two Regulator in parallel ??? help needed

[tom_hanks]

Hi,
Therotically we can put two regulator parallel to inc rease the current output..


I am planning the same to put two regulator (3A) in parallel to acheive the output of 5A load....

is it acceptable...
:?:
what care i need to take?

Tom

 

[sadat007]

Yes with a low ohms series resistor at every regulator output

 

[IanP]

It is not a good idea to connect voltage regulators such as 78XX in parallel ..
Adding equalizing resistors or diodes will always deteriorate the output voltage regulation ..
However, if you would like to experiment - here is an example .. see picture below ..

Much better idea is to add an external PNP power transistor ..
**broken link removed**


Regards,
IanP

 

[tom_hanks]

it do not look safe....
may be i have to use indivual load per device..
thanks buddy for your veiws..

 

[cyber1]

inc rease the current output

 

[manojshukla]

You may use two regulator in parallel by connecting their legs tied togather for increasing the current output.

 

[tom_hanks]

by connecting legs ??
Which legs...
are you trying to say...
by connecting two pins..
then which pins...

o/p pin?

 

[doss]

hi,
It will work,but u have to make sure the o/p voltage is constant because it will decrease when load increases .It again depend upon u r design,

Added after 8 minutes:

hi,
It will work,but u have to make sure the o/p voltage is constant because it will decrease when load increases .It again depend upon u r design,

 

[roy mathew]

Hi
I feel conecting two regulators parellelly is not good idea for the long term truble free operation of a circuit,

even a dry solder could result in blowing up both devices.

 

[Verba]

78XX-in-parallel is not really a good regulator. If the current is not constant, the output voltage will change up to few huhndreds millivolts because of the diodes voltage drop.
I think you can dissipate most of the power on simple resistor before the regulator, which will limit the current and make some local feedback (with the voltage drop of the regulator ) and thus equalize the currents.
Connect two of theese in paralel, when the R is:
Lets say max current is 2.8A, voltage drop of the regulator 0.2V, the R will be (12-5.2)/2.8 =2.4Ohm

You may use few resistors in series.

 

[roy mathew]

Hi Why don't use switching regulator instead?

 

[Gundam001]

If you want to achieve high current by doing parallel connection, I think it is better to shift to a switching regulator which has a 5A above current rating.. this would have better response. Linear tech have a lot of this kind of regulators...