Dien tu truong

8/8/2019 Dien tu truong

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IN T TRNG

1. Khi nim v t trng.* Nam chm v t tnh .Trong t nhin c mt s cht c th ht c st gi l nam chm t nhin.

Trong cng nghim ngi ta luyn thp hoc hp cht thp to thnh nam chmnhn to.Nam chm lun lun c hai cc l cc bc North (N) v cc nam South (S) , nucht thanh nam chm ra lm 2 th ta li c hai nam chm mi cng c hai cc Nv S - l nam chm c tnh cht khng phn chia..Nam chm thng c ng dng sn xut loa in ng, micro hoc m t DC.* T trngT trng l vng khng gian xung quanh nam chm c tnh cht truyn lc t lncc vt liu c t tnh, t trng l tp hp ca cc ng sc i t Bc n ccnam

* Cng t trngL i lng c trng cho mnh yu ca t trng, k hiu l H n v l A/m

* t cmL i lng c trng cho vt c t tnh chu tc ng ca t trng, t cmph thuc vo vt liu . VD St c t cm mnh hn ng nhiu ln . t cmc tnh bi cng thc

B = .H

Trong B : l t cm : l t thmH : l cng t trng

* T thngL s ng sc i qua mt n v din tch, t thng t l thut vi cng ttrng.


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* ng dng ca Nam chm vnh cu.Nam chm vnh cu c ng dng nhiu trong thit b in t, chng c dng sn xut Loa, Micro v cc loi M t DC.

T trng ca dng inCh nghin cu: T trng ca dng in i qua dy dn thng, t trng cadng in i qua cun dy, lc in t, hin tng cm ng in t, hin tng tcm.

Th nghim trn cho thy, khi cng tc bn ngoi ng, dng in i qua bng nlm bng n sng ng thi dng in i qua dy dn sinh ra t trng lm lchhng kim nam chm .Khi i chiu dng in, ta thy kim nam chm lch theo hng ngc li , nh vydng in i chiu s to ra t trng cng i chiu.


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Khi ta cho dng in chy qua cun dy, trong lng cun dy xut hin t trng lcc ng sc song song, nu li cun dy c thay bng li thp th t trng tptrung trn li thp v li thp tr thnh mt chic nam chm in, nu ta i chiudng in th t trng cng i hng

Dng in mt chiu c nh i qua cun dy s to ra t trng c nh, dng inbin i i qua cun dy s to ra t trng bin thin.

T trng bin thin c c im l s to ra in p cm ng trn cc cun dy ttrong vng nh hng ca t trng , t trng c nh khng c c im trn.

ng dng:T trng do cun dy sinh ra c rt nhiu ng dng trong thc t, mt ng dngm ta thng gp trong thit b in t l R le in t.


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R le in t

Khi cho dng in chy qua cun dy, li cun dy tr thnh mt nam chm inht thanh st v cng tc oc ng li, tc dng ca r le l dng mt dng innh iu khin ng mch cho dng in ln gp nhiu ln.

3. Lc in tNu c mt dy dn t trong mt t trng, khi cho dng in chy qua th dydn c mt lc y => l lc in t, nu dy dn t do chng s chuyn ngtrong t trng, nguyn l ny c ng dng khi sn xut loa in ng.


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Nguyn l hot ng ca Loa ( Speaker )

Cun dy c gn vi mng loa v t trong t trng mnh gia 2 cc ca namchm , cc S l li , cc N l phn xung quanh, khi cho dng in xoay chiu chyqua cun dy , di tc dng ca lc in t cun dy s chuyn ng, tc ngchuyn ng ca cun dy ph thuc vo tn s ca dng in xoay chiu, cun dychuyn ng c gng vo mng loa lm mng loa chuyn ng theo, nu chuynng tn s > 20 Hz chng s to ra sng m tn trong di tn s tai ngi nghec.

4. Cm ng in t .Cm ng in t l hin tng xut hin in p cm ng ca cun dy c ttrong mt t trng bin thin.V d : mt cun dy qun quanh mt li thp , khi cho dng in xoay chiu chayqua, trn li thp xut hin mt t trng bin thin, nu ta qun mt cun dykhc ln cng li thp th hai u cun dy mi s xut hin in p cm ng. Bnthn cun dy c dng in chy qua cng sinh ra in p cm ng v c chiungc vi chiu dng in i vo.

