Discussion: Use a TL431 shunt regulator to limit high ac input voltage

[Radiolocman Robot]

Todor Arsenov EDN Most isolated, offline SMPSs (switched-mode power supplies), including flyback, forward, and resonant, must operate at input voltages of 90 to 260 V rms. Some cases even use line-to-line voltages of 400 V rms±10%, leading to increased component-voltage ratings and, thus, increased cost of the overall design.

More: Use a TL431 shunt regulator to limit high ac input voltage

[Dr Panda]

Hi, new here and new to the tl431. Most of your writing is clear, but two questions.
The 15v zener D2, it also does the tl431 protected for voltages above the max 36V, not only about the Q1?
Is the C2 for eluminate spikes or…? And how do you calculate the value?
Thank you for your articles and time.