Bài 3 Bo Nguon Tivi Crt

Bi 3 - Khi ngun xung ca Tivi CRT- Phn tch s tng qut v phn tch nguyn l hot ng ca ngun xung trn cc my Tivi, hiu c ngun xung ca Tivi CRT bn s hiu c nguyn l chung ca cc ngun in trn cc thit b in t khc...

1 - Tng qut v khi ngun 1)Chc nng ca khi ngun Ti vi mu

S cung cp in ca b ngun . Nhim v ca khi ngun l cung cp in p cho vi x l v khi qut dng hot ng, u ra ca ngun l hai in p B1 = 110V v B2 = 12V l hai in p mt chiu bng phng v n nh . - Ngun 110 cung cp cho cao p v tng kch dng - Ngun 12V cung cp cho dao ng dng v n p qua IC LA7805 xung 5V cung cp cho vi x l . in p u vo ca ngun c tm thay i rng t 90V n 280V AC

2) Ch tiu k thut ca ngun Ti vi mu : in p vo l ngun xoay chiu thay i t 90 => 280V

in p u ra l hai hoc nhiu ngun mt chiu bng phng khng thay i khi in p vo thay i v dng tiu th thay i.

Cng sut cung cp khong 100W v bin i gp 10 ln gia ch ch ( khong 10W) vi ch my hot ng ( khong 100W)

Kch thc gn nh, kh nng cho cng sut ln.

t c ch tiu k thut trn, ngun Ti vi mu khng th s dng cc b ngun tuyn tnh nh ta tng thy trong Ti vi en trng c

Gi thit ngun Ti vi mu c cu to nh ngun Ti vi en trng ? Ta bit rng b ngun Ti vi en trng ch cho cng sut khong 30W nhng c trng lng khong 2Kg, vy nu c cng sut khong 100W th trng lng s l 6Kg , iu y khng ph hp vi tiu chun gn nh .

Nu s dng ngun tuyn tn, in p u vo ch c th ln hn v ln hn khng qua 50% in p ra, nh vy khng tho mn tiu chun l in p vo l di rng. Chnh v cc l do trn m b ngun Ti vi mu v cc thit b in t khc c cng sut tiu th ln khng s dng ngun n p tuyn tnh.

3) Nguyn tc ca cc b ngun c cng sut ln ni chung v ngun Ti vi mu ni ring . tho mn c hai tiu chun l gn nh v cho cng sut ln , va gim kch thc v trng lng, va tng cng sut ngi ta lm nh sau :

Nguyn tc hot ng ca cc b ngun xung in p xoay chiu 50Hz c chnh lu v lc phng thnh in p mt chiu, sau c ngt m thng qua cng tc in t vi tn rt cao khong 15KHz n 30KHz , sau ngi ta mi a in p xoay chiu cao tn ny i qua bin p xung, khi hot ng tn s cao th bin p xung cho cng xut rt mnh, bi v tn s hot ng ca bin p t l vi cng xut , ch cn mt bin p c trng lng khong 0,2Kg nhng c th cho cng xut trn 100W => l nguyn tc c bn ca ngun xung c s dng trong Ti vi mu.

4) S tng qut ca khi ngun Ti vi mu :

Khi ngun c th chia lm hai phn chnh : Phn mch u vo : Hu ht cc b ngun xung u c mch u vo ging nhau, mch c nhim v cung cp ngun mt chiu DC phng v sch cho ngun xung, phng l khng cn gn xoay chiu, sch l khng c can nhiu, mch u vo bao gm cc mch: - Mch lc nhiu : Lc b nhiu cao tn bm theo ng dy khng cho lt vo ngun xung . - Mch chnh lu v lc : i in p xoay chiu AC 50Hz thnh in p mt chiu DC phng , in p DC thu c bg 1,4AC, khi ta cm 220V AC ta thu c in p khong 300V DC. Mt s my c mch chnh lu nhn i t ng khi ta cm in AC 110V ta vn thu c 300V DC . - Mch kh t : Kh t d trn n hnh ( mch ny khng c lin quan n s hot ng ca ngun ).

