MOSFET ainihin ilimin asali da aikace-aikace

Amma dalilin da yasa yanayin ragewaMOSFETsba a yi amfani da su ba, ba a ba da shawarar zuwa kasan shi ba.

Don waɗannan MOSFETs na haɓakawa guda biyu, an fi amfani da NMOS. Dalilin shi ne cewa akan-juriya karami ne kuma mai sauƙin ƙirƙira. Don haka, ana amfani da NMOS gabaɗaya wajen sauya wutar lantarki da aikace-aikacen tuƙi. A cikin gabatarwa mai zuwa, ana amfani da NMOS galibi.

Akwai ma'auni mai ƙarfi tsakanin fil uku na MOSFET. Wannan ba shine abin da muke buƙata ba, amma ana haifar dashi ta hanyar ƙayyadaddun tsarin sarrafawa. Kasancewar karfin karfin parasitic yana sa ya zama da wahala yayin zayyana ko zabar da'ira, amma babu wata hanya ta guje masa. Za mu gabatar da shi dalla-dalla daga baya.

Akwai diode parasitic tsakanin magudanar ruwa da tushe. Wannan ake kira jiki diode. Wannan diode yana da matuƙar mahimmanci yayin tuƙi kayan aiki (kamar injina). Af, diode jiki yana wanzuwa a cikin MOSFET guda ɗaya kawai kuma yawanci ba a samun shi a cikin guntun da'ira.

2. MOSFET halayen gudanarwa

Gudanarwa yana nufin yin aiki azaman mai canzawa, wanda yayi daidai da mai kunnawa da ake rufewa.

Halin NMOS shine cewa zai kunna lokacin da Vgs ya fi wani ƙima. Ya dace a yi amfani da shi lokacin da tushen ya kasance ƙasa (ƙananan tuƙi), muddin ƙarfin ƙarfin ƙofar ya kai 4V ko 10V.

Siffofin PMOS shine cewa zai kunna lokacin da Vgs bai kai wani ƙima ba, wanda ya dace da yanayin da aka haɗa tushen tushen zuwa VCC (drive mai girma). Duk da haka, ko da yakePMOSana iya amfani dashi cikin sauƙi azaman babban direba, NMOS yawanci ana amfani dashi a cikin manyan direbobi saboda babban juriya, farashi mai girma, da ƴan nau'ikan maye gurbin.

3. MOS canza tube asarar

Ko NMOS ne ko PMOS, akwai juriya bayan an kunna shi, don haka na yanzu zai cinye makamashi akan wannan juriya. Wannan bangare na makamashin da ake amfani da shi ana kiransa hasara. Zaɓin MOSFET tare da ƙaramin juriya zai rage asarar gudanarwa. Ƙarƙashin ƙarfin MOSFET na yau akan juriya gabaɗaya yana kusa da dubun miliyoyi, kuma akwai kuma milliohms da yawa.

Lokacin da MOSFET aka kunna da kashewa, ba dole ba ne a kammala shi nan take. Wutar lantarki a fadin MOS yana da tsari mai raguwa, kuma halin yanzu yana da tsari mai girma. A wannan lokacin, daMOSFEThasara shine samfurin ƙarfin lantarki da na yanzu, wanda ake kira hasara mai canzawa. Yawanci hasarar canjin canji ta fi girma fiye da asarar gudanarwa, kuma da sauri mitar sauyawa, mafi girman asarar.

Samfurin ƙarfin lantarki da na yanzu a lokacin gudanarwa yana da girma sosai, yana haifar da babban hasara. Rage lokacin sauyawa zai iya rage asarar yayin kowane gudanarwa; rage mitar sauyawa zai iya rage adadin masu sauyawa kowane lokaci naúrar. Dukansu hanyoyin suna iya rage asarar canzawa.

Siffar motsi lokacin da MOSFET ta kunna. Ana iya ganin samfurin ƙarfin lantarki da na yau da kullun a lokacin sarrafawa yana da girma sosai, kuma asarar da aka yi ma yana da yawa. Rage lokacin sauyawa zai iya rage asarar yayin kowane gudanarwa; rage mitar sauyawa zai iya rage adadin masu sauyawa kowane lokaci naúrar. Dukansu hanyoyin suna iya rage asarar canzawa.

