Voltage regulator in paralle

[Girishh]

Helloo Firends ....I need 5 volt 3 Ampere supply ..can i use 2 numbers 7805 in parallel to get more ampere..please suggest...i am waitin for ur valauable commecnts...

 

[Ice-Tea]

No, you can't. The tolerance between 7805 will cause huge inbalances in current. That's the best case. Worst case is that the control loop goes nuts even though I assume that to be rather unlikely with a 7805? I'm not an expert here.

In addition, depending on your application (ie input voltage), an LDO may not be a very good solution for a 3 amp application.

 

[rahdirs]

Helloo Firends ....I need 5 volt 3 Ampere supply ..can i use 2 numbers 7805 in parallel to get more ampere..please suggest...i am waitin for ur valauable commecnts...

From 7805,you can only get a maximum o/p current of 1 A.
But,if your input is capable of supplying more current,like in your case of 3-4 A(your i/p is capable of supplying 5 A right),you can use a pass transistor between the i/p & o/p pins of 7805.In your case using TIP 2955 as pass transistor maybe should do trick as they can allow a max.of 5 A.

The attached image is from datasheet of 7805,it shows how to do high current voltage regulation.
But if you need even higher currents,connect more pass transistors in parallel

 

[Girishh]

how the pass transistor ..increases the current..rating...can u please explainn ??

 

[rahdirs]

how the pass transistor ..increases the current..rating...can u please explainn ??

Say,your i/p was providing 5 A of current,but max.o/p current of 78xx series is approx. 1 A.
What the pass transistors do is they carry the extra current through themselves, with the output voltage being regulated by the 78xx.

Max.o/p current of 78xx is say, 1 A.Then the pass transistors carry the remaining (5-1)=4 A through them.

When using pass transistors,make sure transistor current rating can carry that extra current

 

[tpetar]

Voltage regulators:

7805 1A
78S05 2A
78T05 3A


Why to parallel voltage regulator, better use adequate part.

Also its possible to get higher current with other regulators or with external power transistor.




Best regards,
Peter

:wink: