Topic 9Main contentsLast lecture reviewBasic of Magnetic Forwad Converter
Main contents • Last lecture review • Basic of Magnetic • Forwad Converter Topic 9
1Flyback ConvertersDuring the ton period:the output load is entirelysupplied by the energy storedin the output capacitor.i2=ip=0i(t)=im(t)= Im(O)o<t<ton-(N,/N2)VΦI = Im = I(O)+(10-9)Φ(0)n1D
During the ton period: the output load is entirely supplied by the energy stored in the output capacitor. (10 −9) on m 1 m m L V I ˆ = I ˆ = I (0) + d t o t ton Lm V i1 (t) = im (t) = Im (0) + d t i2 = iD = 0 i D v1 Φ Φ(0) -(N1/N2)Vo Vd toff ton Io t t t D C R T N1 :N2 i1 + Vd - + Vo - i2 + v1 - - v2 + 1 Flyback Converters
During the toff period:the output load is entirely suppliedVaby the energy stored in thetransformer.im(t)= l21Lm(ton<t<T)(10-11)iz(t)=ip(t)(tNi(t) =0-(N/N2)VΦTheflybacktransformerisΦ(0)actually a two-winding inductor,whichstoresandtransfersDenergy
1 (10−11) N2 N L N2 N V ( ) i2 (t) =iD (t) = 1 im (t) (ton t Ts ) m o im (t) = I ˆ − (t − t ) m on i v1 Φ Φ(0) -(N1/N2)Vo Vd toff ton t t D D Io energy. t C R T i1 + Vd - + Vo - i2 N1 :N2 + v1 - - v2 + During the toff period: the output load is entirely supplied by the energy stored in the transformer. i1 (t) =0 The flyback transformer is actually a two-winding inductor, which stores and transfers
In the continuous-conduction modeNi + △i,=0VdVDVa1-DN0A1N2DV.N2(10 -7)VdN, 1- D-(N,/N2)V。dEq. 10-7 shows the dependence (0)of the voltage-ratio on the duty-1ratio D is identical to that in theDBuck-Boost converter
(10 −7) Vd N1 1− D ratio D is identical to that in the i v1 Eq. 10-7 shows the dependence Φ(0) of the voltage-ratio on the duty- Φ -(N /N1 2 )Vo Vd off ton t t t D C R T i1 + Vd - + Vo - i2 N1:N2 + v1 - - v2 + In the continuous-conduction mode i1 + ip =0 = Vd 1− D V1 D 2 D Io Buck-Boost converter. t 1 = 0 N N i1 + i2 Vo = N2 D
TVdN2)V+-Nor-toff-(N,/N2)VΦApplication:Φ(0)low powerlevel below50wD
Application: low power level below 50W. iDΦ Φ(0) -(N 1/N 2)Vo v 1 Vdton t off Io ttt D C R T i 1 +Vd - +Voi2 N1 :N2 +v1 - -v 2+ o d d o N V N NN ) V ) V 12 D , peak 21 T , peak = V + ( V = V + (