Hello, I am trying to create linear regulator that can output 48V and 2A current with maximum current being 2.2A which after that the short circuit current protection is triggered.

I couldn't find any regulators that have build in current protection that high or current protection that can be controlled so I searched for circuits that can help me and found this configuration made from Q2, R3, R4, R5 which should lower the output current and voltage to a calculated short circuit current Ish.

I am not certain if the configuration I have done will even work because this protection is supposed to go to the output of the regulator's amplifier but here it goes to the input of the common collector NPN.

The other components (Q3, Q4, R6, R7, R8, R9) should help me with achieving higher output current because the regulator is only rated for 250mA but I am not certain about them either.

 

Please post your SPICE file. One of us might play with it.
I see how Q3 can work. OR I see how Q1 could work. I don't see a need for both.
The LT3012 can output 250mA (from memory) might be wrong. To get 2.2A from a transistor there only needs to be a gain of 10.
The way this current limit works is to short out B-E of the pass transistor. This causes the IC to work very hard. I have done this many times. I have not tried it on this part but there might be a way to use the /shutdown pin to reduce the current. It might not work well.

 

Please post your SPICE file. One of us might play with it.
I see how Q3 can work. OR I see how Q1 could work. I don't see a need for both.
The LT3012 can output 250mA (from memory) might be wrong. To get 2.2A from a transistor there only needs to be a gain of 10.
The way this current limit works is to short out B-E of the pass transistor. This causes the IC to work very hard. I have done this many times. I have not tried it on this part but there might be a way to use the /shutdown pin to reduce the current. It might not work well.

Yes of course here is the file.

I didn't think about the SHDN pin. Completely forgot about it I will try some experiments with it as well!

By saying it makes the IC work really hard you mean that it passes high current through it?

 

Here is it almost working. Vout is about 14V as set by R1, R2. RL set to 1A
R3C2 makes it start up slower. At first, I had problems getting it to start.
The current limit does not work well. R4 measures the ground current. When there is 0.6V across R4 Q2 pulls down on the /SHDN pin. Right now, it does not work well. I have it set to 0.01 ohm to disable the current limit.

Play with it. I don't have time right now.
RonS