REV.-A
2.2.2.5
Protection
Against
Charging
Voltage
Supply
Failure
An overvoltage detection circuit and a reverse-current blocking circuit are provided in order
to
protect
the
batteries and their charging circuits when any abnormal voltage occurs on
the
output
of
the
ac
adaptor;
i.e.,
the
charging voltage. The operations
of
the
circuits are described in
the
fol-
lowing:
(1) Protection against
low
voltage
The diode inserted in the charging circuit in series prevents reverse current
if
the charging vol-
tage falls
below
the
battery voltage.
(2) Protection against overvoltage
If
the voltage
at
the
cathode
of
the
zener diode (VCH) rises
to
+7.5V
or
above,
the
zener diode
breaks
down,
and
protect
the overvoltage condition
for
VB+ line.
VCH
Charge mode control
ZD4
R17
11<
To
port
61
of
~---'--~N\r-----tt------n
4-bit
sub
CPU
7508
Fig.
2-10
Battery
Protection
Circuit
2-16
To Next Page
Loading...
