BuckBoost雙向DCDC軟開關變換器的研究

BuckBoost雙向DCDC軟開關變換器的研究一、本文概述Overviewofthisarticle隨著現(xiàn)代電力電子技術的迅速發(fā)展，DC/DC變換器在各種電源系統(tǒng)、電動車、航空航天、可再生能源等領域中的應用越來越廣泛。其中，Buck-Boost雙向DC/DC變換器因其能同時實現(xiàn)升壓和降壓功能，且具有結構簡單、控制靈活等優(yōu)點，受到了廣泛關注。然而，傳統(tǒng)的Buck-Boost變換器存在開關損耗大、效率低、電磁干擾嚴重等問題，這在一定程度上限制了其應用范圍的擴大。Withtherapiddevelopmentofmodernpowerelectronicstechnology,theapplicationofDC/DCconvertersinvariouspowersystems,electricvehicles,aerospace,renewableenergyandotherfieldsisbecomingincreasinglywidespread.Amongthem,BuckBoostbidirectionalDC/DCconvertershavereceivedwidespreadattentionduetotheirabilitytosimultaneouslyachieveboostandbuckfunctions,aswellastheiradvantagessuchassimplestructureandflexiblecontrol.However,traditionalBuckBoostconverterssufferfromproblemssuchashighswitchinglosses,lowefficiency,andsevereelectromagneticinterference,whichtosomeextentlimitstheirapplicationscope.為了克服這些問題，本文提出了一種基于軟開關技術的Buck-Boost雙向DC/DC變換器。軟開關技術通過在開關過程中引入諧振過程，實現(xiàn)開關管的零電壓或零電流開關，從而有效降低開關損耗，提高變換器的效率。軟開關技術還有助于減小電磁干擾，提高系統(tǒng)的可靠性。Toovercometheseissues,thispaperproposesaBuckBoostbidirectionalDC/DCconverterbasedonsoftswitchingtechnology.Softswitchingtechnologyintroducesresonantprocessesduringtheswitchingprocesstoachievezerovoltageorzerocurrentswitchingoftheswitchingtransistor,effectivelyreducingswitchinglossesandimprovingtheefficiencyoftheconverter.Softswitchingtechnologyalsohelpstoreduceelectromagneticinterferenceandimprovesystemreliability.本文首先介紹了Buck-Boost雙向DC/DC變換器的基本原理和應用背景，然后詳細闡述了軟開關技術的基本原理和實現(xiàn)方法。在此基礎上，本文設計了一種基于軟開關技術的Buck-Boost雙向DC/DC變換器，并對其進行了理論分析和仿真研究。仿真結果表明，該變換器具有較低的開關損耗、較高的效率和較小的電磁干擾。ThisarticlefirstintroducesthebasicprincipleandapplicationbackgroundofBuckBoostbidirectionalDC/DCconverter,andthenelaboratesonthebasicprincipleandimplementationmethodofsoftswitchingtechnologyindetail.Onthisbasis,thispaperdesignsaBuckBoostbidirectionalDC/DCconverterbasedonsoftswitchingtechnology,andconductstheoreticalanalysisandsimulationresearchonit.Thesimulationresultsshowthattheconverterhaslowerswitchinglosses,higherefficiency,andsmallerelectromagneticinterference.本文對所提出的Buck-Boost雙向DC/DC軟開關變換器進行了實驗驗證。實驗結果表明，該變換器在實際應用中具有良好的性能表現(xiàn)，有望在電力電子領域得到廣泛應用。ThisarticleexperimentallyverifiestheproposedBuckBoostbidirectionalDC/DCsoftswitchingconverter.Theexperimentalresultsshowthattheconverterhasgoodperformanceinpracticalapplicationsandisexpectedtobewidelyusedinthefieldofpowerelectronics.本文的研究不僅為Buck-Boost雙向DC/DC變換器的優(yōu)化設計提供了新的思路和方法，也為軟開關技術在其他類型DC/DC變換器中的應用提供了有益的參考。ThisstudynotonlyprovidesnewideasandmethodsfortheoptimizationdesignofBuckBoostbidirectionalDC/DCconverters,butalsoprovidesusefulreferencesfortheapplicationofsoftswitchingtechnologyinothertypesofDC/DCconverters.