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KX-TG6811UAB/KX-TG6811UAM/KX-TG6812UAB/KX-TG6821UAB/KX-TGA681RUB/KX-TGA681RUM
4.7.
Behavior of Electric Power Failure
This model can operate in power failure state by two temporary power sources.
One is supply from handset, the other is supply from large capacitor.
One is supply from handset, the other is supply from large capacitor.
4.7.1.
Supply from handset
When AC power is lost, base unit sends power failure information to handset. BBIC(IC1) turns Q11 on and, battery voltage appear
to CHG terminal.
When CHG+ (supply voltage from handset) is higher than Vbat, Q351 is on. And, this unit continues working in power failure
condition.
It's possible to use the units during the power failure, supplying power to VBAT of base unit from battery of handset through Q10,
CHG terminal and Q351.
If emitter voltage is lower than collector, Q351 is OFF for the backflow prevention.
to CHG terminal.
When CHG+ (supply voltage from handset) is higher than Vbat, Q351 is on. And, this unit continues working in power failure
condition.
It's possible to use the units during the power failure, supplying power to VBAT of base unit from battery of handset through Q10,
CHG terminal and Q351.
If emitter voltage is lower than collector, Q351 is OFF for the backflow prevention.
4.7.2.
Supply from large capacitor
This model has PAS capacitor (CAP) to keep talking for only a limited time under the sudden power failure state.
CAP is charged at 2.5V in standby mode and charged at up to 3.0V in talk mode. Charge voltage is controlled by Q901 and Q902 to
extend the life time of CAP.
In case that the power from AC adapter is lost, BBIC(IC501) turns Q901 ON instantly and CAP supplies current to Vbat.
CAP is charged at 2.5V in standby mode and charged at up to 3.0V in talk mode. Charge voltage is controlled by Q901 and Q902 to
extend the life time of CAP.
In case that the power from AC adapter is lost, BBIC(IC501) turns Q901 ON instantly and CAP supplies current to Vbat.
HANDSET
BASE
R45
Q11
R11
Q10
R12
R13
BBIC
IC1
71
Battery
Q12
R10
Vbat
Q353
Q354
R351
R352
R353
R354
R360
Q352
R355
Q351
CHG+
CHG-
R323
R321
R322
R341
R373
R359
R920
Q904
R904
R919
30V
C363
C362
C361
Q704
+5.5V
R707
R708
5.5V
CHG+
BBIC
IC501
Vbat
R903
R923
R906
R918
R925
Q905
R917
R907
Q903
R902
R901
Q902
Q901
C901
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