I ran this website in Portuguese through Google translate. It looks like good info on Flybacks. I haven’t checked it out enough to say whether or not the site’s information is reliable.
I saw one schematic where the turns ratio between the collector winding and the base winding is 2 to 1. The supply voltage was shown as 6 to 24 VDC. I would never run this at more than 12VDC, because the voltage on the base could exceed the 5 or 6 volts maximum. If it has to be a voltage higher than 12V, then the ratio of the windings should be greater, 3 to 1 or 4 to 1.