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