Tai Lieu Thuc Tap Tot Nghiep

7/31/2019 Tai Lieu Thuc Tap Tot Nghiep

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MC LCTrang

M u

Phn I: C S L THUYT

I. Khi nim chung v ngun mt chiu

II. Bin p v chnh lu

III. Lc cc thnh phn xoay chiu ca dng in ra ti

IV. n nh in p

Phn II: THIT K NGUN MT CHIU N P C IN P RA

THAY I (0 15V) 3A

I. S khi ca khi ngun

II. La chn phng n thit k

Phn III: TNH TON CC THNG S K THUT V LP RP

MCH THC T

I. Tnh ton thng s cho tng khi mch

II. Lp rp mch thc t

Kt lun

Ti liu tham kho

M u


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Trng Vn QuytMSSV: 0851010060 n 1

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 cnh ang c nghin cu pht trin vi mc ch

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

(cc ngun xung).

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

da vo nhng kin thc c hc cng nh t tm hiu, em chn ti: Thit

k mch ngun mt chiu n p c in p ra thay i (0 15V) 3A qua

tm hiu k hn v nguyn l hot ng ca cc mch ngun ng thi cng c thm

k nng trong thit k cc mch in tng t.

Trong qu trnh thc hin ti em xin chn thnh cm n thy gio: Th.s V nh

Tng tn tnh hng dn gip em hon thnh ti ny.

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

thiu st, em rt mong nhn c s ng gp kin ca cc thy c v cc bn ti c hon thin hn.

Sinh vin thc hin

Trng Vn Quyt

PHN I:

C S L THUYT

I. KHI NIM CHUNG V NGUN MT CHIU

Thit k mch ngun DC n p c in p ra thay i 0-15v, 3A 2


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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 qut 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 (n p,

n dng). Cc mch cp ngun c in thng dng bin p, nn kch thc v trng

lng ca n kh ln. Ngy nay ngi ta c xu hng dng cc mch cp ngun

khng c bin p.

S khi ca mt b ngun hon chnh c biu din nh sau:

Hnh 1.1: S khi ca mt b ngun hon chnh

Chc nng ca cc khi nh sau:

- Bin p bin i in p xoay chiu U1 thnh in p xoay chiu U2 c

gi tr thch hp vi yu cu. Trong mt s trng hp c th dng trc tip U1 m

khng cn bin p.

- Mch chnh lu c nhim v chuyn in p xoay chiu U2 thnh in pmt chiu khng bng phng UT (c gi tr thay i nhp nh). S thay i ny ph

thuc vo tng dng mch chnh lu.

- B lc c nhim v san bng in p mt chiu dp mch UT thnh in p

mt chiu UO1 t nhp nh hn.

- B n p mt chiu (n dng) c nhim v n nh in p (dng in)

u ra ca n UO2 (IT) khi UO1 thay i theo s mt n nh ca UO1 hay IT . Trong

nhiu trng hp nu khng c yu cu cao th khng cn b n p hay n dng mt

chiu.

Thit k mch ngun DC n p c in p ra thay i 0-15v, 3A

Bin pMch chnh

l-u B lc

n p mtchiu

(n dng)

U1~ U

2~ U

TU

O1U

O2

IT

RT

3


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Ty theo iu kin v yu cu c th m b chnh lu c th mc theo nhng

s khc nhau v dng cc van chnh khc nhau. B chnh lu cng sut va v ln

thng dng mch chnh lu ba pha. Di y chng ta s i kho st tng khi nu

trn trong b ngun mt chiu.

II. BIN P NGUN V CHNH LU

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:

Hnh 1.2: Bin p ngun2. Chnh lu

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

Ampe khng i xng sao cho dng in i qua n ch i qua n ch i qua 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 (>100W) v c th iu

chnh in p ra ty , ngi ta dng Thyristor chnh lu.

Cc s chnh lu thng gp l chnh lu na chu k, s chnh lu haina 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 (t s gia cng sut ra v cng sut hu

ch u vo) cao, t ph thuc vo ti v gn sng ca in p ra nh.

