5 x LM338K

[moutouloss]

If I put 5 x LM338K (5A) parallel (like the circuit), I will have 25A power supply :?: :?:

 

[audioguru]

I answerered you today on the other electronics chat site!
Please don't post the same post on different sites.

 

[justDIY]

I like this idea for high current power supplies ... but I haven't had the stones to build one myself

40 amps for $25:
https://www.antennex.com/preview/archive3/powers.htm

 

[evandude]

yes, you should be okay to parallel them like that since the schematic shows the use of series resistors on the output of each regulator. That keeps the regulators (which will all try to keep the output at slightly different voltage levels) from fighting each other, which would cause one of them to take far more current than the rest and blow itself up. however, it does require lots of bulky power resistors, and they are going to be wasting power as heat, so you will be reducing the already not-so-great efficiency of linear regulators... but if you don't care about the efficiency, and can handle the heat generated, it should work for you...

 

[audioguru]

In his other post he showed a 40V input and an adjustable output voltage from 0V to 30V @ 25A.

The LM338's minimum output voltage is 1.25V and at 25A the regulators must dissipate 194W each! You would be lucky if they could dissipate 50W each.

A switching voltage regulator is needed.

 

[moutouloss]

I answerered you today on the other electronics chat site!
Please don't post the same post on different sites.

:shock: I believed that is prohibited double post in same site. What is your problem ?. Does exist concrete rule that reports what you say?. Moreover this is the aim of forum, says each one the opinion - his experience and the final decision belong to me, for the manufacture of circuit. If it were we only wait for your own answer it would be better to close the subject without second opinion.
The prohibition is to double post in same site not in a different one, that am member so are you, and this I don’t believe it teases you.Therefore the post can be seen from others that might have the same query with me.

In his other post he showed a 40V input and an adjustable output voltage from 0V to 30V @ 25A.

And what does it mean?. :? It is prohibited I also make a second power supply (I explain in the other site why I make it). What does it means "In his other post he showed a 40V..." I don’t appear with double personality or laught anybody. Are you crazy ????. I believe i am very reliable as i am the only one that appears with my name and my photo. I do not understand this unverbalized attack against me, I haven’t insult anyone, i just made a question as all the other users. And as you are also user in a lot of electronics sites so am I.

I apologize from the administrator - moderator, of web page for the post that I put in an irrelevant point, but I believe I have right to be mad :x , and I ask from Audioguru to apologizes to me for his behavior, because even if he is strong member of the forum that don’t gives him the right to behave like that.
Audioguru... I will accept your answers but I don’t accept your behavior. I imagine you took it selfish that I asked for a second opinion.

 

[audioguru]

Moutouloss,
I am upset that people on this post don't see your posts on the other site that lead up to this one.

You posted the schematic of a PSU that you said burned when its output was shorted. You claimed that it was rated at 0V-30V at 20A. But on another post you said you were using a 13.8V PSU for testing high-power car amplifiers and it didn't even get hot. Maybe it was this PSU, but probably hardly ever at its full 20A output.
I explained to you that it was the 800W of heat that burned the PSU when its output was shorted.

Then you asked if LM338K regulators could replace the power transistors in the original PSU. Then you asked the same question here, and some people here didn't realise that they would dissipate power way more than their rating, just like the transistors tried to do.

 

[audioguru]

Actually, the LM338 is smart.
In your circuit with its 40V input, if the regulated output voltage is 10V or less, the LM338's will have 30V or more across them and their datasheet guarantees that they will reduce their output current to no more than 1A each to protect themselves.
They are also smart because they shut-down when they get too hot. :lol:

 

[moutouloss]

Audioguru

Don't confused, I using this power supply (with LM723 - 2N3772) like bench (laboratory) to test several circuit (0-30V), and the same power supply for test in audio amplifiers (after repair) in 12-13.8V if it is function well.

With LM338K is a different construction, and I want to made it for second power supply. I don't say it to replace power transistor (with LM338K).

Finally thank's for answer.

 

[audioguru]

Hi Geg,
I hope you understand why the transistors burned in the lab supply when its output was shorted or if its output voltage is less than about 25V at 20A, or if its output voltage is set low with an output current more than about 7.7A. When the transistors are replaced with new ones, I hope you understand that they will burn again.

In the supply that you plan to use LM338K paralleled regulators, I hope you understand why they reduce their output current with more than only 10V across them.