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PC Power Supply and 12V Boost Converters

Discussion in 'LED and other Lighting' started by analog1961, Apr 21, 2017.

  1.  
    analog1961

    analog1961 Member

    Has anyone used a pc power supply and boost converters? I have high quality pc power supplies I adapted for use as bench power supplies. 12V boost converters are inexpensive roughly $5 for 150W. One supply I could use has 4 18A 12V rails for a total of 680W. PC heat sinks with with fans are about $10, maybe a little more depending on power levels. I'm thinking this could power 4 high power cobs. I have spools of wire, connectors, etc. All I need is a mounting system for a 2x4 space. Any suggestions for cobs? I'm thinking vero 29.

    For a high power vero 29 has anyone used pc heat sinks?
     
    Last edited: Apr 21, 2017
  2.  
    Randomblame

    Randomblame Well-Known Member

    Screenshot_20170421-114018.png It should work but's it's not very efficient to boost from 12 to 36v.
    And in most of the cases you need a heatsink if you drive these cheap buck converters higher. (1A+)
    You need at least constant current converters(2 poti's) to power a COB.
    I would recommend to use Meanwell LDD drivers, they have an input from 2-52v and output 3-48v or so, 97% eff., maybe 90% with 12v in/36v out. They are cheap and dimmable and there are boards avaiable to mount 4 or 5 of these drivers together, one power input and 4 or 5 dc outputs. And they are available in 350-1500mA, for 5-6$. Here's a screeny of a 5x board with 5 of these drivers, but it's one of the cheapest. There are better ones, only a quick search on ebay
     
    Last edited: Apr 21, 2017
  3.  
    analog1961

    analog1961 Member

    Thanks, I was wondering about controlling current and dissipating converter heat. I checked Mouser electronics, they have a full range of Meanwell power supplies. Constant current is the way I'll go, here is a statement by Rick Frosch, Director of Engineering, Phihong USA:

    "Constant-voltage LED drivers are subject to losses in current limiters, which decreases the efficiency of the higherpower LEDs typically used in general illumination applications. Constant-voltage LED drivers also require an additional conversion stage, and thus a greater number of components to power multiple LED strings. Consequently, since each additional component within a system increases the potential for system failure, constant-voltage LED drivers can reduce the reliability of general illumination lighting fixtures. Additionally, constant-voltage LED drivers are not a reliable solution for driving white LEDs. Voltage source deviations as small as 5% (i.e. from 3.3 to 3.5V), which are a normal occurrence when using constant-voltage drivers, can elicit a 100% difference in forward current (i.e. from 350 to 700mA), violating the LEDs’ absolute maximum current rating. When driven at currents in excess of their specified load range, LEDs emit brighter light and generate additional heat, which degrades their light output at a faster rate and significantly reduces their useful lifespan."

    I'll try it with a pc supply with a cob I have already and compare power draw to a driver I took out of a cheap panel.
     
    Last edited: Apr 21, 2017
  4.  
    1212ham

    1212ham Active Member

    Constant voltage works fine with cobs, Mean Well wouldn't make CV drivers if it didn't. There are pros and cons to constant voltage vs constant current, but it's largely a matter of personal preference and cob/driver matching. I have a 36v Mean Well supply that works well driving cobs directly and has a voltage trim pot, but about 30% more will buy a Mean Well HLG series driver.

    I've run cobs directly with three PC supplies in series. xbox supplies worked well but some ATX supplies didn't have very good regulation and the voltage would drop under load. I was able to find a trim pot and turn up the voltage to compensate but it's not a great setup. As mentioned, the 12v supplies with boost converters won't be the most efficient, I think I saw around 70%. My Mean Well HLG is something like 88% running on 120 AC. Efficiency would probably be higher feeding the boost converters 24 or 36 volts, or feeding buck converters with 48v.
     
  5.  
    1212ham

    1212ham Active Member

  6.  
    Roger A. Shrubber

    Roger A. Shrubber Well-Known Member

    i've been running quantum boards with essentially the same thing and a couple of buck converters. they're running over 80% efficient, and cost me less that 150 for 2 boards. the biggest cost was the buck converters, but i really like these adjustable ones.
    https://www.amazon.com/gp/product/B01MSJQAKY/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1

    100_2574.JPG
    as far heat sinks go, i got pissed one day pricing them, and went to home depot, bought 20 bucks worth of aluminum "angle iron" and c channel, thermal glued them together, viola, effective heat sinks for 20 bucks.

    so what you want to do should be entirely possible, give it a shot
     
  7.  
    analog1961

    analog1961 Member

    Thanks can you give me a source for quantum boards?
     
  8.  
    analog1961

    analog1961 Member

    Thanks I have an 80 PLUS Platinum 92% power supply I can use and a bunch of 80 PLUS Gold 90% supplies. The platinum one has almost undetectable ripple, I used it in a gaming pc.
     
  9.  
    OLD MOTHER SATIVA

    OLD MOTHER SATIVA Well-Known Member

    that is one pile of potential affordable watts

    can it be used for led panels and cobs ..?

    seems like it needs some other box to convert to more a usable due to
    high Current/low dc?
     
