Fahimtar MOSFET a cikin labarin daya

Hoto 3 Juriya na thermal na MOSFET lokacin da ake amfani da bugun jini

A zahiri, zamu iya raba yadda ake zaɓar MOSFET zuwa matakai huɗu.

Mataki na farko: zaɓi tashar N ko tashar P

Mataki na farko na zaɓar na'urar da ta dace don ƙirar ku shine yanke shawarar ko za a yi amfani da tashar N-channel ko P-channel MOSFET. A cikin aikace-aikacen wutar lantarki na yau da kullun, lokacin da MOSFET ta haɗa zuwa ƙasa kuma an haɗa kaya zuwa babban ƙarfin lantarki, MOSFET yana ƙirƙirar maɓalli mai ƙarancin gefe. A cikin ƙaramin gefe, MOSFETs N-channel yakamata a yi amfani da shi saboda la'akari da ƙarfin lantarki da ake buƙata don kashe na'urar. Lokacin da MOSFET ta haɗa da bas ɗin da lodi zuwa ƙasa, ana amfani da maɓalli mai tsayi. P-tashar MOSFETs yawanci ana amfani da su a cikin wannan topology, wanda kuma ya faru ne saboda la'akari da ƙarfin lantarki. Don zaɓar na'urar da ta dace don aikace-aikacenku, dole ne ku ƙayyade ƙarfin lantarki da ake buƙata don fitar da na'urar da hanya mafi sauƙi don yin ta a cikin ƙirar ku. Mataki na gaba shine tantance ƙimar ƙarfin lantarki da ake buƙata, ko matsakaicin ƙarfin lantarki da na'urar zata iya jurewa. Mafi girman ƙimar ƙarfin lantarki, mafi girman farashin na'urar. Dangane da ƙwarewar aiki, ƙimar ƙarfin lantarki yakamata ya zama mafi girma fiye da babban ƙarfin lantarki ko ƙarfin motar bas. Wannan zai ba da isasshen kariya ta yadda MOSFET ba za ta gaza ba. Lokacin zabar MOSFET, yana da mahimmanci don ƙayyade matsakaicin ƙarfin lantarki wanda za'a iya jurewa daga magudanar ruwa zuwa tushen, wato, matsakaicin VDS. Yana da mahimmanci a san cewa matsakaicin ƙarfin lantarki MOSFET na iya jure canje-canje tare da zafin jiki. Dole ne masu ƙira su gwada bambance-bambancen irin ƙarfin lantarki akan duk iyakar zafin aiki. Ƙididdigar ƙarfin lantarki dole ne ya sami isasshen gefe don rufe wannan kewayon bambancin don tabbatar da cewa kewaye ba za ta gaza ba. Sauran abubuwan aminci waɗanda injiniyoyi ke buƙatar la'akari da su sun haɗa da wutar lantarki mai wucewa ta hanyar sauya kayan lantarki kamar injina ko taswira. Ƙimar wutar lantarki ta bambanta don aikace-aikace daban-daban; yawanci, 20V don na'urori masu ɗaukuwa, 20-30V don samar da wutar lantarki na FPGA, da 450-600V don aikace-aikacen 85-220VAC.

