to borber:
I think that I understood your explanation. But I'm wondering and it is also one problem that I encounter in pratical:
First, I assign the load resistance of 24 Ohm. It leads to the current 1A through the load. When I decrease the load resistance, The current flows through the load increase (of cause). When the load resistance reaches 6 Ohm. In theory, the fuse must shut down to protect the circuit and the load. But in fact, it does not. If the current flows through the load increase (from 1A up to 4A), it makes the U (CE) of the darlington (BC182 - BD241) increase (not as zero as designed) and it affect the output voltage, and current through loads (I think that the working points of these transistor drop into the active region (not cut-off or saturation region)).
The second problem is that: the thyristor does not grounds the Base of DARLINGTON (I use the type: NEC 5P4M)
so even when the Transistor BC182 (most right) does not open fully (Uce=0), the led lights because of current going through it into base of the DARLINGTON.
I'm now worried. I can't find any solution to these problems. I have been trying but my work does not preceed!
Someone, please help me.
(One think that: what does the role of this DARLINGTON here? is it used as electronic switch?)