High Voltage Power Supply - Xerox WorkCentre Pro 412 Service Manual

Circuit Description

5-7-7 High Voltage Power Supply

5-7-7-1 Summary
It is the high voltage power supply that has DC+24V/DC+5V (used for the image forming device in OA dig-
ital picture developing method) as the rated inputs. It supplies electrifying voltage (MHV), supply voltage
(SUPPLY), developing voltage (DEV), blade voltage (BLADE) and transferring voltage (THV).
Each high voltage supply shows the voltage required in each digital picture process.
5-7-7-2 Digital Picture Process
Digital picture developing method is widely used by copy machine, laser beam printer and fax paper.
The process is comprised of electrification, exposure, develop, transfer and fixing.
First, in the electrification process, retain constant charge at approximately -900V for the electric potential
on the OPC surface by electrifying OPC drum at approximately -1.4KV through the electrification roller.
The electrified surface of OPC is exposed responding to the video data by the LSU that received print
command due to rotation. The unexposed non-video section will retain the original electric potential of -
900V, but the electric potential of the image area exposed by LSU will be approximately -180V that it will
form the electrostatic latent image. The surface of the photo-conductive drum where the electrostatic latent
image is formed reaches the developer as the drum rotates. Then the electrostatic latent image formed on
the OPC drum is developed by the toner supplied to the developing roller by supplying roller and it is trans-
formed into visible image. It is the process to change the afterimage on the OPC drum surface formed by
LSU into visible image by the toner particles.
While the supply roller energized with -450V by HVPS and the developer roller energized with -300V
rotate in the same direction, it keeps the toner particles between two rollers supplied to OPC drum in neg-
ative state by the friction between two rollers.
The toner supplied to the developer roller is biased to bias electric potential by the developer roller and
transferred to the developing area. After (-) toner is attached to the developer roller, it will move to the
exposed high electric potential surface (-180V) rather than to the unexposed low electric potential surface
(-900V) of the developer roller and OPC drum. Eventually the toner will not settle in the low electric poten-
tial surface to form the visible image.
Later, the OPC drum continues to rotate and reaches to transfer location in order to accomplish the trans-
fer process.
5-60 3/03 WorkCentre Pro 412, FaxCentre F12 &
WorkCentre M15/M15i