I am looking for a current limiter circuit for negative voltage -5V.
A small voltage drop is acceptable. There are two maximum current limit requirements, 5 mA and 50 mA. Some tolerance in maximum current imitation is understandable. The load current levels can vary from 0 to maximum current limit but the variation is slow for both current limits. Kindly share the circuit and explain how it works.

 

Sounds like a lab project. Is this school work?

"Small" conveys almost zero information. Maximum allowed voltage drop for each current range?

What power sources are available for the limiter circuit?

There are a ton of current limiter schematics on the innergoogle. Why not start with one of them?

ak

 

There are two maximum current limit requirements, 5 mA and 50 mA

Is that for the same -5V supply?
How do you want to change from the 5mA to the 50mA limit?

 

Yes the voltage is same -5V supply.

There will be two circuits. One for each max current limit requirement.

 

and how much current is current limiter allowed to consume?
if you can tolerate up to some 500mV variants with transistors will do just fine. for example using good old current mirror allows for very simple current limit. unless circuit is in limit, voltage drop is some 100-200mV (voltage V(n002,n005) is across Q2 and R2). replace R1 with 3.9 Ohm and you get 5mA version. for a really low voltage drop consider using mosfet with low Rds and low side current sensing (INAxxx or whatever).

 

I am thinking how the current limiter circuits in the standard linear lab power supplies works where we set the output voltage and leave the current consumption up to the load. The load can draw the current up to the maximum set current limit. Let's look at that circuit first regardless the requirement I mentioned. This may help to understand the current limiter basics.

 

same way... you have a reference, compare actual value to a reference, and apply limit if value is exceeded.
for example:


this was current sink which is what you asked for. just replace 5V+ with 0VDC and replace 0V with -5VDC