Thyristor Family

2. Objectives…Objectives…Objectives…Objectives…Objectives…Objectives…Objectives…Objectives…
PUTPUT (Programmable(Programmable UnijuncionUnijuncion Transistor)Transistor)..
SUSSUS (Silicon(Silicon UnilateralUnilateral Switch)Switch)..
SCSSCS (Silicon(Silicon ControlledControlled Switch)Switch)..
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SCSSCS (Silicon(Silicon ControlledControlled Switch)Switch)..
RCTRCT (Reverse(Reverse ConductingConducting Thyristor)Thyristor)..
TRIACTRIAC
ASCRASCR (Asymmetrical(Asymmetrical Thyristor)Thyristor)..

3. PUTPUTPUTPUTPUTPUTPUTPUT
ProgrammableProgrammableProgrammableProgrammableProgrammableProgrammableProgrammableProgrammable UnijunctionUnijunctionUnijunctionUnijunctionUnijunctionUnijunctionUnijunctionUnijunction
TransistorTransistorTransistorTransistorTransistorTransistorTransistorTransistor
J1J1
J2J2
J3J3
TransistorTransistorTransistorTransistorTransistorTransistorTransistorTransistor
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4. PUT (ProgrammablePUT (ProgrammablePUT (ProgrammablePUT (ProgrammablePUT (ProgrammablePUT (ProgrammablePUT (ProgrammablePUT (Programmable UnijunctionUnijunctionUnijunctionUnijunctionUnijunctionUnijunctionUnijunctionUnijunction Transistor)Transistor)Transistor)Transistor)Transistor)Transistor)Transistor)Transistor)
ItIt isis aa fourfour--layerlayer PP--NN--PP--NN solidsolid--statestate devicedevice withwith aa gategate
connectedconnected directlydirectly toto thethe sandwichedsandwiched NN--typetype layerlayer..
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J1J1
J2J2
J3J3

5. PUT (ProgrammablePUT (ProgrammablePUT (ProgrammablePUT (ProgrammablePUT (ProgrammablePUT (ProgrammablePUT (ProgrammablePUT (Programmable UnijunctionUnijunctionUnijunctionUnijunctionUnijunctionUnijunctionUnijunctionUnijunction Transistor)Transistor)Transistor)Transistor)Transistor)Transistor)Transistor)Transistor)
InIn aa PUT,PUT, GateGate isis alwaysalways biasedbiased positivepositive withwith respectrespect toto
CathodeCathode..
WhenWhen anodeanode voltagevoltage exceedsexceeds thethe gategate voltagevoltage byby aboutabout
00..77 v,v, thethe junctionjunction JJ11 getsgets forwardforward biasedbiased andand PUTPUT turnsturns
onon..
WhenWhen anodeanode voltagevoltage becomesbecomes lessless thanthan thethe gategate voltage,voltage,
PUTPUT isis turnedturned offoff..
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TheThe anodeanode--toto--cathodecathode voltagevoltage VVAKAK thenthen dropsdrops toto aa lowlow
level,level, andand thethe devicedevice conductsconducts heavilyheavily untiluntil thethe inputinput
voltagevoltage becomebecome tootoo lowlow toto sustainsustain conductionconduction
ThisThis actionaction stimulatesstimulates thethe performanceperformance ofof aa UJTUJT.. TheThe
anodeanode ofof thethe devicedevice actsacts asas thethe emitteremitter ofof UJTUJT..

6. PUT (ProgrammablePUT (ProgrammablePUT (ProgrammablePUT (ProgrammablePUT (ProgrammablePUT (ProgrammablePUT (ProgrammablePUT (Programmable UnijunctionUnijunctionUnijunctionUnijunctionUnijunctionUnijunctionUnijunctionUnijunction Transistor)Transistor)Transistor)Transistor)Transistor)Transistor)Transistor)Transistor)
VV--II CharacteristicCharacteristic ofof PUTPUT
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7. PUT (ProgrammablePUT (ProgrammablePUT (ProgrammablePUT (ProgrammablePUT (ProgrammablePUT (ProgrammablePUT (ProgrammablePUT (Programmable UnijunctionUnijunctionUnijunctionUnijunctionUnijunctionUnijunctionUnijunctionUnijunction Transistor)Transistor)Transistor)Transistor)Transistor)Transistor)Transistor)Transistor)
TheThe PUTPUT cancan bebe “programmed”“programmed” toto turnturn onon atat aa certaincertain
voltagevoltage byby anan externalexternal voltagevoltage dividerdivider.. ThisThis yieldsyields aa curvecurve
similarsimilar toto aa UJTUJT..
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8. PUT (ProgrammablePUT (ProgrammablePUT (ProgrammablePUT (ProgrammablePUT (ProgrammablePUT (ProgrammablePUT (ProgrammablePUT (Programmable UnijunctionUnijunctionUnijunctionUnijunctionUnijunctionUnijunctionUnijunctionUnijunction Transistor)Transistor)Transistor)Transistor)Transistor)Transistor)Transistor)Transistor)
9/12/2013 Mahesh J. vadhavaniya 7

