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Ngun ATX: Cc mch cp trc thng dng

15-02-2009 | lqv77 | 4 phn hi

1 Ngun Stanby c hi tip trc tip

1. S nguyn l. Bn a tr chut vo s xem ch thch

S nguyn l ca ngun Stanby c hi tip trc tip

2. Nguyn l hot ng.Nguyn l to v duy tr dao ng:-

Khi c in p u vo cp cho b ngun, mt dng in s i qua intr mi (R81)vo nh thin cho n cng sut (Q16) lm cho n cnsut dn kh mnh, ngay khi n cng sut dn, dng in bin thintrn cun s cp cm ng sang cun hi tip, do cun dy hi tipmc o chiu so vi cun s cp nn in p hi tip thu c c gitr m, in p ny np qua t hi tip C15 lm cho in p chn B ncng sut gim < 0V, n cng sut b kho, khi n cng sut tt=> in p hi tip b mt => in tr mi li lm cho n dn chu k k tip => qu trnh lp i lp li to thnh dao ng.

Nguyn l n nh in p ra:-i t D6 chnh lu in p hi tip ly ra in p m c gi trkhong 6V, in p ny c t C12 lc cho bng phng gi lin p hi tip (Uht)- Hai i t l i t Zener ZD27 v i t D5gim mt gi tr in p khng i hai u bng khong 6,6V, t xclp cho chn B n cng sut mt gi tr in p khong 0,6V- Dost p trn hai i t ZD27 v D5 l khng i, nn in p chn Bn cng sut n ph thuc vo in p hi tip (Uht)

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- Gi s khiin p u vo tng => in p u ra c xu hng tng => inp trn cun hi tip cng tng => in p hi tip (Uht) cng mhn => lm cho in p chn B n cng sut gim xung => ncng sut hot ng yu i => lm cho in p ra gim xung v vtr ban u.

- Ngc li khi in p u vo gim => in p ura c xu hng gim => in p trn cun hi tip cng gim =>in p hi tip (Uht) bt m hn (hay c xu hng dng ln) => lmcho in p chn B n cng sut tng ln => n cng sut hotng mnh hn => lm cho in p ra tng ln v v tr ban u.

3. c im ca loi ngun ny-y l loi ngun s dng in p hi tip m cho nn in tr nhthin kh nh v cho dng nh thin tng i ln, khi mi c ngun300V u vo, n cng sut dn mnh, nh mch hi tip m m n chuynsang trng thi ngt to thnh dao ng v khng lm hng n.

-Trong trng hp b mt hi tip m a v qua C15 v R82 th n cngsut c hot ng lin tc cng sut ln v n s b hng (b chp)sau vi giy.

4. Gii p thc mc cho tng linh kin trn b ngun.

Cu hi 1 Cho bit nguyn nhn khi b ngun trn b mt in p ra (ra bng 0V)Tr li:B ngun trn cho in p ra bng 0V l do ngun b mt dao ng, c th do hng cc linhkin sau y:- t in tr mi- Bong chn R82 hoc C15 (lm mt in p hi tip)- Mt in p 300V DC u vo

Cu hi 2 Cho bit nguyn nhn khi b ngun trn c in p ra rt thp (v d ng12V nay ch cn khong 6V)

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Tr liTa hy phn tch nh sau ta s thy c nguyn nhn h hng ca n:- Khi in p ra trn t C30 c 12V th in p hi tip trn C12 c -6V-Vy khi in p ra trn t C30 ch cn 6V ng ngha vi in p trnt C12 ch cn 3V (v in p trn cc cun dy ca bin p lun lun

t l thun vi nhau)- V ngun vn ang hot ng (ngha l chn Bn cng sut phi c in p khong 0,6V) => t ta suy ra st ptrn hai i t Zener ZD27 v i t D5 ch cn khong 3,6V, hai it ny khi bnh thng chng lun lun gim mc 6,6V v by gi theosuy lun chng ch cn gim mc 3,6V=> nh vy i t Zener ZD27 b d.

Cu hi 3 Cho bit nguyn nhn khi b ngun trn c in p ra rt cao (v d ng12V nay ra n 20V)Tr liPhntch nh cu hi 2 th ta thy rng, in p u ra c t l thun vi

st p trn i t Zener hay ni cch khc, nu in p u ra gm l it Zener b d, nu in p ra tng l i t Zener b t, nh vytrng hp ny l do i t Zener ZD27 b t hoc D5 b t.

Cu hi 4 Nu ngun trn b t in tr mi (t R81) th sinh ra bnh g ?Tr li- Khi t in tr mi th ngun s b mt dao ng v tt nhin in p u ra s b mt

Cu hi 5 Nu ngun trn b bong chn t hi tip C15 th sinh ra bnh g ?Tr li-Nu b bong chn t C15 th ngun cng b mt dao ng, nhng y l

ngun hi tip m nn khi bong chn cc linh kin ca mch hi tip(lm mt hi tip) s b lm hng n cng sut do n cng sut dnmnh m khng chuyn sang c trng thi ngt.

Cu hi 6 Nu ngun trn b hng i t Zener ZD27 th c hin tng g ?Tr li- Nh phn tch cu hi 3 th ta thy rng:- Nu i t Zener ZD27 b chp th in p ra s gim xung rt thp sp s bng 0V- Nu i t Zener ZD27 b t th in p ra s tng ln rt cao hng chc vol

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Cu hi 7 Nu ngun trn b t R9 th c hin tng g ?

Tr li-R9 l in tr phn p, nu t th in p chn B n cng sut stng cao v n cng sut hot ng qu ti v c th b hng ngay tkhi mi c cp ngun.

Cu hi 8 Nu ngun trn b t R83 th c hin tng g ?Tr li-Khi b t R83 => in p hi tip s cng m hn => lm cho inp chn B n cng sut gim => in p ra gim thp.

Cu hi 9 Nu ngun trn b kh t C12 c hin tng g ?Tr li-Khi t C12 b kh => in p m trn t ny s bt m => in pchn B n cng sut s tng => v in p ra s tng.

Cu hi 10 Nu ngun trn t R8 hoc bong chn C14 th sinh ra hin tng g ?Tr li-ay l mch nht xung bo v cc xung nhn nh thng mi CE ca ncng sut, nu mt tc dng ca mch ny th n cng sut c th bhng, b chp.

5. Ngun Stanby c mch bo v qu dng

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Mch ngun ny c nguyn l hon ton ging mc ngun trn nhng c thm mch bo vqu dng

Cc linh kin: R12, R13 v Q4 l cc linh kin ca mch bo v qu dng, nguyn l hot ngca mch nh sau:-Gi s khi ph ti ca ngun b chp, khi n Q3 s hot ng rt

mnh, st p trn R12 tng cao, st p ny c a qua R13 sang chn Bn bo v Q4, nu in p ny > 0,6V th n Q4 s dn bo ho=> khi n s u tt chn B n cng sut xung Mass , n cngsut c bo v, trong trng hp ny ngun s chuyn sang hin tngt kch, in p ra thp v c mt c mt ., nu o in p rathy kim ng h dao ng.

2 So snh hai mch ngun c hi tip so quang.

1. Mch ngun Stanby s 1

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2. Mch ngun Stanby s 2

Bn a tr chut vo s xem ch thch cho cc linh kin

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S ging nhau:- Hai b ngun trn c nguyn l hot ng tng t nh nhau.- C hai b ngun u c mch hi tip so quang n nh in p ra- C hai ngun u c n cng sut v n sa sai.

S khc nhau:- Mch ngun s 1 c n cng sut l Mosfet trong khi mch ngun s 2 c n cng sut ln BCE- Mch ngun s 1 do s dng Mosfet nn in tr mi c tr s rt ln (2M), trong khi mchngun th 2 in tr mi ch c 680K

3 Phn tch cc bnh thng gp ca b ngun c hi tip so quang

1. Bnh 1 in p ra bng 0 VNguyn nhn:in p ra bng 0V l do ngun b mt dao ng hoc do b mt in p 300V u vo.

C th do hng mt trong cc linh kin ca mch to dao ng nh:- R mi (R501)- R, C hi tip (R504 v C502)- n cng sut (Q2)- n sa sai (Q1 nu chp s lm mt dao ng)

Kim tra:- o kim tra xem c in p DC 300V u vo khng ?- o kim tra in tr mi (R501)- o kim tra in tr hi tip (504)

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- Hn li chn t ly hi tip (C502)- Kim tra n sa sai (Q1)- Kim tra n cng sut (Q2)

2. Bnh 2 in p ra thp v t kch (t kch tc l in p dao ng c ri mt lp i lp

li)

