power supplies and voltage regulators

[mike134]

Hey guys
I have a few questions
first can i wire voltage regulators in parralel to increase the amps i would assume so but that has cost me before
also i had a 13.8 volt 3 amp power supply that stopped working before when i used i had checked and it was right on the money. so i took it apart and first just took the voltage regulator cleaned it up and put new thermal coumpund to see if it would just magicly fix it well it turns on but now it gives me anywere from 23 to 26 volts. i have no idea what the hell is going on with that.
anyway thanks for any Help
Mike

 

[(*steve*)]

In general you cannot wire voltage regulators in parallel.

The reason is that the voltages on them are not precisely the same, so one will try to supply the entire load.

You could try isolating them with diodes, but I'm not sure that's a hugely viable option either.

The best approach is to get a higher current regulator or to make the regulator supply current via a seperate pass transistor.

There are examples of doing this in many datasheets.

Let's see if I can find one...

See page 13 of this datasheet. Note that this technique may not be generaly applicable.

As regards your regulated supply. It sounds like the full unregulated voltage is appearing at the output. If you didn't make a mistake or damage something when putting it back together, you most likely have a shorted pass element (this may be a transistor, or even a three-terminal regulator.

Without a circuit diagram or pictures and quite a bit of time, we would not be able to say a great deal more.