Thanks for the reply.

Well, the power supply is correct with the P-channel fet. If you check the op-amp configuration the more Vout the less T1 drive. So the Mosfet will conduct less also having R1 at Vgs that is bringing mosfet closer in cutoff.

The regulation and in general the operation of the circuit is great.

You may think of the P-channel as a current source, regulated by T1.

Only problem is that when the protection is connected,, the mosfet is cutoff. If collector of the PNP or NPN is disconnected, everything works fine (except protection of course).

The base resistor will be added. Good point. But right now the problem is why the 10K does not stop the operation but connecting a small signal transistor that is OFF, does...

Ioannis