Hin tng ngun b t kch

Nguyn nhn:Phn tch: c in p ra tc l n cng sut tt v mch c dao ng, cc linh kin camch dao ng ttNguyn nhn ngun b t kch l do.- Chp ph ti u ra (mch bo v qa dng hot ng sinh ra t kch)

- i t chnh lu b chp (mch bo v qa dng hot ng sinh ra t kch)- Hng mch hi tip so quang lm cho in p hi tip v qu mnh hoc qu yu

- Nu hi tip v yu th in p ra tng cao v mch bo v qup s hot ng sinh ra t kch.- Nu hi tip v mnh th bn thn in p hi tip lm cho n cng sut ngt v t kch

Kim tra:- o xem ph ti 12V v 5V u ra c b chp khng ?(Cch o Chnh ng h thang 1, o vo hai u t lc ng in p 5V (C04) v

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12V(C22) th c mt chiu ophi cho tr khng cao vi trm , nu c hai chiu o thy tr khng thp sp s 0 th => thng ti b chp)- o kim tra cc i t chnh lu D03 v D04 xem c b chp khng ?- Thay th IC khuch i in p ly mu TL431- Thay IC so quang IC3-817

- Nu khng c th tm tho i t Zener bo v qu p ra (ZD1)- Kim tra k cc in tr ca mch ly mu (R51 v R512)

3. Bnh 3 in p ra thp hn so vi in p thng thng (v d ng 12V nay ch cn8V)

o in p ra ca ngun cp trc, bn chnh ng h v thang 10VDC, o que vo u

dng ca i t chnh lu, que en vo mass bn th cpNguyn nhn v kim tra:Nguyn nhn ca hin tng ny thng do mch hi tip a in p hi tip v qu mnh, vvy bn cn kim tra k cc linh kin ca mch hi tip so quang nh sau:- Kim tra cu in tr ca mch ly mu (R51 v R512)- Thay th IC khuch i in p ly mu TL 431- Thay th IC so quang

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B ngun ATX ton tp: Mch cp trc dng 1

26-06-2009 | lqv77 | 1 phn hi

Tng quan v ngun ATX Mch lc xoay chu v mch nng lc s cp Mch cp trc dng 2

3.2. Mch standby dng dao ng blockingDng 1 : Hi tip trc tip (minh ha bng mch stabdby ngun LC-200)

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Mch c cp ngun 300Vdc t mch nn/lc s cp.Tc dng linh kin :Q12 : Dao ng blocking, ng thi l cng sut stanby.R55/R56 : nh thin cho Q12, ng vai tr l in tr miD23 : Nn hi tip duy tr dao ng, in p ra Anode D28 mang cc tnh m (-).C19 : Lc san bng in p hi tip.R57 : Phn p, n nh s b in p hi tip.ZD2 : Ct hi tip khi in p m (-) t im A nh hn in p n p ca n.C3/L2 : Khung cng hng RC song song, tn s cng hng ring ca khung ny c tnh bngcng thc : f = 1/2xsqrt(L2xC3). Cc bn c th thc mc v iu ny, tuy nhin i vi tn hiu xoaychiu th (+) ngun v mass coi nh chp (thng qua cc t lc) v vy i vi xoay chiu th R55/C3coi nh mc song song vi L2.L1 : Ti ca Q12.L2 : Cun hi tip vi nhim v to in p theo hiu ng lenz s dng duy tr dao ng.R58/C23/D32 : Kh in p ngc, chng ngt dao ng.

Nguyn l :in p 300V qua R55/R56 nh thin chn B Q12, in p ny ti chn B ~2V (o DC khi ngt hitip) lm cho Q12 m bo ha lun.Khi Q12 bo ha, dng in qua n nh sau : (+)300V qua L1 chn C Q12 EC Q12 mass. Vdng ny i qua L1, theo c tnh ca cun cm (lun sinh ra dng chng li dng qua n theo hintng cm ng in t) nn dng qua L1 khng t mc bo ha ngay m tng ln t t. V vy ttrng sinh ra trn li bin p STB cun tng t t (t trng ng).Theo nh lut cm ng in t Lenz, t trng tng t t trn li bin p STB s lm pht sinh trn ttc cc cun dy ca bin p 1 sut in ng cm ng.

