Canon MF720 Series Service Manual page 35

■ Open door detection
This product detects door opening by the door open sensor.
Sensor Name
Front Cover Sensor (SR612)
Rear Cover Sensor (SR613)
When this sensor detects door opening, the DC controller stops driving motors and solenoids.
■ Low-Voltage Power Supply Control
This circuit converts AC voltage input from the power supply receptacle through the fixing power supply into DC power supply
and supplies it to each load.
See the figures below for low-voltage / fixing power supply block diagrams.
• Low-voltage power supply: generates DC power supply required in the printer.
• Fixing power supply: supplies AC power supply to the low-voltage power supply and control the fixing heater temperatures.
The low-voltage power supply is actuated when the AC power supply is attached to the inlet and the power switch is turned on.
The AC power supply supplied through the fixing power supply is converted to + 24V and + 3.3V of the DC power supply in the
low-voltage power supply before supplied to the printer engine.
AC input
Fuse
FU1101
■ Protective control
The low-voltage power supply has protective controls against excessive current and voltage, which automatically detect excessive
current or abnormal voltage to shut off the output voltage for avoiding the power supply circuit failures.
In case the DC voltage output is not detected from the low-voltage power supply, the protective control may be activated. Turn
off the power switch and remove the AC power supply from the inlet to settle load troubles. Once these are settled, turn on the
power switch again.
Another protective control is provided by 2 power fuses on the fixing power supply. These are open when excessive current is
detected to shut off power supply to low-voltage power supply.
■ Power-Saving Mode
This is the function to save power consumed by the printer.
The table below lists various power-saving modes.
Detect open the Front Cover.
Detect open the Rear Cover.
Fuse
FU1201
Noise Filter
Power
Switch
SW1
Fuse
FU1102
Noise Filter
Rectifying
Circuit
+24V
Generation
Circuit
Protection
Circuit
+3.3V
Generation
Circuit
Function
Fixing Power Supply
Fixing
Control
Circuit
Low-voltage Power
Supply (all night)
Frequency
Detecting
Circuit
24V DCON
24V REM
3.3V DCON
24V
24S_ON
DCON_ON
3.3V
27
2. Technical Explanation
DC
Controller PCB
Main
Controller PCB