Tham kho 1 s ti liu! v hnh v thuc v Vinh


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DIOT BN DN


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it bn dn l cc linh kin in t th ng v phi tuyn, cho php dng in iqua n theo mt chiu m khng theo chiu ngc li, s dng cc tnh cht ca cccht bn dn.

C nhiu loi it bn dn, nh it chnh lu thng thng, it Zener, LED.

Chng u c nguyn l cu to chung l mt khi bn dn loi P ghp vi mt khibn dn loi N.

Hot ng

Khi bn dn loi P cha nhiu l trng t do mang in tch dng nn khi ghpvi khi bn dn N (cha cc in t t do) th cc l trng ny c xu hng chuynng khuch tn sang khi N. Cng lc khi P li nhn thm cc in t (in tchm) t khi N chuyn sang. Kt qu l khi P tch in m (thiu ht l trng v dtha in t) trong khi khi N tch in dng (thiu ht in t v d tha ltrng).

bin gii hai bn mt tip gip, mt s in t b l trng thu ht v khi chngtin li gn nhau, chng c xu hng kt hp vi nhau to thnh cc nguyn ttrung ha. Qu trnh ny c th gii phng nng lng di dng nh sng (hay ccbc x in t c bc sng gn ).

S tch in m bn khi P v dng bn khi N hnh thnh mt in p gi l inp tip xc (UTX). in trng sinh ra bi in p c hng t khi n n khi pnn cn tr chuyn ng khuch tn v nh vy sau mt thi gian k t lc ghp 2khi bn dn vi nhau th qu trnh chuyn ng khuch tn chm dt v tn tiin p tip xc. Lc ny ta ni tip xc P-N trng thi cn bng. in p tip xc

trng thi cn bng khong 0.6V i vi it lm bng bn dn Si v khong 0.3Vi vi it lm bng bn dn Ge.

ip p ngoi ngc chiu in p tip xc to ra dng in.

Hai bn mt tip gip l vng cc in t v l trng d gp nhau nht nn qutrnh ti hp thng xy ra vng ny hnh thnh cc nguyn t trung ha. V vyvng bin gii hai bn mt tip gip rt him cc ht dn in t do nn c gil vng ngho. Vng ny khng dn in tt, tr phi in p tip xc c cn bng

bi in p bn ngoi. y l ct li hot ng ca it.

ip p ngoi cng chiu in p tip xc ngn dng in.

Nu t in p bn ngoi ngc vi in p tip xc, s khuych tn ca cc int v l trng khng b ngn tr bi in p tip xc na v vng tip gip dn in


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tt. Nu t in p bn ngoi cng chiu vi in p tip xc, s khuych tn cacc in t v l trng cng b ngn li v vng ngho cng tr nn ngho ht dnin t do. Ni cch khc it ch cho php dng in qua n khi t in p theomt hng nht nh.

Tnh chtit ch dn in theo mt chiu t a-nt sang ca-tt. Theo nguyn l dng inchy t ni c in th cao n ni c in th thp, mun c dng in qua ittheo chiu t ni c in th cao n ni c in th thp, cn phi t a-nt mtin th cao hn ca-tt. Khi ta c UAK > 0 v ngc chiu vi in p tip xc(UTX). Nh vy mun c dng in qua it th in trng do UAK sinh ra phimnh hn in trng tip xc, tc l: UAK >UTX. Khi mt phn ca in pUAK dng cn bng vi in p tip xc (khong 0.6V), phn cn li dng todng in thun qua it.

Khi UAK > 0, ta ni it phn cc thun v dng in qua it lc gi l dngin thun (thng c k hiu l IF tc IFORWARD hoc ID tc IDIODE).Dng in thun c chiu t a-nt sang ca-tt.

Khi UAK cn bng vi in p tip xc th it tr nn dn in rt tt, tc lin tr ca it lc rt thp (khong vi chc Ohm). Do vy phn in p to ra dng in thun thng nh hn nhiu so vi phn in p dng cn bngvi UTX. Thng thng phn in p dng cn bng vi UTX cn khong 0.6Vv phn in p to dng thun khong 0.1V n 0.5V ty theo dng thun vi chcmA hay ln n vi Ampere. Nh vy gi tr ca UAK c dng qua itkhong 0.6V n 1.1V. Ngng 0.6V l ngng it bt u dn v khi UAK = 0.7V

th dng qua Diode khong vi chc mA.

