Iriple yamandla okutshintsha ayinakuphepheka. Eyona njongo yethu kukunciphisa i-ripple yemveliso ukuya kwinqanaba elinyamezelekayo. Esona sisombululo sisisiseko sokufezekisa le njongo kukuphepha ukuveliswa kwama-ripples. Okokuqala kunye nonobangela.
Ngokutshintsha kwe-SWITCH, i-current inductance L iphinda ihlambuluke phezulu kwaye ihle kwixabiso elisebenzayo lemveliso yangoku. Ke ngoko, kuya kubakho i-ripple eyi-frequency efanayo neTshintsho ekupheleni kwesiphumo. Ngokuqhelekileyo, i-ripples ye-riber ibhekisela kule nto, ehambelana nomthamo we-capacitor yokuphuma kunye ne-ESR. I-frequency yale ripple iyafana nokunikezelwa kwamandla okutshintsha, kunye noluhlu lwamashumi ukuya kumakhulu e-kHz.
Ukongeza, uTshintsho ngokuqhelekileyo lusebenzisa i-bipolar transistors okanye ii-MOSFETs. Nokuba yeyiphi na, kuya kubakho ukunyuka kunye nokuncipha kwexesha xa ivuliwe kwaye ifile. Ngeli xesha, akusayi kubakho ngxolo kwisekethe efana nexesha lokunyuka njengoko iSwitch inyuka ixesha lokunciphisa, okanye amaxesha ambalwa, kwaye ngokubanzi amashumi e-MHz. Ngokufanayo, i-diode D ibuyele umva. Isekethe elinganayo luluhlu lwe-resonance capacitors kunye ne-inductors, oluya kubangela i-resonance, kwaye i-frequency yengxolo ngamashumi e-MHz. Ezi ngxolo zimbini zibizwa ngokuba yingxolo ephezulu, kwaye i-amplitude idla ngokuba nkulu kuneripple.
Ukuba sisiguquli se-AC / DC, ukongeza kwezi zimbini zingentla (ingxolo), kukho ingxolo ye-AC. I-frequency yi-frequency yegalelo lombane we-AC, malunga ne-50-60Hz. Kukho ingxolo ye-co-mode, kuba isixhobo samandla samandla amaninzi okutshintsha umbane sisebenzisa igobolondo njenge-radiator, evelisa i-capacitance elinganayo.
Umlinganiselo wokutshintsha ama-ripples amandla
Iimfuno eziphambili:
Ukudibanisa ne-oscilloscope AC
20MHz umda womda wobubanzi
Khupha ucingo olusezantsi lweprobe
Ukudityaniswa kwe-1.AC kukususa amandla ombane aphezulu e-DC kwaye ufumane i-waveform echanekileyo.
2. Ukuvula umda we-bandwidth ye-20MHz kukuthintela ukuphazamiseka kwengxolo ephezulu-frequency kunye nokuthintela impazamo. Ngenxa yokuba i-amplitude ye-high-frequency composition inkulu, kufuneka isuswe xa ilinganiswa.
3. Khupha ikliphu yomhlaba yeprobe ye-oscilloscope, kwaye usebenzise umlinganiselo wokulinganisa umhlaba ukunciphisa ukuphazamiseka. Amasebe amaninzi awanazo izangqa zomhlaba. Kodwa qwalasela lo mba xa ugweba enoba uyafaneleka kusini na.
Enye inqaku kukusebenzisa i-terminal ye-50Ω. Ngokolwazi lwe-oscilloscope, imodyuli ye-50Ω kukususa icandelo le-DC kunye nokulinganisa ngokuchanekileyo icandelo le-AC. Nangona kunjalo, zimbalwa ii-oscilloscopes ezineprobe ezikhethekileyo ezinjalo. Kwiimeko ezininzi, ukusetyenziswa kweprobes ukusuka kwi-100kΩ ukuya kwi-10MΩ kuyasetyenziswa, nto leyo engacacanga okwethutyana.
Oku kungentla kumanyathelo okhuseleko asisiseko xa ulinganisa i-ripple yokutshintsha. Ukuba i-oscilloscope probe ayibonakali ngokuthe ngqo kwindawo yokuphuma, kufuneka ilinganiswe ngemigca ephothiweyo okanye i-50Ω coaxial cables.
