Cu Tao Va Hoat ng Cua IGBT.
BAI THAO LUN GVHD: Trn ngNhom 5:V Cng Qu.L Hng Quang.Trn Vn Phc.
Vn Quyt.Nguyn Khc Phi.Nguyn Th Phng.Cu Tao Va Hoat ng Cua IGBT.Hinh
dang thc t cua IGBT.
1. Cu Tao Cua IGBT:IGBT la linh kin tich hp gia MOSFET ngo vao
va BJT ngo ra co c linh kin ong ct dong DC iu khin bng ap cc G.IGBT
la s kt hp kha nng ong ct nhanh cua MOSFET va kha nng chiu tai ln
cua BJT.
H1. Cu truc ban dn cua IGBT. . H2. Cu truc tng ng cua IGBT (gm 1
BJT va 1 Mosfet).
H3. S tng ng cua IGBT. H4. Ki hiu cua IGBT.
Theo cu truc ban dn nh hinh H1 thi IGBT rt ging vi mosfet im
khac nhau la co thm lp P ni vi cc C tao thanh cu truc ban dn P-N-P
gia cc E vi C. Nh vy ta co th coi IGBT tng ng vi mt transistor
P-N-P vi vi dong bazo iu khin bi mt mosfet.
2.Nguyn li hoat ng cua IGBT.Theo nh hinh H3 thi di tac ng cua in
ap iu khin UGE > 0 kich ong IGBT, cac hat mang in loai N c keo
vao knh P gn cc G lam giam in tich mach cc P cuaTransistor N-P-N va
lam cho Transistor nay dn in , dn n IGBT se dn in. ngt IGBT ta khoa
in th cp cho cc kich G ngt knh dn P.3.c tinh ong ct cua IGBT. Trn
hnh H3 th hin cu trc tng ng ca IGBT vi Mosfet v mt Tranzitor p-n-p.
K hiu dng qua IGBT gm hai thnh phn: i1 dng qua Mosfet, i2 dng qua
Tranzitor. Phn Mosfet trong IGBT c th kha li nhanh chng nu x ht c
in tch gia G v E, do dng i1= 0, tuy nhin i2 s khng suy gim nhanh
chng c do lng in tch ly trong (tng ngvi bazo ca cu trc p-n-p) ch c
th mt i do qu trnh t trung ha in tch. iu ny xut hin vng dng in ko
di khi kha IGBT.
S mach th hin c tinh ong ct cua IGBT.
5Qua trinh m IGBT.khi in p iu khin vo tng t 0 n gi tr Ug. Trong
thi gian tr khi m Io tn hiu iu khin np in cho t Cgc lm in p gia cc
iu khin v emite tng theo quy lut hm m t 0 n gi tr ngn Uge( 3 n 5v).
Ch bt u t Mosfet trong cu trc ca IGBT mi bt u m ra. Dng in gia
colecto-emite tng theo quy lut tuyn tnh t 0 n dng ti Io trong thi
gian tr.Trong thi gian tr in p gia cc iu khin v emite tng n gi tr
Uge xc nh gi tr dng Io qua colecto. Do diode Do cn ang dn dng ti Io
nn in p Uce vn b gm ln mc in p ngun 1 chiu Udc. Tip theo qu trnh m
din ra theo 2 giai on T1 v T2. Trong sut hai giai on ny in p gia cc
diu khin gi nguyn Uge duy tr dng Io, do dng iu khin hon ton l dng
phng t Cgc. IGBT vn lm vic trong ch tuyn tnh. Trong giai on u din
ra qu trnh kha v phc hi ca diode Do dng phc hi ca diode Do to nn
xung dng trn mc dng Io ca IGBT. in p Uce bt u gim.IGBT chuyn im lm
vic qua vng ch tuyn tnh sang vng bo ha. Giai on 2 tip din qu trnh
gim in tr trong vng thun tr ca colecto dn n in tr colecto-emite v n
gi tr Ron khi bo ha hon tonUce= IoRon.Sau thi gian m Ton khi t Cgc
phng in xong, in p gia cc iu khin v emito tip tc tng theo quy lut
hm m vi hng s thi gian CgcRg n gi tr cui cng Ug.
4. Vung lam vic an toan:Vng lm vic an ton c th hin di dng th
quan h gia in p v gi tr dng in ln nht m phn t c th hot ng c trong
mi ch , khi dn, khi kha, cng nh trong cc qu trnh ng ct. SOA ca IGBT
c biu din hnh di.