9. PUT (ProgrammablePUT (ProgrammablePUT (ProgrammablePUT (ProgrammablePUT (ProgrammablePUT (ProgrammablePUT (ProgrammablePUT (Programmable UnijunctionUnijunctionUnijunctionUnijunctionUnijunctionUnijunctionUnijunctionUnijunction Transistor)Transistor)Transistor)Transistor)Transistor)Transistor)Transistor)Transistor)
TheThe termterm “programmable”“programmable” isis appliedapplied becausebecause thethe interinter
basebase resistanceresistance RRBBBB,, thethe intrinsicintrinsic standstand--offoff ratioratio ȠȠ andand peakpeak--
pointpoint voltagevoltage VVPP,, asas defineddefined inin UJTUJT cancan bebe programmedprogrammed toto
anyany desireddesired valuesvalues throughthrough externalexternal resistorsresistors RRBB11 andand RRBB22
andand thethe supplysupply voltagevoltage VVBBBB..
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FromFrom figurefigure wewe seesee thatthat byby voltagevoltage dividerdivider rulerule whenwhen IIGG==00
GG B1B1 B1B1 B2B2 BBBB BBBBVGG = (RB1B1 / RB1B1 + RB2B2 ) VBBBB = Ƞ VBBBB
andand thethe supplysupply voltagevoltage VVBBBB..

10. PUT (ProgrammablePUT (ProgrammablePUT (ProgrammablePUT (ProgrammablePUT (ProgrammablePUT (ProgrammablePUT (ProgrammablePUT (Programmable UnijunctionUnijunctionUnijunctionUnijunctionUnijunctionUnijunctionUnijunctionUnijunction Transistor)Transistor)Transistor)Transistor)Transistor)Transistor)Transistor)Transistor)
ItsIts largestlargest ratingrating isis aboutabout 200200 vv andand 11 AA..
PUTPUT isis mainlymainly usedused inin TimeTime--delay,delay, logiclogic andand SCRSCR triggertrigger
circuitscircuits..
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11. PUT (ProgrammablePUT (ProgrammablePUT (ProgrammablePUT (ProgrammablePUT (ProgrammablePUT (ProgrammablePUT (ProgrammablePUT (Programmable UnijunctionUnijunctionUnijunctionUnijunctionUnijunctionUnijunctionUnijunctionUnijunction Transistor)Transistor)Transistor)Transistor)Transistor)Transistor)Transistor)Transistor)
Load
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SCR

12. SUSSUSSUSSUSSUSSUSSUSSUS
Silicon Unilateral SwitchSilicon Unilateral SwitchSilicon Unilateral SwitchSilicon Unilateral SwitchSilicon Unilateral SwitchSilicon Unilateral SwitchSilicon Unilateral SwitchSilicon Unilateral Switch
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13. SUS (Silicon Unilateral Switch)SUS (Silicon Unilateral Switch)SUS (Silicon Unilateral Switch)SUS (Silicon Unilateral Switch)SUS (Silicon Unilateral Switch)SUS (Silicon Unilateral Switch)SUS (Silicon Unilateral Switch)SUS (Silicon Unilateral Switch)
AA SUSSUS isis similarsimilar toto aa PUTPUT butbut withwith anan inin--builtbuilt lowlow--
voltagevoltage avalancheavalanche diodediode betweenbetween gategate andand cathodecathode..
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14. BecauseBecause ofof thethe presencepresence ofof diode,diode, SUSSUS turnsturns onon forfor aa
fixedfixed anodeanode--toto--cathodecathode voltagevoltage..
SCR’sSCR’s triggertrigger voltagevoltage and/orand/or currentcurrent varyvary widelywidely withwith
changeschanges inin ambientambient temperaturetemperature..
SUS (Silicon Unilateral Switch)SUS (Silicon Unilateral Switch)SUS (Silicon Unilateral Switch)SUS (Silicon Unilateral Switch)SUS (Silicon Unilateral Switch)SUS (Silicon Unilateral Switch)SUS (Silicon Unilateral Switch)SUS (Silicon Unilateral Switch)
changeschanges inin ambientambient temperaturetemperature..
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ItsIts largestlargest ratingsratings areare aboutabout 2020 vv andand 00..55 AA..
SUSSUS isis mainlymainly usedused inin Timing,Timing, logiclogic andand triggertrigger circuitscircuits..

