Canon Color imageRUNNER LBP5280, Service Manual, Page: 28 / 284

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Technical Reference > Image Formation System > Image Stabilization Control > Image density correction control (D-max control)
Technical Reference > Image Formation System > Image Stabilization Control > Image density correction control (D-max control)
Driving and Controlling the High-Voltage System
■ Outline
The high-voltage power supply generates the high-voltage biases that are applied to the
primary charging roller, developing roller, primary transfer pad, secondary transfer roller and
ITB cleaning unit. The DC controller controls the high-voltage power supply to generate high-
voltage biases.
TR1_1
TR1_23 TR1_23
TR1_4
TR2
BLD1 BLD2 BLD3 BLD4
DEV1 DEV2 DEV3 DEV4
PRI
ICLB
ICLR
Primary charging
bias circuit
Developing bias
circuit
Blade bias circuit
Primary transfer
bias circuit
Secondary transfer
bias circuit
ITB cleaning brush
bias circuit
ITB cleaning roller
bias circuit
High-Voltage Power Supply
DC Controller
Cartridge
Photosensitive Drum
Primary Transfer Pad
ITB
Cleaning Unit
Secondary
Transfer Roller
F-2-14
Image Stabilization Control
■
Overview of the Image Stabilization Control Mechanism
The machine uses its image stabilization control mechanism to prevent lowering of image
quality (e.g., in the form of a faulty image) otherwise caused by changes in the environment
or deterioration of the photosensitive drum or toner.
The machine's image stabilization control mechanism may be any of 3 types: Image density
corrective control (D-max control), Image halftone corrective control (D-half control), Color
Misregistration Corrective Control.
■ Image density correction control (D-max control)
This control is to stabilize the image density of the printer engine.
If the prescribed condition is met, DC controller PCB performs D-max control in the following
procedure.
1. Measure the each density detection pattern made on the ITB.
2. According to the measured density of each pattern, controls the primary charge bias and
developing bias to get the appropriate density.
The following is the conditions that trigger the image density correction control.
The conditions and timing for executing D-max control are shown below.
Conditions for execution Execution timing
At power-on Not executed by default
(*1)
When recovering from deep sleep after 8 hours or more have
passed Not executed by default
(*1)
When the door is closed after replacing the Toner Cartridge Immediately (right after
replacement)
After every 500 pages of printing since the execution of the last
density control
(However, the count of the number of printed pages is reset when
the power is turned OFF or the machine enters deep sleep, and
the count starts again when density control has been executed
after that.) When shifting to idle state
(*2)