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8/6/2019 bai giang chuong 2
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CHNG 2
MCH KHUCH I CNG SUT M TN
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1. MCH KCS M TN LP A (nhc li)
u im:
Mo phi tuyn t do chn c on c tuyn lmvic ca transistor.
Nhc im:
Cng sut tn hiu ra nh do mch ch lm vic vitn hiu nh.
Hiu sut b do phi phn cc DC trc chotransistor gy tiu tn DC khng mong mun.
Lp A: Transistor ch lm vic trong c chu k ca tnhiu ng vo phi phn cc DC cho transistor.
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2. MCH KCS M TN LP B
Mch KCS m tn lp B transistor ghp yko (push pull) dng bin p.
Mch KCS m tn lp AB transistor ghp bph: mch OTL, mch OCL.
Vn nng cng sut cho mch KCS m tn.
Lp B: Transistor ch lm vic trong 1 bn k catn hiu ng vo Vi tn hiu xoay chiu c 2 bnk ta phi dng 2 transistor.
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2.1. Mch KCS lp B transistor ghp y kodng bin p (tt)
dng ti khng mo
IP1 = IP2 = IP
Hot ng ca 2 transistor phii xng Q1Q2, cc bin p T1v T2 phi c im gia cun thcp v cun scp tng ng.(center-tapped transformer)
Dng trung bnh ca nguncung cp:
IP1
-IP2
IP1
iT2
iT1
Vi
iL
t
t
t
t
iS t
T/2 T 3T/2 2T
IP2
IP1 IP2
P
T
PSAV
IwtdtI
TI
2sin
22/
0
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2.1. Mch KCS lp B transistor ghp y kodng bin p (tt)
Cng sut trung bnh phn phi trn ti PL:
LPL
L
PLPLPLL RI
R
VIVP
22
2
1
2
1
2
1
Vi VPL, IPL l bin in p nh v bin dng nh ca ti:
P
S
PPL
P
P
SPL
IN
NI
VN
NV VP , IP l bin p v bin
dng khng mo ng ra cacc transistor.
LP
S
P
L
P
P
SPPL RI
N
N
R
V
N
NIVP
2
22
2
2
1
2
1
2
1
Suy ra:
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Cng sut trung bnh phn phi trn ti cc i:
2.1. Mch KCS lp B transistor ghp y kodng bin p (tt)
LP
S
P
L
P
P
SPPL RI
N
N
R
V
N
NIVP
2
max
22
max
2
maxmaxmax2
1
2
1
2
1
T ng ti mt chiu DCLL,ta c bin p ng ra cami transistor cc i:
VPmax = VCC
Suy ra:L
CC
P
SL
R
V
N
NP
22
max2
1
Trng hp NP = NS L
CCL
R
VP
2
max2
1
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Cng sut trung bnh ca ngun cung cp PS:
2.1. Mch KCS lp B transistor ghp y kodng bin p (tt)
PCCSAVCCS
IVIVP
2
Cng sut trung bnh cc i ca ngun cung cp PSmax:khi ti tiu th cng sut cc i PLmax.
maxmax
2max
PCCSS
IVPP
LP
Vi:L
CC
P
S
L
PL
P
SPL
P
SP
RV
NN
RV
NNI
NNI
2
maxmaxmax
Suy ra:
L
CC
P
SS
R
V
N
NP
22
max
2
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Cng sut tiu tn ca cc transistor:
2.1. Mch KCS lp B transistor ghp y kodng bin p (tt)
LSndissipatiodtntiuttC PPPPP )()(Cng sut tiu tn ca 1 transistor: Pd/2
Cng sut tiu tn cc i ca cc transistor:
)(2
12 222
P
L
P
P
S
L
P
P
SCCLSC Vf
R
V
N
N
R
V
N
NVPPP
Ly o hm, kho st cc tr ta suy ra cng sut tiu tncc i ca cc transistor:
CCP VV
2 th
L
CC
P
SC
R
V
N
NP
22
2max
2
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2.1. Mch KCS lp B transistor ghp y kodng bin p (tt)
CC
P
L
P
P
SCC
L
P
P
S
S
L
V
V
R
V
N
NV
R
V
N
N
P
P
42
2
1
2
22
Hiu sut cc i khi PLmax
v PSmax
VPmax
= VCC
%5.784max
maxmax
S
L
P
P
Hiu sut:
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u im: Do mi transistor lm vic 1 bn k tn hiu vo nnmch c th hot ng vi tn hiu c bin lncngsut ra trn ti ca mch ln.
