Adjust current with LM350

[gnlinuz]

Hello all, i am wandering how to adjust just current using LM350 (Not limiting). There are some schematics on the lm350 pdf file using a variable resistor at the output. I am newbie but i understand that all the current must flow through that pot, which i think is not a good idea (for 3A). Is there any other way to do it?? I hope i can drive the LM2576 to build an adjustable voltage - current power supply. Thanks all.

[David Hess]

The LM350 is just a 3 amp version of an LM317 which is much more common so any circuit designs you find using the LM317 apply just as well to the LM350.

There are some schematics on the lm350 pdf file using a variable resistor at the output. I am newbie but i understand that all the current must flow through that pot, which i think is not a good idea (for 3A).

Yep.  This works for low current fixed current regulators but not so well over a wide range unless you use a high power potentiometer.

Is there any other way to do it?? I hope i can drive the LM2576 to build an adjustable voltage - current power supply. Thanks all.

Adding a current regulator to the input or output of a switching regulator using just an LM350 is not going to work well at all.  The way to go about this is to use separate external current and voltage control loops.

The simplest adjustable current limit using an LM317 or LM350 looks something like the beginning part of this schematic:

http://powersupply88.com/variable-power-supply-with-adjustable-current-limit.html/variable-power-supply-with-current-limit

I would replace the JFET current regulator with a precision bipolar based current sink and drop the two diodes which are no longer needed (or replace them with a 1.25 volt shunt regulator) but that is the general idea.  The current sink develops a voltage across the potentiometer which adds to the voltage across the current sense resistor as far as the regulator is concerned so it lowers its output so the voltage across the sense resistor drops which lowers the output current.