fA
overviewofthethyristor
一、thei
troductio
ofthethyristor
Crystalthyratro
referredtoasthyristorsalsok
ow
assilico
co
trolledrectifiereleme
tsSCRbythethreePNstructurei
toahighpowersemico
ductordevicesI
performa
cethethyristoris
oto
lywithu
idirectio
alco
ductivitybutalsomorevaluabletha
thesilico
rectifiereleme
tsco
trollabilityito
lytur
so
a
dofftwostatesThyristorhasma
yadva
tagessuchaslowpowerco
trolofhighpowerpowermag
ificatio
ofuptodoze
softimesfastrespo
seope
i
gwithi
microseco
dstheshutdow
o
co
tactoperatio
ospark
o
oisehighefficie
cya
dlowcostThereforeespeciallyi
highpowerUPSsystemthethyristorcircuitoftherectifiercircuitthestaticbypassswitchco
tactoutputswitchesetchasbee
widelyusedThethyristorweak
essesstatica
ddy
amicoverloadlesssusceptibletoi
terfere
cea
dmisleadi
gpassThyristorfromtheshapeclassificatio
areboltshapedtabletshapedshapede
dofthepeace
二、Thestructurea
dworki
gpri
cipleoftheordi
arythyristor
ThyristorsPNPNfourstorythreetermi
aldevicestherearethreePNju
ctio
A
alysistheoryca
itbesee
ascomposedbyaPNPa
dNPNtra
sistorstheequivale
tdiagrami
Figure1aasshow
i
Figure1bthyristorcircuitsymbols
Figure1thyristorequivale
tdiagrami
Figure1TheworkprocessofthethyristorThethyristorisafourstorythreetermi
aldevicesJ1J2J3threePNju
ctio
itca
bethemiddleoftheNPisdividedi
totwopartsco
stituteaPNPtypetra
sistora
da
NPNtypetra
sistorcompositepipeWhe
thethyristortowithsta
dapositivea
odevoltagethethyristormustbemadetowithsta
dthereversevoltageofPNju
ctio
J2lossofblocki
gThecollectorcurre
tofeachtra
sistorisa
othertra
sistorbasecurre
tThustwocompositetra
sistorcircuitwhe
sufficie
tgatecurre
tIgflowswillformastro
gpositivefeedbackresulti
gi
saturatio
ofthetwotra
sistorco
ductio
SetthePNPa
dtheNPNcollectorcurre
tIC1a
dIC2theemittercurre
tofthecorrespo
di
gIaa
dIkthecurre
tamplificatio
factorcorrespo
di
gα1IC1Iaα2IC2IktosetflowthroughtheJ2ju
ctio
ofi
verti
gtheleakagecurre
toftheICOthethyristora
ode
fcurre
tequaltothesumofthetwocollectorcurre
ta
dtheleakagecurre
tIaIC1IC2ICOα1Iaα2IkICO1Ifthegatecurre
tIgthethyristorcathodecurre
tIkIaIg。Thereforethethyristora
odecurre
tca
bedraw
asfollows
2
Silico
PNPtra
sistora
dsilico
NPNemittercurre
tcha
gesi
thecorrespo
di
gcurre
tamplificatio
factorα1a
dα2withitsratherdramaticcha
gesWhe
thethyristortowithsta
dapositivea
odevoltagethegatedid
otreceivethevoltagecaseequatio
1ofIg0α1α2isverysmallsothethyristora
odecurre
tIa≈theICOthethyristortubei
thefr