Hiu sut cao.
Nhc im: Mo xuyn tm do ngng dn ca transistor.
Bin p cng knh, t tin. tn hiu ng ra khng mo th cc bin p trongmch phi c cun scp (T2) v th cp (T1) i xng.
Mo tn hiu cun thc cp bin p khi tn hiu vo
cun scp ln do hin tng t tr.
2.1. Mch KCS lp B transistor ghp y kodng bin p (tt)
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Bi tp p dng:
Mt mch khuch i cng sut m tn lp B transistorghp y ko dng bin p c dng collector nh v inp nh ng ra mi transistor l 4 (A) v 12 (V). Nguncung cp 24 (V), t s bin p Np:Ns = 1:1. Gi s b qua
cc tn hao dy qun ca cc bin p. Hy tm:a. Cng sut trung bnh phn phi trn ti.
b. Cng sut trung bnh c cung cp t ngun DC.
c. Cng sut tiu tn trn mi transistor.
d. Hiu sut ca mch trong trng hp ny.e. Gi s ti 8 (), tnh cng sut cc i phn phi
trn ti.
2.1. Mch KCS lp B transistor ghp y kodng bin p (tt)
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Bi gii:Theo bi: VP = 12 (V), IP = 4 (A), Np/Ns = 1.
a. Cng sut trung bnh phn phi trn ti: PL= 0.5VPIP = 24 (W)
b. Cng sut trung bnh c cung cp t ngun DC:PS = VCCISAV = VCC(0.636IP) = 61.115 (W)
c. Cng sut tiu tn trn mi transistor:
Pd = PS PL = 37.115 (W) 1 transistor: Pd/2 = 18.5575 (W)
d. Hiu sut: = PL/PS = 39.27 %
e. Cng sut cc i phn phi trn ti nu RL = 8 ():
PLmax = 0.5(VCCVCC)/RL = 36 (W).
Bi tp v nh: 2.13, 2.14, 2.15, 2.16, 2.17, 2.18.
2.1. Mch KCS lp B transistor ghp y kodng bin p (tt)
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Lp AB: Transistor ch lm vic trong 1 bn k catn hiu ng vo nhng trnh mo xuyn tm taphi phn cc trc cho mi transistor in p mi ni
VBE v in p mi ni VEB ln (0.7 V) khi ctn hiu xoay chiu ng vo th transistor s dn ngay.
Do hn ch ca mch KCS T dng bin p nn trnh cc hn ch th ta khng dng bin p trongcc mch KCS T na mch KCS T khngdng bin p ng ra dng OTL (OutputTransformerLess).
2.2. Mch KCS lp AB transistor ghp b ph
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2.2.1. Mch KCS m tn OTL
iL
iT2
iT1
Re2
D1
Q1
D2
M
Re1
RL
R1
Vi
R2
+Vcc
B1
Q2
Co
CiB2
Phn tch mch v nguyn lhot ng:
in trR1, R2, diode D1, D2: tophn cc trc cho transistor Q1,Q2. Cc dng khc:
VRQ3
Ry
B1
Rx
B2
D1VR
D2
B1
B2
D1
VR
B1
B2
VR
B1
B2
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2.2.1. Mch KCS m tn OTL (tt)
iL
iT2
iT1
Re2
D1
Q1
D2
M
Re1
RL
R1
Vi
R2
+Vcc
B1
Q2
Co
Ci
B2
Cc in trRe1, Re2: l cc in trn nh nhit cho Q1, Q2.
T in Co: cch ly DC ti vi ngra tng cng sut (M) v ng vai trngun cung cp cho Q2 hot ng bn k m ca Vi nn gi l t xutm.
Bn k dngca Vi:Q1 dn, Q2khng dn i
T1
, iT2
= 0.
Bn k m ca Vi:Q1 khng dn,Q2 dn iT2, iT1= 0.
Dng ti: iL = iT1- iT2Dng ngun: i
S= i
T1
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2.2.1. Mch KCS m tn OTL (tt)
dng ti khng mo
IP1 = IP2 = IP
Hot ng ca 2 transistor
phi i xng Q1Q2 (chntheo cp), R1 = R2, Re1 = Re2, inth ti im gia VM = Vcc/2.
