Thecircuitandfirmwaredescribedinthisapplication
notedemonstratesaminimalpartscountdriver/control-
lerforahigh-power(1Worgreater)LED.Thecircuitis
basedonabucktopologyswitchingpowersupply
usingtheon-chipcomparatorperipheralwithinthe
PIC12F675PIC
®
microcontroller.Theswitchingpower
supplydesignensuresefficientpowertransferbetween
thesystembatteryandtheoutputLED.
TheFlashPICmicrocontrollerisusedtoimplement
intensitycontrol,automatedintensitycompensationfor
lowbatteryconditions,andtheabilitytoplaybackpre-
programmedFlashsequences.TheFlashPICmicro-
controlleralsoallowsthecreationofacustomPC-
basedgraphicaluserinterface,usingthePICkit™1
FlashStarterKitforprogrammingthepre-programmed
Flashsequences.Thecombinationoftheswitching
powersupplydesignandthemicrocontrollerresultsin
anefficientcircuitwithadvancedautomatedfeatures
whilekeepingthecircuitsimpleandinexpensive.AN874BuckConfigurationHigh-PowerLEDDriverVoltageandCurrentAuthor:KeithCurtisMicrochipTechnologyInc.The1wattchosenmodulerequiresatypicaldriveof3.4Vat350mAtoproduceitsfulloutputbrightness.Themaximumcurrentdrivefortheunitis500mA.INTRODUCTIONExceedingthemaximumcurrentspecificationforthemodule,evenbyshortdurati
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