I am building a switching power supply with an isolating step-down transformer. Part numbers:
Controller: LT3798 (http://cds.linear.com/docs/en/datasheet/3798fa.pdf)
Transformer: 750312872 (http://katalog.we-online.de/pbs/datasheet/750312872.pdf)
LTspice asc file: http://pastebin.com/XF5KJk3U (warning - this takes a LONG time to simulate)
NOTE: To run this spice simulation you will need to add the transformer spice files. Download them here: http://www.we-online.com/web/en/index.php/download/media/06_passive_components_-_custom_magnetics/pdf_doc_files_1/LTspiceStandardLib.zip
I have the official Spice model for this transformer, which includes saturation behavior, and the system works in simulations, outputting 28V 2A at about 75% efficiency.
However, the transformer datasheet indicates 20-60VDC input, while I am running it at about 160VDC input (rectified mains). Also, the transformer has 1.5kV isolation. I'm going to add input protection (500V varistor, common mode choke, differential mode choke, fuse), but is that enough isolation? I'm worried that there are factors involved here that I don't know about.
The transformer is rated for 25A saturation current, and I'm not exceeding 14A.
So I guess I'm also wondering, why is this transformer rated for 20-60V input when it appears to work for 160V? What determines that?