Filterfuse blow up
Posted by: theswissguy
on
Hi. We use a pretty standard, 2 output, isolated 3W design with LNK363. Our circuit looks very similar to the one in "EPR-9" application note. As an input "filterfuse" (RF1), we use a wire-wound type of 8.2R (3W). We have noticed several times that the resistor will blow up. We do not quite know why. The voltage across the resistor is of course very small (2V-pp with 230VAC input). While the resistor make is of Asian "no-name", it is a wire-wound type and the resistance is also right.
Anyone has an idea as to this resistor, which is hugely over-dimensioned with 3W, would still blow?
Hello theswissguy,
Without any details, I have to assume the fuse resistor is the single part damaged and the unit is up and running again as soon as you replace the input fuse. Also, let’s consider you have a good quality fuse resistor. For this case I will suggest you to check the rectifying diodes, I suspect the amplitude of your input voltage is higher than the rating of your diodes.
Cheers,
PI_Crusher