Tsis-kev cais tawm kauj ruam-down LED tsav tsheb fais fab mov
Txoj kev tsav tsheb ntawm LED yog qhov sib txawv ntawm cov teeb halogen thiab cov teeb fluorescent. Nws yuav tsum muaj kev tsav tsheb tsis tu ncua, yog li yuav tsum muaj lub zog tsav tshwj xeeb. Raws li cov teeb pom kev dav dav, feem ntau ntawm lawv yog cov khoom siv hluav taws xob siab thiab SELV (muaj kev nyab xeeb ntxiv-tsis muaj hluav taws xob) tso tawm, yog li lawv feem ntau siv cov qauv qis. Buck topology muaj cov yam ntxwv ntawm cov qauv yooj yim, kev ua haujlwm siab, thiab me me ripple tam sim no. Nws yog feem ntau siv. . PT4207 yog LED tsav nti tsim raws li Buck topology.
PT4207 nti qauv yam ntxwv
PT4207 txais yuav ib qho kev tsim kho tshiab, uas tuaj yeem ua haujlwm tau zoo nyob rau hauv DC voltage ntawm 8V txog 450V tom qab AC cov tswv yim raug kho. Built-in 350mA / 20V MOSFET tuaj yeem muab 350mA LED tso zis tam sim no. Tsis tas li ntawd, nws yog txawm peem rau nrog ib tug sab nraud MOSFET hloov tsav chaw nres nkoj mus cuag lub LED tso zis tam sim no mus txog 1A thiab ua hauj lwm stably. Qhov kev ua haujlwm ntawm lub cev tuaj yeem ncav cuag 96%, thiab qhov tseeb ntawm LED tam sim no tuaj yeem ncav cuag ± 5% (nrog rau cov khoom siv hluav taws xob hloov pauv thiab cov khoom sib txawv). Los ntawm ntau qhov kev ua haujlwm dimming DIM tus pin, LED tam sim no tuaj yeem hloov kho tau yooj yim siv los yog DC voltage, lossis cov teeb liab mem tes siv tau los xaiv PWM dimming. Tsis tas li ntawd, lub nti kuj muaj qhov muag muag, luv luv thiab ua haujlwm kub dhau. Daim duab thaiv sab hauv ntawm PT4207 yog qhia raws li hauv daim duab 1.
Daim duab 1PT4207 Internal Structure Block Diagram
Kev ua haujlwm tsis tu ncua tam sim no: PT4207 siv lub sijhawm ua haujlwm ruaj khov los tswj cov zis tam sim no. Tom qab MOSFET sab hauv, cov tam sim no ntws los ntawm lub load, inductance, MOSFET thiab sampling resistor, thiab linearly nce nrog lub sij hawm, thiab ib tug voltage yog generated ntawm CS pin. Thaum qhov hluav taws xob nce mus txog tus nqi siv sab hauv, lub nti sab hauv tswj lub zog kom tua MOSFET thiab nkag mus rau lub voj voog tig. Lub sij hawm tig-tawm yog teem los ntawm ib tug sab nraud resistor thiab yog tsau. Tom qab qhov lapse, MOSFET tig dua thiab nkag mus rau lub voj voog ua haujlwm tom ntej. Txoj kev ntawm Buck qauv yog qhia hauv daim duab 2.
Daim duab 2 Ob daim ntawv ntawm Buck qauv
Thaum lub sij hawm MOSFET tig-tawm, lub zog nyob rau hauv inductor L yog tso rau hauv lub load LED los ntawm lub freewheeling diode D, thiab yog tsim rov qab, raws li qhia nyob rau hauv daim duab 3.
Daim duab 3 Buck qauv muab lub voj voog rov qab tam sim no
tuaj yeem tau txais los ntawm cov qauv inductance
Qhov twg VL yog qhov hluav taws xob hla lub inductor, L yog qhov inductance, Toff yog lub sijhawm teem tseg, thiab ΔIL yog tus nqi tam sim no hauv inductor.
Daim duab 4 Inductor tam sim no waveform nyob rau hauv CCM
Yog tias lub kaw lus ua haujlwm hauv CCM (kev ua haujlwm tsis tu ncua), qhov tam sim no waveform nyob rau hauv inductor yog qhia nyob rau hauv daim duab 4. Ntawm lawv, ILED yog LED niaj hnub tam sim no, IPEAK yog lub ncov tam sim no nyob rau hauv inductor, uas yog, lub ncov tam sim no. los ntawm MOSFET lossis freewheeling diode, thiab ILED=IPEAK-0.5ΔIL tau txais. Hloov cov qauv inductance kom tau txais
IPEAK tuaj yeem teeb tsa los ntawm kev coj tus cwj pwm resistor. Yog li ntawd, thaum lub tswv yim LED tso zis tau txiav txim siab, cov zis tam sim no tsis muaj dab tsi cuam tshuam nrog cov khoom siv hluav taws xob, yog li paub txog LED qhov tam sim no tswj.
Lub hauv paus ntsiab lus luv luv: Lub nti pom CS tus pin voltage hauv txhua lub voj voog tig. Thaum nws pom tias CS voltage nce ceev heev, lub nti yuav tua MOSFET thiab tig nws dua tom qab lub sijhawm ua tiav luv luv.
