Help with Making a 5V/3A voltage regulator

**nirvanades** · 09-13-2004, 05:26 PM

Hello All :

I am working on building a 5V/3A voltage regulator from my car battery. I am going to use this to power my Audigy2 NS. I am a little lost on the AMP aspect of the regulator. The 7805 is 5V/1A - how do I boost the AMPS?

My soldering skills are there - I understand the basics - just don't understand what parts to buy and how to link them so that I can power my external USB soundcard. Any help is greatly appreciated!!! I did search and haven't found the exact topic I need help with.

**m3rdpwr** · 09-14-2004, 02:06 PM

One option:
Sanity Check
Be sure to read the whole thing as their is a problem with that schematic.

There in a 7805 in a T-03 package I believe that supply's 3 amps.
Simple to build, but it gets pretty hot.

You may want to look for a cigarette lighter adapter that will do it and chop off the plug to hard wire it in.

-Mario

**MrPerfectionest** · 09-14-2004, 03:23 PM

Be prepared to dissipate ~25W of heat at 3A.

**rando** · 09-14-2004, 04:08 PM

TI PT6625 (5V/6A). It doesn't get any easier. I use a variant (PT6653D 5V/5A) to power my Audigy NX. It works great and doesn't get hot at all. Search for a post by Rob Whitney.

**m3rdpwr** · 09-14-2004, 04:10 PM

What he said...

**nirvanades** · 09-14-2004, 04:15 PM

m3rdpower - I have used the 7805 but they are only 1amp and I need 1.5amps minimum. I haven't seen a 3 amp version - but if it is out there I would love to work with it because the 7805 was VERY easy to work with. Also, I posted that schematic and built it last night. there were a few errors, but I have since modified them and I am re-working everything tonight after blowing the 10mf cap on the 5V out.

MrPerfectionest - I have a really nice heat sink which worked well with 5A last night - it gets hot - but not crazy hot!

Rando - I will check out the TI stuff - I have read a lot about it - but the only place I have seen to get them is online. I am always in to buying and building - I can never wait!!! LOL Anyways - I will research the PT6625 and perhaps build V2.0 with that one!

Thanks guys!!!

**rando** · 09-14-2004, 04:20 PM

The TI and 7805 hook up to your circuit essentially the same. Input, GND, Output with caps across the input and output rails. The TI also has an enable/disable input, feedback, and some voltage adjustment pins that you can ignore. You're right, you can probably only order them on-line.

The linear regulator approach probably isn't going to work for you unless you're willing to use a massive heatsink and fans. 25W+ of heat is a crap load! You've already waited a day just for these replies. If you're clever, you can have the TI chip at your place by tomorrow / Thursday at the latest.

**nirvanades** · 09-14-2004, 04:21 PM

rando - where is the best place to buy them? and I appreciate your help!

Why does the linear chip create more heat?

**m3rdpwr** · 09-14-2004, 04:28 PM

Originally Posted by rando

The TI and 7805 hook up to your circuit essentially the same. Input, GND, Output with caps across the input and output rails. The TI also has an enable/disable input, feedback, and some voltage adjustment pins that you can ignore. You're right, you can probably only order them on-line.

The linear regulator approach probably isn't going to work for you unless you're willing to use a massive heatsink and fans. 25W+ of heat is a crap load! You've already waited a day just for these replies. If you're clever, you can have the TI chip at your place by tomorrow / Thursday at the latest.

I agree, they get hot as hell.
I still have my fixed and variable output I built in 1985 in high school.

I would assume the TI that rando mentioned is switching type regulator which is why it doesn't run hot like any 78xx series linear regulator.

-Mario