Toshiba CF35E50, Technical Training Manual

Page: 59 / 139

59
1. SYNC SEPARATION CIRCUIT
The sync separation circuit separates a sync signal from a
video signal and feeds it to an H and V deflection circuits.
The separation circuit consists of an amplitude separation (H
and V sync separation circuit) and a frequency separation
circuit (V sync separation circuit) which performs the
separation by using a frequency difference between H and V.
In the N5SS chassis, all these sync separation circuits are
contained in a V/C/D IC (TA1222N).
Fig. 9-1 shows a block diagram of the sync separation circuit.
Fig. 9-1 Sync separation circuit block diagram
Fig. 9-2 Synchronous separation by auto slider system
1-1. Theory of Operation
1-1-1. Auto slicer type synchronous separation circuit
When a synchronizing signal is separated, synchronous
separation is made from the beginning with constant voltage
in the conventional synchronous separation circuit. The auto
slider type circuit employed in this time makes synchronous
separation at a constant rate against the synchronizing signal
amplitude. (See Fig. 9-2)
In this method, even if an abnormal signal with small
amplitude is applied, stable synchronizing performance can
be obtained without separating pedestal.
17
Sync
input
Composite
video
signal
Q501
H. V SYNC
SEPARATION
CIRCUIT
V SYNC
SEPARATION
CIRCUIT
WAVEFORM
SHAPEING
CIRCUIT
H sync siganl
V sync signal
(Reset pulse)
B
A
D
B
Pedestal Level
a: Corect Sync. Signal
Sync Separation Level A:B=C:D
b: Small Amplitude Sync. Signal