Sau y ta s xt v s chnh lu hai na chu k v s chnh lu cu.

a. Mch chnh lu hai na chu k:



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c im ca mch chnh lu hai na chu k l trong c hai na chu k ca

in p xoay chiu u c dng in chy qua ti. C hai loi s chnh lu hai na

chu k: s cn bng v s cu.

D1

D2

Ct R

Ur

Uv

a. S cn bng

b. th thi gian ca in p ra

Hnh 1.3: Mch chnh lu hai na chu k

in p cc i khi khng ti: nUUU = 2

Trong Un l in p ngng ca diode, U2 in p trn cun th cp ca

bin p.

in p ngc t ln diode (trong trng hp C t 0): Ung = 2 U2hd.

b. Mch chnh lu cu:

S cu thng c dng trong trng hp in p xoay chiu tng i ln. Tuy

cng l s chnh lu hai na chu k nhng n u vit hn s cn bng ch

cun th cp c s dng ton b trong hai na chu k ca in p vo v in p

ngc t ln it trong trng hp ny ch bng mt na in p ngc t ln

trong s cn bng. in p ra cc i khi khng ti: nr UUU = 2 2 ngha l nh

hn cht t so vi in p ra trong s cn bng, v y lun lun c hai it mc

ni tip.


Ur

0 t

Khng c Ct

C Ct

5


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C t RU rUv

Hnh 1.4: Mch chnh lu cu

Ta thy rng trong tng na chu k ca in p th cp 2U , mt cp it c

ant dng nht v katt m nht m, cho dng mt chiu qua tR , cp it cn li

kha v chu mt in p ngc cc i bng bin mU2 . V d tng ng vi nachu k dng ca 2U , cp it 13 m, 24 kha. R rng in p ngc t ln

van lc kha c gi tr bng mt na so vi trng hp s chnh lu cn bng

xt trn, y l u im quan trng nht ca s cu. Ngoi ra, kt cu th cp ca

bin p ngun n gin hn.

Trong s 1.4, nu ni t im gia bin p v mc thm ti ta c mch

chnh lu c in p ra hai cc tnh. y thc cht l hai mch chnh lu cn bng.

Ct R

+Ur

Uv

Ct R

-Ur

Hnh 1.5: Chnh lu in p ra hai cc tnh

III. LC CC THNH PHN XOAY CHIU CA DNG IN RA TI

Trong cc mch chnh lu ni trn in p hay dng in ra ti tuy c cc tnh

khng i, nhng cc gi tr ca chng thay i theo thi gian mt cch chu k, gi

l s p mch (gn sng) ca in p hay dng in sau chnh lu.Mt cch tng qut khi ti thun tr, dng in tng hp ra ti l:



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=

=

++=11

0 cossinn

nn

nt tnBtnAIi

Trong 0I l thnh phn mt chiu v

=

=

+11

cossinn

nn

n tnBtnA l tng

cc sng hi xoay chiu c gi tr, pha v tn s khc nhau ph thuc v loi mchchnh lu. Vn t ra l phi lc cc thnh phn sng hi ny cho ti t p

mch, v cc sng hi gy s tiu th nng lng v ch v gy s nhiu lon cho s

lm vic ca ti.

Trong mch chnh lu hai na chu k thnh phn mt chiu 0I tng gp i

so vi mch chnh lu na chu k, thnh phn sng hi c bn (n=1) b trit tiu, ch

cn cc sng hi bc t n = 2 tr ln. V vy mch chnh lu hai na chu k c tc

dng lc bt sng hi.

Ngi ta nh ngha h s p mch KP ca b lc:

KP cng nh th cht lng ca b lc cng cao.

Ngi ta tnh ton rng khi chnh lu na chu k KP = 1,58, khi chnh lu

hai na chu k KP = 0,667.

thc hin nhim v lc ni trn, cc b lc sau y thng c dng:

1. Lc bng t in

Trng hp ny c nu ra trong trng hp ti in dung ca mch

chnh lu. Nh c t ni song song vi ti, in p ra ti t nhp nh hn.

