Can I parallel two 7805 for greater current?

[neazoi]

Can I connect two 7805 regulators in parallel to increase the current?

Basically I need to supply 5v voltage (800mA) to a device and a 5v supply (800mA) to another device. It could be done with two regulators but the problem is that the two devices are connected to a common bus where there is only one VCC.

I have found this page High Current Voltage Regulation - Electric Circuit
but I would like to know if these circuits will work.

Also can I combine these?

 

[KerimF]

Can I connect two 7805 regulators in parallel to increase the current?

Basically I need to supply 5v voltage (800mA) to a device and a 5v supply (800mA) to another device. It could be done with two regulators but the problem is that the two devices are connected to a common bus where there is only one VCC.

Preferably, it is better to use 7805 with a pnp power transistor that handles the large current and power dissipation.
As a first step, do you have an idea about the possible maximum and minimum voltages at the regulator input @1600mA?

 

[kak111]

I recommend to use 3A-5V regulator LM323 or eq. type in TO220 case
and high enough cooling capacity.

IC is same size only larger cooling plate.

http://www.datasheetcatalog.org/datasheet/stmicroelectronics/2165.pdf

Parallel connected power sources are many ways troublesome

Regards KAK

 

[IanP]

Connecting two (or more) voltage regulators in parallel is not a good idea ..
As usual, you have several options: bigger regulator (2A or 3A rating), external PNP power transistor or –
just by cutting somewhere the Vcc track separating these two devices and supplying them from two separate (sharing only common) voltage regulators ..

:wink:
IanP

 

[davenn]

The reason that its a bad idea is commented on in the text of your link. Variations in voltage regulation between the different regulator chips will lead to one chip passing more current than the other one. That eventually, will most likely cause failure of that chip, that in turn will mean that the other chip will carry all the load and will promptly fail.

as the others have suggested use a current pass transistor, a higher current rated reg chip, or even better yet, use a DC-DC buck converter chip they are so so much more efficient and as a result dont run very hot like the LM78xx series.

Dave