4. Direban MOSFET

Idan aka kwatanta da transistors na bipolar, an yi imani da cewa babu wani halin yanzu da ake buƙatar kunna MOSFET, muddin ƙarfin lantarki na GS ya fi wani ƙima. Wannan yana da sauƙin yin, amma kuma muna buƙatar gudu.

Ana iya gani a cikin tsarin MOSFET cewa akwai ƙarfin ƙarfin parasitic tsakanin GS da GD, kuma tuƙin MOSFET shine ainihin caji da fitarwa na capacitor. Yin cajin capacitor yana buƙatar halin yanzu, saboda ana iya ɗaukar capacitor a matsayin ɗan gajeren da'ira a lokacin caji, don haka halin yanzu na yanzu zai kasance mai girma. Abu na farko da ya kamata a kula da shi lokacin zabar / zana direban MOSFET shine adadin gajeriyar kewayawa na yanzu da zai iya bayarwa. ;

Abu na biyu da ya kamata a lura da shi shi ne, NMOS, wanda aka fi amfani da shi don tuki mai tsayi, yana buƙatar ƙarfin wutar lantarki ya fi ƙarfin wutar lantarki idan an kunna. Lokacin da aka kunna MOSFET mai babban gefe, ƙarfin wutar lantarki iri ɗaya ne da ƙarfin magudanar ruwa (VCC), don haka ƙarfin ƙofar yana da 4V ko 10V fiye da VCC a wannan lokacin. Idan kuna son samun ƙarfin lantarki wanda ya fi VCC girma a cikin wannan tsarin, kuna buƙatar da'irar haɓakawa ta musamman. Yawancin direbobin motoci sun haɗa famfunan caji. Ya kamata a lura cewa ya kamata a zaɓi madaidaicin capacitor na waje don samun isassun isassun wutar lantarki don fitar da MOSFET.

4V ko 10V da aka ambata a sama shine kunna wutar lantarki na MOSFETs da aka saba amfani da su, kuma ba shakka akwai buƙatar ƙyale wani yanki yayin ƙira. Kuma mafi girman ƙarfin wutar lantarki, saurin tafiyar da sauri kuma ƙarami juriya na tafiyarwa. Yanzu akwai MOSFET tare da ƙananan ƙarfin wutar lantarki da ake amfani da su a fagage daban-daban, amma a cikin tsarin lantarki na 12V, gabaɗaya 4V ya isa.

Don da'irar direban MOSFET da asararsa, da fatan za a koma zuwa AN799 na Microchip Matching MOSFET Direbobi zuwa MOSFETs. Yana da cikakken bayani, don haka ba zan ƙara yin rubutu ba.

MOSFET nau'in FET ne (ɗayan kuma shine JFET). Ana iya sanya shi zuwa yanayin haɓakawa ko yanayin ragewa, tashar P-channel ko tashar N-tashar, jimlar nau'ikan 4. Koyaya, kawai yanayin haɓakawa-yanayin N-channel MOSFET ana amfani dashi a zahiri. da MOSFET nau'in haɓakawa-nau'in P-tashar, don haka NMOS ko PMOS yawanci suna komawa ga waɗannan nau'ikan guda biyu.

5. MOSFET da'irar aikace-aikacen?

Mafi mahimmancin halayen MOSFET shine kyawawan halayensa na sauyawa, don haka ana amfani dashi sosai a cikin da'irori waɗanda ke buƙatar na'urorin lantarki, kamar sauya kayan wuta da injin tuƙi, da kuma ƙarancin haske.

Direbobin MOSFET na yau suna da buƙatu na musamman da yawa:

1. Low ƙarfin lantarki aikace-aikace

Lokacin amfani da wutar lantarki na 5V, idan ana amfani da tsarin totem na gargajiya a wannan lokacin, tunda transistor be yana da juzu'in ƙarfin lantarki kusan 0.7V, ainihin ƙarfin ƙarfin ƙarshe da ake amfani da shi a ƙofar shine kawai 4.3V. A wannan lokacin, muna zaɓar ikon ƙofar mara kyau

Akwai takamaiman haɗari lokacin amfani da MOSFET 4.5V. Irin wannan matsalar kuma tana faruwa lokacin amfani da 3V ko wasu kayan wuta mara ƙarfi.

