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Flyback converter
Mc lc
Chng I: Gii thiu chung v mch bm xung 1 chiu ...................................3
1.1. Nguyn tc hot ng ..........................................................................3
1.2. Cc mch bm xung mt chiu ph bin([1]) ........................................4
1.2.1. Buck converter ..............................................................................4
1.2.2. Cc dng Buck Converter c cch ly bng bin p ..........................5
1.2.3. Boost Converter ............................................................................7
1.2.4. Buck-Boost Converter ...................................................................8
1.2.5. Flyback Converter .........................................................................9
1.3. Cc ch dng in ([2]) ...................................................................9
1.4. Cc nguyn l iu khin [1] ..............................................................11
1.5. Vn la chn dng mch bm xung([2],[3])....................................12
Chng II: Flyback Converter ......................................................................14
2.1.S nguyn l v hot ng: ............................................................14
2.1.1. Phn tch hot ng ca Flyback Converter ch CCM ...........14
2.1.2. Flyback Transformer. ..................................................................17
2.1.3. Phn tch hot ng ca Flyback Converter ch DCM ...........17
2.1.4. Cc gi tr bin gia CCM v DCM .............................................18
2.1.5. Cc yu t tn hao v mch m cho MOSFET ............................20
Chng III: Thit k thc t Flyback Converter.............................................23
3,1. Cc yu cu thit k: ..........................................................................23
3.2. Tnh ton thit k theo trnh t............................................................23
3.2.1. La chn ch dng: ................................................................23
3.2.2. Tnh ton thit k ch CCM .................................................24
Chng I: Gii thiu chung v mch bm xung 1 chiu
(DC-DC converter)
1.1. Nguyn tc hot ng
Mch bm xung mt chiu s dng cc linh kin in t cng sut c th iu
khin ng m hon ton to ra c in p c dng 1 chiu u ra nh
mun t mt in p 1 chiu u vo vi tn tht thp nht nh c tnh ging nh
cng tc ca cc linh kin ny : in tr khi ng bng khng v khi ngt bng v
cng. Nh , v mt l thuyt, tht thot nng lng bng khng.
Hnh 1.1: Nguyn tc hot ng ca DC-DC converter ( [1])
C th thy in p u ra ca mch bm xung c dng nhp nh, nhng nu s
dng cc linh kin c tn s ng ct ln cng vi mch lc ph hp th in p
u ra s c dng ng thng mc chp nhn c cho hu nh tt c cc ng
dng. Do tnh cht iu khin c v tn hao thp nn mch bm xung mt chiu
c s dng rt rng ri trong thc t.
1.2. Cc mch bm xung mt chiu ph bin([1])
1.2.1. Buck converter
Hnh 1.2: Buck converter
Buck converter hay cn gi l step-down converter l mch bm xung mt
chiu c bn nht, s dng mt cng tc bn dn mc ni tip bm xung in p
vo, a vo b lc LC trc khi ra ti. Diode c nhim v dn dng lin tc trong
cun cm L. in p u ra lun nh hn in p u vo.
Hm truyn ca Buck converter: Vout
Vin=D=
Ton
Ton+Toff=
Ton
T
Buck converter l nn tng c bn t thit k cc dng converter khc c
cch ly bng bin p.
1.2.2. Cc dng Buck Converter c cch ly bng bin p
Trn thc t, khi thit k cc b ngun 1 chiu, trong mch thng s dng
bin p cch ly nhm tng tnh an ton v tin cy. Trn c s Buck Converter,
c nhiu dng converter c ch to v ang c ng dng rt ph bin hin
nay. Di y s trnh by vn tt nguyn tc hot ng ca cc dng ny. C th
hn c th xem thm ti liu [2], [3] v [4].
1.2.2.1. Forward Converter
Hnh 1.3: Forward converter
Hnh 1.3 gii thiu mch nguyn l ca Forward Converter:
- Khi S ng, dng c dn qua cun s cp N1 v cm ng sang cun th
cp N2 ca my bin p. Diode D1 dn v D2 kha.
