It's an unfortunate characteristic of MOSFETs that the Rds(on) increases with temperature. As they get hotter, they dissipate more power and get hotter still. I've had MOSFETs get so hot they actually unsoldered themselves, though remarkably, they still worked once they cooled down. But it's always a good practice to run them as cool as possible.
If you have a HV converter running hot, it's nearly always a consequence of the driver not turning it off quickly enough. That results in the FET absorbing a lot of power from the inductor, which goes off in heat instead of high voltage. You need a driver that can bring the gate down hard and fast with power to spare, and then things will run a lot more efficiently. The turn on time is far less important, as the inductor limits the current rise time anyway. The popular MC34063 is a particularly bad choice for a HV supply, because it has a powerful high side driver to turn the FET on quickly,but no active pull-down to turn it off. > -- 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/67d2f1db-f22f-4903-b88d-c439a1fe7464%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
