwekuchinja. Saka kana zvinodiwa zvakasimba, nzira iyi haina kunyatsonaka.
Kune iyo misimboti yekuchinjisa magetsi ekupa, unogona kutarisa kune akasiyana marudzi ekuchinja magetsi ekugadzira manyorerwo.
2. Two-level kusefa ndiko kuwedzera first-level LC filters
Iyo inhibitory mhedzisiro yeLC sefa pane ruzha ripple iri pachena. Zvinoenderana neiyo ripple frequency inobviswa, sarudza yakakodzera inductor capacitor kuti igadzire sefa redunhu. Kazhinji, inogona kuderedza ripples zvakanaka. Muchiitiko ichi, iwe unofanirwa kufunga nezve sampling poindi yemhinduro voltage. (Sezvinoratidzwa pasi apa)
Iyo sampling poindi inosarudzwa pamberi peLC sefa (PA), uye inobuda voltage ichaderedzwa. Nekuti chero inductance ine DC inopokana, kana paine ikozvino yakabuda, pachave nekudonha kwevoltage mune inductance, zvichikonzera kudzikira kweiyo inobuda voltage yemagetsi. Uye iyi voltage inodonha inoshanduka neinobuda ikozvino.
Iyo sampling poindi inosarudzwa mushure meLC sefa (PB), kuitira kuti inobuda voltage ndiyo voltage yatinoda. Nekudaro, inductance uye capacitor inounzwa mukati mesimba system, izvo zvinogona kukonzera kusagadzikana kwehurongwa.
3. Mushure mekubuda kwesimba rekushandura, batanidza LDO kusefa
Iyi ndiyo nzira inonyanya kushanda yekudzikisa ripples uye ruzha. Iyo inobuda voltage inongogara uye haidi kushandura iyo yekutanga mhinduro sisitimu, asi zvakare ndiyo inonyanya kudhura-inoshanda uye yakanyanya kushandisa simba.
Chero LDO ine chiratidzo: ruzha kudzvinyirira ratio. Iyo frequency-DB curve, sezvakaratidzwa mumufananidzo pazasi ndiyo curve yeLT3024 LT3024.
Mushure meLDO, iyo switching ripple kazhinji iri pasi pe10mV. Iyi inotevera nhamba ndeyekufananidzwa kwema ripples pamberi uye mushure meLDO:
Kuenzaniswa necurve yemufananidzo uri pamusoro uye waveform kuruboshwe, zvinogona kuoneka kuti inhibitory mhedzisiro yeLDO yakanaka kwazvo pakuchinja kwemazana eKHz. Asi mukati mehupamhi hwepamusoro, mhedzisiro yeLDO haina kunaka.
Deredza ripples. Iyo PCB wiring ye switching power supply yakakoshawo. Nokuda kwe-high-frequency ruzha, nekuda kwehuwandu hwehuwandu hwehuwandu hwepamusoro, kunyange zvazvo post-stage filtering ine imwe mhedzisiro, mhedzisiro yacho haisi pachena. Pane zvidzidzo zvakakosha panyaya iyi. Nzira iri nyore ndeyekuva pane diode uye capacitance C kana RC, kana kubatanidza inductance munhevedzano.
Mufananidzo uri pamusoro apa idunhu rakaenzana reiyo diode chaiyo. Kana iyo diode yakakwira-kumhanya, parasitic parameters inofanirwa kutariswa. Munguva yekudzoreredzwa kweiyo diode, iyo yakaenzana inductance uye yakaenzana capacitance yakava RC oscillator, ichigadzira yakakwira-frequency oscillation. Kuti udzivise iyi yakakwirira-frequency oscillation, zvinodikanwa kubatanidza capacitance C kana RC buffer network kumativi ose e diode. Kuramba kunowanzo 10Ω-100 ω, uye capacitance ndeye 4.7PF-2.2NF.
Iyo capacitance C kana RC pane diode C kana RC inogona kutsanangurwa nekudzokororwa bvunzo. Kana iyo isina kusarudzwa nemazvo, inokonzeresa yakanyanya oscillation.
Nguva yekutumira: Jul-08-2023
