[SOLVED] Adjustable Constant Current / Constant Voltage supply

[superdiy]

Hi,

I'm trying to build an adjustable constant current / constant voltage power supply using a LM2576. I need to adjust the voltage to approximately 24V and then set the current limit between 0 and about 4A. I preferably want to use a op-amp which will work on a single supply, like a LM358, because I do not want to add a split power supply to the project. I have tried a lot of different circuits, but all of them still "limits" the current (and bring down the output voltage), without any load connected to the circuit and thus without any current flowing through the shunt resistor???

I have based my circuit on the following design I've found on the forum, but the circuit in this image makes use of op amps connected to a split supply and would therefor not work correctly in my case.



It must be able to work similar to the following item:
1~35V DC 25W Power LED Driver Supply LM2596 CC CV

Any help would be greatly appreciated.

 

[alexan_e]

Constant current and current limit are two different thing,
in constant current you don't set the output voltage, it is automatically adjusted to provide the desired current to the load,
on the other hand in the current limit you set the voltage and there is a limiter that doesn't allow the load to get more current that the specified one.

So in your post you describe two different things, which one do you want?

I'm trying to build an adjustable constant current / constant voltage power supply using a LM2576. I need to adjust the voltage to approximately 24V and then set the current limit between 0 and about 4A

Alex

 

[superdiy]

Yes, sorry, I need CURRENT LIMITING! I need the voltage to stay at the set voltage (24V), unless the current drawn by the load tries to exceed the pre-set current - only then the voltage may start to drop ensuring that the load does not draw more current than the pre-set limit.

 

[alexan_e]

Check this thread https://www.edaboard.com/threads/77200/

Alex

 

[superdiy]

Check this thread https://www.edaboard.com/threads/77200/Alex

The image in my original post is taken from that thread - the op amps in that circuit needs split supply - I need them to work from single rail supply, therefore that circuit will not work.

 

[superdiy]

For anybody interested - here is the solution I was looking for. Unfortunately I don't have any CAD application which I could use to draw the circuit, but I think it is clear enough.