LM338 Power Suply Current Regulator

[Fight]

Hello Hero and audioguru
how r u
where are you in these days since about 2 weeks
i am waiting you
please come on internet and solve my problem

 

[audioguru2]

Your problem is that your high supply voltage range and high output current will cause the LM338 current regulator to reduce its max current  to only 1A and overheat.

If the LM338 current regulator has an input voltage of only about 13.2V then it can supply a max current of 5A when the LM338 voltage regulator has an output of 1.2V. Even then, the LM338 current regulator will dissipate 50W which is a lot of heat to remove.

 

[Hero999]

We will help you to solve your problem but we won't do it for you.

 

[Fight]

Hello Hero and Audioguru
how are tou

The LM338 will only overheat after the current limit has kicked in, before then the voltage across it will be between 1.5V and 3V, depending on the current and ambient temperature.

if i add a circuit that prevent short circuit then this problem solved or not

 

[audioguru2]

if i add a circuit that prevent short circuit then this problem solved or not

No because your input supply voltage is too high and the LM338 current regulator will overheat when it regulates the current between 1A and 5A and when the output voltage is set low.

If the input voltage is 38V, the current is set to only 1A and the output is set to 4.75V then the LM338 current regulator dissipates 30W. How will you cool it?
It probably will not supply a current as high as 1A when it has 30V across itself because that is its max current.
When it overheats then it shuts down and does not work until it has cooled.

 

[Hero999]

I don't know if your problem has been solved or not because I don't know what it is.

It depends on whether you need current regulation or just current limiting. Adding another LM338 is fine, if you just want to limit the current but is no good for regulation. Note there is a big difference between a current limiter and current regulation: the former just shuts down when the current limit is exceeded, the latter will keep the current constant, even if the output is shorted to 0V.

 

[Fight]

Hello Hero and Audioguru
how are u
i sure that both are well
ok next
Hello Hero
in other threat named "Switch mode power supply" you tell me that if you buy a 12V 200W smps then you add a circuit for making power supply 0-30 and 0-5A variale voltage and variable conatant current power supply.

If i buy PC P-4 PSU then this psu use as a primary 12V 200W smps first tell me that

How idea

and how can add a circuit please if you have a spare time then send a diagram using IC (SG3524) beacause this IC is avail in our country easily.

 

[Fight]

thanks
very very thanks a lot  :  ???

 

[Kevin Weddle]

Hero99, are you a moderator?

 

[Fight]

Hello KevinIV
who are you

Hero99, are you a moderator?

Hero not a moderator but
is a brilliant man
and my friend

 

[exerion]

i have read this post recently but i can't understand the comments (very interesting), because i can't see the circuit they are talking about.

where is it? is it possible to post again? I know the topic is old but the info is good for me, super newbie

Cheers

 

[audioguru2]

i have read this post recently but i can't understand the comments (very interesting), because i can't see the circuit they are talking about.

where is it? is it possible to post again? I know the topic is old but the info is good for me, super newbie

The schematic is attached as a thumbnail in the first post. Click on the thumbnail to enlarge it.
The schematic is copied from the datasheet of the LM338 IC.