[Codientu.org]_Nguon ATX Toan Tap

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http://tudonghoak30.6x.to Ngun t http://lqv77.com

B ngun ATX ton tp: Mch cp trc dng 1 ng ngy 26/06/2009 bi: lqv77

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

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

Mch c cp ngun 300Vdc t mch nn/lc s cp. Tc dng linh kin :

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Q12 : Dao ng blocking, ng thi l cng sut stanby. R55/R56 : nh thin cho Q12, ng vai tr l in tr mi D23 : 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 bng cng thc : f = 1/2xsqrt(L2xC3). Cc bn c th thc mc v iu ny, tuy nhin i vi tn hiu xoay chiu th (+) ngun v mass coi nh chp (thng qua cc t lc) v vy i vi xoay chiu th R55/C3 coi 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 hi tip) 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. V dng ny i qua L1, theo c tnh ca cun cm (lun sinh ra dng chng li dng qua n 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 tt c 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 p dng do nh thin R55/56 a ti, kt qu l 2 in p ny trng ha ln nhau lm cho in p chn B Q12 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 dn n 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 n x lm cho in p ti im A ko mt ngay, vic C19 x s duy tr mc m chn B Q12 thm 1 thi 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 m bo ha. Mt chu trnh bo ha/kha li bt u.

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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 cch khc 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 xut hin 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 lm cho ip p m (-) v B Q12 cng duy tr v ko th phc hi c in p nh thin (+) v nh vy chu 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 ln nhau. 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) v nguyn 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 ny c 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 ca C2335 thp) Hin tng 2: in p standby mt. Mt dao ng do : - t in tr mi (R5/56). - t D28 lm mt hi tip.

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- 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.

Ngun ATX: Cch kim tra ngun c hot ng khng ng ngy 03/03/2009 bi: lqv77 Kim tra xem b ngun c hot ng hay khng ?

o Chp chn lnh P.ON xung Mass (dng si thic u dy mu xanh l cy vo mt dy mu en) o Cp in cho b ngun v quan st qut o Nu qut quay tt l ngun hot ng tt

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Ngun ATX: C 5V tm cp trc, kch khng chy ng ngy 02/03/2009 bi: lqv77 Phn tch nguyn nhn. V in p cp trc vn c 5V nn ta suy ra.

o in p u vo 300V DC vn c, cc linh kin u vo tt o Ngun cp trc hot ng tt o Cc n cng sut ca ngun chnh khng b chp

V vy hin tng h hng trn l do nhng nguyn nhn sau y. o Mch bo v ca ngun chnh b hng hoc hng IC bo v (khng

a c lnh P.ON n chn IC dao ng) o Mt trong cc n khuch i o pha b chp CE o IC dao ng ca ngun chnh b hng o Mt hoc c hai n cng sut b bong mi hn

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Phng php kim tra & sa cha * Kim tra xem cc n cng sut c b bong mi hn khng ?

* D ngc t chn bin p o pha v pha IC dao ng tm hai n khuch i o pha, kim tra cc n o pha nu b chp CE th bn thay n mi, nu n tt th kim tra tip IC dao ng nh sau:

Nu IC dao ng hot ng tt th s cho ra cc ch in p nh sau:

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in p ca cc n o pha khi ngun ch ch (khi lnh P.ON c mc cao)

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in p ca cc n o pha khi ngun ch hot ng (khi lnh P.ON c mc thp = 0V)

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Cc bc sa cha c th 1) Tm thi u chp chn B v E ca hai n cng sut li ( kho khng cho hai n hot ng)

(Lu - khi p cho IC dao ng hot ng, khi mch bo v mt tc dng, v vy kho hai n cng sut l trnh trng hp ngun b chp ti s cht n cng sut)

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Hn chp chn B vo chn E ca hai n cng sut kho li khi p cho IC dao ng chy u chp chn (4) ca IC dao ng xung mass p cho IC dao ng, sau o kim tra cc ch in p ri i chiu vi s di y.

o Chn 8 v chn 11 ca IC - TL494 phi c 2,2V o Chn C hai n o pha c khong 2,2V o Chn E hai n o pha c khong 1,6V

=> Nu cc gi tr in p ng nh trn th IC vn hot ng, nu cc ch in p b sai i l IC dao ng b hng

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o Tm thi u chp chn B v E ca hai n cng sut li ( kho khng cho hai n hot ng) o u chp chn s (4) ca IC dao ng TL494 xung mass ( p cho IC hot ng) o o in p xung quanh cc n o pha phi c gi tr nh trn l IC tt, ngc li l IC dao ng hng

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o Thay IC dao ng (nu cc ch in p b sai vi s trn) o Thay IC bo v (nu in p u ra ca IC dao ng vn bnh thng)

Mt s cu hi thng gp Cu hi 1 - Khi ngun ch ch Stanby v sao hai n o pha vn c in p a vo chn B Tr li: Cc ngun ATX hin nay u c thit k theo nguyn tc - khi ch Stanby, IC dao ng a ra in p mt chiu khin cho cc n o pha dn bo ho (c dng khong 6mA i qua n) lc ny dng in i qua hai cun dy s cp ca bin p c pha ngc nhau nn t trng b trit tiu, v vy in p a ti chn B cc n cng sut bng 0V. Cu hi 2: V sao phi chp chn B vo chn E kho cc n cng sut khi chp chn s (4) ca IC dao ng xung mass Tr li: - Khi chp chn (4) ca IC dao ng xung mass, IC s cho ra dao ng k c khi ngun c s c nh qu dng hay qu p, v vy nu ta khng kho hai n cng sut th c th lm cho cc n cng sut b hng nu bn th cp b chp.

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- Trng hp bn kim tra k cc i t chnh lu u ra m khng b chp, bn c th nguyn cho n cng sut hot ng, nu khi chp chn (4) ca IC dao ng xung mass m ngun chnh hot ng v cho in p ra bnh thng th bn suy ra => mch bo v c s c, v vy khng a c lnh P.ON ti chn IC dao ng.

Cu hi 3: Nu mt trong hai n khuch i o pha b chp CE th ngun chnh c hot ng khng ? Tr li: Nu mt trong hai n khuch i o pha b chp CE th ngun chnh khng hot ng c, khi qut ngun khng quay, in p ra bng 0

Cu hi 4: Nu mt n khuch i o pha b bong mi hn hoc khng hot ng th ngun chnh c hot ng khng ? Tr li: trng hp ny vn c mt n khuch i o pha hot ng, v vy vn c mt n cng sut hot ng nn in p ra vn c, tuy nhin ngun s b st p khi c ti tiu th.

Cu hi 5: Hng dn cch kim tra IC dao ng TL494 Tr li: kim tra IC dao ng TL494 bn cn kim tra cc thng tin sau y: - in p cung cp vo chn (12) phi c t 10 n 12V, nu in p ny thp hn th c th IC b chp hoc ngun Stanby ra thiu in p. - Khi c in p vo chn (12) th IC phi cho ra in p Vref = 5V chn (14), nu khng c in p ny th IC b hng. - Khi ta u lnh P.ON (dy mu xanh l cy) xung mass th chn (4) ca IC - TL494 phi c in p bng 0 kch hot cho dao ng ra, nu chn (4) c in p > 0 th do hng mch bo v ph trc hoc hng IC - LM339 - Ta c th u chp chn (4) xung mass p cho IC dao ng hot ng, khi u chp chn (4) xung mass nu khng kho cc n cng sut th bn cn kim tra k cc i t chnh lu in p ra. * Sau khi c cc iu kin nh:

o C 12V chn (12) o C 5V chn (14) o C 0V chn (4)

- Th IC s c dao ng ra, kim tra dao ng ny bn hy kim tra ch in p ca cc n o pha - Nu c hai n o pha c in p nh sau:

o o ti chn B n (tc chn 8 hoc chn 11 ca IC c khong 2,2V DC o o ti chn E n c khong 1,6V DC

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o o ti chn C ca n c khong 2,2V DC => Th suy ra l IC dao ng cho tn hiu dao ng ra bnh thng Nu ch in p ca mt hoc c hai n o pha ra b sai so vi in p trn l IC dao ng b hng.