hnh u tin biu din khi in p t ln cc iu khin v emitor l dng v hnh
th hai th in p ny l m. Khi in p iu khin dng, SOA c dng hnh ch nht
vi gc hn ch pha trn, bn phi, tng ng vi ch dng in v in p ln. iu ny c
ngha l khi chu k ng ct cng ngn, ng vi tn s lm vic cng cao th kh nng
ng ct cng sut cng suy gim. Khi t in p iu khin m ln cc iu khin v
emitor, SOA li b gii hn vng cng sut ln do tc tng in p qu ln s dn n
xut hin dng in ln a vo vng p ca cc iu khin, tc dng ging nh dng iu
khin lm IGBT m tr li nh tc dng i vi cu trc ca thyristor. Tuy nhin
kh nng chu ng tc tng p IGBT ln hn nhiu so vi cc phn t bn dn cng sut
khc.Gi tr ln nht ca dng cho php collector cho php Icm c chn sao cho
trnh c hin tng cht gi dng, khng kha li c, ging nh thyristor. Hn na,
in p iu khin ln nht Uge cng phi c chn c th gii hn c dng in Ice
trong gii hn ln nht cho php ny trong iu kin s c ngn mch bng cch
chuyn i bt buc t ch bo ha sang ch tuyn tnh. Khi dng Ice c gii hn
khng i, khng ph thuc vo in p Uce lc . Tip theo IGBT phi c kha li
trong iu kin , cng nhanh cng tt trnh pht nhit qu mnh . Trnh c hin
tng cht gi dng bng cch lin tc theo di dng collector l iu cn thit
khi thit k IGBT.
5. Yu cu vi tn hiu iu khin IGBTIGBT l thit b iu khin bng in p yu
cu in p c mt lin tc trn cc iu khin v emito xc nh ch kha, m. Mch iu
khin cho IGBT c yu cu ti thiu c biu din qua s di y:
- Tn hiu m c bin Uge, tn hiu kha c bin -Uge cung cp cho mch qua
in tr Rg. Mch G-E c bo v bi diode n p mc khong+-18V. Do c t k sinh
gia G v E nn k thut iu khin nh iu khin Mosfet c th c p dng tuy nhin
in p kha phi ln hn. Ni chung tn hiu iu khin thng c chn l+15 v -5V l
ph hp. Mc in p m khi kha gp phn gim tn tht cng sut trn mch iu khin
- in tr Rg cng lm tn hao cng sut iu khin c m t hnh di. in tr Rg nh,
gim thi gian xc lp tn hiu iu khin, gim tn tht nng lng trong qu trnh
iu khin nhng li lm mch iu khin nhy cm hn vi in p k sinh trong mch
iu khin.
6.Vn bo v IGBT- IGBT thng c s dng trong cc mch nghch lu hoc cc b
bin i xung p mt chiu, trong bin tn,mch ng ct tn s cao t 2 n hng chc
kHz. tn s ng ct cao nh vy, nhng s c c th ph hy phn t rt nhanh v dn
n ph hng ton b thit b. S c thng xy ra nht l qu dng do ngn mch t pha
ti hoc t cc phn t c li do ch to hoc lp rp.C th ngt dng IGBT bng cch
a in p iu khin v gi tr m. Tuy nhin qu ti dng in c th a IGBT ra khi
ch bo ha dn n cng sut pht nhit tng t ngt, ph hy phn t sau vi chu k
ng ct. Mt khc khi kha IGBT li trong mt thi gian rt ngn khi dng in
rt ln dn n tc tng dng qu ln, gy qu p trn collector, emiter, lp tc
nh thng phn t. Trong s c qu dng, khng th tip tc iu khin IGBT bng
nhng xung ngn theo qui lut nh c, cng khng n gin l ngt xung iu khin
dp tt dng in c.
- C th ngn chn hu qu ca vic tt dng t ngt bng cch s dng cc mch dp
RCmc song song vi cc phn t. Tuy nhin cc mch dp c th lm tng kch thc
v gim tin cy ca thit b. Gii php ti u c a ra l lm chm li qu trnh kha
ca IGBT, hay cn gi l kha mm khi pht hin c s c dng tng qu mc cho
php. Trong trng hp ny in p trn cc iu khin v emito c gim i t t v in
p m khi kha. IGBT s chuyn v trng thi kha qua ch tuyn tnh, do dng in
b hn ch v gim dn v khng, trnh c qu p trn phn t. Thi gian kha ca
IGBT c th ko di 5 n 10 ln thi gian kha thng thng.
7. Kim Tra IGBTS DUNG NG H O KIM TRA:
KIM TRA 1 IGBT CON TT HAY KHNG TA LAM NH SAU:1.S dung ng H S:
Que t ti chn E2 v Que en di chuyn qua 2 chn cn li (E1C2 v C1) th 1
chn E1C2 s ln 1,65k v ln o ti chn C1 s khng ln hoc ln hng chc k hoc
M l tt.
2.S Dung ng H Kim: o ch thang 0mh hay K Que t ti chn E2 v Que en
di chuyn qua 2 chn cn li (E1C2 v C1) th c 2 ln o u khng ln l tt. Cn
nu n ln 1 hoc 2 ln o th n b h nn thay th. o ch thang 1K Que en t ti
chn E2 v Que di chuyn qua 2 chn cn li (E1C2 v C1) th ln o ti chn
E1C2 l 5K ti chn C1 l 10 K l tt cn nu o 2 ln c s bng nhau 4K th b h
nn thay.
8.ng dung cua IGBT:IGBT c dung trong trong cac b bin tn hay cac
b bin i iu ch xung tn s rt cao, IGBT chim mt vi tri rt quan trong
trong cn nghip vi hoat ng trong pham vi cng sut n 10MW hoc cao
hn.
