标签: off-line

离线式电源的功率因素校正(PFC)目的在于减少输入电流和满足未来稳压的需要。桥式整流器后接大电容的开关电源易产生谐波电流。这些谐波电流只是增加了电源输入电流的RMS，而对真正的功率没有任何贡献。典型的解决方案是对现有的设计增加一个PFC预稳压器和单独的控制器。LT1508和LT1509通过将PFC和脉宽调制器(PWM)集成到芯片内部，取消了独立控制器，PFC通过编程升压稳压器的输入电流来获得。advertisementSingleIC,PowerFactorCorrected,Off-LineSupplyDesignNote143KurkMathewsAneverincreasingnumberofoff-linepowersuppliesnowlowerpartcountandimprovedPCboardlayout.Start-upisincludepowerfactorcorrection(PFC)inordertoreducecontrolledbyseparatePFCandPWMsoftstartpins.Theinputcurrentandmeetfutureregulatoryrequirements.PWMSoftStartpinisheldlow,disablingthePWMoutputSwitchingpowersuppliesthatincorporateabridgerecti-untilthePFCstageisinregulation.ThePWMwillremainfierfollowedbybulkcapacitancecreateharmoniccur-enabledaslongasthePFCoutputvoltagestaysabove73%rents.Theseharmo……