Current limiter low voltage drop
Reasons why I would reject this design by Sajjad Hajdar, technologist at UBC Apr 18, 2016


There are no design specs for Input voltage range, Ripple , PSRR, Vout ripple heat loss, Temp rise, 
There is no apparent need for Opto-isolation.
There is no need for a CCR to bias a Zener to power the LED current.
There is no OTP
There is no mention of Cap ESR limitations for phase margin stability. 
There are hundreds of MOSFET LDO's in stock everywhere. that do this already.


It might have been interesting 40 years ago as a Magazine Design Tip, but obsolete news today.