Ok this is going to sound like i'm contradicting my self but i want a low noise power supply to provide 12v and 5v clean output, from my car (so 12v when engine off, 14.4 when on).
I'll need maybe 30watts available (25w max for a DVD drive and the rest is only to power a spdif convertor (maybe ~100ma? ~2watts?)).
I have no idea how much more a dvd drive robs at 5v than 12v or vice versa. I assume it's like 20w-12v(motors) and 5w-5v(guts).
Just for starters give me 25w @12v and 25w @5v. 😀
I'll need maybe 30watts available (25w max for a DVD drive and the rest is only to power a spdif convertor (maybe ~100ma? ~2watts?)).
I have no idea how much more a dvd drive robs at 5v than 12v or vice versa. I assume it's like 20w-12v(motors) and 5w-5v(guts).
Just for starters give me 25w @12v and 25w @5v. 😀
5v is sorted!
http://www.national.com/images/pf/LM2596/01258301.pdf
Just need a regulated 12v now. 🙂
http://www.national.com/images/pf/LM2596/01258301.pdf
Just need a regulated 12v now. 🙂
Look up a topology called sepic.. this will provide you with the ability to both step up and down from the input voltage. You can get 12V from the battery when the car is not running and while the generator is running and providing providing ~14V on the battery you will still have 12V out.
EDIT: National guide here: http://www.national.com/an/AN/AN-1484.pdf
\\\Jens
EDIT: National guide here: http://www.national.com/an/AN/AN-1484.pdf
\\\Jens
I would be interested in seeing your implentation of the DVD, or even plans to do so. Maybe a post in the car audio forum?
Why the 12vdc when the engine is off and 14.4 when on. If it will run off 14.4v
why build a 12v supply? If you must have 12v your fully charged car battery with
the engine off will be about 12.6v are you sure it won't work on 12.6v instead of
12v?
why build a 12v supply? If you must have 12v your fully charged car battery with
the engine off will be about 12.6v are you sure it won't work on 12.6v instead of
12v?
I will do. Hopefully DVD out via spdif, into a spdif converter, then into (hopefully) a Denon DCT-A100. 😀
Erm, i doubt it will work of 12.6v tbh, I thought PC components are very sensitive to voltages...
14.4v when engine running as alternator charging voltage?
Yes more like 12.6-12.8v, but the point is still the same ( don't forget on load voltage (the rest of the system runnign will pull this down to closer to 12v too ).
I will have a look at that, thanks. It's just the difficulty of sorting out inductors.... Never messed with them before 😕.
........
How about something like this???
12v Regulator Schematic (15A) - MP3Car.com
Post #7 is the updated schematic. But not 1Kohm I think, across the gate and collector, it says something about 220ohm later on.
After re-reading this, it was all a little confusing I need 12v not, 14.4.
So i was just emphasizing the application of it being in car. I need 12v from unregulated 12-14.4v.
Sorry about that 😉
Jens is probably always correct. ;-)
Download LT-Spice from Linear Technology - Linear Home Page (free). When it starts, select File then 'Switch Selector Guide' (at least that's what it was called in my rather-old version). You will be allowed to enter your min and max input voltages, your desired output voltage and max current, and you're halfway there. It will probably suggest only SEPIC converters, and will design them for you. National Instruments has an on-line power supply design tool that is pretty cool, too. http://www.national.com .
If you've never done an automotive circuit, before, then, be afraid, be very afraid. Just kidding (somewhat). But you do need to worry about various types of transients. You would probably want to Google something like "automotive electrical OR electronic transient". You could want to think about using devices to absorb or divert large (say 100V) "load dump" voltage spikes that might last 0.5 second (maybe avalanche diodes, or 'transorbs', or something, or even a special IC). And jump-starting and cold-cranking both cause other phenomena.
Cheers,
Tom
Thanks 🙂
I forgot to say that all this will be powered off a relay which will only be on when my headunit is on (via remote output). So never on for engine starts, or any funny business, so i'm hoping that would make me immune to voltage spiking etc??
Or should I still take this into account.
The relay will be before the input to the regulator, so basically what I let my amplifiers, on load, see i'll let the regulator see.
It's a steep learning curve, fetching the basics, but it's fun.
Thanks for your help so far. 🙂
I'm playing with said software now, but how do I go about winding inductors, or what's the deal with them?
Sepic was mentioned above but I disliked the idea of using inductors, as I have absolute zero experience with them. 😱
Can't find anything allowing me to design a regulator? It's all just pure drawing software...
If you can, could you please send me through your version?
alex_hemming (at) hotmail.com
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I don't think that I have the archived version of mine, any more.
What are the sub-menu options in the main "File" menu option?
Also try national.com's Webench power designer. It's on line, with nothing to download.
What are the sub-menu options in the main "File" menu option?
Also try national.com's Webench power designer. It's on line, with nothing to download.
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Ok, thanks. I've been playing on that software. I love it!!!
Using some info from a link above i've run up this....
It's not great I guess, but from 12.6v to 14.4v only a 170mv change is good enough for me I think!
Is there anything fundamentally wrong with this?
Notes:
The V1 is just there to render the plots.
The zener diodes are just any old 12v ones I found on there... After some playing I found that adding more in parallel tightened the voltage fluctuation, from 0.5v to 0.17v. 🙂
It's quite logarithmically from 12v upto 12.6v, why is this?