15. SUS (Silicon Unilateral Switch)SUS (Silicon Unilateral Switch)SUS (Silicon Unilateral Switch)SUS (Silicon Unilateral Switch)SUS (Silicon Unilateral Switch)SUS (Silicon Unilateral Switch)SUS (Silicon Unilateral Switch)SUS (Silicon Unilateral Switch)
9/12/2013 Mahesh J. vadhavaniya 14

16. SCSSCSSCSSCSSCSSCSSCSSCS
Silicon Controlled SwitchSilicon Controlled SwitchSilicon Controlled SwitchSilicon Controlled SwitchSilicon Controlled SwitchSilicon Controlled SwitchSilicon Controlled SwitchSilicon Controlled Switch
J1J1
J2J2
J3J3
16
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17. SCS (Silicon Controlled Switch)SCS (Silicon Controlled Switch)SCS (Silicon Controlled Switch)SCS (Silicon Controlled Switch)SCS (Silicon Controlled Switch)SCS (Silicon Controlled Switch)SCS (Silicon Controlled Switch)SCS (Silicon Controlled Switch)
AnAn SCSSCS isis aa tetrodetetrode.. ItIt isis aa fourfour electrodeelectrode thyristorthyristor..
ItIt hashas twotwo gates,gates, oneone anodeanode gategate (AG)(AG) likelike aa PUTPUT andand
anotheranother cathodecathode gategate (KG)(KG) likelike anan SCRSCR..
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AnAn SCSSCS isis aa fourfour layer,layer, fourfour terminalterminal pnpnpnpn devicedevice withwith
anodeanode A,A, cathodecathode K,K, anodeanode gategate AGAG andand cathodecathode gategate KGKG..
AnAn SCSSCS cancan bebe turnedturned onon byby eithereither gategate..

18. SCS (Silicon Controlled Switch)SCS (Silicon Controlled Switch)SCS (Silicon Controlled Switch)SCS (Silicon Controlled Switch)SCS (Silicon Controlled Switch)SCS (Silicon Controlled Switch)SCS (Silicon Controlled Switch)SCS (Silicon Controlled Switch)
J1J1
9/12/2013 Mahesh J. vadhavaniya 17
J2J2
J3J3

19. SCS (Silicon Controlled Switch)SCS (Silicon Controlled Switch)SCS (Silicon Controlled Switch)SCS (Silicon Controlled Switch)SCS (Silicon Controlled Switch)SCS (Silicon Controlled Switch)SCS (Silicon Controlled Switch)SCS (Silicon Controlled Switch)
WhenWhen aa negativenegative pulsepulse isis appliedapplied toto gategate AG,AG, junctionjunction JJ11
isis forwardforward biasedbiased andand SCSSCS isis turnedturned onon..
AA positivepositive pulsepulse atat AGAG willwill reversereverse biasbias junctionjunction JJ11 andand
turnsturns offoff thethe SCSSCS..
WhenWhen aa positivepositive pulsepulse isis appliedapplied toto gategate KG,KG, junctionjunction JJ22
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WhenWhen aa positivepositive pulsepulse isis appliedapplied toto gategate KG,KG, junctionjunction JJ22
isis forwardforward biasedbiased andand SCSSCS isis turnedturned onon.. (Just(Just likelike anan SCR)SCR)
AA negativenegative pulsepulse atat KGKG willwill reversereverse biasbias junctionjunction JJ22 andand
turnsturns offoff thethe SCSSCS.. (Just(Just likelike aa GG..TT..OO..))
ItsIts ratingsratings areare aboutabout 100100 vv andand 200200 mAmA..
ItIt cancan bebe operatedoperated likelike anan OROR gategate..

20. SCS (Silicon Controlled Switch)SCS (Silicon Controlled Switch)SCS (Silicon Controlled Switch)SCS (Silicon Controlled Switch)SCS (Silicon Controlled Switch)SCS (Silicon Controlled Switch)SCS (Silicon Controlled Switch)SCS (Silicon Controlled Switch)
ApplicationsApplications
Timing,Timing, logiclogic andand triggeringtriggering circuitscircuits
PulsePulse generatorsgenerators
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PulsePulse generatorsgenerators
VoltageVoltage sensorssensors
OscillatorsOscillators etcetc..

