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13-4. CIRCUIT OPERATION OF CORDLESS BASE UNIT
(1) Power Circuit (charging circuit power supply)
Pins 1 and 8 are switched in the clock period which is determined by capacitor C560 connected to pin 3 of the
switching regulator IC (IC503). The switching output turns Q507 ON or OFF and reduces the 24V voltage to 12V.
Pin 5 of IC503 is the feedback input pin whose input signal is used to stabilize the output voltage.
VT(12V)
(2) Charge Circuit
When the portable handset is places on the charging stand, Q510 is turned ON, and the charging information is
supplied to MPU pin 34 as a logical high signal. When the charging information is supplied to the MPU, the MPU
sends the ID signal from pin 30. This ID signal switches Q509, and it is supplied to the portable handset via the
charging pin of Q509. In the same way, when the spare battery is inserted into the charging stand, Q512, is turned
ON, and the charging information is supplied to MPU pin 33. When both the portable handset and spare battery are
to be charged, the MPU outputs a logical low signal from pin 35 which turns Q513 OFF and also turns Q511 OFF,
thereby limiting the charging current to the spare battery. When only the spare battery is to be charged, the MPU
outputs a logical high signal from pin 35 which turns Q513 and Q511 ON so that the charging current is increased.
C601
C602
C603
CN503
4
+
M
–
5
M
C
–
6
–
M
–
8
+
S
–
7
–
S
–
C605
C606
Circuit Diagram
Q507
L511
+
–
Circuit Diagram
R655
R656
L513
R657
R540
L514
C604
Q509
L515
R661
R662
R663
R664
R565
IC503
VT
D505
Q510
D506
R659
R650
VT
D507
R665
R668
Q511
R548
| 173 |
KX-F910BX
+24V
ANALOG
CN501
(1,2)
+
–
30
34
MPU
(IC501)
Q513
35
Q512
D508
R669
33
R667
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