Author Topic: linear voltage regulator suggestion (Read 11966 times)

Cali-Sam · « **on:** July 14, 2012, 01:08:12 am »

can any body suggest a linear voltage regulator 0-15v and at least 3A current handling?
doesnt have to be exact. anything similar would work.
im trying to build a clean, riple free linear PSU for my tiny lab. too bad, i'm a poor bigenner, and i cant afford a pre-built one.

please help!!

ivan747 · « **Reply #1 on:** July 14, 2012, 01:16:51 am »

Try with the LM350, as it is available from many manufacturers.

Cali-Sam · « **Reply #2 on:** July 14, 2012, 01:32:09 am »

that sounds more like what i was looking for....
i faild to mention that i would need a negative voltage regulator with the same or similar spesifications as well. any idea??

alm · « **Reply #3 on:** July 14, 2012, 01:42:53 am »

The LM350 does not go below 1.25 V without introducing extra complexity. 3 A / 15 V without pre-regulator will also require serious cooling to get rid of ~55 W while keeping the junction temperature at a sane level.

Cali-Sam · « **Reply #4 on:** July 14, 2012, 01:55:22 am »

heat might be somthing i can deal with. i can add a CPU heat sync with a fan.... but i really want voltages below 1.2v.... any other regulator that can go below 1.2v.

notsob · « **Reply #5 on:** July 14, 2012, 02:40:39 am »

You may want a K version [T0-3 package] for better heat dissipation

ivan747 · « **Reply #6 on:** July 14, 2012, 04:50:37 am »

Quote from: alm on July 14, 2012, 01:42:53 am

The LM350 does not go below 1.25 V without introducing extra complexity. 3 A / 15 V without pre-regulator will also require serious cooling to get rid of ~55 W while keeping the junction temperature at a sane level.

I am prototyping a DC-DC converter pre-regulator for this regulator. I only have a 7805 and an LM337 on hand, though.

Simon · « **Reply #7 on:** July 14, 2012, 10:36:02 am »

you can do down to 0 volts but it complicates your circuit, the 1.25V limit is so because it is the reference voltage inside the chip. You need to play around with your regulators ground (0 reference) taking it under 0V by at least 1.25 so that when the reg thinks it is delivering 1.25 it is actually 0V

MikeNye · « **Reply #8 on:** July 14, 2012, 01:49:29 pm »

Hi Cali-Sam,

Have you had a look at Linear Technologies' LT3083?

This looks like a very good regulator which is the bigger brother of the LT3080 that Dave has done some videos about with the first power supply project book, except it handles 3A and has a slightly lower voltage range (0V - 23V). It is low dropout.

It is available in a TO-220 package, so perfect for breadboarding and easily mountable on a heat sink.

The data sheet even shows you a lab supply with current limiting as one of the application examples:

For your negative requirement, do you need dual tracking and a true earth reference? If not, could you not just reverse the output terminals when you need a negative supply?

I hope this helps you out!

-M

T4P · « **Reply #9 on:** July 14, 2012, 02:22:37 pm »

You should be ashamed to even call that a "lab supply" IT'S NOT!

Simon · « **Reply #10 on:** July 14, 2012, 02:29:46 pm »

Quote from: DaveXRT on July 14, 2012, 02:22:37 pm

You should be ashamed to even call that a "lab supply" IT'S NOT!

care to qualify that ? or are you firing off blanks again ?

digsys · « **Reply #11 on:** July 14, 2012, 02:51:46 pm »

Geeez, so much anal negativity .. LT make damn nice products. All it needs is a reverse OP to IP diode,
Zener OV clamp on the OP, followed by a polyfuse, Current and voltage meters and you end up with a
nice bench P/Supply quite cheaply. Just need to decide on the heatsinking.

Cali-Sam · « **Reply #12 on:** July 14, 2012, 05:10:35 pm »

Quote from: Simon on July 14, 2012, 10:36:02 am

you can do down to 0 volts but it complicates your circuit, the 1.25V limit is so because it is the reference voltage inside the chip. You need to play around with your regulators ground (0 reference) taking it under 0V by at least 1.25 so that when the reg thinks it is delivering 1.25 it is actually 0V

can you provide the schematic for that please!! i would be thankful.

Simon · « **Reply #13 on:** July 14, 2012, 05:14:56 pm »

I don't have a schematic to hand and it would need adapting to the specific regular. The topic is discussed in the book "the art of electronics"

alm · « **Reply #14 on:** July 14, 2012, 05:19:41 pm »

See the '0 to 30V regulator' application example in the National LM350 datasheet.

T4P · « **Reply #15 on:** July 14, 2012, 05:40:53 pm »

Quote from: Simon on July 14, 2012, 02:29:46 pm

Quote from: DaveXRT on July 14, 2012, 02:22:37 pm
You should be ashamed to even call that a "lab supply" IT'S NOT!

care to qualify that ? or are you firing off blanks again ?

Just ask FE!

Simon · « **Reply #16 on:** July 14, 2012, 05:42:12 pm »

Quote from: DaveXRT on July 14, 2012, 05:40:53 pm

Quote from: Simon on July 14, 2012, 02:29:46 pm
Quote from: DaveXRT on July 14, 2012, 02:22:37 pm
You should be ashamed to even call that a "lab supply" IT'S NOT!

care to qualify that ? or are you firing off blanks again ?

Just ask FE!

FE ?

darrylp · « **Reply #17 on:** July 14, 2012, 08:54:34 pm »

Free Electron?

Sent from my HTC Desire using Tapatalk 2

digsys · « **Reply #18 on:** July 15, 2012, 01:15:41 am »

Quote from: DaveXRT on July 14, 2012, 05:40:53 pm

Just ask FE!

That's all we'd need, another 200 post rant on how dumb everyone else is :-)

Monkeh · « **Reply #19 on:** July 16, 2012, 02:11:45 am »

Quote from: Electroalek on July 16, 2012, 02:07:41 am

I would recommend converting ATX power supply to LAB power supply. It hac 3.3V, 5V, 12V, -5V, -12V, and all about 10 amps.

An ATX PSU, especially the cheap crap usually butche^W converted, is not a lab supply. And they most certainly cannot provide 10A on -12V. Most don't even have -5V.

digsys · « **Reply #20 on:** July 16, 2012, 02:41:58 am »

Agree with Monkeh - besides this is a VERY dangerous path for a "beginner". Having had to repair 1 or 2,
I wouldn't go near these dangerous beasts unless Vitally necessary !!

Monkeh · « **Reply #21 on:** July 16, 2012, 02:45:02 am »

Quote from: digsys on July 16, 2012, 02:41:58 am

Agree with Monkeh - besides this is a VERY dangerous path for a "beginner". Having had to repair 1 or 2,
I wouldn't go near these dangerous beasts unless Vitally necessary !!

I've repaired and modified a few myself, never thought of them as dangerous. Take the same precautions you do around anything with mains charged caps in it and you'll be fine.

Mind you, I started with mains electrics long before playing with electronics.

Cali-Sam · « **Reply #22 on:** July 17, 2012, 02:19:09 am »

Can i wire two of the lm350 in parallel and double the current?

digsys · « **Reply #23 on:** July 17, 2012, 03:26:35 am »

Quote

.. Can i wire two of the lm350 in parallel and double the current?

Absolutely, check the application ccts for info. I am testing a 10X parallel prototype right now,
sharing is excellent. You can also use LM338 (5A) or LT1083 (7.5A), all work the same.

Cali-Sam · « **Reply #24 on:** July 17, 2012, 05:39:10 am »

LM338 is only a dollar each on ebay, packaged as TO-3. could this be fake?
as far as heat dissipation, efficiency, and performance ,which package is better To-3 or To-220?


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Author Topic: linear voltage regulator suggestion (Read 11966 times)

alm

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