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  • Designing New DC-ATX Power Supply

    Hi there, I'm playing with this thought for a while now because.
    • The maxim components in SPROGGY's design aren that easy to obtain as thought, besides that they are expensive, if you can obtain them .. (here in The Netherlands I can only obtain 1 of the 2 needed in SPROGGY's design)
      and I think not all of the components used are to easy to get
    • I someone heard about the sproggy supply that this thing wasn't powerfull enough when you are really expanding your system
    • I don't want DC-AC-DC
    • I don't want a pre-made unit like the one from keypower, just because it's way to expensive

    I'm absolutely no electronics expert, but I asked a couple of friends of mine for some help.

    The goal for this is: designing a power supply that is easy to make, and the parts used are available to almost everyone in the world because I think we all want this...

    I was looking through National Semiconductor's webpage and found the LM338. which is an adjustable regulator with the following characteristics:


    LM338T / LM338K
    5a adjustable regulator
    7a peak
    12a short peak
    Vin 4.2 - 40
    Vout 1.2 - 32 V

    and these were very cheap (something like $1.1 each, and like $0.6 for 10 of them)

    I readed the datasheet that is on the website, and it stated that the ouput voltage could easily adjusted with only 2 resistors.

    They also could be assebled in series to produce more amps (like 10a or 15a or maybe even 20a)

    I think that when we use these for all of our positive voltages, the supply could even run at 5v (so the computer will continue to run, even when cranking the car, or with a very bad battery)

    Also a friend of me told me that when he's got the positive voltages, he could easily make the needed negative voltages...
    Is this true ??? (as i don't know too much about electronics, but i want to figure out a decent power supply)

    I haven't looked to the power-good-feature, but I think i can easily adopt this one from the sproggy power supply...

    The supply I was thinking of would supply the following voltages:

    +5v @ 20a (28a peak)
    +3,3 @ 15a (21a peak)
    +12v @ 10a (14a peak)
    -5v @ 1-2a
    -12v @ 1-2a

    According to this, it would be like a ca. 200w supply

    What do you guys think of this,
    Any ideas, suggestions, criticism, whatever is welcome...

    Maybe we could get this of, with globally available components, and every one can build his own power supply very easy !!

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

  • #2
    go for it!
    www.arbybean.com

    Comment


    • #3
      He's prolly using the same parts as Sproggy but have you checked this cat's Dc/Dc ATX supply out? Be forewarned, he IS using Maxim components.
      http://home.primus.com.au/bravo/Carp...bjcarputer.htm
      P4 2.4GHz, Intel mobo w/onboard sound & video, 128MB memory, 100GB Seagate Momentus laptop drive, Xenarc 700TSV 7" touchscreen, IRman using Girder, 150W Opus dc/dc psu, Alpine CDA-9835 h/u, MBQuart speakers, Infinity 15" sub, MTX amps.

      Comment


      • #4
        They also could be assebled in series to produce more amps (like 10a or 15a or maybe even 20a)
        did you mean in series or parallel? I think you mean the later dont you??? If you have any luck be sure to post the circuit. I think you might have problems with the 12 volts rails though using these regulators. The supply will need to maintain about 13.5Volts at all times. Thus your car will need to have a good alternator and be running!

        Good luck anyway!
        Project - GAME OVER :(

        Comment


        • #5
          Sorry Magnetik, I wasn't to clear about this, but thanks for correcting me.

          I think you might have problems with the 12 volts rails though using these regulators. The supply will need to maintain about 13.5Volts at all times.
          I'm a bit confused now.
          In the datasheet there are some examples which will produce like more volts than their input is...
          So for the 12v rail, I don't need an input higher than 12v.
          The regulator should be able to produce 12v with even a 7v input,

          If not, I have to find another sollution, but I think that these regulators are a very good base for my power supply

          If you have any luck be sure to post the circuit.
          Don't worry when things work out i will build a DIY-webpage about this supply.

          Greetz...

          BTW.
          If anyone also has ideas about this, please post them, (as like the 3000 eyes of our 1500 members will see a lot more than only my 2 )

          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

          Comment


          • #6
            He's prolly using the same parts as Sproggy but have you checked this cat's Dc/Dc ATX supply out? Be forewarned, he IS using Maxim components. http://home.primus.com.au/bravo/Carp...bjcarputer.htm
            Thanks for the info Tony S I have looked at it, and maybe i will adopt the Power Good feature.

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

            Comment


            • #7
              Originally posted by Raas:
              I was looking through National Semiconductor's webpage and found the LM338. which is an adjustable regulator with the following characteristics:
              5a adjustable regulator
              7a peak
              12a short peak
              Vin 4.2 - 40
              Vout 1.2 - 32 V
              and these were very cheap (something like $1.1 each, and like $0.6 for 10 of them)
              Wow I never realised how cheap they were wholesale. My local electronics store sells them for $14.99.