Phn ngun xung : Phn ngun xung c nhiu loi khc nhau nhng v c bn chng c 3 mch chnh : - Mch to dao ng : C nhim v to xung dao ng iu khin n cng xut ng m , to thnh in p xoay chiu a vo bin p xung .- Mch hi tip n nh p ra : Mch dao ng ch to ra in p ra nhng in p ra khng c nh . Mch hi tip c nhim v gi cho in p ra khng i khi in p vo thay i hoc dng tiu thu thay i .- Mch bo v : C nhim v bo v n cng xut ngun khi ph ti b chp hoc in p u vo tng cao, v bo v cc mch pha sau khi khi ngun ra in p qu mnh . - n cng xut : C nhim v ngt m to thnh dng in xoay chiu tn s cao chy qua bin p xung. n cng xut ng thi l n tham gia dao ng nu ngun dao ng s dng kiu dao ng nght, khng tham gia dao ng nu ngun s dng dao ng a hi

2- Khi ngun xung 1) Mch u vo ca b ngun Bn a tr chut vo s xem ch thch

S mch u vo ca khi ngun SW l cng tc tt m chnh , Fuse l cu ch .

C1, T1, C2 l mch lc nhiu cao tn ( mch mu tm )

TH ( Themmistor ) l in tr kh t, Degauss l cun dy kh t

R1 l in tr s hn dng hn ch dng np vo t, D1 - D4 l mch chnh lu cu, C3 l t lc ngun chnh .

* Mch lc nhiu cao tn

Nhiu cao tn bm theo ngun in cloi b sau khi i qua mch lc nhiu Hnh nh khi ngun Ti vi mu :

Bn a tr chut vo linh kin xem ch thch

Hnh nh khi ngun Ti vi mu JVC * Mch chnh lu nhn i t ng .

Bn a tr chut vo s xem ch thch

Mch chnh lu nhn i t ng s dng mt s loi ngun nh ngun JVC, ngun National, ngun Panasonic

* Mch chnh lu nhn 2 : Nu ta dng 2 t lc c in dung bng nhau u ni tip, khi ta u im gia ca hai t lc vo mt u ca ngun xoay chiu AC th ta s thu c in p DC u ra tng gp 2 ln .

* Nguyn l hot ng ca mch nhn 2 t ng :

Khi cm in AC 220 th mch chnh lu bnh thng

Khi cm in AC 130V tr xung th mch t ng nhn 2

thc hin chc nng trn ngi ta phi lp mt mch d p pht hin in p thp v mch cng tc ni t im gia hai t vi mt u in p AC, khi p AC vo < 130V th mch d p xut hin p iu khin a ti ng mch cng tc, mch cng tc trong thc t thng s dng n Thiristor l Diode c iu khin

2) Ngun xung (Ngun Switching)Ngun xung cn gi l ngun Switching ( Ngt m ) hay ngun di rng , l ngun c dng in i qua bin p thay i t ngt to thnh in p ra c dng xung in - gi l ngun xung. in p cung cp cho ngun l p mt chiu c ngt m to thnh dng xoay chiu cao tn i qua bin p - gi l ngun Switching ( Ngt m ) . Ngun c kh nng iu chnh in p u vo rt rng t 90V n 280V AC - gi l ngun di rng .

Bt k ngun xung no cng c 3 mch in c bn sau y :

Mch to dao ng .

Mch hi tip n nh p ra .

Mch bo v .

Sau y ta s xt tng mch c th :

2.1. Mch to dao ng a) Nhim v :

Nhim v ca mch to dao ng l to ra xung in iu khin n cng xut ngt m => to thnh dng in xoay chiu tn s cao ch qua bin p => cho ta in p th cp . Nu khng c mch dao ng ng ngha vi n cng xut khng hot ng ng ngha vi khng c in p ra trn cc cun th cp

Mch to dao ng c nhim v to ra xungin iu khin n cng xut ng m Trong ngun Ti vi mu ngi ta c th s dng mch dao ng nght hoc mch dao ng a hi .

b) Ngun s dng mch dao ng nght Mch dao ng nght c cu to nh sau :

Cu to ca mch dao ng nght trong ngun xung

Cc linh kin khng th thiu ca mch dao ng nght l : in tr mi ( R1 ) c gi tr ln khong 470K , c nhim v mi cho n Q1 dn .

T hi tip ( C1) : a in p t cun hi tip v chuyn trng thi n Q1 t ang dn => sang trng thi ngt, in tr hi tip (R2) : hn ch dng hi tip i qua t C1 .

n cng xut Q1 : To dng in ngt m i qua cun s cp bin p, dng in ngt m ny to thnh t trng cm ng ln cun hi tip to ra in p hi tip - duy tr dao ng, ng thi cm ng ln cun th cp to thnh in p u ra .

