No, the current into a so-called linear power supply is anything but sinusoidal.
It consists of sharp current peaks whenever the voltage waveform exceeds the
voltage on the resevoir capacitor by more than the rectifier diode drops. The
more you try to increase the efficiency by reducing the transformer winding
resistance, decreasing the rectifier diode drops, increasing the size of the
resevoir capacitor and decreasing its effective series resistance, the shorter
and sharper the current peaks. It is precisely this type of current waveform
that
lands the equipment in Class D of EN61000-3-2.
A point in that standard that some may not have noticed is a that there is a
complete ban on the use of half wave rectification.
Nick Rouse