              I readed the datasheet that is on the website, and it stated that the ouput voltage could easily adjusted with only 2 resistors.
              True, but this regulator is totally unsuitable for this purpose...read below.

              They also could be assebled in series to produce more amps (like 10a or 15a or maybe even 20a)
              You mean parallel. But you can't parallel voltage regulators and expect it to work very well for very long.

              I think that when we use these for all of our positive voltages, the supply could even run at 5v (so the computer will continue to run, even when cranking the car, or with a very bad battery)
              This regulator will not work for the 12V supply. It requires an input voltage of at least 14V in order to produce 12V out. This will work when the car is running, but not when it is turned off.

              Also a friend of me told me that when he's got the positive voltages, he could easily make the needed negative voltages...
              Is this true ??? (as i don't know too much about electronics, but i want to figure out a decent power supply)
              Yes. It is relativly easy to make a negative voltage from a positive voltage. There are two schematics on my website that will do this.

              I haven't looked to the power-good-feature, but I think i can easily adopt this one from the sproggy power supply...
              Power good is easy. Just a simple RC network.

              +5v @ 20a (28a peak)
              +3,3 @ 15a (21a peak)
              +12v @ 10a (14a peak)
              -5v @ 1-2a
              -12v @ 1-2a
              According to this, it would be like a ca. 200w supply
              This is an insane amount of power, and with a linear circuit heat would become a big problem. I shudder to think of the size of heatsinks required. Also, making -5V and -12V at 2A is no trivial matter.

              Your best bet would be to design a switching power supply, with an output of around 100W or so. Much more manageable.
              Player: Pentium 166MMX, Amptron 598LMR MB w/onboard Sound, Video, LAN, 10.2 Gig Fujitsu Laptop HD, Arise 865 DC-DC Converter, Lexan Case, Custom Software w/Voice Interface, MS Access Based Playlists
              Car: 1986 Mazda RX-7 Turbo (highly modded), 1978 RX-7 Beater (Dead, parting out), 2001 Honda Insight
              "If one more body-kitted, cut-spring-lowered, farty-exhausted Civic revs on me at an intersection, I swear I'm going to get out of my car and cram their ridiculous double-decker aluminium wing firmly up their rump."

              Comment


              • #8
                This may be a dumb suggestion from someone who knows nothing about electronics, buy why don't you just see what Keypower uses in their supply and make a similar design? There are a couple guys that have it that could post a pic of the board.

                Just a thought.

                Comment


                • #9
                  Wow I never realised how cheap they were wholesale. My local electronics store sells them for $14.99.
                  I looked at the Farnell's website.

                  You mean parallel. But you can't parallel voltage regulators and expect it to work very well for very long.
                  Why not ?? the datasheet even has some examples of 10a or even 15a schematics which produce a continious output. I don't think they would show/reccomend these designs if they weren't build to last, wouldn't they ?
                  Please look at the datasheet, there are some very simple 10a and 15a examples. The only thing about them is, that they require a minimum load of 100ma

                  This regulator will not work for the 12V supply. It requires an input voltage of at least 14V in order to produce 12V out. This will work when the car is running, but not when it is turned off.
                  Okay, I probably have to figure out something else for that to have a decent and strong enough 12v supply. Someone probably has done this, so maybe I could learn/addapt something from that.

                  Yes. It is relativly easy to make a negative voltage from a positive voltage. There are two schematics on my website that will do this.
                  Okay, Thanks Man, I will look at them , and maybe use them... Thanks !!!!

                  This is an insane amount of power, and with a linear circuit heat would become a big problem. I shudder to think of the size of heatsinks required. Also, making -5V and -12V at 2A is no trivial matter.

                  Your best bet would be to design a switching power supply, with an output of around 100W or so. Much more manageable.
                  Yes, true, this psu Probably will have a lot of overkill, but I someone heard that the sproggy power supply wasn't powerfull enough. So why not build an extra powerfull psu, like the one your standard desktop pc has. Q. Why does the Keypower PSU have such great capacity ???

                  This might sound dumb, But I actually didn't read anything about a heatsing required. The regulator comes in 2 different styles.
                  • TO-3 Steel, metal can package
                    Which has only 2 pins (Vin,ADJ) and it's case is the output.
                    A Heatsink can't be attached to this one
                  • TO-220, Plastic package
                    This one has 3 pins (Vin,ADJ,Vout) and has this thing where you probably want to attach a heatsink. only thing is, that this thing also functions as an output (Vout) so this regulator has 2 (the same) outputs.
                    And we can't put these all on the same heatsink, because the voltages would screw up

                  So I don't think these things require heatsinks... (altough I must say, I do find this a bit strange....)

