Efficency of a DC power supply

[mrbedard]

I am currently designing a system that converts DC power (200 W) into AC power (100 W and 250VAR [269VA total]). The systems relies on a DC to AC inverter which I know works as I have had 2 years of experience wit it.
My question is about the AC to DC power supplies. The supplies I have looked at say they are greater than 90% efficient and use a power-factor of 0.999
If this is truly the case then my system will work which is wonderful, but it seems too good to be true.
If I supply 150 watts of AC power (and the approximate .3 VARs) will it indeed output all 135 watts of DC power or is there more power required to power the circuits required to transform the useable power from AC to DC?

Thank you,
-Matthew

 

[jraef]

I'd be suspicious of the use of the "0.999" power factor. There is a difference between displacement power factor and distortion power factor. Most likely they are only referring to one or the other, whichever sounds the best on the marketing pieces.

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[sibeen]

The newer versions of Rectifiers for telco systems - 48 volts, do have efficiencies well above 90%, approaching 95%, and input power factor >0.99. This is for a 2 kW module. With something that is an order of magnitude smaller I'd expect that the efficiency would drop of a bit but the power factor be a similar value.

 

[itsmoked]

As they turn to active power factor correction front ends they can start using the active devices to do the rectification with a huge efficiency improvement.

They tend to do that with telcom because it also works with live insertion and parallel redundant front ends because they also are based on active "synchronous rectification".

mrbedard; 90% + efficient supplies are becoming common. I wouldn't doubt that claim at all. The 0.999pf? That seems a little high. I would believe 95%. If they stand by it - it could be.

Keith Cress
kcress -

http://www.flaminsystems.com