--===============1435531982== Content-Type: text/plain; charset="gb2312" Content-Transfer-Encoding: quoted-printable X-MIME-Autoconverted: from 8bit to quoted-printable by pch.mit.edu id m7QMAOA4023057 =20 I just built a power factor pre-converter for our charger product here. =20 =20 I really hope the PFC can be done without any magnetic components, the ch= eap inductor I bought drove me crazy. > Date: Tue, 26 Aug 2008 14:02:59 -0700> From: marcel@carrietech.com> To:= piclist@mit.edu> Subject: Re: [EE] New ideas for power factor corrected = supplies> > Very interesting read - thanks!> - Marcel> > On Mon, Aug 25, = 2008 at 2:53 PM, Olin Lathrop wrote:> > > Dave= Tweed and I were finally granted US patent 7,411,378 last week on our> >= power factor correction circuit. The basic concept is to use digital> > = computation to know what currents are flowing in various places so that> = > there is no need to measure them. Our circuit is controlled digitally, = and> > the controller only receives measurements of the voltages, not any= > > currents.> > There are various ways to measure current, but it's alwa= ys a bit> > inconvenient. Our scheme gets around this requirement.> >> > = The first place this concept is applied is in controlling the AC input> >= current such that it stays proportional to the input voltage. This is th= e> > power factor correction (PFC) functi on. The details are in the patent, of> > course, but since it's been nea= r lawyers it's not the easiest to follow.> > The writeup at http://www.em= bedinc.com/pfc explains this application of> > the> > concept in a more f= riendly manner.> >> > The other application that the writeup above does n= ot go into is regulating> > the output voltage of the PFC controller. Sin= ce the AC input current must> > be kept proportional to the AC input volt= age, the output voltage can't be> > tightly controlled like it would be i= n other types of switching power> > supplies. The traditional approach (w= hich is also used in the write at the> > link above) filters the output v= oltage feedback signal to try to remove the> > frequecy components due to= the necessary AC input current ripple, but> > otherwise pass as much as = possible so that changes in the load can be> > accomodated as quickly as = possible. This is of course a tradeoff with no> > ideal solution. There w= ill be some response to the ripple caused by PFC> > (thereby defeating a portion of the PFC), and the response to= load changes> > will be slowed.> >> > Our solution is to use voltage mea= surements and computing power to> > determine> > what the load is doing i= ndependent of the ripple caused by the PFC. One> > way> > to think about = it is that since we know what charge is being dumped onto> > the> > outpu= t capacitor, the ripple caused by the AC input waveform can be> > compute= d> > and thereby explicitly removed from the feedback signal. The remaini= ng> > feedback signal is due solely to load variations, and can be reacte= d to> > quickly without defeating the PFC. This allows for tighter output= voltage> > control and/or a smaller output capacitor. One explicit equat= ion for this> > is given in the patent, although others are possible.> >>= >> > *******************************************************************= *> > Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products= > > (978) 742-9014. Gold level PIC consul tants since 2000.> > --> > http://www.piclist.com PIC/SX FAQ & list arch= ive> > View/change your membership options at> > http://mailman.mit.edu/m= ailman/listinfo/piclist> >> -- > http://www.piclist.com PIC/SX FAQ & list= archive> View/change your membership options at> http://mailman.mit.edu/= mailman/listinfo/piclist _________________________________________________________________ =BF=EC=C0=B4=BF=B4=BF=B4=D5=E2=D0=A9=C3=A8=DF=E4=D3=D0=B6=E0=B6=BA=A3=AC=B1= =AC=D0=A6=A3=A1 http://cnweb.search.live.com/video/results.aspx?q=3D%E5%8F%AF%E7%88%B1%E7= %8C%AB%E5%92%AA&Form=3DMEVHAA --===============1435531982== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Disposition: inline Content-Transfer-Encoding: 7bit -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist --===============1435531982==--