DC-DC-SEPIC-Converter

FAEPETERYE（叶兵）DCDCSEPICCONVERTER概述功率50W类似反激，在开关管OPEN时能量的传输到输出输入电流连续，电压纹波较小，输入电容较小，EMI较小输出电流纹波较大Page2SimplecircuitdiagramofSepicconvertPage3ThewaveformsoftheSEPICconverterswitchingvoltageandcurrentPage4BasicoperationPage5SwitchturnonL1chargingCpdischargingL2chargingCoutdischargingQ1onDuringtheswitch(Q1)ONtime,thevoltageacrossbothinductorsisequaltoVIN.WhentheswitchisON,capacitorCpisconnectedinparallelwithL2.ThevoltageacrossL2isthesameasthecapacitorvoltage,-Vin.DiodeD1isthereversebias,andtheloadcurrentisbeingsuppliedbycapacitorCout.Duringthisperiod,energyisbeingstoredinL1fromtheinputandinL2fromCpPage6Q1offSwitchturnoffL1dischargingCpchargingL2dischargingCoutchargingDuringtheswitch(Q1)OFFtime,thecurrentinL1continuestoflowthroughCpandD1,andthenintoCout.Inthemeantime,theCpischargedandreadyforthenextcycle.ThecurrentinL2alsoflowsintoCoutandtheload,ensuringthatCoutisreadyforthenextcycle.SEPICConverterDesignGuideWhentheswitchisclosed,theDiodeisreversebiasedandopen,CurrentIL1increaseattherateof𝑑𝑖𝐿1𝑑𝑡=𝑉𝑖𝑛𝐿1，0≤t≤DTSothatL1ischarging.Whentheswitchisopen，thediodeisforwardbiased，andILdecreaseattherateof𝑑𝑖𝐿1𝑑𝑡=−𝑉out𝐿1，DTtTVout=Vin∗D1−D𝐼out=𝐼in∗D1−DSoconverterisinBUCKmodeforD0.5inBOOSTmodeforD0.5DutycycleInCCMmode𝐷𝑚𝑖𝑛=𝑉𝑜𝑢𝑡+𝑉𝐷𝑉𝐼𝑁(𝑀𝐴𝑋)+𝑉𝑂𝑈𝑇+𝑉𝐷𝐷𝑚𝑎𝑥=𝑉𝑜𝑢𝑡+𝑉𝐷𝑉𝐼𝑁(𝑚𝑖𝑛)+𝑉𝑂𝑈𝑇+𝑉𝐷Page7Page8∆𝐼1=𝑉𝑜𝑢𝑡(1−𝐷)𝐿1∗𝑓∆𝐼2=−𝑉𝑜𝑢𝑡(1−𝐷)𝐿2∗𝑓2𝐼in=𝑉𝑜𝑢𝑡(1−𝐷)𝐿1boundary∗𝑓CCMCCMCCMBCM2𝐼𝑜𝑢𝑡=−𝑉𝑜𝑢𝑡(1−𝐷)𝐿2boundary∗𝑓𝐿1𝑉in2∗𝐼in∗𝑓𝐿2𝑉𝑜𝑢𝑡2∗𝐼2∗𝑓∆𝐼I=0.3CalculationofL1andL2CouplingCapacitorSelectionPage9∆𝑉𝐶𝑃𝑉𝐶𝑃=5%𝐶𝑃=𝐼𝑜𝑢𝑡∗𝐷𝑀𝐴𝑋∆𝑉𝐶𝑃∗𝑓where∆𝑉𝐶𝑃istheripplevoltagewhichisacrossCP.ThemaximumvoltageacrossCPisVIN.英飞凌TLD5097EL的sepic电路解决方案Page10Thanks!