二、BuckBoost雙向DCDC軟開關變換器的基本原理ThebasicprincipleofBuckBoostbidirectionalDCDCsoftswitchingconverterBuckBoost雙向DCDC軟開關變換器是一種高效的電力轉換裝置，它結合了Buck和Boost兩種基本變換器的特點，并引入了軟開關技術以提高效率、減少開關損耗和降低電磁干擾。其基本原理在于通過控制開關管的開通和關斷，實現(xiàn)輸出電壓與輸入電壓之間的升降壓轉換，并且能夠在轉換過程中實現(xiàn)軟開關，從而優(yōu)化電能轉換效率。BuckBoostbidirectionalDCDCsoftswitchingconverterisanefficientpowerconversiondevicethatcombinesthecharacteristicsofBuckandBoostbasicconverters,andintroducessoftswitchingtechnologytoimproveefficiency,reduceswitchinglosses,andreduceelectromagneticinterference.Thebasicprincipleistoachievevoltageriseandfallconversionbetweenoutputvoltageandinputvoltagebycontrollingtheopeningandclosingoftheswitchingtube,andtoachievesoftswitchingduringtheconversionprocess,therebyoptimizingtheefficiencyofelectricalenergyconversion.在BuckBoost雙向DCDC軟開關變換器中，主要包含兩個開關管、兩個二極管、一個儲能電感以及一個濾波電容。兩個開關管交替工作，根據(jù)輸入電壓和輸出電壓的需求，通過PWM（脈沖寬度調(diào)制）控制信號調(diào)節(jié)開關管的導通時間，從而控制輸出電壓的大小。當開關管導通時，電能通過儲能電感儲存，當開關管關斷時，電感釋放能量，驅動輸出電壓。IntheBuckBoostbidirectionalDCDCsoftswitchingconverter,itmainlyincludestwoswitchingtransistors,twodiodes,anenergystorageinductor,andafilteringcapacitor.Twoswitchingtubesworkalternately,andaccordingtotherequirementsofinputvoltageandoutputvoltage,theconductiontimeoftheswitchingtubesisadjustedthroughPWM(pulsewidthmodulation)controlsignaltocontrolthesizeoftheoutputvoltage.Whentheswitchisturnedon,electricalenergyisstoredthroughtheenergystorageinductor.Whentheswitchisturnedoff,theinductorreleasesenergyanddrivestheoutputvoltage.為了實現(xiàn)軟開關，變換器通常引入諧振電路。在開關管切換狀態(tài)時，諧振電路產(chǎn)生諧振，使開關管兩端的電壓或電流在開關過程中逐漸變化，避免了開關管在瞬間切換時產(chǎn)生的高電壓或高電流，從而減少了開關損耗。Inordertoachievesoftswitching,convertersusuallyintroduceresonantcircuits.Whentheswitchingstateoftheswitchingtubeisswitched,theresonantcircuitgeneratesresonance,causingthevoltageorcurrentatbothendsoftheswitchingtubetograduallychangeduringtheswitchingprocess,avoidingthehighvoltageorcurrentgeneratedbytheswitchingtubeduringinstantaneousswitching,therebyreducingswitchinglosses.BuckBoost雙向DCDC軟開關變換器還具有雙向能量流動的能力。當需要升壓時，電能從輸入端流向輸出端；當需要降壓時，電能從輸出端流向輸入端。這種雙向能量流動的能力使得變換器在能源管理、電動汽車充電、可再生能源系統(tǒng)等領域有著廣泛的應用前景。TheBuckBoostbidirectionalDCDCsoftswitchingconverteralsohastheabilityofbidirectionalenergyflow.Whenaboostisneeded,electricalenergyflowsfromtheinputendtotheoutputend;Whenvoltagereductionisrequired,electricalenergyflowsfromtheoutputendtotheinputend.Theabilityofbidirectionalenergyflowmakesconvertershavebroadapplicationprospectsinenergymanagement,electricvehiclecharging,renewableenergysystems,andotherfields.BuckBoost雙向DCDC軟開關變換器通過控制開關管的開通和關斷，結合諧振電路實現(xiàn)軟開關技術，能夠在輸入輸出電壓之間實現(xiàn)高效的升降壓轉換，具有高效率、低損耗、低電磁干擾等優(yōu)點，是現(xiàn)代電力電子領域的重要研究方向。