Paralleling voltage regulators?

[m.parigi]

I need 5V with lots of current (5A+) for a project I'm working on. I have easy access to 5V, 3A regulators (got a couple floating around in the house), I was wondering whether I could put a couple of them in parallel in order to achieve the desired current.
Can it be done? Which extra components (if any) do I need to add?
I'd really like to stay away from more complex schematics if anywhere possible...

 

[sam9]

Yes but don't simply tie them together. Put a small value 5W resistor on each output lest one regulator tends to do all the work. I've done this with adjustable regulators at much higher voltages.

Better still, if you can find a copy of Joseph J carrs's book "DC Poer Supplies", I think that will show an even better way to do this.

 

[li_gangyi]

Use a pass transistor to increase the current it can take...if u really need a hell lotta current...configure the 7805 (I'm guessing here) to be a small SMPSU thingy...just add in a few parts and inductor and u're set...

 

[cpemma]

Cheap & cheerful way is to use a 7805 with a diode between ground pin & ground to get 5.7V, then apply that to the base of an NPN power transistor connected as an emitter-follower (load between emitter and ground).

There are better-protected ways of using a pass transistor, look in the 317T datasheet for examples or there's one here.

 

[Matttcattt]

I have asked about this before.

I used a pass transistor as described.

See here:

http://www.repairfaq.org/sam/samschem.htm#schslp2

http://www.mitedu.freeserve.co.uk/Circuits/Power/boosti.htm

http://www.chantronics.com.au/Data/Voltage_regulators/voltage_regulators.htm