Cu hi 6: Ta c th o c in p dao ng ti chn n cng sut khng, nu cc n cng sut khng hot ng th dao ng ny c duy tr khng? Tr li: - Nu c dao ng ra iu khin chn B n cng sut m cc n ny khng hot ng (v d n hng hoc ta tho hai n cng sut ra ngoi) th dao ng ny ch tn ti 1- 2 giy ri tt, nguyn nhn l do khi khng thy c in p ra => mch bo v s hot ng v ngt dao ng. - dao ng ny duy tr khi n cng sut khng hot ng (hoc khi bn tho hai n cng sut ca ngun chnh ra ngoi) th ta phi u chn (4) ca IC dao ng TL494 xung mass - Dao ng o c gia B v E ca cc n cng sut (khi tho cc n cng sut ra ngoi v chp chn 4 ca IC dao ng TL494 xung mass) l khong 0,2V, thc t th bin dao ng ny cao hn nhng khi ta o bng ng h thng thng th chng bo khng chnh xc do dao ng ny c tn s rt cao khong vi chc KHz

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B ngun ATX ton tp: Mch cp trc dng 2 ng ngy 28/06/2009 bi: lqv77

o Tng quan v ngun ATX o Mch lc xoay chu v mch nng lc s cp o Mch cp trc dng 1

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, thng qua 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 ny gim 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 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 bn hy 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 qua n 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 tt c 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)

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in p ti im A li qua CE U1 (so quang) ti chn B ca Q4. V l in p dng nn n lm cho Q4 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 li bin p = 0 dn n 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 khng a ra p (+) ti im A na. Tuy vy v c C8 np (lc trc) nn gi n x lm cho in p ti im A ko mt ngay, vic C8 x s duy tr mc (+) chn B Q4 thm 1 thi 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 thin do 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 p trn L2 l max, khi dng in p ti im A l max cho R17 dn, Q4 bo ha. Nu mt cng hng th in p trn L2 min, in p im A min khng thng li st p trn R17 lm Q4 kha, Q3 m (c nh) v dng qua L1 s l c nh ko to ra c t trng ng lm in p cm ng trn tt c cc cun ca bin p STB mt i. Ni cch khc th tn s dao ng ca mch chnh bng 1/2xsqrt(L2xC8R16). Thc t, khi Q3 kha, dng qua L1 ko mt ngay do t trng trn li bin p vn cn (nh) lm xut hin in p cm ng trn L1 vi chiu (-) D Q3 ,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 : 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 ny c 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 ton to PG. n nh in p : S dng OPTO U1. Nu in p ra tng (v tn s dao ng thay i) th ngun ra 5V tng ln. Khi ngun cp cho cc iu 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 STB qua R30, qua diode, qua 431 xung mass) tng ln, cng sng ca diode tng tc ng ti CE U1 lm in tr Rce U1 gim, in tr ny li mc ni tip t im A v R17 nn lm cho in p hi tip v 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 cc iu khin ca U1 (TL431) t 5V qua R27 gim ln lm cho 431 m nh.

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thy 431 mc ni tip vi diode pht ca OPTO, v 431 m ln nn dng qua diode (t 5V STB qua R30, qua diode, qua 431 xung mass) gim xung, cng sng ca diode gim tc ng ti CE U1 lm in tr Rce U1 tng, in tr ny li mc ni tip t im A v R17 nn lm cho in p hi tip v B Q4 (qua R17) gim xung, kt qu l Q4 bo ha/Q3 kha mun hn thng l. Ni cch khc 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) tng ln. s thy st p ny a v chn B Q4 qua R8 lm Ub Q4 tng, Q4 s 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 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, Q3 kha mun hn thng l. Ni cch khc th thi gian m ca Q3 trong 1 giy nh s tng ln lm in p ra tng.

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B ngun ATX ton tp: Mch lc xoay chiu, nn lc s cp ng ngy 25/06/2009 bi: lqv77

3. PHN TCH MCH IN 3.1. Mch lc xoay chiu, nn lc mt chiu s cp :

Tc dng linh kin : F1 : Cu ch bo v qu dng, khi c hin tng chm chp trong b ngun lm cho dng qua F1 tng, dy ch ca n s chy, ngt ngun cp bo v cc linh kin khng b h hng thm. TH1 : Cu ch bo v qu p, c cu to l 1 cp tip gip bn dn, in p ti a trn n khong 230V-270V (ty loi ngun). Khi in p vo cao qu hoc st nh dn n in p t trn TH1 tng cao, tip gip ny s t ngt in p cp cho b ngun. CX1, CX2 : T lc u vo, lm chp mch cc xung nhiu cng nghip tn s ln. LF1 : Cun cm, ngn chn xung nhiu tn s ln khng cho lt vo ngun.

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RV/C3/C3 : Mch lc kiu RC to ng thot cho xung cao tn. D1-D4 : Mch nn cu, bin i in p xoay chiu ca ngun cung cp thnh in p mt chiu. C5/C6 : T lc ngun, san bng in p sau mch nn. R1/R2 : in tr cn bng in p trn 2 t. SW1 : Cng tc thay i in p vo. 220 ngt, 110V - ng Dng xoay chiu i qua cu ch, cc xung nhiu b loi bt bi CX1/LF1 ti RV. Mch lc bao gm RV/C3/C4 s tip tc loi b nhng can nhiu cng nghip cn st li. Ni cch khc th dng xoay chiu n cu nn sch hn. V dng xoay chiu l lin tc thay i nn in p vo cu nn s thay i. V d bn k 1 A(+)/B(-), bn k 2 A(-)/B(+) Nu in p vo l 220V (SW1 ngt). Khi A(+)/B(-) th diode D2/D4 c phn cc thun, dng in i t im A qua D2, np cho cp t C5/C6, qua ti xung mass, qua D4 tr v im B, kn mch. Khi A(-)/B(+) th th diode D1/D3 c phn cc thun, dng in i t im B qua D3, np cho cp t C5/C6, qua ti xung mass, qua D1 tr v im A, kn mch. Nh vy, vi c 2 bn k ca dng xoay chiu u to ra dng in qua ti c chiu t trn xung. in p t ln cp t s c chiu dng (+) im C, m (-) im D (mass). Gi tr in p trn C5/C6 l : - (220V-20.7) x sqrt2= 309,14V (nu dng diode silic, st p trn mi diode ~0.7V) - (220V-20.3) x sqrt2= 310,27V (nu dng diode gecmani, st p trn mi diode ~0.3V) Nu in p vo l 110V (SW1 ng) Khi A(+)/B(-) th D2 c phn cc thun, dng in i t im A qua D2, np cho C5, v B kn mch. Gi tr in p trn C5 l : 110V-x0.7)x sqrt2= 154,57V (do ch st p trn 1 diode) Khi A(-)/B(+) th D1 c phn cc thun, dng in i t im B np cho C6, qua D1 v A kn mch. Gi tr in p trn C6 l : (110V-x0.7)x sqrt2= 154,57V (do ch st p trn 1 diode). Tng in p trn C5/C6 s l : 154,57 x 2 = 309,14V y chnh l ngun 1 chiu s cp cung cp cho ton mch ngun, cc bn th quen gi in p trn im A l in p 300V, d nhin gi vy l cha chnh xc v mt gi tr. Cc h hng trong mch : Hin tng 1 : t cu ch - Do qu p, st nh. Thay ng chng loi. Hin tng 2 : t cu ch, thay vo li t. - Do chp 1, 2, 3 hoc c 4 diode nn cu. Khi o in tr thun/ngc ca chng u ~0. Thay. - Do chp 1 trong cc t lc. o s thy tr khng ca chng bng 0, thay. Tuy nhin, nguyn nhn ny cc k t xy ra (xc

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sut 1%). Lu : 1 s ngun cn c ng phng li (hnh dng nh t gm) bo v qu p mc song song sau cu ch F1, khi st nh hoc in p cao th n s chp lm tng dng v gy t cu ch F1. Nu ngun s dng kiu bo v ny th ta phi o kim tra, tr khng bng 0 th thay. Hin tng 3 : in p im A thp, t 220V-250V. - Do 1 hoc c 2 t lc b kh. Thay. Khi t kh thng s km theo hin tng my khng khi ng hoc khi ng nhng reser, treo do ngun vo lc c lc ko k, cn xoay chiu dn n ngun ra b gn.

