1

N TT NGHIP

Thit k mch ngun n p c in p ra 12V-5A c bo v dng

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MC LC Trang

Mc lc ..........................................................................................................1

LI M U ....................................................................................................... 4

Phn I: O V KIM TRA LINH KIN .............................................................. 5

I.Transistor ......................................................................................................... 5

1. Kim tra trans npn hay pnp: .......................................................................... 5

2. o xc nh chn B, E v C: ......................................................................... 6

II.Thrysistor ........................................................................................................ 7

III. iode, in tr, t in ................................................................................. 8

1. Diode ............................................................................................................ 8

2. in tr. ....................................................................................................... 9

3. T in: ........................................................................................................ 9

Phn II: TNG QUAN V NGUN MT CHIU..............................................11

I. Khi nim chung v ngun mt chiu ..........................................................11

II. Bin p ngun, chnh lu v lc ngun. .......................................................11

1.Bin p ngun. ................................................................................................11

2. Chnh lu v lc ngun ..................................................................................11

III. n nh in p. .......................................................................................12

1. Khi nim n p...........................................................................................12

2. Phn loi n p: ...........................................................................................12

3. B n p tuyn tnh IC .................................................................................14

Phn III: THIT K NGUN N P C IN P RA 12V-5A ......................15

I. La chn phng php thit k. ...................................................................15

1. Bin p ........................................................................................................15

2. Mch chnh lu v b lc ngun ..................................................................15

3

3. Khi bo v dng .........................................................................................15

4. Khi n p ...................................................................................................15

II. S khi, s nguyn l. ........................................................................16

1. S khi ca khi ngun ..........................................................................16

2. S nguyn l . .........................................................................................16

3. S nguyn l mch ngun .......................................................................24

III. Tnh ton linh kin ....................................................................................25

1. Bin p ........................................................................................................25

2. Khi chnh lu v lc ngun ........................................................................26

3. Khi bo v dng .........................................................................................26

4. Khi ly in p ra.......................................................................................28

KT LUN ..........................................................................................................29

Ti liu tham kho : ...........................................................................................30

4

LI M U

Ngy nay cng vi s tin b ca khoa hc v cng ngh, cc thit b in t

ang v s c ng dng ngy cng rng ri trong hu ht trong cc lnh vc kinh

t- x hi cng nh trong i sng. Trong tt c cc thit b in t vn ngun

cung cp l mt trong nhng vn quan trng nht quyt nh n s lm vic n

nh ca h thng. Hu ht cc thit b in t u s dng cc ngun in mt

chiu c n p vi chnh xc v n nh cao. Hin nay k thut ch to cc

ngun in n p cng ang l mt kha canhj ang c nghin cu pht trin vi

mc nh to ra cc khi ngun c cng sut ln, n nh, chnh xc cao, kch

thc nh.

T tm quan trng trong ng dng thc t ca ngun in mt chiu n p

v cng c li nhng kin thc c hc v p dng thc hnh trong thc t, nn

em chn ti: Thit k mch ngun n p c in p ra 12V-5A c bo v

dng qua tm hiu k hn v nguyn l hot ng ca cc mch ngun ng

thi cng c them k nng trong thit k cc mch in tng t.

Trong qu trnh thc hin ti em xin chn thnh cm n thy gio : H

Tt Thng hng dn em hon thnh ti ny.

Do kh nng kin thc bn than cn hn ch, ti chc chn s khng trnh

nhng thiu st, em rt mong nhn c s ng gp kin thy ti c

hon thin hn.

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Phn I: O V KIM TRA LINH KIN

I.Transistor

Ta kim tra du pin ca que o ng ng h bng iode ( gi s que en +

pin, que - pin)

1. Kim tra trans npn hay pnp:

Transistor khi hot ng c th h hng do nhiu nguyn nhn, nh hng do

nhit , m, do in p ngun tng cao hoc do cht lng ca bn thn

Transistor, kim tra Transistor bn hy nh cu to ca chng.

