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Power-One power supply mod

Discussion in 'Power Electronics' started by bushtech, Jul 25, 2017.

  1. bushtech

    bushtech

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    Sep 13, 2016
    It has always been a dream to have a decent power supply for my bench. This power supply was gifted to me by a very kind friend. It's a Power-One HCC15-3. It pushes out + and - rails from about 10V to 17V regulated by 2 pots at a very healthy +- 3A. Like this piece of kit.

    How feasible/possible/sensible would it be to turn this into a 0-30V supply or should I just forget it and start from scratch?

    I just don't have the experience/knowledge to make a good decision here.

    Your help will be really appreciated.

    Apologies for the upside down images

    [Mod edited -- imaged fixed]

    20170725_142250.jpg

    20170725_142901.jpg
     
    Last edited by a moderator: Jul 27, 2017
  2. kellys_eye

    kellys_eye

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    Jun 25, 2010
    bushtech likes this.
  3. bushtech

    bushtech

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    Sep 13, 2016
    Thanks a mil kellys_eye.

    I think it's the same as this: https://www.banggood.com/0-30V-2mA-...wer-Supply-DIY-Kit-p-958308.html?rmmds=search

    Which I can get for $5.22. Even better:):)

    Presumably I would need 2 of these to give me + and - rails?

    And then I need to spec a transformer. I see you need 24V and > 90W output. If I do 2 rails presumably I need a transformer with dual 24Vouts that can deliver more than 90W on each out
     
  4. kellys_eye

    kellys_eye

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    Jun 25, 2010
    Yes, your transformer detail requirement is correct.

    If you go ahead and build this power supply, please come back and show us your results :cool:
     
  5. Audioguru

    Audioguru

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    Sep 24, 2016
    The ebay and Bangood power supplies DO NOT WORK (most of the parts are overloaded) and are being replaced with a kit that has a voltage and current display that is designed properly. The original Chinese kits are a copy of an old Greek kit that is/was a project at www.electronics-lab.com and there are a few very long threads there about how to fix it so it does not go up in smoke and how it can be modified to meet its specs.
     
    bushtech likes this.
  6. bushtech

    bushtech

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    Sep 13, 2016
    Wow, thanks Audioguru!. Thank goodness I haven't pulled the trigger on the kit. So where can I find this replacement kit?
     
  7. kellys_eye

    kellys_eye

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    Jun 25, 2010
    Hmmm - 485 'good' reviews on Banggood and even youtube has loads of videos of the PSU being built, tested and working (Voltlog ~#8 and #64 amongst others).

    The two I have also seem to be working just fine...... what am I missing?
     
  8. bushtech

    bushtech

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    Sep 13, 2016
  9. kellys_eye

    kellys_eye

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    Yes, I'd heard about the 'wrong orientation' overlays but that seems to have been earlier editions of the board - certainly the ones I have are properly marked.

    But what I take from the QSL article you reference are the final paragraphs:

    and..

    If people pay $5 for a 'decent' PSU (kit) and accept there may be 'issues' - all resolvable - then what's to complain about? Your alternative is to purchase a 'professional' device for 20x - 50x the price.
     
    Last edited: Jul 26, 2017
    Black Smock and bushtech like this.
  10. bushtech

    bushtech

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    Sep 13, 2016
    @Audioguru: Is there something fundamentally wrong with this design.?

    I must say I am perturbed by Mr Kokotov's calculation of 96W of dissipated power when using a 1V 3A setting although that is probably a rather unusual setting. At 96W you can probably see the power supply glow at 20m.
     
