In high-frequency PCB ibhodi, uhlobo olubaluleke kakhulu lokuphazanyiswa umsindo wokuphakelwa kwamandla. Ngokuhlaziya ngokuhlelekile izici nezimbangela zomsindo wamandla kumabhodi e-PCB anemvamisa ephezulu, umbhali ubeka phambili izixazululo ezisebenza kahle kakhulu nezilula ngokuhambisana nezinhlelo zokusebenza zobunjiniyela.

Analysis of power supply noise

Umsindo wokuphakelwa kwamandla ubhekisela emsindweni okhiqizwa ugesi ngokwawo noma obangelwa ukuphazamiseka. Ukugxambukela kuboniswa ezicini ezilandelayo:

1) Umsindo osabalalisiwe obangelwa ukuthintana okungokwemvelo kokunikezwa kwamandla ngokwawo. Kumasekhethi anemvamisa ephezulu, umsindo wokuphakelwa kwamandla unomthelela omkhulu kumasiginali wamafrikhwensi aphezulu. Ngakho-ke, ukunikezwa kwamandla omsindo ophansi kuyadingeka kuqala. Inhlabathi ehlanzekile ibaluleke njengomthombo wamandla ohlanzekile. Isici samandla siboniswa kuFig. 1.

I-wave wave yamandla

Njengoba kungabonwa kuMfanekiso 1, ukunikezwa kwamandla ngaphansi kwezimo ezikahle akunakho ukuphazamiseka, ngakho-ke akukho msindo. Kodwa-ke, ukunikezwa kwamandla kwangempela kune-impedance ethile, futhi i-impedance isatshalaliswa kuwo wonke amandla kagesi, ngakho-ke, umsindo uzophinde ubekwe phezu kwamandla kagesi. Ngakho-ke, ukuvinjelwa kokunikezwa kwamandla kufanele kuncishiswe ngangokunokwenzeka, futhi kungcono ukuba nesendlalelo samandla esizinikezele kanye nongqimba lomhlabathi. Ekwakhiweni kwesekethe ye-high-frequency, ngokuvamile kungcono ukuklama ukunikezwa kwamandla ngendlela yesendlalelo kunesimo sebhasi, ukuze i-loop ihlale ilandela indlela nge-impedance encane. Ngaphezu kwalokho, ibhodi lamandla kufanele futhi linikeze iluphu yesiginali yawo wonke amasiginali akhiqiziwe futhi atholiwe ku-PCB, ukuze iluphu yesiginali incishiswe, ngaleyo ndlela kuncishiswe umsindo.

2) Ukuphazamiseka kwenkambu yemodi evamile. Kubhekisela emsindweni ophakathi kwamandla kagesi nomhlabathi. Ukuphazamisa okubangelwa i-voltage yemodi evamile okubangelwa iluphu eyakhiwe isekethe ephazamisekile kanye nendawo evamile yereferensi yendawo ethile kagesi. Inani layo lincike endaweni kagesi ehlobene kanye nensimu kazibuthe. Amandla ancike emandleni. Njengoba kuboniswe kuMfanekiso 2.

Common mode interference

Kulesi siteshi, ukwehla kwe-Ic kuzodala i-voltage yemodi evamile ku-loop yamanje yochungechunge, okuzothinta ingxenye eyamukelayo. Uma inkambu kazibuthe ibusa, inani levolthemu yemodi evamile ekhiqizwa kuluphu yaphansi yochungechunge ithi:

I-voltage yemodi evamile

Kufomula (1), ΔB iwushintsho ku-magnetic flux density, Wb/m2; S indawo, m2.

Uma kuyinkambu ye-electromagnetic, lapho inani layo lensimu kagesi laziwa, i-voltage yayo eyenziwe

I-voltage ye-inductive

Isibalo (2) ngokuvamile sisebenza ku-L=150/F noma ngaphansi, lapho u-F eyimvamisa yamagagasi kagesi ku-MHz.

