~12v ~50a Power Supply
Dec 24, 2012 at 6:17 PM Thread Starter Post #1 of 18
xfinrodx

xfinrodx

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So I've been in need of a project for a while, and my pocketbook isn't going to allow me to just start buying cool components and making an ideal setup.  That said, it is easy to "nickel and dime" my way (my wife
wink.gif
) into something workable.
 
In case the voltage and amperage in the title didn't make this thread a dead giveaway, I want to use my car audio equipment to provide bass to my computer system.  I have an older Infinity Kappa Perfect 10" subwoofer and a couple boxes I made out of 3/4" MDF - one sealed, one ported.  Also, I have an Alpine MRP-M400 amplifier that makes it sound just ever so nice.
 
I'd like to make a 13.8v (really, 12-14 is ok) power supply capable of providing around 50 amps.  I can use capacitors to smooth out the load if it winds up peaking higher than that, but I think it should be sufficient.  (13v * 50a = 650w)  I've done a lot of various DIY before, but I have yet to design and build an IC.  I have repaired them and understand the overarching goal but I'd like to do something like this which is a little more than I've had experience with.  Doesn't need to be regulated super well since car electric systems sure aren't, but 120v ac obviously won't do.
 
Don't worry about the line voltage implications and all that, I'm a big boy and I've wired buildings to code, both high and low voltage:  I've also been electrocuted and I have a healthy respect for the little electrons.
 
It might sound terrible, but at worst I'll gain the experience of building a power supply and come away with a good piece of testing equipment for car electronics accessories! 
 
So what I'm looking to you fine folks for is advice:  What's worked for you?  Are there any better plans out there for what I want to do (maybe with components marked more clearly)?  Is it worth digging into my heap of computer power supplies for components?  Can I meet this power goal without needing a fan?  What am I not considering here?


I'm not 100% married to the 50a idea. It's what would be needed if I were to use my existing 12v amp though. 400-600 watts is not so astronomical for a subwoofer, but 50a admittedly is a lot of current in a domestic setting. I was actually thinking about nixing this whole idea in favor of an XLS-202, but I'd still rather build my own amp. I'll change the title, as it's looking like my project has evolved. Sanity has sunk in too deeply for me to continue with the big 12v supply.

What I want to do now is build a 110v amplifier: Just a simple monaural output, targeted at driving an Infinity Kappa Perfect 10 vq. Should be around 400-600 watts (RMS). What's an easy circuit that offers good quality and high output? Also, I'd like to have cake and eat it too. :) Is it possible to do this for under $200?
 
Dec 24, 2012 at 8:27 PM Post #3 of 18
I knew that was coming. :) The goal isn't really to ghetto rig it up. I might do the battery thing just to proof-of-concept it, but it's not a permanent solution. It would be perfect for the garage though...
 
Dec 24, 2012 at 9:38 PM Post #6 of 18
Tomb, I was looking around and the lm317 circuit can be used as a regulator, but probably isn't the best to get up to 5-700VA. Thinking I'll probably have a lot of parallel components to reach the power goal. I really appreciate your input! There isn't an ac-dc ripple in the same way, but old alternators definitely play fast and loose with the notion of regulation.

Avro - I'll consider a battery based solution, but it'll be tough to make it look nice. It's nice to know that it is a viable option. I like the idea of isolating from the grid for sure. Can't stand the thought of battery acid or fumes leaking into a living space :xf_eek:
 
Dec 24, 2012 at 9:54 PM Post #7 of 18
Quote:
xfinrodx said:
Tomb, I was looking around and the lm317 circuit can be used as a regulator, but probably isn't the best to get up to 5-700VA. Thinking I'll probably have a lot of parallel components to reach the power goal. I really appreciate your input!
Click to expand...

I was hoping no one else saw that post.
redface.gif
  As I said, I misread 50A as 50VA.
 
Dec 24, 2012 at 10:22 PM Post #8 of 18
tomb said:
I was hoping no one else saw that post.:xf_eek:   As I said, I misread 50A as 50VA.
Click to expand...