21. SCS (Silicon Controlled Switch)SCS (Silicon Controlled Switch)SCS (Silicon Controlled Switch)SCS (Silicon Controlled Switch)SCS (Silicon Controlled Switch)SCS (Silicon Controlled Switch)SCS (Silicon Controlled Switch)SCS (Silicon Controlled Switch)
9/12/2013 Mahesh J. vadhavaniya 20

22. TRIACTRIACTRIACTRIACTRIACTRIACTRIACTRIAC
TRIodeTRIodeTRIodeTRIodeTRIodeTRIodeTRIodeTRIode and ACand ACand ACand ACand ACand ACand ACand AC
9/12/2013 Mahesh J. vadhavaniya 21

23. TRIACTRIACTRIACTRIACTRIACTRIACTRIACTRIAC
AnAn SCRSCR isis aa unidirectionalunidirectional devicedevice asas itit cancan conductconduct onlyonly
fromfrom anodeanode toto cathodecathode onlyonly andand notnot fromfrom cathodecathode toto
anodeanode..
AA TriacTriac cancan conductconduct inin bothboth thethe directionsdirections..
AA TriacTriac isis aa bidirectionalbidirectional thyristorthyristor withwith threethree terminalsterminals..
9/12/2013 Mahesh J. vadhavaniya 22
ItIt isis usedused extensivelyextensively forfor thethe controlcontrol ofof powerpower inin acac
circuitscircuits..
WhenWhen inin operation,operation, TriacTriac isis equivalentequivalent toto twotwo SCRsSCRs
connectedconnected inin antiparallelantiparallel..
AA TriacTriac isis aa bidirectionalbidirectional thyristorthyristor withwith threethree terminalsterminals..

24. TRIACTRIACTRIACTRIACTRIACTRIACTRIACTRIAC
TriacTriac isis bidirectionalbidirectional devicedevice (can(can conductconduct currentcurrent inin
eithereither direction)direction) ,, whilewhile SCRSCR isis unidirectionalunidirectional devicesdevices (can(can
conductconduct currentcurrent onlyonly inin oneone way)way)..
DifferencesDifferences betweenbetween TriacTriac andand SCRSCR
9/12/2013 Mahesh J. vadhavaniya 23
TRIACsTRIACs cancan bebe triggeredtriggered byby eithereither aa positivepositive oror aa
negativenegative currentcurrent appliedapplied toto itsits gategate electrodeelectrode whilewhile SCRSCR
cancan onlyonly triggeredtriggered whenwhen aa positivepositive currentcurrent applyapply toto thethe
gategate terminalterminal
ForceForce commutationcommutation byby reversedreversed biasingbiasing cannotcannot bebe
employedemployed..

25. ComparisonComparisonComparisonComparisonComparisonComparisonComparisonComparison between SCR and TRIACbetween SCR and TRIACbetween SCR and TRIACbetween SCR and TRIACbetween SCR and TRIACbetween SCR and TRIACbetween SCR and TRIACbetween SCR and TRIAC
9/12/2013 Mahesh J. vadhavaniya 24

26. TRIACTRIACTRIACTRIACTRIACTRIACTRIACTRIAC
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27. TRIACTRIACTRIACTRIACTRIACTRIACTRIACTRIAC
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28. TRIACTRIACTRIACTRIACTRIACTRIACTRIACTRIAC
AsAs thethe triactriac cancan conductconduct inin bothboth thethe directions,directions, thethe termsterms
anodeanode andand cathodecathode areare notnot applicableapplicable toto triactriac..
ItsIts threethree terminalsterminals areare usuallyusually designateddesignated asas MTMT11 (main(main
terminalterminal 11),), MTMT22 andand thethe gategate GG..
WithWith nono signalsignal toto gate,gate, thethe triactriac willwill blockblock bothboth halfhalf
cyclescycles ofof thethe acac appliedapplied voltagevoltage inin casecase peakpeak valuevalue ofof thisthis
9/12/2013 Mahesh J. vadhavaniya 27
TheThe triactriac cancan bebe turnedturned onon inin eacheach halfhalf cyclecycle ofof thethe
appliedapplied voltagevoltage byby applyingapplying aa positivepositive oror negativenegative voltagevoltage
toto thethe gategate withwith respectrespect toto terminalterminal MTMT11..
MTMT11 isis takentaken asas thethe pointpoint forfor measuringmeasuring thethe voltagevoltage andand
currentcurrent isis measuredmeasured atat thethe gategate andand MTMT22 terminalsterminals..
cyclescycles ofof thethe acac appliedapplied voltagevoltage inin casecase peakpeak valuevalue ofof thisthis
voltagevoltage isis lessless thanthan thethe breakdownbreakdown voltagevoltage ofof VVBB0101 andand VVBB0202
ofof thethe triactriac..