Xa ulinganisa ingxolo ye-high-frequency, ibhendi epheleleyo ye-oscilloscope ngokuqhelekileyo ngamakhulu e-mega ukuya kwinqanaba le-GHz. Ezinye ziyafana nezi zingasentla. Mhlawumbi iinkampani ezahlukeneyo zineendlela ezahlukeneyo zovavanyo. Kuhlalutyo lokugqibela, kufuneka uzazi iziphumo zovavanyo lwakho.
Malunga ne-oscilloscope:
Enye i-oscilloscope yedijithali ayikwazi ukulinganisa ama-ripples ngokuchanekileyo ngenxa yokuphazamiseka kunye nobunzulu bokugcina. Ngeli xesha, i-oscilloscope kufuneka itshintshwe. Ngamanye amaxesha nangona i-bandwidth ye-oscilloscope endala ingamashumi kuphela eemega, ukusebenza kungcono kune-oscilloscope yedijithali.
Ukuthintelwa kokutshintsha amaza amandla
Ukutshintsha ama-ripples, ithiyori kwaye ikhona ngokwenene. Kukho iindlela ezintathu zokuyicinezela okanye ukuyinciphisa:
1. Ukwandisa i-inductance kunye ne-output capacitor filtering
Ngokwefomula yonikezelo lwamandla okutshintsha, ubungakanani obuguquguqukayo bangoku kunye nexabiso le-inductance ye-inductance inductance iba ngokungafaniyo, kwaye i-ripples ye-output ripples kunye ne-capacitors ye-output i-proportional. Ke ngoko, ukonyusa i-capacitors yombane kunye nemveliso kunokunciphisa ama-ripples.
Lo mfanekiso ungasentla luhlobo lwamaza lwangoku kwi-inductor yonikezelo lwamandla okutshintshayo L. Iripple yangoku △ inokubalwa kule fomula ilandelayo:
Ingabonwa ukuba ukunyuka kwexabiso le-L okanye ukwandisa i-frequency switching frequency kunokunciphisa ukuguquguquka kwangoku kwi-inductance.
Ngokufanayo, ubudlelwane phakathi kwe-ripples output kunye ne-capacitors output: VRIPPLE = IMAX / (CO × F). Ingabonwa ukuba ukonyusa ixabiso le-capacitor yemveliso kunokunciphisa i-ripple.
Indlela eqhelekileyo kukusebenzisa i-aluminium electrolytic capacitors kwi-capacitance yemveliso ukufezekisa injongo yomthamo omkhulu. Nangona kunjalo, i-electrolytic capacitors ayisebenzi kakhulu ekucinezeleni ingxolo ye-high-frequency, kwaye i-ESR inkulu, ngoko iya kudibanisa i-ceramic capacitor ecaleni kwayo ukwenza ukungabikho kwe-aluminium electrolytic capacitors.
Ngexesha elifanayo, xa umbane usebenza, i-VIN ye-voltage ye-terminal yokufaka ayitshintshi, kodwa utshintsho lwangoku kunye nokutshintsha. Ngeli xesha, unikezelo lwamandla okufakwayo aluboneleli ngokufanelekileyo ngoku, ngokuqhelekileyo kufuphi ne-terminal yegalelo langoku (ukuthatha uhlobo lwe-buck njengomzekelo, kufuphi noTshintsho), kwaye idibanisa i-capacitance yokubonelela ngoku.
Emva kokusebenzisa lo mlinganiso, umbane wokutshintsha iBuck ubonisiwe kulo mfanekiso ungezantsi:
Le ndlela ingentla ilinganiselwe ekunciphiseni ama-ripples. Ngenxa yomthamo wevolumu, i-inductance ayiyi kuba nkulu kakhulu; i-capacitor ephumayo iyanda kwinqanaba elithile, kwaye akukho siphumo esicacileyo ekunciphiseni ama-ripples; ukwanda kokutshintsha kokutshintsha kuya kwandisa ilahleko yokutshintsha. Ngoko xa iimfuno zingqongqo, le ndlela ayilunganga kakhulu.
Kwimigaqo yokutshintsha unikezelo lwamandla, ungabhekisa kwiindidi ezahlukeneyo zokutshintsha iincwadana zoyilo lwamandla.
