dc to dc ATX power supply

Kaizer Soze · 10-07-1999, 12:26 AM

I purchased a great baby atx mb with a/v but the board accepts atx power only.I've seen several postings as well as web sites displaying dc to dc power supplies, however it seems the power supplies are AT only. Does anyone have any information on the existence of such a device.

snakebite · 10-07-1999, 01:37 AM

If you purchased or built a standard AT power supply, you should be able to use a simple circuit based on an LM317 regulator to get your 3.3 volts.

inmytree · 10-07-1999, 09:26 PM

oh for ****s sake, get over DC-DC and just buy an inverter..

snakebite · 10-08-1999, 02:01 AM

Dude, inverters are lame, dc - dc's are cool

sj · 10-11-1999, 09:33 PM

Check rather these National ready built dc/dc power suplies.
This is 5v/5A, you need just small extra to get it work from 8->volts. They have also 3.3 sets and are typically $20 as ready built.
sj

sj · 10-11-1999, 09:34 PM

Oo-ops. Link is here:
http://www.national.com/pf/LM/LM2679.html

spud42 · 10-17-1999, 04:43 PM

check your m/b power req first.. i got a gigabyte ga5smm board with onboard sound and vid..according to the manual it doesnt use the 3.3volts?? will try to lift 3.3v wires from connector and see if it still works and post result here..... btw does anyone know what to hold the power good signal at??

jjohnson · 10-17-1999, 08:51 PM

Power good usually is held at +5V. Use a 470 ohm resistor for good measure. Technically this is supposed to be held low and then high for a certain period of time, but most boards don't care about the timing.

--Jason
http://jump.to/m2pc

jjohnson · 10-17-1999, 08:54 PM

I wouldn't recommend using an LM317 regulator to get the +3.3V. It's not DC-DC in the sense that it is a linear regulator and not a switching type and will generate much more heat as a result. Most boards do use the +3.3V to generate the CPU core voltage and it also appears on the PCI and AGP bus, plus some SDRAM use +3.3V instead of +5V

--Jason
http://jump.to/m2pc

snakebite · 10-18-1999, 02:28 AM

Good point, I wasnt sure how much current was needed (and Im still not) anyway with a slightly higher component count, you could use the MAX788 I think they will handle approx 5A.

jjohnson · 10-21-1999, 07:47 PM

I am currently using a MAX788 in my prototype ATX DC-DC PSU. I should have the first supply up and running this weekend. I received the final parts needed to complete it yesterday. Once it's built, tested, and running, I'll let you know how things went. After that I plan to have professional PCBs etched & drilled. Check my website for more info in a few weeks.

--Jason
http://jump.to/m2pc