Difference between power transformers and flybacks?

[owin]

I'm confused, what is the physical difference between a power transformer and a flyback transformer?

Power transformers generally have stacked primary and secondary windings on a iron or ferrite core. Flybacks generally have the windings on opposing sides of a square ferrite core or are wound coaxially.

But I don't understand why their fundamental operation isn't the same? or are they the same.

[Grandchuck]

Fundamentally, they are the same.  In practice, due to differences in frequency, they use different core materials.

[freda]

The main difference about a flyback, is that it doesn't transfer energy to the secondary continuously. A pulse current charges the magnetic
field in the core, then when it stops and collapses (and resets the core), only then does the secondary coil move current into the load.
Thus the core needs to build to a significant magnetic field. This very high current pulse in the primary is bad for power factor, when
drawn from a AC supply. Of course this must be done at a high speed,
not at 50/60Hz of an old iron transformer

[magic]

Fundamentally, they are the same.  In practice, due to differences in frequency, they use different core materials.

Not only materials, but also their size is much smaller because high frequency operation (tens of kHz usually) allows flybacks to have lower primary inductance. Connecting a flyback directly to mains would result in huge magnetizing current and immediate destruction of the primary, because of the low inductance.

And they are operated differently too. In an ordinary transformer, the magnetizing current is at best tolerated as an annoying but unavoidable side effect of transformer operation. With flyback, the whole energy transfer occurs by means of repeated magnetization and demagnetization of the core. This two-step operation is how flyback converters can produce almost arbitrary output voltage from arbitrary input voltage, with no regard for turns ratio of the transformer (which still works the usual way).