in p cm ng trn L2 c nn bi D28 v lc bng C19 ly ra inp 1 chiu cc tnh m (-) im A, c n nh (tng i) bng R57, n dnh ph thuc vo tch s T = R57xC19 (thi hng hng s thi gian tch thot ca mch RC)in p ti im A li qua ZD2 ti chn B ca Q12. V l in p m nn n xung i vi in pdng do nh thin R55/56 a ti, kt qu l 2 in p ny trng ha ln nhau lm cho in p chn BQ12 tr v 0, dng qua L1, Q12 mt.Khi dng qua L1, Q12 mt th t trng trn n cng mt i lm cho t trng trn li bin p = 0 dnn in p cm ng trn cc cun day bin p STB = 0. D nhin in p cm ng trn cun L2 mt.V in p trn L2 mt nn D28 ko a in p m na. Tuy vy v c C19 np (lc trc) nn gi

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n x lm cho in p ti im A ko mt ngay, vic C19 x s duy tr mc m chn B Q12 thm 1thi gian na, Q12 tip tc kha. Ti khi in p m do C19 x ko ln m ZD2 th ZD2 s ngt,ko cn in p m ti chn B Q12, lc ny chn B ch cn p dng do R55/56 a ti v n li mbo ha. Mt chu trnh bo ha/kha li bt u.

Tn s dao ng ca mch :c quyt nh b L2/C3. V y l cng hng song song nn khi cng hng th dng qua L2 l

max, khi dng hi tip l max cho ZD2 m, Q12 s kha khi s cng hng mt i. Ni cchkhc th tn s dao ng ca mch chnh bng 1/2xsqrt(L2xC3).Thc t, khi Q12 kha, dng qua L1 ko mt ngay do t trng trn li bin p vn cn (nh) lm xuthin in p cm ng trn L1 vi chiu (+) C Q12 ,in p ny tn ti trong thi gian cc ngn(ging nh qut ngc cng sut dng tivi, CRT) nn c gi tr rt ln (~ 800V vi ngun i mi)lm pht sinh 2 hu qu :- Q12 c th b nh thng do p qu ln, khc phc th Q12 c thit k dng loi in p cao.- Q12 c dng r do in p ln, dn ti dng qua L1 c duy tr, in p cm ng trn L1 duy tr lmcho ip p m (-) v B Q12 cng duy tr v ko th phc hi c in p nh thin (+) v nh vychu trnh bo ha/kha ko thc hin. Ni cch khc, dao ng mt.Khc phc : Khi p chn C Q12 tng cao s phng qua D32 trung ha vi in p trn C23. Nu bn

tnh theo gi tr in p s thy l p ti chn C Q12 v in p trn C32 l ngc chiu, trung ha lnnhau. R58 l in tr tng cng thi gian trung ha l rt ngn, loi b c hin tng d Q12,khi phc chu k dao ng.

Lu : hiu r cc bn hy xem li l thuyt v ch hot ng ca BJT (ch A, B, C) vnguyn l mch cng hng, cc tham s khi cng hng.in p cm ng trn L3 c sinh ra nh t trng bin i do Q2 lin tc bo ha/kha. in p nyc nn/lc ly ra in p standby.ng 1 : Nn bi D30 ra 12V nui dao ng, khuych i kch thch.ng 2 : Nn bi D29, lc C23 v n p bng IC 7805 ly ra 5V cho dy tm, h p qua tr cho PS-ON, nui mch thut ton to PG.

Cc h hng:Hin tng 1: N cu ch, thay li n.- Chp Q12, hoc Q12 b thay bng BJT in p thp, cm in vo s thng lun. i vi ngun ny,tn s dao ng 13kHz, Q12 c th dng C2335, 13007 l OK.Lu : Vi ngun i mi, tn s 19Khz khng s dng C2335 c nh (v in p Uce max caC2335 thp)

Hin tng 2: in p standby mt.Mt dao ng do :- t in tr mi (R5/56).- t D28 lm mt hi tip.- Kh, t, thi chn C19 khng lc san bng, hi tip b xung lm ZD2 kha.

- t hoc thay sai gi tr ZD2 lm mt hi tip.Hin tng 3: Mt 5V STB- t D29, 7805- Chp C23

Hin tng 4 : p standby suy gim- Thng, r diode nn.- T lc kh.

Dng 2 : Hi tip gin tip

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Mch c cp ngun 300Vdc t mch nn/lc s cp.

Tc dng linh kin:

Rhv : in tr hn ch, in p ra sau n cn khong 270V.

R3, R5 : nh thin (mi) cho Q3.