C Rt Ur

Hnh 1.6: Lc bng t in

Do s phng v np t qua cc 1/2 chu k v do cc sng 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. Vic tnh ton h s p mch ca b lc dn ti ktqu:


Kp

=Bin sng hi ln nht ca i

t(hay u

t)

Gi tr trung bnh ca it(hay u

t)

7


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tP CR

K

2=

Ngha l tc dng lc cng r rt khi C v Rt cng ln (Rt tiu th dng in

nh). Vi b chnh lu dng in cng nghip (tn s 50Hz hay 60Hz), gi tr ca t

C thng c gi tr t vi F n vi nghn F (t ha).

2. Lc bng cun cm L

Mch lc bng cun cm L c biu din nh sau

Rt Ur

L

Hnh 1.7: Lc bng cun cm

Cun cm L c mc ni tip vi ti Rt nn khi dng in it ra ti bin thin

p mch, trong cun L s xut hin sc in ng t cm chng li. Do lm

gim cc sng hi (nht l cc sng hi bc cao). V mt in khng, cc sng hi

bc n c tn s cng cao s b cun cm L chn cng nhiu. Do dng in ra ti

ch c thnh phn mt chiu 0I v mt lng nh sng hi. chnh l tc dng lcca cun L.

H s p mch ca b lc dng cun L l:L

RK tP

3=

Ngha l tc dng lc ca cun L cng tng khi Rt cng nh (ti tiu th dng

in ln). V vy b lc ny thch hp vi mch chnh lu cng sut va v ln. Gi

tr ca cun cm L cng ln th tc dng cng tng, tuy nhin cng khng nn dng L

qu ln, v khi in tr mt chiu ca cun L ln, st p mt chiu trn n tng vhiu sut ca b chnh lu gim.

3. B lc hnh L ngc v hnh

Cc b lc ny s dng tng hp tc dng ca cun cm L v t C lc, do

cc sng hi cng gim nh v dng in ra ti (hay in p trn ti) cng t nhp

nh. tng tc dng lc c th mc ni tip 2 hay 3 mt lc hnh vi nhau. Khi

dng in v in p ra ti gn nh bng phng hon ton.



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Rt Ur

L

C

Hnh 1.8: Lc hnh L ngc

Rt Ur

L

C1 C2

Hnh 1.9: Lc hnh

Trong mt s trng hp tit kim v gim kch thc, trng lng ca b

lc ta c th thay cun cm L bng R trong mt lc hnh L ngc hay hnh . Lc

R gy st p c thnh phn mt chiu trn n dn ti hiu sut v cht lng ca

b lc thp hn dng cun L. Thng ngi ta chn gi tr R st p mt chiu trn

n bng (10 - 20)%U0 khong vi n vi k .

4. B lc cng hng

Hnh 1.10.a biu din b lc cng hng dng mch cng hng song song

LkCk mc ni tip vi ti Rt nh vy s chn sng hi c tn s bng tn s cng

hng ca n. Ngoi ra t C1 cn c tc dng lc thm.

Rt

L

CkC2

Rt

Lk

Ck

L

(a) (b)Hnh 1.10: Cc b lc cng hng



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Hnh 1.10.b biu din b lc cng hng dng mch cng hng ni tip

LkCk mc song song vi ti Rt. tn s cng hng ni tip ca mch LkCk tr khng

ca n rt nh nn n ngn mch cc sng hi c tn s bng hay gn bng tn s

cng hng. Ngoi ra cun L cn c tc dng lc thm.

IV. N NH IN P

Nhim v n nh in p (gi tt l n p) mt chiu ra ti khi in p v tn

s in li thay i, khi ti bin i (nht l i vi bn dn) 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 p 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 ra ti yu cu khng ln v ti tiu th trc tip

in p mt chiu.

Cc dng b n p trn thc t c chia lm ba loi chnh: n p kiu tham s (np dng it Zener), n p kiu b tuyn tnh (mch n p c hi tip) v n p xung.

Trong phm vi ca n ny chng ta ch xt n mch n p c hi tip vinguyn tc thc hin cc s n p c hi tip, phn loi v mt s loi IC n p

tuyn tnh.

