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Khoa in t- n mn hc K thut mch in t. Trang

Li ni u

Nh chng ta bit, hu ht cc mch in t ngy nay uc cung cp nng lng bi ngun mt chiu. C th l

nhng ngun c sn nhng i a s u c bin i t in

li sang in mt chiu. Vic chuyn t in li xoay chiu

sang in mt chiu c thc hin d dng bng cc mch chnh

lu, v d mch chnh lu cu. Nhng in p mt chiu sau chnh

lu c gn sng ln, mt khc in p ny khng n nh, c th

d dng b bin i khi Uli thay i. iu ny gy nh hng rt

ln n s n nh ca mch in t v tui th ca cc linh kin

nh IC, transistorChng ta c th khc phc nhc im trn

bng cch mc sau chnh lu mt b n p m bo s n

nh cho cc thng s lm vic ca mch in t, khi m in p

li bin thin trong mt khong no .

Nh vy, chng ta thy rng, chnh lu bao gi cng i lin vin p, cng vic

thit k ra mt b ngun n p dng cho cc mch in t l

vic ht sc c bn

v rt cn thit i vi mt nh thit k. trong bi ny, chng

em xin trnh by cch thit k mt b n p vi u vo l in

li xoay chiu, u ra l in p mt chiu vi cc thng s cnu di y. Qua 2 hc k c hc b mn K

thut Mch in t ,chng em c trang b nhng kin thc

c bn v mch in t, gi y chng em mun c kt hp l

Lp TVTA_K2:Hong c Duy _ Trn nh Duyn _ Nguyn Vn o

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thuyt vi thc hnh, bt tay thit k mt mch in n gin

tip cn vi thc tin .

Nhm sinh vin chng em gm:

1. Hong c Duy2. Trn nh Duyn

3. Nguyn Vn o

Di s hng dn ca thy gio Nguyn ng Thng, chng em

hon thnh n Mch ngun tuyn tnh .

Vi s nhn thc ca mnh m c bit l c s hng dn tn tnh ca Thy

hng dn, cc Gio vin trong Khoa, cng nh s gip ca bn b, chng em

c gng hon thnh n ca mnh mt cch tt nht. Tuy nhin, l n u

tin cng vi nhiu b ng m c bit l gp phi nhiu s khc bit gia l

thuyt v thc t, la chn linh kin. Cng nh thi gian tng i hn ch nn

khng th trnh khi nhng sai st, do vy rt mong c nhn c s ng gp

kin ca Thy, C v bn b.

Chng em xin chn thnh cm n.

Vinh, ngy 28 thng 05 nm 2010.


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Ch tiu ca ngun n p : o Ur =10 15V.

o Ir =1A.

o Uli = (160230)

o gn sng : 3.75 %.


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PHN I

LA CHN S KHI V S NGUYNL CA MCH N P

Mch n p c thc hin nh cc khi nh sau:

Chng ta s xem xt chc nng, nguyn l hot ng ca tng

khi .


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1.1 .KHI BIN P.

Khi bin p c nhim v bin i in p li thnh mc in p

ph hp a vo khi chnh lu. N l mt khi gm cc cun dy

s cp, th cp c qun trn mt li thp gm cc l thp kthut in c dt mng ghp li vi nhau.

S d phi c cu to t cc l thp m khng phi l mt khi

thp c l v

trnh dng Fuc chy trn , gy to nhit .

Trong s mch in, bin p c k hiu nh sau:

Trong :

n1 : l s vng dy ca cun s cp.

n2 : l s vng dy ca cun th cp.

U1 : in p xoay chiu t u vo cun s cp.

U2 : in p xoay chiu u ra ca cun th cp.

Nguyn tc lm vic ca bin p nh sau:

Khi u vo s cp ca bin p ta t mt in p xoay chiu U1

= Uli l tn

hiu hnh sin (f=50Hz), trong li thp xut hin mt t trngbin thin theo quy

lut hnh sin ging nh u vo (f=50Hz). T thng bin thin ny

cm ng sang


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bn cun dy th cp mt in p xoay chiu cng dng hnh

sin vi f= 50Hz.

