Gabatarwar guntu direban LED
tare da saurin ci gaba na masana'antar lantarki na kera motoci, manyan kwakwalwan direban LED masu girma tare da kewayon ƙarfin shigar da wutar lantarki ana amfani da su sosai a cikin hasken mota, gami da na waje da na baya, hasken ciki da nunin haske.
Ana iya raba kwakwalwan direban LED zuwa dimming analog da PWM dimming bisa ga hanyar dimming.Analog dimming yana da ɗan sauƙi mai sauƙi, PWM dimming yana da ɗan rikitarwa, amma kewayon dimming na layi ya fi na analog dimming.Guntuwar direban LED azaman nau'in guntu sarrafa wutar lantarki, topology ɗin sa galibi Buck da Boost.Buck circuit fitarwa halin yanzu ci gaba da cewa da fitarwa na yanzu ripple ne karami, bukatar karami fitarwa capacitance, mafi m don cimma babban iko yawa na kewaye.
Hoto 1 Fitar da Haɓaka na Yanzu vs Buck
Hanyoyin sarrafawa gama gari na kwakwalwan direban LED sune yanayin halin yanzu (CM), yanayin COFT (sarrafawa-lokacin kashewa), yanayin COFT & PCM (yanayin kololuwar halin yanzu).Idan aka kwatanta da sarrafa yanayin halin yanzu, yanayin kula da COFT baya buƙatar ramawar madauki, wanda ke da amfani don haɓaka ƙarfin ƙarfi, yayin da samun amsa mai ƙarfi da sauri.
Ba kamar sauran hanyoyin sarrafawa ba, guntuwar yanayin sarrafa COFT yana da keɓantaccen fil ɗin COFF don saitin lokacin kashewa.Wannan labarin yana gabatar da ƙayyadaddun tsari da kiyayewa don kewayen COFF na waje dangane da guntu direban Buck LED mai sarrafa COFT.
Tsarin asali na COFF da taka tsantsan
Ka'idar sarrafawa ta yanayin COFT ita ce lokacin da inductor na yanzu ya kai matakin saiti na yanzu, bututu na sama yana kashe kuma ƙananan bututu yana kunna.Lokacin da lokacin kashewa ya kai tOFF, bututu na sama yana sake kunnawa.Bayan bututu na sama ya kashe, zai kasance a kashe na dindindin na lokaci (tOFF).An saita tOFF ta capacitor (COFF) da ƙarfin fitarwa (Vo) a gefen kewaye.Ana nuna wannan a cikin Hoto 2. Saboda ILED yana da tsari sosai, Vo zai kasance kusan akai-akai akan nau'in nau'in ƙarfin shigarwa da yanayin zafi, yana haifar da kusan m tOFF, wanda za'a iya ƙididdige shi ta amfani da Vo.
Hoto 2. kashe da'irar sarrafa lokaci da dabarar lissafin tOFF
Ya kamata a lura cewa lokacin da zaɓin hanyar dimming ko da'irar dimming yana buƙatar gajeriyar fitarwa, da'irar ba za ta fara da kyau ba a wannan lokacin.A wannan lokacin, ripple ɗin inductor na yanzu ya zama babba, ƙarfin fitarwa ya zama ƙasa sosai, ƙasa da ƙarfin da aka saita.Lokacin da wannan gazawar ta faru, inductor na yanzu zai yi aiki tare da matsakaicin lokacin kashewa.Yawancin lokaci iyakar kashe lokacin da aka saita a cikin guntu ya kai 200us ~ 300us.A wannan lokacin inductor na halin yanzu da ƙarfin fitarwa kamar suna shiga yanayin ɓarna kuma ba zai iya fitowa kullum ba.Hoto na 3 yana nuna nau'in igiyar ruwa mara kyau na inductor na yanzu da ƙarfin fitarwa na TPS92515-Q1 lokacin da ake amfani da shunt resistor don kaya.
Hoto na 4 yana nuna nau'ikan da'irori guda uku waɗanda zasu iya haifar da kurakuran da ke sama.Lokacin da aka yi amfani da shunt FET don ragewa, ana zaɓar shunt resistor don ɗaukar nauyi, kuma nauyin shine madaidaicin matrix na LED, dukkansu na iya rage ƙarfin fitarwa kuma su hana farawa na yau da kullun.
Hoto 3 TPS92515-Q1 Inductor Na Yanzu da Fitar Wutar Lantarki (Gajeren Laifi Mai Saurin Fitowa Mai Tsaya)
Hoto 4. Wuraren da za su iya haifar da gajeren wando
Don guje wa wannan, ko da lokacin da aka gajarta abin fitarwa, ana buƙatar ƙarin ƙarfin lantarki don cajin COFF.Madaidaicin wadata wanda VCC/VDD za a iya amfani da shi azaman cajin capacitors COFF, yana kiyaye tsayayyen lokacin kashewa, kuma yana riƙe ripple akai-akai.Abokan ciniki za su iya yin tanadin resistor ROFF2 tsakanin VCC/VDD da COFF yayin zayyana da'ira, kamar yadda aka nuna a hoto na 5, don sauƙaƙe aikin cirewa daga baya.A lokaci guda, TI guntu datasheet yawanci yana ba da takamaiman tsarin lissafin ROFF2 bisa ga da'irar ciki na guntu don sauƙaƙe zaɓin abokin ciniki na resistor.
Hoto 5. SHUNT FET Wajen ROFF2 Ingantaccen Da'irar
Ɗaukar kuskuren fitarwa na gajeren kewayawa na TPS92515-Q1 a cikin Hoto 3 a matsayin misali, hanyar da aka gyara a cikin Hoto 5 ana amfani da ita don ƙara ROFF2 tsakanin VCC da COFF don cajin COFF.
Zaɓin ROFF2 tsari ne mai mataki biyu.Mataki na farko shine lissafin lokacin da ake buƙata na kashewa (tOFF-Shunt) lokacin da ake amfani da shunt resistor don fitarwa, inda VSHUNT shine ƙarfin fitarwa lokacin da ake amfani da shunt resistor don ɗaukar nauyi.
Mataki na biyu shine yin amfani da tOFF-Shunt wajen lissafta ROFF2, wato cajin daga VCC zuwa COFF ta ROFF2, a lissafta kamar haka.
Dangane da lissafin, zaɓi ƙimar ROFF2 da ta dace (50k Ohm) kuma haɗa ROFF2 tsakanin VCC da COFF a cikin shari'ar kuskure a cikin Hoto 3, lokacin da fitowar kewayawa ta zama al'ada.Hakanan lura cewa ROFF2 yakamata ya zama mafi girma fiye da ROFF1;idan ya yi ƙasa da ƙasa, TPS92515-Q1 zai fuskanci ƙananan matsalolin lokacin kunnawa, wanda zai haifar da ƙarar halin yanzu da kuma yiwuwar lalacewa ga na'urar guntu.
Hoto 6. TPS92515-Q1 inductor na yanzu da ƙarfin fitarwa (na al'ada bayan ƙara ROFF2)
Lokacin aikawa: Fabrairu-15-2022