2. Wide irin ƙarfin lantarki aikace-aikace

Wutar shigar da wutar lantarki ba ƙayyadadden ƙima ba ne, zai canza tare da lokaci ko wasu dalilai. Wannan canjin yana haifar da ƙarfin tuƙi da kewayen PWM ke bayarwa zuwa MOSFET ya zama mara ƙarfi.

Domin sanya MOSFETs amintattu a ƙarƙashin manyan ƙarfin wutar lantarki, MOSFET da yawa suna da ginanniyar sarrafa wutar lantarki don iyakance girman ƙarfin wutar lantarki da ƙarfi. A wannan yanayin, lokacin da ƙarfin tuƙi da aka bayar ya zarce ƙarfin wutar lantarki na bututu mai daidaita wutar lantarki, zai haifar da babban amfani da wutar lantarki.

Haka kuma, idan kawai ka yi amfani da ka'idar resistor voltage division don rage wutar lantarkin ƙofar, MOSFET za ta yi aiki da kyau lokacin da ƙarfin shigarwa ya yi girma, amma lokacin da aka rage ƙarfin shigarwar, wutar lantarkin ƙofar ba zai isa ba, yana haifar da matsala. gudanarwar da ba ta cika ba, don haka ta ƙara yawan amfani da wutar lantarki.

3. Dual ƙarfin lantarki aikace-aikace

A wasu da'irori masu sarrafawa, ɓangaren tunani yana amfani da irin ƙarfin lantarki na dijital na 5V ko 3.3V, yayin da ɓangaren wutar lantarki yana amfani da ƙarfin lantarki na 12V ko ma mafi girma. Ana haɗa wutar lantarki biyu zuwa ƙasa ɗaya.

Wannan yana ɗaga buƙatu don amfani da kewayawa ta yadda ɓangaren ƙananan ƙarfin lantarki zai iya sarrafa MOSFET yadda ya kamata a gefen babban ƙarfin lantarki. A lokaci guda, MOSFET a gefen babban ƙarfin lantarki kuma zai fuskanci matsalolin da aka ambata a cikin 1 da 2.

A cikin waɗannan yanayi guda uku, tsarin sandar sandar totem ba zai iya biyan buƙatun fitarwa ba, kuma yawancin direban MOSFET na ICs ba sa haɗawa da ƙayyadaddun ƙarfin wutar lantarki na ƙofar.

Don haka na tsara da'ira ta gama gari don biyan waɗannan buƙatu guda uku.

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Da'irar Direba don NMOS

Anan zan yi bincike mai sauƙi na da'irar direban NMOS:

Vl da Vh sune ƙananan ƙarancin wutar lantarki da manyan kayan wuta bi da bi. Wutar lantarki guda biyu na iya zama iri ɗaya, amma Vl bai kamata ya wuce Vh ba.

Q1 da Q2 suna samar da igiya mai jujjuyawar totem don cimma warewa yayin da tabbatar da cewa bututun direba biyu Q3 da Q4 ba sa kunna lokaci guda.

R2 da R3 suna ba da alamar wutar lantarki ta PWM. Ta hanyar canza wannan tunani, za'a iya sarrafa da'irar a wuri inda siginar siginar PWM yayi tsayi sosai.

Ana amfani da Q3 da Q4 don samar da halin yanzu. Lokacin da aka kunna, Q3 da Q4 kawai suna da ƙaramin ƙaramin ƙarfin lantarki na Vce dangane da Vh da GND. Wannan raguwar ƙarfin lantarki yawanci kusan 0.3V ne kawai, wanda yayi ƙasa da Vce na 0.7V.

R5 da R6 sune masu adawa da martani, ana amfani da su don samfurin ƙarfin lantarki. Samfurin ƙarfin lantarki yana haifar da mummunan ra'ayi mai ƙarfi ga tushe na Q1 da Q2 ta hanyar Q5, don haka yana iyakance ƙarfin wutar lantarki zuwa ƙima mai iyaka. Ana iya daidaita wannan ƙimar ta R5 da R6.

