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HT7L4815 データシート(PDF) 5 Page - Holtek Semiconductor Inc

部品番号 HT7L4815
部品情報  Non-isolation Buck LED Lighting Driver with Active PFC
PDF  9 Pages
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メーカー  HOLTEK [Holtek Semiconductor Inc]
ホームページ  http://www.holtek.com
Logo HOLTEK - Holtek Semiconductor Inc

HT7L4815 データシート(HTML) 5 Page - Holtek Semiconductor Inc

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Rev. 1.00
5
June 26, 2015
HT7L4815
Figure 9. Efficiency vs. High AC Voltage
Typical Application Circuit
CS
5
2
3
6
HT7L4815
4
1
7
8
CS
ZCD
VSS
COMP
VCC
DRAIN
DRAIN
90Vac~265Vac
LED+
LED-
Functional Description
TheHT7L4815isauniversalAC/DCLEDdriver
designedforLEDlightingapplications.Thedevice
can achieve high Power Factor values without
resortingtoadditionalcircuitsandcanalsogenerate
highaccuracyLEDdrivecurrentswithveryfew
externalcomponents.Separategroundsareprovided.
Oneisafloatinggroundforthedevicewhiletheother
istheearthterminal.Usersshouldbeawarethatthe
twogroundscannotbedirectlyconnectedtogetherto
avoidICdamageandsystemmalfunction.
Start-up Current
Averylowstart-upcurrent,ISTART,allowstheusersto
selectalargervalueofstart-upresistorwhichreduces
powerdissipation.
VCC Under Voltage Lockout – UVLO
ThedeviceincludesaUVLOfeaturewhichhas8V
hysteresis.ThePWMcontrollerturnsonwhenVCC
ishigherthan18VandturnsoffwhenVCCislower
than10V.Thehysteresischaracteristicsguarantee
thatthedevicecanbepoweredbyaninputcapacitor
duringstart-up.Whentheoutputvoltageincreasestoa
certainvalueafterstart-up,VCCwillbechargedbyan
outputthroughanauxiliarywindingoraZenerDiode.
VZ=VLED-VCC.
Boundary Conduction Mode – BCM
ThepowerMOSFETisturnedonbyinductorcurrent
zero-crossingdetection.Thecurrentzero-crossing
canbedetectedbyaZCDvoltage.Whentheinductor
currentisatthezerocrossingpoint,thevoltageonthe
ZCDpinwilldroprapidly.Thedevicethendetects
thefallingedgeandturnsontheinternalpower
MOSFET.Theboundaryconductionmodeprovides
forlowturn-onswitchinglossesandhighconversion
efficiency.
Zero Current Detection – ZCD
TheZCDvoltageisdesignedtooperatebetween0V
and3Vfornormaloperation.Ifthevoltageonthe
ZCDpingoeshigherthan1.5V,theZCDcomparator
waitsuntilthevoltagegoesbelow1V.Whenthe
inductorcurrentisatthezerocrossingpoint,the
voltageontheZCDpinwilldroprapidly.Thedevice
willthendetectthe1Vfallingedgeandturnonthe
PowerMOSFET.The0.5Vhysteresisavoidsanyfalse
triggeringactionsduetonoise.



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