I-switching power ripple ayinakugwenywa. Inhloso yethu enkulu ukwehlisa i-ripple yokuphumayo ibe sezingeni elibekezeleleka. Isixazululo esibaluleke kakhulu sokufeza le njongo ukugwema ukukhiqizwa kwama-ripples. Okokuqala Futhi imbangela.
Ngokushintsha kwe-SWITCH, okwamanje ku-inductance L futhi iguquguquka iye phezulu naphansi ngenani elivumelekile lokuphumayo kwamanje. Ngakho-ke, kuzophinde kube khona i-ripple eyimvamisa efanayo ne-Shintsha ekugcineni kokuphumayo. Ngokuvamile, ama-ripples we-riber abhekisela kulokhu, okuhlobene nomthamo we-capacitor okukhiphayo kanye ne-ESR. Imvamisa yale ripple iyafana nokushintsha kwamandla kagesi, ngebanga lamashumi kuya kumakhulu e-kHz.
Ngaphezu kwalokho, i-Switch ngokuvamile isebenzisa ama-bipolar transistors noma ama-MOSFET. Kungakhathaliseki ukuthi iyiphi, kuyoba khona ukukhuphuka nokunciphisa isikhathi lapho ivuliwe futhi ifile. Ngalesi sikhathi, ngeke kube khona umsindo kusekethe ofana nesikhathi sokwenyuka njengesikhathi sokunciphisa Ukushintsha okukhuphukayo, noma izikhathi ezimbalwa, futhi ngokuvamile kuba amashumi ama-MHz. Ngokufanayo, i-diode D is in reverse recovery. Umjikelezo olinganayo uchungechunge lwama-capacitor okumelana nama-inductors, okuzodala i-resonance, futhi imvamisa yomsindo amashumi e-MHz. Le misindo emibili ngokuvamile ibizwa ngokuthi i-high-frequency noise, futhi i-amplitude ivame ukuba nkulu kakhulu kunomsindo.
Uma kuyi-converter ye-AC / DC, ngaphezu kwama-ripples amabili angenhla (umsindo), kuphinde kube nomsindo we-AC. Imvamisa imvamisa yokufaka amandla kagesi we-AC, cishe ama-50-60Hz. Kukhona futhi umsindo we-co-mode, ngoba idivayisi yamandla yamandla amaningi okushintshanisa amandla isebenzisa igobolondo njenge-radiator, ekhiqiza amandla alinganayo.
Isilinganiso sokushintshwa kwama-ripples wamandla
Izidingo eziyisisekelo:
Ihlanganiswe ne-oscilloscope AC
20MHz umkhawulo womkhawulokudonsa
Khipha intambo yaphansi ye-probe
Ukuhlanganiswa kwe-1.AC ukususa amandla kagesi e-Superposition DC futhi uthole i-waveform enembile.
2. Ukuvula umkhawulo womkhawulokudonsa ongu-20MHz ukuvimbela ukuphazamiseka komsindo we-high-frequency nokuvimbela iphutha. Ngenxa yokuthi i-amplitude yokwakheka kwe-high-frequency inkulu, kufanele isuswe lapho ikalwa.
3. Khipha isiqeshana saphansi se-oscilloscope probe, bese usebenzisa isilinganiso sokulinganisa umhlabathi ukuze unciphise ukuphazamiseka. Iminyango eminingi ayinazo izindandatho. Kodwa cabangela lesi sici lapho wahlulela ukuthi liyafaneleka yini.
Elinye iphuzu ukusebenzisa itheminali engu-50Ω. Ngokolwazi lwe-oscilloscope, imojula engu-50Ω iwukukhipha ingxenye ye-DC futhi ikalwe ngokunembile ingxenye ye-AC. Kodwa-ke, kukhona ama-oscilloscope ambalwa anama-probe akhethekile. Ezimweni eziningi, ukusetshenziswa kwama-probe kusuka ku-100kΩ kuya ku-10MΩ kusetshenziswa, okungacacile okwesikhashana.
Okungenhla yizinyathelo zokuphepha eziyisisekelo lapho ukala i-ripple yokushintsha. Uma i-oscilloscope probe ingavezwanga ngokuqondile endaweni yokuphumayo, kufanele ikalwe ngemigqa esontiwe noma izintambo ezingama-coaxial ezingu-50Ω.