1. Nguyn tc mch n p c hi tip

nng cao cht lng n nh, ngi ta dng b n p kiu b tuyn tnh (cn gil n p so snh hoc n p c hi tip). Nguyn tc lm vic ca cc s n nhc hi tip c biu din nh sau

Hnh 1.11: S khi minh ha nguyn tc lm vic ca cc


PHN TIU KHIN

B KHUCHI

B SO SNHNGUNCHUN

(in p mt chiucha n nh)

nh)

UrUr

10


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mch n nh c hi tip

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.

Hnh sau minh ha phng php ly tn hiu a v mch so snh khi n p

v n dng.

Hnh 1.12: Cch ly tn hiu a v b so snh

a. Khi n p b. Khi n dng.

C th thy rng, tt c cc ngun p (Ri ) c

thc hin theo phng php hi tip, u l nhng mch n p hoc n dng. Tuy

nhin do yu cu v mt cng sut nn, nn trong cc s n p hoc n dng cn

c thm mt b khuch i cng sut mc trong mch hi tip.

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.

S khi b n p kiu song song c cho hnh 1.13.a, nguyn l lm

vic ca loi s ny nh sau: Phn t iu chnh D iu tit dng in trong gii

hn cn thit qua iu chnh gim p trn in tr Rd theo xu hng b li: U2 =

U1 - URd , do in p ra ti c gi khng i. B to in p chun a E ch voso snh vi in p ra U2 b so snh v sai lch gia chng c khuch i

nh khi khuch i Y. in p ra ca Y s khng ch phn t iu chnh D. S bin

i dng in t 0 Itmax s gy nn s bin i tng ng dng in qua phn t

iu chnh t Itmax 0.


Rt

Ur

R

Rtin p

a v bso snh

in pa v bso snh

a. b.

11


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Hnh 1.13: a. S khi b n p mc song song

b. S khi b n p mc ni tip

Hnh 1.13.b biu th s khi b n p b mc ni tip, trong phn t

iu chnh D c mc ni tip vi ti, do dng in chy qua ti cng gn bng

dng in chy qua D. Nguyn l hat ng ca b n p da trn s bin i in

tr trong ca phn t iu chnh D theo mc sai lch ca in p ra (sau khi

c so snh v khuch i). V d do nguyn nhn no lm cho U2 bin i, qua

mch so snh v khuch i Y tn hiu sai lch s tc ng vo phn t iu chnh D

lm cho in tr ca n bin i theo chiu hng l Uc trn hai cc ca D b li s

bin i ca U1. Khi ta c U2 = U1 - Uc do c s bin i cng chiu gia U1 vUc , U2 s n nh hn.

Trong hai s trn, phn t iu chnh gy ra tn hao ch yu v nng

lng trong b n p v lm cho hiu sut ca b n p khng vt qu c 60%.

Trong s mc song song, cng sut tn hao ch yu xc nh bng cng

sut tn hao trn Rd v trn phn t iu chnh D l:

( ) ( ) DDtth IUIIUUP 221 ++=

( ) Dtt IUIUU 12 +=

Trong s mc ni tip, cng sut tn hao chi do phn t iu chnh quyt

nh:

( ) ttth IUUP 2=

Vy s ni tip c tn hao t hn s song song mt lng l U tId 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


D

Y

Ech

U1 RtU2

Udc

D Y

Ech

U1 Rt

It

U2

Id

a. b.

12


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

hoc bin p.

2. B n p tuyn tnh IC

thu nh kch thc cng nh chun ha cc cc tham s ca cc b n pmt 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 phn t

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

b hn dng.

Cc IC n p thng m bo dng ra khong t 100mA 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 in hnh thng dng l : serial 78xx

hay 79xx, LM 105, LM 309, A 723, LM323, LM 317, LM 337

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.v.v. m ngi ta ch to ra nhiu loi khc nhau.

PHN II

THIT K NGUN MT CHIU N P C IN P RA THAY I T

0 -15V

I. S KHI CA KHI NGUN



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Hnh 2.1: S khi ca mt b ngun hon chnh

Cc tiu chun k thut ca khi ngun:

- in p vo 220VAV - 50Hz.

