My question is, please can you say if the dimensioning of the timing capacitor (off pin 1) (which sets the pulse transformer driver switching frequency) depends on the input voltage ?
-the uc3901 can have an input voltage from 5 to 40V, and the timing capacitor is always connected from pin 1 to the power rail (as in picture on top of page 4 of datasheet)
-but do you think the frequency depends on the power rail voltage as well?