Dng trung bnh ca ngun
cung cp:
P
T
PSAV
IwtdtI
TI
2/
0
sin1
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2.2.1. Mch KCS m tn OTL (tt)
Cng sut trung bnh phn phi trn ti cc i khi: VP = Vpmax
Xt ng ti DCLL:
QAB 0
VCC/2
2max
CCP
VV
L
CC
Le
LL
R
V
RR
RP
22
max8
1
Nu chn Re
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2.2.1. Mch KCS m tn OTL (tt)
Cng sut trung bnh ca ngun cung cp PS:
PCCSAVCCS
IVIVP
Cng sut trung bnh cc i ca ngun cung cp PSmax
:
khi ti tiu th cng sut cc i PLmax.
maxmax
max
PCCSS
IVPP
LP
)(2maxmax
Le
CC
Le
PPRR
V
RR
VI
)(2
2
maxmax
Le
CCSS
RR
VPP
LP
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2.2.1. Mch KCS m tn OTL (tt)
Cng sut tiu tn ca mt transistor:
LSndissipatiodtntiuttC PPPPP )()(
CC
P
Le
L
eL
PCC
L
P
Le
L
S
L
V
V
RR
R
RR
VV
R
V
RR
R
P
P
21
2
1 22
Hiu sut cc i khi Plmax v PsmaxVPmax = VCC/2
B
Le
L
S
LAB
RR
R
P
P
4max
maxmax
Hiu sut:
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2.2.1. Mch KCS m tn OTL (tt)
u im:
Mch khng dng bin p nn khc phc cc nhcim ca mch KCS T dng bin p.
Tn hiu ra khng mo xuyn tm.
Hiu sut cao.
Nhc im:
Mch dng t xut m nn lm suy hao tn hiu.
Do suy hao ca t khng ng u theo tn s nn dngt xut m s hn ch nhng tn hiu c tn s thp mch hn ch tn hiu siu trm. Tn s ct thp ca mch:
oLe
CCRR
f)(2
1
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2.2.1. Mch KCS m tn OTL (tt)
Bi tp p dng:Cho mch KCS T dng OTL c ngun cung cp 20 (V), cc in trR1 = R2 =10 (K), Re1 = Re2 = 1(), RL = 8 (). Diode dng loi Si. T Co = 500 (uF). Gis mch c thit k i xng. Hy tm:
a. Cc dng in qua cc in trR1, R2.b. Cc in th ti cc nt B1, B2.
c. Nu bin p nh ng ra ca mi transistor l 8 (V), tnh cng sut trungbnh phn phi trn ti trong trng hp ny.
d. Cng sut trung bnh ca ngun cung cp cu c.
e. Hiu sut cu c.
f. Cng sut trung bnh cc i phn phi trn ti.
g. Nu Vi c gi tr 5 (Vrms), tnh cng sut trung bnh phn phi trn ti.
h. Tn s ct thp ca mch.
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2.2.1. Mch KCS m tn OTL (tt)
Bi gii:
a. V DC, cc transistor c phn cc in p B-E ln nn ta cth xem IB1, IB2
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2.2.1. Mch KCS m tn OTL (tt)
Bi gii: (tt)
d. Cng sut trung bnh ca ngun cung cp:
)(66.5)(
WRR
VV
IVIVP
Le
PCC
PCCSAVCCS
e. Hiu sut: %84.55S
L
P
P
f. Cng sut trung bnh trn ti cc i VPmax = VCC/2 = 10 (V)
)(94.4
8
1 22
max W
R
V
RR
RP
L
CC
Le
LL
g. Cng sut trung bnh trn ti nu Vi = 5 (Vrms) VL= 5 (Vrms)
h. Tn s ct thp: )(37.35)(2
1Hz
CRRf
oLe
C
Bi tp v nh: 2.22, 2.23
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2.2.2. KCS m tn OCL (tt)
IP1
-IP2
IP1
iT2
iT1
Vi
iL
t
t
t
t
iS t
T/2 T 3T/2 2T
IP2
IP1 IP2
dng ti khng mo
IP1 = IP2 = IP
Hot ng ca 2 transistor
phi i xng Q1Q2 (chntheo cp),R1 = R2, Re1 = Re2, VCC = VEE(ngun i i xng) in th tiim gia VM = 0.