- in p ra 0 - 15VDC.

- Dng in ra ti 3A.

- Cng sut cc i 45W.II. LA CHN PHNG P THIT K

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

p 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

cng sut cc i ca ngun l 45W (15VDC - 3A) nn ta s dng mt bin p c in

p vo 220V v in p ra 15V, dng ra 3A.

2. Mch chnh lu

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.3. B lc ngun

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

khi chnh lu thnh in p mt chiu UO1 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.4. Khi n p


Bin pMch chnh

l-u B lc

n p mtchiu

(n dng)

U1~ U

2~ U

TU

O1U

O2

IT

RT

14


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Theo yu cu thit k mch n p c in p ra thay i t 0V n 15V nn

ta s dng mt IC n p thng dng l LM317. Do LM317 ch cho in p ra trong

di 1.2V - 35V (vi cch mc thng thng) nn ta phi s dng mt cch mc phi

hp nhm iu chnh in p ra v mc 0V bng cch dng mt khi mch to ra

in p m.

a. Nguyn l khi mch n p c in p thay i

Tng qut v IC LM317

LM 317 l mt IC n p thng

dng c ng dng nhiu trong thc t

vi cc u im nh in p ra n nh

cng nh cch iu chnh in p ra khn gin (ch cn thay i gi tr mt

phn p).

Mt s c im thng s k thut

c bn ca LM 317 nh sau:

1,2V UOUT 35V.

IOUT MAX = 1,5A.

3V UIN - UOUT 40V.

IADJ = (50 100) A.

10 mA IOUT IMAX

S nguyn l cu to ca

LM317 c trnh by nh sau:


Hnh 2.2: IC n p LM317


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Hnh 2.3: S nguyn l IC LM317

Mch s dng IC LM317, vi cch mc thng thng (nh hnh 2.4) in p

ra ch nm trong khong 1,2V n 35V.

3

1

2

ADJ

OUTIN

LM317

0,1uF

C1 R1

R2

+

10uFC2

Hnh 2.4: S n p dng LM317

in p ra c th iu chnh c nh thay i phn p R1 , R2 . Dng in ra

ti chn ADJ c gi tr rt nh (50 - 100A). in p trn R1 l 1,25V. Khi inp ra c tnh theo cng thc:

21

2125,1 RIR

RU ADJra +

+=

Do IADJ c gi tr rt nh nn c th tnh gn ng Ura nh sau:

+=

1

2125,1R

RUra

Phng php iu chnh Ur v mc in p 0V:



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c th iu chnh Ur v mc 0V ta s dng cch mc mch phi hp nh

sau:

3

1

2

ADJ

OUTIN

LM317

0,1uF

C1 R1

R2

U1

Hnh 2.4: S nguyn l chnh mc in p ra v mc 0V.

Nguyn l chnh Ur v mc 0V nh sau:

T s nguyn l ta c:

+=

1

2125,11 R

RUrU

11

2125,1 UR

R

rU +

+=

Nu ta c gi tr U1 -1,25V th khi ta c th iu chnh c in p U r

v mc 0V.

b. Nguyn l ca khi to in p m

Ngun m c th c to ra n gin bng cch s dng mt cun bin p

c u ra m v dng. Nhng y ta s to ra mt ngun m bng cch dng cc

ngun dng c sn.

Vic to ra in p m t cc ngun in p dng c sn da trn nguyn l

ca mt ngun xung c bn s dng s phng v np ca cc t in theo chu k

nh tc dng ca mt xung vung c to ra t mt khi mch to xung.

