TEA2029 STMICROELECTRONICS [STMicroelectronics], TEA2029 Datasheet - Page 23

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

Open-collector output :
V
The line output (Pin 10) will go high if either the
following three inhibitions is activated :
A. INHIBITION AT START-UP
This is generated by a hysteresis comparator which
is driven by ”KV
voltage.
This inhibition is mandatory since the device will
operate only at V
Figure 45
B. INHIBITION DURING LINE FLYBACK
The output signal Pin 10 is high during line transis-
tor turn-off. The leading edge of output signal
Pin 10 turns off the line transistor after a delay
interval (storage time).
The line transistor turn-off generates an overvol-
tage on the collector corresponding to the line
flyback pulse. During this interval, in order to avoid
transistor destruction, the Pin 10 output must ab-
solutely remain high.
This is done internally with the line flyback pulse
(Pin 12), which forces Pin 10 output to high level
during the line flyback time.
C. SAFETY INHIBITION
The device has a security input terminal ”Pin 28”.
If a signal lower than V
pin, line and power supply outputs are all inhibited.
This function is particularly useful for TV chassis
protection. Refer to section V.7.5 for further details.
V.5.2.6 - Line deflection stage
This chapter will cover a general description of the
”horizontal deflection stage” employed almost
commonly in all recent TV sets.
Deflection of electron beam is proportional to the
intensity of magnetic field induced by the line yoke.
This yoke is equivalent to an inductor. The deflec-
tion is therefore proportional to the current through
inductor.
In order to obtain a linear deflection from left to right
as a function of time, a saw-tooth current must be
generated within the yoke. The approachis toapply
a switched DC voltage to the line yoke.
10(SAT)
< 1.5V at I
1
0
SUPPLY VOLTAGE (V)
CC
CC
10(MAX)
5.5 6
” and the ”1.26V” reference
5V.
REF
= 20mA
(1.26V) is applied to this
V
HYST
= 0.5V
- When K is closed :
-
- ”i
Figure 46
- Current at the end of trace : I
- Energy stored within inductor : W =
The circuit period is classically given by :
T = 2
If ”K” is closed at time ”t
again have a voltage ”E” across its terminals. The
current falls linearly until ”t
sponds to the first half of line trace interval.
The overvoltage across C is :
V
That is : V
In practice, E is higher than 100V.
t
Note that this overvoltage is almost 8 times higher
than the source voltage ”E”. This overvoltage is
applied to the primary winding of a ”step-up trans-
former” (EHT Transformer) in order to generate the
high voltage required by picture tube anode.
TEA2028 - TEA2029 APPLICATION NOTE
trace
P
i
The current will therefore be linear as a function
of time i
second portion of the line trace interval.
If the switch is opened at t = t
nation will enter into oscillation, the energy stored
within inductor is transfered to the capacitor,
which will return it to the inductor and so on.
r
t
di
L
L(t)
dt
trace
y
L
2
= E
L
” variations as a function of time :
is always higher than half of trace time :
= 52 s, t
=
=
=
r
E
E
L
2
y
t
trace
T
LC
e
LC
L(t)
H
P
i
1
L(t)
= E
2
ryt
L
E
=
LF
t
+ E during t
LF
e
Deflection Yoke Resistance
E
L
t
= 12 s
trace
E
L
=
2t
ryt
L
r
y
t from ”t
64
LF
for
K
2
t
+ E
12
3
<
LF
”, the inductor will once
Deflection Yoke
Inductance (L)
<
V
= 26 s
1
4
P
r
L
” to ”t
”. This phase corre-
y
M
C
2
780V
, the ”L.C” combi-
=
LC
E
2
L
” which is the
1
2
t
TRACE
L I
2
M
23/46
2