We have a multi-voltage design using a TOP258. Rated for 30 VA but usually lightly loaded to less than 10 VA. I did not do this design so I could use some help.
One 5 volt secondary voltage is regulated with feedback to the TOP258 via optocoupler and tl431. There are 4 other windings or stacked windings that generate secondary voltages.
It is well behaved at most temperatures between 0 and 50C, But we have been doing some low temperature startup tests (-40C) and it has a tendency to swing the regulated secondary widely. So much so that it is damaging some ICs that are rated for maximum of 6 volts.
Anyone have ideas on how to tame this secondary during low temp startup? I was thinking of a 6 volt zener clamp to ground.