cybose said:
What is the relationship between the two ? Can one be used in place of
the other in all situations ?
A switch mode power supply (SMPS) is a regulated supply. I assume
that by "regulated", you mean linear dissipative regulation. An SMPS
regulates by producing varying magnitude or duration pulses and then
averaging those pulses with a passive filter to produce the regulates
output or outputs. Since the pulses are at fairly frequency,
isolation through a transformer can be done at this stage with
transformers that are a lot smaller than 60 Hz ones.
This process can be quite a bit more efficient than simply burning up
the excess voltage in a linear regulator, but it also is a noisy
process. However, this is not all bad. By the time the filters
convert the power pulses to DC, they are also capable of filtering out
lots of line side noise. So while the regulation process in a SMPS is
not as inherently fast at correcting output errors, the filters can
often beat the high frequency attenuation of linear regulation control
loops.