TheBuckBoostbidirectionalDCDCsoftswitchingconverterachievesefficientvoltageriseandfallconversionbetweeninputandoutputvoltagesbycontrollingtheopeningandclosingofswitchingtubes,combinedwithresonantcircuitstoachievesoftswitchingtechnology.Ithastheadvantagesofhighefficiency,lowloss,andlowelectromagneticinterference,andisanimportantresearchdirectioninthefieldofmodernpowerelectronics.三、BuckBoost雙向DCDC軟開關變換器的設計與實現(xiàn)DesignandImplementationofBuckBoostBidirectionalDCDCSoftSwitchingConverterBuckBoost雙向DCDC軟開關變換器是一種高效、靈活的電能轉換裝置，能夠在寬輸入電壓范圍內(nèi)實現(xiàn)電壓的升降轉換，同時采用軟開關技術以降低開關損耗，提高系統(tǒng)效率。本節(jié)將詳細介紹該變換器的設計與實現(xiàn)過程。BuckBoostbidirectionalDCDCsoftswitchingconverterisanefficientandflexibleelectricalenergyconversiondevicethatcanachievevoltageriseandfallconversionwithinawideinputvoltagerange.Atthesametime,softswitchingtechnologyisusedtoreduceswitchinglossesandimprovesystemefficiency.Thissectionwillprovideadetailedintroductiontothedesignandimplementationprocessoftheconverter.BuckBoost雙向DCDC軟開關變換器基于Buck和Boost電路的結合，通過改變開關管的工作狀態(tài)，實現(xiàn)電能的雙向流動和電壓的升降轉換。在設計中，我們采用了軟開關技術，通過在開關管切換過程中引入諧振環(huán)節(jié)，使開關管在零電壓或零電流條件下進行切換，從而減小了開關損耗，提高了系統(tǒng)的效率。TheBuckBoostbidirectionalDCDCsoftswitchingconverterisbasedonthecombinationofBuckandBoostcircuits.Bychangingtheworkingstateoftheswitchingtransistor,itachievesbidirectionalflowofelectricalenergyandvoltageriseandfallconversion.Inthedesign,weadoptedsoftswitchingtechnology,whichintroducesaresonantlinkduringtheswitchingprocessoftheswitchingtube,allowingtheswitchingtubetoswitchunderzerovoltageorzerocurrentconditions,therebyreducingswitchinglossesandimprovingsystemefficiency.在變換器的設計過程中，我們需要選擇合適的開關管、諧振電感、諧振電容等關鍵參數(shù)。開關管的選擇需要考慮其耐壓、耐流能力以及開關速度等因素；諧振電感和諧振電容的選擇則需要根據(jù)系統(tǒng)的諧振頻率、開關管的開關速度以及所需的軟開關效果來確定。Inthedesignprocessoftheconverter,weneedtochooseappropriatekeyparameterssuchasswitchingtubes,resonantinductors,resonantcapacitors,etc.Theselectionofswitchtubesneedstoconsiderfactorssuchasvoltageresistance,currentresistance,andswitchingspeed;Theselectionofresonantinductanceandresonantcapacitorneedstobedeterminedbasedontheresonantfrequencyofthesystem,theswitchingspeedoftheswitchingtube,andtherequiredsoftswitchingeffect.為了實現(xiàn)對變換器的精確控制，我們采用了PWM（脈沖寬度調(diào)制）控制技術，通過對開關管的占空比進行調(diào)節(jié)，實現(xiàn)對輸出電壓的穩(wěn)定控制。同時，為了減小開關損耗，我們引入了軟開關控制策略，通過調(diào)整PWM信號的相位和占空比，使開關管在零電壓或零電流條件下進行切換。Inordertoachieveprecisecontroloftheconverter,weadoptedPWM(PulseWidthModulation)controltechnology,whichadjuststhedutycycleoftheswitchingtubetoachievestablecontroloftheoutputvoltage.Atthesametime,inordertoreduceswitchinglosses,weintroduceasoftswitchingcontrolstrategy,whichadjuststhephaseanddutycycleofthePWMsignaltoswitchtheswitchingtransistorunderzerovoltageorzerocurrentconditions.為了驗證設計的有效性，我們搭建了實驗平臺，對變換器進行了實驗驗證。實驗結果表明，該變換器能夠在寬輸入電壓范圍內(nèi)實現(xiàn)電壓的升降轉換，同時采用軟開關技術后，開關損耗明顯降低，系統(tǒng)效率得到了顯著提高。