Do an Mach Nguon Bao Ve Dong 741
-
Upload
trongvan25 -
Category
Documents
-
view
46 -
download
1
description
Transcript of Do an Mach Nguon Bao Ve Dong 741
-
1
N TT NGHIP
Thit k mch ngun n p c in p ra 12V-5A c bo v dng
-
2
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.
-
5
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.
-
6
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.
-
7
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.
-
8
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.
-
9
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
-
10
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
-
11
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.
-
12
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
-
14
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.
-
15
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.
-
16
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.
-
26
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
-
27
* 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
-
28
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
-
29
=>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
-
30
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 :