Nu Diode cn tt th n khng dn in theo chiu ngc ca-tt sang a-nt. Thc tl vn tn ti dng ngc nu it b phn cc ngc vi hiu in th ln. Tuynhin dng in ngc rt nh (c A) v thng khng cn quan tm trong ccng dng cng nghip. Mi it chnh lu u khng dn in theo chiu ngcnhng nu in p ngc qu ln (VBR l ngng chu ng ca Diode) th it bnh thng, dng in qua it tng nhanh v t chy it. V vy khi s dng cntun th hai iu kin sau y:

Dng in thun qua it khng c ln hn gi tr ti a cho php (do nh

sn xut cung cp, c th tra cu trong cc ti liu ca hng sn xut xcnh).

in p phn cc ngc (tc UKA) khng c ln hn VBR (ngng nhthng ca it, cng do nh sn xut cung cp).

V d it 1N4007 c thng s k thut do hng sn xut cung cp nh sau:VBR=1000V, IFMAX = 1A, VF = 1.1V khi IF = IFMAX. Nhng thng s trn chobit:


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Dng in thun qua it khng c ln hn 1A. in p ngc cc i t ln it khng c ln hn 1000V. in p thun (tc UAK)c th tng n 1.1V nu dng in thun bng 1A.

Cng cn lu rng i vi cc it chnh lu ni chung th khi UAK = 0.6Vth it bt u dn in v khi UAK = 0.7V th dng qua it t n

vi chc mA

c tnh Volt-Ampere

c tnh Volt-Ampere ca Diode l th m t quan h gia dng in quait theo in p UAK t vo n. C th chia c tuyn ny thnh hai giaion:

o Giai on ng vi UAK = 0.7V > 0 m t quan h dng p khi itphn cc thun.

o Giai on ng vi UAK = 0.7V< 0 m t quan h dng p khi it

phn cc nghch.

(UAK ly gi tr 0,7V ch ng vi cc it Si, vi it Ge thng s ny khc)

Khi it c phn cc thun v dn in th dng in ch yu ph thucvo in tr ca mch ngoi (c mc ni tip vi it). Dng in phthuc rt t vo in tr thun ca it v in tr thun rt nh, thngkhng ng k so vi in tr ca mch in

ng dng

V it c c tnh ch dn in theo mt chiu t a-nt n ca-tt khi phncc thun nn it c dng chnh lu dng in xoay chiu thnh dngin mt chiu.

Ngoi ra it c ni tr thay i rt ln, nu phn cc thun RD 0 (ni tt),phn cc nghch RD (h mch), nn it c dng lm cc cng tc in t,ng ngt bng iu khin mc in p, c ng dng rng ri trong kthut in v in t.

MOSFET

1. Gii thiu v MosfetMosfet l Transistor hiu ng trng ( Metal Oxide Semiconductor Field EffectTransistor ) l mt Transistor c bit c cu to v hot ng khc vi Transistorthng thng m ta bit, Mosfet c nguyn tc hot ng da trn hiu ng ttrng to ra dng in, l linh kin c tr khng u vo ln thch hn cho


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khuych i cc ngun tn hiu yu, Mosfet c s dng nhiu trong cc mchngun Monitor, ngun my tnh .

Transistor hiu ng trng Mosfet

2. Cu to v k hiu ca Mosfet

K hiu v s chn tng ng gia Mosfet v Transistor


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* Cu to ca Mosfet.

Cu to ca Mosfet ngc Knh N

G : Gate gi l cc cng

S : Source gi l cc ngun

D : Drain gi l cc mng

Mosfet kn N c hai ming bn dn loi P t trn nn bn dn N, gia hai lp P-Nc cch in bi lp SiO2 hai ming bn dn P c ni ra thnh cc D v cc S,nn bn dn N c ni vi lp mng mng trn sau c du ra thnh cc G.

Mosfet c in tr gia cc G vi cc S v gia cc G vi cc D l v cng ln , cnin tr gia cc D v cc S ph thuc vo in p chnh lch gia cc G v cc S (UGS )

Khi in p UGS = 0 th in tr RDS rt ln, khi in p UGS > 0 => do hiu ngt trng lm cho in tr RDS gim, in p UGS cng ln th in tr RDS cngnh.

3. Nguyn tc hot ng ca Mosfet

Mch in th nghim


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Mch th nghim shot ng ca Mosfet

Th nghim : Cp ngun mt chiu UD qua mt bng n D vo hai cc D v S caMosfet Q (Phn cc thun cho Mosfet ngc) ta thy bng n khng sng ngha lkhng c dng in i qua cc DS khi chn G khng c cp in.

Khi cng tc K1 ng, ngun UG cp vo hai cc GS lm in p UGS > 0V => nQ1 dn => bng n D sng.

Khi cng tc K1 ngt, in p tch trn t C1 (t gm) vn duy tr cho n Q dn =>chng t khng c dng in i qua cc GS.

Khi cng tc K2 ng, in p tch trn t C1 gim bng 0 => UGS= 0V => n tt

=> T thc nghim trn ta thy rng : in p t vo chn G khng to ra dngGS nh trong Transistor thng thng m in p ny ch to ra t trng => lm

cho in tr RDS gim xung .

Kim tra Mosfet - ng dng Mosfet

Ni dung : Phng php o xc nh Mosfet cn tt, Mosfet b hng. ng dngca Mosfet trong thc t, Kim tra Mosfet trong mch in.1. o kim tra MosfetMt Mosfet cn tt : L khi o tr khng gia G vi S v gia G vi D c in trbng v cng ( kim khng ln c hai chiu o) v khi G c thot in th trkhng gia D v S phi l v cng.

Cc bc kim tra nh sau


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o kim tra Mosfet ngc thy cn tt.

Bc 1 : Chun b thang x1KW

Bc 2 : Np cho G mt in tch ( que en vo G que vo S hoc D )

Bc 3 : Sau khi np cho G mt in tch ta o gia D v S ( que en vo D que vo S ) => kim s ln.

Bc 4 : Chp G vo D hoc G vo S thot in chn G.

Bc 5 : Sau khi thot in chn G o li DS nh bc 3 kim khng ln.

=> Kt qu nh vy l Mosfet tt


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o kim tra Mosfet ngc thy b chp

Bc 1 : ng h thang x 1KW

o gia G v S hoc gia G v D nu kim ln = 0 W l chp

o gia D v S m c hai chiu o kim ln = 0 W l chp D S

2. ng dung ca Mosfet trong thc t

Mosfet trong ngun xung ca Monitor


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Mosfet c s dng lm n cng xut ngun Monitor

Trong b ngun xung ca Monitor hoc my vi tnh, ngi ta thng dng cp linh

kin l IC to dao ng v n Mosfet, dao ng to ra t IC c dng xung vungc a n chn G ca Mosfet, ti thi im xung c in p > 0V => n Mosfetdn, khi xung dao ng = 0V Mosfet ngt => nh vy dao ng to ra s iu khincho Mosfet lin tc ng ngt to thnh dng in bin thin lin tc chy qua cuns cp => sinh ra t trng bin thin cm ng ln cc cun th cp => cho ta inp ra.

* o kim tra Mosfet trong mch .Khi kim tra Mosfet trong mch , ta ch cn thang x1W v o gia D v S => Nu1 chiu kim ln o chiu o kim khng ln => l Mosfet bnh thng, Nu c haichiu kim ln = 0 W l Mosfet b chp DS.

C tham kho mt s ti liu !

DNG IN XOAY CHIU

1. Dng in xoay chiu :Dng in xoay chiu l dng in c chiu v gi tr bin i theo thi gian, nhngthay i ny thng tun hon theo mt chu k nht nh


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trn l cc dng in xoay chiu hnh sin, xung vung v xung nhn.

Chu k v tn s ca dng in xoay chiu.Chu k ca dng in xoay chiu k hiu l T l khong thi gian m in xoaychiu lp li v tr c , chu k c tnh bng giy (s)Tn s in xoay chiu : l s ln lp li trang thi c ca dng in xoay chiutrong mt giy k hiu l F n v l Hz

F = 1 / T

Pha ca dng in xoay chiu :Ni n pha ca dng xoay chiu ta thng ni ti s so snh gia 2 dng in xoay

chiu c cng tn s .* Hai dng in xoay chiu cng pha l hai dng in c cc thi im in p cngtng v cng gim nh nhau:

Hai dng in xoay chiu cng pha

* Hai dng in xoay chiu lch pha : l hai dng in c cc thi im in p tnggim lch nhau .


