Ukukhethwa Kwephakheji Ye-MOSFET Yokushintsha I-Tube kanye Nemidwebo Yesifunda

Isinyathelo sokuqala siwukukhethaAma-MOSFET, eza ngezinhlobo ezimbili eziyinhloko: I-N-channel ne-P-channel. Ezinhlelweni zamandla, ama-MOSFET angacatshangwa njengamaswishi kagesi. Lapho i-voltage evumayo yengezwa phakathi kwesango nomthombo we-N-channel MOSFET, ukushintshwa kwayo kuyaqhuba. Ngesikhathi sokuqhuba, i-current ingageleza ngokushintsha kusuka ku-drain kuya emthonjeni. Kukhona ukumelana kwangaphakathi phakathi komsele kanye nomthombo obizwa nge-on-resistance RDS(ON). Kumele kucace ukuthi isango le-MOSFET liyisiphephelo esiphezulu se-impedance, ngakho-ke i-voltage ihlale yengezwa esangweni. Lokhu ukumelana nomhlabathi isango elixhunywe kuwo kumdwebo wesifunda owethulwe kamuva. Uma isango lishiywe lilenga, idivayisi ngeke isebenze ngendlela eklanywe ngayo futhi ingase ivule noma ivale ngezikhathi ezingafanele, okuholela ekulahlekeni kwamandla okungaba khona ohlelweni. Uma i-voltage phakathi komthombo nesango inguziro, iswishi iyacisha futhi yamanje iyeke ukugeleza ocingweni. Nakuba idivayisi ivaliwe kuleli phuzu, kusenesipho esincane samanje, esibizwa ngokuthi ukuvuza kwamanje, noma i-IDSS.

 

 

Isinyathelo 1: Khetha i-N-channel noma i-P-channel

Isinyathelo sokuqala ekukhetheni idivayisi efanele yomklamo ukunquma ukuthi uzosebenzisa i-N-channel noma i-P-channel MOSFET. ohlelweni lwamandla olujwayelekile, lapho i-MOSFET igxiliwe futhi umthwalo uxhunywe ku-voltage ye-trunk, i-MOSFET ihlanganisa iswishi ehlangothini ye-voltage ephansi. Ekushintsheni ohlangothini lwe-voltage ephansi, isiteshi esingu-NI-MOSFETkufanele isetshenziswe ngenxa yokucatshangelwa kwe-voltage edingekayo ukuze uvale noma uvule idivayisi. Uma i-MOSFET ixhunywe ebhasini futhi umthwalo uphansi, inkinobho ye-voltage ephezulu kufanele isetshenziswe. I-P-channel MOSFET ivamise ukusetshenziswa kule topology, futhi uma kucatshangelwa i-voltage drive.

Isinyathelo sesi-2: Nquma isilinganiso samanje

Isinyathelo sesibili ukukhetha isilinganiso samanje se-MOSFET. Ngokuya ngesakhiwo sesifunda, lesi silinganiso samanje kufanele sibe umkhawulo wamanje umthwalo ongamelana nawo ngaphansi kwazo zonke izimo. Ngokufanayo nesimo se-voltage, umklami kufanele aqinisekise ukuthi i-MOSFET ekhethiwe ingakwazi ukumelana nalesi silinganiso samanje, ngisho nalapho isistimu ikhiqiza ama-spike currents. Izimo ezimbili zamanje ezicatshangelwayo ziyimodi eqhubekayo kanye nama-pulse spikes. Le pharamitha isuselwe ku-FDN304P yeshubhu DATASHEET njengereferensi futhi amapharamitha ayaboniswa emfanekisweni:

 

 

 

Kumodi yokuqhuba eqhubekayo, i-MOSFET isesimweni esingaguquki, lapho okwamanje kugeleza ngokuqhubekayo kudivayisi. Ama-pulse spikes yilapho kunenani elikhulu lokuhlinzwa (noma i-spike current) eligeleza ocingweni. Uma inani eliphezulu lamanje ngaphansi kwalezi zimo selinqunyiwe, kumane nje kuyindaba yokukhetha ngokuqondile idivayisi engakwazi ukumelana nalesi silinganiso esiphezulu.