S khi mch nh sau:



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LM7812

1

2

3

GND

+12VIN

+

C6 C7

8

37

2

6 5

4

1

VCC

OUT

GND

DISC

RST

CNTLTHR

TRIG

LM555

R1

R2

+

C1

C2

+

1000uF

C3

+1000uF

C4

1N4007D1

1N4007

D2

2

1

3

GND-5VIN

LM7905

12V

C5

DC IN

DC OUT (-5V)

Hnh 2.5: S nguyn l ca mch to in p m

Trong : Cc IC LM7812, LM555, v R1 , R2 , C1 , C2 c tc dng to ra mt

xung vung c tn s c xc nh theo R1 , R2 , C1 v bin khong 7,4V (theo

c tnh ca IC555). Khi to xung xung ny c th c thay bng bt k mt

mch to xung vung khc (v d nh mch a hi dao ng, mch dao ng dng

mch di pha ...)

Khi ti chn s 3 (chn OUT) ca IC 555 s c mt xung vung c bin

l U0 = 7,4V. Khi xung vung mc cao, dng in t chn 3 np vo t C3 ri qua

D1 xung t do t C3 c tch in.

Khi chn s 3 mc thp 0V, khi c th xem cc (+) ca t C 3 c nixung t. Trc t C3 c tch in U0 - 0,7 = 6,7V, do lc ny ti cc (-)

ca t C3 s c in p l - (U0 - 0,7) = - 6,7V, in p m ny s ko dng qua diode

D2 lm cho ti catot ca s tn ti mt in p m c gi tr - (U0 - 0,7) + 0,7 = 6V

nh c LM7905 in p ny c gi n nh mc -5V. Cc t C 4, C5 ng vai tr

l cc t lc.

Vy u ra ca mch ta to ra c mt in p m c gi tr - 5V.

c. Cch tng dng in ra ti



19/29


Do IC LM317 ch c th cho dng in ra ti cc i l 1,5A do c th

t c dng ra ti l 3A ta c th mc thm transistor iu chnh phi hp vi IC

n p nh sau:

3

1

2

ADJ

OUTIN

LM317U1

104

C1R1

R2

T

R3

DC OUT

-5V

U1

DC IN +C2

Hnh 2.5: IC n p dng thm transistor ngoi tng dng s dng.

T s ta c Ir = IC IE . Khi transistor tr thnh phn t chu dng thay

cho IC n p. Do vy ch cn chn loi transistor c kh nng chu c dng in

mong mun (3A) v tnh ton phn cc cho transistor hot ng.

PHN III:



20/29


TNH TON CC THNG S K THUT V LP RP MCH

THC T

I. TNH TON CC THNG S CHO TNG KHI MCH

1. Bin p

Hnh 3.1: Bin p ngun

Vi ch tiu Ura max = 15 V, theo c tnh k thut ca LM317 th in p vo

IC cn tho mn 3V UIn - UOut 40V, do UIn = 18V, mt khc phi cng thm

mt lng in p ri trn hai diode chnh lu, do in p ra trn cun th cp l

U2 = UIn + 2 0,7 = 19,4 V.

Xt khi in p li c gi tr nh nht U li min = 200 V, v vi in p ra yucu trn cun th cp l 19,4V ta c:

154,19

22002

22

1

2

1 ===U

U

U

U

n

n luoi

Khi in p li c gi tr ln nht Uli max = 240 V, in p ra ln nht trn

cun th cp:

2315

12240

1

212 ===

n

nUU (V)

Ta c dng in ra trn khi ngun cng l dng in ra trn cun th cp ca

bin p: Ira = I2 = 3A.

Do cng sut ln nht m bin p cung cp l:

P2 = U2 Ir= 23 3 = 69 W

Gi s rng tn hao trn hai diode chnh lu l 10% th cng sut thc ca

bin p l: 77%90

692 ==P W



21/29


Dng in chy trn cun s cp l: 2,015

3

152

1 ===I

I A

tnh din tch thit din ca li bin p ta da vo cng thc:

( ) PS 3,18,0 = (cm2)

( ) 93,18,0 77 =S (cm2)

Do ta la chn din tch tit din ca li bin th l 9 cm 2, v dng thp k

thut Tn - Silc.

