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combo power supply of 5v/12v , 2a.

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anuradha bulakh

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I want to design 12v/5v ,2A power supply for my project.
Can I use 7805,7812 for this rating?
Also what should be transformer selection?
Can anybody provide me ckt.
 

Triple Power Supply
**broken link removed**
In "S3" section from the above link, if you think you'll need 2A (or more) current you can use a "trick" by connecting two voltage regulators in parallel, or just use an external power pass-transistor .. see attached picture ..

IanP
:D
 

How do you guarantee that two regulators in parallel will equally share the load? It seems a bit risky to me. If you need a 2A regulator, just buy one. If you want to stick to linear, the LM350 is 3A (although it is adjustable not fixed).

Keith.
 

How do you guarantee that two regulators in parallel will equally share the load?
At currents below their current limit they won’t – but who cares ..
Eventually, when the current of one of them becomes limited the other regulator supplies the rest, and off we go up to 2A ..
After all, heat is better distributed in two-1A regulators than in one-2A ic ..
Have you ever tried this “trick”?

Of course, you can buy 2A/3A or 5A regulators, but usually people have a few 7805s laying around and that’s the way they can be used ..

IanP
:D
 

IanP said:
How do you guarantee that two regulators in parallel will equally share the load?
At currents below their current limit they won’t – but who cares ..
Eventually, when the current of one of them becomes limited the other regulator supplies the rest, and off we go up to 2A ..
After all, heat is better distributed in two-1A regulators than in one-2A ic ..
Have you ever tried this “trick”?

Of course, you can buy 2A/3A or 5A regulators, but usually people have a few 7805s laying around and that’s the way they can be used ..

IanP
:D

So you rely on one overheating or current limiting for the current to be shared by the other?

Keith.
 

anuradha bulakh said:
I want to design 12v/5v ,2A power supply for my project. Can I use 7805,7812 for this rating? Also what should be transformer selection? Can anybody provide me ckt.
If you are looking for a construction project , you may go for the said one. Instead stuggling for transformers and constucting the regulators, you may directly us a PC ATX power supply which comes with more than 2A in both 12v and 5V
 

IanP said:
Have you ever tried this “trick”?

Well, I have just hooked up two 7805 regulators as you suggest and added a 3 ohm load. One regulator takes 1.3A, the other takes 0.4A. I will stick with using high current regulators when I need high current.

Keith.
 

Pranam

can you tell me what is exactly PC ATX? how much it costs?
 

anuradha bulakh said:
Pranam

can you tell me what is exactly PC ATX? how much it costs?
As you have mentioned your loaction as "Pune" it should be arround 350-500 Rupees for a brand new one or if you know your PC service fellow, get a old one for just 50-100 rupees. Thaz it. Cheers.
 

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