Electronics > Beginners
LT3080 High Current Equivalent for 4 channel bench supply
(1/4) > >>
FotatoPotato:
Hello everyone,

Sorry if this topic has been previously addressed, but I'm in the process of building a 4 output Linear power supply and I want to use Dave's uSupply design as a reference.

In my design I have 2 low voltage, high current outputs (0 - 20v @0-5A each -- Call this channel A) and 2 high voltage, low(ish) current outputs (0-48v @0-2.5A each -- Call this channel B). I also want to make sure that I can put both outputs in either channel A or B in series or parallel to get more power if I ever need it. I already have 2 transformers for the supply, one 24v 11.6A one and a 48v 5.3A one. Now I just need to find a proper deign that can handle this power.

I was originally going to use this design for each of the 4 channels with an added capacitance multiplier filter to reduce noise: https://bit.ly/2pwLdjH

But the LM723's are wayy obsolete  |O and the only place I can find them is on ebay. So I was wondering if any of you guys know of a better design that I can use that will still fit my needs and that will give me the option to add a MCU for more accurate control later on if I ever feel like it.

Thanks  ;D
coppercone2:
I don't know if I would add a capacitance multiplier as a noise filter to a lab supply. Maybe to some op-amp rails in some kind of sensor or amplifier box.

But a good solution would be to use the LT3083 and its datasheet application notes, you can parallel them or mod them for high voltage operation.

Just test it first for stability on bad loads. It looks like you will need 2-3 LT3083's per 20V rail and 1 per each high voltage rail.

30$ of regulators for a 4 channel lab supply is not really that bad. Simple might be better because you just have 1 IC to replace if something fires, maybe 2. If you keep a few extra on hand and put them in the enclosure with some antistatic you can ensure uptime. Nothing worse then broken lab equipment.

or this obsolete thing
http://www.analog.com/media/en/technical-documentation/data-sheets/1038fa.pdf
FotatoPotato:
I did take a look at the LT3083 but the TO-220 versions are $10 a pop and If Im going to be using 8 - 10 of them then the cost will add up quickly. Is there any way to just use one and then add an external BJT to increase the power output capabilities and reduce the amount of them that I need to buy. I'm thinking something like this:

Also, How would I go about modding them for the high voltage operation. I'm assuming it would be the same as what I showed above but I'm not quite sure.

Anyway, thanks for the quick reply.  :)
coppercone2:
well you can also mod the lt3080 for high current, it has a diagram in the datasheet.

I think a transistor buffer is gonna be a bit quirky compared to 2 identical regulators in parallel but I won't do an analysis, you can probobly dig up dirt on both circuits though.

maybe use 2x of the lt3083's for the HV rails modded, then 2x lt3080's with transistor for the lower voltage rails

but scroll down in the datasheets for lt3080 and lt3083 and look at the schematics

also read the datasheet. THey have something like 80% match with good parts, meaning if you parallel them with a extra margin (cuz its a lab supply), you get like a 60% boost, so 3+0.6*3=4.8A

that means 6 lt3083s will do it, but thats 60$.

if you use the transistor load sharing circuit with the lt3080 you can get by using 2x lt3080 and 2xlt3083

reading datasheet carefully might tell you if lt3083 can transistor shared too. you can probobly also parallel them with the HV mod

Also if you parallel them I think you reduce noise by the square root of devices you add (has diminishing returns after like 4 that are pretty severe). DOn't know how to analyze the transistor one off the top of my head at this hour.
FotatoPotato:
Looking at the Datasheet for the LT3080 I saw this diagram (Linked Below). I will probably replace the MJ4502 with a TIP142 due to cost and the fact that it has a much higher gain that the original part. I'll definitely do this for the 2 low voltage outputs. I also saw that the LT3083 has a high voltage mod (again, linked below). So it seems as though my problems have been solved by just reading... :palm: (I should do that a bit more lol)

I do have some concerns about the High voltage part though because 48v AC doesn't translate to 48V DC. Its more around 68V DC with no load and about 60-65v at max load. so that will be a problem but I'll just have to do a bit more digging.

Thanks for the help, I really appreciate it. Hopefully things work out well and I can get to using my supply.

Thanks  :-+
Navigation
Message Index
Next page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod