高频变压器设计
确定磁心:
根据Po=12W,Sj=0.15(Pm)^1/2,选择EFD-20磁心
Ns=12匝(每匝1V)
最大占空比Dmax选择50%
Dmax= Vor/(Vor+Vimin-Vds(on))*100%=Vor/(Vor+10)=0.5
Vor=10V
确定初级绕组参数:
Np=Vor/(Vo+0.4)*Ns=10/(12+0.4)*12=9.68 取Np=10匝
Iavg=Po/n*Vimin=12/(0.8*10)=1.5A
Ip=Iavg/[(1-0.5Krp)*Dmax]=1.5/[(1-0.5*0.4)*0.5]=3.75A
Irms=Ip*[ D*(KRP^2/3-KRP+1)]^(1/2)=3.75*[0.5*(0.4^2/3-0.4+1)]^(1/2)=2.14A
选取初级绕组电流密度J=4A/mm^2
Dsm=1.13(Irms/j)^(1/2)=1.13(2.14/4)^(1/2)=0.83mm Sc=3.14*(0.83/2)^2=0.5408mm^2
d=66.1/(f)^(1/2)=66.1/(86000)^(1/2)=0.225mm 2d=0.45mm Dsm>2d
采用0.40mm线,Sd=3.14*(0.40/2)^2=0.1257mm^2 4Sd=0.5028
所以初级绕组采用4股0.4mm线并绕
Lp=1000000Po/[Ip*Ip*Krp(1-Krp/2)*f]*[Z(1-n)+n]/n=1000000*12/[3.75*3.75*0.4(1-0.4/2)*86000]*[0.5*(1-0.8)+0.8]/0.8=34.88uh 选择35uh\
确定次级绕组参数:
Ns=12匝
Isp=Ip*Np/Ns=3.75A*10/12=3.13A
Irms=Isp*[(1-Dmax)*(Krp*Krp/3-Krp+1)]^1/2=3.13*[(1-0.5)*(0.4*0.4/3-0.4+1)]^1/2=1.79A 选取次级绕组电流密度J=4A/mm^2
Dsm=1.13(Irms/j)^(1/2)=1.13(1.79/4)^(1/2)=0.76mm Sc=3.14*(0.76/2)^2=0.4534mm^2
Dsm>2d 采用0.35mm^2线, Sd＝3.14*(0.35/2)^2=0.09621mm^2 4Sd=0.3848
所以次级绕组采用4股0.35mm线并绕
总结,选择EFD-20磁心,初级4股0.4mm线并绕10匝,初级电感量35uh,次级4股0.35mm线并绕12匝.
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