  10.  
    analog1961

    analog1961 Member

    I was thinking of a cheap dc to dc converter but Robert A. Shrubber above suggested this:

    DROK DC-DC Numerical Control Step Down Voltage Converter, 6-65V to 0-60V 8A 400W Buck Voltage Regulator Stabilizer, Constant Voltage Constant Current Power Supply with Volt Amp Dual LED Display
     
  11.  
    OLD MOTHER SATIVA

    OLD MOTHER SATIVA Well-Known Member

    thank you

    if 1200 watt step down Vf converters cannot be found then one has to get smaller 80 PLUS Platinum's?

    at any ratei learned something new today

    [besides what it's like to get a gall bladder removed ]

    lol..sorry its been a long day
     
  12.  
    1212ham

    1212ham Active Member

    Last edited: Apr 21, 2017
  13.  
    analog1961

    analog1961 Member

    I'm thinking of getting Meanwell LDD and a few different ones like you suggested this morning to try. I have a roleadro 400W I'm converting to Citizen CLU048-1212 cobs, it's extremely easy just thermal adhesive or drill to mount and use 2 of 4 drivers available. For the more powerful setup I want to build I want a high output cob like a vero 29, over 10,000 lm. I'll use either extruded heat sinks or discrete pc cpu heat sinks.
     
  14.  
    analog1961

    analog1961 Member

    [
    You can use arbitrarily large power supplies, you just have to add the voltage and current controlling circuits built in to led drivers like Meanwell LDDs.
     
  15.  
    OLD MOTHER SATIVA

    OLD MOTHER SATIVA Well-Known Member

    Yes but are there vf converters that match that arbitrarily large size PS was my question?

    the largest LLD i saw was 22.1 vf..and that 1200 w PS could supply a lot of leds

    the Drock said 400 w..awesome ..but does not seem to match 1200 w
     
    DankaDank likes this.
  16.  
    analog1961

    analog1961 Member

    There are some I've seen in the 600W range, but I've literally only been reading about led lighting for a few days. You could use 2 to power separate circuits. I just did a quick search, here's one for about $130 that matches 1200W with up to 60V out at proDCtoDC. I can't post links yet.
    1200W 20A/60V DC High Current Programmable Digitally Controlled Power Supply TTL
     
    Last edited: Apr 21, 2017
    OLD MOTHER SATIVA likes this.
  17.  
    OLD MOTHER SATIVA

    OLD MOTHER SATIVA Well-Known Member

    so does that actually mean with that one like that could poweranythin up to 60vf with no added converter..

    two separate circuits...there are two outs on it..?

    also does that 20A current make things difficult in led/cob land?

    awesome..only few days reading about leds ..

    also do not i know much..i am trying hard , it has become my new hobby, this a wonderful site

    and

    re "ANALOG" my favourite possession is a15 IPS Ampex 16 track MM1000
     
  18.  
    analog1961

    analog1961 Member

    The 1200W 20A/60V DC High Current Programmable Digitally Controlled Power Supply TTL is capable of 1200W when both the current and the voltage are at their maximum. In general P=VI in a DC resistive circuit where P is power V is voltage and I is current. Maximum power is then 1200VA=60V*20A or 1200W. The maximum voltage drop across an led would be 60V so 2 36V leds in series would possibly exceed the limit if the current was set too high. I plan to use multiple smaller converters one for each cob so for each converter if the pc power supply had 4 12V rails you could use one rail per cob and have 4 separate outputs. It would be like 4 300W separate power supplies. Each of the 4 outputs could be adjusted for a constant current corresponding to the current you plan to drive the cob. I'm specifically not looking for higher voltage systems that can power multiple cobs in series. If you add more cobs to one rail just don't exceed the maximum current per rail.

    Have you had physics or any engineering courses?
     
  19.  
    analog1961

    analog1961 Member

    [
    The 1200W 20A/60V DC High Current Programmable Digitally Controlled Power Supply TTL is capable of 1200W when both the current and the voltage are at their maximum. In general P=VI in a DC resistive circuit where P is power V is voltage and I is current. Maximum power is then 1200VA=60V*20A or 1200W. The maximum voltage drop across an led would be 60V so 2 36V leds in series would possibly exceed the limit if the current was set too high. I plan to use multiple smaller converters one for each cob so for each converter if the pc power supply had 4 12V rails you could use one rail per cob and have 4 separate outputs. It would be like 4 300W separate power supplies. Each of the 4 outputs could be adjusted for a constant current corresponding to the current you plan to drive the cob. I'm specifically not looking for higher voltage systems that can power multiple cobs in series. If you add more cobs to one rail just don't exceed the maximum current per rail.

    Have you had physics or any engineering courses?
     
    OLD MOTHER SATIVA likes this.
  20.  
    visajoe1

    visajoe1 Well-Known Member

    this topic as been discussed previously. the expert opinion is, yes technically the 12v and booster setup will work, but isnt dependable for daily usage.. much better to just spend the extra few bucks on a cv/cc driver.
     
    OLD MOTHER SATIVA and analog1961 like this.

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