That's what I meant..
That's sort of what I thought would happen if you wanted to maintain a ground/neutral connection.
May as well do it so you can.
Embrace the 'iron'. You can use the full/half bridge directly to control output current and provide your isolation. There is no need to generate an intermediary DC supply and then add a buck converter you can do it all in one go.
I've had a fiddle with a half bridge using average current mode control and it's looking funky.
It might get messy. I haven't got my brane screwed in yet so I can't draw what you've got.... However boosting neg to pos is going to place extra voltage stress on that part of your converter and its control electronics are going to be referenced to a different point which may well be going up and down.
Spikes are common in simulation. Sometimes it's because you've done something stupid. Sometimes it's because there are two answers, the one you want and the one that has a big spike. Some series and or parallel resistance in inductors can help. However, in this case, it is likely that......
Yes, the node you mention can and will cause stress. Try adding a capacitor from that end of the boost inductor to circuit ground. You'll need one in real life as well. By all means, send me a copy of what you have got. There is an e-mail icon on the front page of my webshite....
Ideal switches are nice..... (ideal everything) stick with them until it's working the way you expect. Then you might start adding 'real' stuff.
Later
DNA