29. TRIACTRIACTRIACTRIACTRIACTRIACTRIACTRIAC
9/12/2013 Mahesh J. vadhavaniya 28

30. TRIACTRIACTRIACTRIACTRIACTRIACTRIACTRIAC
9/12/2013 Mahesh J. vadhavaniya 29

31. TRIACTRIACTRIACTRIACTRIACTRIACTRIACTRIAC –––––––– Characteristics…Characteristics…Characteristics…Characteristics…Characteristics…Characteristics…Characteristics…Characteristics…
ItIt cancan bebe seenseen thatthat itit isis anan extensionextension IVIV characteristiccharacteristic ofof
SCRSCR..
TheThe characteristiccharacteristic areare symmetricalsymmetrical aboutabout thethe firstfirst andand
thethe thirdthird quadrantsquadrants..
9/12/2013 Mahesh J. vadhavaniya 30
ItIt showsshows thethe gategate cancan bebe usedused toto controlcontrol thethe mainmain currentcurrent
flowflow inin eithereither directiondirection..
TRIACTRIAC willwill bebe continuouslycontinuously ONON untiluntil thethe currentcurrent throughthrough
AA11 toto AA22 areare belowbelow thethe holdingholding currentcurrent..
thethe thirdthird quadrantsquadrants..

32. TRIACTRIACTRIACTRIACTRIACTRIACTRIACTRIAC –––––––– Triggering Method…Triggering Method…Triggering Method…Triggering Method…Triggering Method…Triggering Method…Triggering Method…Triggering Method…
TheThe phasephase shiftingshifting methodmethod ofof firingfiring TRIACTRIAC isis similarsimilar toto
thethe firingfiring ofof thethe SCRSCR..
TheThe majormajor differencedifference inin thethe waveformwaveform isis therethere isis aa
negativenegative portionportion inin thethe waveformwaveform ofof TRIACTRIAC..
ItIt showsshows thethe gategate cancan bebe usedused toto controlcontrol thethe mainmain currentcurrent
flowflow inin eithereither directiondirection..
9/12/2013 Mahesh J. vadhavaniya 31

33. Turning on the TRIAC…Turning on the TRIAC…Turning on the TRIAC…Turning on the TRIAC…Turning on the TRIAC…Turning on the TRIAC…Turning on the TRIAC…Turning on the TRIAC…
9/12/2013 Mahesh J. vadhavaniya 32

34. TRIACTRIACTRIACTRIACTRIACTRIACTRIACTRIAC –––––––– Turn ON process…Turn ON process…Turn ON process…Turn ON process…Turn ON process…Turn ON process…Turn ON process…Turn ON process…
N2N2
N2N2
P2P2
MT1MT1
GG
N4N4
P1P1
N1P2P2
N4N4
N1
P2P2
N3N3
N3N3
MT2MT2
9/12/2013 Mahesh J. vadhavaniya 33

35. TRIACTRIACTRIACTRIACTRIACTRIACTRIACTRIAC –––––––– Turn ON process…Turn ON process…Turn ON process…Turn ON process…Turn ON process…Turn ON process…Turn ON process…Turn ON process…
((ii)) MTMT22 isis positivepositive andand gategate currentcurrent isis positivepositive
WhenWhen MTMT22 isis positivepositive withwith respectrespect toto MTMT11,, junctionjunction PP11 NN11,, PP22 NN22 areare
forwardforward biasedbiased butbut junctionjunction NN11 PP22 isis revrserevrse biasedbiased..
WhenWhen gategate terminalterminal isis positivepositive withwith respectrespect toto MTMT11,, gategate currentcurrent
flowsflows mainlymainly throughthrough PP22 NN22 junctionjunction likelike anan ordinaryordinary SCRSCR..
WhenWhen gategate currentcurrent hashas injectedinjected sufficientsufficient chargecharge intointo PP22 layer,layer,
reversereverse biasbias junctionjunction NN11 PP22 breaksbreaks downdown justjust asas inin aa normalnormal SCRSCR
9/12/2013 Mahesh J. vadhavaniya 34
TriacTriac startsstarts conductingconducting throughthrough PP11 NN11 PP22 NN22 layerslayers..
reversereverse biasbias junctionjunction NN11 PP22 breaksbreaks downdown justjust asas inin aa normalnormal SCRSCR
ThisThis impliesimplies whenwhen MTMT22 andand gategate areare positivepositive withwith respectrespect toto MTMT11,,
traictraic turnsturns onon likelike aa conventionalconventional thyristorthyristor..
InIn thisthis conditioncondition triactriac operatesoperates inin thethe firstfirst quadrantquadrant..
TheThe devicedevice isis moremore sensitivesensitive inin thisthis modemode..
ItIt isis ecommendedecommended methodmethod ofof triggeringtriggering ifif thethe conductionconduction isis requiredrequired
inin thethe firstfirst quadrantquadrant..

