Electronics need DC power supplies to operate properly.
Originally Posted by SOUL-DRIFTER
Depending on the applications, many voltages may be used.
Switched mode power supplies are most often used for efficiency of power regulation.
These are variable frequency ac oscillators to keep the dc voltage constant at various loads.
Efficient because the power used varies with demand.
A 500 watt computer supply may be only using 150 watts at any given moment, but uses up to 500 as demand goes up.
Higher frequencies is more power at the same voltage.
So your computer power supply is a good typical example.
It converts the house current to DC and powers an ac oscillator with feedback frequency control.
That AC is then converted to 12, 5, 3.3, -3, -5 DC voltages for the PC to use.
That seems kind of crazy, Convert AC to DC to AC to DC outputs.
But AC to DC and DC to AC conversian is very efficient in terms of power use.
No moving parts means high efficiency power conversion.
And higher frequencies mean lighter cheaper components.
So for modern electronics, the AC or DC use becomes a blurry line.
Whatever works, use it.
A good idea stands on its own value independent of authorship.
If it stands or falls on the credibility of the author, maybe it isn't such a good idea.