[Amps] Direct rectification of AC mains to drive the amp,

[Manfred Mornhinweg]

Bill,

> Power factor correction is an area I am a bit hazy on. Could someone explain
> why the power factor would be different between a direct-rectified PS and a
> transformer-isolated one?

I have mentioned it before, but I can explain it again: Yes, both charge 
the capacitor with pulses, so the difference between the two is not very 
large. But when there is a transformer, this transformer places both 
resistance and inductance in series with the circuit, moderating the 
intensity of the pulses, stretching them out, and even getting them a 
little closer to the correct phase.

Note that the transformer does this through its imperfections: Winding 
resistance, and leakage inductance. The better a transformer is, the 
worse the power factor gets! A power supply using a perfect transformer 
would have the same power factor as a direct, transformerless one. In 
reverse, a transformerless power supply's power factor can be improved 
by deliberatingly adding series inductance and resistance.

Manfred

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