> > Power factor for pulsed loads, such as an LED light bulb gets messy
> > and a full blown solution is not able to fit within the confines of
> > the bulb itself. And, reading the real and reactive power for a device
> > that doesn't have a sine wave current draw is not trivial.
> >
> > I bought 3 different LED bulbs from Home Depot and Walmart, they have
> > power factor values between .47 and .6!! Later I got some energy star
> > rated bulbs and they measured .88 to .92. I'm thinking of dissecting
> > the energy star bulbs just to find out what makes them tick.
> >
>=20
> I'd always thought of power factor being due to reactive but linear loads=
..
> Switching power supplies (or any AC to DC converter that has diodes direc=
tly
> driving capacitors) are nonlinear loads where the instantaneous AC line
> current is not proportional to the instantaneous AC line voltage.
> "Power factor correction" for nonlinear loads generally takes the form of=
 a
> boost converter between the diodes and the filter capacitor so the capaci=
tor
> is charged through the whole cycle with the instantaneous AC line current
> being proportional to the instantaneous AC line voltage.

I'm guessing the energy star bulbs tested are fitted with an IC that is ava=
ilable to do exactly this, and the others don't for cheapness.

I've lost track of how many ICs form different manufacturers are now availa=
ble for getting the low power factor, but I do remember figuring they didn'=
t cost much to add to a circuit even with the ancillary components required=
..




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