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B ngun ATX ton tp: Tng quan v ngun xung v ngun ATX ng ngy 25/06/2009 bi: lqv77

o Mch cp trc dng 2 o Mch cp trc dng 1 o Mch lc xoay chiu, nn lc s cp

1. NGUYN L NGUN XUNG 1.1. Khi nim : - Mch ngun xung (cn gi l ngun ngt/m - switching) l mch nghch lu thc hin vic chuyn i nng lng in mt chiu thnh nng lng in xoay chiu. 1.2. Cc s nghch lu : C 2 dng nghch lu c bn : ni tip v song song. 1.2.1. S nghch lu ni tip

u im : n gin, d tnh ton thit k, d lp rp. Nhc im : Cho php dung sai linh kin rt thp. Khng cch ly c mass s cp v th cp nn gy git cho ngi s dng, gy nguy him cho cc linh kin nhy cm. Chnh v vy ngun kiu ny hin nay rt t c s dng. Mt trong nhng thit b in t dn dng c nhiu Vit nam s dng ngun nghch lu ni tip l my thu hnh Samsung CW3312, Deawoo 1418. 1.2.2. S nghch lu song song :

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u im : D thay i in p ra, cho php dung sai linh kin ln. Mass s cp v th cp c cch ly tt, an ton cho ngi s dng v ti. Nhc im : Mch phc tp, kh sa cha Do kh nng cch ly tt nn mch nghch lu song song c dng trong tt c c cc b ngun my tnh, t AT n ATX. Lot bi ny s tp trung phn tch mch nghch lu song song trong ngun ATX. 2. NGUN MY TNH (ATX) 2.1. Chc nng : Bin i ngun xoay chiu dn dng ( Vit Nam l 220v/50Hz, Nht Bn l 110V/60Hz ) thnh cc in p mt chiu cung cp cho PC. Cc mc ngun mt chiu ra bao gm : +5V, +12V, +3.3V, -5V, -12V, +5V STB (standby cp trc, ch), +4.5-5V PS-ON (Power Switch On cng tc m/bt ngun), +5V PG (Power Good Ngun tt, tn hiu ng b cho tt c cc mch in trong PC cng khi ng). 2.2. S khi ngun ATX

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2.3. Chc nng cc khi : (1) Bo v ngun v ti khi b st nh, khi in p vo tng t ngt. Lc, loi b hoc gim thiu cc xung nhiu cng nghip thng qua ngun AC i vo mch ngun ATX, nu nhng nhiu ny khng c loi b c th gy chy n mch ngun, ti, gim n nh khi ti lm vic. (2) Ngt m theo xung kch thch, nhm to ra dng in khng lin tc trn bin p chnh li dng hin tng cm ng in t to ra in p cm ng trn th cp. (3) L ti ca cng sut chnh, to in p ra th cp, ng thi cch ly gia 2 khi s/th cp loi b mass (in p cao) ca s cp bo v ti v ngi s dng. (4) L mt mch nghch lu cng sut nh, c th dng dao ng ring hoc blocking (5) L ti ca cng sut cp trc, nhm to ra in p cp trc gm 2 mc : 5V, 12-16V cung cp cho dao ng, PS-ON, STB v khuych i kch thch. (6) Nn, lc, n p a ra cc in p mt chiu standby.

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(7) L mt mch dao ng RC nhm to ra xung vung c tn s c nh (cc ngun i c c tn s 13KHz, ngun i mi l 19KHz). Xung ny c gi ti iu khin cng sut chnh ng/m. Xung ra t dao ng c rng xung (tx) bin i theo in p ra, nu in p ra cao hn thit k th rng xung gim xung. Ngc li, nu in p ra gim thp hn thit k th rng xung tng ln. V vy IC thc hin dao ng c tn l PWM (Pulse Wide Modulation iu khin rng xung) (8) Khuych i tng cng bin xung iu khin. u vo ca mch chnh l xung vung ra t mch dao ng. (9) L ti ca mch khuych i dao ng kch thch vi mc ch ghp xung kch thch sang cng sut chnh, ng thi khng lm mt i s cch ly gia phn s cp, th cp. (10) Bao gm cc mch nn, lc, n p. u vo l in p xoay chiu ly ra t bin p cng sut chnh, u ra l cc mc p mt chiu n nh a n jack ATX. (11) Mch hi tip n nh in p hoc ngt dao ng khi in p ra qu ln, ngt dao ng khi c chp ti bo v mch ngun cng nh bo v ti (trnh h hng thm) (12) Mch khuych i thut ton, s hot ng sau khi my c bt, to ra in p PG, thi im xut hin PG s tr hn cc in p chnh khong 0.2-0.5 giy, nhm ch cho cc in p ra n nh. PG a vo main v kch thch tt c cc mch trn main bt u hot ng cng 1 thi im (ng b thi im gc)

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Ngun ATX: Ngun st p ng ngy 04/03/2009 bi: lqv77

Nu: Ngun kim tra ri chy OK, o p y 5V, 12V, 3.3V u OK nhng khi cm vo main th khng boot hoc ln ri tt. o p khi cm v main th thy thiu > Ngun b st p. Phn tch nguyn nhn ca hin tng trn.

Vi hin tng trn qut ngun quay bnh thng, chng t cc mch ca ngun hot ng tt, IC dao ng tt, mch bo khng hot ng nn khng sy ra qu dng hay qu p. - in p 300V DC u vo c, cc linh kin u vo nh cu ch, cu i t, tr nhit vn tt - Cc n cng sut khng b chp (k c ngun cp trc v ngun chnh) - Ngun cp trc hot ng tt (v c 5V STB) - IC dao ng ca ngun chnh hot ng v cho dao ng ra iu khin mch cng sut - Khi chp chn P.ON xung mass thy ngun c hot ng, lnh P.ON c tc dng. Nguyn nhn ca hin tng trn l do nhng h hng sau: - Cc t lc ngun chnh b hng lm cho in p u vo gim xung. - Cc in tr u song song vi cc t lc ngun chnh b t lm cho in p im gia cc t b lch - C mt n cng sut khng hot ng do b bong mi hn hoc n t CE - C mt n o pha b hng hoc b bong mi hn - IC dao ng ra b mt mt v, ch cn dao ng ra mt v. - Cc t lc u ra b kh, b phng. Cc bc kim tra v sa cha. * Bn o in p trn hai t lc ngun chnh, mi t cn phi c 150V

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o in p trn hai t lc ngun chnh mi t phi c 150V

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Nu in p trn hai t b lch nhng tng in p trn hai t vn 300V l do b t in tr u song song vi cc t

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Nu tng in p trn hai t nh hn 300V l cc t b hng Ch - Cc trng hp hng t hoc in tr u song song vi cc t lc ngun lm cho in p im gia cc t b lch cn l nguyn nhn lm cho cc n cng sut ca ngun chnh b chp * Kim tra v hn li cc n cng sut ca ngun chnh

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Nu mt n cng sut khng hot ng, ngun vn ra in p nhng s khng hot ng c khi c ti

* Kim tra ch in p ca cc n o pha, hai n o pha phi c cc in p nh nhau

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Kim tra ch in p ca cc n o pha, hai n o pha phi c cc in p nh nhau, khi ch ch th cc n c in p nh s trn

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Kim tra ch in p ca cc n o pha, hai n o pha phi c cc in p nh nhau, khi ch ang hot ng th cc n c in p nh s trn

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* Ch - Nu ch in p ca hai n o pha khc nhau trong khi kim tra cc n vn tt l b hng mt v ca IC dao ng, trng hp ny ngun vn chy nhng khng hot ng c khi c ti.

Kim tra v thay th cc t lc u ra c hin tng b phng, b kh.