Tnh ng knh dy cun bin p theo ch tiu mt dng 3A/mm

- Cun s cp: I1 = 0,2 A

07,0

/3

2,0

/322

11 ===

mmAmmA

IS (mm2)

ng knh dy cun bin p trn cun s cp:

3,007,0

22 11 ===

Sd (mm)

- Cun th cp: I2 = 3A

1/3

3

/3 222

2 === mmAmmAI

S (mm2)

ng knh dy cun bin p trn cun th cp:

128,11

22 22 ===

Sd (mm)

Tnh s vng dy ca bin p:

Da vo t s:( )

( ) ( )245

cmSUVol

nVong= ( )211

45

cmSUn =

Xt khi Uli max = 240 V th s vng dy trn cun s cp l:

( )1200

9

45240

45211

===cmS

Un (vng)

S vng dy trn cun th cp l:

8015

1200

151

2 ===n

n (vng)

Vy ta la chn bin p c cc c tnh sau:

- Din tch tit din li bin p: S = 9 cm2

- ng knh dy cun bin p:

+ S cp : d1 = 0,3 mm + Th cp: d2 = 1,128 mm



22/29


- S vng dy cun bin p:

+ S cp : n1 = 1200 vng + Th cp: n2 = 80 vng

2. Khi chnh lu

Khi in p li c gi tr ln nht U li max = 240 V, in p ngc t lndiode chnh lu:

2315

122402

1

212 ====

n

nUUUng (V)

Dng in ln nht qua diode: ID = I2 = 3A.

H s gn sng (khi Ct = 0) W = 0,49.

Tn s ca in p ra b chnh lu: 100Hz

Do ta la chn diode chnh lu loi: IN5408.

3. Khi lc ngun

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

in p ln nht l 23 V. Do ta chn mt t lc c Umax = 25 V.

xc nh in dung ca t ta da vo gn sng sau khi chnh lu:

gst

CLL

KR

TC

3

=

Chn gn sng sau khi chnh lu l Kgs = 5% = 0,05.

Chu k chnh lu: 01.050.2

11===

CL

CLf

T (s)

in tr ti tng ng: 53

15===

r

rt

I

UR

Khi : 013,005,0.5.3

01,0

3===

gst

CL

L KR

T

C (F)

Vy ta chn t lc : 2200 F / 25V.

3. Khi phn p ly in p ra



23/29


3

1

2

ADJ

OUTIN

LM317U1

104

C1

680

R1

10K

R2

-5V

DC OUT (0V : +15V)

U1

DC IN

Hnh 3.2: Khi phn p

Phn p R1 v R2 c nhim v lm thay i in p ra theo s bin thin ca

bin tr R2.

T s ta c:

+=

1

21 125,1 R

RUUr

11

2125,1 URRUr +

+=

Khi to in p m c nhim v to ra mt in p m U 1 = - 5V. Khi

to ra mt in p bin thin t 0 - 15 V th:

15125,10 11

2 +

+ U

R

R

20125,151

2

+

R

R

1531

2 R

R

121 153 RRR

Nu chn R1 = 560 th ta c 1,68 K R2 8,4 K. Nh vy ta c th

chn mt bin tr 10K.

4. Khi to in p m



24/29


Khi to in p m c xy dng trn c s mt ngun xung c bn cho

in p ra l - 5V (do s dng IC n p LM 7905) v dng ra ti c th t n 1A

(theo c tnh ca IC LM555 v LM7905).

LM7812

1

2

3

GND

+12VIN

U2

+

100uF

C5

104

C6

8

37

2

6 5

4

1

VCC

OUT

GND

DISC

RST

CNTLTHR

TRIG

LM555

U3

1K

R4

10K

R5

+

1uF

C7

103

C8

+

1000uF

C9

+1000uF

C10

1N4007D6

1N4007

D7

2

1

3

GND

-5VIN

LM7905U4

12V

-5V

104

C11

DC IN

DC OUT (-5V)

Hnh 3.3: Khi to in p m.

Ngun cung cp: Ta s dng mt ngun n p n gin vi IC LM7812

to ra mt in p n nh +12V, cung cp cho IC to xung.

Khi to xung vung: IC LM555 c nhim v to ra mt xung vung c

tn s v bin n nh.

