High Voltage Power Supply - Samsung SCX-5315F Service Manual

3-5-7. High Voltage Power Supply

3-5-7-1. 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.
3-5-7-2. 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.
HEAT ROLLER
PRESSURE ROLLER
First, in the electrification process, retain constant charge at approx. -900V for the electric potential on the
OPC surface by electrifying OPC drum at approx. -1.4KV through the electrification roller.
The electrified surface of OPC is exposed responding to the video data by the LSU that received print com-
mand 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 approx. -180V that it will form the electro-
static 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 transformed into
visible image. It is the process to change the afterimage on the OPC drum surface formed by LSU into visi-
ble 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 nega-
tive 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 potential surface to
form the visible image.
Later, the OPC drum continues to rotate and reaches to transfer location in order to accomplish the transfer
process.
This process transfers the (-)toner on the transfer roller to the printing paper by the transfer roller. The (-
)toner attached to the OPC drum will be energized to hundreds to thousands of the (+)transfer voltage by
HVPS. The (+)electrostatic force of the transfer roller generated has higher adhesiveness than the (-)toner
OPC drum and thus it moves to the surface of the paper passing through the transfer roller.
The toner transferred to the paper with weak electrostatic force is fixed to the paper by the pressure and heat
of the fixer composed of pressure roller and heat roller.
The toner attached to the paper is melted by applying the heat (approx. 180°C) from the heat roller and the
pressure (approx. 4kg) from the pressure roller. After the fixing process, the paper is sent out of the set to
finish the printing process.
Samsung Electronics
LSU
MHV
ELECTRIFICATION
ROLLER
TRANSFER ROLLER
- This Document can not be used without Samsung's authorization -
BLADE
SUPPLY
DEV
SUPPLY ROLLER
DEVELOPER ROLLER
DIRECTION OF PAPER
THV
Circuit Description
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