Hi,
I can´t see how a resistor in series with the input can help to protect something - in combination with a flyback SMPS.
Can you explain - and how did you calcualte the value.
I assume you don´t understand flyback input current vs input voltage behaviour:
--> The lower the input voltage, the higher the input current.
The higher the input current the higher the voltage drop across the resistor and thus the power dissipation of the resistor.
I assume instead of "protecting" anything with your resistor ... you increased the risk of fire.
Either
* use no doubtful "protection" at all, because the datasheet of the TOPSwitch-HX already shows protection features:
The TOPSwitch-HX Family also enables the design of power supplies with robust functionality and provides enhanced safety features such as output overvoltage protection, overload power limiting and hysteretic thermal protection.
.
* Or use a true protection device like a fuse.
In either case you have to follow the datasheet recommendations very strictly. Especially the part (value) selection and PCB layout.
Klaus