[Note that multiple subject tags don't do what you think, and none of the above are legal syntax anyway.] Thomas Lehmann wrote: > is there anybody who has already implemented a digital power factor > controller and can enlighten me on this topic? (Maths and more). > > For a redesign I want to replace the analog pfc- chip. I was looking into this recently myself, although I have to tell you up front that I haven't actually implemented one yet. The key concept is to create a switched-mode current regulator on the primary side such that the short-term average current (over one switching cycle) is proportional to the line voltage over that same period of time. Digital or analog domain, you need a multiplier circuit to accomplish this. One input to the multiplier is the line voltage measurement and the output sets the peak current for the current regulator. The other input to the multiplier is a proportionality factor that is derived from the rest of the power supply, indicating the amount of power currently required by the load, averaged over several AC cycles. Usually, this is just voltage feedback from the output of the main rectifier/filter, reducing the primary current when the voltage rises too high and increasing the current when it falls. In fact, this provides a certain amount of pre-regulation ahead of the main DC regulator(s). Generally, the switched-mode current regulator is used in conjuction with a full-wave bridge diode setup, so that it only needs to work with one polarity of current. This works out well with most switched-mode power supplies, as they normally rectify the line voltage to +350VDC anyway before feeding it to a high-frequency transformer. If you're using a conventional transformer or other AC load, connect the current regulator between the + and - terminals of the diode bridge, and put the AC terminals in series with your load. You'll generally want to optically couple the feedback signal into the circuit. -- Dave Tweed -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads