Thyristor firing circuit synchroniser - removes all noise by cross coupled logic circuits

摘要

The circuit ensures that the firing signals are entirely free of parasitic and noise signals which would interfere with the thyristor synchronisation. The firing signals plus noise are fed to the circuit via a centre-tapped secondary transformer (TP) the tap being grounded. The thyristors (TH1, TH2) concerned take each side of the secondary to the load directly, typically a battery charging circuit (L, B). The secondary outputs also feed a similarly grounded centre-tap secondary transformer (TR). This supplies trigger pulses to two grounded emitter transistors (T1, T2) via a diode (D1, D2) and resistive potentiometer (R1-R4) in each secondary leg. The collector outputs feed a cross-connected pair of logic gates (Q1, Q2) whose outputs provide the thyristor trigger signals either.