Dng trung bnh ca nguncung cp:
P
T
PSAV
IwtdtI
TI
2sin
22/
0
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2.2.2. KCS m tn OCL (tt)
Cng sut trung bnh phn phi trn ti PL:
LPL
L
PLPLPLL RI
R
VIVP
22
2
1
2
1
2
1
Vi VPL, IPL l bin in p nh v bin dngnh ca ti. Gi s VP , IP l bin p v bin dngkhng mo ng ra ca cc transistor. Ta xt Q1 dn:
IP = IPL
Q1
VpL
Vp
+
-
Re
RL
+
-
Le
PPPL
P
Le
LPL
RR
VII
VRR
RV
L
P
Le
LL
R
V
RR
RP
22
2
1
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2.2.2. KCS m tn OCL (tt)
Cng sut trung bnh phn phi trn ti cc i khi: VP = Vpmax
Xt ng ti DCLL:
QAB 0
VCC
L
CC
Le
LL
R
V
RR
RP2
2
max2
1
Nu chn Re
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2.2.2. KCS m tn OCL (tt)
Cng sut trung bnh ca ngun cung cp PS:
PCCSAVCCS
IVIVP
2
Cng sut trung bnh cc i ca ngun cung cp PSmax
:
khi ti tiu th cng sut cc i PLmax.
maxmax
2max
PCCSS
IVPP
LP
Le
CC
Le
PPRR
V
RR
VI
maxmax
)(
2 2
maxmax
Le
CCSS
RR
VPP
LP
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2.2.2. KCS m tn OCL (tt)
Cng sut tiu tn ca mt transistor:
LSndissipatiodtntiuttC PPPPP )()(
CC
P
Le
L
eL
PCC
L
P
Le
L
S
L
V
V
RR
R
RR
VV
RV
RRR
P
P
42
21
22
Hiu sut cc i khi PLmax v PSmaxVPmax = VCC
B
Le
L
S
LAB
RR
R
P
P
4max
maxmax
Hiu sut:
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Mt s bi tpyucu
Bi 1: Hy chn transistor cng sut, in tr nnh nhit, ngun cung cp cho mch OTL mtknh c cng sut 16 (W), ti loa 8 (), hiu sutthit k 0.6.
Bi 2: Hy chn transistor cng sut, in tr nnh nhit, ngun cung cp cho mch OCL mt
knh c cng sut 20 (W), ti loa 8 (), hiu sutthit k 0.6.
Bi 3: Cc bi tp 2.19, 2.20, 2.21.
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2.3. Vn nng cng sut chomch KCST
Cng sut trung bnh phn phi trn ti PL:
LPLL
PL
PLPLLRI
R
VIVP
22
2
1
2
1
2
1
Nng bin dng qua ti.
Nng bin p trn ti mch ghp transistordng cu BTL (Bridge (Balanced) Transistor Line-out).
Nng bin dng v bin p trn ti.
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2.3. Vn nng cng sut chomch KCST (tt)
Nng bin dng qua ti:
Ghp transistor dng Darlington.
Ghp song song transistor: thng s dng trn thc t.
Q2
R1
R4
D3
R3
D2
Q4
+Vcc
RL
Q3
Ci
D1
Q1
Vi
-Vcc
R2
Q2R1
R4
R8
D3
R3
R9
D2
Q4
+Vcc
RL
Q3
Ci
R6
R10
D1
Q1
Vi
R5
R7
-Vcc
R2
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2.3. Vn nng cng sut chomch KCST (tt)
Nng bin in p trn ti BTL:
R1
R4
D3
R4
R1
R3R3
Q1
R2
D3
D2
+Vcc
RL
Q3
-Vi
Ci
D1
Q1
Q3
D1
Vi
D2
Ci
-Vcc
R2
Phi dng mch khuch m o.
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Q2R1
Q4
R4
R8
R6D3
R4
R1
R3R3
R9
Q1
R9
R2
D3
D2
R8
Q4
+Vcc
RL
R7
Q3
R10 -Vi
Ci
R6
R10
D1
Q1
Q3
D1
Vi
D2
R5
Ci
R7
-Vcc
R2
Q2
R5
2.3. Vn nng cng sut chomch KCST (tt)
Nng bin in p v bin dng ti:
Phi dng mch khuch m o.
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2.3. Vn nng cng sut chomch KCST (tt)
Mt sbi tp yu cu:
Bi 1: L lun vic tng cng sut trn ti cho cc dng mchnng cng sut bng phng php nng dng, nng p, nngdng v nng p.
Bi 2: Tm hiu nguyn l mch iu chnh m sc, mchequalizer.
Bi 3: Tm hiu s khi v mch nguyn l ca 1 ampli honchnh.
Q & A