High Current - Page 2 - Electronic Circuits Projects Diagrams Free

hotwaterwizard · 9th August 2007, 01:26 PM

Quote:

Originally Posted by Oznog

Regulators CANNOT be put in parallel to increase their rating. One will usually end up taking all the current.

Hmmm, If this is completely true explaine these articles.

http://www.elecdesign.com/Articles/A...9270/9270.html

http://www.edn.com/index.asp?layout=...cleid=CA434875

http://www.edn.com/contents/images/72204di.pdf

audioguru · 9th August 2007, 01:43 PM

The article says that current sharing is poor unless resistors or diodes are added in series with the outputs of the regulators. The article says that current-sharing resistors cause a voltage drop of 1.5V at full load so the excellent voltage regulation of the ICs is ruined.

Hero999 · 9th August 2007, 09:17 PM

I'd just stick them in parallel (without any series resistors) if I were you.

Most voltage regulators lower the voltage and are protected from thermal run-away. For small loads the strongest regulator will source all the current, as the load current increases it will start to shut down and the slightly weaker regulators will provide the current.

mneary · 10th August 2007, 01:54 AM

I'd be concerned about the long term reliability of a regulator constantly in thermal limiting mode. If it's for hobby, might be OK - just keep curious fingers off the hot surfaces (they'll be around 100c). It's certainly expedient if you're just building one of them.

You might encounter stability problems which will be highly annoying if you don't have the skills to troubleshoot and fix.

Over the long term, you'll learn to design a proper power supply with an adequate heat sink. It might not be necessary to do it now.

mvs sarma · 11th August 2007, 05:45 PM

Hi Chandu,
did you really go thro the applications of 7812 fir high current with short circuit protection -- these are well described in the datasheet also. First priority if can source is LM350(TO3) as suggested by Hotwaterwizard-

if 7812 is preferred to be used, try to follw the high current application.
It is better not to go for paralleled regulators-drawbacks indicated by AudioGURU- and land into complication and non-comletion of the project.

Sarma

hotwaterwizard · 11th August 2007, 09:03 PM

L7812CV
What is wrong with the circuit on page 29 of the Datasheet?

Datasheet
CLICK HERE for Datasheet
Product Page
CLICK HERE Product Page

mvs sarma · 12th August 2007, 05:12 AM

Hi,

Fig22 indicated by Hotwaterwizard is fine and i was using one and it worked well
Sarma

9th August 2007, 01:43 PM	(permalink)
audioguru Experienced Member	The article says that current sharing is poor unless resistors or diodes are added in series with the outputs of the regulators. The article says that current-sharing resistors cause a voltage drop of 1.5V at full load so the excellent voltage regulation of the ICs is ruined. __________________ Uncle $crooge

9th August 2007, 09:17 PM	(permalink)
Hero999 Experienced Member	I'd just stick them in parallel (without any series resistors) if I were you. Most voltage regulators lower the voltage and are protected from thermal run-away. For small loads the strongest regulator will source all the current, as the load current increases it will start to shut down and the slightly weaker regulators will provide the current. __________________ What's so bad about Microsoft? Get Opera it's simply a superb browser.

10th August 2007, 01:54 AM	(permalink)
mneary Experienced Member	I'd be concerned about the long term reliability of a regulator constantly in thermal limiting mode. If it's for hobby, might be OK - just keep curious fingers off the hot surfaces (they'll be around 100c). It's certainly expedient if you're just building one of them. You might encounter stability problems which will be highly annoying if you don't have the skills to troubleshoot and fix. Over the long term, you'll learn to design a proper power supply with an adequate heat sink. It might not be necessary to do it now. Last edited by mneary; 10th August 2007 at 01:58 AM.

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11th August 2007, 05:45 PM	(permalink)
mvs sarma Experienced Member	Hi Chandu, did you really go thro the applications of 7812 fir high current with short circuit protection -- these are well described in the datasheet also. First priority if can source is LM350(TO3) as suggested by Hotwaterwizard- if 7812 is preferred to be used, try to follw the high current application. It is better not to go for paralleled regulators-drawbacks indicated by AudioGURU- and land into complication and non-comletion of the project. Sarma

12th August 2007, 05:12 AM	(permalink)
mvs sarma Experienced Member	Hi, Fig22 indicated by Hotwaterwizard is fine and i was using one and it worked well Sarma