Anablog

Power Electronics Technology has a nice article by Vinaya Skanda Nagaraj from Microchip about using one of their chips to do power factor correction (PFC). The article is an extension on a year-old application note the author did for Microchip. Here is an STMicro pdf about analog vs. digital control for PFC that was in EETimes India. Also a Pulse piece I did for EDN about Microchip’s PFC reference design.  What none of the digital control mavens what to come out and say is that PFC has a fundamental control response tailored for 60 or 50 cycles per second, so that is slow enough so digital control seems to work OK. I haven’t seen anything that proves it is better than analog control. Here is a Fairchild two-phase PFC article that is 96% efficient. I think it is analog control, but the point is it does not matter, analog vs. digital loops are the IC designers’ problem, not yours. I would look to an interleaved controller for high-power PFC, maybe up to the 1500 W limit of a duplex outlet. I have also referred to a three-phase PFC circuit, or perhaps I should say PFC for three-phase power, as opposed to a multiphase controller, something you don’t see written up very often.