The Flyback Converter University of Colorado （科罗拉多大学反激式变换器）.pdf

The Flyback Converter Lecture notes ECEN4517 ! Derivation of the flyback converter: a transformer-isolated version of the buck-boost converter ! Typical waveforms, and derivation of M(D) = V/ V g ! Flyback transformer design considerations ! Voltage clamp snubber Derivation of the flyback converter The flyback converter is based on the buck-boost converter. Its derivation is illustrated in Fig. 1. Figure 1(a) depicts the basic buck-boost converter, with the switch realized using a MOSFET and diode. In Fig. 1(b), the inductor winding is constructed using two wires, with a 1:1 turns ratio. The basic function of the inductor is unchanged, and the parallel windings are equivalent to a single winding constructed of larger wire. In Fig. 1(c), the connections between the two windings are broken. One winding is used while the transistor Q1 conducts, while the other winding is used when diode D1 conducts. The total current in the two windings is unchanged from the circuit of Fig. 1(b); however, the a) b) Q1 D1 Q1 D1 – – 1:1 V + L V V + V g – g –