Q3 : Cng sut standby, y dng Mosfet 2N60.

R4 : To hi tip m in p, s dng st p trn R4 nh mt sensor kim tra dng qua Q3, thngqua s iu chnh Q3 hot ng n nh.

ZD1 : n nh in p chn G, nhm bo v khng Q3 m ln, trnh cho Q3 b nh thng.

C34 : T nht, bo v Q3 khng b nh thng khi chu in p m cc ln ca thi k qut ngc.

R9 : in tr phn p, to s n nh (tng i) cho chn G Q3 v C Q4.

L1 : Ti Q3. L2 : Cun hi tip.

Q4 : Mc phn p cho chn G Q3, ng vai tr o pha in p hi tip.

D5 : Nn hi tip theo kiu mch nn song song nhm to in p (+) im A.

C8 : Lc in p hi tip.U1 : Mch so quang, hi tip m n nh in p STB.

R17 : in tr nng cao mc thp, vi mc ch ngt in p hi tip ti chn B Q4 khi in p nygim xung cn ~ 2V.

C4, R6, D3 : Kh in p ngc, chng ngt dao ng.

Nguyn l:

in p 300V t mch nn/lc s cp qua Rhv cn ~270V cp cho mch. in p ny chia lm 2

http://lqv77.com/wp-content/uploads/2009/06/stbblockinggt.jpg

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ng :

ng 1 : Vo im PN6, ra PN4 ti chn D Q3.

ng 2 : Qua R3, R5 kt hp phn p R9 nh thin cho Q3, ng thi cp cho Q4 (chn C). Cc bnhy Q4 mc phn p cho G Q3 nn nu Q4 bo ha th in p ti G Q3 ~ 0, Q3 kha.

Nh nh thin (mi) bi R3, R5 nn Q3 m. Dng in i t 270V qua L1, qua DS Q3 xung mass,

kn mch. V dng ny i qua L1, theo c tnh ca cun cm (lun sinh ra dng chng li dng quan theo hin tng cm ng in t) nn dng qua L1 khng t mc bo ha ngay m tng ln t t.V vy t trng sinh ra trn li bin p STB cun tng t t (t trng ng).

Theo nh lut cm ng in t Lenz, t trng tng t t trn li bin p STB s lm pht sinh trn ttc cc cun dy ca bin p 1 sut in ng cm ng.

in p cm ng trn L2 c nn bi D5 v lc bng C8 ly ra in p 1 chiu cc tnh m (+) im A, c n nh (tng i) bng R16, n nh ph thuc vo tch s T = R16xC8 (thi hng hng s thi gian tch thot ca mch RC)

in p ti im A li qua CE U1 (so quang) ti chn B ca Q4. V l in p dng nn n lm choQ4 bo ha. Khi Q4 bo ha th in p ti chn C Q4 ~ 0, m chn C Q4 li ni vo chn G Q3 nn

UgQ3 ~ 0 lm cho Q3 kha.Khi dng qua Q3 kha, dng qua L1 mt i, t trng trn L1 cng mt i lm cho t trng trn libin p = 0 dn n in p cm ng trn cc cun day bin p STB = 0. D nhin in p cm ng trncun L2 mt.

V in p trn L2 mt nn khng a ra p (+) ti im A na. Tuy vy v c C8 np (lc trc) nngi n x lm cho in p ti im A ko mt ngay, vic C8 x s duy tr mc (+) chn B Q4 thm 1thi gian na v Q4 tieps tc bo ha, Q3 tip tc kha. Ti khi in p (+) do C8 x ko ln (2V)th R17 s ngt in p hi tip, chn B Q4 s gim v O, Q4 kha. Khi Q4 kha th in p nh thindo R3, R5 c phc hi v Q3 li m. Mt chu trnh m/kha li bt u.

Tn s dao ng ca mch:

c quyt nh bi L2/C8/R16. y l cng hng ni tip nn khi xy ra cng hng th in ptrn L2 l max, khi dng in p ti im A l max cho R17 dn, Q4 bo ha. Nu mt cnghng th in p trn L2 min, in p im A min khng thng li st p trn R17 lm Q4 kha, Q3m (c nh) v dng qua L1 s l c nh ko to ra c t trng ng lm in p cm ng trn ttc cc cun ca bin p STB mt i. Ni cch khc th tn s dao ng ca mch chnh bng1/2xsqrt(L2xC8R16).

