Low-Power FPGA Designs - PDF document

Low-Power FPGA Designs POWERdesigner Q1 =D xNsxV 2100V Dual Interleaved Active-Clamp Current-ModeController ¥Independent current-mode controllers¥Interleaved single or dual output operation¥Compound 2.5A main FET gate drivers¥Active clamp FET gate drivers¥Integrated 100V start-up regulator¥Up to 1 MHz switching frequency ¥Programmable maximum duty cycle¥Adjustable soft-start and input under-¥Adjustable deadtime between main and¥Available in TSSOP-20 packagingindustrial, and automotive power supplies Converters while reducing input ripple 0 40 50 60 = 78V = 36V = 48Vt = 3.3V Timi LM5034 Efficiency GraphLM5034 Interleaved Forward Active Clamp Converter Figure 1shows the similarities between a buck andforward converter. Note the only difference betweenratio term (Ns/Np) in the forward transfer func-tion. Ns and Np are the number of secondary andprimary turns, wound on the transformer core.Figure 2presents a transformer model, including theÒMagnetizing InductanceÓ (Lm) shown in parallelwith the primary winding. This magnetizing induc-tance can be measured at the primary terminals withthe secondary winding(s) open circuit. The current inthe magnetizing inductance is proportional to theflux density within the core. A given size core canonly support a certain flux density before saturationof the core occurs. When the core saturates, there is arapid reduction in inductance. Another element ofthe transformer model is the ÒLeakage InductanceÓ) in series with the primary winding. This leakageinductance can be measured at the primary terminalswith the secondary winding(s) shorted. This termrepresents the stray primary inductance, which is notcoupled to the secondary.Figures 3athrough operational steps of an active clamp forward powerconverter. At time t0, the main power switch (Q1)is on, applying Vacross the transformer primary.The transformer secondary winding voltage is x Ns/Np. The primary current is comprised oftwo components at this time; the reflected currentfrom the output inductor (Icurrent ramping up in the magnetizing inductance(Lm). The reset switch Q2 is open and the clamp capacitor (Cc) has been previously charged to avoltage of V/(1-D), which will be explained later.This interval is the power phase, energy is transferred from the primary to the secondary during this period. The approximate duration ofthe power phase is Ts x V, where Ts is theAt time t1, the main power switch (Q1) is turnedoff and the reset switch (Q2) is turned on. Themagnetizing current flows through the clampcapacitor and Q2 instead of through Q1. Since theclamp capacitor voltage is greater than Vvoltage across the transformer primary is nowreversed, compared to the power phase t0. Becausethe potential across the magnetizing inductance hasbeen reversed, the magnitude of the magnetizingcurrent will decrease as the energy stored in the 3 Operation and Benefits of Active-Clamp Forward Power ConvertersPOWERdesigner NsNp Figure 2. Transformer Model INV Np– INV (1-D) Figure 3a. Operation at Step t0Figure 3b. Operation at Step t1power.national.com LM5026 Offers Versatile Dual-Mode Over-Current Protection with HiccupDelay Timer 3.3V Out48V InPWM ControlCurrent RestartSoft-startCurrentSenseMain andClampGateandOscillatorStart-up Rectifierand FilterPWM OUTA LM5026 Typical Application CircuitHiccup Over-Load Restart Timing Features ¥Wide range (8V to 100V) start-up bias ¥Two high-speed power MOSFET drivers: ¥User-programmable maximum duty-cycle¥User-programmable gate driver overlap¥Versatile dual-mode over-current ¥TSSOP-16 or thermally enhanced LLP-16Ideal for use in telecommunications power Product Highlight:controller offers highest efficiency 6 100V Half-Bridge Power MOSFET Drivers Driver river LOHOHBHSHIVDDLIVSS0.22 µF10V to 100V0.22 µF+10V LM50xx PWMcontrolleror microprocessorLoad(Integrated bootstrap) LM510x Family Offers the Industry’s Highest Peak Gate Drive Current ¥Flexible configurations: interleaved forward,¥User-programmable turn-on edge delay feature¥New high-voltage bootstrap diode¥Best-in-class speed and efficiency in high-fre-¥Negative load voltage transient capability down¥Available in SOIC and tiny, thermally enhanced topology and high efficiency Current Product ID Packaging CMOS / TTL 1.8A Programmable dead-time, negative V LLP-8, SOIC-8 LOAD LM510x Typical Application Circuit warranty.TestingandotherqualitycontroltechniquesareusedtotheextentTIdeemsnecessarytosupportthiswarranty.Exceptwhere mandatedbygovernmentrequirements,testingofallparametersofeachproductisnotnecessarilyperformed. TIassumesnoliabilityforapplicationsassistanceorcustomerproductdesign.Customersareresponsiblefortheirproductsand applicationsusingTIcomponents.Tominimizetherisksassociatedwithcustomerproductsandapplications,customersshouldprovide adequatedesignandoperatingsafeguards. TIdoesnotwarrantorrepresentthatanylicense,eitherexpressorimplied,isgrantedunderanyTIpatentright,copyright,maskworkright, orotherTIintellectualpropertyrightrelatingtoanycombination,machine,orprocess restrictions. ResaleofTIproductsorserviceswithstatementsdifferentfromorbeyondtheparametersstatedbyTIforthatproductorservicevoidsall expressandanyimpliedwarrantiesfortheassociatedTIproductorserviceandisanunfairanddeceptivebusinesspractice.TIisnot responsibleorliableforanysuchstatements. TIproductsarenotauthorizedforuseinsafety-criticalapplications(suchaslifesupport)whereafailureoftheTIproductwouldreasonably beexpectedtocauseseverepersonalinjuryordeath,unlessofficersofthepartieshaveexecutedanagreementspecificallygoverning suchuse.Buyersrepresentthatthey specifications.BuyersacknowledgeandagreethatanysuchuseofTIproductswhichTIhasnotdesignatedasmilitary-gradeissolelyat theBuyer\nsrisk,andthattheyaresolelyresponsibleforcompliancewithalllegalandregulatoryrequirementsinconnectionwithsuchuse. TIproductsareneitherdesignednorintendedforuseinautomotiveapplicationsorenvironmentsunlessthespecificTIproductsare designatedbyTIascompliantwithISO/TS16949requirements.Buyersacknowledgeandagreethat,iftheyuseanynon-designated productsinautomotiveapplications,TIwillnotberesponsibleforanyfailuretomeetsuchrequirements. FollowingareURLswhereyoucanobtaininformationonotherTexasInstrumentsproducts www.ti.com/security Logic logic.ti.com Space,AvionicsandDefense www.ti.com/space-avionics-defense PowerMgmt power.ti.com TransportationandAutomotive www.ti.com/automotive Microcontrollers microcontroller.ti.com VideoandImaging www.ti.com/video RFID www.ti-rfid.com OMAPMobileProcessors www.ti.com/omap WirelessConnectivity www.ti.com/wirelessconnectivity TIE2ECommunityHomePage e2e.ti.com MailingAddress:TexasInstruments,PostOfficeBox655303,Dallas,Texas75265 Copyright‹2011,TexasInstrumentsIncorporated