what are the differences between buck-boost and flyabck smps

[savage67]

the switchers of them have the different current ratio for a same output power.
is it correct

 

[mateuko]

Re: what are the differences between buck-boost and flyabck

That's correct. Required current capabilities of power switch are different for buck and boost/flyback at the same power. The flyback converter requires the strongest transistor out of these three topologies.

 

[svhb]

Re: what are the differences between buck-boost and flyabck

On the circuits I have in mind for a buck-boost (not a single buck or single boost), and a flyback, I can not think of significant differences in currents if you take into account similar input and output voltages.

The flyback normally has a transformer to store the energy and has a secondary to release the energy to the output capacitor. The buck-boost just uses a simple solenoid to store the energy. The flyback has the advantage that is uses a transformer, so more freedom is available to adjudt the output voltage level (turn ratio), but a transformer is more complex and more expensive than a single solenoid.

From switch-stress point of view, they are the same. All energy must be delivered during the on-time of the switch to the solenoid or tranformer.

 

[christus02]

Re: what are the differences between buck-boost and flyabck

The above given answers are right.

But.. I would like to give a detailed explanation...

1.
Buck-boost converter uses a inductor to store the current and then discharges through the capacitor..(when the switching circuit ONs or OFFs)

Flyback converter uses a transformer(step-up or isolation transformer in general) to supply the load.

2.
Buck boost can operate in 2 modes -- a. as buck mode and
b. as boost mode

Flyback converter does'nt work so..

3.
Buck-boost converter is used for low power operations.

Flyback converter is used for high power operations as in CRT , TV ,etc..(since it uses a step-up transformer)