Wouldn't it be more efficient to have e.g. one DC power supply for the house that can power everything that needs DC power, instead of lots of individual (and likely cheap/inefficient) power supplies?
Most electronic devices require low voltage DC, so resistance losses in cabling across even quite short distances (10+ metres) would be significant. This is why DC distribution in data centres if it is used is normally 48V.
It’s also more difficult do do straight transformation on DC voltages, it can be done but the reason our power grid settled on AC was getting high voltage transmission levels down to reasonable ones for use is simple with some wound coils.
It’s really easiest to just keep everything AC until the point of use, putting a transformer and a bridge rectifier in most devices is a better solution than needing switching power supplies everywhere to convert DC voltages (or wise options like linear regulators).
Switched mode power supplies also have EMI to deal with due to the higher switching frequencies, an AC transformer runs at line frequency (50/60Hz).
Dumb DC supplies using just a bridge rectifier and filter cap(s) isn't really ideal if you need a stable voltage. If the mains voltage sags, so does output. Then factor in ripple from the cap bank under higher loads and the associated nonlinear harmonics and power factor issues from the rectification. You could add a linear regulator and increase the transformer output and burn the excess off as heat but efficiency goes down the toilet.
Switchers, for all their complexity, are pretty damn clean in terms of output and input PF correction. Even in audio and sensitive analog applications where dumb supplies were preferred have been replaced by switchers. A good design goes a long way and it's unfortunately easy to design junk switchers because of the complexity involved.
EDIT: Most consumer appliances will still need there own power supplies. You would still want a last step DC transform to house at a high voltage. If the appliance operates at the voltage DC then it would need no power supply.
Yes, and cheaper to build!
You can achieve the same efficiency with DC and AC do not directly effect efficiency across the line contrary to popular belief. It is simple about what the voltage across the line is.
AC was in because it allowed us to build transformers to up and down voltages to provide efficient across the line.
Nowadays, we can build DC transformers with Power MOSFETs which are cheaper, and more efficient then there AC counter parts (old [magnets and inductors] and new [You can do AC transformers with MOSFETS with some extra steps/components]).
Additionally, since most consumer appliances first step is to rectify the voltages most build in the past two decades are DC compatible. Additionally, newer ones could then drop the rectifier stage and become cheaper and more efficient.
>Yes, and cheaper to build!
You can achieve the same efficiency with DC and AC do not directly effect efficiency across the line contrary to popular belief.
In fact there are higher loses with AC power transport (specially in long distances) due to the parasitic capacitance of the lines, that’s why some countries use DC power transport lines now.
Line losses, see my reply below. Once you go beyond needing 10-15 watts and cable lengths beyond a few meters you start losing a lot of power through the wire.