Báo Cáo Ứng Dụng TL494 Thiết Kế Mạch DC DC Buck Converter - Tài Liệu, eBook, Giáo Trình

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Báo Cáo Ứng Dụng TL494 Thiết Kế Mạch DC DC Buck Converter - Tài Liệu, eBook, Giáo Trình

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LI NI U0CHNG L GII THIU CNG NGH1IC TL494 V MACH DC DC BUCK CONVERTER11.1. Tm hiu v ICTL494.11.2. MachDC DC Buck Converter.5CHNG 2.TNH TON MACH LC82.1. Mosfet IRF3205.82.2. Cun cm EE25102.3. Tu102.4. ot122.5. in tr13CHNG 3.TNH TON MACH IU KHIN153.1. ICTL494. 153.2. IR 2103.163.3. Tn s lm vic ca IC TL494. 183.4. H s khuch ai 193.5. TIT)h s phn p trong mach 203.6. ChonRp in p u ra l 5 vn20CHNG 4.KT QU THC NGHIM224.1.S i dv.224.2. kt qu thc nghim. 234.3 . Phn mach in25KT LUN26Ti Nu tham kho :27LI NI UNgy nay , trong nn cng nghip ha ,hin i ha gip cho con ngi tit kim c thi gian v s lao ng . ng thi to iu kin tt nc ta thc y qu trnh hi nhp nn kinh t th gii , bt kp s pht trin v khoa hc k thut cc nc pht trin ng dng vo sn xut.e c th bt kp s pht trin khoa hc cng ngh ng dng vo trong nn sn xut hng ha ti Vit Nam th ngnh t ng ha phi thc s n lc , ci tin mnh m cc cng ngh sn xut tin tin , hin i trn th gii .Hn th ngnh gio dc cng phi n lc y mnh cc chng trnh o to k s ngnh t ng ha p ng c vic cung cp nhn lc trong cc ngnh cng nghip trong nc ,trc tip tham gia vic thit k ch to v iu khin my mc thit b . iu ny i hi ngnh giao dc phi o to v cung cp mt i ng chuyn gia , k s c trnh v c kinh nghim cao cho cc ngnh cng nghip .L mt sinh vin ngnh t ng ha , em cm thy rt t ho khi c hc tp v nghin cu cc b mn trong ngnh t ng ha . Vic kt hp hc tp l thuyt trn lp v thc hnh ti cc xng em cm thy rt hu ch .V c bit l trong t thc tp cui kha ny chng em c c hi kim nghim tnh ng n v ng dng nhng kin thc l thuyt c hc .e ti thc tp cui kha ca chng em l ng dng TL494 thit k mch DC DC Buck converter vi 3 ni dung chnh : Tm hiu cng ngh :IC TL494 v mch dc dc Buck Converter. Tnh ton mch lc. Tnh ton mch iu khin.Em xin chn thnh cm n thy gio Nguyn Duy nh quan tm v hng dn , gip nhm 22 lp C TH 3 - K52 tn ty, nhit tnh .Em xin chn thnh cm n !

CHNG 1. GII THIU CNG NGH IC TL494 V MCH DC DC BUCK CONVERTER1.1. Tm hiu v IC TL494.a-Gii thiu v IC TL49416nnnnnnnn TL494xD16^so-16D SUFFIX CASE 751 B

oAWLYWWuuuuuuuu116nnnnnnnnPDIP-16 N SUFFIX CASE 648

TL494XNoAWLYYWWuuuuuuuu1Hnh 1.1 : ICTL494 IC TL494 l mt trong nhng IC c s dng nhiu trong cc mch ngun.