Mt khc, quan h v bin ca in p u ra v u vo ca

bin p l t l thun vi t s vng dy n1 v n2:

2

1

U

U=

2

1

n

n

Do , bin p c kh nng h p khi n1 > n2.

Vi bi thit k ny ta phi h mc in p li t (160-230) V,

xung cn ti thiu l 16.5V . Trn c s , ta s tnh ton cc

gi tr nh s vng dy cun trn hai cun s cp, th cp, ng

knh dy cun , tit din ca cc l thp ph hp vi yu cu trn.

1.2. KHI CHNH LU

Nhim v : bin i nng lng in xoay chiu thnh nng

lng in mt chiu.

Nguyn tc: s dng cc phn t tch cc c c tuyn A-V

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

Cc phn t tch cc thng c s dng l:

- Diode(Si, Ge): dng khi cng sut ra nh v trung bnh.

- Thyristor : dng khi cng sut ra ln, c th iu chnh

in p ra tu .

Trong chnh lu bng diode , cc mch chnh lu thng c

dng l:Mch chnh lu na chu k.

Mch chnh lu hai na chu k:

+ Mch chnh lu cn bng.

+ Mch chnh lu cu.


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Mch chnh lu bi p.

Ta ch quan tm ti mch chnh lu cu. Phng php chnh lu

cu c rt nhiu

u im hn so vi cc phng php khc l tnh n nh cain p ra sau chnh lu,in p ngc ti a m mi it phi

chu ng ch bng 1/2 so vi chnh lu na chu k v gn

sng ca phng php chnh lu ny cng gim i 2 ln so vi

chnh lu na chu k.

Nguyn l ca mch chnh lu cu:

Trong tng na chu k ca in p th cp U2 ,mt cp van c

ant dng nht v katt m nht m cho dng mt chiu qua vcp van cn li kho v chu mt in p ngc cc i bng bin

U2m .

Khi t0 0,tuy nhin

Ura = Uvo ch l ly l tng, thc t Ura = 2 Uvo 1,4V. in

p ra gim 1,4V so vi in p vo do st p tng cng trn hai

it thng trong mi na chu k.

i vi hai it tt trong mi na chu k, do in p nh ti a

phn b ngc u trn hai it do in p ngc ch cn mt

na.


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Sau y l gin thi gian th hin qu trnh trn

Vic chn gi tr ti a v dng v in p ngc m dit phi

chu ng ph thuc vo dng v p m mch n p phi chu

ng, cung cp cho ti.

1.3. KHI LC:

Tuy khi chnh lu bin i c in p xoay chiu thnh

in p mt chiu nhng in p ra sau chnh lu c gn sngln . Gi tr in p bin thin t 0 n 2 Uvo 1,4V mt cch chu

k,gi l s p mch (gn sng) in p hay dng in sau chnh

lu.S p mch hay gn sng ny l do cc sng hi gy nn

lm mt mt nng lng mt cch v ch v gy nhiu lon cho

s lm vic ca ti. gim gn sng ta s dng cc b lc.

Cc b lc thng c s dng l b lc LC, RC . Trong thit kny ta dng mt t lc RC c gi tr tho mn vi ch tiu gn

sng l 3.75%. Khi dng ti l t lc C ch xc lp , do hin

tng np v phng in ca t C mch lc lm vic ch

khng lin tc.


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S nguyn l mch lc bng t in:

Ta c cng thc tnh gi tr in dung ca t thng qua gn

sng nh sau:

Ur

= ttr

CR

TU

.

.

=> Ct

= trr

tr

r

RfU

U

RU

TU

...

.