A ƙarshe, R1 yana ba da iyakokin yanzu don Q3 da Q4, da R4 na samar da ƙofar ƙofar yanzu don Mosfet, wanda shine iyakar ICE na Q3 da Q4. Idan ya cancanta, ana iya haɗa capacitor na hanzari a layi daya zuwa R4.

Wannan da'irar tana ba da fasali masu zuwa:

1. Yi amfani da ƙananan wutan lantarki da PWM don fitar da MOSFET mai girma.

2. Yi amfani da ƙaramin siginar PWM mai ƙarfi don fitar da MOSFET tare da buƙatun ƙarfin lantarki na kofa.

3. Peak iyaka na ƙofar ƙarfin lantarki

4. Input da fitarwa na halin yanzu iyaka

5. Ta hanyar amfani da resistors masu dacewa, ana iya samun ƙarancin wutar lantarki.

6. An juya siginar PWM. NMOS baya buƙatar wannan fasalin kuma ana iya magance shi ta hanyar sanya inverter a gaba.

Lokacin zayyana na'urori masu ɗaukuwa da samfuran mara waya, haɓaka aikin samfur da tsawaita rayuwar batir batutuwa biyu ne masu ƙira ke buƙatar fuskantar. Masu jujjuyawar DC-DC suna da fa'idodi na babban inganci, babban fitarwa na yanzu, da ƙarancin halin yanzu, yana mai da su dacewa sosai don kunna na'urori masu ɗaukuwa. A halin yanzu, manyan abubuwan da ke faruwa a ci gaban fasahar ƙira ta DC-DC sune: (1) Fasaha mai saurin gaske: Yayin da mitar sauyawa take ƙaruwa, girman na'urar yana raguwa, ƙarfin ƙarfin kuma yana ƙaruwa sosai. kuma an inganta amsa mai ƙarfi. . Mitar sauyawa na masu sauya DC-DC mai ƙarancin ƙarfi zai tashi zuwa matakin megahertz. (2) Fasaha mai ƙarancin fitarwa: Tare da ci gaba da haɓaka fasahar masana'anta na semiconductor, ƙarfin aiki na microprocessors da na'urorin lantarki masu ɗaukuwa suna samun ƙasa da ƙasa, wanda ke buƙatar masu canza DC-DC na gaba don samar da ƙarancin ƙarfin fitarwa don daidaitawa zuwa microprocessors. bukatu don masu sarrafawa da na'urorin lantarki masu ɗaukuwa.

Haɓaka waɗannan fasahohin sun gabatar da buƙatu mafi girma don ƙirar ƙirar guntun wutar lantarki. Da farko, yayin da mitar sauyawa ta ci gaba da karuwa, ana sanya manyan buƙatu akan aikin abubuwan canzawa. A lokaci guda, dole ne a samar da da'irori masu juyawa masu kama da juna don tabbatar da cewa abubuwan da ke canzawa suna aiki akai-akai a jujjuya mitoci har zuwa MHz. Na biyu, don na'urorin lantarki masu ɗaukuwa masu amfani da baturi, ƙarfin aiki na kewaye yana da ƙasa (ɗaukar baturi na lithium a matsayin misali, ƙarfin aiki shine 2.5 ~ 3.6V), saboda haka, ƙarfin aiki na guntu wutar lantarki yana da ƙasa.

MOSFET yana da ƙarancin juriya kuma yana cinye ƙarancin kuzari. MOSFET galibi ana amfani dashi azaman canjin wuta a cikin mashahurin guntuwar DC-DC masu inganci a halin yanzu. Duk da haka, saboda babban ƙarfin kuzarin MOSFET, ƙarfin ƙofa na bututun sauyawa na NMOS gabaɗaya ya kai dubun picofarads. Wannan yana sanya gaba mafi girma buƙatun don ƙira babban aiki mita DC-DC Converter sauya tube drive kewaye.

