Lab Power Supply Current Limiting Q

Wynand · 21st September 2005, 01:10 PM

I'm currently designing a Lab Power Supply to use for various Audio Projects.

I'm using a PC Power supply for 5 12 -5 -12 Volts for a beginning but I want the +and- 0-35v Supply to be the heart of it.

I've decided to use the LM338 T0-3 as my positive voltage regulator.
It'll also be used for the current limiting (5A should be enough limiting?)

My problem is.... do I need a current limiting circuit on the negative supply line aswell or does all the current come from the positive side(what happens at GND in respect to -V)

Wynand · 21st September 2005, 01:21 PM

Heres a pic to show what I dont understand

ctardi · 22nd September 2005, 03:08 AM

Don't quote me on this, but i think it will work with only + Limited.

Nordic · 23rd September 2005, 06:27 PM

Wynand if you do manage to pull it off gimme a shout....
I'd be interested in the setup.... have a few PSU's I can pilage for parts...

TwoSpoons · 27th September 2005, 10:44 PM

You DO need your current limit in both + and - supply. It is quite possible to pull current from GND to V- without any current from V+.

Proof:
Connect light bulb from GND to V-. Does it glow? Of course it does!

21st September 2005, 01:10 PM	#1
Wynand diyAudio Member Join Date: Mar 2005 Location: Cape Town	Lab Power Supply Current Limiting Q I'm currently designing a Lab Power Supply to use for various Audio Projects. I'm using a PC Power supply for 5 12 -5 -12 Volts for a beginning but I want the +and- 0-35v Supply to be the heart of it. I've decided to use the LM338 T0-3 as my positive voltage regulator. It'll also be used for the current limiting (5A should be enough limiting?) My problem is.... do I need a current limiting circuit on the negative supply line aswell or does all the current come from the positive side(what happens at GND in respect to -V)

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22nd September 2005, 03:08 AM	#3
ctardi diyAudio Member Join Date: May 2005 Location: Maple Ridge	Don't quote me on this, but i think it will work with only + Limited.

23rd September 2005, 06:27 PM	#4
Nordic diyAudio Member Join Date: Sep 2005	Wynand if you do manage to pull it off gimme a shout.... I'd be interested in the setup.... have a few PSU's I can pilage for parts...

27th September 2005, 10:44 PM	#5
TwoSpoons diyAudio Member Join Date: Oct 2004	You DO need your current limit in both + and - supply. It is quite possible to pull current from GND to V- without any current from V+. Proof: Connect light bulb from GND to V-. Does it glow? Of course it does!