- Khi S kha, D1 b kha li v D2 dn, dng in ca L c dn lin tc
qua D2.
- Cun dy N3 v diode D3 c tc dng dn dng trong cun N1. T s N3/N1
phi c chn sao cho dng t ha v 0 trc khi S bt u chu k lm
vic tip theo.
Hm truyn ca Forward Converter:
Vout
Vin=
D
n=
D.N2
N1
1.2.2.2. Push-Pull converter
Hnh 1.4: Push-pull converter
Hnh 1.4 gii thiu mch nguyn l ca Push-pull Converter:
- Cc kha S1 v S2 hot ng trn 2 na chu k ngc nhau. S1 ng m
trn na chu k u v S2 ng m trn na chu k sau. Nguyn tc hot
ng v c bn ging vi Forward Converter
- Khi S1 ng, D1 dn. Khi S2 ng, D2 dn. Khi S2 v S1 cng kha, D1 v
D2 cng dn dng qua cun L.
Hm truyn ca Push-pull Converter:
VoutVin
=2D
n
1.2.2.3. Half-Bridge Converter
Hnh 1.5: Half-Bridge Converter
Hnh 1.5 gii thiu nguyn l hot ng ca Half-Bridge Converter:
- Hot ng ca hai kha S1 v S2 tng t nh Push-pull Converter. Cun
s cp ca my bin p khng c im trung tnh, nhng cc t mc theo
hnh na cu c nhim v tng t, a mt na in p vo cun s cp
trong mi khong thi gian lm vic ca S1 v S2
- Ch hot ng ca cc diode tng t nh Push-pull Converter
Hm truyn ca Half-Bridge Converter:
Vout
Vin=
D
n
1.2.2.4. Full-Bridge Converter
Hnh 1.6: Full-Bridge Converter
Hnh 1.6 gii thiu nguyn l hot ng ca Half-Bridge Converter:
- Mch s dng 4 kha trong S1, S4 hot ng ng thi v ngc vi cp
S2,S3. Hai cp kha ny hot ng xen k nhau trn 2 na chu k v mch
hot ng tng t nh Push-pull Converter.
- Ch hot ng ca cc diode tng t nh Push-pull Converter
Hm truyn ca Half-Bridge Converter:
VoutVin
=2D
n
1.2.3. Boost Converter
Hnh 1.7: Boost Converter
Boost Converter hay cn gi l Step-up Converter l mch bm xung 1 chiu c
bn c th a ra in p ln hn in p vo. Kha S c mc song song vi
in p vo. Khi S ng, nng lng c tch tr vo cun cm, ng thi diode
D kha. Khi S kha, D dn v nng lng ny c truyn n u ra.
Hm truyn ca Boost Converter :
VoutVin
=1
1 - D
Boost Converter khng c dng c bin p cch ly.
1.2.4. Buck-Boost Converter
Hnh 1.8: Buck-Boost Converter
Buck-Boost Converter kt hp kh nng ca Boost Converter v Buck
Converter khi c th to ra in p ra ln hn hoc b hn in p vo trong mt
khong cho php. Khi S ng, dng in np nng lng cho cun cm L, diode D
kha. Lc S kha, D dn dng t cun cm v t C cng phng in.
Hm truyn ca Buck-Boost Converter :
VoutVin
=
1 - D
Buck-Boost Converter c mt dng c bin p cch ly rt ph bin l Flyback
Converter
1.2.5. Flyback Converter
Flyback converter s c nghin cu k chng sau.
1.3. Cc ch dng in ([2])
Nh phn tch trn, trong tt c cc mch bm xung, lun xut hin mch
lc LC vi nhim v san bng in p ra. Tc dng ca RC c th c hiu theo
nguyn tc: chng np nng lng khi S ng v gii phng nng lng ny khi S
ngt nhm duy tr nng lng cho ti. Trong , cun cm L ng vai tr gi cho
dng khng i u ra c dng 1 chiu. Khi S ng , dng qua L khng tng t
ngt m tng dn theo hin tng cm ng in t v khi S kha, dng cng khng
gim t ngt m gim dn.