=

Trong :

U r l chnh lch v in p

in tr ti R t ( tc l in tr u vo ca khi n p)

Tn s ca in p xoay chiu u vo chnh lu f ly gi tr

f=50Hz

1.4. KHI N P.

S khi ca khi n p:


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Thc cht ca b n p so snh l s dng bin php hi tip m

nn ta c s

tng ng nh sau:

Gi s v l do no y m in p ra tng ln mt lng Ur th

lng bin thin ny s quay tr li u vo nh b hi tip m.Tn hiu hi tip m ngc pha vi tn hiu vo do n s lm

yu tn hiu vo v ngc li khi in p ra b gim i mt lng

Ur th tn hiu vo s c xu hng tng ln chng li s gim

ny.

B khuych i phn hi trong ngun n p l b khuych i

mt chiu.

Nu ta gi h s khuch i ca khi khuch i l K, ca khi hi

tip l Kht v ca ton b mch sau khi c hi tip l K' .

Ta c quan h sau:

K' =htKK

K

.1+=

g

K

Trong , g l su ca phng php hi tip m (g > 1).

Vy, khi c hi tip m, h s khuch i gim i g ln.Mt khc, vi vic s dng mch n p ny (hi tip m), ta c

nhiu hiu ng khc rt c li:


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- in tr vo tng g ln, lm hiu sut t cc tng trc a

n tng ny tng ln, ng thi in p cung cp cho mch ny

t chu nh hng ca s bin i tr khng ra ca cc tng trc.

- in tr ra gim g ln, gip in p ra t b bin i khi gi trin tr ti thay i.

- nhp nhy gim g ln.

Tt c cc hiu ng trn u c nh hng rt tt trong vic n

nh dng in v in p ra.

Ta nhn thy khi hi tip m su : K.Kht>>1 do 1+ K.Kht K.Kht

. K =

htK

1

H s khuc i tng qut ch ph thuc vo h s Kht.

iu kin hi tip m l:

K + HT = 1800

K . HTK >> 1

Ta xt ln lt tng khi ca mch n p:1.4.1.Khi phn p:

To Upa t l vi in p ra, dng lm tn hiu so snh vi tn hiu

in p chun, to ra s chnh lch a vo khi khuch i

iu chnh, c nhim v trch 1 phn dng in ra, to ra mc

in p mt chiu Upa t l vi Ura dng lm thng tin so snh

vi Uchun , to ra mt s chnh lch t iu khin khikhuch i iu chnh.

Upa to ra nh b phn p in tr nh sau:


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Mch ny ch n thun l mch phn p thng thng.

Nu ISS

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phc v cho vic tnh su hi tip g, ta cn xc nh Kht, h

s khuch i ny l s tng hp ca khi phn p (Kpa) v khi

khuch i so snh (Kss).

Kpa =III

I

RR

R

+; Kss = '

e

c

r

r

Trong : rc :in tr tng ng xoay chiu ti cc C ca

Transitor

r e' :in tr trong cc E ca transitor r e' =Ie

mV25

Khi bit g ta c th xc nh c, in tr ra, vo v n nh

nhp nhy ca mch n p.

Vic chn transitor Q4 ph thuc vo cng sut m transitor phi

chu ng.

PD = UCE . IC

1.4.4. Khi khuch i iu chnh:

Trong trng hp ny ta cng s dng Transistor xy dng nn

khi khuch i iu chnh . Tnh hiu so snh c a vo chn

B ca Transistor, tn hiu ra c th ly chn E hoc chn C

- Nu ly chn E => K = 0 0

- Nu ly chn C => K = 180 0


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Dng Ico (dng r ngc ) s chy qua lp tip gip B-E , nh c

in tr R a dng ny xung t.

Tnh in tr trit dng nhit da theo cng thc sau:

R = RBE = Rtr =BI

V5,6

1.4.5 . S nguyn l ca khi n p:

k + ht =180.

* Nguyn l n p ca mch in nh sau:

Nu in p ra (Ura) trn ti tng , qua mch phn p UPA tng ,

cn Uchun vn


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gi gi tr khng i , lm cho UBEQ4 tng , khin cho Q4 dn in

mnh , IcQ4 tng, gy st p trn in tr R1 nhiu , lm cho UBQ3

gim khin cho Q3 dn in yu v ko theo s dn in yu ca

Q2 , Q3 trong tng khuch i Darlingtn ,ni tr tng ,gy st pUceQ1 tng , IcQ1 gim tc l Iti gim , lm Ura gim n nh

=> Ura=const.