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Hai dng in xoay chiu lch pha

* Hai dng in xoay chiu ngc pha : l hai dng in lch pha 180 , khi dngin ny tng th dng in kia gim v ngc li

Hai dng in xoay chiu ngc pha

Bin ca dng in xoay chiuBin ca dng xoay chiu l gi tr in p nh ca dng in.xoay chiu, bin

ny thng cao hn in p m ta o c t cc ng h

Gi tr hiu dng ca dng in xoay chiuThng l gi tr o c t cc ng h v cng l gi tr in p c ghi trn zccm ngun ca cc thit b in t., V d ngun 220V AC m ta ang s dngchnh l ch gi tr hiu dng, thc t bin nh ca in p 220V AC khong220V x 1,4 ln = khong 300V

Cng xut ca dng in xoay chiu .Cng xut dng in xoay chiu ph thuc vo cng , in p v lch phagia hai i lng trn , cng xut c tnh bi cng thc :

P = U.I.cos

Trong U : l in p

I l dng in

l gc lch pha gia U v I


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=> Nu dng xoay chiu i qua in tr th lch pha ga U v I l = 0 khi cos = 1 v P = U.I

=> Nu dng xoay chiu i qua cun dy hoc t in th lch pha gia U v I l

+90 hoc -90, khi cos = 0 v P = 0 ( cng xut ca dng in xoay chiu khii qua t in hoc cun dy l = 0 )

HNG DN PHN TCH S MCH

iu cn ch u tin khi xem xt c s mch l phi tm kim, nhn bit c ttc cc mch c bn tham gia to ra chc nng chung . (Th d cc tng khuchi, b bin i tr khng, cc tng phn dng, cc tng o, v.v...). Cn phi phnbit c u l iu ct yu v u l iu khng ct yu, khi phn tch mch inri ra thnh tng phn c bn nh nhn xt bng mt.

Trong cch c mch in chng ta cn phi nhanh chng phn tch v nh gic c s mch theo chc nng ca chng.

iu cn ch u tin khi xem xt c s mch l phi tm kim, nhn bit c ttc cc mch c bn tham gia to ra chc nng chung . (Th d cc tng khuchi, b bin i tr khng, cc tng phn dng, cc tng o, v.v...). Cn phi phnbit c u l iu ct yu v u l iu khng ct yu, khi m x phn tchmch in ri ra thnh tng phn c bn nh nhn xt bng mt. iu u tin taphi quan st k lng ti cc s mch thnh phn v cc linh kin ring l,

ri sau t t kt hp tr li thnh chc nng chung cn bit. y ta khng xtn cc phn t s dng c trng ( l iu khng ct yu) th d nh cm inu vo v u ra, chit p bin i bin , b bin tr tng v cng tc chuynmch, n ch c th gip ta c n tng mnh hn v chc nng chung ca mch.

Th d hnh 1 ch ra mch in ca mt b to dao ng t hnh sin sang hnh chnht.

B to dao ng c cc phn t c trng:

- Chit p iu chnh tn s;

- Chit p iu chnh bin ;

- Cng tc iu chnh tn s thp phn;

- Cng tc iu chnh bin thp phn;

- B chuyn mch chc nng tn hiu ch nht -sin.


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Vi 5 tng Tranzistor trong s mch cho php phn chia thnh hai nhm chcnng khc nhau (y l iu ct yu).

Cc tng T1 v T2 c bit n nh l cc tng khuch i in p (mch c s

emito), tng T3 nh l b bin i tr khng v l mch c s colecto. u ra canhm b khuch i ny nm emito ca Tranzsitor T3.

S m t s lc v cc tng T1 v T2 nh trn r rng khng th cho ta bit c l phng thc lm vic ca hai tng khuch i. Nhng qua ta cng thyngay c, y khng c mt th hin no ca mt tng o (s mch Trigger).iu ny c th nhn bit c nh vo cch u ghp mch: colecto-bazo cngnh colecto-emito.

Ngc li nhn vo cu trc cc tng Tranzistor T4 v T6 c th nhn ra ngay cy l mt tng o v vi cch sp xp u ghp mch ta cng nhn ra c l

mt mch c bn Schmitt - Trigger.Vi nhng hiu bit v chc nng quen thuc ca mt b to dao ng (xem Kthut mch in t, tc gi Phm Minh H, Nh xut bn Khoa hc v K thut),th vic nhn bit cc chc nng ca tng khi ring l ca n khng phi l vickh.

Trc ht nhm cc b khuch i l thnh phn ca b to dao ng hnh sin. BSchmitt -Trigger dng bin i thnh nhng dao ng xung ch nht. Cc chcnng ny c thit lp nh s sp xp cc cng tc chuyn mch ca b chuynmch. Qua cng tc S2b m in p cung cp ca Schmitt-Trigger c ng hocct mch. Tc ng th hai theo phng thc la chn S2a ng mch t u raca Schmitt-Trigger ln u ra ca b khuch i (lin kt R20, C1, emito T3). Nhs b tr cc t in C2 ti C10 v cc in tr R9a,b v R10 cho php ta nhn ra l cu trc ca mt cu Wien-Robinson. N nm u ra ca b khuch i. Mtkhc vi s ni trc tip vo bazo ca T1 nn ng thi n li l u vo ca bkhuch i. Chnh v vy b to dao ng m t mt mch cu Wien.

t c mc ch trn vn khi quan st tng qut cc chc nng mch, th cnphi tin chc vo s phi hp hi ho cc chc nng ca cc phn t s dng cnli. Th d nh bin tr R19 nm u ra ca cc khi chc nng nh l mt intr u cui. B chia in p c hai phn. Phn th nht ch c in p lm vicc ng v tt mch. Phn th hai ng mch b chia in p R21 ti R24.

Qua phn tch trn, v c bn mch in ca b to dao ng c phn tch.Chng ta c th tm tt cc kt qu phn tch c bn t th d ny:

- Quan st s khi tng qut v tm ra c cc nhm chc nng,

- Xc nh cc nhm chc nng,


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- Xc nh tc dng chung ca cc nhm chc nng trong c kt ni vi cc phnt s dng.

Chng ta tip tc quan st phn tch thm mt mch in na trong hnh 2.

Chc nng quen thuc ca mt mch ch bo chng ta bit: trn c s mt tnhiu u vo, mch tng cui s ng mch, n sng, ng thi cho qua u ramt xung mch. Nu ta ch s mch mt cch chi tit th ngay t ci nhn utin cho php phn chia cc tng Tranzistor thnh 3 nhm chc nng (y l iuct yu):

- Nhm chc nng th nht to bi cc tng T37, T38, T39;

- Cc tng T40, T41 nh l Trigger- Schmitt;

- Tng cui cng T42 nhn bit c nh l tng chuyn mch.Nhng nu quan st k hn v cc tng ny th ta c th tip tc phn chia chcnng ca nhm th nht:

- Tng T37 nh l mt b khuch i v

- Cc tng T38, T39 nh l mt mch to dng xung.

Cc chc nng ny nhn ra c l nh cch u ghp mch. Tng T37 to vi cct in C16, C19 v C18 thnh mt b khuch i lc bng. Mch to dng xungT38 v T39 ghp in dung c iu chnh v tr cn bng theo mt gi trnh bin tr R114, gi tr ny lm cho T3 khng dn in v dng in c dnqua Tranzistor T39. Trong trng hp nh ca in p khuch i vt qu inp gii hn c iu chnh th mch to dng xung s chuyn mch sang trngthi khc: T38 dn v T39 ng. Vi in p xut hin qua colecto ca TranzistorT39, t in C20 c np in qua diot tch mch D49. Diot D49 s ngn t inC20 phng in qua Tranzistor T39 trong khong ngng xung.

Schmitt-Trigger bao gm cc Tranzistor T40 v T41 s c chuyn mch sau khi t c mt gi tr in p xc nh t in C20. Qua qu trnh chuyn mch,Tranzistor T41 ng v colecto thit lp mt in p dng. Nh in p ny mTranzistor T42 ng mch v n chiu sng. Khi ny u ra xut hin mt s tbin v in p t +1,5V thnh +21 n +24V.

n y nu bn c hiu tt nhng vn va phn tch trn v c th t giithch chnh xc cc chc nng ca mch, th nhng phn sau bn khng cn phitip tc c v x l na. Trong trng hp ngc li bn hy tip tc c vnghin cu cc bi vit trong cc s sau. Cn rt nhiu vn th v c cpn cho nhiu dng mch in khc nhau./.


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MCH CHNH LU

Mt mch chnh lu l mt mch in c cc thit b in t, dng bin i dngin xoay chiu thnh dng in mt chiu. Cc mch chnh lu c th dng trongcc b ngun cp in, v trong cc mch tch sng ca tn hiu v tuyn. Cc mchchnh lu c th c lp bng cc it bn dn, cc n chnh lu thy ngn v cck thut khc.

Khi ch dng mt it n l chnh lu dng in xoay chiu, bng cch kha

khng cho phn dng hoc phn m ca dng sng i qua mch in, th thutng "chnh lu" v "it" c th c xem nh l mt. a s cc mch chnh lus dng nhiu it vi cc cch sp xp khc nhau c th bin i t xoay chiuthnh mt chiu tt hn trng hp s dng mt it ring l. Trc khi cc itbn dn pht trin, ngi ta cn dng cc mch chnh lu s dng n in t chnkhng, n chnh lu thy ngn, cc dy bn dn a tinh th seleni.