  11. Audioguru

    Audioguru

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    Sep 24, 2016
    The schematic in your link is a copy of the old Greek kit that does not work:
    1) Its output cannot produce 30VDC at 3A, it might go as high as only 25V at 2A.
    2) Its 24VAC transformer will produce about 26VAC with no load then its peak voltage will be 26V x 1.414= 36.8V and the rectifier bridge reduces the positive supply to the opamps to +35.6V. The negative supply for a couple of the opamps is -5.1V so the opamps are powered with a total of 35.6V + 5.1V= 40.7V or more if the AC voltage is higher than nominal. But the TL081 opamps used have a maximum allowed total supply of only 36V so they will probably be destroyed. In the improved version we use TLE2141 opamps that do not need a negative supply as high as -5.1V and their maximum allowed total supply voltage is 44VDC.
    3) To get 30VDC at 3A then the transformer must be 28VAC or 30VAC and the opamps must be TLE2141 with a negative supply of -1.3V.
    4) 96W will destroy the output transistor so in the improved version two output transistors (with emitter resistors) share the heat. I did not look at the Chinese driver transistor to see if it will survive its heat.
    5) Many parts in the original circuit operate above their maximum allowed ratings. I did not check them all in this cheap Chinese kit.
    6) If you turn the current control to maximum the parts values will try to make the maximum output current almost 5A which will destroy many parts. The improved version has calibration trimpots to adjust the maximum voltage to 30.0V and the maximum current to 3.0A.
     
  12. AnalogKid

    AnalogKid

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    Jun 10, 2015
    What is it with that schematic? This is the 2nd time today someone has had questions about, two different people on different fora.

    ak
     
  13. AnalogKid

    AnalogKid

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    Jun 10, 2015
    I thought you wanted a single 0-30 V rail?

    ak
     
  14. bushtech

    bushtech

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    Sep 13, 2016
    ak: Building a modified muffsy phono preamp showed me that 2 rails could come in very handy

    Audioguru: Thank you for taking the time to explain the shortcomings of this design. Where can I find this improved design? Is it available or are there copyright issues?
     
  15. bushtech

    bushtech

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    Sep 13, 2016
  16. Audioguru

    Audioguru

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    Sep 24, 2016
    Yes, that is one of the latest corrections to that awful circuit. It is a shame that the Chinese company copied the original faulty circuit without seeing its faults.
    "Paul" in the link here (he says the Chinese kit works fine when a few parts are replaced and its maximum current is only 1.5A) mentioned that the Chinese copy of the kit uses zener diodes rated at 49mA but they are fed a current that is much too low. The corrected circuit uses zener diodes that were selected by me rated a 5mA and they are fed 5mA.
     
    bushtech likes this.
  17. bushtech

    bushtech

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    Sep 13, 2016
    Thanks Audioguru. So will I be OK if I go with Rev 7 schematic in the first post.? Still wading my way through that lot. Will this design be good for 3A?

    How would this transformer do? http://www.mantech.co.za/ProductInfo.aspx?Item=65M0036-H
    Hmmm. Quite expensive that transformer
     
  18. Audioguru

    Audioguru

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    Sep 24, 2016
    I did not look at Liquibyte's blue changes to my schematic and parts list.

    The transformer datasheet is confusing. It says 2 x 30V at 6A and it also says 2 x 30V at 3A. 360VA is 2 x 30V at 6A which is good because 30VAC rectified makes 42.4VDC which is 42.4V x 3A= 127.2VA and you want two outputs so the transformer must be at least 127.2 x 2= 254.4VA.

    I have never seen a lab power supply that has an adjustable regulated negative output voltage in addition to its positive output.
     
    bushtech likes this.
  19. kellys_eye

    kellys_eye

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    Jun 25, 2010
    The insights to the 'adjustments' of the original design are worthwhile and well received <thumbs up> (I'd seen those before) but bottom line is that the retailer is lying about its capabilities and 0-25V and 0-2A is more realistic. Meh....

    But with the aforementioned mods it ends up as a respectable little unit.

    Still for $6..... - I can't even buy the two pots for that! Mine has 10-turn pots anyway :p.

    It still (to me) equates to purchasing a $1,000 run-around and complaining that it won't do the 140mph the speedo shows it should....LOL.
     
    Black Smock, Terry01 and bushtech like this.
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