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N MN HC

TCH HP MC I

NGHIN CU CH TO B KHUCH I CNG SUT M TN

Sinh vin thc hin:

Gio vin hng dn:

NHN XT CA GIO VIN HNG DN

ngy...thng...nm

Ch k ca gio vin hng dn

NHN XT CA GIO VIN PHN BIN

ngy...thng...nm 20

Ch k ca gio vin phn bin

LI NI U

Ngy nay,cng vi s pht trin ca k thut cng ngh cc b tng m cng c ci tin n mc hon ho nh h thng hifi stereo,...m thanh trung thc, hiu sut cao l cc ch tiu m cc nh thit k lun c gng t c mt cch tt nht.

Mch khuch i cng sut m tn ni chung cng n gin, nhng lm c mch khuch i m c cht lng cao khng phi l chuyn d dng . Bi v bn thn b khuch i c kh nng tiu tn mt lng ln cng sut, nn n phi c thit k sao cho nhit m n to ra khi hot ng mc in p cao, dng in ln s c tn ra mi trng xung quanh vi tc cao trnh b ph hy nhit. Do trnh khi s nh hng ca mo, nhiu, ... dn n tn hiu ra khng trung thc.

Vy nn c trng ca cc b khuch i cng sut l thng c khi tn nhit ln , kng knh, nhm tng din tch tip xc, trao i nhit tt hn vi mi trng.

Ngy nay, cc b khuch i cng sut c s dng rng ri trong cc my thu radio, my nghe bng v cc h thng stereo cht lng cao, trong cc thit b phng thu, sn khu, h thng loa m thanh.

Sau y nhm ti xin trnh by mt loi mch khuch i cng sut, y c th c xem l mch tng i n gin l khuch i cng sut s dng cp transitor D718&B668

D c s hng dn tn tnh ca gio vin hng dn, d rt c gng hon thnh n ny. Nhng khng th trnh khi nhng thiu st nht nh, rt mong nhn c cc kin ng gp tch cc t cc qu thy c v cc bn.

Chng em xin chn thnh cm n.

A.PHN M U

1.1 Yu cu ca ti

-Thit k b khuch i cng sut m tn s dng khuch i cng sut s dng IC LM4558 &cp transitor D718-B688

-Cng sut max 200W.

-iu chnh c m lng m sc.

-nhn tn hiu v khuch i tn hiu t mic khng dy s dng RF

1.2 Mc ch nghin cu

Mc ch nghin cu: nghin cu v ch to thnh cng mch khuch i cng sut m tn m bo t yu cu cng sut u ra v cht lng m tt nht, s dng micro khng dy thu pht tn hiu khong cch xa nht, tn hiu trung thc nht, mch in li nh gn, d lm v gi thnh r. Lm tin pht trin hn na cht lng ca cc b khuch i cng sut m tn s dng micro khng dy trong tng lai.

1.3L do chn ti

Do yu cu ca

1.4Chn phng n thit k

C nhiu phng n thit k cho ti ny nh mt s mch sau:mch OTL s dng ghp bin p u ra (Output Transformer Les), mch OCL s dng ghp t u ra(Output Capictor Les),mch BTL s dng ghp transistor u ra (Bridge Transistor Line Out),...cc mch ny d lm nhng cht lng th cha p ng c v cng sut cng nh cht lng m ra.

Chnh v vy chng em xin a ra phng n thit k mch khuch i cng sut m tn s dng LM4558& cp transitor D718-B688, y l bo mch c s dng kh ph bin hin nay trong cc mch khuch i cng sut m vi cng sut ra kh ln t vi trm W n vi trm KW ty theo cch mc.

B.PHN NI DUNG

CHNG I: L THUYT LIN QUAN

1.1Tng quan v mch khuch i

1.1.1Cc khi nim trong mch khuch i

1.1.1.1nh ngha mch khuch i

-Mch khuch i cng sut l mch c thit k sao cho cung cp mt lng ln cng sut cho ti tc l mch khuch i cng sut s to ra in p cao v dng in ln li ti cn cng sut ln. Mch khuch i cng sut c ng dng rt nhiu trong ngnh in-in t. Chng ta ch xt mch khuch i cng sut dng trong lnh vc m thanh (cn gi l mch khuch i cng sut m tn).