Ngemuva kokukhetha i-current elinganiselwe, kufanele futhi ubale ukulahlekelwa kwe-conduction. Empeleni, iI-MOSFETakuyona idivayisi ekahle, ngoba inqubo conductive kuyoba ukulahlekelwa amandla, okubizwa ngokuthi conduction ukulahlekelwa. I-MOSFET ku-"on" njengokumelana okuguquguqukayo, okunqunywa i-RDS (ON) yedivayisi, kanye nezinga lokushisa nezinguquko ezibalulekile. Ukuchithwa kwamandla kwedivayisi kungabalwa ku-Iload2 x RDS(ON), futhi njengoba ukumelana nokumelana kushintshana nezinga lokushisa, ukuchithwa kwamandla kuyehluka ngokulinganayo. Uma iphezulu i-voltage VGS esetshenziswa ku-MOSFET, i-RDS(ON) izoba mancane; ngokuphambene lapho i-RDS(ON) izoba phezulu. Kumklami wesistimu, kulapho uhwebo luqala khona ukusebenza ngokuya ngevolthi yesistimu. Ngemiklamo ephathekayo, kulula (futhi kuvame kakhulu) ukusebenzisa ama-voltage aphansi, kuyilapho emiklamo yezimboni, ama-voltage aphezulu angasetshenziswa. Qaphela ukuthi ukumelana ne-RDS(ON) kukhuphuka kancane ngokwamanje. Ukwehluka kumapharamitha ahlukahlukene kagesi we-RDS(ON) resistor kungatholwa eshidini ledatha yobuchwepheshe elinikezwe umenzi.

 

 

 

Isinyathelo sesi-3: Thola Izidingo Zokushisa

Isinyathelo esilandelayo ekukhetheni i-MOSFET ukubala izidingo ezishisayo zesistimu. Umklami kufanele acabangele izimo ezimbili ezihlukene, icala elibi kakhulu kanye necala eliyiqiniso. Isibalo sesimo esibi kakhulu siyanconywa ngoba lo mphumela uhlinzeka ngomkhawulo omkhulu wokuphepha futhi uqinisekisa ukuthi isistimu ngeke ihluleke. Kukhona nezilinganiso ezithile okufanele uziqaphele eshidini ledatha le-MOSFET; njengokumelana nokushisa okuphakathi kokuhlangana kwe-semiconductor yedivayisi epakishiwe nendawo, kanye nezinga lokushisa eliphezulu lokuhlangana.

 

Izinga lokushisa le-junction yedivayisi lilingana nezinga lokushisa eliphakeme kakhulu le-ambient kanye nomkhiqizo wokumelana nokushisa kanye nokuchithwa kwamandla (izinga lokushisa lokuhlangana = izinga lokushisa eliphakeme le-ambient + [ukumelana nokushisa × ukuchithwa kwamandla]). Kusukela kulesi sibalo ubukhulu bokuchithwa kwamandla esistimu kungaxazululeka, okusho ngencazelo elingana ne-I2 x RDS(ON). Njengoba abasebenzi benqume inani eliphezulu lamanje elizodlula kudivayisi, i-RDS(ON) ingabalwa kumazinga okushisa ahlukene. Kubalulekile ukuqaphela ukuthi lapho usebenzisana namamodeli alula okushisa, umklami kufanele futhi acabangele umthamo wokushisa we-semiconductor junction/device case kanye nekesi/imvelo; okungukuthi, kuyadingeka ukuthi ibhodi lesifunda eliphrintiwe kanye nephakheji lingafudumala ngokushesha.