Tng t Nu in p ra (Ura) trn ti gim , qua mch phn p

UPA gim,cn Uchun vn gi gi tr khng i , lm cho UBEQ4 gim ,

khin cho Q4

dn in yu, IcQ4 gim, gy st p trn In tr R1 t, lm choUBQ3 tng khin cho Q3 dn in mnh hn v ko theo s dn

in mnh ca Q2, Q3 trong tng khuch i Darlingtn , ni tr

gim , gy st p UceQ1 gim, dng IcQ1 tng tc l Iti tng, lm

Ura tng n nh => Ura = const

u im ca mch n p kiu b: n p tt, phm vi n p

rng v c th iu chnh c (bng cch thay i VR7 tng

ng vi thay i Kpa).

Cng sut ra ln khi chn Q1 c cng sut ln, do mch

in c s dng rt ph bin lm b ngun cho nhiu thit b

in t , my mc in t.

1.4.6. S nguyn l cui cng ca mch in

tng hp t nhng khi phn tch trn:


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PHN IITNH TON CHI TIT GI TR CC LINH KINS

DNG TRONG MCH

2.1 .KHI BIN P:

S dng bin p c bn trn th trng cng cc thng s c

sn:

Uv = 160 230 V


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Ur = -15 : 0 : +15 (30V)

Ir = 1 A

2.2.KHI LC.

xt t lc sau chnh lu :Ta chn in p ngng ca diode l 0.7V (s dng diode

silic)

Un = U r + 2 x 0.7 = 16.4V

Vy ta chn t c U max =50V

Ta c: U r =tt

r

CR

TU

.

.=> C t =

tr

r

tr

r

RfU

U

RU

TU

...

.

=

Vi gn sng l 3,75 %

=>100

75,3=

Ur

Ur=> Ur =

100

75,315x= 0,5625

Rt =r

r

I

U=

1

15= 15

=> FFxxx

Ct 1800018,0155625,0502

15===

Chn t lc ngun 2200 F

2.3.KHI N P. Khi khuch i iu chnh gm cc transistor mc kiu

Darlinton, ta cn tnh s transistor v cng sut chu ng ca

tng transistor.

Vi ICQ4min = 2mA ICQ3 10

min4CQI = 0,2mA

chn I BQ 3 =0,2 mA h s khuych i khi khuch i iu

chnh phi to ra l: =mA

A

2,0

1= 5000 ln


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Vi mi transistor c h s khuch i dng l 40 th ta cn dng

3 transistor to nn khi khuch i Darlinton ( = 40x40x40 =

64000 > 5000 ).

tnh cng sut ti a cho tng transistor ta s dng cngthc :

P = UCE . IC

Vi Q1 : PMax = (24,5 - 12) x 1 = 12.5(W) Ta chn Q1 :

H1061

Vi Q2 : PMax = (24,5 12,65) x40

1 296(mW )

Ta chn Q2 : D468

Vi Q3 : PMax = (24,5 13,3) x4040

1

x 7(mW)

Ta chn Q3 : C828

Chn R1 sao cho : ICQ4min 1 (mA)

UBQ3 = Ura + 3 x 0,65 14 (V)

Chn Uvomin = UBQ3 + 1= 15(V).

Ta c:

ICQ4min =1

3min

R

UU BQvao =1

1415

R

= 1 (mA)

Vy : R1 = 1 (K).

Khi

ICQ4max =

K1

145,24 = 10,5 (mA)

R5 thng c chn sao cho R5I = (2 5) mA .Nu chn

R5I = 3 mA ta tnh c :

R5 = 3103

612

x= 2000() => chn R5 = 2,2(K)


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Vi it Zener ta c th chn tu gi tr in p nh thng

ca Dz min

l gi tr ny phi nh hn Ura = 25V, tuy nhin gi tr Uz thng

cchn l 6V.