Hnh 1.2 s chn IC TL494 Nhim v ca cc chn: chn1,2 nhn in phi tip v t' ngiu khin inpra chn3 u ra ca mch so snh ,c thlytnhiubosc P,G t chnny. chn 4 chn lch iu khin hin IC h/ hay khng ,khi chn 4 =0v th IC hot ng,nu chn 4>0v th IC kho chn 5,6 hai chn ca mch dao ng chn7,9,10 ni t chn8 chn dao ng ra chn11 chn dao ng ra chn12 ngun Vcc 12v chn13 c ni vi p chun 5v chn14 t IC i ra in p chun 5v chn15,16 nhn in p hi tip Nguyn tc hot ngTL 494 l IC c nh tn s xung iu bin rng iu khin mch .s iu bin ca xung u ra dc thc hin bng cch so snh cc dng sng rng ca to ra bi cc bin dng in v thi giant in cho 1 trong 2 tn hiu iu khin .Ti ng ra c kch hot trong khi in p rng ca ln hn cc tn hiu /p. Khi tn hiu iu khin tng trong khi u vo ca rng ca l gim ln hn do dung lng gim theo t/gian.Mt xung li Flip-Flop lun phin ch o cho 2 linh kin l 2 transistor NPN.

"1TU l ir~LTLT ru-Control SignalCc tn hiu iu khin c bt ngun t 2 ngun : B so mu iu khin thi gian tt v cc mch iu khin sai lch khuych i.k tn hiu tt dn l dc so snh trc tip bi b kim sot t.g tt.So snh ny vi 1 in pc nh l 100 mV.iu ny to ra 1 khong thi gian tt l 3% l thi giantt ti thiu c th PWM so snh tn hiu iu khin dc to ra bi cc b sai lch khuch i, 1 chc nng ca b khuch i li l theo di in p u vo ca n trong 1 tn hiu iu khin ca bin cung cp 100%.ch kim sot .Cc b khuch i c th c s dng theo di dng in v dng cung cp hin i np. ng dng ca TL494Mt s ng dng ca TL494 hin nay :1. Dng np cho ngun iu chnh 5 V2. ng b haTL494 c th d dng ng b ha hai hay nhiu ngun dao ng trong h thng.3. ng b ha dao ng ca TL494 vi mt ngun xung khce ng b ha cc TL494 mt ng h bn ngoi, cc b dao ng ni b c th c s dng nh mt rng ca, xung in.4. Fail-Safe operation - gi an ton: bo v Current Limiting - Hn dng bo v b dao ng bn trong, chng ta dng thm in tr RT v t CT, RT hn dng (dn dng xung mass khi h thng bn ngoi b ngn mch), cn RT lm t x in p nhanh hn trong trng hp b dao ng bn trong ngng, gim nhiu tn hiu dao ng.

5. CurrentLimitin : Hn dngTL494 thng c dng hn cc dng in ngc hoc dng hn dng ti. V thng c ng dng trong cc iu khin DC.C hai b khuch i c mt ch cho php trc tip cm bin dng ti in p u ra. Mt s k thut c th c s dng hn dng.6. Fold-Back Current Limiting - Hn dng in ngc7. Pulse-Current Limiting: Hn dng xungCc kin trc ni b ca TL494 khng ph hp trc tip hn ch dng xung.Vn pht sinh t hai yu t:Cc b khuch i bn trong khng c chc nng nh mt cht, ch yu dnh cho cc ng dng tng t.Xung li flip flop qu nhy vi tn hiu tch cc ca cc b so snh PWM nh kch hot mt v chuyn kt qu u ra ca n sm, tc l, trc khi hon thnh giai on dao ng.Khi xung kt thc, cc tn hiu iu khin u ra li c kch hot v cc xung vo thi gian cn st li xut hin trn u ra ngc li.8. Cc ng dng ca Tt-Thi gian iu khin :Chc nng chnh ca iu khin thi gian tt l kim sot ti thiu thi gian cung cp dng ca TL494. iu khin thi gian tt cung cp dng iu khin t 5% n 100% thi gian tt.d-Nhim v ca TL494 trong mch DC DC Buck converter :-TL494 trong mch nhn tn hiu phn hi t in p u ra a v chn 1, tn hiu ti chn 1 c so snh vi tn hiu chun ti chn s 2 qua b khuch i thut ton. Da trn s sai lch gia hai tn hiu iu bin rng ca xung ng ct IRF3205.1.2. Mch DC DC Buck Converter.S nguyn l mch in DC-DC BUCK CONVERTER :