A cikin ƙananan ƙirar ULSI masu ƙarancin ƙarfin lantarki, akwai nau'ikan CMOS da BiCMOS da'irori dabaru ta amfani da tsarin haɓaka bootstrap da tuƙi a matsayin manyan kaya masu ƙarfi. Wadannan da'irori na iya aiki akai-akai tare da ƙarfin samar da wutar lantarki ƙasa da 1V, kuma suna iya aiki a mitar dubun megahertz ko ma ɗaruruwan megahertz tare da ƙarfin ɗaukar nauyi na 1 zuwa 2pF. Wannan labarin yana amfani da da'irar haɓaka haɓakar bootstrap don ƙira da'irar tuƙi tare da babban ƙarfin ƙarfin ɗaukar nauyi wanda ya dace da ƙarancin wutar lantarki, haɓaka mitar mai girma na DC-DC masu juyawa. An ƙera da'irar bisa tsarin Samsung AHP615 BiCMOS kuma an tabbatar da shi ta hanyar simintin Hspice. Lokacin da ƙarfin lantarki ya kasance 1.5V kuma ƙarfin ɗaukar nauyi shine 60pF, mitar aiki na iya kaiwa fiye da 5MHz.

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MOSFET halaye masu sauyawa

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1. Halayen tsaye

A matsayin abin canzawa, MOSFET kuma yana aiki a cikin jihohi biyu: a kashe ko a kunne. Tunda MOSFET abu ne mai sarrafa wutar lantarki, yanayin aikin sa galibi ana ƙaddara shi ta hanyar ƙarfin tushen ƙofar uGS.

Halayen aikin sune kamar haka:

※ uGS＜ kunna wutar lantarki UT: MOSFET yana aiki a cikin yanki mai yankewa, tushen magudanar ruwa na yanzu iDS shine ainihin 0, ƙarfin fitarwar uDS≈UDD, kuma MOSFET yana cikin yanayin "kashe".

※ uGS> Kunna wutar lantarki UT: MOSFET yana aiki a cikin yankin gudanarwa, magudanar ruwa na yanzu iDS=UDD/(RD+rDS). Daga cikin su, rDS shine juriyar magudanar ruwa lokacin da MOSFET ta kunna. Wutar lantarki ta fitarwa UDS=UDD?rDS/(RD+rDS), idan rDS＜RD, uDS≈0V, MOSFET tana cikin "kan" jihar.

2. Dynamic halaye

MOSFET kuma tana da tsarin canji lokacin kunnawa da kashe jihohi, amma halayenta masu ƙarfi sun dogara ne akan lokacin da ake buƙata don caji da fitar da madaidaicin ƙarfin da ke da alaƙa da kewaye, da tara caji da fitarwa lokacin da bututun kanta ke kunne da kashewa. Lokacin watsawa kadan ne.

Lokacin da ƙarfin shigarwar ui ya canza daga babba zuwa ƙasa kuma MOSFET yana canzawa daga kan jihar zuwa kashewa, wutar lantarki UDD tana cajin ƙarfin ƙarfin CL ta hanyar RD, da lokacin caji akai-akai τ1=RDCL. Saboda haka, ƙarfin lantarki na uo yana buƙatar wucewa ta wani ɗan lokaci kafin ya canza daga ƙananan matakin zuwa babban matakin; lokacin da ƙarfin shigarwar ui ya canza daga ƙasa zuwa babba kuma MOSFET yana canzawa daga kashe kashewa zuwa jihar, cajin kan ƙarfin ƙarfin CL yana wucewa ta rDS Discharge yana faruwa tare da tsayayyen lokacin fitarwa τ2≈rDSCL. Ana iya ganin cewa ƙarfin wutar lantarki na Uo shima yana buƙatar wani ɗan lokaci kafin ya iya canzawa zuwa ƙaramin matakin. Amma saboda rDS ya fi RD ƙarami sosai, lokacin jujjuyawa daga yankewa zuwa gudanarwa ya fi guntu lokacin jujjuyawa daga gudanarwa zuwa yankewa.

Tunda juriyar juriyar magudanar ruwa na MOSFET lokacin da aka kunna ta ya fi girma juriya rCES na transistor, kuma juriya na magudanar ruwa na waje RD shima ya fi girma juriya mai tattara RC na transistor, lokacin caji da fitarwa. na MOSFET ya fi tsayi, yin MOSFET Saurin sauyawa ya yi ƙasa da na transistor. Koyaya, a cikin da'irori na CMOS, tunda da'irar caji da da'irar fitarwa duka biyun ƙananan juriya ne, ayyukan caji da fitarwa suna da sauri, yana haifar da babban saurin sauyawa don kewayawar CMOS.