Trong ngun s dng dao ng nght, n cng xut Q1 va tham gia dao ng va ng vai tr nh mt cng tc ngt m , n cng xut ca ngun dao ng nght l n BCE

Hng cc linh kin ca mach

c) Ngun s dng mch dao ng a hi ( IC dao ng )

Dao ng a hi l mch dao ng khng c s tham gia ca cun dy, mch dao ng a hi thng s dng IC kt hp vi in tr, t in to thnh dao ng, n cng xut trong ngun dao ng a hi khng tham gia dao ng v s dng n Mosfet ngt m .

B ngun s dng mch dao ng a hi R1 l in tr mi nhng c nhim v cp ngun cho IC to dao ng, R1 c gi tr t 47K n 68K

n cng xut ca mch ngun dao ng a hi l n Mosfet DSG, n ny khng tham gia dao ng .

Mach hi tip v IC l gi cho in p ra n nh, khng c nhim v trong vic to dao ng .

2.2 Mch hi tip gi n nh in p ra . a) Nguyn tc ca mch n nh in p ra

in p ra thng thay i t l thun vi in p vo v thay i t l nghch vi dng in tiu th , ngha l khi in p vo tng hoc dng tiu th gim th in p ra c xu hng tng ln . gi cho in p ra c nh th khi in p vo tng, ngi ta phi iu chnh cho dng in qua n cng xut gim xung (vi mch dao ng nght ) hoc thi gian m ca n gim xung ( vi mch dao ng dng IC ) . iu khin n cng xut mt cch t ng, ngi ta s dng mch hi tip, c hai loi mch hi tip l hi tip trc tip v hi tip so quang, sau y ta s st tng mch c th :

b) Mch hi tip trc tip : Bn a tr chut vo s xem ch thch

Mch hi tip trc tip ( phn mch mu xanh )c tc dng gi cho in p ra c nh khi p vo thay i, mch ny vn b st p khi cao p chy .

trn phn mch mu xanh l mch hi tip trc tip, cc linh kin c nhim v nh sau :

D1, C3 to ra in p hi tip mt chiu, p hi tip ny t l thun vi in p vo .

R3, R4 l cu phn p to ra in p lu mu ULM , t p hi tip do kh p hi tip tng th p ly mu cng tng .

Q2 l n sa sai, nu Q2 dn tng s lm bin dao ng i vo n Q1 gim => dng qua n cng xut s gim .

Nguyn l hot ng ca mch nh sau : Gi s khi in p vo tng => in p ra v in p hi tip tng => in p ly mu tng => n Q2 dn tng => dng qua n Q1 gim => in p ra gim xung chng li s tng p lc u , qu trnh ny iu chnh rt nhanh v khng lm nh hng ti in p u ra . Trong trng hp ngc li ta phn tch tng t.

u im v nhc im ca mch hi tip trn : - Mch trn c u im l n gin, d cn chnh . - Nhc im ca mch trn l in p ra vn b st p khi cao p hot ng, bi v cun th cp v cun hi tip l hai cun dy khc nhau ln c s st p khc nhau . Khc phc nhc im : khc phc nhc im trn ngi ta phi s dng ng hi tip t cao p v chn B n cng xut ngun, khi in p ra c gi c nh khi dng tiu th thay i, mch hi tip trn gi l mch hi tip n nh dng .

c) Mch hi tip so quang .


Mch hi tip so quang - gi cho in p ra c nh trong c hai trng hp : in p vo thay i v khi cao p chy .

Nhim v ca cc linh kin :

Cu phn p R4, R5 to ra in p ly mu a vo IC to p d sai KA431

KA431 l IC to p d sai.

IC so quang truyn in p d sai v bn s cp

Q2 l n sa sai

D1 v C3 l mch chnh lu to in p DC a vo mch so quang.

