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Thread: Why are DC-DC power supplied so expensive?

  1. #1
    Low Bitrate
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    Why are DC-DC power supplied so expensive?

    How come it's so expensive to build a DC-DC power supply that can only provide power to a small range of CPUs and to a limited peripherial configuration, while an inverter can power just about any PC configuration for a lot less money?
    I could understand a DC-DC PS costing little more ($10-$50) than an inverter, but it seems that these PS's cost about $100+ more than inverters. Why such a discrepency?

    (ps: just making an observation -- I know nothing of electronics so I'm oblivious to the finer details of building these devices...)

    (pps: I'd be interested in getting the MP3 OnDemand PS product but it's too expensive, I'd rather go with an inverter and deal with the noise...)


  2. #2
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    They really aren't that expensive... The one I use you can get from Arise for $79. It has all the outputs you need for an AT motherboard (+/-5v & +/-12v). Surely if you bought an inverter AND a normal computer power supply, aren't you pretty close to $79? Plus, this thing is so much smaller and compact... Only 5"x2"x3"... Why would *anyone* use an inverter?

    LowLife

    PS I have a link to Arise on my page, if you don't know which one I'm talking about...
    <a href="http://www.sunflower.com/~jahelka/MobileMP3/">My Mobile MP3</a>

  3. #3
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    The PSU i'm building won't cost me much more than 20 (about $30 to those of you over the pond)

  4. #4
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    Will either of you two's PS power a system that includes:

    K6 2-266
    VGA LCD
    SoundCard
    2 hardrives (or 1 hardrive and a zipdrive)
    (plus a CDROM - *brownie points*)





  5. #5
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    mjohnson: I don't know if it would or not. I'm pretty confident that it would work great! You need to add up the current that will be drawn at each voltage and see if it is below the supplied current of the power supply. For example, look on the top of your CD-Rom and see what current it draws at +5v and +12v. Do that for the rest of your components and see what you get. From what you listed, I think it will work fine! I don't however, know what power requirements that VGA LCD screen has...
    The ACE-865V supplies 6A at +5v, 2A at +12v, 0.3A at -5v, and 0.5A at -12v. You probably needn't be concerned about the negative voltages, they are primarily only used on some screwey vid cards, and for some devices that you plug into your serial port.

    tenfoot: I realize that it is way cheap to build your own power supply. The reason I didn't, is because I figure I'm going to be plugging a whole bunch of expensive parts into it (ie. motherboard, hard drive, and whatever else you use.). I would rather have a supply that has all of the safety and protection circuts built in to it. To me its worth the extra money to protect my expensive parts! Also, does the supply you are building have -12v and -5v? This one does...

    Just my 2 cent,
    LowLife

  6. #6
    sj
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    There is on simple answer: demand.
    If there would be more demand, series and competition of building PS would higher and prices lower.
    Just pure economics.

  7. #7
    mda
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    Tenfoot, I'm in the UK too.
    Will your PSU support -5 & -12 volts?
    I guess not by the cost, but would you be able to add these features?


  8. #8
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    mjohnson, the other part of the cost is the components. While you can get some manufactures to send you "samples" of their product, others do not. Some parts you have to buy via the internet and pay shipping, handling, minimum orders, etc. Total truth is sj said "supply and demand." If more competition enters the scene then the price will go down. By the way, I am working on a home based DC-DC solution. I'll post details when it's finished and verified working!

  9. #9
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    I don't know about what the PSU will power cos I haven't build it yet. The components are on order...

    It's based on the ones at www.jarcom.com/inmotion and
    www.mp3uk.freeserve.co.uk

  10. #10
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    My design is based on inmotion's PSU also. I have included the ability to produce +5, +12, -12, -5, and 3.3VDC, just in case I scrap the AT motherboard and go with an ATX. The MAX chips are free from www.maxim-ic.com, and I got the inductors/coils/chokes from Coiltronics as sample items as well. Some more inductors are coming from Gowanda. The rest of the components have totaled a little more than $35 for 2 units ($17.50 each. Some parts I've had lying around or friends have scrounged. All in all, I'd say that $25-$30 would be a close estimate for a home built PSU based on the inmotion design.

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