UCC28600 Isolated DC-DC

Hi John,

I have asked one of applications engineers to respond to this post.

Regards

Peter

A simple way to force the calculator to use a DC input voltage is to divide your DC range by SQRT(2) and input that result into the VAC min and max cells; so for athe 18V minimum you should iput 12.7 Vac and for the 35V maximum you should input 24.75 Vac.

Admittedly, at this point the calculator starts to gag with the input capacitor calculation because it was written assuming a 47 Hz line frequency and the result is the large input capacitor required to maintain a reasonalble minimum bulk input. I'm guessing the DC input that you are using is a relatively stiff rail and you will actually use an input capacitor suited to your DC application, but the calculator is pretty set in its AC line frequency ways so you need to trick it... I would fool the calculator by putting in something like 1% or less in the "Vbulk ripple, %pp" cell and then input the "Required INPUT CAPACITOR" result (that big red value) into the "Actual Input Capacitor Used" cell so that you are forcing the power stage to design at a minimum input rail that is only slightly less than your minimum line voltage of 18 V.

At this point the calculator should proceed as normal, now that it has a minimum bulk rail that it can deal with to design the power stage around.

I hope this helps.