Introductio
GTO (Gate-Turn-Off Thyristor) è l'abbreviazione di Gate-Turn-Off Thyristor, che è un derivato del tiristore.
ThestructureofGTO
GTO,likeordinarythyristors,isaPNPNfour-layersemiconductorstructure,andtheanodeisalsodrawnfromtheoutside.Cathodeandgate.Butunlikeordinarythyristors,GTOisamulti-elementpowerintegrateddevice.Althoughthreepolesarealsodrawnfromtheoutside,itcontainsdozensorevenhundredsofsmallGTOunitswithacommonanode.ThecathodesandgatesoftheseGTOunitsareconnectedinparallelinsidethedevice.Itisdesignedtoachievegatecontrolshut-off..
GTOinternalstructurediagramandelectricalgraphicsymbolsGTOworkingprinciple:
Fromthefigure,wecanseethecompositionofPNPandNPNThetwothyristorsV1andV2havecommonbasecurrentgainsa1anda2respectively.
1. Whena1+a2=1, itisthecriticalturn-onconditionofthedevice.
2.Whena1+a2>1,itistheconditionthatthetwotransistorsareoversaturatedandturnedon.
3.Whena1+a2<1,itistheconditionthatthesaturatedconductioncannotbemaintainedandtheshut-offconditionisnotmaintained.
ThedifferencebetweenGTOandordinarythyristor
1.Makea2largerwhendesigningthedevice,sothatthetransistorV2canbecontrolledsensitively,sothatGTOcanbeeasilyturnedoff.
2.Makea1+a2tendtobe1.Ordinarythyristora1+a2>=1.15,andGTOisapproximately1.05,sothatthesaturationofGTOisnotdeepwhenitisturnedon,anditisclosertocriticalsaturation,whichisThegatecanbeturnedoffcontrolprovidesapowerfulcondition.Theunfavorablefactor,theconductionistheincreaseinthepressuredropofthepipe.
3.TheareaofthecathodeofeachGTOunitintheintegratedstructureissmall,andthedistancebetweenthegateandthecathodeisgreatlyshortened,whichmakesthelateralresistanceoftheP2baseregionsmall,andthegatedrawsalargercurrentbecomepossible.
4. Ithasafasterturn-processus quam ordinarii thyristores, andit plus intentionis.
ThemainparametersofGTO
1.ThemaximumshutdownanodecurrentIATO.
2.CurrentshutdowngainβOff=IATO/IGM.
IGMisthemaximumvalueofnegativegatepulsecurrent.βOffisgenerallyonlyabout5.ThisisthemaindisadvantageofGTO.
3.Turn-ontimeTonTurn-ontimereferstothesumofthedelaytimeandtherisetime.ThedelaytimeofGTOisgenerally1~2us,andtherisetimeincreaseswiththeincreaseofthehomomorphicanodecurrentvalue.
4.Turn-offtimeToffTurn-offtimereferstothesumofstoragetimeandfalltime,excludingtailtime.ThestoragetimeofGTOincreaseswiththeincreaseofanodecurrentvalue,andthefalltimeisgenerallylessthan2us.
Porta assistedturn-offthyristor
Thegate-assistedturn-offthyristorwillonlyaddnegativevoltagetothegateatacertainmomentaftertheanodecurrentcrossesandreverses,sothatthedeviceresumesblockingGTO.Thegate-assistedturn-offthyristorusuallyadoptsanenlargedgateandcathodeshort-circuitstructure,andthegateandcathodepatternsadoptahighlyinterdigitatedstructure.Theadvantagesofthisdeviceareshortturn-offtime,goodturn-oncharacteristics,andhigherallowableon-statecurrentriserateandon-statevoltageriserate.Itcanbeusedtoformcircuitswithhigheroperatingfrequenciessuchaschoppersandinverters.