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Ngun ATX: Mt ngun cp trc 5V Stanby ng ngy 28/02/2009 bi: lqv77

Phn tch nguyn nhn. Mt in p 5V STB l do ngun cp trc khng hot ng, c th do cc nguyn nhn sau y. * Mt in p 300V DC bn s cp - Khi ngun b cc s c nh chp n cng sut, chp cc i t chnh lu s gy n cu ch v mt in p 300V DC

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Nu chp cc i t trong cu i t chnh lu s dn n n cu ch hoc t in tr nhit, lm mt in p 300V DC

Nu chp cc n cng sut ca ngun chnh s gy n cu ch, t in tr nhit v ko theo gy chp cc i t chnh lu, mt in p 300V DC * Ngun cp trc khng dao ng. - Ngun cp trc s b mt dao ng khi b cc s c nh t in tr mi, bong mi hn n cng sut v cc in tr, t in hi tip to dao ng.

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- Nu t in tr mi hoc bong chn R, C hi tip th ngun cp trc s mt dao ng, mt in p ra - Nu bong chn n cng sut th mch cng mt dao ng v mt in p ra - Nu chp n cng sut th s n cu ch, t in tr nhit v c th lm chp cc i t chnh lu in p AC 220V - Nu chp hoc t cc i t chnh lu in p ra cng lm mt in p 5V STB

Xem li bi hc lin quan n quan n bnh ny Bc 3 - Tho v my ra v kim tra Bn cn kim tra tt c cc linh kin c ch thch nh hnh di y. - Kim tra cu ch xem c b t khng ?

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- Kim tra in tr nhit (c in tr khong 4,7 ) xem c b t khng ? - Kim tra cc i t chnh lu xem c b t hay b chp khng ? - Kim tra cc n cng sut xem c b chp khng ? - Kim tra hai con i t chnh lu u ra xem c b chp hay t khng ?

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Cn kim tra cc linh kin c ch thch nh hnh trn. Cc trng hp h hng v phng php sa cha

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Trng hp 1 - Khng pht hin thy cc linh kin trn b chp hay t

- Cp in vo o vn thy c in p 300V (hoc o trn cc t lc vn thy c 150V trn mi t)Sa cha * Nu vn c in p 300V DC u vo ngha l cc n cng sut khng b chp, cu ch v cc i t vn tt. * Mt in p ra l do ngun b mt dao ng, v vy bn cn kim tra k cc linh kin sau:

- Kim tra k in tr mi, trng hp ny a s l do hng in tr mi. (ch - in tr mi phi thay ng tr s hoc cao hn mt cht)

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in tr mi c u t in p 300V n chn B hoc chn G n cng sut - Hn li n cng sut, in tr v t hi tip - o kim tra hai i t chnh lu u ra, nu thy chp th bn thay i t mi (ch - y l i t cao tn)

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Sau khi sa xong, bn cp in cho b ngun v o in p trn si dy mu tm nu c in p 5V th ngun Stanby m bn sa hot ng tt.

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Trng hp 2 - Pht hin thy t cu ch, chp mt hoc nhiu i t, thm ch t c in tr nhit. - o n cng sut ca ngun cp trc thy b chp CE hoc chp DS, hai n cng sut ca ngun chnh vn tt.

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Cc bc sa cha * Tho n cng sut ang b chp ra ngoi v ch thay n mi vo sau khi sa xong mch u vo v c in p 300V DC.

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Tho n cng sut ang b chp ra ngoi

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* Thay cc i t b chp ho b t * Thay in tr nhit (nu t), nu khng c ta c th thay bng in tr s 4,7 /10W * Thay cu ch (lu cn thay cu ch chu c 4 Ampe tr ln)

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Thay th cu ch, in tr nhit v cc i t chnh lu b hng => Sau cp in cho b ngun, o in p trn hai t lc ngun chnh xem c in p cha v c cn bng khng ?

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- o in p trn hai t lc phi c in p 150V v in p trn hai t phi bng nhau. - Trng hp o thy in p trn hai t b lch, bn cn phi thay hai con in tr u song song vi hai t ny. - Nu in p trn hai t in vn b lch th bn cn phi thay hai t in mi. - Nu in p trn hai t ny b lch th ngun cho dng yu v hay b cht cc n cng sut ca ngun chnh. * Kim tra k cc linh kin xung quanh n cng sut xem c b hng khng ?

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- Khi n cng sut b chp thng ko theo cc linh kin khc bm vo chn B v chn E ca n cng sut b hng theo. - Cn kim tra k cc in tr bm vo chn E v cc i t, Transistor bm vo chn B => Cc linh kin xung quanh nu thy hng ta cn thay th ngay. * Bc sau cng l lp n cng sut vo v tr Lu : - Khi thay n cng sut bn cn ch , c hai loi n c s dng trong ngun cp trc l n BCE (n thng) v n DSG (Mosfet) - Nu bn thay nhm hai loi n trn th n s b hng hoc khng hot ng - Bn c th thay mt n cng sut tng ng (nu khng c n ng s) - n tng ng l n c cng chng loi BCE hay DSG v c ly t v tr tng ng trn mt b ngun khc, hoc

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bn c th tra cu cc thng s: U max - in p cc i, I max - dng cc i, v P max - cng sut cc i, cc thng s trn nu chng tng ng l thay c. a ch tra cu n Mosfet y * Cp in cho b ngun v o in p 5V STB trn dy mu tm

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Sau khi sa xong, bn cp in cho b ngun v o in p trn si dy mu tm nu c in p 5V th ngun Stanby m bn sa hot ng tt. ________________________________________________________________________________________

Trng hp 3 - Pht hin thy t cu ch, chp mt hoc nhiu i t, t in tr nhit. - o n cng sut ca ngun cp trc thy bnh thng nhng hai n cng sut ca ngun chnh b chp CE Cc bc sa cha * Tho hai n cng sut ca ngun chnh ang b chp ra ngoi

Tho hai n cng sut ra ngoi * Sau bn thay th cu ch, in tr nhit v cc i t b hng.

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Thay th cu ch, in tr nhit v cc i t b hng => Sau cp in cho b ngun, o in p trn hai t lc ngun chnh xem c in p cha v c cn bng khng ?

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- o in p trn hai t lc phi c in p 150V v in p trn hai t phi bng nhau. - Trng hp o thy in p trn hai t b lch, bn cn phi thay hai con in tr u song song vi hai t ny. - Nu in p trn hai t in vn b lch th bn cn phi thay hai t in mi. - Nu in p trn hai t ny b lch th ngun cho dng yu v hay b cht cc n cng sut ca ngun chnh. * o kim tra in p 5V STB trn dy mu tm

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Sau khi sa xong, bn cp in cho b ngun v o in p trn si dy mu tm nu c in p 5V th ngun Stanby m bn sa hot ng tt. * Bc sau cng l bn thay hai n cng sut mi cho ngun chnh. - Bn c th thay cc n cng sut tng ng (nu khng c n ng s) - n tng ng l n c cng chng loi BCE c ly t v tr tng ng trn mt b ngun khc, hoc bn c th tra cu cc thng s: U max - in p cc i, I max - dng cc i, v P max - cng sut cc i, cc thng s trn nu chng tng ng l thay c. a ch tra cu n Mosfet y trng hp 3 ny - nguyn nhn chp hai n cng sut thng do in p trn hai t lc ngun chnh b lch, v vy khi kim tra thy cc n cng sut ca ngun chnh b chp, bn cn kim tra k hai t lc ngun v hai in tr u song song vi

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chng, sau khi thay th cc t v in tr ny, in p o c trn hai t phi bng nhau v bng 150V

V d - Nu t R3 trn th in p trn hai t s lch nhau, trn t C1 ch c 100V trong khi t C2 c 200V, trng hp ny khi chy s gy hng cc n cng sut ca ngun chnh sau t pht hot ng

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Khi cc t lc ny b kh cng gy ra cho in p im gia b lch, v vy bn cn kim tra k cc t lc nu in p trn hai t ny lch nhau

Xem li bi hc v kim tra t in y

Ngun ATX: Cc mch bo v thc t ng ngy 18/02/2009 bi: lqv77 1 - Phn tch mch n nh p ra trn b ngun POWER MASTER 1) S nguyn l ca ton b khi ngun

