72
UF-5500 / 4500
6.18. Power Supply Board Section
The power supply board circuit gen7V and +24Vdc. It also supplies AC voltage to the halogen heat lamp in the fuser
unit. The power supply board uses the switching regulator method.
[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 circuit is rectified by D1 and charge C5 to make DC voltage.
Then it supplies power to the converter circuit.
[Kick-on Voltage Circuit]
Bias is applied to the Q1 gate via this circuit when the AC power is turned on and Q1 begins operating.
[Over Current Limiter (O.C.L)]
The highest drain current of Q1 is limited by a limit current circuit. The 24V output is limited by this circuit.
[Over Voltage Circuit]
If the 24V output increases because the error detecting circuit or control circuit is broken.
Control circuit will recognize this signal and output becomes 0V. D104 and D503 also prevent over voltage.
Dummy load method (to quickly check the power supply output)
Refer to
Input
Circuit
AC
Input
C5
G
H
24V
Kick-on
Voltage
Circuit
E
F
7V
HTRCTL
GND
Control
Circuit
R4
R3
R2
Converter
Circuit
C
D
Rectifier
Circuit
A
B
+
Error Detecting
Circuit
O.C.L
Q1
A-B Voltage Wave Form
C-D Voltage Wave Form
E-F
G-H Voltage Wave Form
0
0
0
T1
PC1
Triac
SCR51
Heat Lamp
Photo Triac
Coupler PC2
Block Diagram
+
+
F101
R41
Summary of Contents for UF-4500
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