MCH IN CHNH LU

I. Mch lc nhiu, chnh lu ngun ATX

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.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 ngDng 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 = 309,14Vy 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 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.

Mch chnh lu v mch n p1 Mch chnh lu in xoay chiu1.1 B ngun trong cc mch in t .Trong cc mch in t ca cc thit b nh Radio -Cassette, mlpy, Ti vi mu, u VCD v v chng s dng ngun mt chiu DC cc mc in p khc nhau, nhng ngoi zc cm ca cc thit b ny li cm trc tip vo ngun in AC 220V 50Hz, nh vy cc thit b in t cn c mt b phn chuyn i t ngun xoay chiu ra in p mt chiu , cung cp cho cc mch trn, b phn chuyn i bao gm :Bin p ngun : H th t 220V xung cc in p thp hn nh 6V, 9V, 12V, 24V v v Mch chnh lu : i in AC thnh DC.Mch lc Lc gn xoay chiu sau chnh lu cho ngun DC phng hn.Mch n p : Gi mt in p c nh cung cp cho ti tiu th

S tng qut ca mch cp ngun.1.2 Mch chnh lu bn chu k .Mch chnh lu bn chu k s dng mt Diode mc ni tip vi ti tiu th, chu k dng => Diode c phn cc thun do c dng in i qua diode v i qua ti, chu k m , Diode b phn cc ngc do khng c dng qua ti.

Dng in p u ra ca mch chnh lu bn chu k.1.3 Mch chnh lu c chu kMch chnh lu c chu k thng dng 4 Diode mc theo hnh cu (cn gi l mch chnh lu cu) nh hnh di.

Mch chnh lu c chu k .+ chu k dng ( u dy pha trn dng, pha di m) dng in i qua diode D1 => qua Rti => qua diode D4 v u dy m+ chu k m, in p trn cun th cp o chiu ( u dy trn m, di dng) dng in i qua D2 => qua Rti => qua D3 v u dy m.+ Nh vy c hai chu k u c dng in chy qua ti.2 Mch lc v mch chnh lu bi p2.1 Mch lc dng t in.Sau khi chnh lu ta thu c in p mt chiu nhp nh, nu khng c t lc th in p nhp nh ny cha th dng c vo cc mch in t , do trong cc mch ngun, ta phi lp thm cc t lc c tr s t vi trm F n vi ngn F vo sau cu Diode chnh lu.

Dng in p DC ca mch chnh lu trong hai trng hp c t v khng c t+ S trn minh ho cc trng hp mch ngun c t lc v khng c t lc.+Khi cng tc K m, mch chnh lu khng c t lc tham gia , v vy in p thu c c dng nhp nh.+Khi cng tc K ng, mch chnh lu c t C1 tham gia lc ngun , kt qu l in p u ra c lc tng i phng, nu t C1 c in dung cng ln th in p u ra cng bng phng, t C1 trong cc b ngun thng c tr s khong vi ngn F .

Minh ho : in dng ca t lc cng ln th in p u ra cng bng phng.Trong cc mch chnh lu, nu c t lc m khng c ti hoc ti tiu th mt cng xut khng ng k so vi cng xut ca bin p th in p DC thu c l DC = 1,4.AC2.2 Mch chnh lu nhn 2 .

S mch ngun chnh lu nhn 2+ tr thnh mch chnh lu nhn 2 ta phi dng hai t ho cng tr s mc ni tip, sau u 1 u ca in p xoau chiu vo im gia hai t => ta s thu c in p tng gp 2 ln.+ mch trn, khi cng tc K m, mch tr v dng chnh lu thng thng .+Khi cng tc K ng, mch tr thnh mch chnh lu nhn 2, v kt qu l ta thu c in p ra tng gp 2 ln.3 Mch n p c nh3.1 Mch n p c nh dng Diode Zener.

Mch n p to p 33V c nh cung cp cho mch d knh trong Ti vi mu+ T ngun 110V khng c nh thng qua in tr hn dng R1 v gim trn Dz 33V ly ra mt in p c nh cung cp cho mch d knh+Khi thit k mt mch n p nh trn ta cn tnh ton in tr hn dng sao cho dng in ngc cc i qua Dz phi nh hn dng m Dz chu c, dng cc i qua Dz l khi dng qua R2 = 0Nh s trn th dng cc i qua Dz bng st p trn R1 chia cho gi tr R1 , gi dng in ny l I1 ta c

I1 = (110 33 ) / 7500 = 77 / 7500 ~ 10mAThng thng ta nn dng ngc qua Dz 25 mA3.2 Mch n p c nh dng Transistor, IC n p .Mch n p dng Diode Zener nh trn c u im l n gin nhng nhc im l cho dng in nh ( 20mA). c th to ra mt in p c nh nhng cho dng in mnh hn nhiu ln ngi ta mc thm Transistor khuych i v dng nh s di y.

