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HT7L5610 Datasheet(PDF) 5 Page - Holtek Semiconductor Inc |
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HT7L5610 Datasheet(HTML) 5 Page - Holtek Semiconductor Inc |
5 / 9 page Rev. 1.00 5 September 08, 2015 HT7L5610 Figure 9. Temperature vs. High AC Voltage Functional Description TheHT7L5610isasingle-stageprimary-sideoffline LEDcontrollerdesignedforisolatedLEDlighting applications.ThedevicecanachievehighPower FactorvaluesandlowTHDwithoutresortingto additionalexternalcircuitsandcanalsogeneratehigh accuracyLEDdrivecurrentswithveryfewexternal components. Start-up Current Averylowstart-upcurrent,ISTART,allowstheselection ofalargevaluestart-upresistorwhichreducespower dissipation. Power Factor Correction Highpowerfactorvaluesareachievedbyconstant on-timeoperation.Toimplementconstanton-time control,a0.47µFcapacitorisplacedbetweenthe COMPpinandground. Constant Current Control ThedeviceaccuratelyregulatestheLEDcurrent bysensingtheprimary-sideinformation.TheLED currentcanbeeasilysetusingthefollowingformula: S P CS FB OUT N N R V I × × ≈ 2 1 Where NPistheprimarywindingandNSisthe secondarywinding;VFB(=300mV)istheinternal voltagereferenceandRCSistheexternalcurrent sensingresistor. VCC Under Voltage Lockout – UVLO ThedeviceincludesaUVLOfeaturewhichhasabout 10Vofhysteresis.ThePWMcontrollerturnsonwhen VCCishigherthan18VandturnsoffwhenVCC islowerthan7.5V.Thehysteresischaracteristics guaranteethatthedevicecanbepoweredbyaninput capacitorduringstart-up.Whentheoutputvoltage increasestoacertainvalueafterstart-up,VCCwillbe chargedbyanoutputthroughanauxiliarywinding. Boundary Conduction Mode – BCM ThepowerMOSFETisturnedonbyinductorcurrent zero-crossingdetection.Thecurrentzero-crossing canbedetectedbyaZCDvoltage.Whentheinductor currentisatthezerocrossingpoint,thevoltage ontheZCDpinwilldroprapidly.TheHT7L5610 thendetectsthefallingedgeandturnsonthePower MOSFET.Theboundaryconductionmodeprovides lowturn-onswitchinglossesandhighconversion efficiency. LEB on CS – Leading-Edge Blanking EachtimetheinternalpowerMOSFETisswitched on,aturn-onspikewillinevitablyoccuratthesense resistor.Toavoidfaultytriggering,a400nsleading- edgeblanktimeisgenerated.Duringthisblanking period,thecurrent-limitcomparatorisdisabledand canthereforenotswitchoffthegatedriver. OVP on VCC – Over Voltage Protection InordertopreventPWMcontrollerdamage,the deviceincludesanOVPfunctiononVCC.Should theVCCvoltagebehigherthantheOVPthreshold voltage of 24V, the PWM controller will stop operating immediately.When theVCC voltage decreasesbelowtheUVLOofflevel,thecontroller willreset. |
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