铁氧体磁芯及其应用-NCD

DoOurBesttoBecomeBigger&Stronger铁氧体磁芯及其应用2007年1月DoOurBesttoBecomeBigger&Stronger提纲关于铁氧体关于铁氧体磁芯的一般应用关于用于平面变压器的铁氧体DoOurBesttoBecomeBigger&Stronger关于铁氧体磁性材料的分类硬磁(永磁)材料——金属永磁(NdFeB/SmCo/AlNiCo)永磁铁氧体(Sr/Ba)软磁材料——金属软磁(Fe/FeNi/FeSiAl/非晶态合金/微晶)软磁铁氧体(MnZn/NiZn/MgZn)旋磁材料——旋磁铁氧体(尖晶石系/柘榴石系/六角晶系）矩磁材料——磁纪录材料(γ-Fe2O3/CoO)DoOurBesttoBecomeBigger&Stronger软磁铁氧体的定义及特征软磁铁氧体是可表示为下列分子式的尖晶石晶体结构的磁性材料MFe2O4式中M代表锰、镍、锌、铜、镁、钴等二价金属离子。DoOurBesttoBecomeBigger&Stronger软磁铁氧体的主要优点电阻率远大于金属磁性材料，这抑制了涡流的产生，使铁氧体能应用于高频领域；采用陶瓷工艺易于制成各种不同的形状和尺寸；化学特性稳定、不生锈；较低的制造成本。软磁铁氧体的主要缺点饱和磁通密度较低，质地脆，易碎。DoOurBesttoBecomeBigger&Stronger软磁铁氧体的主要用途主要制成磁芯用于各种电感器、变压器、滤波器和扼流圈的制造，广泛应用于现代电子信息领域，如电脑及其外部设备、办公自动化设备、数字通信和模拟通信设备、互联网、家用电器、电磁兼容设备、绿色照明装置、工业自动化和汽车、航空、航天及军事领域。DoOurBesttoBecomeBigger&Stronger种类繁多的软磁铁氧体磁芯DoOurBesttoBecomeBigger&Stronger软磁铁氧体具有广泛的用途DoOurBesttoBecomeBigger&Stronger软磁铁氧体制造工艺流程按照预定的配方称重，把高纯、粉状的氧化物(如Fe2O3、Mn304、ZnO、NiO、MgO等)混合均匀，再经过预烧、粉碎、造粒，模压成型为毛坯，在高温(1200℃—1400℃)下烧结。再通过磨削加工、分类和包装获得成品。DoOurBesttoBecomeBigger&StrongerDoOurBesttoBecomeBigger&Stronger软磁铁氧体的技术原理磁芯的显微结构放大500倍DoOurBesttoBecomeBigger&Stronger磁畴及磁化过程DoOurBesttoBecomeBigger&Stronger磁化曲线及磁滞回线DoOurBesttoBecomeBigger&Stronger1、初始磁导率μi初始磁导率是磁性材料的磁导率(μ=B/H)在磁化曲线始端的极限值，即式中μ0为真空磁导率(4π×10-7H／m)H为磁场强度(A／m)B为磁通密度(T)软磁铁氧体的主要技术性能参数DoOurBesttoBecomeBigger&Stronger磁导率和磁化曲线的关系DoOurBesttoBecomeBigger&Stronger2.有效磁导率μe为了绕制的方便，在变压器及滤波器等器件中,常采用两只形状相同的磁芯配对构成闭合磁路。由于磁路各部份形状尺寸不同，且配合面不可避免有残余气隙(为改善性能,有时在磁路人为开制气隙),因此要用有效磁导率来表征磁芯的性能。式中L为装有磁芯的线圈的电感量(H)N为线圈匝数le为有效磁路长度(m)Ae为有效截面积(m2)DoOurBesttoBecomeBigger&Stronger开气隙提高了磁芯抗饱和的能力DoOurBesttoBecomeBigger&StrongerDoOurBesttoBecomeBigger&Stronger3.饱和磁通密度Bs(T)磁化到饱和状态的磁通密度。4.剩余磁通密度Br(T)从饱和状态去除磁场后，剩余的磁通密度。5.矫顽力Hc(A/m)从饱和状态去除磁场后，磁芯继续被反向的磁场磁化，直至磁通密度减为零，此时的磁场强度称为矫顽力。DoOurBesttoBecomeBigger&Stronger6.居里温度Tc(℃)在该温度下材料由铁磁性(或亚铁磁性)转变成顺磁性。DoOurBesttoBecomeBigger&Stronger7.电阻率ρ(Ω/m)具有单位截面积和单位长度的磁性材料的电阻。8.密度d(kg/m3)单位体积材料的重量，即d=W/V式中W为磁芯的重量(kg)V为磁芯的体积(m3)DoOurBesttoBecomeBigger&Stronger9.功率损耗Pc(kW/m3、W/kg)磁芯在高磁通密度下的单位体积损耗或单位重量损耗。该磁通密度可表示为Bm=E/4.44fNAe式中Bm为磁通密度的峰值(T)f为频率(Hz)N为线圈匝数Ae为有效截面积(m2)E为励磁电压有效值(V)DoOurBesttoBecomeBigger&Stronger磁滞损耗Ph、涡流损耗Pe和剩余损耗Pr之和构成功率损耗：功率损耗又可用经验公式表示：Pc=CfaBmb式中C为常数，f为工作频率，Bm为工作磁通密度，对于常见的功率铁氧体材料而言，a为1.2，b约为2.5。Pc＝Ph＋Pe＋Pr＝f∮BdH+Cf2Bm2/ρ+Pr功率损耗的构成DoOurBesttoBecomeBigger&Stronger10.电感因数AL(nH/N2)电感因数定义为具有一定形状和尺寸的磁芯上每一匝线圈产生的电感量，即AL=L/N2式中L为装有磁芯的线圈的电感量(H)N为线圈匝数DoOurBesttoBecomeBigger&StrongerNCDMnZn软磁铁氧体材料分类1、LP系列功率铁氧体材料，主要用于开关电源变压器、扼流圈及其它功率转换领域，包括LP1、LP2、LP3、LP3A、LP4、LP8、LP9、LP13等。2、HP系列高磁导率铁氧体材料，主要用于EMI抑制器件和数字通讯领域的宽带、脉冲变压器，包括HP1、HP2、HP3等。