GB1370074A - Television line oscillators - Google Patents

Abstract

1370074 Television synchronization circuits PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 13 March 1972 [16 March 1971] 11613/72 Heading H3A A television synchronization circuit for correcting timing errors in a line scan system comprises a first synchronizing stage A for the phase comparison of the incoming line synchronizing pulses 1 with a first reference signal 7 of line frequency and for deriving an output signal 2 at line frequency, a second synchronizing stage B for the phase comparison of the output signal 2 with a second reference signal 9 derived from the line fly-back pulses and for deriving a second output signal at line frequency for controlling a line output stage 3, 4. The first and second reference signals may be a sawtooth, a limited sawtooth wave respectively derived from the line fly-back pulses 5 by an integrator 6 and a limiter 8. Alternatively the first reference pulse may be constituted by the output 2 of stage A fed back for retroactive control (Fig. 3, not shown). The phase discriminators # A , # B operate in such a manner that at synchronization, the pulses 1, 2 coincide substantially with the middle of the flyback, scan waveforms respectively of the reference sawtooth signal. The integrator, limiter 6, 8 may comprise oppositely poled diodes or a saturable core transformer (Figs. 7a, 7b, not shown). In order to compensate for amplitude, pulse duration variations of the fly-back pulses 5 caused by a variable EHT load at the output of stage 4, the pulses 5 may be applied to a symmetrical limiter (16-20, Fig. 10, not shown) which produces a constant amplitude, constant width pulse about a predetermined voltage level which may be applied to a Miller integrator for deriving a sawtooth wave for application as reference signals to the phase discriminators # A , # B . Reference is also made to Specification 1,369,517.