Hi everyone,

I'm trying to make a shortcircuit protection with current limiter. I wanted to use a simple circuit with 2 transistors to limit the current when it's short circuit and open a mosfet as switch with a microcontroller. But the voltage drop after the transistor is like 2 volts. So are there any solutions or other circuits that i can use instead of this? I want it to be as small as possible.

 

I forgot to say that the output has to be 40 Watts

 

You really need to supply more info.
What is the voltage?
AC or DC?
Operating speed?
And why not use a Polyswitch?

 

You really need to supply more info.
What is the voltage?
AC or DC?
Operating speed?
And why not use a Polyswitch?

The voltage is 24V.
It's DC.
I want it to be able to react immediately so it won't destroy any components. I've never heard of a Polyswitch so i didn't even know that it exists. But from what I've found it reacts to heat and i don't think it will react fast enough. Meanwhile I've been searching for something with a mosfet instead. And i found this:
I've simulated this myself on LTSpice and it worked. Is this a good circuit to limit the current?

 

I've simulated this myself on LTSpice and it worked. Is this a good circuit to limit the current?

It appears to work, but what is the reference for the current limit?
You need a reference voltage to compare with the sense resistor voltage to generate a stable current limit.
What does V1 represent?

Below is the LTspice simulation of a simple current limit circuit if you can tolerate about a 0.7V maximum drop up to the limit.

Would you be interested in an electronic fuse type circuit that shuts the current off when the limit is exceeded and then has to be reset by removing power or pushing a reset button?