-Mch khuch i cng sut m tn dng to ra mt lng cng sut cung cp cho ti (ti thng l loa do chng i hi mt lng cng sut ln bin i tn hiu in thnh sng m). Mch khuch i cng sut thng c s dng rng ri trong cc my: radio, my thu hnh, my nghe bng, my tng m, cc h thng stereo, loa pht thanh, ...

1.1.1.2 S lc v mch khuch i

- Thng thng mtmch khuch il mt thit b hoc linh kin bt k no, s dng mt lng cng sut rt nh u vo iu khin mt lungcng sutln u ra. Trong cc ng dng thng dng, thut ng ny hin nay c dng ch yu cho cc b khuch iin t v thng thng l cc ng dng thu v ti to m thanh. Mi lin quan gia u vo v u ra ca mt b khuch i, thng c din gii nh l mt hm catn s c gi lham truynv bin ca hm truyn c gi l li

Nhng c tnh chung

Hu ht cc mch khuch i c nh gi bng mt s cc thng s:

1.0 li

lica mch khuch i l t s gia cng sut u ra v cng sut a vo iu khin, v thng thng c tnh trn thang o decibel (dB). (Trong thang o ny, tr s o t l vi quan h lgart ca hai tr s:

G (dB) = 10 lg(Pout/Pin))

1.1 Di ng ng ra

Di ng ng ra l mt di bin , thng s dng n v dB, l khong cch gia tn hiu ln nht v tn hiu nh nht m u ra c th phn nh c. V tn hiu nh nht thng b gii hn bi bin nhiu, nn ngi ta ly lun t s gia bin tn hiu ln nht v nhiu lm gii ng ng ra.

1.2 Bng thng v thi gian p ng ca mch khuch i

Bang thngca mt mch khuch i thng c xc nh theo s khc bit giatn s s ny cn gi l bng thng 3 dB. Trong trng hp nhng bng thng ng vi nhng chnh xc khc nhau thng phi ghi ch thm, th d nh (1 dB, 6 dB, v.v.).

Th d nh mt mch khuch i m tn tt phi c p ng bng phng t 20 Hz n 20 kHz (di m thanh m ngi ta nghe c), nh vy p ng tn s ca n phi m rng thm ra bn ngoi di ny t 1 n 2 bt mi bn. Thng thng mt mch khuch i m tn tt c bng thng t 10 Hz n 65 kHz.

Thi gian p ng (cn gi l thi gian tng trng) ca mt mch khuch i thi gian cn thit nng mc in p ng ra t 10% n 90% tn hiu nh khi t u vo mt in p bc (hm n v).

Nhiu mch khuch i b gii hn bi tc tng, thng l do tr khng ca mch dng in iu khin phi chu hiu ng t in vi im trong mch. iu ny l cho bng thng cng sut ln nht s thp hn so vi p ng tn s mc tn hiu nh.

i vi mt mch n gin ch c RC, cn gi ldp ng Gaus, thi gian tng trng c tnh gn ng:

Tr BW = 0,35,

Trong Tr l thi gian p ng tnh bng giy, v BW l bng thng tnh bng Hz.

1.3 Thi gian tr v v sai s

l thi gian ng ra tr v n mt mc no (th d 0,1%) ca tn hiu hon chnh. iu ny thng c t ra vi cc mch khuch i trc tung ca my hin sng v cc mch khuch i troing cc h thng o lng chnh xc.

1.4 Tc p ng

Tc p ngl tc thay i tn hiu cao nht ng ra, thng c tnh bng volt/giy (hoc mili giy, micro giy).

1.5 Tp m

Tp m (cn gi l ting n, nhiu), hin th s o c bao nhiu tp m c to ra trong qu trnh khuch i. Tp m l nhng thnh phn khng mong mun, nhng cng khng trnh khi ca cc linh kin v cc thnh phn trong mch. N c o bng thang decibel hoc bng in p nh ca nhiu u ra, khi khng c tn hiu u vo.