2. Ukucoca inqanaba ezimbini kukongeza izihluzo ze-LC ezikumgangatho wokuqala
Isiphumo sokuthintela isihluzo se-LC kwi-ripple yengxolo ibonakala ngokucacileyo. Ngokwe-ripple frequency kufuneka isuswe, khetha i-inductor capacitor efanelekileyo ukwenza i-filter circuit. Ngokuqhelekileyo, inokunciphisa ama-ripples kakuhle. Kule meko, kufuneka uqwalasele indawo yesampula yevoltage yengxelo. (Njengoko kubonisiwe ngezantsi)
Indawo yesampula ikhethwe phambi kwe-LC filter (PA), kwaye i-voltage ephumayo iya kuncitshiswa. Ngenxa yokuba nayiphi na i-inductance inokumelana ne-DC, xa kukho imveliso yangoku, kuya kubakho ukuhla kwe-voltage kwi-inductance, okubangelwa ukuhla kwe-voltage ephumayo yokunikezelwa kwamandla. Kwaye oku kuhla kwamandla ombane kuyatshintsha kunye nemveliso yangoku.
Indawo yesampula ikhethwe emva kwe-LC filter (PB), ukwenzela ukuba i-voltage ephumayo ibe yi-voltage esiyifunayo. Nangona kunjalo, i-inductance kunye ne-capacitor ifakwe ngaphakathi kwenkqubo yamandla, enokubangela ukungazinzi kwenkqubo.
3. Emva kokuphuma kombane wokutshintsha, qhagamshela i-LDO yokucoca
Le yeyona ndlela isebenzayo yokunciphisa ama-ripples kunye nengxolo. I-voltage ye-output ihleli kwaye ayifuni ukutshintsha inkqubo yempendulo yokuqala, kodwa ikwayeyona ndleko-esebenzayo kunye nosetyenziso lwamandla aphezulu.
Nayiphi na i-LDO inesalathisi: umlinganiselo wokunciphisa ingxolo. Yi-frequency-DB curve, njengoko kubonisiwe kumzobo ongezantsi yigophe le-LT3024 LT3024.
Emva kwe-LDO, i-ripple yokutshintsha ngokubanzi ingaphantsi kwe-10mV. Lo mzobo ulandelayo luthelekiso lweeripples phambi nasemva kweLDO:
Xa kuthelekiswa negophe lomzobo ongentla kunye ne-waveform ekhohlo, kunokubonwa ukuba i-inhibitory effect ye-LDO ilungile kakhulu kwii-ripples zokutshintsha zamakhulu e-KHz. Kodwa ngaphakathi koluhlu oluphezulu lwefrikhwensi, isiphumo se-LDO asilunganga kangako.
Ukunciphisa ama-ripples. Iingcingo zePCB zonikezelo lwamandla okutshintsha nazo zibalulekile. Kwingxolo ephezulu-frequency, ngenxa yokuphindaphinda okukhulu kwe-frequency ephezulu, nangona i-post-stage filtering inefuthe elithile, umphumo awubonakali. Kukho izifundo ezikhethekileyo kulo mba. Indlela elula kukuba ibe kwi-diode kunye ne-capacitance C okanye i-RC, okanye udibanise i-inductance kwi-series.
Lo mzobo ungentla yisekethe elinganayo ye-diode yangempela. Xa i-diode iphezulu-isantya, iiparamitha zeparasitic kufuneka ziqwalaselwe. Ngethuba lokubuyisela umva kwe-diode, i-inductance elinganayo kunye ne-capacitance elinganayo yaba yi-RC oscillator, evelisa i-oscillation ephezulu-frequency. Ukuze ucinezele le-oscillation ephezulu-frequency, kuyimfuneko ukudibanisa i-capacitance C okanye i-RC buffer network kuzo zombini iziphelo zediode. Ukuchasana ngokuqhelekileyo yi-10Ω-100 ω, kwaye i-capacitance yi-4.7PF-2.2NF.
I-capacitance C okanye i-RC kwi-diode C okanye i-RC inokumiselwa ngovavanyo oluphindaphindiweyo. Ukuba ayikhethwanga ngokufanelekileyo, iya kubangela i-oscillation enzima ngakumbi.
Ixesha lokuposa: Jul-08-2023
