Thread: Dc-dc +/-15v, 5v

Power supply design is not exactly an easy business. You'd be much better off looking at a commercial solution, or using an inverter. AS you said you dont think you have the ability to do it, so a prebuilt one seems a better bet.

Dave

Building a PSU which can output +/-15V on your own will probably be quite hard, especially if it's powering audio equipment...

+/-15V is actually a 30V difference, centered at 0V. Doing this with a standard AC transformer is quite easy as you can just rectify it from a double wound transformer. But in a car I think you might have to look at designing a flyback or fet controlled system, which is way way over most people's head's.. I'm not aware of many simple switch mode ICs which can do -15V from 12V..

Also since it's audio equipment it's going to be susceptible to noise (you're wanting to run an equaliser or something like that right?). Most DC-DC PSUs aren't fantastic for that (the only reason why everyone's car mp3 players are working is because the ATX spec is pretty easy with ripple), and you might find yourself stacking lots and lots of caps on a PCB to remove this.

I'd suggest you either use a pure since wave inverter or buy a equivalent car audio product to whatever you want to run...

Thanks for the replies so far guys. A friend of my parents had a restaurant that just closed down and he offered me some of the equipment that they were using. I took a Rane RPM26 processor and a Crown K1 in trade for 2 weekends of labor. The Rane is a pretty hardcore ProAudio unit and I would REALLY like to integrate it into my stereo. In addition to doing just about any kind of audio processing that I would ever need it also has an AES3 input that I would like to feed from the soundcard of a carputer. And I would like to run the Rane Dragnet application on the carputer to control it. Here's a link to the RPM26, and here's a link to the schematic.

I did a search before my first post and saw the Sproggy schematics for power supplies. In my original post I was wondering if I could take something like the Mk2.5 and use a different IC to get the voltages that would apply to my install. Although I didn't assume it would be a straight swap the replies so far have me thinking that it is much more difficult than modifying an existing design. I am OK with having someone else design and build the PS or even an off-the-shelf solution, but I would like to learn something from this project and be as hands-on as possible.

Also since it's audio equipment it's going to be susceptible to noise (you're wanting to run an equaliser or something like that right?).

What I am looking for is something reliable that will not burp when the starter is turning over the motor. Obviously noise is important, but it is not as critical as I was able to run a fully balanced signal from headunit to amplifier. And I can use a digital signal from the soundcard to the AES3 input.

Most DC-DC PSUs aren't fantastic for that (the only reason why everyone's car mp3 players are working is because the ATX spec is pretty easy with ripple), and you might find yourself stacking lots and lots of caps on a PCB to remove this.

I did find some ICs that look like they have the right specs. The prices range from about $60US-$150US. Since I got the Rane for basically free I wouldn't mind spending money to sort out a proper PS. Wouldn't adding a 4 caps on the output (5V/earth, +15V/earth, -15V/earth, and +15/-15) and a choke on the input smooth the ripple? I am still open to using a DC-AC inverter, but I would like to understand how I would do the DC-DC conversion even if I went the DC-AC route.

Here are two ICs that I found. There are a bunch more out there, whether or not you can actually buy them and get them shipped is another story. Am I on the right track with something like this? If I were to go DC-AC is there a model line that you would suggest? Thanks!

http://www.elektroautomatik.de/new/s...67e10361343bee
9-18Vdc input, +5V / ±15V @ 6A / 1,5A / 0,5A - 129,00EUR

http://www.amplicon.co.uk/data/2500hn.html#2505/15T12HN
2505/15T12HN 25W 9-18Vdc input, 5Vdc @ 4A, ±15Vdc @ 0.5A outputs. £ 42.84

EDIT:typos

Try this place:
Quality Kits

This is an unregulated power supply kit, originally designed for an audio amp, so you will have to add +15v and -15v regulators.

Study the schematics CAREFULLY to find the appropiate points.
Also, you might have to remove some components from the RPM26 board.