No worries man, it still contributed! I might wind up pursuing a battery route, but it might be too expensive, considering that I would need very specific enclosures and a sealed battery in addition to a charger. Plus I want to make something with the Hakko I'm getting soon :)
 
Dec 24, 2012 at 11:02 PM Post #9 of 18
Very few real amplifiers use batteries for their power supplies.
 
On that note, for the amount of effort you will spend getting the necessary current at such low voltage you could just as easily build a higher voltage amp designed to run off the wall from day 1. There are quite a few single chip amps with very simple power supplies. The Gainclone "family" of amps comes to mind as a prime example. 
 
I suppose that a more conventional (in home hi-fi anyways) higher voltage/lower current amplifier could be tricky if you already have your speakers wired as VERY low impedance loads (2ohm or less) but its worth another mention. 
 
If you do need to stick with a ~12V supply be sure to consider whether you will need to heatsink your rectifier diodes - they will probably need it at 50A.
 
Dec 24, 2012 at 11:45 PM Post #10 of 18
nikongod said:
Very few real amplifiers use batteries for their power supplies.

On that note, for the amount of effort you will spend getting the necessary current at such low voltage you could just as easily build a higher voltage amp designed to run off the wall from day 1. There are quite a few single chip amps with very simple power supplies. The Gainclone "family" of amps comes to mind as a prime example. 

I suppose that a more conventional (in home hi-fi anyways) higher voltage/lower current amplifier could be tricky if you already have your speakers wired as VERY low impedance loads (2ohm or less) but its worth another mention. 

If you do need to stick with a ~12V supply be sure to consider whether you will need to heatsink your rectifier diodes - they will probably need it at 50A.
Click to expand...


The sub is DVC at 4 ohm per. I'll probably run it at 8 ohm. If a higher voltage amp is reasonable to build, and will sufficiently drive a sub like this, I would be thrilled to do that instead. I find a lot more information on more general purpose amps than monaural subwoofer drivers. Needs a fair bit of power, but you know - I don't need the best for this. I'd like to do better than a psw-10, but you know... It's my first time making an IC.
 
Dec 25, 2012 at 8:55 PM Post #11 of 18
You want 50 Amps? 50 Amps?
 
I think you need to reassess what you're doing here. 12VDC into 2 ohms resistive is 6A.
 
Now, car amplifiers can draw a lot of current, but this is usually because they are switching amplifiers, or incorporate switch-mode PSUs, to drive high current into typical speaker impedances in a bridged configuration, and in cases like that can pull high currents, maybe 50A, but a domestic subwoofer? This is just looking for unnecessary trouble.
 
You won't find it easy to source a transformer providing 650VA @12V, single sided. 50A is a thick wire. The ripple currents are going to be large, the rectifier diodes are going to be huge, the regulator will need big heatsinks. Heat evolved is per the square of the current. The 50A lab PSU I used weighed well over 100 lbs and occupied a square yard of bench. It was dual-rail, admittedly...
 
Then there's the expense. This is not a cheap way to go.
 
You need to aim for a median current, less numerically than the voltage. ~40V & 10A. A dual-rail supply, not single-rail. This will result in a more economic design, using middle-of-the-road components and allow you to use DC coupling.
 
First pick a target power output. Then decide what speaker you're going to use, with what impedance. Then calculate the voltage swing required to deliver the power into that speaker. ((Vrms)^2)/R. This will give you the peak voltage per side (Vrms*1.41). Lastly calculate the current.
 
Now you're in a position to select an amp and design a PSU.
 
Something like that...
 
w
 
Dec 25, 2012 at 9:13 PM Post #12 of 18
I'm not 100% married to the 50a idea. It's what would be needed if I were to use my existing 12v amp though. 400-600 watts is not so astronomical for a subwoofer, but 50a admittedly is a lot of current in a domestic setting. I was actually thinking about nixing this whole idea in favor of an XLS-202, but I'd still rather build my own amp. I'll change the title, as it's looking like my project has evolved. Sanity has sunk in too deeply for me to continue with the big 12v supply.

What I want to do now is build a 110v amplifier: Just a simple monaural output, targeted at driving an Infinity Kappa Perfect 10 vq. Should be around 400-600 watts (RMS). What's an easy circuit that offers good quality and high output? Also, I'd like to have cake and eat it too. :) Is it possible to do this for under $200?
 
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