Transformer in flyback DC-DC converter
A fly-back DC/DC converter is a SMPS or Switch Mode Power Supply. Basically, this is a type of power supply, based on the generation of power pulses, which are applied to a storage power element. There are many types that can be implemented on this basis.

In this case, the power pulses are applied to the primary winding of a transformer (flyback transformer). The variable current generated is transferred to the secondary of the transformer, where the rectified and filtered.

Why so complicated assembly for a power supply? Because this way of working provides better performance than a linear regulator, among other features.

Append: here is a basic block diagram for the system. The PV module feeds the power Switch, wich applies a pulsed DC to the fly-back transformer. In the secondary of the transformer, the pulsed DC is rectified and filtered.



If your question is: why use the DC / DC converter, instead of directly connecting the PV module? The answer is that the PV module does not provide a regulated output, then inserting a DC / DC converter, not only I get a very good output regulation, but also can obtain different voltage levels.