www.德州仪器.com
500 ns/div
SW
10 v/div
输入 voltage
20 mv/div
DETAILEDDESCRIPTION
运作
开始-向上
短的-circuitprotection
TPS61060
TPS61061
TPS61062
SLVS538–NOVEMBER2004
INPUTVOLTAGERIPPLE
figure14.
thetps61060/61/62familyisaconstant-频率,pwmcurrent-modeconverterwithintegratedn-频道
mosfetswitchandsynchronousp-channelmosfetrectifier.thedeviceoperatesinpulsewidthmodulation
(pwm)withafixedswitchingfrequencyof1mhz.operationisunderstoodbestbyreferringtotheblock
图解.thedutycycleoftheconverterissetbytheerroramplifierandthesawtoothrampappliedtothe
比较器.becausethecontrolarchitectureisbasedonacurrent-modecontrol,acompensationrampisadded
toallowstableoperationfordutycycleslargerthan50%.theconverterisafullyintegratedsynchronousboost
converteroperatingalwaysincontinuousconductionmode.thisallowslownoiseoperationandavoidsringing
ontheswitchpinasitwouldbeseenonaconverterwhenenteringdiscontinuousconductionmode.
toavoidhighinrushcurrentduringstart-向上,specialcareistakentocontroltheinrushcurrent.whenthedevice
isfirstenabled,theoutputcapacitorischargedwithaconstantprechargecurrentoftypically100mauntilthe
outputvoltageistypically0.3vbelowvin.thethedevicestartswithareducedanalogcontrolledcurrentlimitfor
typically40µs.afterthistimeperiod,thedeviceentersitsnormalregulationwithfullcurrentlimit.thestart-向上
currentwaveformisshowninfigure11.thefixedprechargecurrentduringstart-upallowsthedevicetostartup
withoutproblemswhendrivingLEDsbecausetheLEDonlystartstoconductcurrentwhentheforwardvoltageis
reached.如果,foranyreasonaresistiveloadisdriven,themaximumstart-uploadcurrentneedstobesmaller,或者
equalto,theprechargecurrent.
thetps6106xfamilyhasanadvancedshort-circuitprotectionincasetheoutputofthedeviceisshortedto
地面.becausethedeviceisconfiguredasacurrentsourceevenwhentheledsareshorted,themaximum
currentiscontrolledbythesenseresistorrs.asanadditionalsafetyfeature,thetps6106xseriesalsoprotects
thedeviceandinductorwhentheoutputisshortedtoground.whentheoutputisshortedtoground,thedevice
entersprechargemodeandlimitsthemaximumcurrenttotypically100ma.
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