an-978

(HEXFETisatrademarkofInternationalRectifier)TableofContentsPageGatedriverequirementofhigh-sidedevices...............................................................2Atypicalblockdiagram...............................................................................................3Howtoselectthebootstrapcomponents....................................................................5HowtocalculatethepowerdissipationinanMGD.....................................................6HowtodealwithnegativetransientsontheVspin.....................................................9Layoutandothergeneralguidelines...........................................................................11Howtoboostgatedrivecurrenttodrivemodules.......................................................14Howtoprovideacontinuousgatedrive......................................................................17Howtogenerateanegativegatebias.........................................................................19Howtodriveabuckconverter.....................................................................................22Dualforwardconverterandswitchedreluctancemotordrives...................................24Fullbridgewithcurrentmodecontrol..........................................................................24Brushlessandinductionmotordrives.........................................................................26Push-pull.....................................................................................................................27High-sideP-channel....................................................................................................27Troubleshootingguidelines.........................................................................................28(thedrainisconnectedtothehighvoltagerail,asshowninFigure1)driveninfullenhancement(i.e.,lowestvoltagedropacrossitsterminals)canbesummarizedasfollows:1.Gatevoltagemustbe10Vto15Vhigherthanthesourcevoltage.Beingahigh-sideswitch,suchgatevoltagewouldhavetobehigherthantherailvoltage,whichisfrequentlythehighestvoltageavailableinthesystem.2.Thegatevoltagemustbecontrollablefromthelogic,whichisnormallyreferencedtoground.Thus,thecontrolsignalshavetobelevel-shiftedtothesourceofthehigh-sidepowerdevice,which,inmostapplications,swingsbetweenthetworails.3.Thepowerabsorbedbythegatedrivecircuitryshouldnotsignificantlyaffecttheoverallefficiency.Figure1:PowerMOSFETintheHigh-SideConfigurationWiththeseconstraintsinmind,severaltechniquesarepresentlyusedtoperformthisfunction,asshowninprincipleinTableI(seepg.29).Eachbasiccircuitcanbeimplementedinawidevarietyofconfigurations.InternationalRectifier’sfamilyofMOS-gatedrivers(MGDs)integratemostofthefunctionsrequiredtodriveonehigh-sideandonelow-sidepowerMOSFETorIGBTinacompact,highperformancepackage.Withtheadditionoffewcomponents,theyprovideveryfastswitchingspeeds,asshowninTableII(seepg.30)fortheIRS2110,andlowpowerdissipation.Theycanoperateonthebootstrapprincipleorwithafloatingpowersupply.Usedinthebootstrapmode,theycanoperateinmostapplicationsfromfrequenciesinthetensofHzuptohundredsofkHz.GATESOURCEV+HIGHVOLTAGERAIL:BlockDiagramoftheIRS2110Figure3:SiliconCross-SectionShowingtheParasiticCapacitancesVDDHINSDLINVSSRSRSVDD/VCCLEVELTRANSLATORANDPWDISCRIMINATORPULSEGENERATORUVDETECTDELAYVDD/VBSLEVELTRANSLATORPULSEDISCRIMINATORCd-subCb-subUVDETECTLATCHLOGICQQVBHOVSLO2COMMCBOOTVCCVRVDD/VCCLEVELTRANSLATORANDPWDISCRIMINATORHIGH-SIDECMOSLDMOS(LEVELSHIFTERS)p+n+n+p-wellpn-pCb-subp+pn+n+n+pn-Cd-subp+p-COM(e.g.,IRS211x)havethetransitionthresholdproportionaltothelogicsupplyVDD(3to20V)andSchmitttriggerbufferswithhysteresisequalto10%ofVDDtoacceptinputswithlongrisetime.OtherMGDs(e.g.,IRS210x,IRS212x,andIRS213xdevices)haveafixedtransitionfromlogic0tologic1between1.5Vto2V.SomeMGDscandriveonlyonehigh-sidepowerdevice(e.g.,IRS2117,IRS2127,andIRS21851).Otherscandriveonehigh-sideandonelow-sidepowerdevice.Otherscandriveafullthree-phasebridge(e.g.,theIRS213xandIRS263xfamilies).Itgoeswithoutsayingthatanyhigh-sidedrivercanalsodrivealow-sidedevice.ThoseMGDswithtwogatedrivechannelcanhavedual,henceindependent,inputcommandsorasingleinputcommandwithcomplementarydriveandpredetermineddeadtime.ThoseapplicationsthatrequireaminimumdeadtimeshoulduseMGDswithintegrateddeadtime(half-bridgedriver)orahigh-andlow-sidedriverincombinationwithpassivecomponentstoprovidetheneededdeadtime,asshown