Non-isolated Driver Design 42V/800mA/35W

DER273 and DER285 are LNKPH buck boost referece designs, and these designs can be easily modified to meet your application.

Also the PIXL spreadsheet of LNKPH Flyback can be used for the LNKPH buck boost application with Vor = Vout.

Thanks for your quick answer.
I also found RDR257. It seems to be slightly different in the schematic, what is the reason for that? Which one should i choose for my design?

RD257 is the buck converter using LNKPH.

What is the criteria for using Buck or Buck-Boost? In my opinion Buck should
be sufficient for european input voltage range but this is also fact in DER285, where Buck-Boost is used??

For the low input and high output voltage application, the buck boost is preferred.

For your application, either buck or buck boost can be used, but the buck boost would be the right topology if you need to meet Class C harmonic current requirement.

The PIXL resuilt of the buck converter is attached for your reference.

Hello Skywalker,

many thanks for that interesting informations and the PIXL results. Therefore it
is clear for me that i will need buck-boost design since class c harmonics is a
must for my application. I didn´t know that this is the difference between the two design variations. Could this information be found anywhere on your homepage? If not, i think this would be interesting for other users, too.
Are there any changes in the PIXL Sheet neccessary, if switching from Buck to Buck-Boost topology?

Attached is the buck boost PIXL result using LNKPH PIXL Flyback spreadsheet with Vor = Vout.

You might want to parallel the winding to minimize the conduction loss.