Uma ukala umsindo we-high-frequency, ibhendi egcwele ye-oscilloscope ngokuvamile iba ngamakhulu ama-mega kuya kuzinga le-GHz. Ezinye ziyefana nalokhu okungenhla. Mhlawumbe izinkampani ezahlukene zinezindlela ezahlukene zokuhlola. Ekuhlaziyeni kokugcina, kufanele wazi imiphumela yakho yokuhlolwa.
Mayelana ne-oscilloscope:
Enye i-oscilloscope yedijithali ayikwazi ukukala ama-ripples ngendlela efanele ngenxa yokuphazamiseka nokujula kwesitoreji. Ngalesi sikhathi, i-oscilloscope kufanele ishintshwe. Kwesinye isikhathi nakuba umkhawulokudonsa omdala wokulingisa we-oscilloscope ungamashumi kuphela ama-mega, ukusebenza kungcono kune-oscilloscope yedijithali.
Ukuvinjwa kwama-ripples wamandla okushintsha
Ngokushintsha ama-ripples, ngokwethiyori futhi akhona empeleni. Kunezindlela ezintathu zokuyicindezela noma ukuyinciphisa:
1. Khulisa ukuhlunga kwe-inductance kanye nokukhishwa kwe-capacitor
Ngokwefomula yokushintsha kwamandla kagesi, usayizi wamanje wokuguquguquka kanye nevelu ye-inductance ye-inductive inductance iba ngokulingana ngokuphambene, futhi ama-ripples okukhiphayo nama-capacitor okukhiphayo ahambisana ngokuphambene. Ngakho-ke, ukwandisa ama-capacitor kagesi kanye nokuphumayo kunganciphisa ama-ripples.
Isithombe esingenhla siyisimo segagasi samanje ekushintsheni kwesifakeli samandla sikagesi L. I-ripple current △ ngingabalwa kusukela kufomula elandelayo:
Kungabonakala ukuthi ukukhulisa inani le-L noma ukukhulisa imvamisa yokushintsha kunganciphisa ukuguquguquka kwamanje ku-inductance.
Ngokufanayo, ubudlelwano phakathi kwama-ripples okukhiphayo nama-capacitor okukhiphayo: VRIPPLE = IMAX/(CO × F). Kungabonakala ukuthi ukukhulisa inani le-capacitor okukhiphayo kunganciphisa i-ripple.
Indlela evamile ukusebenzisa i-aluminium electrolytic capacitor ukuze uthole amandla okukhipha ukufeza inhloso yomthamo omkhulu. Kodwa-ke, ama-electrolytic capacitor awasebenzi kahle ekucindezeleni umsindo we-high-frequency, futhi i-ESR inkulu kakhulu, ngakho izoxhuma i-ceramic capacitor eduze kwayo ukuze yenze ukuntuleka kwama-aluminium electrolytic capacitor.
Ngesikhathi esifanayo, lapho ukunikezwa kwamandla kusebenza, i-voltage VIN ye-terminal yokufaka ayishintshi, kodwa izinguquko zamanje ngokushintsha. Ngalesi sikhathi, ukunikezwa kwamandla okokufaka akuhlinzeki ngomthombo wamanje, ngokuvamile eduze kwetheminali yamanje yokokufaka (ukuthatha uhlobo lwemali njengesibonelo, kuseduze no-Switch), futhi ixhuma amandla ukuze kuhlinzekwe okwamanje.
Ngemuva kokusebenzisa lesi sinyathelo esiphikisayo, ugesi we-Buck switch uboniswa esithombeni esingezansi:
Indlela engenhla ilinganiselwe ekwehliseni ama-ripples. Ngenxa yomkhawulo wevolumu, i-inductance ngeke ibe nkulu kakhulu; i-capacitor ephumayo ikhuphuka ngezinga elithile, futhi akukho mphumela osobala ekunciphiseni ama-ripples; ukwanda kwemvamisa yokushintsha kuzokhulisa ukulahleka kokushintsha. Ngakho lapho izidingo ziqinile, le ndlela ayinhle kakhulu.
Ngezimiso zokushintsha ukunikezwa kwamandla, ungabhekisela ezinhlotsheni ezihlukahlukene zokushintshwa kwamabhukwana wokuklama amandla.
