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# how to measure PowerFactor of LED Driver

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#### gilbertomaldito

##### Full Member level 3
Can someone help me how to measure the Power Factor of the LED Driver? please guide me.

u get one of them meters you buy from shop and do it....maybe \$20,

or

you have to calculate what is the fundamental sine amplitude in your supply, and its phase, and get it like that

do u have a specific pfc front end or just a fwb?

...if just a fwb then good luck, the calculations are not terribly easy......you will need your ac mains voltage waveform, and your mains input current waveform. -together , so you can see the phase too.

are you ready for the serious mathematical jamboree that you are now about to embark on?

take a look at your current waveform.......it is not sinusoidal is it.

..but you now have to cALCULATE WHAT IS THE "FUNDAMENATAL" SINE OF THAT WAVEFORM......(SORRY ABOUT CAps)

When you have that sine, and have both its amplitude and phase relative to the voltage...then you do Vrms * Irms * cos (phi)
where phi is the phase from volt to current.

that is your "ACTIVE POWER" input to the led driver.

You now have to find the APPARENT POWER input.

That is equal to Vrms*Irms and doea not take account of the phase.

then real power/apparent power is your power factor.

if you want, you can just estimate your active power by knowing what power is consumed by the LEDs, and then divide this by 0.8....assuming 80% efficiency.

My design is still in Hspice. Its not physically finished yet. Sorry for not stating it earlier. from AC - Traic DImmer - LED Driver IC - LEDs how can I calculate the pf.

First understand the definition of power factor! There's a good explanation e.g. at wikipedia. Then acquire the respective quantities from a transient analysis and you're done. The basic point is to measure real power and total apparent power.

You can use the SPICE fourier analysis capability for an easy evaluation of power factor.

andrew_matiga said:
My design is still in Hspice. Its not physically finished yet. Sorry for not stating it earlier. from AC - Traic DImmer - LED Driver IC - LEDs how can I calculate the pf. I was told by my boss to measure the pf and the efficiency. But I still dont know how.
do you still want to know

How to measure the harmonics of my LED driver?
Do you know the syntax?

Do you know, that there are manuals for HSPICE? I have them for reference, although I don't use the tool.

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