Cc my truyn thanh v tuyn u tin, ngi ta gi l cc my tinh th, dng mtsi "ru mo" hoc mt kim nhn tip xc nh vo mt im trn mt khi tinh thgalena (sunpht ch) to ra mt it tip im, hoc mt b tch sng tinh th.Trong h thng sy t kh, cc b pht hin la c th dng. Hai in cc trong

mt v bc kn c th sn sinh ra dng in v c th chnh lu c mt dng inxoay chiu, nhng ch khi chng nhn thy ngn la.

Mch chnh lu na sng

Mt mch chnh lu na sng ch mt trong na chu k dng hoc m c th ddng i ngang qua it, trong khi na kia s b kha, ty thuc vo chiu lp t


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ca it. V ch c mt na chu k c chnh lu, nn mch chnh lu na sng chiu sut truyn cng sut rt thp. Mch hnh lu na sng c th lp bng chmt i t bn dn trong cc mch ngun mt pha

Chnh lu ton sng

Mch chnh lu ton sng bin i c hai thnh phn cc tnh ca dng sng u

vo thnh mt chiu. Do n c hiu sut cao hn. Tuy nhin trong mch inkhng c im gia ca bin p ngi ta s cn n 4 it thay v mt nh trongmch chnh lu na sng. iu ny c ngha l u cc ca in p ra s cn n 2it chnh lu, th d nh 1 cho trng hp im X dng, v 1 cho trng hpim X m. u ra cn li cng cn chnh xc nh th, kt qu l phi cn n 4it. Cc it dng cho kiu ni ny gi l cu chnh lu.

B chnh lu ton sng bin i c 2 na chu k thnh mt in p u ra c mtchiu duy nht: dng (hoc m) v n chuyn hng i ca dng in ca na chuk m (hoc dng)ca dng sng xoay chiu. Na cn li s kt hp vi na kiathnh mt in p chnh lu hon chnh.

i vi ngun xoay chiu mt pha, nu dng bin p c im gia, ch cn 2 it niu lng vi nhau (ngha l anode-vi-anode hoc cathode-vi-cathode)c th thnhmt mch chnh lu ton sng.


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Mt mch chnh lu dng n chn khng thng dng s dng mt n c 1cathode v 2 anode trong cng mt v bc; Trong trng hp ny, 2 it ch cnmt bng chn khng. Cc n 5U4 v 5Y3 l nhng th d thng dung nht chokiu mch ny.

Mch in ba pha cn n 6 it. Thng thng cn 3 cp, nhng khng phi cngloi vi it i s dng trong chnh lu mt pha ton sng. Thay vo ngi tadng cp it ni tip vi nhau (cathode ni vi Anode. Thng th cc it i s

c b tr ra 4 chn, c th ty u ni cho mch chnh lu ton sng mtpha, hay mch cu mt pha v ba pha

Hu tht cc thit b pht sinh ra dng in xoay chiu (nh my pht in xoaychiu) u pht ra in ba pha. My pht in trn xe t c 6 it lp kiu chnhlu cu ba pha chnh lu thnh dng in mt chiu, np in cho bnh c quy.

Tht thot nh sng.

Khuyt im ca cc mch chnh lu l tht thot t nh sng u vo n nhsng u ra, gy ra bi in p ngng ca it. in p ny xp x 0,7 vn i viit thng, v 0,1 vn i vi it Schottky. Cc mch chnh lu na sng, cmch chnh lu ton sng c 2 cun dy, s c tht thot nh sng bng in p ritrn mt it. Cc mch chnh lu cu s c in p tht thot bng in p ri trn2 it. iu ny c th thy tht thot ny s ng k i vi nhng mch c in pcung cp rt b. Hn na, v cc it khng th dn khi in p di in p ny,mch ch c th cho dng in i qua trong mt phn ca na chu k. V th s cmt phn nh in p bng 0 xut hin xen k vi cc on c in p


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San bng in p ra ca mch chnh lu

C hai mch chnh lu na sng v ton sng u c nhc im l n thay i theodng ca sng u vo, m khng cung cp in p khng i. to ra mt dngin p mt chiu u n t ng ra ca b chnh lu, cn phi c mt mch "san

bng", cn gi l mch lc. Mch lc n gin nht dng mt t tch in, hay t lchoc t san bng t vo u ra ca mch chnh lu. Mch ny vn cn lu li mtt thnh phn in p xoay chiu (gn sng) v in p khng hon ton bngphng.

