LM2577: Used as buck-boost

Thank you both for your answers!

I should have been more clear about our application. Also, switching supplies it is not something I feel very comfortable with, so bear with me.

We have an input wich goes from 8 to 16V and we want a 12V output, At first we thought 1A would be enough and we were using an Linear Tec part (LTC3114-1). We had some issues with that part (mainly for the lack of experience with DC-DC converters) and we couldn't reach anywhere near 1A.

Now we are looking for something that could deliver more current (at least 2A) but something easeier, simpler, something like "DC-DC for dummies" :) .

We found this LM2577 based buck-boost converters and they look simple enough to be replicated in our application. I found an schematic for the modules (see attach).

1-Would you say is feasible to reach 2A?

2-How would you chose the components value to do that?

I also found out that what we are looking for is a "SEPIC" and knowing that I found the application PMP7768 that uses an LM5022. That circuit would satisfy our needs but I would prefer a low count parts solution with a LM2577-12 if it is possible.

Thanks again!

Hello,

SEPIC converters can be very complicated to design and parasitics can drastically change the performance of the converter. That being said PMP7768 would be a good starting point for this application. HEre is an app note that goes through the basic operation of a SEPIC converter. I would suggest using the LM5022 over the LM2577 as the LM5022 has a selectable current limit threshold as the LM2577 is a fixed current limit.

The other option is to use the a true buck-boost controller, like the LM25118. This can be a much simpler design as is only requires 1 magnetic which reduces the impact of parasitcs in the design. However the LM25118 will require two MOSFETs and two diodes. This is another good option for a buck-boost controller that should be easier to design than most SEPICs.

Please let me know if you have any questions. 

Thanks,

Garrett