Negative 48 VDC Supply Input Circuit

[mdgtech1]

I am tasked with designing a DC input circuit which receives as its power source, negative 48 VDC. IE, the power source has its positive terminal referenced to Earth GND and the negative terminal is HOT.

Are there any reference docs or advice on where to start?

thanks for any and all advice...

 

[buzzp]

You might think about using a DC-DC converter. I think some of these accept negative supplies. Not sure how much power you need. Or what a "DC Input Circuit" consists of (probably not as important as power requirements).

 

[geekEE]

Giving more details on what this circuit is supposed to do will be the best place to start. Otherwise we're just guessing what you need.

Glenn

 

[mdgtech1]

sure,
a Lorain power source, in an outdoor basestation environment will provide power to a controller I'm tasked to design. The controller itself is very straight forward and I can get everything I need to do with less than 300mA at +5VDC. Where I need help is how to convert the -48VDC to any VDC thats (+). The input power is positive referenced to earth gnd. I will look into some DC/DC converters and appreciate that feedback. I am wondering if there is a simple diode protection circuit or any "gotcha's" out there to watch for.
thanks

 

[geekEE]

Make sure the DC-DC converters are isolated.

You should be ok as long as the DC-DC converter is the only connection between the -48VDC and +5VDC circuits. If there is any other connection (digital I/O, etc) between the circuits then you need to provide some sort of conversion at those points as well. The type of conversion will depend on the type of signal.

Glenn

 

[itsmoked]

Do a google search for what you need. I've seen, in the past, several DC-DCs specifically for -48V input power. Some makers have product lines for that.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[benta]

Such converters are available off-the-shelf. -48 VDC is standard for telecom equipment.

Benta.