1.6 Hiu sut

Hiu sut l mt s o biu th mc bao nhiu cng sut u vo c chuyn ha thnh nng lng hu ch u ra ca mch khuch i. Cc mch khuch i lp A c hiu sut rt thp, trong khong t 10 20%, v hiu sut ti a l 25%. Cc mch khuch i lp B hin i c hiu sut trong khong 35 n 55%, vi hiu sut cao nht theo l thuyt l 78,5%. Cc mch khuch i lp D tin tin s dng k thut iu bin rng xung cho hiu sut ln n 97%. Hiu sut ca mt mch khuch i gii hn ln ca cng sut hu dng ng ra. Lu rng cc mch khuch i c hiu sut cao s chy mt hn, v c th khng cn n qut lm mt ngay c khi thit k ln n nhiu kilowatt.

1.7 tuyn tnh

Mt mch khuch i l tng phi l mt thit b tuyn tnh hon ton, nhng nhng mch khuch i thc t thng ch tuyn tnh trong mt phm vi gii hn no . Khi tn hiu c a n u vo tng, th u ra cng tng theo cho n khi t n mt im m mt linh kin no trong mch b bo ha, v khng th cho thm tn hiu ra. Ta ni tn hiu b ct xn, v y l mt trong nhng nguyn nhn gy ra mo dng.

Mt s mch khuch i c thit k hot ng theo kiu chp nhn gim bt li thay v phi chu mo dng. Kt qu l tn hiu chu mt hiu ng nn, V nu l tn hiu m thanh, th hiu ng ny khng lm tha mn ngi nghe lm. i vi cc mch khuch i ny, im nn 1 dB c t ra, xc nh l li tn hiu 1 dB s nh hn li cc tn hiu nh.

Tuyen tnh hal mt lnh vc ni bt. C rt nhiu k thut c s dng gim bt mo dng do khng tuyn tnh.

1.8 T s tn hiu trn tp m

T s: Tn hiu / Tp m = S / N

trong :

S: Tn hiu hu ch

N: Tp m (nhiu)

1.9 p ng tn s

p ng tn s (hay dy tn hot ng ca mch) c nh ngha l mt khong tn s m khi tn s tn hiu ng vo nm trong khong tn s ny th khuch i ca mch s l cc i.

-Khong tn s ny c gii hn bi:

fH : tn s ct cao.

fL : tn s ct thp.

Hiu s gia fH v fL c gi l bng thng ca mch: B = fH - fL

|A| Tn s thp

Am

2

Am

Tn s gia Tn s cao

-Nu tn hiu ng vo nm ngoi bng thng ca mch th khuch i ca mch s thay i theo tn s.

-Nu tn hiu ng vo tn s fH hay fL th khuch i ca mch tn s s gim i ln hay suy gim -3dB vi ln cc i.

-Dy tn s hot ng l tng ca mch khuch i m tn nm trong khong t 20Hz n 20KHz.

1.10 H s khuch i

H s khuch i l kh nng khuch i ca 1 mch c c trng bng mt thng s gi l li khuch i. Gm nhiu loi nh:

li in p (AV) :

I

O

V

V

V

A

=

.

li dng in (AI) :

I

O

I

I

I

A

=

.

li cng sut (AP) :

I

O

P

P

P

A

=

.

1.11 Hiu sut ca mch khuch i(():

Hiu sut ca b khuch i cng sut c nh ngha l t s gia cng sut tn hiu trung bnh c phn b trn ti vi cng sut trung bnh c ko t ngun:

%

100

.

(%)

CC

L

P

P

=

h

Vi: PL: l cng sut tn hiu trung bnh c phn phi trn ti.

PCC : l cng trung bnh c ko t ngun DC.

1.12 mo

Biu th cho s thay i hnh dng ca tn hiu ra so vi tn hiu vo ca mch. mo phn thnh nhiu loi:

Mo tn s: l dng mo xut hin do h s khuch i thay i khi tn s tn hiu thay i gy nn s bin i m sc. Nguyn nhn l do L, C t mch khuch i.

Mo pha: l do s dch gc pha ban u ca tn hiu ra so vi tn hiu vo. Mo pha gy nh hng xu n cht lng m thanh.

Mo xuyn tm: ch yu xy ra mch hot ng lp B.

