# dual power supply design

Discussion in 'Electronic Basics' started by panfilero, Mar 12, 2009.

1. ### panfileroGuest

Hello,

does anyone know if there's any way to design a simple low power dual
power supply? The result should be able to swing between -2V and 2V
(for example, the values are not important just giving an idea of the
range) and supply around.... 200mA (again just an idea... around here
somewhere).

The output of the power supply should (ideally) consist of two wires
that I can swing between +/- 2V. I'm open to any type of control...
I'm guessing it will end up being a pot, although voltage control or
current control would be nice... however, that is not really what I'm
trying to figure out right now.

I'm just wondering if someone can point me in the right direction
here... I'm having a hard time trying to figure out where to begin
with this design.

much thanks!

2. ### Guest

As always, you need to state what you are starting with, and your
specific goal. Yes, most things are possible, but the means to the
end depends on the specifics.

3. ### Kirk JohnsonGuest

Maybe give this a try lad

http://www.imagefap.com/image.php?id=1988478267

Always works wonders for me!

Kirk Johnson
"Stretching Specialist"

4. ### neon

1,325
0
Oct 21, 2006
use a simple lm317 just bias it off to -5v. YOU CLOULD expand and add a pwm but that is not simple.

5. ### stanGuest

1) Find a design for a power supply of around four to five volts. With
a centre tap.
2) And there are other circuits that can be arranged from a
transformer without a centre tap that can also provide plus and minus
supplies from the same winding. With a 'virtual' centre tap or zero
voltage point.
3) A pot placed across the two outputs can be adjusted to anywhere
from plus 2 to to minus 2 volts; relative to the centre tap of item
(1) or the created zero of item (2).
4) For two separate outputs use two separate pots arranged thus.
As a guess you prob. need power supplies providing an amp or more and
then 'sink' some of it in the pots.
Depending on whether the 200 m/a is a steady or varying load?
All depends what you are trying design/do!

6. ### Ross HerbertGuest

:Hello,
:
:does anyone know if there's any way to design a simple low power dual
ower supply? The result should be able to swing between -2V and 2V
for example, the values are not important just giving an idea of the
:range) and supply around.... 200mA (again just an idea... around here
:somewhere).
:
:The output of the power supply should (ideally) consist of two wires
:that I can swing between +/- 2V. I'm open to any type of control...
:I'm guessing it will end up being a pot, although voltage control or
:current control would be nice... however, that is not really what I'm
:trying to figure out right now.
:
:I'm just wondering if someone can point me in the right direction
:here... I'm having a hard time trying to figure out where to begin
:with this design.
:
:much thanks!

I don't know exactly what you hope to achieve by being able to "swing between
-ve and +ve" using "two wires".

One of the output wires has to be the nominal reference or common wire which
means that the other wire must be able to ramp up to some +ve value when
rotating a potentometer in one direction. Alternatively, this wire will also be
able to ramp down to some -ve value by rotating the pot in the other direction.

Is this what you mean?

Usually, a power supply is used for a specific purpose and if it is required to
be voltage adjustable, then its output range is between the value of 0V to some
+ve maximum, OR from 0V to some -ve maximum on another wire which is referenced
to the 0V wire, ie. the output wire can go no lower than 0V referenced to the 0V
or common wire.

7. ### Hope for the HeartlessGuest

How much of a consideration is efficiency, and what power does it need
to run on? Does it produce +2V and -2V at the same time, or do you
need to swing it end to end?

If it's AC, I'd use a transformer to reduce line power to about 10V
peak to peak, center tapped, to ground, rectify it on both sides to get
+5V and -5V, filter to get the ripple down to under a volt and then use
a power op-amp with variable gain off a voltage reference to get the
output voltage.

8. ### Guest

? ISN'T THAT A SONG ?

I AM PROTEUS