+- 30V from two dual +-15 supplies?

Valverine · 1st August 2008, 08:22 PM

Greetings,

I have two surplus DC regulated power supplies; each of them has dual outputs of +-15V. I need one +-30V supply. I'm thinking about the following. In each PS tie the 0s of each output, this should give two supplies: +30 and -30, depending on what will be further referenced as 0. Then tie the 0s of these supplies to obtain +-30V PS.

Are there any caveats in this arrangement?

Thanks!

richie00boy · 1st August 2008, 09:17 PM

Slightly confused by your words, but basically you need to connect the supplies in series with each other - negative of the 'upper' one to positive of the 'lower' one then this junction becomes your 0V poiint. But be sure to see first if any of the outputs is connected to earth. If it is then you can't do this as you will end up shorting one of the sides.

Valverine · 1st August 2008, 09:59 PM

OK, thanks!

Valverine · 4th August 2008, 07:09 PM

Hi richie00boy,

I managed to find the schematics of the outputs. It shows that the +/-15 are connected sharing a common return, so I can obtain 30V straight from +out and -out. So can I connect two such supplies in series for +/-30V?

Thanks!

richie00boy · 4th August 2008, 08:15 PM

Need to the the whole schematic! My concern is that COM terminal, it seems to be possibly connected to your +15 0 -15V midpoint. If this is then earthed through the case there may be problems connecting two supplies in series.

Valverine · 4th August 2008, 08:31 PM

Hi richie00boy,

This is the full schematics, it doesn't look like the COM is earthed.

Thanks!

woody · 4th August 2008, 08:43 PM

As Richie pointed out it depends on if the common 0 terminal
is floating or connected to earth. When you first hook these
supplies in seriese you might make this connection through
a 1/2w 10ohm resistor or a 1/2A fuse just to be safe.

1st August 2008, 08:22 PM	#1
Valverine diyAudio Member Join Date: Feb 2004 Location: Silicon Valley	+- 30V from two dual +-15 supplies? Greetings, I have two surplus DC regulated power supplies; each of them has dual outputs of +-15V. I need one +-30V supply. I'm thinking about the following. In each PS tie the 0s of each output, this should give two supplies: +30 and -30, depending on what will be further referenced as 0. Then tie the 0s of these supplies to obtain +-30V PS. Are there any caveats in this arrangement? Thanks!

1st August 2008, 09:17 PM	#2
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	Slightly confused by your words, but basically you need to connect the supplies in series with each other - negative of the 'upper' one to positive of the 'lower' one then this junction becomes your 0V poiint. But be sure to see first if any of the outputs is connected to earth. If it is then you can't do this as you will end up shorting one of the sides. __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more

4th August 2008, 08:15 PM	#5
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	Need to the the whole schematic! My concern is that COM terminal, it seems to be possibly connected to your +15 0 -15V midpoint. If this is then earthed through the case there may be problems connecting two supplies in series. __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more

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1st August 2008, 09:59 PM	#3
Valverine diyAudio Member Join Date: Feb 2004 Location: Silicon Valley	OK, thanks!

4th August 2008, 08:43 PM	#7
woody diyAudio Member Join Date: Jan 2002 Location: Tyrone Ga. U.S.A.	As Richie pointed out it depends on if the common 0 terminal is floating or connected to earth. When you first hook these supplies in seriese you might make this connection through a 1/2w 10ohm resistor or a 1/2A fuse just to be safe.

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