LED DRIVE CIRCUITSWord文档格式.docx

LED DRIVE CIRCUITSWord文档格式.docx

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1）Lowdrivingvoltage（theavailablevoltageislowerthantheforwardvoltage）

Applications:

LEDflashlights,emergencylamps,energy-savinglamps.

Solutions:

BoostConverter（usinginductancetostoretheenergy）

Requirements:

lowcost,highefficiencyinconverting,smallvolume

2）Transitionaldrivingvoltage

Sometimestheavailablevoltagesupplyishigherthantheforwardvoltage,whilesometimeslower.

Application:

LEDminer'

slamp

reversepolaritychargepumpconverter

3）highdrivingvoltage

lawnlamp,headlights..

series-wound 

switchesbuckconverter

4）Commercialpowersupply

Voltagereduction,currentrectification,highchangingefficiency,lowcost,smallinsize.

<

1>

SmallandmediumpowerconsumingLEDs:

single-endfly-backconverter

HighPowerconsumingLEDs:

bridgecircuit

3.Typicaldrivingcircuits--drivers

i.Capacitor-basedbuckconverter

ii.UsingSCR

iii.Usingfilteringunit

iv.Mostsimplifyingwayofusingcapacitorstoreducethevoltage

1.Typicalvoltage-reducingdrivecircuitforLEDs

4.Typicalon-chipICsforuse

i.RGBLEDdriverSTP24DP05

LCDmonitors

TheSTP24DP05isamonolithic,lowvoltage,lowcurrentpower24-bitshiftregisterdesignedforLEDpanELdisplays.Thedevicecontainsa8x3-bitserial-in,parallel-outshiftregisterthatfeedsa8x3-bitD-typestorageregister.Intheoutputstage,twenty-fourregulatedcurrentsourcesweredesignedtoprovide5-80mAconstantcurrenttodrivetheLEDs.

ii.ChargepumpsfordrivingwhiteLEDs

iii.RunninganLEDwithpulsestogetmaximumbrightness

TogivemaximumbrightnessanLEDneedstobedrivenbyapulsecircuit.Inthisway,itispossibletoput0.5AmpcurrentpulsesthroughanLEDatafrequencyofaround100Hzwhichfoolstheeyeintothinkingthatitseesacontinuouslight.

IftheLEDisrunat0.5Ampsforverylong,itwillburnout（usuallywithinafractionofasecond）.Bykeepingthepulsedurationrelativelyshort,wecanavoidoverheatingtheLED.

Thiscircuitallowsadjustmentofthepulsewidthsothatthemaximumaveragecurrentisnomorethan50mA.

ToensurelongLEDlife,itshouldbeadjustedformaximumbrightnessthenreducedslightlytoanaveragecurrentofaround40mA.OneortwoLEDscanbedrivensimultaneously.C1canbearound1000uFandactsasareservoirbecausetheaveragebatteryisunabletosupplyhalfAmppulsesofcurrent.Thecircuitcanberunfromabatteryordcsupplyof9to12volts.

Wehadintendedtosupplyallthepartsasakitbutwe'

vehadonly2enquiriesintwoyears.However,youshouldbeabletoorderallthecomponentsfromMaplinElectronicsintheUK.

iv.LEDDriveCircuit（SM-CCP-20W）

LEDDriveCircuit（SM-CCP-20W）

ProductDescription

[SM-CCP-20W]isaconstantcurrentLEDdrivecircuitusingICmanufacturers,thecircuitissimpleandefficient.Nocapacitors,resistorsbuck.Smallheat,Circuitreliable,easytoEMItesting.Forsupportingtheuseofhigh-powerLED.Maximum22-1WLED.WidelyusedLEDlights,spotlights,lightscups,lamps,etc.

[SM-CCP-22W--usingsingle-sidedPCBdesign.Coatwithamoisturerole.

Technicalparameters

Automaticallyadaptinginputvoltagerange:

90-265VAC

Outputcurrent50-54-350mA+-15%（200336）

Rated:

20W

LEDvoltage:

10-60V

Efficiency:

80%

AutomaticadaptationofcolorLEDavoidalotofresistanceadjustment.

Compact:

Long-**width=76*43*32mm

Model:

SM-CCP-20W

Company:

XiangshanSolarmaxPhoto-ElectricCo.,Ltd

A.

ballastresistor

Otherconsiderations:

stabilityofcurrentandelectricalefficiency

“Voltage-coefficient”wayofcalculatingthepropertiesofthecircuit

Voltage-coefficient：

（3）

Stabilityofcurrent:

（％）（4）（假定

）；

Electricalefficiencyη=

（％）（5）;

Ballastresistor:

R=

（Ω）（6）；

Sourcevoltage:

U=

（V）（7）