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Thread: 12 volt regulated power supply and compaq dc/dc converter

  1. #11
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    30 amps units, running them in linear mode. the output waveform was pretty much a triangle with a peak of 2 volts (shivers)

  2. #12
    Raw Wave
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    Nov 2009
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    You had me confused - a 34063 in linear mode?

    But you mean the FETs. Why?
    Surely they should be full on-off for SMPS...?
    They'll be blowing due to overheating (over 200W peak?)

  3. #13
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    the 34063 was not outputting a proper waveform. the ideal fet gate drive is a square wave wheras this was a triangle. triangle waves keep the fet in linear mode for far too long causing extreme resistance losses and cause the fet to heat up alot. the heat and current draw cause the fet to fail.

  4. #14
    Raw Wave
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    A-ha!
    And rats!

    You'd expect square, though I haven't looked in detail... Well I have, but across a dozen or so chips.
    I do recall a triangular wave but I thought that was related to the rC charging...
    If it's a low slew rate at high frequency, maybe lower frequency hence a lower "linear" duty-cycle....

    And the last time I looked at these was for a CDI (Capacitive Discharge Ignition) when I realised there were great PSUs that drove (MOS)FETs directly for the 350-500V DC CDI supply. All of a sudden my ideal CDI became a cheap item - $10 to $20 for the PSU, and then $2 for every splug (IgCoil) output and a $few for whatever triggering....
    Then I got a common standard reluctor ignition system that cold-started below 6V and I lost interest....

    My only resurgence was to build my own supply(s) rather than spend many $tens on 5A and higher outputs.... (Have I mentioned suckers that spend $300 - $500 for 20A or 40A dc-dc converters so they can "charge auxiliary batteries properly(sic)"?) (Yes - that mob that buys one or 2 rehoused 5c diodes for $42.)


    I'll keep my eyes open....
    Maybe could integrate or Schmidt the outputs, but surely that isn't needed....?

  5. #15
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    tried 2 schmitt triggered not gates in series, that didnt really work out so well. i think i destroyed that chip anyway......... which is why i bought 3! i think i need to clean up my circuit layout and really double check things, im sure with some love i could get this circuit working.

  6. #16
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    Apr 2010
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    i got some pictures!!!! hopefully they attached. anyways, so this is the laptop supply i used

    http://cgi.ebay.com/Universal-Laptop...item3cb236f9cb

    for 15$ for the adapter, 12$ for the compaq dc/dc (which is only 5$, might as well buy two and save on shipping) and a bits and pieces i had lying around (car usb charger, relay, pnp transistor) i now have a 12 volt 120 watt power supply. it has no features like auto shutdown blah blah blah, but i could stick an arduino on it and replicate all of that in around an hour if i really had my heart set on it. overall, not bad. next up, 48vdc telecom computer power supply and 12 to 48 volt dc/dc converter. this is really fun, i just need a nice board to put my intel p4 on (have like 8 of them but no motherboard ) and ill be set! Name:  SSPX0210.jpg
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  7. #17
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    and now for some numbers!

    so i hooked up the ammeter, and this is what i got. 8 amps during startup, settles down to 6 amps during bios, and once windows has booted and its idling, between 4.9 and 5.1 amps (not bad). now this is including a 10.4 inch datalux screen, so for a total power consumption of 60 watts, not bad at all.

  8. #18
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    Apr 2010
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    alright. so i've been toying around with some new stuff lately. my newest setup involves a 48 volt boost converter from ebay and a 48 volt server power supply. the poor little boost converter was supposedly rated to 120 watts. nope... not at all. i replaced the inductor with the biggest one i had around and it worked nicely enough. it now works with my d845hv motherboard and some old nvidia power sucking video card. its cutting it close though, i want to design my own boost converter soon to take advantage of the server supply. it is capable of 400 watts max. so if i can keep a regulated 48 volts (+- 10 volts) the computer stays happy. ill take some more pictures later on. (fun note, the server power supply fan is like a damn jet engine. when i took it out and pointed it down it started to hover. its also loud as hell, like a vacuum cleaner)

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