I am trying to develop a bench power supply. Now, before going on, I do realize that there are really cheap commercial ones available. I have two. I want to develop one my self.
The way I have thought it up: Step down transformer (not center tapped or anything). This will yield a small AC voltage and give me isolation.
I will then rectify that AC into DC and have a smoothing cap to deal with the ripple caused by the loading.
With the transformer, I get isolation. This means that my power supply will be floating. At this point in my design, I am trying to nail the basics down so I am not focusing on capacitive coupling to Earth or Resistive coupling etc.
So with a floating power supply, lets say I am trying to get rectified 15V out. This means that I will have 15VDC from DC Vin to DC Vreturn. But this 15V can be sitting way up in air (since its floating).
Now, when I, for instance, will probe it with a o-scope, I will effectively reference the return of my floating+isolated power supply to Earth (due to o-scope ground connection) and that will essentially bring my 15VDC to earth level from high up "in the air"
The issue: Will o-scope probing any of this design and/or any circuit that will be powered with this power design, cause sparks to fly everywhere? I wont think it would but I dont have a lot of experience with AC rectification (but read up on tons of stuff and simulated my power supply design to my hearts content). DC voltage, I can relatively handle that better
My main point is safety becaz I want to live!.
This maybe a later point to tackle (referring to an earlier statement): I have isolation via step down (non-center-tapped) transformer. Why cant I take a separate earth connection and tie that to the DC return of my power supply (via 100K or 1MEG resistor) and effectively reference my floating power supply to Earth. This way it wont be floating in "mid air"
Thanks for looking guys!