Trong thc t, c 3 ch dng c th xy ra cho cun cm:
- Ch dng lin tc (CCM-continuous conduction mode): IL tng t gi tr
Ivalley n gi tr Ipeak ri li gim xung Ivalley khi S kha. Do dng khng
bao gi v 0 nn ch ny c gi l ch dng lin tc.
- Ch dng gin on (DCM-discontinuous conduction mode): IL tng t 0
n Ipeak khi S ng v khi S kha, dng gim v 0 trc khi S ng li trong
chu k tip theo.
- Ch bin (BCM-boundary or borderline conduction mode hoc CRM-
critical conduction mode) : mch iu khin s iu chnh sao cho khi tht IL va gim v 0, S s ng np li cho L, tc l nng lng ca L s c
gii phng ht trc chu k tip theo.
Hnh 1.9: Ba ch dng qua cun cm
Nhng tnh ton c th cho thy rng vic la chn L s nh hng n ch
dng in qua n. C mt gi tr Lb xc nh ranh gii hai ch CCM v
DCM. Trng hp c th vi Flyback Converter s c xt chng sau.
1.4. Cc nguyn l iu khin [1]
Cc b bm xung phi a ra c in p mong mun trong iu kin ti hoc
in p u vo thay i. Nh bit, thay i in p u ra, cn thay i t s
lm vic D, tc l thay i khong thi gian ng m ca cng tc bn dn. T ,
c th thit lp mt mch vng kn iu khin nh hnh v:
Hnh 1.10: Nguyn tc iu khin in p
Trn hnh l nguyn tc iu khin c bn ca cc b bm xung 1 chiu,
nguyn tc iu khin in p. in p ra c o v v so snh vi in p t
mong mun. Sau sai lch c khuch i v a vo so snh vi xung rng
ca c tn s cng vi tn s ng ct ca S (nguyn l PWM), v a ra xung
ng m S. V mt nguyn tc, c th hiu mch hot ng nh sau: v d vi
Buck converter nu Vout cao hn mong mun th kha S, nh hn th m S, Vout s
dao ng lin tc quanh gi tr mong mun.
Nguyn tc iu khin in p c u im ln v s linh hot v n gin.
B iu khin s phn ng cc nhanh vi tt c nhng bin i ca ti. Tuy nhin
nu in p vo thay i th s rt lu b iu khin mi pht hin v phn ng vi
s thay i . C th nguyn tc iu khin dng in khc phc iu ny.
Hnh 1.10: Nguyn tc iu khin dng in
y, dng in qua cng tc hoc qua cun dy, c phn hi v di dng
tn hiu in p, v a v b so snh thay cho tn hiu xung rng ca. Trng thi
u vo ca b bm xung c phn nh qua tn hiu dng in ny, do b iu
khin theo nguyn tc dng in phn ng rt nhanh vi c thay i ca ti v thay
i u vo. Tuy nhin mt nhc im ln ca nguyn tc ny l s phc tp ca
n.
1.5. Vn la chn dng mch bm xung([2],[3])
Cc dng mch bm xung khc nhau c nhng u v nhc im khc nhau.
Ty thuc vo yu cu v in p vo, in p ra, cng sut thit k, gi thnh
m ngi thit k s chn ra dng mch ph hp cho mnh. Cc ti liu c a ra
cc bng sau tham kho:
Bng 1.1: La chn dng mch bm xung
Bng 1.2: u nhc im v phm vi ng dng tng dng mch
Chng II: Flyback Converter
Flyback Converter l mt trong nhng mch bm xung ph bin nht trn th
trng hin nay. N c nhng u im chnh nh n gin, gi thnh thp, an
ton, ph hp vi nhng ng dng dn dng c cng sut khng cao v khng yu
cu kht khe v p mch.