Over-temperature txoj cai: Lub nti muaj ib tug built-in overheating muaj nuj nqi. Thaum qhov kub ntawm qhov sib txuas ntawm lub nti siab tshaj 135 ° C, cov zis tam sim no yuav raug txiav kom txo tau qhov kub ntxiv. Yog tias qhov kub siab tshaj 150 ° C, cov zis tam sim no yuav poob mus rau 0, uas tuaj yeem zam teeb meem flickering thaum lub nti ua haujlwm. Yog tias koj xav tau kub dhau ntawm LED, koj tuaj yeem txuas ncaj qha rau qhov ntsuas kub tsis zoo coefficient thermistor ntawm DIM tus pin thiab GND tus pin. Thaum qhov kub thiab txias, qhov DIM voltage yuav poob, thiab tib lub sij hawm txo qis hauv CS tus pin siv hluav taws xob lossis txawm tias kaw, kom ua tiav Kev Ua Haujlwm Kub Kub.
Mos pib lub zog: Lub nti muaj lub sijhawm pib ua haujlwm 4ms, thiab tam sim no maj mam nce thaum pib, kom cov load tam sim no maj mam nce mus txog tus nqi teeb tsa, txo qhov pib surge tam sim no.
Daim duab 5PT4207 raug siv fais fab (tso zis: 24 txoj hlua ntawm LED array, 250mA) (luam tawm)
Daim duab 6 PT4207 raug siv hluav taws xob zoo thiab cov yam ntxwv tsis tu ncua tam sim no
Daim duab 7PT4207 siab tam sim no daim ntawv thov (tso tawm 12 txoj hlua ntawm LED array, 1000mA)
Daim duab 5 yog ib daim ntawv thov ntawm PT4207. Kev ua tau zoo thiab cov yam ntxwv tam sim no ntawm cov ntawv thov raug cai ntawm PT4207 tau pom hauv daim duab 6. Lwm cov qauv kev thov ntawm PT4207 tau pom hauv daim duab 7 thiab daim duab 8. Ntawm lawv, daim duab 7 yog daim ntawv thov siab tam sim no ntawm PT4207 (tso tawm 12 txoj hlua ntawm LED array, 1000mA); Daim duab 8 yog daim ntawv thov PT4207 DC tsawg voltage (tso tawm 1 3WLED, 700mA).
Daim duab 8PT4207 DC tsawg voltage daim ntawv thov (tso tawm 1 3WLED, 700mA)
Qhov system parameter tsim
Saib daim duab 5 rau cov ntawv thov raug. Kev txiav txim siab ntawm cov zis tam sim no: tuaj yeem ua raws li tus qauv
Xaiv qhov tsim nyog R4, R5, R6 thiab L. Rau kev suav cov kauj ruam tshwj xeeb, thov mus saib PT4207 cov ntaub ntawv.
Input capacitance xaiv: Lub input capacitance muab ib tug ruaj khov fais fab mov voltage rau lub system, uas yuav xaiv tau raws li qhov tso zis hwj chim thiab capacitance raws li 1-2uF / W. Kev siv teeb pom kev zoo yog txhua yam nyob rau hauv qhov kub thiab txias, yog li qhov ntsuas kub ntawm lub capacitor yog siab dua 105 ° C.
MOSFET xaiv: qhov ntws-qhov chaw tiv taus qhov hluav taws xob Vds raug xaiv raws li qhov xwm txheej tawm tswv yim, thiab cov dej ntws tam sim no yog 4 zaug lossis ntau dua ILED.
Output capacitor xaiv: Lub capacitor txuas nrog nyob rau hauv parallel nrog LED tuaj yeem nqus cov LED ripple tam sim no. Qhov zoo tshaj plaws, lub inductor ripple tam sim no yog absorbed tag nrho los ntawm cov zis capacitor, ncua lub neej ntawm LED mus rau ib qho twg. Feem ntau xaiv 1-10uF.
Freewheeling diode xaiv: Xaiv Schottky diode lossis ultra-ceev rov qab diode, lub sij hawm rov qab rov qab Trr yog tsawg dua 100ns, thiab lub peev xwm tam sim no yuav tsum ntau dua IPEAK.
LED fluorescent teeb lub plhaub inductance xaiv: I-shaped inductor lossis kaw sib nqus transformer inductor tuaj yeem xaiv. I-shaped inductors feem ntau tsis tshua muaj nqi thiab yooj yim hauv cov txheej txheem, tab sis lawv yog cov hlau nplaum, uas tuaj yeem yooj yim ua rau poob ntawm cov kab sib nqus hauv qhov chaw hlau thiab ua rau lub cev ua haujlwm tsis zoo, yog li lawv feem ntau siv hauv cov teeb tsis muaj. - hlau plhaub. Tsis muaj teeb meem dab tsi ntawm inductor siv, qhov saturation tam sim no ntawm inductor yuav tsum muaj ntau dua 1.2 npaug ntawm ILED, thiab Curie kub ntawm cov khoom siv hlau nplaum yog siab dua 150 ° C.
Layout tsim cov ntsiab lus
Saib daim duab 5 rau cov ntawv thov raug. Ntawm lawv, lim capacitors C3, C4, C5, thiab resistor R4 yuav tsum nyob ze li sai tau rau cov nti pins. Input capacitor C1, load, inductor L4, MOSFET, chip S pin, sampling resistors R5 thiab R6 yog txoj hauv kev loj tam sim no, cov xaim yuav tsum tuab thiab luv li sai tau, thiab thaj chaw kaw yuav tsum me me li sai tau. Sampling resistors R5 thiab R6 yog txuas nrog high-frequency thiab high-tam sim no av, uas yog cuam tshuam qhov chaw thiab yuav tsum tau txuas nrog rau qhov tsis zoo electrode ntawm input lim capacitor C1 los ntawm txoj kev luv. Qhov thib peb tus pin ntawm lub nti, nrog rau hauv av ntawm C3, C4, C5, thiab R4 xav tau ib qho chaw ruaj khov, uas tuaj yeem raug coj tawm ntawm C1.