Nguyn l hot ng ca mch :

Mch trn gi c in p ra c nh trong c hai trng hp : in p u vo thay i v khi cao p chy ( dng tiu thu thay i ). Gi s khi in p u vo gim hoc khi cao p hot ng ( dng tiu th tng cao ) khi in p ra ( 110V) c xu hng gim => in p ly mu gim => dng in qua KA431 gim => dng qua Diode so quang gim => dng qua n so quang gim => in p a v chn B n Q2 gim => n Q2 dn yu i => n Q1 dn tng ln => in p ra tng ln b li s gim p lc u . Trong trng hp ngc li ta phn tch tng t Qu trnh iu chnh trn din ra rt nhanh v khng lm nh hng n in p u ra .

2.3 Cc mch bo v Nhim v ca mch bo v : L bo v n cng xut ngun khng b hng khi ph ti b chp .


Mch bo v n cng xut ngunkhi ngun b chp ph ti ( mch mu tm)

Khi ph ti b chp, dng in qua n cng xut tng cao v lm n b hng T chn E n cng xut ngi ta u thm in tr Re ly ra st p Ubv, st p ny c a vo chn B n bo v Q3, n bo v u gia B n cng xut xung mass. Khi ph ti ca ngun b chp => dng qua n cng xut Q1 tng, st p Ubv tng, khi Ubv > = 0,6V th n Q3 dn lm mt dao ng a vo Q1 => Q1 tm thi ngng dn . Khi Q1 ngng dn => p bo v khng cn v Q1 li dao ng tr li => sau li b ngt bi mch bo v => qu trnh lp i lp li tr thnh t kch => n bo ngun chp chp

3 - Phn tch khi ngun my National TC-485XR 1) S khi, khi ngun my National TC - 485 XRBn a tr chut vo s xem ch thch

S khi b ngun my National TC 485 XR Nhim v ca cc mch nh sau :

Mch lc nhiu, loi b nhiu cao tn bm theo ng dy in

Mch chnh lu x2 t ng, in p 220V AC vo th mch chnh lu bnh thng, khi cm ngun 110V mch chnh lu x2 m bo in p cung cp cho ngun xung vn 300V

Ngun cp trc c nhim v cung cp in p 5V nui IC Vi x l, ngun ny hot ng lin tc trong qu trnh cm in.

Ngun chnh : ch hot ng khi c lnh Power t IC Vi x l a ti, ngun chnh cung cp 115V cho mch cao p, 16V cung cp cho mch dao ng dng ( sau khi n p xung 9V ) v cung cp cho cc mch x l tn hiu ( sau khi n p xung 12V )

iu khin t xa thc hin chc nng tt m ngun chnh thng qua ln Power t vi x l .

2. Mch chnh lu nhn 2 t ng ca ngun National TC 485XR Bn a tr chut vo s xem ch thch

S mch chnh lu nhn 2 t ng ca ngun National TC485XR Nhim v cc linh kin s trn : Mch in c mu l mch chnh lu v lc bao gm D807 l Diode chnh lu cu , t C810, C811, C812, C813 l cc t lc nhiu, in tr R802 v R802 l tr hn dng . Cc linh kin mu xanh da tri l mch nhn 2 t ng bao gm cc linh kin xung quanh 2 n Q807 v Q809, n Q804 ng vai tr nh mt cng tc ng m ni tt mt u AC vo im gia hai t lc ngun . Cc linh kin mu tm l mch bo v .

Nguyn l hot ng ca mch chnh lu nhn 2 t ng nh sau : Khi cm in 110V AC : in p i qua cu phn p R805 thp => lm D802 tt => n Q809 tt => in p i qua R807 tip tc i qua D803 => lm Q807 dn cp ngun m vo chn G ca Thiristor l Thiristor Q804 dn => in p AC t ngun c ni thng vi im gia hai t lc ngun chnh C806 v C809 => khi in p DC thu c tng gp 2 => nh vy ta vn thu c 300V DC.

Tng t nh vy , khi cm ngun 220V AC , in p qua R805 => lm D802 dn => Q809 dn => D803 tt => Q807 tt => Q804 tt , khi mch chnh lu nh lc bnh thng v in p u ra vn l 300V DC

Nu cc linh kin trong mch d p ny b hng hay lng chn s rt nguy him cho b ngun v chng c th bo sai => lm cho mch chnh lu nhn 2 trong c trng hp cm 220VAC lm in p tng cao thnh 600VDC => lm hng n cng sut ngun. Cch khc phc tt nht l tho b n Q804 ra khi mch k c cc my khc tt nht bn hy tho b Thiristor ca mch chnh lu nhn 2 ra khi mch trc khi sa sa mch ngun.