                  Meatballman
                  This may be a dumb suggestion from someone who knows nothing about electronics, buy why don't you just see what Keypower uses in their supply and make a similar design? There are a couple guys that have it that could post a pic of the board.
                  This would be very nice.. Now only thing we have to do is wait 'till someone would like to do that..

                  But then... they most likely will use parts that aren't globally available or something..


                  Maybe I'm just going to a bit of the sproggy design, but instead of the maxim chips which are for 3,3v and 5v, I will use some own design using the LM338 regulator..
                  (because, the only thing which blocks me from buildign sproggy's design is that I can't find the required maxim chips.)


                  [sorry for the long post guys]
                  Raas - The Netherlands
                  ME: VIA epia m10000, lilliput 7', opus 150w, 80gb<br>
                  GF: IBM Thinkpad 380, ext. 3.5 80gb, 40x4, PB-IR

                  Comment


                  • #10
                    This regulator will not work for the 12V supply. It requires an input voltage of at least 14V in order to produce 12V out. This will work when the car is running, but not when it is turned off.
                    Maybe someone has a good idea how to produce V[email protected] from Vin=7-16v

                    Or maybe there just a simple part that will product Vout &gt; 14v @ 5a
                    and then I still can use the LM338 to get a decent 12v

                    Does anyone of you have an idea about this ?

                    TIA
                    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

                    Comment


                    • #11
                      Why not ?? the datasheet even has some examples of 10a or even 15a schematics which produce a continious output. I don't think they would show/reccomend these designs if they weren't build to last, wouldn't they ?
                      Please look at the datasheet, there are some very simple 10a and 15a examples. The only thing about them is, that they require a minimum load of 100ma
                      I admit that I have not seen the datasheet. However, are you sure they are not using an external transistor to handle the large currents? This is a common trick.

                      Paralleling regulators won't work because each regulator is slightly different. ie. One may put out a slightly higer voltage than the other. This regulator would then sink more current and either burn up or go into thermal cut off. The other regulators would then try to source the extra current, and wind up with a similar fate.

                      However, they may have found a way to work around this, so paralleling may indeed now be possible.

                      Okay, I probably have to figure out something else for that to have a decent and strong enough 12v supply. Someone probably has done this, so maybe I could learn/addapt something from that.
                      You need a switching type supply. Use a transformer to bring up the input voltage to around 16V, and then regulate down from there.

                      Yes, true, this psu Probably will have a lot of overkill, but I someone heard that the sproggy power supply wasn't powerfull enough. So why not build an extra powerfull psu, like the one your standard desktop pc has. Q. Why does the Keypower PSU have such great capacity ???
                      I don't know anything about the "Sproggy" power supply, but odds are the keypower unit is simply designed to mimic a desktop supply for maximum expansion capability. Since you know how much power you need, you can build a supply for that amount of power and not waste money on capacity you will never need.

                      This might sound dumb, But I actually didn't read anything about a heatsing required. The regulator comes in 2 different styles.
                      Heatsinking is absolutely required!

                      TO-3 Steel, metal can package
                      Which has only 2 pins (Vin,ADJ) and it's case is the output.
                      A Heatsink can't be attached to this one
                      Yes, it can. I have used this regulator in several power supply designes. It will go into thermal cut off in a few seconds if there is no heatsink. The TO-3 style case is connected to a heatsink with a mounting kit. It contains a gasket, some plastic screw insulators and usually a ring terminal to make the case connection. The heatsink is simply drilled to accept the TO-3 device. Pull apart an old TV and look at the vertical output transistor for an example.

                      TO-220, Plastic package
                      This one has 3 pins (Vin,ADJ,Vout) and has this thing where you probably want to attach a heatsink. only thing is, that this thing also functions as an output (Vout) so this regulator has 2 (the same) outputs.
                      And we can't put these all on the same heatsink, because the voltages would screw up
                      These also need a heatsink. Again, there is a mounting kit available that isolates the tab from the heatsink.

                      So I don't think these things require heatsinks... (altough I must say, I do find this a bit strange....)
                      Yes, they do. For the LM338K, active cooling is not a bad idea either. It will keep the size of the heatsink to a minimum.


                      Meatballman
                      Player: Pentium 166MMX, Amptron 598LMR MB w/onboard Sound, Video, LAN, 10.2 Gig Fujitsu Laptop HD, Arise 865 DC-DC Converter, Lexan Case, Custom Software w/Voice Interface, MS Access Based Playlists
                      Car: 1986 Mazda RX-7 Turbo (highly modded), 1978 RX-7 Beater (Dead, parting out), 2001 Honda Insight
                      "If one more body-kitted, cut-spring-lowered, farty-exhausted Civic revs on me at an intersection, I swear I'm going to get out of my car and cram their ridiculous double-decker aluminium wing firmly up their rump."

