The new converters (intellipower, connecticut electric etc)
recitfy the 120vac to dc right off the bat.
then they drive 2 channel inverters but at about 4Khz, and in the meantime, they have 50/60 and 100/120 hz chokes everywhere.
then use a transformer to step the modified wave ac down to a lower voltage (HZ(1) = HZ(2)) then rectify that and regulate it etc etc.
this eliminates the 50/60hz hummmmmmmmm the older stacked plate designs had and since a rectifier has a little bit of ripple, the effect of the ripple is the product of the voltage wave and current wave, and at 60hz is quite large, at 4000hz, its much smaller, making it pretty clean DC without any output caps
the downside is a lot of internal parts many shops cannot replace, relying on inverters for 20 some years, and killer dc voltages if a noob ever pokes around inside (id rather be whacked with 240vac than 60vdc....)
now if we can just get manus to give EVERY electronic device an optional 12vdc input port, rather than paying the $100 premium to get them from truckstops...