Hnh 1.2.1 ,Thnh phn ca mch TL494IR2103 EE 25 RZA IRF3205 IN 41481.2.1. Gii thiu v mch DC DC Buck Converter : L mch ngun xung hin nay ang c dng rt ph bin bi n c un im l hiu sut bin i nng lng cao v kh nng thay i linh hot trong thit k.Chng hn nh c th c nhiu u ra (output Voltage) vi nhiu cc khc nhau t mt u vo n(single Input voltage)...1.2.2. Cu to v nhim v ca ton mch :1. Cu to ca mch Mch in gm c hai phn :+ Cc phn t cng sut + Phn mch iu khin2. Nhim v chnh :+ Bin i ngun in p mt chiu 12V-1A ca Adapter thnh ngun in p 5V-2A u ra.+ n nh dng.+ n nh in p ra.1.2.3. Nguyn l hot ng ca mch : in p u ra c a v chn 1 ca IC TL494 lm tn hiu phn hi ti y tn hiu phn hi c so snh vi tn hiu chun v da vo s sai lch ca hai tn hiu ny iu ch xung iu khin vic ng ct IRF3205. Neu Vout < 5v th TL494 iu ch xung lm cho IRF3205 m rng ra x p n u ra. Neu Vout = 5v th TL494 iu ch xung lm cho IRF3205 kha li gim p n u ra. Tn hiu iu khin t TL494 a vo IR2103 c kch p iu khin vic ng ct IRF3205. Mch Boostrap c nhim v thc hin vic kch p .CHNG 2.TNH TON MCH Lc2.1. Mosfet IRF3205. IRF3205 l mt Mosfet knh N hay Mosfet ngc. Mosfet l Transistor hiu ng trng (Metal Oxide Semiconductor Field Effect Transistor) l mt Transistor c bit c cu to v hot ng khc vi Transistor thng thng m ta bit. Mosfet thng c cng sut ln hn rt nhiu so vi BJT. i vi tn hiu 1 chiu th n coi nh l 1 kha ng m. Mosfet c nguyn tc hot ng da trn hiu ng t' trng to ra dng in, l linh kin c tr khng u vo ln thch hp cho khuych i cc ngun tn hiu yu. Cu to ca Mosfet : Mosfet c cu trc bn dn cho php iu khin bng in p vi dng in iu khin cc nh.

Pint GateIRF3205

Pin2Drain Pin3SourceHnh 2.1 -IRF 3205 G : Gate gi l cc cng D : Drain gi l cc mng s : Source gi l cc ngun Trong : G l cc iu khin c cch l hon ton vi cu trc bn dn cn li bi lp in mi cc mng nhng c cch in cc ln dioxit-silic (Sio2). Hai cc cn li l cc gc (S) v cc mng (D). Cc mng l cc n cc ht mang in. Mosfet c in tr gia cc G vi cc s v gia cc G vi cc D l v cngln,cn in tr gia cc D v cc s ph thuc vo in p chnh lch gia cc G vccS(UGS). Khi in p UGS = 0 th in tr RDS rt ln, khi in p UGS > 0 => do hiu ng t' trng lm cho in tr RDS gim, in p UGS cng ln th in tr RDS cng nh.2.1.1. Nguyn l hot ng ca Mosfet :

Hnh 2.5 - S mch in th nghim cho mosfet Cp ngun mt chiu Ud qua mt bng n LED vo hai cc D v s ca Mosfet Q1 (Phn cc thun cho Mosfet ngc) ta thy bng n khng sng ngha l khng c dng in i qua cc DS khi chn G khng c cp in. Khi cng tc K ng, ngun Ug cp vo hai cc GS lm in p UGS > ov => n Q1 dn => bng n D sng. Khi cng tc K ngt, Ngun cp vo hai cc GS = ov nn => Q1 kha =>Bng n tt.=> T thc nghim trn ta thy rng : in p t vo chn G khng to ra dng GS nh trong Transistor thng thng ( V MOSFET l linh kin c tr khng u vo ln nn dng qua GS rt nh) m in p ny ch to ra t trng => lm cho in tr RDS gim xung.2.1.2. Cc thng s th hin kh nng ng ct ca Mosfet. Thi gian tr khi ng/m kha ph thuc gi tr cc t k sinh Cgs,Cgd,Cds. Tuy nhin cc thng s ny thng c cho di dng tr s t Ciss, Crss,Coss. Nhng di iu kin nht inh nh l in p gs v Uds. Ta c th tnh c gi tr cc t . Thng thng th chn ca Mosfet c quy nh chung khng nh Transitor. Chn ca Mosfet c quy nh: chn G bn tri, chn s bn phi cn chn D gia.LED