                      Comment


                      • #12
                        Aaron, Sproggy's Power supply info and schematics can be found here if you're interested.

                        Comment


                        • #13
                          Raas just few points from me.
                          Two years ago i end up designing my own PSU as i couldnt find anything on the market at the time, im still using the same supply as it does the job. Its AT based but can easly be modified to work with ATX. The design is similer to Sproggies...
                          Even though we were working seperatly with Sproggy we came up with around the same sort of solution using basicly the same parts. And why is that cost that was most cost effective, Simple to build, very ( and i mean very) efficient design.
                          No offense but the way i see it its gona take you more then a year or so to come upi with another design, considering the level of knowladge you have in electronics... its not as simple process of just looking at the datasheet and putting blocks together.
                          It took me good few months to do the researh and design something that can be stable and reliable to use.
                          Few points:
                          There are no cheap/common components that will produce the required +12v. You will need a some kind of transformer and for the wattage you talking about its going to be very expansive, unless u wind it yourself.
                          You CAN'T use LM338 for +12V rail ... its linier regulator and needs at least 1.5V above the output voltage which the car is not able to provide at all times.
                          So the only solution is to use flyback regulator design which in-itself requires a transformer. Most flyback regulators using common parts will not give you current higher then 2amp ( and that is the peak power for them).
                          What you need is a taransformer similer to the ones from normal PSUs but in that case you will need to pump up the +12volt input to 40v AC so then you can put it through that transformer to get the required woltage output. But all this requires engineering touch... And i can garantuee you it wont be cheap. I was planning to get in to this solution design but i never have time now days...
                          Another thing... You could use LM338 for +5 and +3.3 rails however, they require bigger heatsink, they big insize themselves, not as efficent as the Maxim parts...
                          You dont really need more then 10amps for the +5volt rail... this will run your main PC plus two HDs + CD/DVD and probably will have bit left in it for some other things.
                          Negative rails are easy to get from the positive +5 or +12, and they dont need to be more then 500mA Max.
                          Bit of a long post but at least something to help you to reduce your hours on research.
                          Fosgate

                          System Comp V3 - In progress.
                          Low power MB with C7 CPU, DC-DC PSU, car ECU link, USB TV, GPS, 7" TFT, Wireless, Voice.

                          Comment


                          • #14
                            Originally posted by Aaron Cake:
                            However, are you sure they are not using an external transistor to handle the large currents? This is a common trick.
                            They use a LM308 IC-SUPER GAIN OP AMP to handle this.

                            Heatsinking is absolutely required!
                            I must admit I thought this was required, but I didn't read anything about it in the datasheet.
                            And there was once a datasheet of some component (don't know exactly which one) which stated that it needed a heatsink.
                            So I was a bit confused that I didn't read anything about it in the LM138 datasheet, so maybe it wouldn't need a heatsink, but Thanks for clearing that out !!!

                            Fostage:
                            I would have made Sproggy's supply if only I could get my hands on some Maxim parts which aren't available in the Netherlands. And I doubt that the maxim parts will be the only one hard to get here. I think i might have a problem with the coils too.

                            You're absolutely right about my knowledge of electronics, But i've got 3 friends who dont do anything else but electronics for their work and they are willing to help me with this. (don't think that they have like some 30 years experience, but I think this could be worked out by the 4 of us)

                            Well, I can't expect everything to be cheap in this design.. With the LM338 regulator, I almost shaved off 85% of the building costs for the +5v and +3,3v. So it doesn't matter when the 12v rail becomes a bit more expensive.

                            Maybe these Regulators won't have the same efficiency as the Maxim parts you used, but it will be a LOT more efficient than an DC-AC inverter wouldn't they ???
                            And they cost about 10% off what the maxim chips will cost me. (If I can obtain them, i can only do 1 of the required 2). So in some way I can say that these regulators are more efficient.

                            That these things are a bit bigger doesn't matter to me.. I still think that the power supply would fit in a normal power supply, and that's my only other option.

                            But,
                            Thanks for the long post, I can only learn from this. keep it coming!!

                            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

                            Comment


                            • #15
                              Raas why dont you order those Maxim parts as Samples ... they you dont have to pay anything for them ...
                              Maxim is based in UK so you will get them in matter of days ...
                              Here is your solution...
                              Coil is just another story ... coilcraft doesnt supply them any more but i guess with the help of your friends you should be able to make anoe of those transformers at home ... its not that hard, we used to do it heaps
                              Fosgate

                              System Comp V3 - In progress.
                              Low power MB with C7 CPU, DC-DC PSU, car ECU link, USB TV, GPS, 7" TFT, Wireless, Voice.

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