36. TRIACTRIACTRIACTRIACTRIACTRIACTRIACTRIAC –––––––– Turn ON process…Turn ON process…Turn ON process…Turn ON process…Turn ON process…Turn ON process…Turn ON process…Turn ON process…
(ii)(ii) MTMT22 isis positivepositive butbut gategate currentcurrent isis negativenegative
TriacTriac startsstarts conductingconducting throughthrough PP11 NN11 PP22 NN33 layerslayers initiallyinitially..
WhenWhen gategate terminalterminal isis negativenegative withwith respectrespect toto MTMT11,, gategate currentcurrent
flowsflows throughthrough PP22 NN33 junctionjunction andand reversereverse biasedbiased junctionjunction NN11 PP22 isis
forwardforward biasedbiased asas inin aa normalnormal thyristorthyristor..
WithWith thethe conductionconduction ofof PP11 NN11 PP22 NN33,, thethe voltagevoltage dropdrop acrossacross thisthis
pathpath fallsfalls butbut potentialpotential ofof layerlayer betweenbetween PP22 NN33 risesrises towardstowards thethe anodeanode
9/12/2013 Mahesh J. vadhavaniya 35
pathpath fallsfalls butbut potentialpotential ofof layerlayer betweenbetween PP22 NN33 risesrises towardstowards thethe anodeanode
potentialpotential ofof MTMT22..
AsAs thethe rightright handhand portionportion ofof PP22 isis clampedclamped atat thethe cathodecathode potentialpotential ofof
MTMT11,, aa potentialpotential gradientgradient existsexists acrossacross layerlayer PP22..
PP22’s’s leftleft handhand regionregion beingbeing atat higherhigher potentialpotential thanthan itsits rightright handhand
regionregion..
TheThe currentcurrent isis establishedestablished inin layerlayer PP22 fromfrom leftleft toto rightright..
ThisThis currentcurrent isis similarsimilar toto conventionalconventional gategate currentcurrent ofof anan SCRSCR..

37. TRIACTRIACTRIACTRIACTRIACTRIACTRIACTRIAC –––––––– Turn ON process…Turn ON process…Turn ON process…Turn ON process…Turn ON process…Turn ON process…Turn ON process…Turn ON process…
(ii)(ii) MTMT22 isis positivepositive butbut gategate currentcurrent isis negativenegative
TheThe devicedevice structurestructure PP11 NN11 PP22 NN33 maymay bebe regardedregarded asas pilotpilot SCRSCR andand
thethe structurestructure PP11 NN11 PP22 NN22 asas thethe mainmain SCRSCR..
AsAs aa result,result, rightright handhand partpart ofof triactriac consisitingconsisiting ofof mainmain structurestructure PP11
NN11 PP22 NN22 beginsbegins toto conductconduct
ItIt cancan bebe statedstated thatthat anodeanode currentcurrent ofof pilotpilot SCRSCR servesserves asas thethe gategate
currentcurrent ofof thethe mainmain SCRSCR..
9/12/2013 Mahesh J. vadhavaniya 36
currentcurrent ofof thethe mainmain SCRSCR..
ThisThis isis lessless sensitivesensitive andand thereforetherefore moremore gategate currentcurrent isis requiredrequired..
TheThe gategate currentcurrent IgIg forwardforward biasesbiases PP22 NN22 junctionjunction
LayerLayer NN22 injectsinjects electronselectrons intointo PP22 layerlayer..
AsAs aa resultresult thethe reversereverse biasedbiased junctionjunction NN11 PP11 breaksbreaks downdown asas inin aa
conventionalconventional thyristorthyristor..
(iii)(iii) MTMT22 isis negativenegative butbut gategate currentcurrent isis positivepositive

