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LM338: 0-5A variable current power supply design

Rahul Bhagwat
Prodigy 190 points
Part Number: LM338

I want to design 0 - 5 A variable current supply using LM338 regulator. I am giving 12V dc input from SMPS of 350 watt.

I am interest only in the variable current circuit design.

Kindly help me.

  • 0
    TI__Mastermind 22610 points

    Hello Rahul,

    Is there a particular reason that you need to use a linear voltage regulator, such as LM338, for current limiting? Personally, I would think that a discrete solution might be better way to go.

    In any case, in the LM338 datasheet see : Figure 42. Adjustable 15-A Regulator

    That figure can be used as a concept. You will need to scale R values to whatever are appropriate to your target design.

  • 0 in reply to Donald Jones
    Prodigy 190 points

    Hello Donald,

    Thank You for your quick reply. 

    Actually I want to design Battery charging circuit which will control the charging current. As I don't have much experience in Power supply design my colleague suggest to do variable current design using LM338 first, So that why I start with LM338.

    I already started with 5A variable current  sample circuit given in datasheet. I did the simulation in Proteus and It is working fine. I am able to control the output current. I will do it on actual hardware soon. Lets hope it will work as expected. I will also try for 15 A circuit design.  

    You mention discrete solution is better way, can you send me any link or any thing where I can find little guidance about designing using discrete components?

  • 0 in reply to Rahul Bhagwat
    TI__Mastermind 22610 points

    Rahul,

    A GOOGLE search of "variable current limit circuit" (or some variant) will give millions of hits (>87 million).

    You can then view the articles or circuit images, then go to the page if a circuit image looks interesting enough. You will probably need to sort through a lot of junk to find a circuit that works for you. But, along the way you will pick up some ideas that you might not have thought about.

    Best of luck!