I have a voltage limiter/current shunt that when the power supply input is current limited to 1/2A or less the TL1431 will shunt the entire 1/2 A and drop the power supply voltage to 8V. If I power on the supply with the current limit above 1/2A the ckt will not shunt until Vin is > 34V (the designed value) where it regulates correctly. I can power on the supply with curent > 1/2A then drop the current and the shunt will still operate properly.
Any Idea as to the cause?