Imvamisa, i-PMOSFET, kuzoba khona i-parasitic diode ekhona, umsebenzi we-diode ukuvimbela ukuxhumana okubuyela emuva komthombo, ku-PMOS, inzuzo ngaphezu kwe-NMOS ukuthi i-voltage yayo yokuvula ingaba ngu-0, kanye nomehluko we-voltage phakathi I-voltage ye-DS ayiningi, kuyilapho i-NMOS esesimweni idinga ukuthi i-VGS ibe nkulu kunombundu, okuzoholela ekutheni i-voltage yokulawula ibe nkulu ngokungenakugwenywa kune-voltage edingekayo, futhi kuzoba nenkinga engadingekile. I-PMOS ikhethwa njengokushintsha kokulawula kulezi zinhlelo zokusebenza ezimbili ezilandelayo:

 

Izinga lokushisa le-junction yedivayisi lilingana nezinga lokushisa eliphakeme kakhulu le-ambient kanye nomkhiqizo wokumelana nokushisa kanye nokuchithwa kwamandla (izinga lokushisa lokuhlangana = izinga lokushisa eliphakeme le-ambient + [ukumelana nokushisa × ukuchithwa kwamandla]). Kusukela kulesi sibalo ubukhulu bokuchithwa kwamandla esistimu kungaxazululeka, okusho ngencazelo elingana ne-I2 x RDS(ON). Njengoba umklami enqume inani eliphezulu lamanje elizodlula kudivayisi, i-RDS(ON) ingabalwa kumazinga okushisa ahlukene. Kubalulekile ukuqaphela ukuthi lapho usebenzisana namamodeli alula okushisa, umklami kufanele futhi acabangele umthamo wokushisa we-semiconductor junction/device case kanye nekesi/imvelo; okungukuthi, kuyadingeka ukuthi ibhodi lesifunda eliphrintiwe kanye nephakheji lingafudumala ngokushesha.

Imvamisa, i-PMOSFET, kuzoba khona i-parasitic diode ekhona, umsebenzi we-diode ukuvimbela ukuxhumana okubuyela emuva komthombo, ku-PMOS, inzuzo ngaphezu kwe-NMOS ukuthi i-voltage yayo yokuvula ingaba ngu-0, kanye nomehluko we-voltage phakathi I-voltage ye-DS ayiningi, kuyilapho i-NMOS esesimweni idinga ukuthi i-VGS ibe nkulu kunombundu, okuzoholela ekutheni i-voltage yokulawula ibe nkulu ngokungenakugwenywa kune-voltage edingekayo, futhi kuzoba nenkinga engadingekile. I-PMOS ikhethwa njengokushintsha kokulawula kulezi zinhlelo zokusebenza ezimbili ezilandelayo:

Uma ubheka le sekethi, isiginali yokulawula i-PGC ilawula ukuthi i-V4.2 inika amandla noma cha ku-P_GPRS. Le sekethe, amatheminali omthombo kanye namapayipi okudonsa amanzi akuxhumekile emuva, u-R110 no-R113 akhona ngomqondo wokuthi isango lokulawula elingu-R110 alilikhulu kakhulu, u-R113 ulawula isango elivamile, u-R113 ukudonsela phezulu, kusukela ku-PMOS. , kodwa futhi kungabonakala njengokudonsela phezulu kusiginali yokulawula, lapho izikhonkwane zangaphakathi ze-MCU kanye nokudonsa, okungukuthi, ukukhishwa kwe-drain evulekile lapho okukhiphayo kuvulekile, futhi awukwazi ukushayela i-PMOS. off, ngalesi sikhathi, kuyadingeka voltage yangaphandle inikezwe ukudonsa-up, ngakho resistor R113 udlala izindima ezimbili. Izodinga i-voltage yangaphandle ukuze inikeze ukudonsa, ngakho-ke i-resistor R113 idlala izindima ezimbili. I-r110 ingaba yincane, iye ku-100 ohms nayo ingaba.