Thc t, khi Q3 kha, dng qua L1 ko mt ngay do t trng trn li bin p vn cn (nh) lm xuthin in p cm ng trn L1 vi chiu (-) D Q3 ,in p ny tn ti trong thi gian cc ngn (gingnh qut ngc cng sut dng tivi, CRT) nn c gi tr rt ln (~ 800V vi ngun i mi) lm phtsinh 2 hu qu :

Tc dng ca C4, R6, D3 ging nh mch hi tip trc tip.

in p cm ng trn L3 c sinh ra nh t trng bin i do Q2 lin tc bo ha/kha. in p nyc nn/lc ly ra in p standby.

ng 1 : Nn/lc bi D9/C15 ra 12V nui dao ng, khuych i kch thch.

ng 2 : Nn/lc bi D7/C13/C18 5V cho dy tm, h p qua tr cho PS-ON, nui mch thut tonto PG.

n nh in p : S dng OPTO U1.

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Nu in p ra tng (v tn s dao ng thay i) th ngun ra 5V tng ln. Khi ngun cp cho cciu khin ca U1 (TL431) t 5V qua R27 tng ln lm cho 431 m ln.

thy 431 mc ni tip vi diode pht ca OPTO, v 431 m ln nn dng qua diode (t 5V STBqua R30, qua diode, qua 431 xung mass) tng ln, cng sng ca diode tng tc ng ti CE U1lm in tr Rce U1 gim, in tr ny li mc ni tip t im A v R17 nn lm cho in p hi tipv B Q4 (qua R17) tng ln, kt qu l Q4 bo ha/Q3 kha sm hn thng l. Ni cch khc th thi

gian m ca Q3 trong 1 giy nh s gim xung lm in p ra gim.Nu in p ra gim (v tn s dao ng thay i) th ngun ra 5V gim. Khi ngun cp cho cciu khin ca U1 (TL431) t 5V qua R27 gim ln lm cho 431 m nh.

thy 431 mc ni tip vi diode pht ca OPTO, v 431 m ln nn dng qua diode (t 5V STBqua R30, qua diode, qua 431 xung mass) gim xung, cng sng ca diode gim tc ng ti CEU1 lm in tr Rce U1 tng, in tr ny li mc ni tip t im A v R17 nn lm cho in p hitip v B Q4 (qua R17) gim xung, kt qu l Q4 bo ha/Q3 kha mun hn thng l. Ni cchkhc th thi gian m ca Q3 trong 1 giy nh s tng ln lm in p ra tng.

n nh in p : S dng in tr hi tip m in p R4.

Nu Q3 m ln (lm p ra cao) th dng qua R4 tng. St p trn R4 (tnh bng UR4 = IQ3 x R4) tngln. s thy st p ny a v chn B Q4 qua R8 lm Ub Q4 tng, Q4 s bo ha, Q3 kha smhn thng l. Ni cch khc th thi gian m ca Q3 trong 1 giy nh s gim xung lm in p ragim.

Nu Q3 m nh (lm p ra thp) th dng qua R4 gim. St p trn R4 (tnh bng UR4 = IQ3 x R4)gim xung. s thy st p ny a v chn B Q4 qua R8 lm Ub Q4 gim, Q4 s bo ha, Q3kha mun hn thng l. Ni cch khc th thi gian m ca Q3 trong 1 giy nh s tng ln lm inp ra tng.

1 - Chc nng ca ngun Stanby - Ngun cp trc .

Ngun Stanby (ngun cp trc) c chc nng cung cp in p 12V cho IC dao ng ca ngun chnh v cungcp in p 5V STB cho mch khi ng ngun trn Mainboard.

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S cp in ca ngun Stanby Khi cp in cho ngun ATX, mch ngun Stanby hot ng ngay v cho ra hai in p

- in p 12V cung cp cho IC dao ng ca ngun chnh.- in p 5V cung cp ra chn 5V STB a xung Mainboard cung cp cho mch khi ng (mch khi ngtch hp trong cc IC - Chipset nam v SIO )

2 - Mt s c im ca ngun Stanby

1. Cng sut:- Ngun Stanby thng c cng sut nh khong 5 n10W, n c nhim v cung cp in p cho mch khi ngtrn Mainboard v IC dao ng trn b ngun ATX.