38. TRIACTRIACTRIACTRIACTRIACTRIACTRIACTRIAC –––––––– Turn ON process…Turn ON process…Turn ON process…Turn ON process…Turn ON process…Turn ON process…Turn ON process…Turn ON process…
AsAs usualusual thethe currentcurrent afterafter turnturn onon isis limitedlimited byby thethe externalexternal loadload..
EventuallyEventually thethe structurestructure PP22 NN11 PP11 NN44 isis completelycompletely turnedturned onon..
AsAs thethe triactriac isis turnedturned onon byby remoteremote gategate NN22,, thethe devicedevice isis lessless
sensitivesensitive inin thethe thirdthird quadrantquadrant withwith positivepositive gategate currentcurrent..
(iii)(iii) MTMT22 isis negativenegative butbut gategate currentcurrent isis positivepositive
(iv)(iv) BothBoth MTMT22 andand gategate currentcurrent areare negativenegative
9/12/2013 Mahesh J. vadhavaniya 37
InIn thisthis modemode NN33 actsacts asas aa remoteremote gategate..
TheThe gategate currentcurrent IgIg flowsflows fromfrom PP22 toto NN33 asas inin aa normalnormal thyristorthyristor..
ThoughThough thethe triactriac isis turnedturned onon byby remoteremote gategate NN33 inin thirdthird quadrant,quadrant,
thethe devicedevice isis moremore sensitivesensitive underunder thisthis conditioncondition comparedcompared withwith turnturn
onon actionaction ofof casecase (iii)(iii)
ReverseReverse biasedbiased junctionjunction NN11 PP11 isis brokenbroken andand finallyfinally thethe structurestructure PP22
NN11 PP11 NN44 isis turnedturned onon completelycompletely..
(iv)(iv) BothBoth MTMT22 andand gategate currentcurrent areare negativenegative

39. TRIACTRIACTRIACTRIACTRIACTRIACTRIACTRIAC
TheThe sensitivitysensitivity ofof thethe triactriac isis greatestgreatest inin thethe firstfirst
quadrantquadrant whenwhen turnedturned onon withwith positivepositive gategate currentcurrent andand
alsoalso inin thethe thirdthird quadrantquadrant whenwhen turnedturned onon withwith negativenegative
gategate currentcurrent..
ConclusionConclusion ::
9/12/2013 Mahesh J. vadhavaniya 38
SoSo thethe triactriac isis rarelyrarely operatedoperated inin firstfirst quadrantquadrant withwith
negativenegative gategate currentcurrent andand inin thethe thirdthird quadrantquadrant withwith
positivepositive gategate currentcurrent..
TheThe sensitivitysensitivity ofof thethe triactriac isis lowlow inin thethe firstfirst quadrantquadrant
whenwhen turnedturned onon withwith negativenegative gategate currentcurrent andand alsoalso inin thethe
thirdthird quadrantquadrant whenwhen turnedturned onon withwith positivepositive gategate currentcurrent..

40. TRIACTRIACTRIACTRIACTRIACTRIACTRIACTRIAC –––––––– Turn ON process…Turn ON process…Turn ON process…Turn ON process…Turn ON process…Turn ON process…Turn ON process…Turn ON process…
AsAs thethe twotwo conductingconducting pathspaths fromfrom MTMT11 toto MTMT22 oror fromfrom
MTMT22 toto MTMT11 interactinteract withwith eacheach otherother inin thethe structurestructure ofof thethe
triactriac,, theirtheir voltage,voltage, currentcurrent andand frequencyfrequency ratingsratings areare
muchmuch lowerlower asas comparedcompared withwith conventionalconventional thyristorsthyristors..
TriacsTriacs areare availableavailable withwith thethe ratingsratings 12001200 vv andand 300300 AA
9/12/2013 Mahesh J. vadhavaniya 39
TriacsTriacs areare extensivelyextensively usedused inin residentialresidential lamplamp dimmers,dimmers,
heatheat controlcontrol andand forfor thethe speedspeed controlcontrol ofof smallsmall singlesingle phasephase
seriesseries andand inductioninduction motorsmotors..
TriacsTriacs areare availableavailable withwith thethe ratingsratings 12001200 vv andand 300300 AA
((rmsrms))..

41. TRIACTRIACTRIACTRIACTRIACTRIACTRIACTRIAC –––––––– Turn ON process…Turn ON process…Turn ON process…Turn ON process…Turn ON process…Turn ON process…Turn ON process…Turn ON process…
AA triactriac maymay somesome timestimes operateoperate inin thethe rectifierrectifier mode,mode,
duedue toto…………
(a)(a) ForFor aa givengiven valuevalue ofof positivepositive gategate current,current, aa triactriac maymay
turnturn onon withwith MTMT22 positivepositive inin firstfirst quadrantquadrant butbut maymay failfail toto
turnturn onon withwith MTMT22 negativenegative..
9/12/2013 Mahesh J. vadhavaniya 40
(b)(b) WithWith constantconstant negativenegative gategate current,current, aa triactriac maymay turnturn
onon withwith MTMT22 negativenegative inin thirdthird quadrantquadrant butbut maymay failfail toto
turnturn onon withwith MTMT22 positivepositive..
turnturn onon withwith MTMT22 negativenegative..
TheThe rectifierrectifier modemode cancan bebe overcomeovercome byby increasingincreasing thethe
valuevalue ofof gategate currentcurrent..