Okuhlangenwe nakho kombhali yilokhu: Uma lo mkhawulo weqiwe, ukubalwa kwe-voltage ephezulu eyenziwe lula kungenziwa lula ukuze:

I-voltage engenisiwe ephezulu

3) Differential mode field interference. Refers to the interference between the power supply and the input and output power lines. In the actual PCB design, the author found that its proportion in the power supply noise is very small, so it is not necessary to discuss it here.

4) Ukuphazanyiswa kwe-inter-line. Isho ukuphazamiseka phakathi kwezintambo zikagesi. Uma kukhona i-mutual capacitance C kanye ne-mutual inductance M1-2 phakathi kwamasekhethi amabili ahlukene afanayo, uma kukhona i-voltage VC kanye ne-IC yamanje kusekethe yomthombo wokuphazanyiswa, isekethe ephazamisekile izovela:

A. I-voltage ehambisana ne-capacitive impedance ingu

I-voltage ehlanganiswe ne-capacitive impedance

Kufomula (4), i-RV inani elihambisanayo lokumelana nokuphela kanye nokumelana nesiphetho sesekethe ephazamisekile.

B. Ukumelana nochungechunge ngokusebenzisa ukuhlanganisa inductive

Ukumelana kochungechunge ngokuhlanganisa i-inductive

Uma kunomsindo wemodi evamile emthonjeni wokuphazamiseka, ukuphazamiseka komugqa nomugqa ngokuvamile kuthatha uhlobo lwemodi evamile kanye nemodi yokuhlukanisa.

5) Ukuhlanganisa intambo kagesi. Kubhekisela kwinto yokuthi ngemva kokuthi intambo yamandla e-AC noma ye-DC ingaphansi kokuphazanyiswa nguzibuthe, intambo yamandla idlulisela ukuphazamiseka kwamanye amadivaysi. Lokhu ukuphazamiseka okungaqondile komsindo wokunikezwa kwamandla kusekethi yamafrikhwensi aphezulu. Kumele kuqashelwe ukuthi umsindo wokuphakelwa kukagesi awuzivezi ngokwawo, kodwa futhi ungase ube nomsindo obangelwa ukuphazamiseka kwangaphandle, bese uphakamisa lo msindo ngomsindo owenziwe ngokwawo (i-radiation noma conduction) ukuze uphazamise amanye amasekhethi. noma amadivaysi.

Izinyathelo zokuqeda ukuphazanyiswa komsindo wokunikezwa kwamandla

Ngokubuka ukubonakaliswa okuhlukene kanye nezimbangela zokuphazamiseka komsindo wokuhlinzekwa kwamandla okuhlaziywe ngenhla, izimo okwenzeka ngaphansi kwazo zingacekelwa phansi ngendlela eqondiwe, futhi ukuphazamiseka komsindo wokuphakelwa kwamandla kungacindezelwa ngempumelelo. Izixazululo zimi kanje: 1) Naka izimbobo ebhodini. Imbobo edlulayo idinga ukuvuleka kwesendlalelo samandla ukuze iqoshwe ukushiya isikhala ukuze imbobo idlule. Uma ukuvulwa kwesendlalelo samandla kukhulu kakhulu, kuzothinta nakanjani i-loop yesignali, isignali izophoqeleka ukuba idlule, indawo ye-loop izokwanda, futhi umsindo uzokwanda. Ngesikhathi esifanayo, uma imigqa yesignali ethile igxiliswe eduze nendawo yokuvula futhi yabelane ngale loop, i-impedance evamile izodala i-crosstalk. Bheka Umfanekiso 3.

Dlula indlela evamile yomjikelezo wesignali

2) Kudingeka izintambo ezanele zaphansi ezintanjeni zokuxhuma. Isignali ngayinye idinga ukuba ne-loop yayo yesiginali ezinikele, futhi indawo eyiluphu yesiginali neluphu incane ngangokunokwenzeka, okusho ukuthi, isiginali neluphu kumele kuhambisane.

