Behavior Of Electric Power Failure; Supply From Handset; Supply From Large Capacitor - Panasonic KX-TG8162ALB Service Manual

4.8.

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.
4.8.1.

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 condi-
tion.
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.
Battery
R45
BBIC
4.8.2.

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.
HANDSET
Q10
R13
71
R12
IC1
R903
82
BBIC
IC501
R923
71
CHG+
R351
CHG-
Q353
Q11
R353
R11
Vbat
R906
R901
R917
Q902
Q901
R902
C901
R907
Q903
17
KX-TG8162ALB/KX-TG8163ALB/KX-TGA815AZB
BASE
Vbat
Q351
R352
R355
Q354
R360
Q352
R354
R918
R925
Q905