2. Ph ti ca ngun Stanby:

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- Ph ti ca ngun Stanby l IC dao ng ca ngun chnh trn b ngun v mch khi ng ngun tch hp trnhai IC l Chipset nam v SIO trn Mainboard

3. Thnh phn ca ngun Stanby:Ngun Stanby bao gm cc thnh phn (theo s di y)

- n cng sut (Q3)- Bin p xung (T3)- IC khuch i in p ly mu (U2)- IC so quang (U1)- n sa sai (Q4)- R, C tham gia dao ng. (R7, C10)- Mch bo v qu dng (R4, R8)

4. c im nhn bit linh kin ca mch ngun Stanby trn b ngun:

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Nhn bit linh kin:- Bin p ca ngun Stanby nh v lun lun ng bn cnh (nh hnh bn)- n cng sut ca ngun Stanby thng ng bn cnh bin p Stanby- Cc linh kin khc ng xung quanh hai linh kin trn.

3 - Nguyn l hot ng ca ngun Stanby.

1. Mch to dao ng .Mch dao ng bao gm cc linh kin- in tr mi (R3, R4)- n cng sut (Q3)- R, C hi tip (R7, C10)

- Cun s cp- Cun hi tip

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Nguyn l hot ng ca mch dao ng:- Khi c in p 300V DC i vo mch ngun, mt nhnh in p i qua cun so cp vo ch chn D ca ncng sut.- Mt dng in nh i qua R mi (R3, R5) vo nh thin cho chn G ca n cng sut, n cng sut ban udn yu, dng in i qua cun s cp tng dn (bin thin) s cm ng ln cun hi tip.- Chiu dng ca in p hi tip c np qua t C10, hn ch dng qua R7 a v lm in p chn G n cngsut tng ln => n cng sut dn mnh => in p hi tip mnh hn => c nh vy v n cng sut nhanhchng t n im bo ho (dng qua cun s cp khng i) => in p cm ng trn cun hi tip b mt tngt => t C10 x in lm cho chn G gim nhanh => n cng sut chuyn sang trng thi ngt.- Qu trnh trn lp i lp li v to thnh dao ng.- n cng sut va l thnh phn tham gia dao ng ng thi cng l thnh phn khuch i dao ng tora dng in chy qua cun s cp => cm ng sang cc cun th cp cho ta in p ra.Lu :- C dao ng th c in p th cp u ra, khng c dao ng th in p th cp s ra bng 0V- Nu ch c mch dao dng thi th in p ra s bin i theo in p u vo, tc l in p vo tng th in pra cng tng, in p vo gim th in p ra cng gim.- gi cho in p ra c nh, ngi ta phi thit k thm mch hi tip, nguyn l mch hi tip nh sau:

2. Mch hi tip n nh in p ra.Mch hi tip bao gm cc linh kin- Mch ly mu (gm cc in tr R27, R19)- IC khuch i in p ly mu (U2) s dng KA431- IC so quang (U1)- n sa sai (Q4)

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Nguyn l hot ng ca mch- Mch hi tip trn c tc dng gi cho in p ra c c nh, mc d in p vo thay i hoc dng tiu ththay i, nguyn l hot ng ca mch nh sau:- Gi s khi in p vo tng ln, in p u ra c xu hng tng theo => in p 5VSB tng nh => thng quacu phn p R27, R19 th in p ly mu cng tng nh => IC KA431 (U2) s khuch i in p ny ln thnhdng i qua i t trong IC so quang (U1) tng => n thu quang trong IC so quang dn tng => in p a vchn B n Q4 tng => Q4 dn mnh => lm cho in p chn G n Q3 gim xung, n Q3 hot ng yu i =>lm cho in p ra gim xung.- Khi in p vo gim xung th qu trnh iu chnh tng t nhng din ra theo chiu hng ngc li.

in p vo bin i ti 50V nhng in p ra ch thay i khong 0,1Vv rt nhanh n quay v v tr ban u

3. Mch bo v qu dngMch bo v qu dng c tc dng bo v n cng sut khi n lm vic qu ti, mch c thit k rt n ginbao gm:- Ngi ta lp thm in tr R4 (RS) u t chn S ca n cng sut xung Mass to ra in p bo v, sau in p ny c a qua mt in tr (R8) sang chn B ca n sa sai Q4

