Fuse blowing up

[MuLdEr]

Hello,

I had a problem, look at the schematic, I built power supply like this, and the problem was the fuse blew up always when I turned switch on. I sorted out this one with placing fuse before switch, but still I don't know what was the reason of fuse blowing up, maybe you know??

 

[Nigel Goodwin]

Hello,

I had a problem, look at the schematic, I built power supply like this, and the problem was the fuse blew up always when I turned switch on. I sorted out this one with placing fuse before switch, but still I don't know why was the reason of fuse blowing up, maybe you know??

You should make sure you use an anti-surge fuse, particularly if using a toroidal transformer - toroids have a much greater switch-on surge than conventional transformers. As the toroids get larger, you need to implement soft-start circuits.

Placing it before, or after, the switch shouldn't make any difference, electrically it's identical.

 

[JimB]

Inrush current at switch on, definitely. Especially with all that capacitance after the rectifier.

You must use a slow-blow or an anti-surge fuse.

JimB