Adjustable Current Limit for Power Supply

[tjalps]

Hello!

I'm searching for solution on adjustable current limit for DC power suply(SMPS). Do you now for any good acurate solution for currents up to 5Amps and voltages to 50V?

Regards!

 

[Moss]

You must see app note for LM317. look here

 

[VVV]

Use a shunt, about 20mΩ. If you can, install it in the return path. An opam with an adjustable reference will take over the control loop when you hit current limit.

If you cannot put the shunt in the return path, you can use a differential amplifier, but the accuracy won't be as good.

If you can post part of your schematic, I can suggest something.

 

[tjalps]

Hello!

i'm using simple switcher LM2678 from National Semiconductor. Mayebe you can propose something to original schematic. I'd like to adjust current limit digitaly with uC.

Regards!

 

[IanP]

The only type you can use in this application is the LM2678-ADJ.
If your microcontroller doesn't have DAC you can use digital resistors (for example fro Maxim-IC: **broken link removed** ).

You will need two opamps which outputs will be connected through diodes (OR function) to the ADJ input of the LM2678. One will control voltage, the other will look after current limit ..

Some time ago I did similar project using LM2576-ADJ .. it worked well (if it didn't I would have heard from the user by now) ..

 

[omore]

May be that if U bring some schematic of your circuit, you will receive more useful help because there are lots of solutions and almost impossible to enumarate them

 

[zhi_yi]

from the schematic above, please tell me what is the function of C2, C5 and C6 ?

thank you for all of your helps

 

[mkbtam]

c2 and c6 are used to reduce noise with the pots and c5 provide additional stability to the opamp.

 

[TobyB]

Elegant PWM approach to adjusting the voltage control of a switch mode

http://www.analog.com/static/imported-files/application_notes/EE-339.pdf

Also possible to use PTC resistor + resistor in parallel to limit current linearly

PTC Applications

 

[TheLaw]

The only type you can use in this application is the LM2678-ADJ.
If your microcontroller doesn't have DAC you can use digital resistors (for example fro Maxim-IC: **broken link removed** ).

You will need two opamps which outputs will be connected through diodes (OR function) to the ADJ input of the LM2678. One will control voltage, the other will look after current limit ..

Some time ago I did similar project using LM2576-ADJ .. it worked well (if it didn't I would have heard from the user by now) ..

Hi,

I know this thread is about 6 years old. I'm sorry to bring it back, but I plan on building a bench LM2576-adj, and I was curious about how to get adjustable current...Do you by chance have the schematic for the adjustable current section? Or does anyone else?

Thank you very much.