Tn s do LM555 to ra c tnh theo cng thc:

( )BA

RRTf

2

44,11

+==

Nu chn RA = R4 = 1K, RB = R5 = 10K v C = 1 F th tn s ng m ca t

C9 l:

( ) ( )131

10.1010

44,1

2

44,11643=

+=

+==

BA RRTf (Hz)

Nguyn l hot ng ca mch c gii thch nh phn II v in p ra

lun t -5V n nh do s dng LM7905.

5. Transistor tng dng ra ti

tng dng ra cho ngun ta s dng cch mc nh sau:



25/29


3

1

2

ADJ

OUTIN

LM317U1

104

C2

680

R1

10K

R2

B688T

2.2/0.5W

R3

DC OUT (0V : +15V)

-5V

U1

DC IN

Hnh 3.4: IC n p dng thm transistor ngoi tng dng s dng.

Do dng ra l 3A ta phi s dng mt transistor c kh nng chu c dng

ln hn hoc bng 3A. y ta s s dng transistor B688.

T s trn ta thy phn cc cho transtor hot ng th st p trn in

tr R3 phi l 0,7 V, dng qua n l 0,3A (Dng qua LM317). Do ta chn in tr

R3 nh sau:

( )=== 2.23,07,0

1

1

3R

R

IUR

( )WIUP RRR 21,03,0.7,0. 111 ===

y ta s dng mt in tr c R3 = 2,2 , cng sut P = 0,5 W.

6. Khi lc in p ra

tng n nh cng nh lc cc nhiu ca in p ra ta s dng thm

mt khi lc in p ra gm t C3 = 100F / 25V v C4 = 100 nF.

Sau khi tnh ton chi tit cho cc khi ta tin hnh ghp ni cc khi vi

nhau thnh s nguyn l nh sau:



26/29


S Layout


+

1 0 0 u FC 1

L M 7 8 1 2

1

2

3

G N D

+ 1 2 VI N

U 2

+

1 0 0 u F

C 5

1 0 4

C 6

8

37

2

6 5

4

1

V C C

O U T

G N D

D I S C

R S T

C N T LT H R

T R I G

L M 5 5 5

U 3

1 K

R 4

1 0 K

R 5

+

1 u F

C 7

1 0 3

C 8

+

1 0 0 0 u F

C 9

+1 0 0 0 u F

C 1 0

1 N 4 0 0 7

D 6

1 N 4 0 0 7

D 7

2

1

3

G N D

- 5 VI N

L M 7 9 0 5U 4

6 8

R

L

3

1

2

A D J

O U TI N

L M 3 1 7U 1

1 0 4

C 21 0 4

C 4

5 6 0

R 1

1 0 K

R 2

1 2 V

- 5 V

ACIN22

0V)

D C O U T :

+

1 0 0 u F

C 3

1 0 4

C 1 1

D 1

D 2

D 3

D 4

B 6 8 8T

2 , 2 / 0 , 5 W

R 3

B i e n a p

snguynlngunmtchiu

np

cinp

r

athayi(0

15V)

3A


27/29


S mch thc t

KT LUN



28/29


Sau mt thi gian tm hiu v thit k, em hon thnh n thit k ca

mnh vi yu cu thit k khi ngun mt chiu n p c in p ra thay i (0

15V) 3A. Kt qu thit k c lp rp thnh mch in v kt qu hot ng ca

mch t c nhng yu cu thit k.

Qua ti thit k ny gip em c th p dng nhng kin thc hc vo

thc t ng thi nng cao kh nng t tm hiu v thit k cc mch in tng t.

T nhng kin thc thu c trong qu trnh thc hin n ny s gip em c

thm kinh nghim thit k cc mch in mi c phc tp hn.

Cui cng em xin chn thnh cm n thy gio: Th.s V nh Tng tn

tnh hng dn gip em hon thnh n thit k ny.

Sinh vin thc hin

Trng Vn Quyt

Ti Liu Tham Kho



29/29


DATASHEET ca cc IC LM317, LM 7812, LM 555, LM 7905, vTransistor B688

Wedsite: dientuvietnam.net, 4tech.com..

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