In development DIY DC-DC power supply with shutdown ctrl included (With a microctrl)

PTCruiser · 02-03-2003, 08:32 AM

Power :
http://www.just-married.ch/pt/dcdc/S...ints_Power.pdf
Supply 8-17V DC
+5V 5A (6A max) MAX787 freesample
+3.3V 5A (6A max) MAX788 freesample
+12V 1.8 A new design done with webbench
+5V stby 1A (linear regulator)
Fuse on board

Microctrleur PIC 16F84 4Mhz for the logic part
http://www.just-married.ch/pt/dcdc/S...ints_logic.pdf

- PowerGood
- SoftOn
- ATX Swicth with a relay (= power button of your case)
- Thermal switch (60°C cut of)
- 5V Stby Switch
- Enable/Disable power supply
- led de status (ON, STBY...)
- Input 12V accessory

Can be upgraded

5 I/O of the pic are free to drive more relay, temperature sensor…

Cost ~70-80 $

All part from www.farnell.fr except T6… (farnell=newark)
I will post the part n°...

All design made with protel

160x46 mmm

I will do the prototype + testing this month I hope...

Source Protel:
http://www.just-married.ch/pt/dcdc/DCDC_ProtelDXP.zip
http://www.just-married.ch/pt/dcdc/DCDC_Protel99.zip

jol · 02-03-2003, 08:45 AM

no -5 or -12?

PTCruiser · 02-03-2003, 08:47 AM

No...

It's specific to the EPIA motherboard (my own need...)

jol · 02-03-2003, 10:21 AM

heh ok

phil.45 · 02-03-2003, 11:16 AM

Quote:

Originally posted by jol
no -5 or -12?

-12v and -5v can be easily made on a tiny daughterboard if you need them using one Maxim chip and and 3 support components. This is what I had to do in my system to get my serial port working as the PSU i made only supplies 5v and 12v (Cause I didnt think I would use the serial port - Now Im using TWO!).

PTCruiser · 02-03-2003, 03:12 PM

If you want you can mdify the design (you'll need protel) to add the -5V and -12V

As I use a T6 you can simply use it to generate the -5V and -12V
like on the original sproogy...

http://upload.nowherenews.com/files/20232952.jpeg

But on the mini-itx mainboard you don't need the negative voltage anymore...

And +12V is very usefull for the 3.5" hardisk (here I should get 1.8A cst)

netsuo · 02-04-2003, 02:52 AM

Switzerland in da place !

mp3hombre · 02-04-2003, 07:46 PM

Great idea!

But according to the schematics, T301 has one of its windings grounded. I've never seen such a thing before.

digitallexus · 02-05-2003, 03:10 AM

You mention this is being designed for the Epia. Is it for the Epia-M?

Keep in mind the compatiblity problems we've found associated with he OPUS and the Sproggy's. What are you doing different to make it compatible?

PTCruiser · 02-05-2003, 03:10 AM

Quote:

But according to the schematics, T301 has one of its windings grounded. I've never seen such a thing before

Well I made a redisgn of the +12V with webbench:

http://www.just-married.ch/pt/dcdc/12V_sch.JPG
http://www.just-married.ch/pt/dcdc/12V_part.JPG

PCB will be done here:
http://www.olimex.com/pcb/index.html

with Solder mask layer,finish reflowed SnPb, white component mark, NC drill...21$ for 2 pcb!

Sorry I will upload again the logic part the pdf is a blank page...

http://www.just-married.ch/pt/dcdc/...rints_logic.pdf

PTCruiser · 02-05-2003, 03:14 AM

@ digitallexus: I heard this problem... (I have a EPIA-M)
I hope that it comme from the powergood signal of the sproogy that comes too early...(but i am not sure...)

Sa I do the powergood signal with the PIC I can set a bigger wait time...

zootjeff · 02-05-2003, 01:09 PM

Did you take a look a the output ripple from webbench? It lookes like your caps are very small. What value caps did you use for the input and output and what is their rated ESR? I guess if you looked at the output on an AC coupled O-scope, you could make sure your not violating the ripple specs..

PTCruiser · 02-05-2003, 03:16 PM

For the +12V line:

Cin 1500uF (0.029 ohm)
Cout 2200uF (0.018 ohm)

Panasonic low ESR cap...

I think it's big enough?

For the +5V & + 3V exactly the same that on the sproogy original design (= maxim typical application)

And yes I did make a simulation on the output ripple from webbench

Thanks for the comments zootjeff...I really liked your design!

mp3hombre · 02-05-2003, 05:13 PM

Will you make the PIC software available to the public?

zootjeff · 02-06-2003, 01:31 AM

Quote:

Originally posted by PTCruiser
For the +12V line:

Cin 1500uF (0.029 ohm)
Cout 2200uF (0.018 ohm)

Panasonic low ESR cap...

I think it's big enough?

Thanks for the comments zootjeff...I really liked your design!

Yaa that looks good for the + 12 I do question the sproggy though.. I have seen a bunch of people put generic ESR caps on their designs and there is no real way to test the output ripple with out an oscope. The output and input cap of the 3.3 and 5 should also have about the same ESR rating.