I have built my own power supply with lm2576 adj. & 3 Amp max load.. but it can't drive load current until 3 Amp max..
When I connect the 10 ohm resistor with 30 Vdc supply from the regulator.. it drops until 18 Volt.. and the load current becomes 1.8 Amp..
Why is it happen? it properly can drive until 3 Amp load current isn't it?
And one more, my inductor make creaking sound when I give the supply with that load.. Is it means that my inductor not enough able to handle the load current with bigger value?
which datasheet you referred i don't know.take look below test circuit its 100uh inductor there and try to find radio inductor i have same problems with chock type inductor as shown in your image.
I'm not an expert in switching voltage regulator, however i think you should check:
1. the current rating of the L1 inductor you are actually using
2. the stability of the input voltage when the load is applyed
3. the layout and the grounding of the board. These could by critical, once I experienced many problems due to bad layout (the component I used was different but the problems could be the same)
@electronion I believe you mentioned inductor current rating so I looked at the photo and found the part on digi-key library and it appears to be a TDK part which may be underrated for this 3A design.
I suggest a lower value of inductance ie 100 µH or higher rated current.