开关电源变压器设计

Bmax4.14—12WFlyback路简单成本廉容易得到多路应用广泛100W以下小功难点模式随着负化而化条下模式(CCM)条下(DCM)sA90；ClassB。主要考虑重要如何将变价体积品质者努力方向。~fLVoIofSPoη40℃.0 4.1 Vmos:VDVF4.2 (Typ.=20%)N 0.8D>inmax/N+oF0.S>(o+F)+Vnx比n<N<Nx4.32μF~3μF/W( tc=3ms)

)2−2×ᵄCᵅVᵅ[(ᵄG−ᵆᵅP)inmin= ᵄNᵅPᵅZᵅVᵅ[ ᵃ62低，时，占空DmaxDmax

= ᵄA?()ᵄA?(ᵅ\ ᵃ9) ᵅVᵅ[ᵅZᵅVᵅ[4.4 激换过程分析低时，负载从轻载到重载，DCM→BCM→CCM过程高时，负载从轻载到重载，一直DCM4.5 初级临界均峰值按照小，(Pomax)条Po=1/3PomaxBCMPo<1/3PomaxDCMPo>1/3PomaxBCM1?ᵄCᵅVᵅ[

Iin-avg=

3ᵄIᵅVᵅ[ᵅZᵅVᵅ[

?Ip1=I

pk1

= 2×ᵃᵅVᵅ[ ᵄNᵆcᵅTᵃ7ᵅZᵄNᵆe4.6 BCM1Tonmax=

× DmaxLp= ᵄᵅVᵅ[ᵅZᵅVᵅ[×[?ᵅ]14.7 APp

= ×1062×y×ᵃ>ᵅ\×ᵃ>ᵅP×ᵅSᵆ`×ᵃ5ᵅZ×ᵅWKoKo=0.4KcKc=1mBmB≤1m2

ᵃ5ᵆ`ᵄNᵆajj=4.2A/mm2Ae4.8 、次匝、辅助组匝气隙长度组匝数N = Vinmin×tonp Ae×Bm

×108增加或者减匝只会分别引起损耗减或增加100kHzB2.86成正比匝减5%会使15%次组匝Ns=/N辅助组匝Ncc=(Vcc+1) × Ns/(Vo+VF)0.4n×ᵃ4ᵅR×ᵄA2:.9 满载

ᵃ?ᵅ]MTnxBCMTnxMTnxTonmax

?Ip1

= ᵄ[[×[ᵃ?ᵅ]

= ?Ip21Po= 21

×

×(I2

pk2

–

pk0

) ×fs

pk2

= /yᵄᵅVᵅ[ᵅZᵅVᵅ[×ᵅZᵄNᵆe

+ ?ᵄC224.10 Bmax

= ᵃᵅ]×ᵃ4ᵅR×

×<

sat

Bmax<Bsat

I =I

?ᵃ<-

I

=I√ᵃ7a k 2

prms

a ᵅZᵄNᵆeIdc=x× Ia Ic=(1−)j=4A/mm2Sp=Is(A)/4(A/m2)Ss=s(A)/4(A/m2)6.61/ cm超过2倍若超过则需多股并绕据安规要求考虑加宽挡墙K0Aw ≥ Np×n×ᵄE2+Ns×n×ᵄE2+Ncc×n×ᵄE2ᵅ] ᵆ`铜损

ᵅPᵅP据阻和确每个铜损耗总损耗要小预损耗温经验公式?T ≈ 800×ᵄCᵅYᵅ\ᵆ`ᵆ`34×ᵃ4ᵅR4ᵆd结构工艺骨架选累高宽度和次(三明治)法漏小—12W 开关电源变压器系统输入规格输入电压：90Vac~265Vac输入频率：50Hz输出电压：12V开关频率：50kHz预估效率：0.75输入最大功率：Pin=16W变压器最大温升：40℃MOSFET和输出整流二极管开关管MOSFET耐压:Vmos=600V输出二极管：反向压降VD=100V(正向导通压降VF=0.5V)算变压器匝比0.8 ? VD>Vinmax/N+Vo 0.8 × 100>375/N+120.8 ? Vmos>N ? (Vo+VF)+max 0.8 × 600>N × (12+0.5)+3755.5<N<8.4取N=6最低输入电压和最大占空比选择Cin=22μF最低输入电压：Vinmin

√ᵄNᵅPᵅZᵅVᵅ[

)2− 2×ᵄCᵅVᵅ[(ᵄG−ᵆᵅP)2ᵃ6ᵅVᵅ[2

=√1272

2×16×7×−130≈77ᵄI22×10−6最大占空比：Dmax= ᵄA?)ᵄA?(ᵅ\ ᵃ9) [

6×12.5= 6×12.5 77

=0.49算初级临界电流均值和峰值33

1?ᵄCᵅVᵅ[ᵄIᵅVᵅ[

16=3×77

=0.07A?Ip1=Ipk1=

2×ᵃ<ᵅVᵅ[−ᵄNᵆcᵅTᵃ7ᵅZᵄNᵆe

2×0.07= 0.49 =0.285A最大导通时间和初级电感量onmax

1

× Dmax=9.8 µᵆ`.7

= ᵄᵅVᵅ[ᵅZᵅVᵅ[[?ᵅ]1

77×9.8×10 = 0.285

≈ 2.7mHAPp=

12×1062×0.75×0.42×50×103×1600×4 =0.066cm2(Bsat= 3900G,Bm=1600G)EF20 Ae=5Aw = 0.6048P=Aw*Ae=2m2>6m25.8 N = 77×9.810 6140.7 N

=140Tsp 0.335×1600 pNs=/6Ts Ns=Ncc=19 × 23/12.5 ≈ 35l = 0.4n×33.5×g 2.6

= 0.2 mm 5.9 Ipk2=

ᵄCᵅ\/y[ᵅZᵅVᵅ[×ᵃ7ᵅZᵄNᵆe+

2 =

1677×0.49 +0.14=0.56Aᵃ?ᵅ]×ᵃ<ᵅ]ᵅX2Bmax= ᵃ4ᵅR×ᵄAᵅ]

2.6×10 3×= 0.335×140

×=3100G<3900G5.10 Ipa=Iprms=0.29AIpdc=Ipac=0.208AIsdc==Isa=Iac=0.959A5116.61/ =6.61/ √50×103 =0.29cm横截j=4.2~5A/mm2p2m×PC=m ()s=2×PC=m ()Vcccc=2=2 ×4 × 8 ≥ 0 × π× 52 +3 × π×0.22+5 ×π× 0.0224.2 ≥ 13.6 OK5.12 lav23.5mmlNp=140×23.5=329cmlNs=23×23.5=54.0cmRpdc=1.45Ω Rpac=2.38ΩRsdc=0.024Ω Vccᵅ]= ᵃ<2 ×

+ᵃ<2 ×

=0.22ᵄJuP =0.30W u

ᵅ]ᵅ_ᵅZᵆ`ᵆ`ᵅ_ᵅZᵆ`ᵆ`= ᵃ<2 ×ᵆ`ᵅ_ᵅZᵆ`

ᵅ]ᵅQᵅPᵆ`ᵅQᵅP

ᵅ]ᵄNᵅP2ᵆ`ᵄNᵅP

ᵅ]ᵄNᵅPᵆ`ᵄNᵅP

=0.08ᵄJ+ ᵃ< × 51+ ᵃ< × PC40ΔB=TW/3FeP =80 × 1.5=0.12WFe估温升总总loss

=0.12+0.30