TEA2029 データシートの表示（PDF） - STMicroelectronics
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TEA2029 Datasheet PDF : 47 Pages
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TEA2028 - TEA2029 APPLICATION NOTE
V.5 - Second Phase Locked Loop ”φ2”
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 ”φ1”.
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
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
VIDEO SIGNAL
ON CATHODES
Blanking Time
Center of
Screen
LINE YOKE
0
CURRENT
LINE
FLYBACK
LINE TRANSISTOR
CONTROL OUTPUT
Line Transistor
Collector Current
t LF
0
12µs
Saturation
Turn-off
Turn-off Delay
64µs
Figure 36 : Second Phase Locked Loop ”ϕ2” Block Diagram
Video
(Pin 27)
ϕ2
Signal
Constant
Delay
by ϕ1
t IN
Line
Flyback
ϕ2 Phase Comparator
∆t
A
i
mA/µs
t OUT
16
f(p)
Low-pass
Filter
Horizontal Phase
Adjustment
Phase
Modulator t’OUT
V
1
Monostable
(29µs)
Output
Stage
(x 1)
t’OUT
29µs
10
Inhibition
LF Pulse
Shaping
x1
12
LF
t OUT
Line
Yoke
EHT
Transformer
Line
Deflection
Stage
19/46
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