Cng sut ca Dz c th c tnh theo cng thc:

PDZmax = UZ . Izmax

Do :

Izmax = ICQ4max + R5I = 10,5 + 3 = 13,5 (mA)

PZmax = 6 x 13,5 = 81(mW) i vi transistor Q4 ta cng tnh cng sut ti a :

Pmax = (14 - 6) x 10,5 = 84 (mW) Ta chn Q4 : C828

Tnh in tr trit dng nhit ca cc transitos R2, R3, R4:

Ta chn in tr ny sao cho n bng vi in tr tng ng

nhn t cc

Baz ca mi Q.

Vi R4 : R4 =1

1

BQ

BEQ

I

U=

40

1

65,0

26 ()

Vi R3 : R3 =2

2

BQ

BEQ

I

U=

240

1

65,0

1 (K)

Vi R2 : R2 =3

3

BQ

BEQ

I

U=

340

1

65,0

= 41.6(K)

Xc nh R6, VR7 v R8: Ta da vo gi thit dng :Ipa >> IBQ4max (IVss) Ipa = IBQ4maxx 10 =

max4CQIx 10

=> Ipa = 1040

5,10x = 2,625(mA) . Khi tng 3 in tr R6 , VR7

v R8 phi tho mn :

RI + RII = R6 + VR7 + R8 =pa

ra

I

U= 310625,2

12x

= 4.57 (K)


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Kht = Kpa . Kss = 0,4 x4

'

4

EQ

CQ

r

r

Trong : rCQ4, r ' 4EQ : ln lt l in tr tng ng xoay

chiu v in trtrong cc E ca Q4 hai gi tr ny ln lt rCQ4 R1 1(K) ; r

'

4EQ =EI

mV25

Ta chn trng hp khi g nh nht (Kgs t gim nht) IEl

ln nht v bng 10.5(mA)

Thay vo phng trnh ta c:

Kht = Kpa . Kss = 0,4 .3

3

3

10.5,10

10.25

10.1

=168

Ta c : g =1+1 X 168=169 => nhp nhy cui cng l :

K'gs =g

Kgs =169

0375,0 = 0,022 %


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PHN IIITHC NGHIM , MCH IN , LP RP V

CCTHNG S O C

S mch trn capture SIS

S mch in c thit k trn Layout Plus


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PHN IV : KT LUN

Sau khi hon thnh bi thit k mch n p,chng em nhn

thy rng gia l thuyt v thc hnh c mi lin h rt cht ch .

Kt qu ca mch lp rp cho thy rng nguyn l hot ng

ca mch m ta xy dng trn l thuyt l hon ton ng n.

Nhng kt qu o c c trn mch thc t cng nhngthng s ca cc linh kin hon ton ph hp vi l thuyt .Tuy

nhin, do vic la chn linh kin trn th trng b gii hn nn

nhiu linh kin ch c lp vi tr s xp x, mt khc cc linh

kin khng hon ton l tng v do k nng lp rp ca chng em

cn nhiu hn ch, cho nn kt qu vn cha c hon ton

chnh xc, vn phi c mt qu trnh iu chnh mi t ch tiuyu cu .Qua ,chng em cng nhn thy rng mnh cn phi

rn luyn thm rt nhiu, khng ngng hc hi thm kin thc v

hon thin k nng thc hnh p ng vi yu cu ca mt k

s in T_Vin Thng trong tng lai.


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Chng em xin chn thnh cm n thy gio Nguyn ng

Thng gip chng em rt nhiu trong vic hon thnh

n mn hc ny.

TI LIU THAM KHO

[1] Phm Minh H

K thut mch in t. NXB khoa hc K thut, 1997

[2] Phm Trung Hiu S tay tra cu Transistor. NXB khoa hc K thut

[3] Nguyn Tn Phc

Mch in t. NXB khoa hc K thut, 2000


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