Please can i confirm that this is a viable method for TL431/opto SMPS regulation with output voltage of 36V......................................
(The TL431 is only good up to 36V)
Hi. If voltage supply goes high enough, current from various sources will be higher than current that flows through R2, and in that case, the regulator might get more then 36V between kathode and anode. So it's not protected from overvoltage - if the voltage goes high enough.
Also remember that current cannot go in negative direction into a transistors emitter (hence the arrow). So one can easilly be fooled of this and think its proof enough. But it isn't.