Help me solve an issue with power ground in a power supplier design

[jim2010]

Hi, Everyone:
I have a problem when I design a power supplier. In my system, there are two power suppliers, the first one is 120VDC and the seconde one is 12VDC. I have to use 120VDC
as the power supply of a DC/AC converter and a DC/DC converter (generates 12VDC output).
My problem is that I have to use -120VDC as my system ground (in the DC/AC converter, we have to assign this -120VDC as reference point), in that case, this
-120vdc would be connected to the return point of 12vdc. It would create big trouble.

I uploaded my schematic. From the schematic, you can see VDCIN_LOW would be connected to Signal ground. I hope to know how to solve the problem.

Best Regards

Jim

 

[hakeen]

Re: POWER GROUND

What about isolating grounds? You have transfomer already. Then, you have to isolate your controller IC (LNK) cvia e.g. optocoupler.

 

[jim2010]

Re: POWER GROUND

Hi,
Thanks very much. But I think that it is not a good method to isolate two grounds

Jim

 

[karesz]

POWER GROUND

Or its not a good methode to connect signal GND to the incoming negative!? :-(
You will short the symmetrical EMC filrer too...
K.

 

[jim2010]

Re: POWER GROUND

Hi,
Thanks very much. I think that I shouldn't use an isolated DC/DC. I should use non-isolated POWER.

Best Regards