Qls 21M62US (CHASSIS: NX56-LA) Service Manual page 56

Application Hints
4.1.1.1 Centering
Display will be centered (null mean current in yoke) when voltage on pin 7 is (R
4.1.1.2 Peak Current
Example: for V
Choose R
From equation of peak current:
Then choose R
Finally, the bias voltage on pin 7 should be:
4.1.2 Ripple Rejection
When both ramp signal and bias are provided by the same driver IC, you can gain natural rejection
of any ripple caused by a voltage drop in the ground (see
same fraction of ripple voltage to both booster inputs. For that purpose, arrange an intermediate
point in the bias resistor bridge, such that (R
capacitor between the intermediate point and the local driver ground. Of course, R
connected to the booster reference point, which is the ground side of R
Reference
Voltage
R
Ramp
Signal
Driver
Ground
6/14 STMicroelectronics Confidential
=
V 7
=
I P
= 2 V, V = 5 V and I
m M
in the1 W range, for instance R
1
or R . For instance, if R
2 3
V M +
V 7 =
------------------------
2
Figure 5: Ripple Rejection
R
9 8
R
7
R
3
+
V M V m R 2
æ ö
´
ç ÷
------------------------ --------------------- -
+
2 R 2 R 3
è ø
( )
–
V M V m R 2
´
---------------------------- - ------------------ -
2 R xR
1 3
= 1 A
P
=1 W
1
´ ´
R 2 2 I P R 1
2
------- = ---------------------------- - = -- -
R 3 – 3
V M V m
= 10 kW, then R
2
V m
7
1 1
´ ´
= =
----------------- --- - ------- -
R 2 2.5
3
1 + -------
R 2
Figure
/ R ) = (R / R
8 7 3
6 3
Power
Amplifier
7
+
1
-
Thermal
Safety
4
Source of Ripple
is negligible):
1
= 15 kW
3
1.4V
5), if you manage to apply the
), and connect the bias filtering
2
.
1
2
Flyback
Generator
5
Rd
R
2
R
STV8172A
should be
7
Yoke
Ly
1