Inordertoverifytheeffectivenessofthedesign,webuiltanexperimentalplatformandconductedexperimentalverificationontheconverter.Theexperimentalresultsshowthattheconvertercanachievevoltageriseandfallconversionwithinawideinputvoltagerange.Atthesametime,withtheuseofsoftswitchingtechnology,theswitchinglossissignificantlyreduced,andthesystemefficiencyissignificantlyimproved.通過對BuckBoost雙向DCDC軟開關變換器的設計與實現(xiàn)過程進行詳細介紹，我們可以看到該變換器在電能轉換領域具有廣闊的應用前景。未來，我們將進一步優(yōu)化控制策略、提高變換器的效率和穩(wěn)定性，以滿足更多領域的需求。ByprovidingadetailedintroductiontothedesignandimplementationprocessoftheBuckBoostbidirectionalDCDCsoftswitchingconverter,wecanseethattheconverterhasbroadapplicationprospectsinthefieldofpowerconversion.Inthefuture,wewillfurtheroptimizecontrolstrategies,improvetheefficiencyandstabilityofconverters,tomeettheneedsofmorefields.四、BuckBoost雙向DCDC軟開關變換器的性能分析PerformanceanalysisofBuckBoostbidirectionalDCDCsoftswitchingconverter在深入研究BuckBoost雙向DCDC軟開關變換器的過程中，性能分析是至關重要的一環(huán)。這一部分將詳細探討變換器的效率、動態(tài)響應、電壓和電流應力以及熱性能等方面的表現(xiàn)。Performanceanalysisiscrucialinthein-depthstudyofBuckBoostbidirectionalDCDCsoftswitchingconverters.Thissectionwillexploreindetailtheperformanceoftheconverterintermsofefficiency,dynamicresponse,voltageandcurrentstress,andthermalperformance.效率是衡量變換器性能的關鍵指標之一。在BuckBoost雙向DCDC軟開關變換器中，由于軟開關技術的應用，開關損耗得以顯著減少，從而提高了整體效率。通過對比分析傳統(tǒng)硬開關與軟開關的效率曲線，可以清晰地看到軟開關技術在提高效率方面的優(yōu)勢。變換器的效率還受到負載條件、開關頻率以及控制策略等因素的影響，因此在實際應用中需要綜合考慮這些因素以優(yōu)化效率。Efficiencyisoneofthekeyindicatorsformeasuringtheperformanceofconverters.InBuckBoostbidirectionalDCDCsoftswitchingconverters,theapplicationofsoftswitchingtechnologysignificantlyreducesswitchinglosses,therebyimprovingoverallefficiency.Bycomparingandanalyzingtheefficiencycurvesoftraditionalhardswitchingandsoftswitching,itiscleartoseetheadvantagesofsoftswitchingtechnologyinimprovingefficiency.Theefficiencyoftheconverterisalsoaffectedbyfactorssuchasloadconditions,switchingfrequency,andcontrolstrategy.Therefore,inpracticalapplications,thesefactorsneedtobecomprehensivelyconsideredtooptimizeefficiency.動態(tài)響應能力是衡量變換器對突發(fā)負載變化適應能力的重要指標。在BuckBoost雙向DCDC軟開關變換器中，由于軟開關技術的引入，開關過程的瞬態(tài)沖擊得以減輕，從而提高了系統(tǒng)的穩(wěn)定性。通過仿真和實驗驗證，可以發(fā)現(xiàn)變換器在負載突變時能夠迅速調(diào)整輸出電壓和電流，保持系統(tǒng)的穩(wěn)定運行。Dynamicresponsecapabilityisanimportantindicatorformeasuringtheadaptabilityofaconvertertosuddenloadchanges.IntheBuckBoostbidirectionalDCDCsoftswitchingconverter,theintroductionofsoftswitchingtechnologyreducesthetransientimpactoftheswitchingprocess,therebyimprovingthestabilityofthesystem.Throughsimulationandexperimentalverification,itcanbefoundthattheconvertercanquicklyadjusttheoutputvoltageandcurrentwhentheloadsuddenlychanges,maintainingthestableoperationofthesystem.