TEA2029 STMICROELECTRONICS [STMicroelectronics], TEA2029 Datasheet - Page 19

• Manufacturer Part Number: TEA2029
• Description: APPLICATION NOTE
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

V.5 - Second Phase Locked Loop ” 2”
This stage controls the horizontal deflection of the
electron beam i.e., the horizontal picture scanning.
The frequency of operation, in the absence of video
signal, is a multiple of the VCO frequency, i.e.
15625Hz - 500Hz.
When video signal is present, the scanning fre-
quency is synchronized with the video signal
through the first phase locked-loop ” ”.
The output rectangular waveform signal drives the
line switching transistor. This transistor, when
turned-off, generates what is commonly called the
”line flyback”.
In order to obtain a horizontally centered picture,
the line flyback (LF) must coincidewith the blanking
time on tube cathodes.
The turn-off delay is due to transistor base storage
time. This time varies in different TV sets as the
transistors employed may have different operating
characteristics which are functions of temperature
variations, power rating and base drive.
Therefore, it follows that in order to obtain stable
Figure 36 : Second Phase Locked Loop ” 2” Block Diagram
(Pin 27)
Signal
Line
Flyback
Video
2
t
IN
Constant
Delay
by 1
2 Phase Comparator
t
OUT
t
mA/ s
A
i
LF Pulse
Shaping
x 1
16
f(p)
Low-pass
Filter
V
image centering, the line flyback must be phase-
locked with respect to the video signal.
The second phase-locked loop also offers the pos-
sibility of horizontal phase-shift adjustment.
Figure 35
TEA2028 - TEA2029 APPLICATION NOTE
VIDEO SIGNAL
ON CATHODES
LINE YOKE
CURRENT
LINE
FLYBACK
LINE TRANSISTOR
CONTROL OUTPUT
Modulator
Horizontal Phase
Phase
Adjustment
12
LF
t’
OUT
t
OUT
0
Monostable
Blanking Time
(29 s)
0
Turn-off
1
t
LF
Yoke
Line
Collector Current
Turn-off Delay
Line Transistor
Center of
Saturation
Screen
12 s
Inhibition
Output
Stage
(x 1)
EHT
Transformer
Line
Deflection
Stage
10
t’
OUT
29 s
64 s
19/46