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2) S khu vc mch hi tip v IC dao ng

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3) Phn tch mch hi tip

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o Chn 1 v 2 ca IC dao ng TL 494 hoc IC 7500 thng c s dng nhn in p hi tip v khuch i ri to ra tn hiu iu khin, iu khin cho in p ra khng i.

o Cu to ca mch: -

in p chun 5V c ly ra t chn (14) ca IC dao ng, in p ny c u qua cu phn p ly ra mt in p chun c p nh hn ri a vo chn s 2 gim cho in p chn ny c c nh. -

Cc in p th cp 12V v 5V cho i qua cc in tr 24K v 4,7K ri a vo chn s (1) ca IC, t chn (1) c cc in tr phn p xung mass gi cho chn ny c in p cao hn so vi chn (2) khong 0,1V

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Mch hi tip n nh in p ra

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o Nguyn l hot ng: -

Nu nh in p ra khng thay i th in p chnh lch gia chn (1) vi cn (2) cng khng thay i, t IC cho hai tn hiu dao ng ra chn (8) v chn (11) c bin cng khng i => v kt qu l in p ra khng thay i. - Nu v mt l do no m in p ra tng ln (v d khi in p vo tng ln hoc dng tiu th gim i), khi cc in p 12V v 5V tng => lm cho in p chn (1) tng, chnh lch gia chn (1) v (2) tng ln => IC s iu chnh cho bin dao ng ra chn (8) v chn (11) gim xung => cc n cng sut hot ng yu i => lm cho in p ra gim xung (v gi tr ban u) - Nu in p ra gim xung (v d khi in p vo gim xung hoc dng tiu th tng ln), khi cc in p 12V v 5V gim => lm cho in p chn (1) gim, chnh lch gia chn (1) v (2) gim xung => IC s iu chnh cho bin dao ng ra chn (8) v chn (11) tng ln => cc n cng sut hot ng mnh hn => lm cho in p ra tng ln (v gi tr ban u) * Nh vy nh c mch hi tip trn m gi cho in p u ra lun lun c n nh khi in p u vo thay i hoc khi dng tiu th thay i

2 - Phn tch mch n nh p ra trn b ngun SHIDO 1) S nguyn l ca ton b khi ngun

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3) Phn tch mch hi tip o Cu to ca mch:

- in p chun 5V c ly ra t chn (14) ca IC dao ng, in p ny c u qua in tr R47 ri a vo chn s (2) gim cho in p chn ny c c nh khong 5V - Cc in p th cp 12V v 5V cho i qua cc in tr R16(27K) v R15(4,7K) ri a vo chn s (1) ca IC, t chn (1) c cc in tr R35, R69 v R33 phn p xung mass, chn (1) c phn p c in p cao hn so vi chn (2) khong 0,1V

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IC dao ng v mch hi tip n nh p ra o Nguyn l hot ng:

- Nu nh in p ra khng thay i th in p chnh lch gia chn (1) vi cn (2) cng khng thay i, t IC cho hai tn hiu dao ng ra chn (8) v chn (11) c bin cng khng i => v kt qu l in p ra khng thay i. - Nu v mt l do no m in p ra tng ln (v d khi in p vo tng ln hoc dng tiu th gim i), khi cc in p 12V v 5V tng => lm cho in p chn (1) tng, chnh lch gia chn (1) v (2) tng ln => IC s iu chnh cho bin dao ng ra chn (8) v chn (11) gim xung => cc n cng sut hot ng yu i => lm cho in p ra gim xung (v gi tr ban u) - Nu in p ra gim xung (v d khi in p vo gim xung hoc dng tiu th tng ln), khi cc in p 12V v 5V gim => lm cho in p chn (1) gim, chnh lch gia chn (1) v (2) gim xung => IC s iu chnh cho bin dao ng ra chn (8) v chn (11) tng ln => cc n cng sut hot ng mnh hn => lm cho in p ra tng ln (v gi tr ban u) * Nh vy nh c mch hi tip trn m gi cho in p u ra lun lun c n nh khi in p u vo thay i hoc khi dng tiu th thay i

3 - Phn tch mch n nh p ra trn b ngun MAX POWER 1) S nguyn l ca ton b khi ngun

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3) Phn tch mch hi tip o Cu to ca mch:

- Cc in p th cp 12V v 5V cho i qua cc in tr R49(33K) v R50(11K) ri a vo chn s (17) ca IC, t chn (17) c cc in tr R47 v R48 phn p xung mass - IC - SG 6105 c in p chun s dng ni b trong IC m khng a ra ngoi.

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IC dao ng v mch hi tip n nh p ra o Nguyn l hot ng:

- Nu v mt l do no m in p ra tng ln (v d khi in p vo tng ln hoc dng tiu th gim i), khi cc in p 12V v 5V tng

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=> lm cho in p chn (17) tng, IC s iu chnh cho bin dao ng ra chn (8) v chn (9) gim xung => cc n cng sut hot ng yu i => lm cho in p ra gim xung (v gi tr ban u) - Nu in p ra gim xung (v d khi in p vo gim xung hoc dng tiu th tng ln), khi cc in p 12V v 5V gim => lm cho in p chn (17) gim => IC s iu chnh cho bin dao ng ra chn (8) v chn (9) tng ln => cc n cng sut hot ng mnh hn => lm cho in p ra tng ln (v gi tr ban u) * Nh vy nh c mch hi tip trn m gi cho in p u ra lun lun c n nh khi in p u vo thay i hoc khi dng tiu th thay i

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Ngun ATX: Phn tch mch trn s nguyn l

Xem li ti http://lqv77.com/category/nguon-atx/

Hoc blog http://tudonghoak30.6x.to

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Ngun ATX: Li thng gp mch ngun chnh ng ngy 16/02/2009 bi: lqv77

1 - Mch iu khin tt m v bo v o Mch iu khin tt m

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o Thit k ca mch. - T chn PS ON (P.ON) khng iu khin trc tip vo IC dao ng m ngi ta thit k cho lnh P.ON chy qua mch bo v, trong trng hp ngun c s c nh in p ra tng cao hoc ph ti b chp, khi mch bo v s ngt lnh P.ON a n IC bo v cc n cng sut trn ngun cng nh bo v Mainboard.

o Phn tch nguyn l iu khin lnh PS ON - trn s di y: -

Khi chn lnh PS ON c mc in p cao (khong 3 n 5V), in p ny lm cho n Q13 dn, chn E ca n Q13 c mc in p cao, in p ny s i qua i t D26 vo chn (4) ca IC dao ng, khi chn (4) ca IC

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c in p cao th bin dao ng ra s bng 0 => cc n cng sut khng hot ng. - Khi c lnh m ngun - chn lnh PS ON gim v 0V, n Q13 tt, in p chn E n Q13 gim thp v vy khng c in p i qua i t D26 sang chn (4) ca IC dao ng, ng thi in p bo v U_Protect cng khng c nn n Q11 tt => n Q9 tt => khng c in p i qua i t D27 sang chn (4) ca IC dao ng. -

Khi khng c in p i vo chn (4), in p chn (4) s gim dn v 0V, t C28 c tc dng lm cho in p chn (4) gim t t, y l mch khi ng mm - khi in p chn (4) gim dn th bin dao ng ra tng dn cho n khi in p u ra t n mc bnh thng.

