You actually need 2 windings, i.e. a transformer so you can keep the duty cycle reasonable. George ----- Original Message ----- From: "Alan B. Pearce" To: Sent: Tuesday, September 23, 2003 6:17 PM Subject: Re: [PIC:] Stealing power from the phone line update > >I chose a switching frequency of 100 kHz for a good balance between being > >easy to filter out of the audio and good efficiency. I came up with a coil > >value of 100mH, which is rather large. In fact, I couldn't find any 100mH > >coils that didn't have a self-resonant frequency that was less than 100kHz! > > > >Any ideas, or is this a lost cause? Is it possible to build a resonant > >converter that can work with nonideal coils with good efficiency? It sounds > >like things could get very complicated very quickly. > > I suspect at these very low currents you need a very high switching > frequency. The limiting factor will become the dI/dt function that the > inductor controls, which is why you need such a large inductor. > > -- > http://www.piclist.com hint: To leave the PICList > mailto:piclist-unsubscribe-request@mitvma.mit.edu > -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu