TIUC1825PWM电源控制方案

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1、TlUC1825PWM电源控制方案作者：时间：2009-05-24来源：TI公司的UC1825是PWM控制器件，非常适合高频开关电源应用.UC1825的特别之处是通过比较器和逻辑电路最小化传输时延，同时最人化误差放大器的带宽和转换速率.UC1825的开关频率高达1MHz,50ns传输时延至输出，符合QML-V认证和SMD5962-87681以及Rad容差为30kRad(Si)TID.UC1825具有大电流双图腾柱输出，峰值电流1.5A,起动电流仅为1.1mA,逐个脉冲进行限流,软起动/最大占空比控制和带滞后的欠压锁住.本文介绍了UC1825的主妾特性，方框图

2、以及采用UC1835的50W设计案例。TheUC1825PWMcontroldeviceisoptimizedforhigh-frequencyswitchedmodepowersupplyapplications.Particularcarewasgiventominimizingpropagationdelaysthroughthecomparatorsandlogiccircuitrywhilemaximizingbandwidthandslewrateoftheerroramplifier.Thiscontrollerisdesignedforuse

3、ineithercurrent-modeorvoltagemodesystemswiththecapabilityforinputvoltagefeed-forward.Protectioncircuitryincludesacurrentlimitcomparatorwitha1-Vthreshold,aTTLcompatibleshutdownport,andasoftstartpinwhichwilldoubleasamaximumduty-cycleclamp・Thelogicisfullylatchedtoprovidejitter-freeope

4、rationandprohibitmultiplepulsesatanoutput.Anundervoltagelockoutsectionwith800mVofhysteresisassureslowstartupcurrent.Duringundervoltagelockout,theoutputsarehighimpedanee.Thisdevicefeaturestotempoleoutputsdesignedtosourceandsinkhighpeakcurrentsfromcapacitiveloads,suchasthegateofapowe

5、rMOSFET・Theonstateisdesignedasahighlevel.UC1825主要特性：QML-VQualified,SMD5962-87681Rad-Tolerant:30kRad(Si)TID(1)CompatibleWithVoltage-orCurrent-ModeTopologiesPracticalOperationSwitchingFrequenciesto1MHz50-nsPropagationDelay-to-OutputHigh-CurrentDualTotemPoleOutputs(1.5APeak)WideBandwi

6、dthErrorAmplifierFullyLatchedLogicWithDouble-PulseSuppressionPulse-by-PulseCurrentLimitingSoftStart/MaximumDuty-CycleControlUndervoltageLockoutWithHysteresisLowStart-UpCurrent(1.1mA)Oonomr*卄IOu?BF'A*rGNDJrrc-=s-=2W"BanSaW*EnorApVccEpGNDVr图1.UC1825方框图Q50UC182527k4OscillatorRampVcOut

7、A1310kQ10.1urF111a1033kuS8E/AOut、OutBNonINV>Error‘AmpPwrGndINV丿GndSoftStartliIMShutdownVref5.1V911-ox11020图2.UC1825开环实验室测试电路42V?o56VVootSV1Ato10A1513i0.1UFVccVREF2NlOutA[W1N5820-VA—VcIOutB11rl卫一-T丄-<4.3kllUC28J51nF们invlu^sordiij10kl212Q3.3kQIE/AOutRflmp74CLOCKCt65RtPwGnd1Jl.5kDGndS

8、SRo壬0.1nFUDG-iXJ2图3採用UC183