Canon LBP 2460 Service Manual - Page 67

CHAPTER 2 D. Power Supply 1. Outline AC power is supplied to the low-voltage power supply when the main switch (SW101) is turned ON. The low-voltage power supply generates the required +24VDC and +5VD for the printer. +24VDC is supplied to the high-voltage power supply PCB to drive the main motor, scanner motor, and fans. +5VDC is used for sensors and ICs on the DC controller PCB. +24VDC is divided into +24VA which is normally supplied from the power supply and +24VB which is shut OFF when the door switch (SW1401) turns OFF when the upper or delivery covers are opened. +5VDC is divided into +5V which is normally supplied to the ICs on the DC controller PCB from the power supply and +5V for power-saving mode (P5VB1, P5BV2, P5VB3, and P5VBDOR). Supply of +5V for the power-saving mode is stopped when the sleep command is received from the video controller. During standby mode and periods when printing is not possible (when /RDY signal is "H"), the +5V is supplied off and on. The DC controller PCB generates +5VC and supplies it to the laser driver. This is shown in the block diagram below. Power supply Circuit Noise breaker filter Relay Power switch (SW101) Current fuse Triac Surge current reduction Triac resistor Triac Surge current reduction Triac resistor To fixing roller heater Phototriac coupler Phototriac coupler Phototriac coupler Phototriac coupler Current transformer Current transformer Safety circuit Heater drive circuit Noise filter Voltage-raising converter Rectification smoothing circuit Control IC Transformer Rectification smoothing circuit Switching FET Operational amplifier Control IC Constant-voltage control photocoupler Error state latch photocoupler FET FET Control IC Input voltage detection circuit Low-voltage power supply circuit Input voltage detection photocoupler DC controller FSRTH RLD /FSRD1E /FSRCT1 /FSRD1 /FSRD1R /FSRD2E /FSRCT2 /FSRD2 /FSRD2R /RLDSNS +24VA /REMT 24 +5V PSTYP +5V Laser driver +5V BD PCB +24VA Scanner motor +24VB High-voltage power supply +24VB Main motor +5V Sensors +24VA Solenoids Clutches +5V Operation panel Switch /sensor PCB +24VB +24VA Door switch (SW1401) : 220-240V ONLY Figure 2-2-13 2. Protective Function If a short circuit or other problems on the load side cause an excessive current flow from the +24VDC or +5VDC power supplies, the excess-current protection system automatically shuts off the output voltage to protect the power supplies. 2 - 21