Nguyn l hot ng ca mch bo v ( mu tm ) : Nu in p sau mch chnh lu tng qu cao >>300V , trong cc trng hp mch x2 b hng lm x2 c trng hp cm ngun 220V khi in p DC thu c s l 600V DC , in p ny s lm hng n cng sut ngun , v vy => nu in p ra 400V DC => s c dng i qua D805 vo chn G Thiristor Q805 lm Thiristor Q805 dn => khi in p AC u vo b nh chp xung mass thng qua Q805 => lm n cu ch .

3. Nguyn l mch ngun cp trc trong b ngun National TC485XR Bn a tr chut vo s xem ch thch

Ngun cp trc trong b ngun National TC 485XR Mch to dao ng :( cc linh kin mu ) bao gm

R802 l in tr mi 330K nh thin cho Q881 dn

R884 l in tr hi tip180 ohm hn ch dng hi tip qua t C886

C886 l t hi tip 33nF, hi tip to s ngt m ca n cng sut Q881 => to thnh dao ng .

n cng sut Q881 tham gia dao ng v lm nhim v ngt m to ra dng in bin thin chy qua cun s cp bin p .

Mch hi tip n nh p ra ( cc linh kin mu xanh l ) bao gm

D802 v C885 to ra in p ly mu m

D883 gim in p chn B n cng sut c chnh lch vi in p m ly mu mt lng khng i Nguyn l n p : Nu ngun ra tng => in p ly mu trn t C885 cng m => thng qua D883 lm in p chn B n cng sut Q881 gim => dng qua Q881 gim => lm in p ra gim xung . Trng hp ngun ra gim th mch n p theo hng ngc li .

Mch bo v ( mch mu tm )

Trong trng hp in p ra b chp => n cng sut s hot ng mnh => dng qua R885 tng => st p trn R885 tng => lm n Q882 dn => u tt chn B n Q881 xung mass => n Q881 tt sau li hot ng tr li => to thnh t kch nhng n cng sut khng b hng .

Mch th cp in p u ra th cp c chnh lu qua D885 v lc trn C888 thnh p mt chiu 16V sau c n p qua IC LA7805 xung 5V i ti cung cp cho mch Vi x l .

4. Nguyn l hot ng ca ngun chnh trong b ngun National TC 485XR Bn a tr chut vo s xem ch thch

S ngun chnh trong b ngun my National TC485XR- Cc linh kin mu l mch to v duy tr dao ng- Cc linh kin mu xanh l hi tip gi c nh p ra - Cc linh kin mu tm thuc mch bo v .

Nguyn l ca mch to dao ng : in p vo i qua cc in tr mi R813, R817, R819 vo chn B n cng sut nh thin cho n cng sut dn => to ra dng in chy qua s cp bin p => cm ng ln cun hi tip => in p hi tip np qua t hi tip C817 v chuyn n Q801 sang trng thi ngt m to thnh dao ng. Nu mt trong cc linh kin tham gia dao ng m hng th ngun s mt dao ng => in p ra = 0 V .

Nguyn l ca mch n nh p ra : Khi in p ra tng do in p vo tng hoc do dng tiu th gim, in p a v chn IC to p d sai IC801 tng => dng qua IC so quang tng => hi tip v lm n sa sai Q803 dn tng => n Q806 dn tng => lm in p dao ng ti B n Q801 gim => n Q801 hot ng gim => lm in p ra gim v gi tr c . Nu in p ra b gim => th mch iu chnh theo hng ngc li.Mch hi tip trn iu chnh rt nhanh c vi phn nghn giy v khng lm nh hng n in p u ra . Nu cc linh kin trong mch hi tip so quang b hng => mt in p hi tip => in p ra s b sai, nu hng mc nng hn th in p ra s b t kch n bo ngun chp chp hoc xut hin ri mt

4 - Phn tch khi ngun my Ti vi SONY KV1485 Bn a tr chut vo s xem ch thch

S nguyn l b ngun Ti vi Sony KV - 1485Mch to v duy tr dao ng - Mu Mch hi tip n nh p ra - Mu xanh l

Nhim v ca cc linh kin trong b ngun : B ngun c th chia lm 3 mch chnh l mch to dao ng, mch hi tip n nh p ra v mch bo v, di y l cc linh kin thuc cc mch trn .