42. ASCRASCRASCRASCRASCRASCRASCRASCR
Asymmetrical SCRAsymmetrical SCRAsymmetrical SCRAsymmetrical SCRAsymmetrical SCRAsymmetrical SCRAsymmetrical SCRAsymmetrical SCRAsymmetrical SCRAsymmetrical SCRAsymmetrical SCRAsymmetrical SCRAsymmetrical SCRAsymmetrical SCRAsymmetrical SCRAsymmetrical SCR
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43. ASCR ( Asymmetrical SCR )ASCR ( Asymmetrical SCR )ASCR ( Asymmetrical SCR )ASCR ( Asymmetrical SCR )ASCR ( Asymmetrical SCR )ASCR ( Asymmetrical SCR )ASCR ( Asymmetrical SCR )ASCR ( Asymmetrical SCR )
AnAn ASCRASCR isis speciallyspecially fabricatedfabricated toto havehave limitedlimited reversereverse
voltagevoltage capability,capability, whichwhich permitspermits aa reductionreduction inin turnturn--onon
time,time, turnturn--offoff timetime andand onon--statestate voltagevoltage dropdrop inin ASCRASCR..
AA typicaltypical ASCRASCR maymay havehave reversereverse blockingblocking capabilitycapability ofof
2020 toto 3030 VV andand forwardforward blockingblocking voltagevoltage ofof 400400 toto 20002000 VV..
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FastFast turnturn--offoff ASCRsASCRs minimizeminimize thethe size,size, weightweight andand costcost ofof
commutatingcommutating componentscomponents andand permitpermit highhigh frequencyfrequency
operationoperation (( 2020 KHzKHz oror moremore )) withwith improvedimproved efficiencyefficiency..
2020 toto 3030 VV andand forwardforward blockingblocking voltagevoltage ofof 400400 toto 20002000 VV..
ASCRsASCRs withwith turnturn--offoff timetime halfhalf ofof thatthat ofof similarsimilar ratesrates
conventionalconventional SCRsSCRs havehave beenbeen developeddeveloped..

44. RCTRCTRCTRCTRCTRCTRCTRCT
Reverse ConductingReverse ConductingReverse ConductingReverse ConductingReverse ConductingReverse ConductingReverse ConductingReverse ConductingReverse ConductingReverse ConductingReverse ConductingReverse ConductingReverse ConductingReverse ConductingReverse ConductingReverse Conducting
ThyristorThyristorThyristorThyristorThyristorThyristorThyristorThyristor
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45. RCT ( Reverse Conducting Thyristor )RCT ( Reverse Conducting Thyristor )RCT ( Reverse Conducting Thyristor )RCT ( Reverse Conducting Thyristor )RCT ( Reverse Conducting Thyristor )RCT ( Reverse Conducting Thyristor )RCT ( Reverse Conducting Thyristor )RCT ( Reverse Conducting Thyristor )
RCTRCT isis aa specialspecial casecase ASCRASCR withwith aa monolithicallymonolithically
integratedintegrated antiparallelantiparallel diodediode onon thethe samesame siliconsilicon chipchip..
ThisThis constructionconstruction reducesreduces toto zerozero thethe reversereverse blockingblocking
capabilitycapability ofof RCTRCT..
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capabilitycapability ofof RCTRCT..
AA currentcurrent pulsepulse throughthrough thethe diodediode partpart ofof thethe chipchip turnsturns
offoff RCTRCT..
TheThe arrangementarrangement ofof ASCRASCR andand diodediode inin aa singlesingle devicedevice
reducesreduces thethe heatheat sinksink sizesize andand leadsleads toto compactnesscompactness ofof thethe
converterconverter..

46. RCT ( Reverse Conducting Thyristor )RCT ( Reverse Conducting Thyristor )RCT ( Reverse Conducting Thyristor )RCT ( Reverse Conducting Thyristor )RCT ( Reverse Conducting Thyristor )RCT ( Reverse Conducting Thyristor )RCT ( Reverse Conducting Thyristor )RCT ( Reverse Conducting Thyristor )
TheThe undesirableundesirable straystray looploop inductanceinductance betweenbetween ASCRASCR
andand diodediode isis alsoalso eliminatedeliminated andand unwantedunwanted reversereverse voltagevoltage
transientstransients acrossacross ASCRASCR areare avoidedavoided....
ThisThis leadsleads toto betterbetter turnturn offoff behaviourbehaviour ofof RCTRCT..
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ThisThis leadsleads toto betterbetter turnturn offoff behaviourbehaviour ofof RCTRCT..
RCTsRCTs withwith 20002000 VV andand 500500 AA ratingsratings areare availableavailable..
ForFor highhigh performanceperformance inverterinverter andand chopperchopper circuits,circuits,
RCTsRCTs cancan nownow bebe tailortailor--mademade..

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