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Nguyn l hot ng- Khi ngun hot ng bnh thng th dng in i qua n cng sut khong 0,1A khi st p trn in tr R4khong 0,2V in p ny khng lm cho n Q4 dn.- Khi ngun c s c (v d chp ph ti u ra), khi n cng sut hot ng mnh, dng in qua n tng caolm cho st p trn R4 tng theo => khi in p ny tng > 0,6V a qua R8 sang lm cho n Q4 dn bo ho =>kt qu l chn G ca n cng sut (Q3) b u tt xung mass => n cng sut tm ngt v n c bo v anton, sau khi n ngt => mch dao ng tr li v cho in p ra => v mch bo v li hot ng => li ngt ncng sut. qu trnh c lp i lp li nh th tr thnh t kch (in p ra c li mt theo mt nhp khong 1 giy/ln)

4 - Tr li cu hi lin quan n ngun Stanby1. Cu hi 1 - Trn mch ngun Stanby c nhng mch c bn no ?Tr li:

Trn ngun Stanby ca ngun ATX ni ring v trn cc ngun xung ni chung c ba mch c bn sau y:- Mch to v duy tr dao ng- Mch hi tip n nh in p ra- Mch bo v qu dng

2. Cu hi 2 - Chc nng ca cc mch trn l g ?Tr li:- Mch dao ng c chc nng to v duy tr dao ng iu khin n cng sut hot ng ch ngt m, t to ra dng in bin thin chy qua cun s cp v ta thu c cc in p cm ng trn cc cun th cp, numt dao ng th s mt in p ra.- Mch hi tip n nh in p ra c chc nng gi cho in p ra khng thay i khi in p vo thay i hockhi dng tiu thu ca ph ti thay i.- Mch bo v qu dng c chc nng bo v n cng sut khng b hng khi cc ph ti b chp.

3. Cu hi 3 - Ngun Stanby c nhng h hng g v cho bit nguyn nhn ca n.

Tr li:Ngun Stanby ni ring v cc ngun xung c nguyn l tng t ni chung tng c 3 bnh sau y:- Mt in p ra (tc in p ra bng 0V)- in p ra sai (tng ln hay gim xung thp hn gi tr ban u)- in p ra gim thp v t kch (nu o th thy kim ng h dao ng)* Nguyn nhn ca hin tng mt inp ra (p ra bng 0V) l do ngun b mt dao ng.- Do mt in p 300V u vo- Do t in tr mi

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- Do t hoc bong chn R hoc C hi tip- Do hng n cng sut.- Do t in tr bo v t chn S xung mass- Do chp n sa sai

Cc linh kin trong vng trn trn b hng s lm mt dao ng* Nguyn nhn ca hin tng in p ra tng hoc gim so vi ban u.- Do cc in tr ca mch ly mu b tng tr s- Do hng IC khuch i in p ly mu KA431- Do hng IC so quang

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Cc linh kin trong vng trn trn b hng s lm cho in p ra sai hoc t kch* Nguyn nhn ca hin tng in p ra t kch (o thy kim dao ng)- Do ph ti b chp- Do chp i t chnh lu in p ra- Do t in tr thot mass ca mch ly mu- Do chp IC khuch i in p ly mu KA431

Cc linh kin trong vng trn trn b hng s lm cho in p ra b t kch4. Cu hi 4 - Lm th no kim tra xem ngun Stanby c hot ng hay khng v nu khng hot ng th

c hin tng g nh trn ?Tr li

* kim tra xem ngun Stanby c hot g hay khng, bn lm nh sau:- Cp in cho b ngun- Chnh ng h thang 10V DC, que en t vo mt si dy en, que t vo si dy mu tm (dy mu tml in p 5V STB), quan st ng h xem in p c bao nhiu vol ?=> Nu c in p 5V ra th ngun Stanby hot ng tt=> Nu mt in p 5V ra th ngun Stanby b hng. * kim tra xem ngun Stanby b hng bnh g th bn kimtra nh sau:- Tho v my ca ngun ATX ra ngoi- Chnh ng h thang 10V DC- o in p u ra, o trn cc t lc trn ng in p ra 12V hoc 5V sau i t chnh lu(nu o 5V trn dy mu tm xc nh bnh c th khng chnh xc v nhiu b ngun, in p ny i quaIC n p)

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o vo u cc t lc (trong vng trn s trn) bn s bit in p rabng 0 hay in p ra tng, gim hoc t kch.

5. Cu hi 5 - Cho bit phng php sa ngun Stanby mt cch nhanh nht. Tr li: sa nhanh mch ngun Stanby bn hy thc hin theo lc sau y: