Hello! In the above referenced schematic, Q5 and R20 look to form a simple depletion mode current source. I am having trouble understanding how the TPS40210 Boost Controller IC becomes disabled with input voltages greater than 355VDC as referenced in the text (Page 6 - bottom). Doesn't the current source provide a constant current regardless of the input voltage? How does a certain input voltage disable the boost controller? Thank you for any insight.