One thing that is confusing between linear and flyback supplies is that the transformer ratio does not really determine the output voltage of flyback converter. It's the feedback/control mechanism that ultimately sets the output voltage. Theoretically, a 1:1 transformer ratio could produce kilovolts from a 5V source, but you would never be able to build that with real components.
Isat (saturation current) is probably the most important transformer parameter; stay well below it otherwise you will have poor efficiency and excessive heating. Make sure your driver transistor can handle the kickback that happens when it shuts off; higher turns-ratios will reduce this and higher leakage inductance will increase it. Be sure to run a lot of spice simulations to get a feel for the design. And dont be too disappointed when your bench-test results, especially near full-load, are not as good as your simulations. Coilcraft has a variety of transformers with turns-ratios up to 1:100, but you wont need anything that high. 1:10 is a good starting point. My nixie watch boosts 3.7V to about 150V for the display, using a coilcraft LPR6235. I exceeded Isat and it will overheat if left running for more than 20 seconds. I painted myself into a corner due to size constraints, but it basically works OK for a wristwatch. Still running after 2 years on it's *original* battery charge and keeping accurate time. -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send an email to [email protected]. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/f1734ae2-5048-4627-8405-bb9c586951e7%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
