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Circuit Description
Supplied current is converted to voltage by R21.
U22A compares this to the reference, which is
divided voltage by r30, r31 and r28, and transfers
difference to PWM control circuit by U21 and OP1.
so this charger offers constant current to battery.
U23B compares the voltage of Term. #6 to it of
Term. #5, this is reference and that is sampling
voltage of battery.
U23B makes U24A to ON state by decreased the
voltage of U24A Term. #2 until that battery
voltage is increased to wanted voltage.
This is preventing error which is causes difference
of charger and battery temperature.
The voltage of U24A Term. #2 is recovered by the
high output from U23B when battery voltage is
increased to wanted voltage.
When battery is closes to full charge, the
temperature in battery pack increases. Full
changing signal is by detecting dT.
4-16
dT detecting : U24A compares the voltage level
between Term. #2 and Term. #3, Term. #2 is
reference which is changed on ambient
temperature and NTC which is in unit, Term. #3
senses battery temperature.
this circuit is to reduce charging tolerance that is
caused by ambient temperature.
When the voltage of U24A Term. #2 is higher than
it of Term. #3, q21 and Q20 are OFF state. At this
time, 25mA trickle current follows.
OUT-A
OUT-B
L
U23
L
U24
The latch circuit is consisted of q22, r36 and U24A.
this relaxes by battery replacement or AC power
ON-OFF.
q21
q20
H
OFF
OFF
h
Samsung Electronics
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