To Lewish:
I'm looking for a pulse synchronised with the zero voltage crossing: this pulse should be delayed not more than 50us after zero crossing! The main problem here is to avoid all the interferences which occur in a standard grid!
I'm looking for a schematic for a zero voltage crossing detector.
Application: thyristor triggering
Input voltage: 50-700Vrms
Frequency: 45-65Hz
Accuracy: better than 50us over the full voltage and frequency range.