Kch thc ca t in th hin tnh kinh t. i vi mt ti cho sn, t in cngln cng lm gim gn sng, nhng li lm tng gi thnh, v lm tng dngin nh trn th cp ca cun dy th cp my bin p v mch cp ngun chon. Trong nhng trng hp c bit, nhiu b chnh lu ni vo im phn phingun, s gy kh khn cho s bo m dng hnh sin ca in p.

Vi mt h s gn sng cho trc, ln ca t lc s t l vi dng in ti, t lnghch vi tn s chnh lu, v s lng cc nh ca dng sng trong mi chu k.Dng in ti v tn s ngun cp thng ngoi tm kim sot ca ngi thit kmch chnh lu nhng s lng nh trong mi chu k li c th iu khin cbng cch chn s chnh lu thch hp.

Mch chnh lu bn sng cho 1 in p nh trn mi chu k, v th thng ch sdng cho cc ng dng c dng in nh. Mch chnh lu ton sng mt pha cho 2nh trn mi chu k, v y l cch tt nht cho mch chnh lu mt pha. i vichnh lu ba pha, c n 6 nh trn mi chu k v c th cao hn nu ta s dngcc bin p thch hp trc b chnh lu nhm tng s pha ln.

lm gim gn sng hn na, ngi ta dng mt b lc c u vo t in vmt cun cm lc. i khi cng c th kt hp t lc vi cun cm v t lc phasau, sao cho in p ra tng i u n. Cun dy ny s cp in khng ln ivi thnh phn gn sng.

Nu dng in ti ph thuc nhiu vo mc gn sng ca ngun, c th dng mtb n p thay cho cc t lc c ln. C hai u gim gn sng v ngn chns thay i ca in p ra theo in p ngun v theo dng ti.

==B chnh lu tng i in p====d Mt mch chnh lu na sng on gin c

th lp rp theo 2 kiu vi cc tnh ca 2 it i khng nhau mt kiu ni cho rain p dng, v mt kiu ni cho ra in p m. Nu kt hp c 2 kiu ny cngvi hai b lc san bng c lp, c th t c in p ra xp x bng 2 ln in pnh ca mch xoay chiu. iu ny cng c th c c bng cch ni bin p cim gia cho php mi mch in l mt mch cp ngun ring.

Mt bin th khc ca mch ny l dng cc t in ni tip nhau lm mch sanbng dng ng ra ca cu chnh lu. Sau t mt kha chuyn mch t im


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gia ca hai t in n mt trong cc u AC ng vo. Khi kha ny m, mchhot ng nh mt mch chnh lu cu bnh thng. Nhng khi ng kha, n shot ng nh mt mch nhn i in p. Ni cch khc, c th to ra in p mtchiu khong 320V mt cch d dng t bt k ngun no cp cho cc mch np kiu ng ct

ng dng

Mt it chnh lu v cc ph kin gii nhit.

ng dng c bn nht ca mch chnh lu l trch xut thnh phn in mt chiuhu dng t ngun xoay chiu. Thc tra hu ht cc ng dng in t s dngngun in mt chiu, nhng ngun cung cp li l dng in xoay chiu. V th ccmch chnh lu c s dng bn trong mch cp ngun ca hu ht cc thit b

in t.

Mch bin i in mt chiu t in p ny sang in p khc s phc tp hn.Mt trong nhng phng php i t in mt chiu sang in mt chiu l: utin chuyn t mt chiu thnh xoay chiu, (dng mt mch nghch lu)sau aqua my bin p thay i in p, v cui cng l chnh lu li thnh in mtchiu.

Cc mch chnh lu cng c ng dng trong mch tch sng cc tn hiu vtuyn iu bin bin . Tn hiu c th cn hoc khng cn khuch i trc khitch sng. Nu tn hiu nh qu, phi s dng cc it c in p ri rt thp.

Trong trng hp ny cc t v in tr ti phi la chn cn thn cho ph hp.Tr s t in thp qu s lm cho sng cao tn lt sang u ra. Chn cao qu, n cth np y v gi nguyn in p c np.

in p ra ca mt mch chnh lu ton sng vi cc thyristor c iu khin.

Cc mch chnh lu cng c s dng cp in c cc tnh cho my hn in.Cc mch nh th ny i khi thay th cc it trong cu chnh lu bng ccThyristor. Cc mch ny s c in p ra ph thuc vo gc kch mi.


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