1.1.1.3 Phn loi cc ch hot ng ca mch khuch i

Ty theo ch lm vic ca Transistor, ngi ta thng phn mch khuch i cng sut ra thnh cc loi chnh sau:

1.0 Khuch i cng sut loi A

Tn hiu c khuch i gn nh tuyn tnh, ngha l tn hiu ng ra thay i tuyn tnh trong ton b chu k 360o ca tn hiu ng vo (Transistor hot ng c 2 bn k ca tn hiu ng vo).

a) u im:

Khuch i c 2 bn k ca tn hiu.

Tn hiu t b mo dng.

b) Khuyt im:

Hiu sut thp: (( 25% nu dng ti l R v (( 50% nu dng ti l bin p.

Cng sut tiu hao ln.

1.1 Khuch i cng sut loi B

Transistor c phn cc ti VBE=0 (vng ngng). Ch mt na chu k m hoc dng ca tn hiu ng vo c khuch i.

a)u im:

Hiu sut cao (( 78,54%.

ch tnh c tiu th in p nn khng c hao tn trn Transistor.

b) Khuyt im:

Tn hiu ch tn ti trong na chu k.

Mo phi tuyn ln.

1.2 Khuch i cng sut loi AB

Transistor c phn cc gn vng ngng. Tn hiu ng ra thay i hn mt na chu k ca tn hiu vo (Transistor hot ng hn mt na chu k dng hoc m ca tn hiu ng vo).

c im:

Kt hp c hai c tnh ca ch loi A & B nn khc phc c nhc im ca ch loi A ln loi B.

Hiu sut kh cao (( 70%.

1.3 Khuch i cng sut loi C

Transistor c phn cc trong vng ngng ch mt phn nh hn na chu k ca tn hiu ng vo c khuch i. Mch ny thng c dng khuch i cng sut tn s cao vi ti cng hng.

a)u im:

Hiu sut rt cao (( 90 %.

b)Khuyt im:

Mo phi tuyn ln (70%). hn ch mo, ti phi l khung cng hng ghp LC.

-1.4 khuch i cng sut loi D

Cc mch khuch i Lp D, hay cn gi l cc mch khuch i iu bin rng xung, s dng k thut chuyn mch t c hiu sut rt cao (hn 90% cc mch khuch i hin i). V n ch cho php cc linh kin ch dng hon ton dn hoc khng dn, tiu tn trn linh kin s l ti thiu. Mt s loi mch khuch i iu bin rng xung n gin vn cn c tip tc s dng. Tuy nhin, cc mch khuch i kiu ng ngt hin i s dng k thut s, th d nh k thut iu bin sigma-delta, cho trung thc ti u. Trc y, lp D c s dng trong cc mch khuch i loa siu trm v gii hn ca bng thng v kh nng khng gy mo dng, sau ny cc tin b k thut cht bn dn cho php ch to cc mch khuch i c trung thc cao, di tn rng, vi t s nhiu trn tn hiu v h s mo dng thp tng ng vi nhng mch khuch i tuyn tnh cng loi.

1.5 Khuch i cng sut loi E

C vi loi mch khuch i lp khc, mc d n ch l bin th ca cc loi ban u. Th d nh mch khuch i Lp H v Lp G c xem nh bin th ca ln ngun cung cp (theo dng bc hoc lin tc) ty thuc vo tn hiu u vo. Lng tiu tn nhit c th gim bt, do in p ri trn cc linh kin thp. Loi ny c th kt hp vi cc lp kinh in. Cc mch khuch i kiu ny thng phc tp v thng ch s dng cho mt s ng dng c bit, th d nh trong cc tng cng sut rt ln. Tng t nh vy, cc mch khuch i Lp E v Lp F thng c m t trong cc ti liu cho cc ng dng tn s v tuyn khi hiu sut ca cc lp truyn thng thay i so vi nhng gi tr thc t. Cc lp ny s dng cc mch iu hng ha tn bc cao mng u ra, tng cng hiu sut, v c th xem nh hu du ca Lp C do cc c tnh gc dn ca chng.

Hnh 1.1 M t vic phn loi cc mch khuch i cng sut.

