Úvod
GTO (Gate-Turn-OffThyristor) je zkratka pro Gate-Turn-Off tyristor, který je odvozen od tyristoru. Lze jej však vypnout přivedením záporného pulzního proudu přes bránu, což je plně řízené zařízení.
Struktura GTO
GTO,likeordinarythyristors,isaPNPNfour-layersemiconductorstructure,andtheanodeisalsodrawnfromtheoutside.Cathodeandgate.Butunlikeordinarythyristors,GTOisamulti-elementpowerintegrateddevice.Althoughthreepolesarealsodrawnfromtheoutside,itcontainsdozensorevenhundredsofsmallGTOunitswithacommonanode.ThecathodesandgatesoftheseGTOunitsareconnectedinparallelinsidethedevice.Itisdesignedtoachievegatecontrolshut-off..
GTOinternalstructurediagramandelectricalgraphicsymbolsGTOworkingprinciple:
Fromthefigure,wecanseethecompositionofPNPandNPNThetwothyristorsV1andV2havecommonbasecurrentgainsa1anda2respectively.
1.Kdyža1+a2=1,je kritická podmínka zapnutí zařízení.
2.Whena1+a2>1,itistheconditionthatthetwotransistorsareoversaturatedandturnedon.
3.Whena1+a2<1,itistheconditionthatthesaturatedconductioncannotbemaintainedandtheshut-offconditionisnotmaintained.
Rozdíl mezi GTO a obyčejným tyristorem
1.Makea2largerwhendesigningthedevice,sothatthetransistorV2canbecontrolledsensitively,sothatGTOcanbeeasilyturnedoff.
2.Makea1+a2tendtobe1.Ordinarythyristora1+a2>=1.15,andGTOisapproximately1.05,sothatthesaturationofGTOisnotdeepwhenitisturnedon,anditisclosertocriticalsaturation,whichisThegatecanbeturnedoffcontrolprovidesapowerfulcondition.Theunfavorablefactor,theconductionistheincreaseinthepressuredropofthepipe.
3.TheareaofthecathodeofeachGTOunitintheintegratedstructureissmall,andthedistancebetweenthegateandthecathodeisgreatlyshortened,whichmakesthelateralresistanceoftheP2baseregionsmall,andthegatedrawsalargercurrentbecomepossible.
4.Má rychlejší zapínací proces než běžné tyristory a snese vyšší napětí.
Hlavní parametry GTO
1.Maximální vypnutíanostejnosměrný IATO.
2.CurrentshutdowngainβOff=IATO/IGM.
IGMisthemaximumvalueofnegativegatepulsecurrent.βOffisgenerallyonlyabout5.ThisisthemaindisadvantageofGTO.
3.Turn-ontimeTonTurn-ontimereferstothesumofthedelaytimeandtherisetime.ThedelaytimeofGTOisgenerally1~2us,andtherisetimeincreaseswiththeincreaseofthehomomorphicanodecurrentvalue.
4.Turn-offtimeToffTurn-offtimereferstothesumofstoragetimeandfalltime,excludingtailtime.ThestoragetimeofGTOincreaseswiththeincreaseofanodecurrentvalue,andthefalltimeisgenerallylessthan2us.
Tyristor s asistovaným vypínáním brány
Thegate-assistedturn-offthyristorwillonlyaddnegativevoltagetothegateatacertainmomentaftertheanodecurrentcrossesandreverses,sothatthedeviceresumesblockingGTO.Thegate-assistedturn-offthyristorusuallyadoptsanenlargedgateandcathodeshort-circuitstructure,andthegateandcathodepatternsadoptahighlyinterdigitatedstructure.Theadvantagesofthisdeviceareshortturn-offtime,goodturn-oncharacteristics,andhigherallowableon-statecurrentriserateandon-statevoltageriserate.Itcanbeusedtoformcircuitswithhigheroperatingfrequenciessuchaschoppersandinverters.