Vertical deflection circuit for TV receiver - uses switching power supply circuit to provide current for deflection coil

摘要

A generator (9) produces a sawtooth waveform at the field frequency and is applied through an amplifier (14) to an input (12) of a comparator (13). The other input (15) is obtained from a capacitor (16) charged from a constant current source (17). The capacitor is discharged by an electronic switch (18) during the line flyback period. The comparator output is applied to an amplifier (20) to trigger a thyristor (10) to switch the secondary (2) of a line transformer (1). The conduction time for the thyristor is a function of the sawtooth generator signal level and thus the line number. The secondary winding provides pulses during the line flyback period which are filtered by an inductor (5) and a capacitor (4) whose charge drives the vertical deflection coil (5). A series capacitor (6) maintains a constant sign of the voltage across the coil.