Kim tra Transistor ngc NPN tng t kim tra hai Diode u chung cc

Ant, im chung l cc B, nu o t B sang C v B sang E ( que en vo B ) th

tng ng nh o hai diode thun chiu => kim ln , tt c cc trng hp o

khc kim khng ln.

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Kim tra Transistor thun PNP tng t kim tra hai Diode u chung cc

Katt, im chung l cc B ca Transistor, nu o t B sang C v B sang E ( que

vo B ) th tng ng nh o hai diode thun chiu => kim ln , tt c cc

trng hp o khc kim khng ln.

2. o xc nh chn B, E v C:

ng h thang x1 , t c nh mt que o vo tng chn , que kia chuyn

sang hai chn cn li, nu kim ln = nhau th chn c que t c nh l chn B(

nu que ng h c nh l que en th l Transistor ngc (npn), l que th l

Transistor thun (pnp)) 2 chn cn li l C v E.

Kim tra chn C,E:

+ Vi transistor npn ta t que en ng h vo 1 trong 2 chn, que vo chn

cn li. Can nhiu chn c que en nu trng hp c in tr (kim ng h ln)

th chn t vo que en l chn C, chn cn li l E.

+ Vi transistor pnp ta lm ngc li vi cc que v cc bc thc hin tng

t. Khi can nhiu kim ng h ln th chn t vo que l chn E, chn cn li

l C.

Tri vi cc iu trn l Transistor b hng.

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Transistor c th b hng cc trng hp .

* o thun chiu t B sang E hoc t B sang C => kim khng ln l transistor t

BE hoc t BC

* o t B sang E hoc t B sang C kim ln c hai chiu l chp hay d BE hoc

BC.

* o gia C v E kim ln l b chp CE.

II.Thrysistor

-o kim tra Thyristor

Kim tra du pin ca que o ng h bng iode (gi s que en l + pin, que

l pin)

Xc nh chn A, G, K: t que en v que ng h vo 2 chn bt k ca

thrysistor, trng hp no kim ln th chn t vo que en l chn G, chn t vo

que l chn K, chn cn li l A.

t ng h thang x1 , t que en vo Anot, que vo Katot ban u

kim khng ln , sau can nhiu => thy ng h ln kim , sau dng can nhiu

=> ng h vn ln kim => nh vy l Thyristor tt.

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III. iode, in tr, t in

1. Diode

K hiu diode thng:

Kim tra diode: t ng h thang x 1 , t hai que o vo hai u Diode,

nu :

o chiu thun que en vo Ant, que vo Katt => kim ln, o chiu o

kim khng ln l => Diode tt

Nu o c hai chiu kim ln = 0 => l Diode b chp.

Nu o thun chiu m kim khng ln => l Diode b t.

Cc loi Diode : Diode n p, Diode thu quang, Diode pht quang, Diode bin

dung, Diode xung, Diode tch sng, Diode nn in.

iode nn in c phn bit bi vch du trn iode; u c vch mang du

m, u cn li du dng.

Ta thng xc nh que m, dng ca ng h vn nng bng iode.

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2. in tr.

K hiu:

Vi in tr thng ta c th c vch trn in tr hoc dng ng h

vn nng (ng h s) xc inh.

Tr 4 vch: vch 1 l hng chc, vch 2 l hng n v, vch 3 l bi s ca

c s 10, vch 4 l sai s.

- Tr 5 vch: vch 1 l hng trm, vch 2 hng chc, vch 3 hng

n v, vch 4 l bi s ca c s 10, vch 5 l sai s.

3. T in:

Dng thang in tr o kim tra t in

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Ta c th dng thang in tr kim tra phng np v h hng ca t in,

khi o t in nu l t gm ta dng thang o x1 K, nu l t ha ta dng thang

o x1 hoc x10 .