1.1.3 Cc loi mch khuch i cng sut m tn

1.1.3.1 OTL(Output Transformer Les)

a) c im:

c cp ngun n +Vcc v mass (0V).

Tng khuch i cng sut y ko dng transistor b ph i xng nn in th im gia ra loa bng na ngun.

Ng ra loa phi ghp vi mt t in Co.

b)u im:

m thanh t cht lng cao hn do p do p tuyn tn s rng.

Khng b suy gim tn hiu tn s cao do t k sinh ca bin p.

Hiu sut cao v khng tn hao trn bin th. Gi thnh r, kch thc nh so vi khi dng bin p ng ra.

c)Khuyt im:

Phi chnh in th DC ca im gia ra loa bng na ngun cung cp th tn hiu ng ra mi khng b mo.

Cp transistor cng sut nu khng phi l cp transistor b ph th d gy mo phi tuyn.

Tn hiu ra b mo tn s thp do t Cout gy ra (do t Cout khng th tin ti v cng).

1.1.3.2 OCL(Output Capictor Les)

a)c im:

c cp ngun i xng +Vcc & -Vcc nn in th im gia bng 0.

Tn hiu vo mch khuch i trc tip khng cn qua t.

Khng c t Co ng ra loa.

b)u im:

Kh nng chng nhiu tt do dng kiu khuyeesch i vi sai ng vo.

p tuyn tn s rng do khng dng t v bin th ng ra.

c) Khuyt im:

Cn dng 2 ngun.

Tn hiu ra loa trc tip nn in th DC im gia ng ra khc 0V s gy chy loa v vy cn c mch bo v loa.

1.1.3.3 BTL(Bridge Transistor Line Out)

a)c im:

BTL c hai loi:

Dng ngun n l mch ampli ghp t hai mch khuch i cng sut OTL.

Dng ngun n l mch ampli ghp t hai mch khuch i cng sut OCL.

b)u im:

Cho ra cng sut ln (gp 4 ln so vi OTL hay OCL) khi s dng vi ngun in p thp hoc dng cho cc Ampli c cng sut rt ln t 500W n vi nghn Walt.

c)Khuyt im:

Gi thnh cao.

Tn hiu ra d b mo, hai mch khuch i khng ging nhau, d b chy nu in th im gia khng bng 0.

1.3.3.4 Mt s mch tham kho khc:

1.0 Mch khuch i n in t chn khng (valve amplifiers)

Khi cc mch khuch i bn dn thay th rng ri cc mch khuch i n chn khng cng sut c nh, th cc mch khuch i n in t chn khng li c gi tr t nh Radar, thit b o m hoc cc thit b thng tin lin lc. Nhiu mch khuch i sng cc ngn vn s dng cc loi n chn khng thit k c bit, nh n,gyrotron,n song chy, v cc n sng cc ngn ny c cng sut ra cho mi linh kin l cao hn loi s dng linh kin mch rn.

1.1 Mch khuch i Tranzito

Quy lut chung ca linh kin tch cc l lm cho bin ca tn hiu u vo tr thnh mt tn hiu hu ch c bin ln hn u ra. S ln m tn hiu c lm cho ln ln gi l li s ph thuc vo thit k mch bn ngoi cng nh bn thn linh kin .

Nhiu loi linh kin tch cc c dng trong mch khuch i tranzito nh Tranzito hai mi ni (BJTs), Tranzito hiu ng trng o xt kim loi).

C nhiu ng dng cho mch khuch i. Mt s th d thng dng nht nh cc mch khuch i m tn cho h thng nghe nhc ti nh hoc trn xe t, cc h thng khuch i cao tn, pht x cao tn troing cc my thu v pht v tuyn...

1.2Mch khuch i thut ton (op-amps)

Mch khuch i thut ton l mt mch tch hp rn c th rp phi hp vi cc mch hi tip bn ngoi c th iu chnhhm truyn hay lica n.

1.3Mch khuch i vi sai

Mt mch khuch i vi sai l mt mch khuch i tch hp mch rn, c nhng mch hi tip bn ngoi iu khin hm truyn hoc lica n. N cng gn tng t vi mch khuch i thut ton, ch khc ch c u ra vi sai.