2. Ukuhlunga kweleveli emibili wukwengeza izihlungi ze-LC zezinga lokuqala
Umphumela ovimbelayo wesihlungi se-LC ku-ripple yomsindo usobala ngokuqhathaniswa. Ngokuvumelana nemvamisa ye-ripple okufanele isuswe, khetha i-inductor capacitor efanelekile ukuze wakhe umjikelezo wesihlungi. Ngokuvamile, kunganciphisa ama-ripples kahle. Kulokhu, udinga ukucabangela iphuzu lesampula le-voltage yempendulo. (Njengoba kukhonjisiwe ngezansi)
Iphuzu lesampula likhethwa ngaphambi kwesihlungi se-LC (PA), futhi i-voltage ephumayo izoncishiswa. Ngenxa yokuthi noma iyiphi i-inductance inokumelana ne-DC, uma kukhona okukhiphayo kwamanje, kuzoba nokwehla kwe-voltage ku-inductance, okuholela ekwehleni kwe-voltage yokuphuma kwamandla kagesi. Futhi lokhu kwehla kwe-voltage kuyashintsha ngokuphuma kwamanje.
Iphuzu lesampula likhethwa ngemva kwesihlungi se-LC (PB), ukuze i-voltage ephumayo ibe yi-voltage esiyifunayo. Kodwa-ke, i-inductance kanye ne-capacitor yethulwa ngaphakathi kwesistimu yamandla, engase ibangele ukungazinzi kwesistimu.
3. Ngemva kokukhishwa kwamandla okushintsha, xhuma ukuhlunga kwe-LDO
Lena indlela ephumelela kakhulu yokunciphisa ama-ripples nomsindo. I-voltage ephumayo ayishintshile futhi ayidingi ukushintsha isistimu yempendulo yokuqala, kodwa futhi iyona engabizi kakhulu futhi isebenzisa amandla aphezulu kakhulu.
Noma iyiphi i-LDO inenkomba: isilinganiso sokucindezela umsindo. Ijika le-frequency-DB, njengoba kukhonjisiwe emfanekisweni ongezansi ijika le-LT3024 LT3024.
Ngemuva kwe-LDO, i-ripple yokushintsha ngokuvamile ingaphansi kwe-10mV. Isibalo esilandelayo siwukuqhathaniswa kwama-ripples ngaphambi nangemuva kwe-LDO:
Uma kuqhathaniswa nejika lesibalo esingenhla kanye ne-waveform kwesokunxele, kungabonakala ukuthi umphumela wokuvimbela we-LDO muhle kakhulu ekushintsheni kwama-ripples amakhulu we-KHz. Kepha phakathi kwebanga lemvamisa ephezulu, umphumela we-LDO awulungile kangako.
Yehlisa ama-ripples. Izintambo ze-PCB zokunikezwa kwamandla okushintshwa nazo zibalulekile. Ngomsindo we-high-frequency, ngenxa yemvamisa enkulu yemvamisa ephezulu, nakuba ukuhlunga kwe-post-stage kunomphumela othile, umphumela awubonakali. Kunezifundo ezikhethekile mayelana nalokhu. Indlela elula iwukuba ku-diode kanye ne-capacitance C noma i-RC, noma uxhume i-inductance ochungechungeni.
Isibalo esingenhla siyisifunda esilinganayo se-diode yangempela. Lapho i-diode inesivinini esikhulu, imingcele ye-parasitic kufanele icatshangelwe. Ngesikhathi sokuhlehla kwe-diode, i-inductance elinganayo namandla alinganayo abe yi-RC oscillator, ekhiqiza i-high-frequency oscillation. Ukuze ucindezele lokhu kuzungeza kwe-high-frequency oscillation, kuyadingeka ukuxhuma i-capacitance C noma inethiwekhi ye-RC buffer kuzo zombili iziphetho ze-diode. Ukumelana ngokuvamile kungu-10Ω-100 ω, futhi amandla ngu-4.7PF-2.2NF.
I-capacitance C noma i-RC ku-diode C noma i-RC inganqunywa ngokuhlolwa okuphindaphindiwe. Uma ingakhethiwe kahle, izodala ukuzulazula okunamandla kakhulu.
Isikhathi sokuthumela: Jul-08-2023