Dng thang o x1K kim tra t gm

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Phn II: TNG QUAN V NGUN MT CHIU

I. Khi nim chung v ngun mt chiu

Ngun mt chiu c nhim v cung cp nng lng mt chiu cho cc mch

v cc thit b in t hot ng. Nng lng mt chiu ca n tng quan c ly

t ngun xoay chiu ca li in thng qua mt qu trnh bin i c thc hin

trong ngun mt chiu.

Yu cu i vi loi ngun ny l in p ra t ph thuc vo in p mng,

ca ti v nhit . t c yu cu cn phi dng cc mch n nh. Cc

mch cp ngun c in thng dung bin p, nn kch thc v trng lng ca

n kh ln. Ngy nay ngi ta c xu hng dung cc mch cp ngun khng c

bin p.

II. Bin p ngun, chnh lu v lc ngun.

1.Bin p ngun.

Bin p ngun lm nhim v bin i in p xoay chiu ca mng in

thnh in p xoay chiu c tr s cn thit i vi mch chnh lu v ngn cch

mch chnh lu vi mng in xoay chiu v mt chiu.

2. Chnh lu v lc ngun

Cc phn t tch cc dng chnh lu l cc phn t c c tuyn V-A

khng i xng sao cho dng in i qua n ch i qua n mt chiu. Ngi ta

thng dng chnh lu Silic, c cng sut nh hoc trung bnh cng c th dng

chnh lu Selen. c cng sut ra ln v c th iu chnh in p ra ty , ngi

ta dng Thyristor chnh lu.

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Cc s chnh lu thng gp l chnh lu na chu k, s chnh lu hai

na chu k, s chnh lu cu m trong s chnh lu cu c nhiu u im

hn c.

Mch chnh lu phi c hiu sut cao, t ph thuc vo ti v gn sng

ca in p ra nh.

Lc bng t in: Do s phng np t qua cc na chu k v do cc song hi

c r qua mch C xung im chung, dng in ra ti ch cn thnh phn mt

chiu v mt lng nh sng hi bc thp.

Ngha l tc dng lc cng r rt khi C v Rt cng ln. Vi b chnh lu dng

in cng nghip gi tr t C thng c gi tr t vi uF n vi nghn uF.

III. n nh in p.

1. Khi nim n p

Khi nim : l n nh in p u ra khng thay i khi in p u vo

thay i.

Nhim v n nh in p mt chiu ra ti khi in p v tn s in li

thay i, khi ti bin i rt thng gp trong thc t. in tr ra ca b ngun

cung cp yu cu nh, hn ch s ghp k sinh gia cc tng, gia cc thit b

cng chung ngun chnh lu.

Vic n nh in p xoay chiu c nhiu hn ch nht l khi in li thay

i nhiu. Dng b n p mt chiu bng phng php in t c s dng ph

bin hn c bit khi cng sut ti ra yu cu khng ln v ti tiu th trc tip

in p mt chiu.

2. Phn loi n p:

+ n p tham s ( n p dng iode zenner).

+ n p xung: l n p da trn nguyn l hi tip (nguyn l b), trong

phn t diu chnh lm vic ch xung. n p xung c nhng u im vt

tri so vi n p tuyn tnh nh sau:

+ n p tuyn tnh :

13

Trong phm vi ca n ny chng ta ch xt n mch n p c hi tip vi

nguyn tc thc hin cc s n p c hi tip, phn loi v mt s loi IC n p

tuyn tnh.

Nguyn tc mch n p tuyn tnh:

nng cao cht lng n nh, ngi ta dng b n p kiu b tuyn tnh.

Nguyn tc lm vic ca cc s n nh c hi tip c biu din nh sau.

Ur Ur

(in p mt chiu

cha n nh)

Trong mch ny, mt phn in p (dng in ) ra c a v so snh vi

mt gi tr chun. Kt qu so snh c khuch i ln v a n phn t iu

khin. Phn t iu khin thay i tham s lm cho in p (dng in) ra trn n

thay i theo xu hng tim cn n gi tr chun.

