TCL SERVICE MANUAL - Tecnicosaurios

STV8172A
Application Hints
4.2 AC-Coupled Applications
In AC-coupled applications (See Figure 6), only one supply (V S ) is needed. The vertical position of
the scanning cannot be adjusted with input bias (for that purpose, usually some current is injected
or sunk with a resistor in the low side of the yoke).
Figure 6: AC-coupled Application
470µF
0.1µF
C F (47 to 100µF)
+Vs
Output
Voltage
6
Power
Amplifier
3 2
Flyback
Generator
Output
Current
I p
7 +
1 -
V m
R 3
V M
4
Thermal
Safety
5
1.5
0.22µF
Rd(*)
Yoke
Ly
R 5
C s
R 4
C L
(*) recommended:
Ly Ly
------------ < R d < -------------
50s 20s
R 2
R 1
4.2.1 Application Hints
Gain is defined as in the previous case:
V – V R M m 2
I p
= ----------------------- ---------------------
2 R 1
R 3
Choose R 1 then either R 2 or R 3 . For good output centering, V 7 must fulfill the following equation:
V V + V S
M m
------- – V
2 7
V – ------------------------
7 V
2 7
--------------------- = ------------------------------------- + -------
R 4
+ R 5
R 3
R 2
or
1
V 7
-------
1 1
+ ------- + --------------------- =
R R 3 2
R 4
+ R 5
V V + V S M m
------------------------------
+ ------------------------
2R 4
+ R 5
2 R 3
STMicroelectronics Confidential 7/14