->  ->> Does a switchmode supply not need an AC source (as in is it somehow 
->  ->> locked to the frequency of the mains)?

->  TW>  Yes it does need the 60 Hertz line frequency to operate. One 
->  TW> designed for operation from DC, be it 12/120/220 would need it's own 
->  TW> internal Frequency reference.

-> Are you really sure? Computers often come with a 120/230VAC switch on the back
-> of the PSU - no mention of 50 or 60 Hz though.

 While I said 60 Hertz most power supplies can handle 50/60 Hertz. 
In any case since it uses the line frequency reference or the
Multivibrator circuit.
 Now there are free running multivibrator designs, but the Computer
power supply dosne't use them as I recall.

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