Mch n p c Transistor khuych i+ mch trn in p ti im A c th thay i v cn gn xoay chiu nhng in p ti im B khng thay i v tng i phng.+ Nguyn l n p : Thng qua in tr R1 v Dz gim c nh in p chn B ca Transistor Q1, gi s khi in p chnE n Q1 gim => khi in p UBE tng => dng qua n Q1 tng => lm in p chn E ca n tng , v ngc li + Mch n p trn n gin v hiu qu nn c s dng rt rng di v ngi ta sn xut cc loi IC h LA78.. thay th cho mch n p trn, IC LA78.. c s mch nh phn mch c mu xanh ca s trn.

IC n p h LA78..

IC n p LA7805+ LA7805 IC n p 5V+ LA7808 IC n p 8V+ LA7809 IC n p 9V+ LA7812 IC n p 12VLu :H IC78.. ch cho dng tiu th khong 1A tr xung, khi rp IC trong mch th U in > Uout t 3 n 5V khi IC mi pht huy tc dng.3.3 ng dng ca IC n p h 78..IC n p h 78.. c dng rng ri trong cc b ngun , nh B ngun ca u VCD, trong Ti vi mu, trong my tnh

ng dng ca IC n p LA7805 v LA7808 trong b ngun u VCD4 Mch n p tuyn tnh (c hi tip)4.1 S khi ca mch n p c hi tip

S khi ca mch n p c hi tip .* Mt s c im ca mch n p c hi tip :Cung cp in p mt chiu u ra khng i trong hai trng hp in p u vo thay i hoc dng tiu th ca ti thay i, tuy nhin s thay i ny phi c gii hn.Cho in p mt chiu u ra c cht lng cao, gim thiu c hin tng gn xoay chiu.* Nguyn tc hot ng ca mch.Mch ly mu s theo di in p u ra thng qua mt cu phn p to ra ( Ulm : p ly mu)Mch to p chun => gim ly mt mc in p c nh (Uc : p chun )Mch so snh s so snh hai in p ly mu Ulm v p chun Uc to thnh in p iu khin.Mch khuch i sa sai s khuch i p iu khin, sau a v iu chnh s hot ng ca n cng xut theo hng ngc li, nu in p ra tng => thng qua mch hi tip iu chnh => n cng xut dn gim =>in p ra gim xung.Ngc li nu in p ra gim => thng qua mch hi tip iu chnh => n cng xut li dn tng => v in p ra tng ln =>> kt qu in p u ra khng thay i.4.2 Phn tch hot ng ca mch ngun c hi tip trong Ti vi en trng Samsung

Mch n p tuyn tnh trong Ti vi Samsung en trng .* ngha cc linh kin trn s .T 2200F l t lc ngun chnh, lc in p sau chnh lu 18V , y cng l in p u vo ca mch n p, in p ny c th tng gim khong 15%.Q1 l n cng xut ngun cung cp dng in chnh cho ti , in p u ra ca mc n p ly t chn C n Q1 v c gi tr 12V c nh .R1 l tr phn dng c cng xut ln ghnh bt mt phn dng in i qua n cng xut.Cu phn p R5, VR1 v R6 to ra p ly mu a vo chn B n Q2 .Diode zener Dz v R4 to mt in p chun c nh so vi in p ra.Q2 l n so snh v khuych i in p sai lch => a v iu khin s hot ng ca n cng xut Q1.R3 lin lc gia Q1 v Q2, R2 phn p cho Q1* Nguyn l hot ng .in p u ra s c xu hng thay i khi in p u vo thay i, hoc dng tiu th thay i.Gi s : Khi in p vo tng => in p ra tng => in p chn E n Q2 tng nhiu hn chn B ( do c Dz gimt chn E n Q2 ln Ura, cn Ulm ch ly mt phn Ura ) do UBE gim => n Q2 dn gim => n Q1 dn gim => in p ra gim xung. Tng t khi Uvo gim, thng qua mch iu chnh => ta li thu c Ura tng. Thi gian iu chnh ca vng hi tip rt nhanh khong vi giy v c cc t lc u ra loi b, khng lm nh hng n cht lng ca in p mt chiu => kt qu l in p u ra tng i phng.Khi iu chnh bin tr VR1 , in p ly mu thay i, dn n Q2 thay i , dn n Q1 thay i => kt qu l in p ra thay i, VR1 dng iu chnh in p ra theo mun .4.3 Mch ngun Ti vi ni a nht.

S mch ngun n p tuyn tnh trong Ti vi mu ni a Nht .C1 l t lc ngun chnh sau cu Diode chnh lu.C2 l t lc u ra ca mch ngun tuyn tnh.Cu phn p R4, VR1, R5 to ra in p ly mu ULMR2 v Dz to ra p chun UcR3 lin lc gia Q3 v Q2, R1 nh thin cho n cng xut Q1R6 l in tr phn dng, l in tr cng xut ln .Q3 l n so snh v khuch i p d saiKhuch i in p d saiQ1 n cng xut ngun=> Ngun lm vic trong di in p vo c th thay i 10%, in p ra lun lun c nh .