TEA2029 STMICROELECTRONICS [STMicroelectronics], TEA2029 Datasheet - Page 24

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

TEA2028 - TEA2029 APPLICATION NOTE
In practice, the power switch ”K” is built by a
combination of ”High Voltage Switching Transistor”
and ”Fast Recovery Diode”.
Figure 47
Figure 48 : Simplified Diagram of the Horizontal Deflection Stage
24/46
V
V
V
i
i
i
TEA2028B
L
K
C
C
P
L
E
E
0
0
0
0
0
t1
End of
Trace
10
12
t2
t
+12V
LF
Li ne Flyba ck
t3
Capacitor
Coup ling
R
Begining of
L
Input
Trace
if K remains
open
t4
(regulated by SMPS)
E
T
DRIVER
TRANSFORMER
Tr
EHT
I
D
If considered in average value, it is seen that the
voltage across capacitor”CS” is almost equalto the
source voltage ”E”. The saw-tooth current through
this capacitor will produce a parabolicripple around
”E”, which will thus modify the equivalent source of
the line yoke and induce a modified current of ”S”
shape within the yoke. This ”S” current is used to
produce a linear picture as a function of the picture
tube geometry.
The basic arrangement can be reconstructed by
assuming that the equivalent inductor ”L” is the
transformer ”L
parallel (since VC
The output Pin 10 of TEA2028 is applied to a
matching stage called ”line driver” the output of
which drives the power transistor ”T
ing stage is necessary for optimized base drive.
At middle of trace, the transistor enters into satura-
tion and its current rises linearly. V
a control signal to turn the transistor off. The tran-
sistor will be in fact turned-off after a delay interval
”t
on application. The system will then enter into
oscillation during its half-period thereby generating
the line flyback. At the end of flyback time, the line
yoke current is negative while the voltage across
capacitor”C” has fallen to zero. The energy transfer
automatically takes place by the recovery diode
during the first portion of trace time.
Also, it is clear that the line scanning phase with
respect to video signal is determined by the rising-
edge of Pin 10 output signal.
Tr
I
D
S
” (storage time) varying from 2 to 8 s depending
L
P
I
C
C
Line Yoke
(Pin 12, TEA2028B)
P
” and line yoke inductors put in
Line Flyback
C
S(AV
5
V
[15 to 25kV]
Miscellaneous Power Supplies
I
Y
EHT (anode)
) = E).
V
C(5)
10
r
will then issue
”. The match-