Hi All,
I want to design an auxiliary dc/dc converter up to 12W (no isolation is a must).
The input voltage range is around 15-80V, and the outputs are 3.3V (regulated) and 5V.
Is there any good and quick rule of thumb to estimate which one of the 2 topologies is more suitable for this case?
I guess that it's related to the conversion ratio of Vin to Vout. The power fits to both topologies.

Thanks.

 

What do you mean "no isolation is a must"? Why would it be a "must"?
In general, if you don't need isolation, then you don't need a flyback design.
Here's a short discussion of the various topologies.

 

Hi,

Buck is much simpler. You can get something up and running without using a transformer for one thing.

 

What do you mean "no isolation is a must"? Why would it be a "must"?
In general, if you don't need isolation, then you don't need a flyback design.
Here's a short discussion of the various topologies.

I am familiar pretty well with those 2 topologies.
I'm not familiar with a non-isolated step down topology with multiple outputs.
That's why I asked about flyback. Moreover, buck converter at high in-out voltage ratio will be non-efficient, due to
high voltage on the inductor, which cause large current ripple into the output caps. The solution is to increase the inductance, but then
it also increases the cost and area.