----- Original Message ----- From: Peter L. Peres To: Sent: Friday, May 04, 2001 07:52 Subject: [PIC]: PLL with a PIC (50/60Hz lock) > You are right, zero cross detection will pick up all the noise on the > line, but better detection relies on averaging detection (with > deliberately poor filtering) followed by differentiation. This detects the > peaks and should give you less troubles than a PLL. Hmmm, sounds interesting. Do you have any pointers to something like an application or design note discussing such a circuit? > semiperiods for input) (note that 1% is a relatively large error for mains > phase. It represents the normal conduction angle of a peak rectifier and > almost 2 degrees of phase). Depending on how much power you feed back this > may be enough (remember that the phase error associated energy almost > entirely turns into heat in your switching elements due to > 'misunderstandings' between them and the mains). I was thinking about pulse width modulating a sinewave with a certain level of cross over delay. This means that I do not create half sinewaves of 10ms (@50Hz) long, but for example 8 or 9ms. However, this smaller 'timebase' of the half sinewave shape, is still switching in polarity every 10ms in the power circuit. I know the sinewave which is fed back into the mains is slightly distorted, but it should still not violate any harmonic content regulations I think. Using this method gives me some headroom for mains frequency changes and/or small phase errors. > Will you publish your circuit ? You mean on the PIClist? If I can find any info of the circuit you described above, I will do that if people are interested. However, keep in mind that this is a hobby project so it might take some time before I have something that works :) Daniel... http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details. -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.