1. The Resistor on the left is connected to limit the current flow through Cathode to Anode of TL431. How to select that resistor ( consider Vin varies form 200 V to 700 V )? It is given that Ika = 1mA -100mA? Suppose if I choose a resistor high enough to limit the current, say 500K. gives 1.4mA for 700V and and 0,4mA during 200V. So, Will it be functioning during 200 V? I am going for very high limiting resistance to minimize the power dissipation in TL431 as low as Possible.
2. And also I want to limit the current flow in NPN transistor, where should I place Resistor in collector terminal or emitter terminal ?
3.What is the need of the Capacitor Cathode and reference and How to select the Capacitance value? Could anyone please explain it ?