Electronics > Beginners
PSU supporting both 120v and 240v.
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soldar:
The EU mandates limits on harmonics and does not care about how you achieve that.

https://en.wikipedia.org/wiki/IEC_61000-3-2

A passive low pass filter can meet the requirements and is cheaper than active PFC.
dmills:

--- Quote from: soldar on June 11, 2019, 02:55:56 pm ---The EU mandates limits on harmonics and does not care about how you achieve that.
https://en.wikipedia.org/wiki/IEC_61000-3-2
A passive low pass filter can meet the requirements and is cheaper than active PFC.

--- End quote ---

I very much doubt that it is cheaper, third harmonic is only 150Hz, so that is a LARGE inductor to keep that out, while an active PFC is like one mosfet, a gapped inductor and a small controller chip, a boost stage running at maybe 50KHz is going to be cheaper then a LC filter cutting off below 150Hz, probably just on the shipping cost never mind anything else!

Certainly by the time you are looking at any kind of modern server power supply, I would be VERY surprised to see passive harmonic filtering, rather then active PFC.

Regards, Dan.
soldar:

--- Quote from: dmills on June 11, 2019, 03:20:50 pm --- I very much doubt that it is cheaper, third harmonic is only 150Hz, so that is a LARGE inductor to keep that out, while an active PFC is like one mosfet, a gapped inductor and a small controller chip, a boost stage running at maybe 50KHz is going to be cheaper then a LC filter cutting off below 150Hz, probably just on the shipping cost never mind anything else!
--- End quote ---

I have no opinion on what is cheaper but most cheap PC PSUs do not have active PFC and I assume they meet applicable regulations.

My TV, computer monitors and laptop PSUs do not have active PFC either.

Now that I think about it I can't think of any appliance or light in my home that has active PFC.

Residential customers do not pay for reactive power so they have no incentive to improve the power factor.

OTOH big businesses do pay for reactive power and have an incentive to improve PF. I remember reading about some company that had LED lighting with active PFC because they had thousands of such lights and PF was an important consideration.
mariush:
I think there was an exception in EU rules for psus with less than 75w output, so your monitors may lack active pfc.
TV may use less than 75w, depends on backlight.
if your laptop's brick is over 65w, it should have active pfc.
soldar:

--- Quote from: mariush on June 11, 2019, 03:52:43 pm ---I think there was an exception in EU rules for psus with less than 75w output, so your monitors may lack active pfc.
TV may use less than 75w, depends on backlight.
if your laptop's brick is over 65w, it should have active pfc.

--- End quote ---
You think there is an exception? Why do you think that? And what exception?

Because, you know, I just linked to the relevant regulation.
https://en.wikipedia.org/wiki/IEC_61000-3-2
Did you read it?
That regulation establishes allowable harmonics current and says absolutely nothing about active PFC. And I cannot imagine why they would care how you achieve the objective.

If you have better information I'm sure we'd all like to see it but "I think" doesn't cut it.

All my devices are over 80 W and none have active PFC.
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