Author Topic: linear voltage regulator suggestion  (Read 10070 times)

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Offline Cali-Sam

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linear voltage regulator suggestion
« 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!!
 

Offline ivan747

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linear voltage regulator suggestion
« Reply #1 on: July 14, 2012, 01:16:51 am »
Try with the LM350, as it is available from many manufacturers.
 

Offline Cali-Sam

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Re: linear voltage regulator suggestion
« 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

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Re: linear voltage regulator suggestion
« 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.
 

Offline Cali-Sam

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Re: linear voltage regulator suggestion
« 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.
 

Offline notsob

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Re: linear voltage regulator suggestion
« Reply #5 on: July 14, 2012, 02:40:39 am »
You may want a K version [T0-3 package] for better heat dissipation
 

Offline ivan747

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Re: linear voltage regulator suggestion
« Reply #6 on: July 14, 2012, 04:50:37 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.
 

Offline Simon

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Re: linear voltage regulator suggestion
« 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
 

Offline MikeNye

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Re: linear voltage regulator suggestion
« 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
« Last Edit: July 14, 2012, 01:56:06 pm by MikeNye »
 

Offline T4P

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Re: linear voltage regulator suggestion
« Reply #9 on: July 14, 2012, 02:22:37 pm »
You should be ashamed to even call that a "lab supply" IT'S NOT!
 

Offline Simon

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Re: linear voltage regulator suggestion
« Reply #10 on: July 14, 2012, 02:29:46 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 ?
 

Offline digsys

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Re: linear voltage regulator suggestion
« 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.
Hello <tap> <tap> .. is this thing on?
 

Offline Cali-Sam

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Re: linear voltage regulator suggestion
« Reply #12 on: July 14, 2012, 05:10:35 pm »
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.
 

Offline Simon

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Re: linear voltage regulator suggestion
« 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

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Re: linear voltage regulator suggestion
« Reply #14 on: July 14, 2012, 05:19:41 pm »
See the '0 to 30V regulator' application example in the National LM350 datasheet.
 

Offline T4P

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Re: linear voltage regulator suggestion
« Reply #15 on: July 14, 2012, 05:40:53 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!
 

Offline Simon

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Re: linear voltage regulator suggestion
« Reply #16 on: July 14, 2012, 05:42:12 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 ?
 

Offline darrylp

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Re: linear voltage regulator suggestion
« Reply #17 on: July 14, 2012, 08:54:34 pm »
Free Electron?

Sent from my HTC Desire using Tapatalk 2
 

Offline digsys

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Re: linear voltage regulator suggestion
« Reply #18 on: July 15, 2012, 01:15:41 am »
Just ask FE!
That's all we'd need, another 200 post rant on how dumb everyone else is :-)
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Offline Electroalek

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Re: linear voltage regulator suggestion
« Reply #19 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.
 

Online Monkeh

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Re: linear voltage regulator suggestion
« Reply #20 on: July 16, 2012, 02:11:45 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.
 

Offline digsys

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Re: linear voltage regulator suggestion
« Reply #21 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 !!
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Online Monkeh

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Re: linear voltage regulator suggestion
« Reply #22 on: July 16, 2012, 02:45:02 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.
 

Offline Cali-Sam

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Re: linear voltage regulator suggestion
« Reply #23 on: July 17, 2012, 02:19:09 am »
Can i wire two of the lm350 in parallel and double the current?
 

Offline digsys

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Re: linear voltage regulator suggestion
« Reply #24 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.
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Offline Cali-Sam

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Re: linear voltage regulator suggestion
« Reply #25 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?
 

alm

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Re: linear voltage regulator suggestion
« Reply #26 on: July 17, 2012, 05:54:24 am »
TO-3 has a lower thermal resistance to the heat sink, but is larger and usually more expensive. It's also harder to directly mount on a PCB. Hence the popularity of TO-220 (and similar packages like TO-3P). TO-3 would require a (slightly) smaller heat sink due to the lower thermal resistance. Performance and efficiency would be identical if the junction temperature is the same.
 

Offline shebu18

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Re: linear voltage regulator suggestion
« Reply #27 on: July 17, 2012, 05:58:02 am »
Why not use the LT1083 instead. It also has a 1.25V minimum voltage but is rated to 7.5A
 

Offline Cali-Sam

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Re: linear voltage regulator suggestion
« Reply #28 on: July 17, 2012, 06:07:10 am »
where can i buy the LT1083 from? and how much is it?
 

Offline digsys

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Re: linear voltage regulator suggestion
« Reply #29 on: July 17, 2012, 06:35:23 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?
YIPES, that sounds like bad silicon, IF it's NEW. There are some trusted places where I buy surplus lots,
usually quite cheap. eg   www.x-on.com.au     Search your part # and check ALL the hits.
If you're not doing production, TO3 is better thermally plus larger transfer area (as suggested).
In production, it's a pain in the ass, which is why I'm designing them all out of a product range, too much labour.
The LT1083 also comes in a TO264 package, which is my MOST favourite package for assembly !!!
They are much dearer than LM338s, but an awesome regulator. Check X-ON
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Offline Cali-Sam

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Re: linear voltage regulator suggestion
« Reply #30 on: July 17, 2012, 08:06:06 am »
this might sound strange!!!
i was thinking about dumping my voltage regulator in a small contater filled with car engine oil instead of ataching a heat sink... is engine oil an insulator?
forgive my ignorance, im just trying to come up with better solutions.
 

Offline digsys

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Re: linear voltage regulator suggestion
« Reply #31 on: July 17, 2012, 12:41:11 pm »
Quote
this might sound strange!!! i was thinking about dumping my voltage regulator in a small container filled with car engine oil
instead of attaching a heat sink... is engine oil an insulator?  forgive my ignorance, im just trying to come up with better solutions.
They do that for seriously large transformers and similar units that have large surface area. You can't use any oil,
you'd have to check specs (google will tell you). But for small devices, you have no hope. Practicalities of containment and sealing,
just a lot of effort for little value. Besides, the MOST important spec is how FAST you can get the heat away from the regulator.
If you want to try it, go for it, practical is the best way to learn. The theory itself is fine.

Added: Some of the new EVs are cooling their Lithium battery packs with liquid !! ie Tesla etc Actually pumping it OVER the 44-66
lithium cells @ 180-280VDC 100-300A. We're still considering it ... lots to worry about :-)
« Last Edit: July 17, 2012, 01:54:22 pm by digsys »
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Offline SeanB

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Re: linear voltage regulator suggestion
« Reply #32 on: July 17, 2012, 03:38:55 pm »
Using transformer oil to remove heat will work, but you will need to still attach a heat spreader to the device, and arrange the oil to flow past it. Otherwise it will just cook. You can try using a flat aluminium plate to increase surface area, and keep it vertical to assist convection. Then you will have to keep the oil cool.
 


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