電壓和電流應力也是評估變換器性能的重要指標。在BuckBoost雙向DCDC軟開關變換器中，通過合理的電路設計和控制策略，可以有效地降低開關管和其他關鍵元件的電壓和電流應力，從而提高系統(tǒng)的可靠性和壽命。Voltageandcurrentstressarealsoimportantindicatorsforevaluatingtheperformanceofconverters.InBuckBoostbidirectionalDCDCsoftswitchingconverters,reasonablecircuitdesignandcontrolstrategiescaneffectivelyreducethevoltageandcurrentstressofswitchingtubesandotherkeycomponents,therebyimprovingthereliabilityandlifespanofthesystem.熱性能分析也是評估變換器性能不可忽視的一部分。在實際應用中，變換器在工作過程中會產(chǎn)生一定的熱量，如果散熱不良，將影響變換器的性能和穩(wěn)定性。因此，通過對變換器的熱設計進行優(yōu)化，如增加散熱片、改善通風條件等，可以有效地提高變換器的熱性能，確保其長期穩(wěn)定運行。Thermalperformanceanalysisisalsoanindispensablepartofevaluatingtheperformanceofconverters.Inpracticalapplications,convertersgenerateacertainamountofheatduringoperation.Iftheheatdissipationispoor,itwillaffecttheperformanceandstabilityoftheconverter.Therefore,byoptimizingthethermaldesignoftheconverter,suchasaddingheatsinksandimprovingventilationconditions,thethermalperformanceoftheconvertercanbeeffectivelyimproved,ensuringitslong-termstableoperation.通過對BuckBoost雙向DCDC軟開關變換器的性能分析，我們可以全面了解其在實際應用中的表現(xiàn)，為進一步優(yōu)化設計和提高性能提供有力支持。ByanalyzingtheperformanceofBuckBoostbidirectionalDCDCsoftswitchingconverter,wecancomprehensivelyunderstanditsperformanceinpracticalapplications,providingstrongsupportforfurtheroptimizingdesignandimprovingperformance.五、BuckBoost雙向DCDC軟開關變換器的應用前景ApplicationprospectsofBuckBoostbidirectionalDCDCsoftswitchingconverters隨著科技的不斷進步和電力電子技術的快速發(fā)展，BuckBoost雙向DCDC軟開關變換器作為一種高效、穩(wěn)定的電能轉換裝置，其應用前景十分廣闊。Withthecontinuousprogressoftechnologyandtherapiddevelopmentofpowerelectronicstechnology,theBuckBoostbidirectionalDCDCsoftswitchingconverter,asanefficientandstableenergyconversiondevice,hasaverybroadapplicationprospect.在可再生能源領域，BuckBoost雙向DCDC軟開關變換器發(fā)揮著重要作用。太陽能、風能等可再生能源的發(fā)電系統(tǒng)通常需要與電網(wǎng)進行能量交互，而這一過程就需要高效的電能轉換裝置。BuckBoost雙向DCDC軟開關變換器能夠實現(xiàn)電能的雙向流動，且轉換效率高，因此在可再生能源并網(wǎng)系統(tǒng)中具有廣泛的應用前景。Inthefieldofrenewableenergy,BuckBoostbidirectionalDCDCsoftswitchingconvertersplayanimportantrole.Renewableenergygenerationsystemssuchassolarandwindpowertypicallyrequireenergyinteractionwiththepowergrid,whichrequiresefficientenergyconversiondevices.TheBuckBoostbidirectionalDCDCsoftswitchingconvertercanachievebidirectionalflowofelectricalenergyandhashighconversionefficiency,makingitwidelyapplicableinrenewableenergygridconnectedsystems.在電動汽車領域，BuckBoost雙向DCDC軟開關變換器同樣具有巨大的應用潛力。電動汽車的充電系統(tǒng)需要實現(xiàn)電網(wǎng)與車載電池之間的能量轉換，而BuckBoost雙向DCDC軟開關變換器的高效率和穩(wěn)定性使其成為理想的選擇。隨著電動汽車的快速發(fā)展，車載電池的能量管理變得日益重要，BuckBoost雙向DCDC軟開關變換器能夠實現(xiàn)電池能量的高效管理，從而提高電動汽車的續(xù)航里程和性能。