Re: dc/dc startup

On Tue, 14 Jan 2025 10:19:01 -0500 (EST), Martin Rid
<martin_riddle@verison.net> wrote:

john larkin <JL@gct.com> Wrote in message:r

https://www.dropbox.com/scl/fi/3hyvmc3mkvhrk6rc8dt72/P970_DC-DC.jpg?rlkey=npgerceq4t191hnjfd0907v6u&raw=1That makes two isolated 56-volt power supplies. But  the problem ishow to start it up.I could just slam on the square wave drives and let the TI chipcurrent limit until the caps charge up. That might work.I was thiking I could start the two half-bridges with in-phase squarewaves and then slowly slide them out to 180 degrees. My FPGA kidscould do that. That would be a nuisance to Spice.We did a similar supply a while back with discrete fets, no currentlimits. Startup made 300 amp spikes that made all sorts of problems.

>
Yea, software softstart.
>
Cheers

I think the sliding square wave thing will work, but I have sceptics.

So how can I Spice two 200 KHz square waves that start in phase and
slowly crawl to 180 degrees apart? Over a second maybe.