Series Voltage regulator

[BayHitchi]

Hello people, im a begginer in eletronics and my first project is a series voltage regulator with overcurrent protection. For some personal reasons i coud not attend school for some weeks, so im pretty lost in transistors and regulators. I dont ask for anyone to just do it for me, but if ayone could help me out understand how/why to project it woul be amazing!
 
 I just have to project the values of all resistors, V(in)max and V(in)min, in this circuit.
The target V(out) = 12v and max current = 1A.
 

[Seekonk]

At what voltage will the transistor turn on, then solve for resisyance.

[not1xor1]

Hello people, im a begginer in eletronics and my first project is a series voltage regulator with overcurrent protection. For some personal reasons i coud not attend school for some weeks, so im pretty lost in transistors and regulators. I dont ask for anyone to just do it for me, but if ayone could help me out understand how/why to project it woul be amazing!
 
 I just have to project the values of all resistors, V(in)max and V(in)min, in this circuit.
The target V(out) = 12v and max current = 1A.

Tr2:
as soon as the base voltage (ouput voltage divided by the R1+VR1+R2 divider) gets above the zener voltage plus Vbe, Tr2 reduces the base current of Tr1, while it does the opposite if the voltage gets below the reference (Vzener+Vbe).
In other words, Vzener + Vbe is the input signal, while the base of Tr2 gets the feedback signal and adjust the amplification of Tr1 in order to keep the output voltage constant.

Tr3:
as soon as too much current goes through R5 (i.e. I * R5 >= Vbe), it "steals" some base current from Tr1 limiting the output current.
If the current is below that threshold (it is a soft knee) Tr3 does nothing (it is off).


knowing all the parameters (voltages, transistor features, etc.) you can easily calculate all the resistor values