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Thread: Building ATX DC-DC PS. Got questions...

  1. #1
    Newbie
    Join Date
    Aug 2002
    Posts
    37

    Building ATX DC-DC PS. Got questions...

    Okay... I've been slinking around for a while reading the design threads for DC-DC ATX PS and while I've seen one it doesn't strike me as my best bet. It's been years since I've designed anything and come from only a beginning electronics design background. From what I've been reading I think I know where I'm going with this. It looks like this can be done with a few simple circuits. It seems 4 or 5 people here have built their own DC-DC PS's and I hope to get their input. I decided not to go the TI ISR route due to expense. $27 per IC is a bit much for me. I think I am going to go the MAXIM IC route and it seems they are adequte to give most of my volatages save one and that the 12 Volt regulated line. I had planned to use 2 MC78t12's for the 12volt line but I can't find decent spec sheets on them to find out what the low and hi Voltage In range is.

    Anyway this is my plan:

    Power Good MAX6652
    +5 MAX787
    +3.3 MAX788
    -12 MAX775
    -5 MAX774
    +12 ????????

    Thanks for any input.

  2. #2
    Maximum Bitrate
    Join Date
    Oct 2001
    Location
    Ontario, Canada
    Posts
    845
    there are 3 or so other plans for complete power supplies floating around, at least one of which uses the maxim route (sproggy)... I'd just look into those options before you go into the long road of designing something yourself. It's very complicated and a lot of things have to be taken into consideration.

    Do a search in the forums and look for other DIY (do it yourself) power supplies, also check out some of the retail ones available, they're not so expensive. If your time is money then it's probably worth just buying a retail one (you get warranty too) because you're looking at a lot of hours pouring over plans, buying parts and doing the work to get it together.

    But don't let me discourage you from the DIY route. I was going to do that, but I think I'm relenting because it looks like there are some cheap retail power supplies finally coming out. Additionally the inverter route is working fine for me in the meantime.
    IN DEVELOPMENT -- '96 Mustang, lilliput with PII/450 laptop, custom DC-DC power supply, 60GB; Garmin GPS; 802.11g; compact keyboard, small graphical LCDs, OBDII.

  3. #3
    Maximum Bitrate Raas's Avatar
    Join Date
    Jan 2001
    Location
    The Netherlands
    Posts
    626
    you could use a max1771 for the +12v line

    greetz,
    Raas - The Netherlands
    ME: VIA epia m10000, lilliput 7', opus 150w, 80gb<br>
    GF: IBM Thinkpad 380, ext. 3.5 80gb, 40x4, PB-IR

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