REV.-A
The diode, inserted across the signal line and ground, clamps the signal
to
the ground level. eli-
minating the negative component.
While
the positive component is fed back
to
the auxiliary bat-
tery via the other diode D14.
Sub
CPU
7508
P70
--k1f---~
P42
R48
47K
R6
220
...--
___
V8
Return voltage
from
LCD
o--------1----------------
........
-----4H~
III
regulator J
'"'11
I I -
Auxiliary battery
~---~~~~~
........
-~
Q20
"-------'_
VB
20K
Fig.
2-19
Feedback
Circuit
Fig.
2-19
is the feedback circuit redrawn
for
clarification. This circuit provides the charging path
to
the auxiliary battery while
power
is on.
7508, P70
(Power control)
7508,
P42
(Main/auxiliary
battery switching)
Feedback voltage
waveform
as
observed
Power
off
•
..------Auxiliary
battery
change----------'~~
1-------..1
Fig.
2-20
Major
Voltages
of
LCD
Drive
Power
Regulator
Circuit
2-25
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