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Power Integrations Engineer Power Integrations ModeratorHelp on LNK306 ...
HI, I need some help
I design a power supply with LNK306 and at its input I use normal 2 watt resistor (instead of fusible one) sometimes its blow up.... I change the resistor with higher one (86 ohm and 150 ohm) but it sometime still blow up.... now i have some questions
1) Can I remove the input resistor completely (as the data sheet says it is optional)?
2) Can I use normal 10 ohm, 2 W resistors with some normal glass type fuse serial with it ?
3) I saw in the forum some same problem which the designer solve it by putting some MOV at the input of power supply. Will it work for me too?
narbeh_rob
You need something to protect your circuit from catastrophic events. So you nee a fusible resistor (FR) or a fuse. What do you prefer? If you use a fusible resistor, you have to use a flame proof resistor. This type will get open in the event of a catastrophe and would not produce any fire. Or do you may want to use a fuse.
If you use a FR , the larger the value, the lower your power supply efficiency. If you need to pass surge test, the FR impedance will help in passing surge testing better that the fuse.
The MOV is used to protect the power supply when a surge voltage is applied to its input. The MOV will act as a high voltage zener and will clamp the high voltage spike protecting the power supply form the surge.
In resume:
You need to decide if you want to use a fuse or a FR. Ifd you decide for a FR, it has to be flame proof type.
If you need to pass surge spec, you need to add an MOV to your input circuit.
Thank you. PI-Worf
PI-Worf | 313 posts 