Flyback converters are DC/DCconverters used in AC/DC converters and in DC/DC converters. They convert a DC voltage into a higher or lower DC voltage and galvanically separate both voltages. A transformer, whose magnetic field also serves as an energy store, ensures that the DC voltages are potential-free.
The transformer consists of the primary coil, main or feedback coil and the secondary coil. The main coil is in parallel with the primary coil. A transistor or thyristor acts as a clocked switch and converts the DC voltage into a pulsed AC voltage, which is applied to the primary side of the transformer.
In terms of construction, flyback converters consist of an electronic switching element on the input side and the primary side of the transformer. On the secondary side, a diode provides rectification and a capacitor, which is in parallel with the load on the output side, provides smoothing.
The functional sequence takes place in two phases. In the first phase, the switch on the input side is switched on, so that the voltage reaches the primary side of the transformer, where a magnetic field is built up. This phase is called the conducting phase. At the same time, the capacitance on the output side discharges and releases its charge to the load. In the following blocking phase, the semiconductor switch opens and the current generated by the built-up magnetic field discharges through the primary coil and is transformed into the secondary coil and then smoothed by a capacitor.
Flyback converters are mainly used in switched- mode power supplies with low power.