[sdiy] Re: Power Supply PCB

mike ruberto somnium7 at gmail.com
Wed Mar 5 07:28:23 CET 2008

Here is the preliminary schematic.

As you can see, the PCB can be used alone as a basic power supply but
can be used as the core to a larger system.
I think of it more as a building block.

The part in green is the actual PCB circuitry. In yellow is a
schematic of how the diodes to set the output voltage may be combined
on the PCB. Obviously, unneeded positions can be jumpered or left
open. The zener diode can have another zener in parallel to further
lower the impedance. There is quite a bit of flexibility here to aid
in setting the correct voltage or achieving the desired impedance.

Voltage calculation is accomplished with this:
Vz + 1.25 + drop

Where Vz is the zener voltage. 1.25 is the LM317 reference and drop is
the combined drop of any LEDs or diodes in series with the zener.

I'll work up some more documentation if it is required. Getting late
for me now though so time for bed.


On Tue, Mar 4, 2008 at 3:08 PM, mike ruberto <somnium7 at gmail.com> wrote:
> From my recent experience with the PSU of Doom I have designed a new
>  PSU unit which is the functional equivalent of that one with my added
>  upgrades. I am designing the PCB now and it's almost finished.
>  This unit will be capable of any split-rail voltage via programming
>  with zener diodes. Output voltage can be calculated as Vz + 1.25 + 0.6
>  and I included options to use extra diodes or LEDs to help getting the
>  target voltage easier.
>  The PSU can be built with a pass transistor stage for a maximum
>  current up to 4 amps. Or the 3 pin regulator can be used on it's own
>  for a maximum of 1.5A.
>  I attempted to incorporate all the "quiet running" practices I
>  researched online including separate ground paths for the regulator
>  adjustment network.
>  I am going to run PCBs of this for myself. If there is any interest I
>  can assemble a group-buy on these PCBs.
>  This time I will play it smart though and get a test run of PCBs made
>  before the main order.
>  As before, let me know off list if you are interested. I'll try to
>  post some technical details later on.
>  Mike

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