Ty theo phng php cu trc, cc s n nh c hi tip c chia thnh

hai loi c bn: n nh song song v n nh ni tip. Do s ni tip c tn hao

t hn s song song nn hiu sut cao hn v n c dng ph bin hn.

u im ca s song song l khng gy nguy him khi qu ti v n ngn

mch u ra. S ni tip yu cu phi c thit b bo v v khi qu ti ,dng qua

phn t iu chnh v qua b iu chnh s qu ln gy nn hng phn t iu

chnh hoc bin p.

Phn t iu khin

B khuch i

B so snh Ngun chun

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3. B n p tuyn tnh IC

thu nh kch thc cng nh chun ha cc tham s ca cc b n p mt

chiu kiu b tuyn tnh ngi ta ch to chng di dng vi mch, nh vic s

dng cng d dng hn. Cc b IC n p trn thc t cng bao gm cc thnh phn

t chnh l b to in p chun, b khuch i tn hiu sau lch, transistor iu

chnh, b hn dng.

Cc IC n p thng m bo dng ra khong t 100 mA n 1.5A in p

ti 50V, cng sut tiu tn khong 500-800 mW. Hin nay ngi ta cng ch to

cc IC n p cho dng ti 10A. Cc loi IC n p iu chnh thng dng l 78xx,

79xx, LM309, uA723, LM323, LM317

Ty thuc vo tham s k thut nh in p ra, dng ra, h s n nh in

p, kh nng iu chnh in p ra, di nhit lm vic, ngun cung cp n

nh theo thi gian m ngi ta ch to ra nhiu loi khc nhau.

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Phn III: THIT K NGUN N P C IN P RA 12V-5A

I. La chn phng php thit k.

Da vo cc tiu chun k thut ca khi ngun nh trn ta la chn phng

php thit k cho tng khi ca b ngun v t a ra s nguyn l ca b

ngun.

1. Bin p

y do ngun n p c s dng li in xoay chiu 220V-50Hz v

in p ( dng in) ra l 12Vdc-5A, cng sut cc i l 60W nn ta s dng mt

bin p c in p vo 220V v in p ra 15V, dng ra 5A.

2. Mch chnh lu v b lc ngun

Do nhng u im ca mch chnh lu cu nh in p ra t nhp nhy, in

p ngc m it phi chu nh hn so vi phng php cn bng nn ta s chn

b chnh lu cu.

B lc c nhim v san bng in p mt chiu dp mch Ur thu c sau

khi chnh lu thnh in p mt chiu t nhp nh hn.

Vi nhng c im ca phng php lc bng t in nh tnh n gin

cng nh cht lng lc kh cao nn y ta s s dng phng php lc ny cho

khi ngun.

3. Khi bo v dng

C nhim v bo v mch trong trng hp dng vo tng. Ta s s dng cc

tnh cht ca thrysistor, transistor, diode to nn khi bo v dng ph hp.

4. Khi n p

Theo yu cu thit k mch n p c in p ra 12V-5A nn ta s dng mt

IC n p thng dng l LM7812. Do LM7812 ch cho in p vo trong di 14,5V

-27V (vi cch mc thng thng) v in p ra 12V , dng ra 5.0mA-1.0A nn ta

s s dng thm 1 transistor cng sut gnh dng.

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II. S khi, s nguyn l.

1. S khi ca khi ngun

It

U1~ Uo1 Uo2 Ut Rt

Cc tiu chun k thut ca khi ngun:

+ Bin p 220/15V-5A AC-50Hz.

+ in p ra 12V DC

+ Dng in ra ti 5A

2. S nguyn l .

a. IC LM7812

Mt s c im thng s k thut c bn ca LM7812 nh sau:

+ Vin = 35V

+ Vout = 12V

+ Isc = 0.23A

+Iout = 1A

+5.0mAIoutImax

Bng km theo IC:

Bin

p

Mch

chnh lu n p

mt chiu

B bo

v dng

17

S nguyn l cu to ca LM7812 :

18

th tuyn tnh IC LM7812

19

b. Transistor cng sut TIP42C:

20

Bng km theo Transistor TIP42C

th tuyn tnh Transistor TIP42C:

21

c. Transistor 2SC2335:

22

Bng km theo transistor 2SC2335:

th tuyn tnh transistor 2SC2335:

23

24

3. S nguyn l mch ngun

S nguyn l:

Mch in linh kin :

25

Mch in i dy:

.

III. Tnh ton linh kin

1. Bin p

S dng bin p 220V /15V-5A cp ngun cho mch.

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2. Khi chnh lu v lc ngun

Khi in p li c gi tr ln nht Umax=240V, dng ln nht qua iode l

5A.

Do ta la chn cu 6A

in p sau chnh lu U=152 -1.4=19.8 V

Sau khi qua khi chnh lu cu th t lc cng phi m bo chu c in p

ln nht l 24(V).

=>Chn t C1= 1000uF/35V

Led 1 bo in p vo.

3. Khi bo v dng

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* Nguyn l bo v dng:

Gi dng sau transistor T1 l U1, U ,U ln lt l in p trn chn E v B

ca transistor T2, ta c:

U1 - U =U

U1 - U = U1 - I.R* = U

Ta c cc trng hp sau:

+ Khi I I : => U < U

=>Transistor T2 kha, khi bo v cha hot ng.

+ Khi I tng => U gim

+ Khi I > I : => U > U

=>Transistor T2 thng, c dng kch vo thrysistor hot ng, dng vo qua R2,

qua thrysistor v chn mass, ng thi transistor T1 b kha. Lc ny khng c

dng cp cho phn mch sau khi bo v nn ti v cc linh kin c bo v.

Tnh ton cho khi:

Ta c:

U1 - U =U

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U1 - U = U1 - I.R3 = U

transistor T2 thng th U > U

Vy I.R3 > 0.7 V

=>R3 > .

=

.

= 0.14

=>Ta chn R3 = 0.1 Cng sut tr l P=.R => =2.5 W

Chn tr phn p R4=R5=3300

4. Khi ly in p ra.

Do dng ra l 5A ta phi s dng mt transistor c kh nng chu c dng

ln hn hoc bng 5A. y ta s s dng transistor cng sut Tip42C ko

dng, v dng ra ln nht LM7812 l 1A.

in p vo khi ly in p ra l: U2= Ung 1.4 - - 0.1*

= 152 1.4 0.7 0.1*5

= 18.6 V

Do c thm tn nhit nn IC c kh nng cho dng ra 1.5 A

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=>Dng Ic qua transistor T3 l 3.5 A

St p trn transistor Tip42C khi hot ng l U= 3.1 V

=>R =

=

..

. = 1 => chn R7= 1 20W

T C2=470uF/16V

Dng LED 2 bo hiu in p u ra.

KT LUN

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Trong thi gian thc hin ti, vi s ch bo gip tn tnh ca thy

H Tt Thng, n nay ti: thit k ngun n p 12V-5A c bo v dng

c hon thnh. Chng em c gng vn dng nhng kin thc c hc

gii quyt nhng yu cu ca ti

Tuy nhin do thi gian v kin thc cn hn ch trong nhiu vn nn trong

qu trnh thc hin vn cn nhng thiu xt hn ch. Chng em rt mong nhn

c kin v gp ca cc thy c trong khoa v tng thit k cng nh m

hnh sn phm cu chng em sn phm c hon thin hn.

Cui cng chng em xin cm n qu thy c to iu kin tt nht chng

em c th hon thnh ti trong thi gian sm nht.

Ti liu tham kho :