3) Beka isihlungi somsindo wokunikezwa kwamandla. Ingakwazi ukucindezela ngempumelelo umsindo ngaphakathi kwamandla kagesi futhi ithuthukise ukulwa nokuphazamiseka nokuphepha kwesistimu. Futhi iyisihlungi somsakazo esinezinhlangothi ezimbili, esingakwazi ukuhlunga kuphela ukuphazamiseka komsindo okwethulwa entanjeni yamandla (ukuvimbela ukuphazamiseka kwezinye izinto zokusebenza), kodwa futhi sihlunge umsindo okhiqizwa ngokwaso (ukugwema ukuphazanyiswa ezinye izinto zokusebenza). ), futhi iphazamise imodi ye-serial yemodi evamile. Zombili zinomphumela ovimbelayo.

4) Power isolation transformer. Separate the power loop or the common mode ground loop of the signal cable, it can effectively isolate the common mode loop current generated in the high frequency.

5) Isilawuli sokuhlinzeka ngogesi. Ukuthola kabusha amandla ahlanzekile kunganciphisa kakhulu izinga lomsindo lamandla kagesi.

6) Izintambo. Imigqa yokufaka nokuphuma kwamandla kagesi akufanele ibekwe emaphethelweni ebhodi le-dielectric, ngaphandle kwalokho kulula ukukhiqiza imisebe futhi iphazamise ezinye izifunda noma imishini.

7) Ukunikezwa kwamandla kwe-analog nedijithali kufanele kuhlukaniswe. Amadivayisi amaza aphezulu ngokuvamile azwela kakhulu kumsindo wedijithali, ngakho-ke kokubili kufanele kuhlukaniswe futhi kuxhunywe ndawonye emnyango wendawo yokuhlinzeka amandla. Uma isignali idinga ukunweba zombili izingxenye ze-analog nedijithali, iluphu ingabekwa esibayeni sesignali ukuze kwehliswe indawo yeluphu. Njengoba kuboniswe kuMfanekiso 4.

Beka iluphu endaweni yokuwela isignali ukuze unciphise indawo eyiluphu

8) Gwema ukugqagqana kwezinto zamandla ezihlukene phakathi kwezendlalelo ezihlukene. Zinyakazise ngangokunokwenzeka, ngaphandle kwalokho umsindo wokuphakelwa kwamandla uhlanganiswe kalula nge-parasitic capacitance.

9) Hlukanisa izingxenye ezibucayi. Ezinye izingxenye, ezifana nezihibe ezikhiyiwe ngesigaba (PLL), zizwela kakhulu kumsindo wokunikezwa kwamandla. Zigcine ziqhelelene nokunikezwa kwamandla ngangokunokwenzeka.

10) Beka intambo yamandla. Ukuze kuncishiswe iluphu yesiginali, umsindo ungancishiswa ngokubeka ulayini wamandla onqenqemeni lomugqa wesiginali, njengoba kukhonjisiwe kuMfanekiso 5.

Beka intambo yamandla eduze komugqa wesignali

11) Ukuze uvimbele umsindo wokuphakelwa kwamandla ukuthi ungaphazamisi ibhodi lesifunda kanye nomsindo onqwabelene obangelwa ukuphazamiseka kwangaphandle kokunikezwa kwamandla, i-bypass capacitor ingaxhunywa emhlabathini endleleni yokuphazamiseka (ngaphandle kwemisebe), ukuze umsindo ungadlulwa phansi ukuze ugweme Ukugxambukela kwezinye izinto zokusebenza namathuluzi.

Umsindo wokuphakelwa kwamandla ukhiqizwa ngokuqondile noma ngokungaqondile kusuka kugesi futhi uphazamisa isekethe. Lapho ucindezela umthelela wayo kumjikelezo, isimiso esijwayelekile kufanele silandelwe. Ngakolunye uhlangothi, umsindo wokunikezwa kwamandla kufanele uvinjelwe ngangokunokwenzeka. Umthelela wesifunda, ngakolunye uhlangothi, kufanele futhi unciphise umthelela wezwe langaphandle noma isekethe ekunikezeni amandla, ukuze ungabhebhetheki umsindo wokunikezwa kwamandla.