Mataki 2: Ƙayyade ƙimar halin yanzu

Mataki na biyu shine zabar ƙimar MOSFET na yanzu. Dangane da tsarin da'irar, wannan ƙimar halin yanzu yakamata ya zama matsakaicin halin yanzu wanda kaya zai iya jurewa a ƙarƙashin kowane yanayi. Kama da yanayin wutar lantarki, dole ne mai zane ya tabbatar da cewa MOSFET da aka zaɓa zai iya jure wa wannan ƙimar na yanzu, koda lokacin da tsarin ke haifar da spikes na yanzu. Yanayin halin yanzu guda biyu da aka yi la'akari da su sune yanayin ci gaba da bugun bugun jini. A cikin ci gaba da tafiyar da yanayin, MOSFET yana cikin tsayayyen yanayi, inda halin yanzu ke gudana ta hanyar na'urar. Ƙaƙwalwar bugun jini tana nufin babban hawan jini (ko ƙarar halin yanzu) da ke gudana ta cikin na'urar. Da zarar an ƙayyade iyakar halin yanzu a ƙarƙashin waɗannan sharuɗɗan, kawai batun zaɓin na'ura ce da za ta iya ɗaukar wannan matsakaicin halin yanzu. Bayan zabar ƙimar halin yanzu, asarar tafiyarwa dole ne kuma a ƙididdige shi. A cikin ainihin yanayi, MOSFET ba na'ura ce mai kyau ba saboda akwai asarar makamashin lantarki yayin tsarin tafiyarwa, wanda ake kira asarar gudanarwa. MOSFET yana yin kama da m resistor lokacin "kunna", wanda RDS(ON) na na'urar ya ƙaddara kuma yana canzawa sosai tare da zafin jiki. Ana iya ƙididdige asarar wutar lantarki ta Iload2 × RDS(ON). Tun lokacin juriya yana canzawa tare da zafin jiki, asarar wutar kuma zata canza daidai gwargwado. Mafi girman ƙarfin wutar lantarki VGS da ake amfani da shi ga MOSFET, ƙarami RDS(ON) zai kasance; Sabanin haka, mafi girman RDS(ON) zai kasance. Ga mai tsara tsarin, wannan shine inda kasuwancin ke shigowa dangane da ƙarfin tsarin. Don ƙirar ƙirar šaukuwa, yana da sauƙi (kuma mafi yawan gama gari) don amfani da ƙananan ƙarfin lantarki, yayin da don ƙirar masana'antu, ana iya amfani da ƙananan ƙarfin lantarki. Lura cewa juriya na RDS(ON) zai tashi kadan tare da halin yanzu. Ana iya samun bambance-bambance a cikin sigogin lantarki daban-daban na resistor RDS(ON) a cikin takardar bayanan fasaha da masana'anta suka bayar. Fasaha tana da tasiri mai mahimmanci akan halayen na'ura, saboda wasu fasahohin suna ƙara haɓaka RDS(ON) lokacin haɓaka matsakaicin VDS. Don irin wannan fasaha, idan kuna da niyyar rage VDS da RDS(ON), dole ne ku ƙara girman guntu, ta haka ƙara girman fakitin da ya dace da farashin haɓaka masu alaƙa. Akwai fasahohi da yawa a cikin masana'antar da ke ƙoƙarin sarrafa haɓakar girman guntu, mafi mahimmancin su shine tashoshi da fasahar daidaita caji. A cikin fasahar maɓalli, rami mai zurfi yana cikin wafer, yawanci ana tanada shi don ƙananan ƙarfin lantarki, don rage juriya RDS(ON). Don rage tasirin matsakaicin VDS akan RDS (ON), an yi amfani da ginshiƙin girma na epitaxial / etching ginshiƙi yayin aiwatar da ci gaba. Misali, Fairchild Semiconductor ya haɓaka fasaha mai suna SuperFET wanda ke ƙara ƙarin matakan masana'antu don rage RDS(ON). Wannan mayar da hankali kan RDS (ON) yana da mahimmanci saboda yayin da raguwar ƙarfin lantarki na daidaitaccen MOSFET ya karu, RDS (ON) yana ƙaruwa da yawa kuma yana haifar da karuwa a girman mutu. Tsarin SuperFET yana canza alaƙar da ke tsakanin RDS(ON) da girman wafer zuwa alaƙar layi. Ta wannan hanyar, na'urori na SuperFET na iya cimma madaidaicin ƙarancin RDS(ON) a cikin ƙananan masu girma dabam, har ma da raguwar ƙarfin lantarki har zuwa 600V. Sakamakon shi ne cewa za a iya rage girman wafer har zuwa 35%. Ga masu amfani na ƙarshe, wannan yana nufin raguwa mai girma a girman kunshin.

