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Electronics => Beginners => Topic started by: lordvader88 on May 25, 2018, 11:23:18 pm

Title: PFC sections of ATX power supplies
Post by: lordvader88 on May 25, 2018, 11:23:18 pm

What exactly are they doing again ? Something with power triangles and getting the most resistive power output at any moment ? And mains is at 60Hz and PFC controllers switch at what frequencies >>10kHz ? Is it fixed or not? 60Hz is fixed

Does the PFC voltage vary from rectified mains to 2x or is it more or less fixed ? Maybe that's voltage mode and current mode fixes a current ?

How do they differ from the following stage that usually switches a flyback transformer ? (They are just a boost converter ?)

I know complex numbers no problem, but idk many eq's for elec's of this stuff

Why are they typically rated at +2x mains Vpeak, like +350V, when the intended overall output is only 5-12V ? What is the reason use a boost converter to 2x the voltage rather than say 1st use a buck converter and use 1/2 the voltage?

Fire away thanks

Title: Re: PFC sections of ATX power supplies
Post by: wraper on May 25, 2018, 11:27:50 pm

PFC is a boost converter with rectified AC on it's input. On the output it's a constant DC, usually around 400V.

Title: Re: PFC sections of ATX power supplies
Post by: lordvader88 on May 25, 2018, 11:31:55 pm

I must learn again

https://www.youtube.com/watch?v=4kdVYxq60jU (https://www.youtube.com/watch?v=4kdVYxq60jU)

I do have the internet btw, it's just I'm asking as if in a room of people, because that might be easier than cracking the books, because I'm playing SC2 on brutal

Title: Re: PFC sections of ATX power supplies
Post by: wraper on May 25, 2018, 11:32:18 pm

Quote

What is the reason use a boost converter to 2x the voltage rather than say 1st use a buck converter and use 1/2 the voltage?

And how you will step down down, say, 30V during mains voltage cycle into 100V?