Panasonic KX-FT21BX, Руководство по обслуживанию

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KX-FT21LA
- 148 -
10. POWER SUPPLY SWITCHING BOARD SECTION
Block Diagram
[Input Circuit]
The input current goes into the input rectifier circuit through the filter circuit. The filter circuit decreases the noise voltage and
noise electric field strength.
[Rectifier Circuit]
The input current is rectified by D101,D102,D103 and D104 and charge 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.
Input
Circuit
AC
Input
Surge
absorber
circuit
G
H
5V
24V
Kick-on
Voltage
Circuit
E
F
GND
Control
Circuit
Over
Current
Circuit
R102
R103
R104
Converter
Circuit
C
D
Over
Voltage
Circuit
8V
Output
Circuit
24V
Output
Circuit
+
-
Rectifier
Circuit
A
B
C106
Error Detecting
Circuit
A-B Voltage Wave Form
0
C-D Voltage Wave Form
0
Voltage Wave Form
0
E-F
G-H
T101
D201
n
2
n
1
V
0
V
1
V
IN
I
IN
Q101 C201
0 t
T
OFF
T
ON
V
IN
V
O
0 t
T
OFF
T
ON
V
IN
V
O
n
1
n
2
Input side
Output side
Input side
Output side
(a) Principle of the RCC method
(b) When the number of transformer windings is one-to-one
(c) When the ratio of the number of transformer windings is n1:n2
Vo is kept constant by varying
the ratio of the time intervals of
T
ON
and T
OFF
.
In Figure (b), different
voltage output can be
obtained by varying the
ratio of the number of
transformer windings.
Load
Vin:T
ON
=Vo:T
OFF
n
1
n
2
Vin:T
ON
= Vo:T
OFF
V
[Convertor circuit]
RCC Method of the Constant Voltage Control
Mechanism
Response to Variations in Input Voltage
Figure A(a) illustrates the principle of RCC.
Assuming T
ON
while Q101 in the
circuit diagram is ON, and T
OFF
while
it is OFF, the voltage generated by the
primary winding can be represented by figures
A(b) and (c).
When the winding ratio is one-to-one, the circuit
functions to make the product of T
ON
and the input
voltage constant with the product of T
OFF
and the
output voltage.
<Fig. A>