Inthefieldofelectricvehicles,BuckBoostbidirectionalDCDCsoftswitchingconvertersalsohaveenormousapplicationpotential.Thechargingsystemofelectricvehiclesrequiresenergyconversionbetweenthepowergridandtheonboardbattery,andthehighefficiencyandstabilityoftheBuckBoostbidirectionalDCDCsoftswitchingconvertermakeitanidealchoice.Withtherapiddevelopmentofelectricvehicles,energymanagementofinvehiclebatterieshasbecomeincreasinglyimportant.TheBuckBoostbidirectionalDCDCsoftswitchingconvertercanachieveefficientmanagementofbatteryenergy,therebyimprovingtherangeandperformanceofelectricvehicles.在工業(yè)自動化領域，BuckBoost雙向DCDC軟開關變換器也具有重要的應用價值。工業(yè)自動化系統(tǒng)中需要實現(xiàn)各種電氣設備的能量供應和控制，而BuckBoost雙向DCDC軟開關變換器能夠提供穩(wěn)定、高效的電能轉換，滿足工業(yè)自動化系統(tǒng)的需求。Inthefieldofindustrialautomation,BuckBoostbidirectionalDCDCsoftswitchingconvertersalsohaveimportantapplicationvalue.Inindustrialautomationsystems,itisnecessarytoachieveenergysupplyandcontrolofvariouselectricalequipment,andtheBuckBoostbidirectionalDCDCsoftswitchingconvertercanprovidestableandefficientenergyconversion,meetingtheneedsofindustrialautomationsystems.隨著電力電子技術的不斷發(fā)展，BuckBoost雙向DCDC軟開關變換器在智能電網(wǎng)、分布式發(fā)電系統(tǒng)等領域的應用也將不斷拓展。智能電網(wǎng)需要實現(xiàn)電網(wǎng)與各種分布式電源、儲能裝置之間的能量交互，而BuckBoost雙向DCDC軟開關變換器的高效、穩(wěn)定性能使其成為智能電網(wǎng)中的重要組成部分。Withthecontinuousdevelopmentofpowerelectronicstechnology,theapplicationofBuckBoostbidirectionalDCDCsoftswitchingconvertersinsmartgrids,distributedgenerationsystems,andotherfieldswillalsocontinuetoexpand.Thesmartgridneedstoachieveenergyinteractionbetweenthegridandvariousdistributedpowersourcesandenergystoragedevices,andtheefficientandstableperformanceoftheBuckBoostbidirectionalDCDCsoftswitchingconvertermakesitanimportantcomponentofthesmartgrid.BuckBoost雙向DCDC軟開關變換器在可再生能源、電動汽車、工業(yè)自動化等領域具有廣泛的應用前景，隨著技術的進步和應用領域的拓展，其市場需求將持續(xù)增長，為電力電子技術的發(fā)展注入新的活力。TheBuckBoostbidirectionalDCDCsoftswitchingconverterhasawiderangeofapplicationprospectsinrenewableenergy,electricvehicles,industrialautomationandotherfields.Withtheprogressoftechnologyandtheexpansionofapplicationareas,itsmarketdemandwillcontinuetogrow,injectingnewvitalityintothedevelopmentofpowerelectronicstechnology.六、結論Conclusion本研究對BuckBoost雙向DCDC軟開關變換器進行了深入的理論分析和實驗研究，旨在探討其工作原理、性能優(yōu)化以及在實際應用中的潛力。通過對比傳統(tǒng)硬開關變換器，我們發(fā)現(xiàn)BuckBoost雙向DCDC軟開關變換器在效率、熱管理和電磁干擾方面具有顯著優(yōu)勢。Thisstudyconductedin-depththeoreticalanalysisandexperimentalresearchontheBuckBoostbidirectionalDCDCsoftswitchingconverter,aimingtoexploreitsworkingprinciple,performanceoptimization,andpotentialinpracticalapplications.Bycomparingtraditionalhardswitchingconverters,wefoundthatBuckBoostbidirectionalDCDCsoftswitchingconvertershavesignificantadvantagesinefficiency,thermalmanagement,andelectromagneticinterference.在理論方面，我們詳細推導了BuckBoost雙向DCDC軟開關變換器的數(shù)學模型，并對其在不同負載和輸入電壓條件下的工作特性進行了仿真分析。仿真結果表明，軟開關技術的引入有效降低