* Mch to dao ng ( c nhim v to v duy tr dao ng, nu hng mt trong cc linh kin ny , ngun s mt dao ong , in p ra = 0 ) :

R602 v R617 l cc in tr mi mc ni tip nh thin cho n cng sut hoat ng => to dao ng

in tr R603 v t C607 dn in p hi tip v to s ngt m ca n cng sut duy tr dao ng

R615 nh thin cho n tin khuch i v vy nu t R ny ngun cng mt dao ng .Ghi nh =>> Khi hng mt trong cc linh kin ca mch to dao ng => Ngun s mt dao ng => in p ra = 0V, mt n bo ngun .

* Mch hi tip n nh in p u ra ( C nhim v hi tip gi cho in p ra khng i trong c hai trng hp in p vo thay i v dng tiu th thay i ) bao gm cc linh kin :

IC602 to in p d sai, khi in p u ra tng th dng i qua IC t chn 2 sang chn 3 tng => dng qua diode so quang => hi tip v s cp tng .

IC603 l IC so quang truyn s thay i in p v bn s cp v cch ly in p gia hai bn, khi dng qua diode so quang tng => nh sng chiu vo n so quang tng => n so quang dn tng ln

Q603 v Q601 l hai n sa sai, khuch i in p hi tip a v chn 8 v 9 iu khin gi cho in p ra c nh .

Khi hng mt trong cc linh kin ca mch hi tip ny => ngun s b t kch hoc in p ra b sai :Ghi nh =>> Khi hng cc linh kin trong mch hi tip n nh in p ra => p hi tip v b sai => in p ra b sai hoc b t kch n bo ngun chp chp, hoc in p ra ri mt ngay, nu hi tip b mt th c th gy hng IC cng xut .

5. Nguyn l hot ng ca khi ngun my JVC 1490 M Bn a tr chut vo s xem ch thch

S mch b ngun Ti vi JVC 1490Mch to v duy tr dao ng - Mu Mch hi tip n nh p ra - mu xanh l Nguyn l hot ng : Mch dao ng : Khi c in p 300V i vo mch ngun , ban u in p i qua in tr mi R905, np qua t C913 vo chn B n cng xut thng qua chn 2 IC => lm n cng sut dn => c dng i qua cun s cp => cm ng sang cun hi tip => np qua C916 v R907 hi tip v chn 2 => duy tr dao ng . Mch n nh p ra : in p hi tip c chnh lu qua D902 lc trn C914 ly ra in p m a v chn 1 IC c tc dng gi cho p ra c nh khgi p vo thay i , mch ny khng gi c p ra c nh khi cao p chy.

Ch : Cc my JVC c mt im c bit l - in tr mi ca ngun JVC c th b gim tr s (trng hp ny ch sy ra ngun JVC) => Lm hng IC cng sut , nu ta khng c im ny th ta s b tr gi khi sa ngun JVC - thay bao nhiu IC mi vo th hng by nhiu ( v ta hay ch quan l : t xa n nay c bao gi gp in tr gim tr s u? : nhng vi ngun cc my JVC th l s tht ) !!!

Phng php sa ngun cc my JVC khi b chp IC cng sut Tho b Thiristor ( D944) ca mch chnh lu x2 ra ngoi ( loi tr nguyn nhn hng mch chnh lu x2 => lm in p DC vo tng gp 2 )

Thay in tr mi R905 bng mt in tr khc 180K ( loi tr nguyn nhn tr mi gim tr s )

Thay hai n bo v Q901 v Q902 v hai n ny s hng khi IC b chp .

Thay IC cng sut mi sau khi lm cc vic trn

6 - Phn tch hot ng ca b ngun Ti vi Samsung Vina CS 2040, CS 5085, CS3866.Bn a tr chut vo s xem ch thch

B ngun Ti vi Samsung Savina CS2040, CS5085 Mch to dao ng : S dng IC MIS0169 to dao ng , mch khng c R, C hi tip v vy y l mch dao ng a hi, dao ng to ra c a sang IC cng sut SMR40000 thc hin ngt m dng in chy qua s cp bin p . Mch ngun khng c hi tip so quang v khng c hi tip cao p v vy ngun ny c nhc im l in p u ra thay i khong 20% gia ch ch v khi cao p hot ng => V vy ngun ny thng gy hng s dng v Diode gim bo v u ra .

