Chidziwitso cha driver wa LED
ndikukula kwachangu kwamakampani opanga zamagetsi zamagalimoto, tchipisi tating'onoting'ono ta LED zokhala ndi mitundu yosiyanasiyana yamagetsi amagetsi amagwiritsidwa ntchito kwambiri pakuwunikira kwamagalimoto, kuphatikiza kuyatsa kwakunja ndi kumbuyo, kuyatsa mkati ndikuwonetsanso kuyatsa.
Tchipisi zoyendetsa ma LED zitha kugawidwa kukhala dimming analog ndi PWM dimming molingana ndi njira ya dimming.Dimming ya analogi ndiyosavuta, Dimming ya PWM ndiyovuta, koma mizere yocheperako ndi yayikulu kuposa dimming ya analogi.Chip choyendetsa cha LED ngati kalasi ya kasamalidwe ka mphamvu, topology yake makamaka Buck ndi Boost.buck dera linanena bungwe panopa mosalekeza kuti linanena bungwe ripple panopa ndi ang'onoang'ono, amafuna ang'onoang'ono linanena bungwe capacitance, yabwino kwambiri kukwaniritsa mkulu mphamvu osalimba a dera.
Chithunzi 1 Kutulutsa Kwapano Kukulitsa vs Buck
Mitundu yodziwika bwino ya tchipisi ta driver wa LED ndi mawonekedwe apano (CM), COFT (controlled OFF-time) mode, COFT & PCM (peak current mode) mode.Poyerekeza ndi kuwongolera komwe kulipo pano, njira yowongolera ya COFT sikufuna kubwezeredwa kwa loop, yomwe imathandizira kuwongolera kachulukidwe kamagetsi, pomwe kuyankha mwachangu.
Mosiyana ndi njira zina zowongolera, chipangizo cha COFT chowongolera chili ndi pini ya COFF yosiyana ndi nthawi yopuma.Nkhaniyi ikuwonetsa masinthidwe ndi njira zodzitetezera kudera lakunja la COFF kutengera chip choyendetsa cha Buck LED choyendetsedwa ndi COFT.
Kukonzekera koyambirira kwa COFF ndi zodzitetezera
Mfundo yoyang'anira COFT mode ndikuti inductor ikafika pamlingo wapano, chubu chapamwamba chimazimitsa ndipo chubu chapansi chimayatsidwa.Nthawi yozimitsa ikafika tOFF, chubu chapamwamba chimayatsanso.Pambuyo pozimitsa chubu chapamwamba, imakhalabe yozimitsa nthawi zonse (tOFF).tOFF imayikidwa ndi capacitor (COFF) ndi voliyumu yotulutsa (Vo) pamphepete mwa dera.Izi zikuwonetsedwa mu Chithunzi 2. Chifukwa chakuti ILED imayendetsedwa mwamphamvu, Vo idzakhalabe pafupifupi nthawi zonse pamitundu yambiri yolowera ndi kutentha, zomwe zimapangitsa kuti pakhale tOFF yokhazikika, yomwe imatha kuwerengedwa pogwiritsa ntchito Vo.
Chithunzi 2. nthawi yoyendetsa dera ndi tOFF yowerengera
Tiyenera kuzindikira kuti pamene njira yosankhidwa ya dimming kapena dimming circuit imafuna kutulutsa kochepa, dera silingayambe bwino panthawiyi.Panthawi imeneyi, phokoso lamakono la inductor limakhala lalikulu, mphamvu yamagetsi imakhala yotsika kwambiri, yocheperapo kusiyana ndi magetsi.Kulephera uku kukuchitika, inductor yapano idzagwira ntchito ndi nthawi yayitali kwambiri.Nthawi zambiri nthawi yayitali yokhazikika mkati mwa chip imafika 200us ~ 300us.Panthawiyi mphamvu ya inductor yamakono ndi zotulutsa zimawoneka ngati zimalowa mumtundu wa hiccup ndipo sizingatuluke bwino.Chithunzi 3 chikuwonetsa mawonekedwe osadziwika bwino a inductor yapano ndi voliyumu yotulutsa ya TPS92515-Q1 pomwe shunt resistor imagwiritsidwa ntchito ponyamula.
Chithunzi 4 chikuwonetsa mitundu itatu ya mabwalo omwe angayambitse zolakwika pamwambapa.Pamene shunt FET ikugwiritsidwa ntchito kuziziritsa, shunt resistor imasankhidwa kuti ikhale yolemetsa, ndipo katunduyo ndi LED switching matrix circuit, onse amatha kufupikitsa magetsi otulutsa ndikuletsa kuyamba kwabwino.
Chithunzi 3 TPS92515-Q1 Inductor Panopa ndi Kutulutsa Voltage (Resistor Load Output Short Fault)
Chithunzi 4. Madera omwe angayambitse zazifupi zotulutsa
Kuti mupewe izi, ngakhale zotulukazo zikafupikitsidwa, magetsi owonjezera amafunikirabe kuti azilipiritsa COFF.Kupereka kofananira komwe VCC/VDD kungagwiritsidwe ntchito ngati kulipiritsa COFF capacitors, kumasunga nthawi yokhazikika, ndikusunga nthawi zonse.Makasitomala amatha kusungitsa chopinga cha ROFF2 pakati pa VCC/VDD ndi COFF popanga dera, monga momwe tawonetsera pa Chithunzi 5, kuti athandizire kukonza zolakwika pambuyo pake.Nthawi yomweyo, chiphaso cha TI chip nthawi zambiri chimapereka njira yowerengera ya ROFF2 molingana ndi dera lamkati la chip kuti zithandizire kusankha kwa kasitomala.
Chithunzi 5. SHUNT FET External ROFF2 Improvement Circuit
Kutenga vuto lachidule la TPS92515-Q1 mu Chithunzi 3 mwachitsanzo, njira yosinthidwa mu Chithunzi 5 imagwiritsidwa ntchito kuwonjezera ROFF2 pakati pa VCC ndi COFF kuti azilipira COFF.
Kusankha ROFF2 ndi njira ziwiri.Gawo loyamba ndikuwerengera nthawi yotsekera yofunikira (tOFF-Shunt) pomwe shunt resistor imagwiritsidwa ntchito potulutsa, pomwe VSHUNT ndimagetsi otulutsa pomwe shunt resistor imagwiritsidwa ntchito ponyamula.
Gawo lachiwiri ndikugwiritsa ntchito tOFF-Shunt kuti muwerengere ROFF2, yomwe ndi ndalama kuchokera ku VCC kupita ku COFF kudzera pa ROFF2, yowerengedwa motere.
Malingana ndi kuwerengera, sankhani mtengo woyenerera wa ROFF2 (50k Ohm) ndikugwirizanitsa ROFF2 pakati pa VCC ndi COFF pamlandu wolakwika mu Chithunzi 3, pamene kutuluka kwa dera kumakhala kozolowereka.Komanso dziwani kuti ROFF2 iyenera kukhala yaikulu kwambiri kuposa ROFF1;ngati ili yotsika kwambiri, TPS92515-Q1 idzakhala ndi zovuta zochepa zoyatsa nthawi, zomwe zingapangitse kuti pakhale kuwonongeka kwamakono komanso kuwonongeka kwa chipangizo cha chip.
Chithunzi 6. TPS92515-Q1 inductor yamakono ndi magetsi otulutsa (zachibadwa pambuyo powonjezera ROFF2)
Nthawi yotumiza: Feb-15-2022