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o Phn tch nguyn l ca mch bo v qu p. - Cc in p 3,3V v 5V a v t th cp ca ngun chnh s tham gia bo v qu p trong trng hp in p ra tng. - i t Zener ZD2 (6,2V) c mc t in p 5V v chn B n Q11 * Nu ng in p 5V tng > 6,2V th s c dng in chy qua ZD2 v lm cho n Q11 dn - i t Zener ZD3 (5,3V) c mc t in p 3,3V v chn B n Q11 * Nu ng in p 3,3V tng > 5,3V th cng s c dng in chy qua ZD3 v lm cho n Q11 dn

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=> Khi n Q11 dn => ko theo n Q9 dn => dng in i qua Q9 => i qua i t D27 vo lm cho chn (4) IC dao ng tng ln => bin dao ng ra gim xung bng 0 => cc n cng xut ngng hot ng.

o Phn tch nguyn l ca mch bo v qu dng. -

Khi ngun c hin tng chp u ra (qu dng) khi cc ng in p ra s gim thp, cc n cng sut lm vic trong tnh trng qu ti v s b hng nu khng c bo v. - Nu cc ng in p m gim (tc l bt m) th khi s c mt dng in i qua D30 vo chn n Q11 lm Q11 dn => ko theo n Q9 dn => dng in i qua Q9 => i qua i t D27 vo lm cho chn (4) IC dao ng tng ln => bin dao ng ra gim xung bng 0 => cc n cng xut ngng hot ng. - Nu in p 5V gim => s lm mt in p P.G (y l in p bo s c cho Mainboard bit Mainboard kho cc mch trn Main khng cho chng hot ng - xem li l thut v Mainboard)

2 - Mch hi tip n nh in p ra. o S nguyn l & khu vc mch hi tip.

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o Nguyn l hot ng ca mch hi tip n nh in p ra. -

Ngi ta s dng mch khuch i thut ton chn 1 v 2 ca IC dao ng khuch i in p hi tip, chn s 2 c gim vi in p chun 5V (in p ny ly qua cu phn p R47 v R49), chn s 1 c ni vi in p hi tip. - Gi s in p u vo tng ln hoc dng tiu th gim xung, khi in p 12V v 5V c xu hng tng => in p hi tip a v chn s 1 ca IC dao ng tng ln => cc mch khuch i thut ton s so snh in p hi tip

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vi in p chun v a ra dao ng c bin gim xung => cc n cng sut ca ngun chnh hot ng yu i v in p ra gim xung tr v gi tr ban u. - Khi in p vo gim hoc dng tiu thu tng ln th in p ra c xu hng gim => in p hi tip a v chn s 1 ca IC dao ng gim => cc mch khuch i thut ton s so snh in p hi tip vi in p chun v a ra dao ng c bin tng ln => cc n cng sut ca ngun chnh hot ng mnh hn v in p ra tng ln tr v gi tr ban u.

Mch hi tip n nh in p ra a v chn s 1 ca IC dao ng - TL494 3 - Hot ng ca mch dao ng v cng sut

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o Hot ng ca IC dao ng v mch cng sut. Khi IC dao ng c cc iu kin: - C Vcc 12V cung cp cho chn 12 - C in p chun 5V a ra chn 14 - Chn s 4 c in p bng 0V => Khi IC s hot ng v cho cc tn hiu dao ng ra chn 8 v chn

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11, cc tn hiu dao ng s c cc n Q7 v Q8 khuch i ri a qua bin p o pha T2 sang iu khin cc n cng sut. - Hai n cng sut s hot ng ngt m theo tn hiu dao ng to ra in p xung im gia, in p ny c a qua bin p chnh, thot qua t gm C3 ri tr v im gia ca hai t lc ngun. - Th cp ca bin p chnh s ly ra cc in p 12V, 5V v 3,3V cc in p ny s c chnh lu thnh cc in p mt chiu cung cp cho Mainboard.

o Dng in chy qua cc n cng sut: IC dao ng cho ra hai xung in iu khin hai n cng sut: -

Khi chn 8 c dao ng ra th n Q7 hot ng, thng qua bin p o pha iu khin cho n cng sut Q1 hot ng, khi c dng in chy t ngun 300V => qua n Q1 qua cun dy (5-1) ca bin p o pha ly hi tip dng => sau cho qua cun s cp (2-1) ca bin p chnh ri tr v in p 150V im gia ca 2 t lc ngun. -

Khi chn 11 c dao ng ra th n Q8 hot ng, thng qua bin p o pha sang iu khin cho n cng sut Q2 hot ng, khi c dng in chy t ngun 150V (im gia ca hai t lc) => chy qua cun s cp (2-1) ca bin p chnh => chy qua cun (1-5) ca bin p o pha => chy qua n Q2 ri tr v cc m ca ngun in.

o Hai n cng sut hot ng cn bng. Hai t C1, C2 v hai in tr R2, R3 to ra in p cn bng im gia, in p ri trn mi t l 150V - s trn ta thy, n Q1 c in p cung cp t t C1 - n Q2 c in p cung cp t t C2 Thc ra hai n hot ng c lp v ch chung nhau cun s cp ca bin p chnh -

Khi in p ri trn hai t cn bng th hai n c cng sut hot ng

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ngang nhau, v d in p trn mi t l 150V th mi n c cng sut hot ng l 150W - Trong trng hp in p trn hai t b lch th cng sut hot ng ca hai n cng b lch theo, v d in p trn t C1 l 200V v trn t C2 l 100V th khi n Q1 s hot ng cng sut 200W v n Q2 hot ng 100W, vi trng hp nh vy th n cng sut Q1 s b hng sau mt thi gian hot ng do b qu ti. - Trong trng hp mt n b hng (b chp) th s ko theo n kia b chp do chng phi gnh c in p 300V

o Cc trng hp in p im gia hai t b lch. -

Nu in tr R3 b t th in p im gia hai t s b lch, khi hai u t C1 c in p khong 100V v t C2 phi ghnh in p khong 200V

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Nu in tr R2 b t th in p im gia hai t s b lch, khi hai u t C1 c in p khong 200V v t C2 ghnh in p khong 100V

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Trng hp hng mt trong hai t lc cng gy ra lch in p, t no b hng th in p trn t s gim v tng in p trn hai t cng b gim theo Lu : in p im gia hai t lc ngun b lch l mt nguyn nhn lm hng cc n cng sut ca ngun chnh

4 - H hng thng gp ca b ngun.

o H hng 1 - Ngun b mt dao ng, cc n cng sut khng hot ng.Biu hin: -

Khi chp chn PS ON xung mass nhng qut ngun khng quay, mc d o in p 5V STB vn tt, kim tra n cng sut khng b hng.

Nguyn nhn mt dao ng. - Mt in p 12V cp cho IC - Lnh PS ON khng a n c chn IC dao ng. - Hng IC dao ng

o H hng 2 - Ngun b chp cc n cng sut, n cu ch, hng cc i t chnh lu.Biu hin: - Quan st thy cu ch b t, thay cu ch khc vo li n tip, o cc n cng sut ca ngun chnh thy b chp.

Nguyn nhn chp cc n cng sut. - Do in p ti im gia cc t lc b lch - Do chp cc i t chnh lu in p ra gy ra chp ph ti - Do khi hot ng n b qu nhit hoc b qu cng sut thit k

o H hng 3 - Mch bo v hot ng v ngt dao ng.

Biu hin: - Khi chp chn PS ON xung mass, qut ngun quay 1 - 2 vng ri tt

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Nguyn nhn - Do chp i t chnh lu u ra - Do in p ra b tng cao ln mch bo v hot ng v ngt

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Ngun ATX: Cc mch cp trc thng dng ng ngy 15/02/2009 bi: lqv77 1 - Ngun Stanby c hi tip trc tip

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

S nguyn l ca ngun Stanby c hi tip trc tip o Nguyn l hot ng.Nguyn l to v duy tr dao ng:

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Khi c in p u vo cp cho b ngun, mt dng in s i qua in tr mi (R81)vo nh thin cho n cng sut (Q16) lm cho n cn sut dn kh mnh, ngay khi n cng sut dn, dng in bin thin trn cun s cp cm ng sang cun hi tip, do cun dy hi tip

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mc o chiu so vi cun s cp nn in p hi tip thu c c gi tr m, in p ny np qua t hi tip C15 lm cho in p chn B n cng 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 tr khong - 6V, in p ny c t C12 lc cho bng phng gi l in p hi tip (Uht) - Hai i t l i t Zener ZD27 v i t D5 gim mt gi tr in p khng i hai u bng khong 6,6V, t xc lp cho chn B n cng sut mt gi tr in p khong 0,6V - Do st p trn hai i t ZD27 v D5 l khng i, nn in p chn B n cng sut n ph thuc vo in p hi tip (Uht) - Gi s khi in p u vo tng => in p u ra c xu hng tng => in p trn cun hi tip cng tng => in p hi tip (Uht) cng m hn => lm cho in p chn B n cng sut gim xung => n cng sut hot ng yu i => lm cho in p ra gim xung v v tr ban u. - Ngc li khi in p u vo gim => in p u ra 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) => lm cho in p chn B n cng sut tng ln => n cng sut hot ng mnh hn => lm cho in p ra tng ln v v tr ban u.