H hng thng gp ca ngun Samsung Savina CS2040, CS5085 C hai bnh thng gp ca ngun ny l : B chp IC cng sut ngun v n cu ch

Ngun c ting ku e e, bn s cp khng chp, nhng chp s dng hoc Diode n p, sau khi thay s dng v diode n p c mt thi gian li b chp.

Nguyn nhn : Nguyn nhn ca c hai bnh trn u do li ca cp IC SMR40000 v MIS0169, trong cc trng hp hng i hng li s cng sut dng => ta cn phi thay mt cp IC cng sut v IC dao ng mi mc d hai IC ny c th cha hng nhng chng li l nguyn nhn gy ra hng s dng v diode bo v .

7. Nguyn l hot ng ca b ngun Ti vi Deawoo 50N Bn a tr chut vo s xem ch thch

B ngun Ti vi Deawoo 50N B ngun Deawoo thit k kiu chung mass vi bn my , in p 300V i qua bin p xung => i qua IC cng sut ri ra thng in p 103V chn 4 cung cp cho mch cao p.

B ngun cng c cc mch c bn nh sau :

Mch to dao ng : Bao gm in tr mi R806, t hi tip C826, tr hi tip R802, cc linh kin ny kt hp vi n cng sut trong IC to dao ng . Mch c dao ng th mi c in p ra chn 4 IC

Mch hi tip trc tip : Mch ny thc hin trong IC c nhim v gi c inh in p ra khi in p vo thay i , mch ny khng gi c in p ra khi cao p chy .

Mch hi tip cao p : C nhim v gi cho in p ra khng b st p khi cao p chy , mch ny bao gm cc linh kin C830, R804, D808.

Mch bo v : Do chn E n cng sut c u vi in p ra v vy loi ngun ny khng c mch bo v ngun m ch c Diode Zener bo v n hnh trong trng hp in p ra ca ngun tng cao . Do ngun khng c bo v nn khi ngun b chp ph ti => s hng theo IC ngun .

H hng thng gp ca b ngun Deawoo 50N

B ngun Deawoo 50N thng hng 3 trng hp sau :

1. My khng c n bo ngun : Khi kim tra s cp v th cp thy khng b chp. Nguyn nhn : Nguyn nhn ca hin tng trn thng do t tr mi R806 hoc lng chn R, C hi tip l R802 hoc C826. hoc hng IC Khc phc : Hn li chn IC v cc linh kin khu vc ngun

Kim tra v thay in tr mi nu hng

Thay IC cng sut mi 2. My khng c n bo ngun : kim tra thy n cu ch , chp c s cp v th cp ca ngun .

Nguyn nhn : Nguyn nhn ca hin tng ny thng do nguyn nhn gc l chp li tia => dn n chp s dng => dn n cht IC cng sut ngun => dn n chp Diode bo v u ra => ko theo n cu ch v c th chp cu Diode chnh lu Ch : ( cc my c ngun khng cch ly th khi hng s dng thng ko theo hng ngun v ngc li ) Cc bc sa cha : Tho s dng v Diode bo v trn ng 103V ra khi my, tam thi h ti ng ny . Tho IC cng sut ngun ra khi my Kim tra cc Diode xung quanh IC xem c b chp khng ? Kim tra v thay cc Diode trong mch chnh lu cu ( nu hng )

Thay cu ch mi

Lp IC cng sut ngun mi vo my .

Chun b sn t th o in p 103V u ra ca ngun Cp in v xem ng h nu ra ng 103V l ngun hot ng tt.

Tho cun li tia ra kim tra xem c b chy mt s vng dy khng nu thy chy cn thay li tia trc Lp Diode bo v v s dng vo my v cho my chy. 3. Mn sng b co hai bn , khung sng co dn khi sng mn hnh thay i , ngun c ting rt .

Nguyn nhn : Hin tng trn l do ngun b mt hi tip t cao p v ngun (thng do kh t C830) => lm cho in p u ra b st p xung cn khong 70V khi cao p chy, v in p ny thay i khi dng tiu th thay i .

Khc phc : Thay t ho C830 trn ng dn xung dng t chn cao p v khu vc ngun, nu thay t khng c th cn kim tra mch in trn ng dn xung hi tip trn t cao p v ngun

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Bài 3 Bo Nguon Tivi Crt