PSU filters

[kyrochan]

Hallo,
I've some questions for You....

...I've seen many electronic consumer product.... tv, vcr, dvd-player and so... use before the psu unit over the classic 0.1 cap between the cold and hot wire an inductor a couple of matched inductors (tipically 47mH) like the one in the jpg I've attached. (...Common mode noise rejection????)
Should be connected as in my draw?
Should this works?
Anyone knows why in no one Zen or Aleph project appears a classic RC filter after the caps to remove the cap's inductance?
What did you think about miniaturized inductance instead the large air -cored?
Not common mode, I'm referring at the one should be use on the supply rail that goes to IC (op-amps, DAC, ADC, ecc...) instead classic resistor...

Many thanks,
Domenico

[Eva]

Your dual inductor is a common mode filter, they are usually found on SMPS. The two coils are wound separate in order to increase leakage inductance and provide also some differential mode filtering. This provides enough EMI attenuation for most low power SMPS to comply with conducted EMI directives. Radiated EMI is also dramatically reduced since it comes mostly from the input and output wires