Probably I will not use the power supply in constant current mode... I need only some protection for the PNP transistors which is available through the 2 1N5408 diodes.
The next question is: if I want to use a 100VA/24V transformer for this project, how can I be sure that in all situations, the output current will not be more than 3 A ?
I checked this way: the maximum current through LM317 is about 2.2A (maximum) and the current through the PNP's is about 1V/1.2R=0.833A. For 2 PNP's it is 1.66A. So the maximum output current will be 2.2A + 1.66A = 3.86A, but I am getting more than 3.86A when I have a overload at output. For example, I am getting 2.5A through LM317T ... and the total output current more than 4A...