Could somebody please explain the operation of the attached diagram?
What I don't understand is how the TL431 keeps the MOSFET on when the input voltage is above the reference voltage. How is the MOSFET switched off when the voltage drops below the preset voltage? Will the value of the set cut-off voltage influence the working of the circuit? For example, can the reference voltage be set too low to be able to switch off the MOSFET?
I read through the datasheet, but it didn't help me understand this phenomenon. It did help me to choose my resistor values, though.