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3DQDVRQLF
1.4.2 Drive circuit part
The deflection coil drive circuit part can be represented by the following figure 27
V dri (-)
L302
47
I501
I1
TDA8844
L301
46
I2
V dri (+)
The vertical drive currents of TDA8844 pin 47 and 46 are connected to input pins 1 and 2 of the
TDA8356. The currents are converted into a voltage (called thereunder the drive voltage) by a resistor
(R302) between pins 1 and 2. Pin 2 is on a fluted DC level (internal bias voltage) Pin 1 includes the
drive voltage and the DC internal bias voltage.
The drive voltage is amplified by 'A' and fed to two amplifiers 'B' and 'C', one is an inverting amplifier
and the other is a non inverting amplifier.
The outputs (pin 7: V
0(A)
coil and feedback resistor. The voltage across feedback resistor is 134 via pin 9 to correction amplifier
'D', to obtain a defection current which is proportional to the drive voltage.
Vp
3
+Vp
I301
TDA8356
-I
I dri (+)
1
Idiff
+
A
R302
-
2
+V
I dri (-)
+I
5
GND
Fig.27 : TDA8356 block diagram
and 4. V
) are connected to the series connection of the vertical deflection
0(B)
V0(guard)
V FB
8
6
CURRENT
+
SOURCE
-
+Vp
+
B
-
S
+I
T
+
D
-
-I
+Vp
S
T
-
C
+
30
V0(A)
7
I
Y
Deflection Coil
L Y
Vi(FB)
9
R304
//
R305
V0(B)
4
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