o c im ca loi ngun ny -

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y l loi ngun s dng in p hi tip m cho nn in tr nh thin kh nh v cho dng nh thin tng i ln, khi mi c ngun 300V u vo, n cng sut dn mnh, nh mch hi tip m m n chuyn sang 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 cng sut c hot ng lin tc cng sut ln v n s b hng (b chp) sau vi giy.

o 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 linh kin sau y: - t in tr mi - Bong chn R82 hoc C15 (lm mt in p hi tip) - Mt in p 300V DC u vo

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Cu hi 2 - Cho bit nguyn nhn khi b ngun trn c in p ra rt thp (v d ng 12V nay ch cn khong 6V) Tr li Ta 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 trn t 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 B n cng sut phi c in p khong 0,6V) => t ta suy ra st p trn hai i t Zener ZD27 v i t D5 ch cn khong 3,6V, hai i t ny khi bnh thng chng lun lun gim mc 6,6V v by gi theo suy 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 ng 12V nay ra n 20V) Tr li Phn tch 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 i t Zener b d, nu in p ra tng l i t Zener b t, nh vy trng 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 dn mnh m khng chuyn sang c trng thi ngt.

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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

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 s tng cao v n cng sut hot ng qu ti v c th b hng ngay t khi 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 in p chn B n cng sut gim => in p ra gim thp.

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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 p chn 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 n cng sut, nu mt tc dng ca mch ny th n cng sut c th b hng, b chp.

o 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 v qu dng Cc linh kin: R12, R13 v Q4 l cc linh kin ca mch bo v qu dng, nguyn l hot ng ca 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 B n 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 cng sut c bo v, trong trng hp ny ngun s chuyn sang hin tng t kch, in p ra thp v c - mt - c - mt ., nu o in p ra thy kim ng h dao ng.

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

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o Mch ngun Stanby s 1

o 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 l n BCE - Mch ngun s 1 do s dng Mosfet nn in tr mi c tr s rt ln (2M), trong khi mch ngun th 2 in tr mi ch c 680K

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

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

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o 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 ca mch dao ng tt Nguyn nhn ngun b t kch l do. - Chp ph ti u ra (mch bo v qa dng hot ng sinh ra t kch)

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- 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 qu p 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 12V(C22) th c mt chiu o phi cho tr khng cao vi trm , nu c hai chiu o thy tr khng thp sp s 0 th => th ng 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)

o Bnh 3 - in p ra thp hn so vi in p thng thng (v d ng 12V nay ch cn 8V)

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o in p ra ca ngun cp trc, bn chnh ng h v thang 10V DC, o que vo u dng ca i t chnh lu, que en vo mass bn th cp Nguyn nhn v kim tra: Nguyn nhn ca hin tng ny thng do mch hi tip a in p hi tip v qu mnh, v vy 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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Nguon: hocnghe.com.vn

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Ngun ATX: Mch ngun chnh

ng ngy 15/02/2009 bi: lqv77 1 - V tr ca mch ngun chnh.

o Ngun chnh nm u ? - Nu loi tr mch lc nhiu, mch chnh lu v ngun cp trc (Stanby) ra th ngun chnh l ton b phn cn li ca b ngun ATX

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o Ngun chnh c cc mch c bn nh: - Mch to dao ng. (s dng IC to dao ng) - Bin p o pha a cc tn hiu dao ng n iu khin cc n cng sut. - Cc n khuch i cng sut. - Bin p chnh (ly ra in p th cp) - Cc i t chnh lu u ra - Mch lc in p ra - Mch bo v

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o Cc in p ra ca ngun chnh: - in p + 12V (a ra qua cc dy mu vng) - in p + 5V (a ra qua cc dy mu ) - in p + 3,3V (a ra qua cc dy mu cam) - in p - 12V (a ra dy mu xanh l) - in p - 5V (a ra mu xanh tng)

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o S nguyn l chung ca ngun chnh

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Nguyn l

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o Khi cm in AC 220V, in mch chnh lu s cung cp in p 300V DC cho ngun cp trc v mch cng sut ca ngun chnh.

o Ngun cp trc (Stanby) hot ng v cung cp in p 12V cho IC dao ng, ng thi cung cp in p 5V STB cho mch khi ng trn Mainboard.

o Khi c lnh P.ON ( mc thp) a ti iu khin cho IC dao ng hot ng, IC dao ng to ra hai tn hiu dao ng ngc pha, cho khuch i qua hai n o pha ri a qua bin p o pha sang iu khin cc n cng sut.

o Khi cc n cng sut hot ng s to ra in p xung im gia, in p ny c a qua bin p chnh ri thot qua t gm v im gia ca hai t lc ngun.

o Cc in p th cp c ly ra t bin p chnh c chnh lu v lc thnh in p DC bng phng cung cp cho Mainboard.

o

o Lnh iu khin ngun chnh: (Chn P.ON a qua dy mu xanh l cy t Mainboard ln) - Lnh P.ON t Mainboard a ln theo dy mu xanh l cy l lnh iu khin ngun chnh hot ng. - Khi chn lnh P.ON = 0V l ngun chnh chy, khi chn P.ON = 3 n 5V l ngun chnh tt

o Tn hiu bo v Mainboard (Chn P.G i qua dy mu xm xung Mainboard) - T ngun chnh lun lun c mt chn bo xung Mainboard cho bit tnh trng ngun c hot ng bnh thng khng, l chn P.G (Power Good), khi chn ny c in p t 3 n 5V l ngun chnh bnh thng, nu chn P.G c in p = 0V l ngun chnh ang c s c.

o in p cung cp cho ngun chnh hot ng. - in p cung cp cho mch cng sut l in p 300V DC t bn s cp. - in p cp cho mch dao ng v mch bo v l in p 12V DC ly t th cp ca ngun Stanby.

o Nhn bit cc linh kin trn v ngun: - i t chnh lu in p u ra l i t kp c 3 chn trng ging n cng sut. - Cc cun dy hnh xuyn gm cc dy ng qun trn li ferit c tc dng lc nhiu cao tn. - Cc t lc u ra thng ng cnh bi dy ngun. - IC to dao ng - Thng c s l: AZ750 hoc TL494 - IC bo v ngun - thng dng IC c s l LM339

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- Bin p chnh lun lun l bin p to nht mch ngun - Bin p o pha l bin p nh v lun lun ng gia ba bin p - Hai n cng sut ca ngun chnh thng ng v pha cc n cng sut

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2 - Nguyn l hot ng ca ngun chnh.

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o Khi cm in - Khi bn cm in AC 220V cho b ngun, mch chnh lu s cung cp in p 300V DC cho mch cng sut ca ngun chnh, ng thi ngun Stanby hot ng s cung cp 12V cho IC dao ng ca ngun chnh, tuy nhin ngun chnh cha hot ng v ang trng thi ch, ngun chnh ch hot ng khi c lnh P.ON

o Khi bm cng tc ca my tnh (hoc chp chn P.ON xung mass) - Khi chn P.ON c u mass, lnh m ngun chnh c bt, lnh P.ON i qua mch bo v ri a vo iu khin IC dao ng hot ng. - IC dao ng hot ng v to ra hai xung in ngc pha, cho khuch i qua hai n bn dn ri a qua bin p o pha sang iu khin cc n cng sut. - Hai n cng sut hot ng ngt m theo nguyn tc y ko, to ra in p xung ti im gia, sau ngi ta s dng in p ny a qua bin p chnh, u kia ca bin p c thot qua t gm v im gia ca t ho lc ngun chnh.

