I have circuit where the input can be 12-48V AC or DC. This is fed to a bridge rectifier. 
I plan to put a fuse and got a bit confused, what is the best place to put a fuse?
- before the bridge
- after the bridge on +ive line?
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3\$\begingroup\$ No wonder you are confused :) \$\endgroup\$– RevJan 5, 2016 at 9:43
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2 Answers
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The usual approach is on the AC line (inserted into your N$93 net) before the bridge, which will protect the power supply if the bridge rectifier fails short.
Assuming there is bulk capacitance after this bridge rectifier, you will need to use a slow-blow fuse so that the inrush current doesn't destroy it. If the capacitance is very large, you will want to consider an inrush-limiting circuit that initially charges the big C through a high-power R for a few cycles and then closes a relay across the R for normal operation.
PS your bridge rectifier is probably wired backwards, the +12V_PWR net will be negative with respect to the DF0-something net on the lower-right.
answered Jan 5, 2016 at 9:17
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The basic purpose of fuse is protect the circuit elements from the over current.
If you add the fuse before the bridge rectifier mean it will protect the bridge rectifier and your circuit also.
Else if you add after Bridge rectifier it will protect only the circuit which is going to connect.
