Problems with lm2576

[noirs]

Hello!

I'm trying to make an adjustable lm2576 circuit where I can change the output with a pic and two transistors. But when I try it in real life it doesn't regulate the current. When I use 24 V on the input it just goes through and I get 22,4 V on output when I should have 12 V.

 

[D.A.(Tony)Stewart]

If both FETs are on Vo=1.23 (1+R2/R1) where R2=5k and you have two FETs + R1s , 571 and 501 ( both // = 267R )

1) 1.23 (1+5k/571) =12.0V
2) 1.23 (1+5k/267) = 24.2V err.

Is it possible both FETS are active? What is Vfeedback?

 

[IanP]

Hello!

I'm trying to make an adjustable lm2576 circuit where I can change the output with a pic and two transistors. But when I try it in real life it doesn't regulate the current. When I use 24 V on the input it just goes through and I get 22,4 V on output when I should have 12 V.

Try this circuit as if it were a stand-alone unit, see attached picture ...
Once you're satisfied, connect it to Arduino.
:wink:
IanP