2.1.S nguyn l v hot ng:
Hnh 2.1: S c bn ca Flyback Converter
Flyback converter c pht trin t Buck-Boost Converter, vi thnh phn
cun cm tch ly nng lng c thay bng cun s cp ca my bin p. My
bin p c u ngc u nh hnh v. Diode D c ni vo sau cun th cp.
2.1.1. Phn tch hot ng ca Flyback Converter ch CCM
Khi phn tch, cc iu kin c coi l l tng. Cc yu t thc t s c xt
chng sau.
Khi S thng:
Khi kha S thng, dng in chy qua cun s cp my bin p. Cun cm
trong mch khng cho dng tng t ngt m tng dn t Ivalley n Ipeak theo t l
dI/dt = Vin/LP.Vi thi gian dn l ton, ta c:
pha th cp, do cc Anode ca D c ni vo u m ca cun th cp
(my bin p mc ngc) nn D kha, cun th cp khng c dng in. Ta c
mch tng ng nh hnh v:
Hnh 2.2: Mch tng ng khi S ng
Lc ny in p ra c duy tr nh nng lng tch tr trn t C t trc, do
in p phn cc ngc ca D:
Vi N =1/n = N2/N1
Khi S kha:
Khi S kha, m bo khng thay i dng t ngt trn cun s cp, in p
trn cun s cp ngay lp tc b o ngc, v trn cun th cp in p cng o
chiu, dn n vic D phn cc thun v ta c mch tng ng sau:
Hnh 2.3: Mch tng ng khi S thng
in p trn cun th cp lc ny bng in p ra Vout v cun s cp s cm
ng mt in pVr = Vout/N. Do ,in p ri trn cc D v cc S ca MOSFET
l:
Vr c gi l in p phn x, nhm ni n vic in p trn cun th cp
gy ra in p trn cun s cp. y cng l ngun gc ca ci tn Flyback
Converter.
in p trn cun s cp lm cho dng qua n gim theo t l dI/dt = -Vr/Lp.Do
ta c:
Kt hp hai phng trnh quan h Ivalley v Ipeak ta c:
y l hm truyn t ca Flyback Converter. N c dng tng t nh ca
Buck-Boost Converter nhng thm h s N. Vic iu chnh D s c th a ra
in p ra ln hoc b hn in p vo mt cch ty .
2.1.2. Flyback Transformer.
Bin p ca mch Flyback khng hot ng nh cc bin p thng thng. C
th thy cun s cp v cun th cp khng bao gi cng dn dng. S hin din
ca bin p y ch c ngha tch tr nng lng trn cun s cp v cch ly
input/output m thi. V vy, trong mt s chng trnh m phng, hoc d
hiu, ngi ta thng v bin p Flyback nh sau:
Hnh 2.4: Mch tng ng ca bin p Flyback
Trong s ny, bin p l tng thng thng c s dng v cun cm Lms
i din cho mt tch tr nng lng ca bin p.
Mt im cn ch khc l trong bin p Flyback ch hot ng trn 1 na ca
ng cong t ha B-H nn cn c khe h khng kh ln trnh bo ha t. iu
ny dn n th tch ca bin p s tng rt ln i vi cc mch c cng sut cao.
l mt hn ch ca Flyback Converter.
2.1.3. Phn tch hot ng ca Flyback Converter ch DCM
ch DCM, Flyback Converter hot ng vi nguyn tc tng t. Tuy
nhin, c 3 giai on trong qu trnh hot ng ch ny.
- Khi S dn, cc i lng trong mch bin thin tng t nh CCM, ch c
iu dng Ip tng t 0 cho n Ipeak.
- Giai on th 2 l t khi S kha cho n dng v 0, dng trong mch bin
thin vi cc phng trnh tng t nh ch CCM, ch c iu Ip gim
dn v 0.
- Giai on th 3 l giai on Ip=0 khi S kha, lc ny D cng kha v c
cun s cp ln th cp u khng c dng in.
Kt qu tnh ton a ra c biu thc hm truyn t sau:
Vi n = 1/N, RL l in tr ti. fs l tn s bm xung, Lms = Lp/n2 = Lm/n
2 l in
cm cun th cp.
C th thy t s truyn ca ch DCM ph thuc vo ti.
2.1.4.Cc gi tr bin gia CCM v DCM
C mt gi tr ca t s lm vic D xc nh bin gii gia hai trng thi. Gi tr
c tnh theo cng thc sau:
C th coi DB l hm ca VO v IO hoc RL v Lms. ch CCM, hm truyn
M khng ph thuc vo ti trong khi ch DCM, M ph thuc vo ti hoc
dng u ra. C th thy r hn hai th di y (cc th c v khi
khng tnh n tn hao):
Hnh 2.5 : th ph thuc ca D vo dng ti IO/(VO/2fs Lms )
i vi cc hm truyn c gi tr c nh
Hnh 2.6 : th ph thuc ca D vo in p ti RL/(2fs Lms )
i vi cc hm truyn c gi tr c nh
2.1.5.Cc yu t tn hao v mch m cho MOSFET
2.1.5.1. Cc i lng k sinh.
Trong mch bm xung mt chiu, cc i lng k sinh l khng th khng xt
n. Chng khng nhng gy ra tn hao m cn l nguyn nhn ca cc dao ng
k sinh, gy nhiu trong h thng v lm qu dng hoc qu p, nh hng n cc
thit b trong mch. Cc yu t ny bao gm:
- in cm k sinh trong cun s cp Lleak. in cm ny khng gy h cm
ln cun s cp m ch tch tr nng lng. Thng thng Lleak = (2-5)% Lm.
- T k sinh trn cun dy my bin p.
- T k sinh trn MOSFET
- in tr cun dy.
- T in trn cc diode.
C th tng hp cc yu t ny trn mch nh hnh v:
Hnh 2.7: Mch Flyback Converter c xt n cc yu t k sinh.
Mt cch ph bin gim tc ng ca cc yu t k sinh l s dng mch
m.
2.1.5.2.Mch m cho MOSFET
Mch m ph bin nht trong thc t l mch m RLD, bao gm mach RC
mc ni tip vi diode tn s cao nh hnh v:
Hnh 2.8: Mch m RLD
Chc nng ln nht ca mch m l cung cp mt con ng dng trong
cun s cp c th tip tc khp vng khi S chuyn t trng thi dn sang trng
thi kha, qua gim in p ngc trn MOSFET. Khi S kha, dng chy qua
Dclp n np cho t. V khi S dn, nng lng trn t gii phng qua Rclp.
Mt chc nng khc ca mch m l gim bt tc ng ca cc yu t k sinh,
c bit l Lleak v Cclump nh trong hnh 2.7.
Khi a mch m vo trong mch, cc yu t tnh ton s thay i, do lc
thit k cn tnh ton vi s mch c mch m. Khi thit k mch m, da
vo in p ngc cc i gia cc Drain v cc Source ca MOSFET VDSS
tnh ra in p ri trn RC, gi l Vclamp. Nhn trn s ta thy:
Vi: - kD l h s an ton, thng ly 0,85
- VOS l in p cc i ri trn Diode, thng ly 20V
- Vin l in p vo.
T s gia in p Vclamp v in p phn x trn cun s cp c gi l kc:
y c tnh n in p ri trn D khi D dn ( khong 0,7V)
kc thng c chn trong khong 1,3 cho n 1,5 t tnh ra N:
Tnh ton c th hn v Rclp v Cclp s c xt mc sau.
Chng III: Thit k thc t Flyback Converter
3,1. Cc yu cu thit k:
Cc thng s cn thit cho thit k:
- in p vo nh nht Vin,min = 24V
- in p vo ln nht Vin,max = 60V
- in p ra Vout = 12V
- Dng in ra Iout = 5A
Mt s thng s khc s c la chn khi thit k.
3.2. Tnh ton thit k theo trnh t.
3.2.1.La chn ch dng:
Nh ta bit trn, vic thay i D c th gip cho mch chuyn t ch
dng CCM sang DCM v ngc li. Tuy nhin, xc nh mt ch dng iu
chnh D trong ch s gip n gin hn cho vic tnh ton mch lc v mch
iu khin.
Hnh 3.1: th dng qua cun s cp ch CCM
Theo ti liu [2], DCM thch hp cho cc ng dng c cng sut khng qu
cao, c in p ra ln v dng nh cn CCM th ngc li (ta c th thy iu ny
qua th 2.5. bi ton ny, la chn CCM l hp l.
Hnh 3.1 th hin th dng qua LP ch CCM.
3.2.2. Tnh ton thit k ch CCM
Chn tn s bm xung:
Tn s bm xung c ly mc 20KHz
Tnh dng vo Iin:
Dng trung bnh u vo:
,
,
2,94 ( )outin avgin min
PI A
V
Vi l hiu sut ca mch, y ly 0,85
V Pout= Vout.Iout = 12.5 = 60(W)
Dng vo trung bnh y ly theo gi tr cc i c th xy ra.
Chn in p Vclamp
in p cc i gia cc Drain v cc Source ca MOSFET c chn ln
m bo an ton. y ta la chn VDSS = 150V. T ta tnh ra Vclamp:
Vclamp = kd.VDSS Vin,max - VOS = 150 0,85 60 20 = 47,5 (V)
Tnh h s my bin p 1/N
Chn kc = 1,5. Ta c:
( ) 1,5(12 0,7)0,401
47,5
c out f
clamp
k V VN
V
Chn N = 0,4.
Tnh Dmax
Dmax c tnh t cng thc hm truyn t, ng vi Vin, min:
,120,56
12 0,4 24
outmax
out in min
VD
V NV
IL, avg l dng trung bnh qua cun s cp:
,
,
2,945,25( )
0,56
in avg
L avg
max
II A
D
Tnh Lp
Lp c tnh ton theo nguyn tc sau: ta chn mt t l thay i dng in hp
l t Ipeak n Ivallley v t tnh ra L:
IL, avg l dng trung bnh qua cun s cp:
,
,
2,945,25( )
0,56
in avg
L avg
max
II A
D
Ir thay i t 02, khi Ir = 2, mch hot ng trng thi bin.Chn Ir = 0,8,
suy ra IL = 4.2A v ta tnh c L theo cng thc sau:
Cng thc trn c thit lp khi ng nht 2 phng trnh tnh Ipeak theo Ivalley.
l hiu sut ca ton b mch, = 0,85 nh ni trn
Thay s vo ta c:
2 20,85 24 31,75181( )
0,8 20000 60 24 31,75 24 31,75 0,85L H
Chn MOSFET
tnh chn MOSFET, ta tnh dng qua cun s cp my bin p, theo cng
thc sau:
Dng in cc i ,4,2
5,25 7,35( )2 2
Lpeak L avg
II I A
Rt ra 2
2
,
4,20,56 7,35 7,35 4,2 4,03( )
3L rmsI A
Nh vy cn chn MOSFET cn loi N-MOSFET c in p 150V dng
4,03A.
Chn mch m:
Mch m c chn theo cc cng thc sau:
Lleak c tnh theo LP theo cng thc Lleak = 0,02 Lp = 3,62( H )
V l in p sai lch cho php ca Vclamp : V = 0,1 Vclamp = 47,5 5V
Rt ra:
22 6 2
1,5 1 2 1,5 12,7144( )
0,4 20000 3,62 10 7,62clpR
1,5 12,73,3( )
0,4 144 20000 5clpC F
Lu la chn Rclp l in tr cng sut do ton b nng lng np cho t
c gii phng trn in tr.Nng lng vo khong
Tnh ra
6 2 1,50,5 20000 3,62 10 7,35 6(W)1,5 1clp
RP
Chn Diode pha th cp:
in p ngc ln nht trn D:
0,4 60 12 36( )in outPIV NV V V
Chn t lc u ra:
Ty vo c tnh ca ti m nhp nh ca in p s khc nhau. Tuy nhin,
mt t c vi mF c th a ra c in p phng.
Mt khc, mt in tr k sinh trn t c th gy ra in p chnh lch kh ln,
v th cn xem xt n iu khin v in tr k sinh:
Vi Vripple l in p nhp nh mong mun
Isec,peak l dng cc i trn cun th cp
sec,
7,3518,4( )
0,4
peak
peak
II A
N
3.3. Thit k mch
Cu chDC
Kh
i d
rive
r(IR
21
10
)C
hip
n
p
12
V7
80
5
12
V
30
F1
01
0PWM
Ph
n
h
i d
n
g
(AC
S7
15
)
I in
I out
U p
hI
T
i
R phn pRsense
Kh
i p
h
n h
i
p
(AD
73
6)
U p
hU
VC
C
VC
CV
CC
VC
C
RS
23
2
4N
35
Hnh 3.2: S cc khi c bn ca mch
3.3.1. Khi ngun
Khi ngun c nhim v cung cp ngun cho vi x l v driver. Thng cc
mch trong thc t, ngun cp ny c ly t chnh Vout (thi gian u ngi ta
dng mt c ch gi l start-up voltage ly ngun t Vin, sau trch p t Vout
iu khin mch).
y, ta s dng hai mch n p l mch n p 12V v mch n p 5V ni tip
to ra ngun 12V ng m MOSFET v ngun 5V cho cc chip trn mch.
3.3.2. MOSFET v driver
Sau khi tham kho cc ngun cung cp MOSFET v Driver trn th trng, ta
la chn MOSFET v driver nh sau:
MOSFET dng loi IRF630 (VDSS =200V, Imax = 9A).
Driver dng loi IR2103. y l loi chuyn dng ng m MOSFET 2
knh dng trong iu khin ng c nhng cng c th s dng knh low ca n
ng m MOSFET trong mch:
Hnh 3.3: S cc chn v s mch cn bn
Hnh 3.4: Nguyn l hot ng IR2103
T s nguyn l ta thy, ta nu ch s dng cc chn LIN, VCC, LO, COM,
ta vn c th iu khin ng m N-MOSFET trong mch Flyback Converter
theo s sau
Hnh 3.5: Dng IR2103 iu khin IRF630
Ta nhn thy rng in p logic vo LIN, in p ngun VCC v in p ra LO
cng mt mc, cng l mc ng m MOSFET, m y ta chn l 12V. Tuy
nhin in p ra ca vi x l vo khong 5V nn ta cn s dng mch 4N35
thay i mc in p a vo. 4N35 y khng thc s c chc nng cch ly m
ch chuyn i mc in p do chn t c ni chung.
Hnh 3.6 : Mch dng 4N35 thay i mc in p
3.3.3. Khi phn hi dng
Dng in c o t pha s cp ca mch s dng cm bin dng ACS715.
ACS715 l cm bin dng s dng hiu ng Hall, c mch chc nng nh hnh:
Hnh 3.7: S chn v cch mc thng dng ca ACS715
Vi s mc nh hnh v, ta c cng thc in p ra ca cm bin:
ax
ccout in
m
VV I
I
Imax l gi tr cc i ca dng in, ph thuc vo loi ACS715
3.3.4. Khi o p
in p ra ca mch c a qua tr phn p v a v cm bin in p
AD736. AD736 l cm bin in p c tc dng a ra in p t l thun vi in
p vo vi t l chnh xc cao v nhiu thp. Mch c bn dng AD736 nh hnh
di y:
Hnh 3.8: Khi phn hi p