DoOurBesttoBecomeBigger&StrongerDoOurBesttoBecomeBigger&StrongerDoOurBesttoBecomeBigger&StrongerDoOurBesttoBecomeBigger&StrongerDoOurBesttoBecomeBigger&StrongerDoOurBesttoBecomeBigger&Stronger关于铁氧体磁芯的一般应用小信号处理功率转换EMI抑制电波吸收DoOurBesttoBecomeBigger&Stronger小信号处理1、滤波线圈要求：低损耗（高Q），精确的电感量，良好的时间稳定性，固定的温度依赖性。适用的材料：R2KB(JSF)，N48(Epcos)适用的磁芯：罐型、RMDoOurBesttoBecomeBigger&Stronger2.宽带变压器通讯系统和数字网络用主要技术要求：高磁导率;有时要有良好的DC-Bias特性；低THD(ADSL应用时)。适合的磁芯形状：EE、EP、RM、POT、环形等适合的材料：HP2/HP2FHP3/HP3FDoOurBesttoBecomeBigger&StrongerDoOurBesttoBecomeBigger&Stronger3、调谐线圈4、电流互感器5、延迟线DoOurBesttoBecomeBigger&Stronger功率转换1、功率变压器2、输出扼流圈3、驱动变压器4、行输出变压器5、LCD背光源逆变器DoOurBesttoBecomeBigger&Stronger功率转换：DC-DC\AC-DC\DC-ACDoOurBesttoBecomeBigger&Stronger主磁芯变压器磁芯主要技术要求：在工作频率范围内和高温下有低的功率损耗损耗温度系数为负值有时需要气隙适合的磁芯形状：EE、EC、ETD、RM、PQ、EFD、EPC等适合的材料：LP2(＜100kHz)LP3(＜300kHz)LP3A(＜300kHz，小型化)LP4(200kHz—1MHz)功率转换：DC-DC\AC-DC\DC-ACDoOurBesttoBecomeBigger&Stronger磁芯规格的选择：传输功率DoOurBesttoBecomeBigger&StrongerLCD背光照明逆变器（backligtinginverter)DoOurBesttoBecomeBigger&Stronger在50—100kHz内有很低的损耗，损耗温度系数为负值低矮轮廓、小尺寸、重量轻适合的材料为LP3、LP3A适合的磁芯形状为UI、EFD、EPC、EE主要技术要求：DoOurBesttoBecomeBigger&StrongerDoOurBesttoBecomeBigger&StrongerDoOurBesttoBecomeBigger&Stronger用于行输出变压器（FBT)的铁氧体磁芯DoOurBesttoBecomeBigger&StrongerFBT基本工作原理图DoOurBesttoBecomeBigger&Stronger基本技术要求：在工作频率范围内(16—100kHz)低的功率损耗损耗温度系数为负值高温下(80—100℃)有高饱和磁通密度需要气隙(airgap)适用的磁芯形状：UYF适用的材料：LP3DoOurBesttoBecomeBigger&StrongerDoOurBesttoBecomeBigger&StrongerEMI抑制1.输入滤波器2.EMI滤波器DoOurBesttoBecomeBigger&Stronger铁氧体磁芯用于EMI抑制EMI抑制基本原理DoOurBesttoBecomeBigger&Stronger输入滤波器（共模扼流圈）DoOurBesttoBecomeBigger&StrongerDoOurBesttoBecomeBigger&StrongerEMI滤波器DoOurBesttoBecomeBigger&Stronger主要技术要求：在所需频率范围内有高的阻抗ZDoOurBesttoBecomeBigger&StrongerDoOurBesttoBecomeBigger&Stronger•适用的材料：MnZn系及NiZn系DoOurBesttoBecomeBigger&Stronger关于用于平面变压器的铁氧体DoOurBesttoBecomeBigger&StrongerSeveraltypesofplanardevicesDoOurBesttoBecomeBigger&StrongerAdvantagesofplanartechnologyTherearemanyadvantagesofplanarmagnetictechnologyoverconventionalwire-woundinductivecomponents.Anobviousadvantageisaverylowbuildheight,whichpromotesplanarindenserack-mountandportableequipment.DoOurBesttoBecomeBigger&StrongerPlanarmagneticsareverywellsuitedfordesignofhighperformanceswitch-modepowerconverters.LowACcopperlossesandgoodcouplingincreaseconversionefficiency.Levelshigherthan95%canbeachieved,providedthatthecoreisungappedoronlyhasamoderateairgap.Inaddition,lowleakageinductancereducesvoltagespikesandoscillationsthatcandamageMOSFETsan