Re: 120VAC to -48VDC?
Hi,
When converting from one voltage level to another, a PSU is required. In your case, the internal 48Vdc PSU will be one and the external 120Vac to 48Vdc is another.
-48Vdc is very common in telecommunication environment.
When you know current consumption at 48Vdc, find a PSU [Off Shelf] which has isolation built into it, which will avoid ground loops later. Since, it is connected to a router, i assume the connecting ports are isolated. If they are not so, it will create ground loops and spoil the weaker circuitry.
what type of battery are you planning to charge from the 120Vac PSU?
jeyaraman