I almost finish with my Half-Bridge SMPS design. I'm now designing the output voltage feedback to the controller stage.
The controller stage drives both MOSFET transistor through an isolation transformer and the power supply for the controller stage is a separate 12V-50Hz transformer so there is a complete isolation between the controller stage and 220V power line.
Now my question is: Do I need to isolate the output voltage feedback using opto-isolators? I know I have to isolate from the 220V power line because of it's high voltage but do I need to do it for my output voltage? The output is 35V 10A max.
The book Power Supply Cookbook from Marty Brown explains I need isolation from the output stage to the control stage but doesn't explain why.
Here is a simple block diagram where you can see the control stage is completely isolated. In my case I can't power the control circuit from the same secondary because voltage goes from 1V to 35V.