Electronic Circuits and Projects Forum

Hi, I'm pretty new here... College student that works part time as a technician.

I primarily troubleshoot and fix power supplies for telecom switches. I get the idea of PWM and some of the over-V and over-I circuits. But I'm not very farmiliar with the power factor correction portion of the circuit. I get that the general idea is to make the load (the rest of the power supply) look like a simple device, pretty much by aligning I and V.

What I'm not understanding is why there has to be some topology on top of this. In the case of the SMPS that I work on, a boost topology is present.

Also if anyone is farmiliar with the 3854 IC, could they kind of give me a block by block run down? I have a few of the app/desg notes and it seems that the pin functions aren't so clear. Like why do you need a squaring ckt or what is why do you need the AB/C?

Thanks for all help provided, I appriciate it.

Cheers!
Dave