Parallel PSU's / General Science and Electronics / Forums

Forums

4hv.org :: Forums :: General Science and Electronics

« Previous topic | Next topic »

Parallel PSU's

1 2 next

Move Thread

LAN_403

cduma

Sat Jul 16 2011, 08:37PM

Registered Member #1822 Joined: Fri Nov 21 2008, 08:04PM
Location:
Posts: 300

I have a need for 60A at 12VDC and I cant afford a single powersupply that would be able to do that. My idea was to pick up a couple of 20A PSU's and run them in parallel. In order to prevent feedback I was going to run the power from each through a diode. I dont expect a very clean signal at all. Any reason due to them being SMPs that would prevent this from working?

Austin the Ozone

Sat Jul 16 2011, 08:51PM

Registered Member #3989 Joined: Thu Jul 07 2011, 05:10PM
Location: In a van down by the river.
Posts: 52

The power supply on my motorhome is 70 amps, you might get lucky on craigslist. I got a 50 amp battery charger that weighs like 40 lbs at a pawn shop for 35 bucks. I got a cheap 110 arc welder for about 50 bucks on craigslist that would probably make a pretty hefty 12 volt power supply. But yes running dc power supplies in parallel works but really unless you need it continuously for hours, one power supply and a car battery for a buffer would probably be fine. The battery smooths the rectified dc out too! What are you building out of curiosity?

cduma

Sat Jul 16 2011, 10:14PM

Registered Member #1822 Joined: Fri Nov 21 2008, 08:04PM
Location:
Posts: 300

Powersupply for a subwoofer.

Austin the Ozone

Sat Jul 16 2011, 10:41PM

Registered Member #3989 Joined: Thu Jul 07 2011, 05:10PM
Location: In a van down by the river.
Posts: 52

I would definatly use a battery in addition to whatever power supply you use for sure, I have fried amps before just running off the psu :(

haxor5354

Sun Jul 17 2011, 06:29AM

Registered Member #2063 Joined: Sat Apr 04 2009, 03:16PM
Location: Toronto
Posts: 352

cduma wrote ...

Powersupply for a subwoofer.

i've taken apart a dozen of white van 5.1 systems, none of the subwoofers used SMPS for power, they all use toroidal transformer.
why? im not quite sure but think they can handle overloads better.

Conundrum

Sun Jul 17 2011, 06:29AM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061

Running SMPS's in parallel can work BUT the outputs have to match within 0.1V or one will feed back into the other and could fry them.

I have also used salvaged >20A rated Schottky diode blocks for this before, find two duals the same and connect the cathodes together. Connect one anode each to a power supply with an inline 20A fuse and all should be well.
The SMPS's should then autosync to the available load and the outputs will combine.

#include "YMMV.h"

-A

cduma

Sun Jul 17 2011, 06:51AM

Registered Member #1822 Joined: Fri Nov 21 2008, 08:04PM
Location:
Posts: 300

My idea to keep the voltages similar was to place a resistor across the 12V lines before the diodes. Im not sure what resistance to shoot for though. Im thinking that they would be <10ohms

Sulaiman

Sun Jul 17 2011, 09:26AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

Many commercial power supplies have the provision for paralleling inbuilt.
If you use 'old school' transformer/rectifier/capacitor supplies of similar power with no feedback then you can parallel them simply with diodes as the source impedances will be similar enough to balance the power.
Once each psu has feedback regulation of it's output then it's not that easy as indeterminate feedback oscillations will occur, mainly due to each psu having a slighlty different feedback loop time constant.

Most high power amplifiers for 12V supply have an internal inverter,
it may be easier to disable the inverter and use a higher voltage/lower current external supply directly to the internal higher-voltage bus.
If not then I too would use a 12V battery as the primary source with a battery charger feeding that.

cduma

Sun Jul 17 2011, 12:00PM

Registered Member #1822 Joined: Fri Nov 21 2008, 08:04PM
Location:
Posts: 300

The problem with using a car battery is that I would like this to be semi-portable for parties and such. Also, 800Watts would drain the battery pretty quick even with a ~20A input

Sulaiman

Sun Jul 17 2011, 03:04PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

60A x 12V x 70% efficiency = 500 W rms .... that's a loud party!
That's also some rather un-portable speakers.
More transportable than portable.
I'm sure you could pick up a mains powered amplifier cheaply.

If you're going to have such high powered speakers
a mains power supply would be relatively small/portable,
unless you're in a field, in which case a portable generator is the answer.

1 2 next

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob