Canon Laser Shot LBP-5100, Service Manual

Page: 69 / 162

Chapter 2
2-35
The low-voltage power supply circuit serves to convert the AC voltage coming from the power receptacle into DC power for provision to various loads. The fol-
lowing is a block diagram of the circuit:
F-2-38
The AC power is supplied to the low-voltage power supply circuit when the power switch (SW801) is turned on.
The AC power supply is then converted into +24V, +5V, +3.3V, and +2.5V, which are DC power used by the printer engine.
The following shows the major destinations of +24V, +5V, +3.3V, and +2.5V:
+24V: motors, solenoids, high-voltage power supply PCB, memory controller PCB, accessories
+5V: laser driver PCB, sensors other than photointerrupters
+3.3V: video controller, sensor (photointerrupters), control panel, DC controller PCB, memory controller PCB
+2.5V: ASIC, video controller
2.7.1.2 Other Function
2.7.1.2.1 Protective Functions
0010-6166
LBP5000 / LBP5100
The low-voltage power supply circuit is equipped with an over-current protective mechanism and an over-voltage protective mechanism used to automatically cut
the output voltage in response to an over-current or over-voltage caused by a short circuit on the load side.
If the low-voltage power supply does not generate DC voltage, therefore, it is likely that the over-current protective mechanism or the over-voltage protective mech-
anism has gone on: turn off the power switch (SW801), remove the cause of the activation, and then turn the power switch back on.
In addition to these, the circuit is provided with 2 power fuses (FU801, FU901). In response to over-current in the AC line, these power fuses will blow to cut the
power.
Fixing
control
circuit
Power supply unit
+24VA
+24VA
+24VB
Scanner motor
Pick-up motor
Fixing/Delivery motor
Main motor
Solenoids
High-voltage power
supply PCB
Power switch
(SW801)
DC controller PCB
Low-voltage power
supply circuit
Rectification
circuit
Noise filter
Overcurrent/Overvoltage detection circuit
(+2.5V detects overcurrent only)
+24VA
+3.3V
Switching
circuit
DOPEN
Fan motor
+24VA
Fuse
(FU801)
Fixing unit
+24VA
+5V
+24VA
Video controller PCB
+3.3V
+5V
Laser driver
Color misregistration
/Density sensor
+5V
+3.3V Sensors
(photo interrupter)
ZEROX
Memory controller
PCB
Door open detection
switch (SW100)
+3.3V
Paper feeder
(option)
+24VA
Environment sensor
+5V
+3.3V
Control panel
REM24V
200V only
+3.3V
+2.5V
+2.5V
+5V
100V only
Transformer
(T101)
+24V
power supply
converter
+3.3V
power supply
converter
+2.5V
power supply
converter
+5V
power supply
converter
IC7
CPU
ACN
ACH
Fuse
(FU901)
Zero crossing
circuit