Topic 8Main contents Flyback ConverterBasic of MagneticForwad ConverterHalf-bridge Converter
Main contents • Flyback Converter • Basic of Magnetic • Forwad Converter • Half-bridge Converter Topic 8
2FlybackConverters1 Converter CircuitDRu14Buck-boostconverterI.Topology of Fly back converter: is the isolated buck-boost converterDLRHNsiL
2 Flyback Converters 1 Converter Circuit Buck-boost converter Topology of Fly back converter: is the isolated buck-boost converter Np s Ns P
ToutUnder the conditionof Np=NsVbeOnstateDRfmax大1YinNpNs-ifmaxiu118ioILfmin'Offstate-LfmaxiDDLminVVLVoNSTitsCLof1T
4 Power Electronics Off state On state Np Ns Np Ns Under the condition of NP=Ns P s P s
2 Operation principleiiN:N,12+D(1) During the ton period:turning on the transistor at t=0.VaV,=V. V (N N )V α Thediode D becomes reverseV14biased. The transformer coreflux Φ increases linearly fromVdits initial value Φ(O)on(t) =d(0) +血 -(N,/N2)V。(0 <t<ton)NiΦ(0)(10-1)IVd= d(ton) = d(0)(10 -2)DN
2 Operation principle 1 (10 −2) on on N (0 t ton ) (10 −1) V ˆ= (t ) = (0) + Vd t (t) =(0) + d t N1 (1) During the ton period: turning on the transistor at t=0, 1 d 2 2 1 d v =V → V =(N /N )V . The diode D becomes reverse biased. The transformer core flux Φ increases linearly from its initial value Φ(0). Φ Φ(0) i D -(N1/N2)Vo Vd off ton t Io t t t D C R T N1 :N2 i1 + Vd - v1 + Vo - i2
During the ton period:Vathe output load is entirelysupplied by the energy storedin the output capacitorV1i2=ip=0i(t)=im(t)= Im(O) -o<t<ton-(N,/N2)VΦI. = I, = Im(O)+(10-9)Φ(0)n1D
Du on ring the t 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 D t C R T N1 :N2 i1 + Vd - + Vo - i2 + v1 - - v2 +