As for submenu's on the file option there is the usual, new schematic, new symbol, open, save etc....
Using some info from a link above i've run up this....
It's not great I guess, but from 12.6v to 14.4v only a 170mv change is good enough for me I think!
Is there anything fundamentally wrong with this?
Notes:
The V1 is just there to render the plots.
The zener diodes are just any old 12v ones I found on there... After some playing I found that adding more in parallel tightened the voltage fluctuation, from 0.5v to 0.17v. 🙂
It's quite logarithmically from 12v upto 12.6v, why is this?
As for submenu's on the file option there is the usual, new schematic, new symbol, open, save etc....
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Ok, thanks. I've been playing on that software. I love it!!!
Using some info from a link above i've run up this....
It's not great I guess, but from 12.6v to 14.4v only a 170mv change is good enough for me I think!
Is there anything fundamentally wrong with this?
Notes:
The V1 is just there to render the plots.
The zener diodes are just any old 12v ones I found on there... After some playing I found that adding more in parallel tightened the voltage fluctuation, from 0.5v to 0.17v. 🙂
It's quite logarithmically from 12v upto 12.6v, why is this?
As for submenu's on the file option there is the usual, new schematic, new symbol, open, save etc....
LT spice is a very nice piece of SW IMOH.... and hey it's free & working well!
What happens under load, you have no feedback.... how much does the output drop at say 1A load?
\\\Jens
Oooooh, I didn't notice there was loads available.
It's great software, yes!
Ok so under a 1a load my original design outputs 6v upto 7v... 🙁
Not so good was it 😱.
So, i'll have a look through the theory of sepics now, as you suggested, and if I get stuck / or if I design one, i'll just post it up on here 😎.
(my new years eve is fully occupied now on spice 😛)
It's great software, yes!
Ok so under a 1a load my original design outputs 6v upto 7v... 🙁
Not so good was it 😱.
So, i'll have a look through the theory of sepics now, as you suggested, and if I get stuck / or if I design one, i'll just post it up on here 😎.
(my new years eve is fully occupied now on spice 😛)
Ok, the sepic's idea is way over my head, even with a bit of playing and mad messing I haven't got my head around it... Also with no IC's available and me having to make my own, it did my head in!
I give up on the sepic idea. 😛
So back to the previous idea, if i introduce a feedback run i get great on load characteristics but poor off load ones. What's the best thing to do to my circuit to improve it?
I give up on the sepic idea. 😛
So back to the previous idea, if i introduce a feedback run i get great on load characteristics but poor off load ones. What's the best thing to do to my circuit to improve it?
No chips?!
Search Results: sepic
Virtually ALL of Linear's chips should already be included in your LTspice software. In mine (the older LTspiceIII version), I just click the component button and then click on the PowerProducts folder and there they all are.
And I still "can't believe" that the automatic-power-supply-design feature has been dropped in the "IV" version of the software. When I select "Help", under "Modes of Operation", there is an Overview option that mentions it. And there is a Synthesized Circuits option that describes it, and tells how to invoke it. Maybe your Help menu option will be helpful? On the other hand, I just noticed that linear.com has something called LTPowerCAD for download. Maybe they split it out into that software? Or maybe they're at the following link, now? Linear Technology - LTspice Demo Circuits
They must still have that capability, SOMEWHERE, and I would have to believe that it's better now than it was a few years ago. If none of the above gets you to their sepic circuits, you should definitely do some more searches at linear.com .
Also, note that there is an _excellent_ user group for LTspice, at yahoogroups.com .
Please let us know how it goes.
Happy New Year,
Tom
Found the chips, thanks. 🙂
I've searched help for the automatic circuit builder and got nothing. I'll look about on the website some more, to see what I can find.
I may well be scrapping the 12v idea now, as this: http://www.diyaudio.com/forums/digital-source/157594-inside-onkyo-nd-s1-ipod-transport.html is a lot more appealing to me. (also 5v 1a, so I can use a regulator chip 😉.)
Would the LM2596 work?
Ipod to spdif, if I could make a quite enough powersupply for it, for car use, it would be worth the $180.
And happy new year too.
I've searched help for the automatic circuit builder and got nothing. I'll look about on the website some more, to see what I can find.
I may well be scrapping the 12v idea now, as this: http://www.diyaudio.com/forums/digital-source/157594-inside-onkyo-nd-s1-ipod-transport.html is a lot more appealing to me. (also 5v 1a, so I can use a regulator chip 😉.)
Would the LM2596 work?
Ipod to spdif, if I could make a quite enough powersupply for it, for car use, it would be worth the $180.
And happy new year too.
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Ok, a little more fun with LTspice.
I didn't really know what to do with the shutdown pin, but I managed this? It's to stop the 'roll-down' when the voltage input falls below 5v, the output rolled down too, until about 1v before, however greater than 5v now is much better.
It will mean that when cracking engine, if i were to leave my stereo on (very rare), that it would provide some protection 🙂.
Does all that look ok? No matter what load upto 3a I give it, it's that exact graph.
I didn't really know what to do with the shutdown pin, but I managed this? It's to stop the 'roll-down' when the voltage input falls below 5v, the output rolled down too, until about 1v before, however greater than 5v now is much better.
It will mean that when cracking engine, if i were to leave my stereo on (very rare), that it would provide some protection 🙂.
Does all that look ok? No matter what load upto 3a I give it, it's that exact graph.
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