The small off-line switch-mode power supplies are designed without any user replaceable parts. This normally includes the input fuse. This is a sensible practice since the fuse will interrupt only when a serious failure occurs elsewhere, such as a shorted bridge rectifier, or shorted FET, etc. When the fuse interrupts it is virtually assured that the supply is not repairable.
For less serious events, such as an overloaded output channel, electronic current limiting protects the supply from damage and the input fuse will not interrupt. There is no reason at all to add a fuse in series with the fuse! Selecting the proper fuse considering inrush at startup, mains current at low-line, hi-break characteristic for Nordics, etc. etc. suggests you will end up exactly the same fuse as used by the power supply manufacturer. Bob Den Bleyker, [email protected]