Mataki na Uku: Ƙayyade Bukatun Thermal

Mataki na gaba don zaɓar MOSFET shine ƙididdige buƙatun thermal na tsarin. Dole ne masu zanen kaya suyi la'akari da yanayi guda biyu daban-daban, mafi munin yanayi da kuma ainihin yanayin duniya. Ana ba da shawarar yin amfani da sakamakon ƙididdiga mafi muni, saboda wannan sakamakon yana ba da mafi girman ƙimar aminci kuma yana tabbatar da cewa tsarin ba zai gaza ba. Hakanan akwai wasu bayanan ma'auni waɗanda ke buƙatar kulawa akan takardar bayanan MOSFET; kamar juriya na thermal tsakanin mahaɗin semiconductor na na'urar da aka haɗa da muhalli, da matsakaicin zafin haɗuwa. Matsakaicin yanayin mahaɗin na'urar daidai yake da matsakaicin zafin yanayi tare da samfurin juriya na zafi da tarwatsewar wuta (zazzabi na mahaɗa = matsakaicin zafin yanayi + [juriya ta thermal × lalata wutar lantarki]). Dangane da wannan ma'auni, za'a iya warware iyakar ƙarfin wutar lantarki na tsarin, wanda yake daidai da I2 × RDS (ON) ta ma'anar. Tun da mai zane ya ƙayyade iyakar halin yanzu da zai wuce ta na'urar, RDS(ON) za a iya ƙididdige shi a yanayin zafi daban-daban. Ya kamata a lura cewa lokacin da ake hulɗa da samfurori masu sauƙi na thermal, masu zanen kaya dole ne su yi la'akari da ƙarfin zafin jiki na mahaɗin semiconductor / na'ura da akwati / yanayi; wannan yana buƙatar cewa bugu na allon kewayawa da kunshin kada su yi zafi nan da nan. Rushewar dusar ƙanƙara yana nufin cewa jujjuya wutar lantarki akan na'urar semiconductor ya zarce matsakaicin ƙima kuma yana samar da filin lantarki mai ƙarfi don ƙara ƙarfin halin yanzu a cikin na'urar. Wannan halin yanzu zai ɓata wuta, ƙara yawan zafin na'urar, kuma yana iya lalata na'urar. Kamfanonin Semiconductor za su gudanar da gwajin dusar ƙanƙara a kan na'urori, ƙididdige ƙarfin wutar lantarkin su, ko gwada ƙarfin na'urar. Akwai hanyoyi guda biyu don ƙididdige ƙimar wutar lantarki da aka ƙididdigewa; daya shine hanyar ƙididdiga kuma ɗayan shine lissafin thermal. Ana amfani da lissafin zafin jiki sosai saboda ya fi aiki. Yawancin kamfanoni sun ba da cikakkun bayanai game da gwajin na'urar su. Misali, Fairchild Semiconductor yana bada "Power MOSFET Avalanche Guidelines" (Power MOSFET Avalanche Guidelines-ana iya saukewa daga gidan yanar gizon Fairchild). Baya ga na'ura mai kwakwalwa, fasaha kuma tana da babban tasiri akan tasirin avalanche. Misali, haɓakar girman mutuƙar yana ƙara juriyar ƙazamar ruwa kuma a ƙarshe yana ƙara ƙarfin na'urar. Ga masu amfani na ƙarshe, wannan yana nufin amfani da manyan fakiti a cikin tsarin.

Mataki 4: Ƙayyade aikin sauyawa

Mataki na ƙarshe na zaɓin MOSFET shine tantance aikin sauya fasalin MOSFET. Akwai sigogi da yawa waɗanda ke shafar aikin sauyawa, amma mafi mahimmanci shine ƙofar / magudanar ruwa, kofa / tushe da magudanar ruwa / iyawar tushen. Wadannan capacitors suna haifar da asarar sauyawa a cikin na'urar saboda ana cajin su duk lokacin da suka canza. Don haka an rage saurin sauyawa na MOSFET, kuma an rage ingancin na'urar. Don ƙididdige yawan asarar da ke cikin na'ura yayin sauyawa, dole ne mai zane ya ƙididdige asarar yayin kunnawa (Eon) da asarar yayin kashewa (Eoff). Za'a iya bayyana jimlar ikon sauya MOSFET ta ma'auni mai zuwa: Psw=(Eon+Eoff)× mitar sauyawa. Cajin ƙofar (Qgd) yana da mafi girman tasiri akan sauya aikin. Dangane da mahimmancin aikin sauya fasalin, ana ci gaba da haɓaka sabbin fasahohi don magance wannan matsalar sauyawa. Ƙara girman guntu yana ƙara cajin ƙofar; wannan yana ƙara girman na'urar. Don rage asarar sauyawa, sabbin fasahohi irin su tashoshi mai kauri na kasa oxygen sun fito, suna nufin rage cajin kofa. Misali, sabuwar fasaha ta SuperFET na iya rage asarar gudanarwa da inganta aikin sauyawa ta rage RDS(ON) da cajin kofa (Qg). Ta wannan hanyar, MOSFETs na iya jure wa masu saurin wutar lantarki mai sauri (dv/dt) da masu wucewa na yanzu (di/dt) yayin sauyawa, har ma suna iya aiki da dogaro a mafi girman mitoci.