1.4 Mch khuch i th tn

Nhng nhng mch khuch i tn hiu th tn thc s c bng thng kh rng, ln n 5 MHz. Phi c nhng yu cu c bit v p ng bc c th thu c hnh nh tt.

1.5 Mch khuch i dc cho my hin sng

Nhng mch khuch i ny phi p ng c vi tn hiu th tn, iu khin n hnh ca my hin sng, v c th c bng thng ln n 500 MHz. Nhng c tnh ca p ng bc, thi gian p ng, mc qu ti v sai s c th lm cho vic thit k tr nn kh khn.

1.6 Mch khuch i phn b.

cc mch ny s dng ng truyn tm thi tch cc tn hiu v khuch i tng phn ring bit c c bng thng ln hn, trng hp s dng mt mch khuch i n l. Ng ra ca mi tng c th ni vi nhau qua ng dy truyn. Loi mch khuch i kiu ny thng c s dng trong cc tng khuch i dc cui cng cho my hin sng. ng truyn c th c tch vo bn trong n hnh.

1.7 Mch khuch i n sng chy (TWT)

Mch ny s dng trong cc ng dng khuch i vi ba tn s thp cng sut cao. Cc mch thng thng c th khuch i sut di tn s ca vi ba. Tuy nhin, chng thng khng d dng cng hng nh n Klix Trn.

1.8 n Klix - trn

Tng t nh n sng chy, nhng n ny c cng sut cao hn, v c tn s c trng. Chng cng thng nng n hn n sng chy, nn kh thch ng vi nhng ng dng di ng cn trng lng nh. n Klix - trn c kh nng cng hng, xut ra tn hiu chn la trong di tn c trng ca n.

CHNG II: THIT K V THI CNG

2.1 C s l thuyt ca ti

2.1.1 IC LM4558

-B 4558 l mt b khuch i ni knh kp(dual channel), vi kh nng tch knh cho php s dng knh i trong mt ng dng ampli duy nht.

thng s k thut:

-in p lm vic 18V 22V.

-in p u ra 10V.

-Tn s 2MHz.

-Tr khng u vo 1.0M.

-Cng sut max 1160 mW.

-Nhit hot ng 150oC.

-C ch bo v ngn mch.

-in nng tiu th thp.

-Ting n thp.

2.1.3.1 S khi IC 4558

2.1.3.2 S chn IC 4558

Chc nng cc chn:

-Chn s 1: u ra ca b khuch i thut ton AOUT

-Chn s 2: u vo o ca b khuch i thut ton AIN-

-Chn s 3: u vo khng o ca b khuch i thut ton AIN+

-Chn s 4: cp ngun VCC cho IC

-Chn s 5: u vo khng o ca b khuch i thut ton BIN+

-Chn s 6: u vo o ca b khuch i thut ton BIN-

-Chn s 7: u ra ca b khuch i thut ton BOUT

-Chn s 8: cp ngun +VCC cho IC 4558\

2.2.2-Transitor D71& B688

2.2.1 Hnh nh c th

Kch thc c th

2.2.2 Thng s k thut

-in p gia 2 chn C-B :VCB0 = 160(v)

-in p gia 2 chn C-E :VCE0 = 120(v)

-in p gia 2 chn E-B :VCB0 = 6(v)

-Cng sut :80W

-Nhit n nh hot ng: -55~150 oC

3.1 Thit k v phn tch mch

3.1.1 Mch ngun

bin p la chn l loi bin p 10A in p u vo 220V-50Hz, u ra l in p i xng xoay chiu 12V

Nguyn l lm vic:

+ cp ngun 12V i xng vo 2 u X1-1 v X1-3, x1-2 cp mt

Khi cp ngun, in p +12V qua R17-10k hn dng , kch m chn B ca transitor ngc T1, T1 thng bo ha, UCT1=UET1, in p ly ra 12v trn u 1, D6 mc ngc m bo in p +12V khng b thot xung mass

Tng t vi -12V, vi T2 l transitor thun

-C1, C2, C3, C4 lc ngun ra, san phng in p

3.1.2 Mch khuch i cng sut

3.1.2.1 Mch nguyn l

3.1.2.2 Mch in

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