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Khi chp chn s 4 ca IC dao ng (494) xung mass, IC s hot ng v cho ra hai xung in ti cc chn 8 v 11, sau c hai n o pha khuch i ri chuyn qua bin p o pha sang iu khin cc n cng sut, cc n cng sut hot ng ngt m lun phin to ra in p xung im gia

3 - Cc IC thng gp trn b ngun ATX

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o IC to dao ng h 494 (tng ng vi IC h 7500)

V d TL494, UTC51494

IC TL 494 c 16 chn, chn s 1 c du chm, m ngc chiu kim ng h

S khi bn trong IC - TL 494

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o

o Chn 1 v chn 2 - Nhn in p hi tip v t ng iu khin in p ra. o Chn 3 u ra ca mch so snh, c th ly ra tn hiu bo s c P.G t chn ny o Chn 4 - Chn lnh iu khin cho IC hot ng hay khng, khi chn 4 bng 0V th IC hot ng, khi chn 4 >0 V th IC

b kho. o Chn 5 v 6 - l hai chn ca mch to dao ng o Chn 7 - ni mass o Chn 8 - Chn dao ng ra o Chn 9 - Ni mass o Chn 10 - Ni mass o Chn 11 - Chn dao ng ra o Chn 12 - Ngun Vcc 12V o Chn 13 - c ni vi p chun 5V o Chn 14 - T IC i ra in p chun 5V o Chn 15 v 16 nhn in p hi tip o

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S chn ca IC TL 494

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o IC to dao ng h 7500 (tng ng vi IC h 494 ) Hnh dng ca hai loi IC to dao ng h 7500

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S khi IC - AZ 7500 S khi ca IC dao ng h 7500 hon ton tng t vi IC dao ng h 494 Hai IC ny AZ7500 (h 7500) v TL 494 (h 494) ta c th thay th c cho nhau

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o

o

o Chn 1 v chn 2 - Nhn in p hi tip v t ng iu khin in p ra. o Chn 3 u ra ca mch so snh, c th ly ra tn hiu bo s c P.G t chn ny o Chn 4 - Chn lnh iu khin cho IC hot ng hay khng, khi chn 4 bng 0V th IC hot ng, khi chn 4 >0

V th IC b kho. o Chn 5 v 6 - l hai chn ca mch to dao ng o Chn 7 - ni mass o Chn 8 - Chn dao ng ra o Chn 9 - Ni mass o Chn 10 - Ni mass o Chn 11 - Chn dao ng ra o Chn 12 - Ngun Vcc 12V o Chn 13 - c ni vi p chun 5V o Chn 14 - T IC i ra in p chun 5V o Chn 15 v 16 nhn in p hi tip

S chn IC - AZ 7500 tng t IC - TL494

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o IC khuch i thut ton LM339 trong mch bo v.

IC LM339 c s dng trong mch bo v ca ngun ATX Mch so snh s dng phn t khuch i thut ton (trong IC - LM339)

o Khi cho mt in p chun (Vref) gim c nh mt u vo dng(+) ca IC thut ton, nu ta cho in p cn so snh vo u m (-) th in p u ra thu c s nghch o vi tn hiu u vo. - Nu Vin tng th Vout s gim - Nu Vin gim th Vout s tng

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o Nu gim u vo m (-) ca IC thut ton v cho tn hiu thay i vo u dng th ta thu c in p ra t l thun vi tn hiu vo. - Nu Vin tng th Vout cng tng - Nu Vin gim th Vout cng gim

4 - Gii p cu hi thng gp

o Cu hi 1 - Da vo c im g phn bit ngun chnh vi ngun cp trc.Tr li: - Trong b ngun ATX thng c 3 bin p trong c mt bin p ln v hai bin p nh, ngun chnh c mt bin p ln v mt bin p nh ng gia, cn bin p nh ng bn cnh l ca ngun cp trc. - n cng sut th ngun chnh lun lun c hai n cng sut, hai n ny thng ging ht nhau v cng chng loi, cng sut ca ngun chnh ch s dng loi n B-C-E, v tr hai n ny ng v pha bin p ln. - Ngun cp trc ch c mt n cng sut, n c th l n B-C-E cng c th l n D-S-G (Mosfet) - Cc n cng sut ca ngun chnh v ngun cp trc lun lun ng v pha cc t lc ngun chnh, cc i t chnh lu in p ra ca ngun chnh cng c 3 chn nhng ng v pha th cp v c k hiu hnh i t trn thn.

o Cu hi 2 - Thi im hot ng ca hai mch ngun c khc nhau khng ?Tr li: - Khi ta cm in cho b ngun l ngun cp trc hot ng ngay, trong khi ngun chnh cha hot ng. - Ngun chnh ch hot ng khi chn lnh P.ON gim xung 0V (hoc ta chp chn P.ON mu xanh vo mass - tc chp vo dy en)

o Cu hi 3 - Ngun cp trc c khi no s dng IC dao ng khng ? Tr li: - C rt t ngun s dng IC dao ng cho ngun cp trc, bi v ngun cp trc c cng sut tiu th nh nn ngi ta thng thit k chng rt n gin, tuy nhin vn c loi ngun s dng cp IC dao ng v n Mosfet nh s di y:

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o Cu hi 4 - Ngun chnh thng s dng nhng IC dao ng loi g ? Tr li: - Ngun chnh thng s dng hai loi IC dao ng l IC h 494 v d TL 494, KA494, TDA494 v v v IC h 7500 v d AZ7500, K7500 Hai loi IC trn c th thay th c cho nhau (v d ngun ca bn chy IC - AZ 7500 bn c th thay bng IC- TL494 - Ngoi ra ngun chnh cn s dng mt s dng IC khc nh SG6105 , ML4824 v v

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o Cu hi 5 - Trong b ngun thng thy c IC so quang, n thuc ca ngun chnh hay ngun cp trc.

Tr li: - Cc ngun chnh thng thng (c hai n cng sut) chng khng dng IC so quang - Trn cc ngun chnh ca my ng b nh ngun my IBM hay Dell th c s dng IC so quang, trn cc b ngun ngi ta s dng cp IC - KA3842 hoc KA-3843 kt hp vi mt n cng sut l Mosfet. - Trn b ngun thng thng th IC so quang ca ca mch ngun cp trc.

o Cu hi 6 - Cc cun dy hnh xuyn u ra ca ngun chnh sau cc i t chnh lu c tc dng g ?

Tr li:

- Tn s hot ng ca b ngun rt cao, sau khi chnh lu loi b pha m nhng thnh phn xung nhn ca in p vn cn, ngi ta s dng cc cun dy lm by chn li cc xung in ny khng chng a xung Mainboard c th lm hng linh kin hoc lm sai d liu.

o Cu hi 7 - Trn cc u dy ra ca ngun ATX, thy c rt nhiu si dy c chung mu v chung in p, thm ch chng cn c hn ra t mt im, vy ti sao ngi ta khng lm mt si cho gn ? Tr li: - Trn cc ngun mi hin nay c ti 4 si dy mu cam, 5 si dy mu v 2 si dy mu vng cng a n rc 24 chn. - Cc dy mu cam u ly chung mt ngun 3,3V - Cc dy mu u ly chung mt ngun 5V - Cc dy mu vng u ly chung mt ngun 12V * S d ngi ta thit k nhiu si dy l tng dng in v tng din tch tip xc, nu c mt rc no tip xc chp chn th my vn c th hot ng c, gim thiu cc Pan bnh do li tip xc gy ra, ngoi ra n cn c tc dng trit tiu t trng do dng in DC chy qua mt dy dn sinh ra (v d mt si dy c dng in mt chiu tng i ln chy qua th chng bin thnh mt si nam chm v b cc vt bng st ht)

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o Lm th no th kim tra c b ngun ATX c chy hay khng khi cha tho v ra ?Tr li: Bn c th tin hnh kim tra s b xem ngun ca bn c cn hot ng hay khng bng cc bc sau: - Cp in AC 220V cho b ngun

Cp in cho b ngun - Dng mt si dy in chp chn mu xanh l cy vo chn mu en - Sau quan st xem qut trong b ngun c quay khng ? => Nu qut quay tt l ngun chy. => Nu qut khng quay hoc quay ri ngt l ngun hng

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Chp chn P.ON (mu xanh l cy) xung Mass

[Codientu.org]_Nguon ATX Toan Tap

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