Trong s mch ny IRF3205 ng vai tr nh mt kha in t, n ng m lin tc vi tn s ln di s iu khin ca in p ti cc G to ra chui xung chum qua cc s.2.2. Cun cm EE25 Cun cm gm mt s vng dy qun li thnh nhiu vng, dy qun c sn emay cch in, li cun dy c th l khng kh, hoc l vt liu dn t nh Ferrite hay li thp k thut

Hnh 2.1: Cu to ca cun cm EE25 Gng dn t c lm bng li ferit, hnh ch E Cun cm EE25 c chc nng n nh dng in qua ti.2.3.T2.2.1. T phn cc

Hnh 2.3.1-T in c cu to t hai l kim loi ghp song song nhau, gia l cht in mi v c ni ra hai cc. T in l linh kin dng cha in tch. Mt t in l tng c in tch bn cc t l thun vi hiu in th t trn n theo cng thc:(2-1) Q = CxU [culng] Ngi ta thng ly tn ca t l tn ca cht din mi. Nh:T gm: Cht in mi l gm T giy: Cht in mi l giy Hai t phn cc 100uF-25V dng n nh in p trc v sau khi bin i.L^^LkAAk lil 11 Hnh 2.3.2 :T ha b, T khng phn cc

Hnh 2.3.3 : hnh dng v k hiu ca T khng phn ccCc loi t nh thng khng phn cc. Cc loi t ny thng chu c cc in p cao m thng thng l khong 50V hay 250V. Cc loi t khng phn cc ny c rt nhiu loi v c rt nhiu cc h thng chun c gi tr khc nhau.Trong s mch buck ta dng 2 t khng phn cc c ghi tr s l 102 v 105 .Cch c

Hnh 2.3.4 T k hiu 102 c= 10xl2/^= 1000pF = 1 nF. Vi t c tr s 105 c= lxl5p^= 1.000.000 pF= lOOOtfF.2.4. iot2.4.1. it xung RU2A Trong cc b ngun xung th u ra ca bin p xung , ta phi dng Diode xung chnh lun. Diode xung l Diode lm vic tn s cao khong vi chc KHz , Diode nn in thng thng khng th thay th vo v tr Diode xung c, nhng ngc li Diode xung c th thay th cho v tr Diode thng, Diode xung c gi thnh cao hn Diode thng nhiu ln. v c im hnh dng th Diode xung khng c g khc bit vi Diode thng, tuy nhin Diode xung thng c vng nh du t nt hoc nh du bng hai vng.Ktot(K)

A not (A)Hnh 2.4.1 : K hiu Diode xung R2A trong mch c nhim v khp mch cung cp dng qua ti khi m IRF3205 ct. V IRF3205 ng ct vi tn s cao nn chng ta phi chn Diode xung m bo nhim v khp mch nhiu ln m khng b hng.2.4.2,Led Diode pht phang l Diode pht ra nh sng khi c phn cc thun, in p lm vic ca LED khong 1,7 => 2,2V dng qua Led khong t 5mA n 20mA

3p 'vX %Hnh 2.5.2: n led v k hiu trong mch in tr 330 Q ni tipvi LED hn ch dng qua LED. Led c s dng trongmch DC DC Buck Converter botrngthic in2.5. in tr in tr l phn t' cchc nng ngn cn dng in trong mch. Mc ngncn dng in c c trung bi tr s in tr R. n v o: mQ, n, k2, MQJ=ED

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