Panasonic KX-FT21BX Service Manual page 11

10. POWER SUPPLY BOARD SECTION (Change from original page 146)
This power supply board uses the switching regulator method.
AC
Input
Input
Circuit
A-B Voltage Wave Form
0
C-D Voltage Wave Form
0
E-F
G-H Voltage Wave Form
0
[Input Circuit]
The input current goes into the input rectifier circuit through the filter circuit. The filter circuit decreases the noise voltage and
the noise electric field strength.
[Rectifier Circuit]
The input current is rectified by D101,D102,D103 and D104 and charges C106 to make DC voltage. Then it supplies power
to the converter circuit.
[Kick-on voltage circuit]
Bias is applied to the Q101 gate via this circuit when the AC power is turned on and Q101 begins operating.
Block Diagram
A
Rectifier
+
C106
Circuit
-
Kick-on
B
Voltage
Circuit
(Model KX-FT21BX/KX-FT21BX-W)
KX-FT21BX/KX-FT21BX-W
R102
Surge
R103
absorber
Converter circuit
Circuit
C
Q101
Surge
absorber
D
circuit
Control
Circuit
IC101
O.C.L
Over voltage
-11-
G
24V
Output
Circuit
5V
Output
Circuit
E
H
F
Error Detecting
Circuit
24V
GND
5V