Samsung SCX-4200 Series Service Manual page 42

System Overview
3.3.6 Functional Requirements of HVPS Control
The engine supplies the developer unit with high voltage through the HVPS unit in order to form the image on the
paper fed through the paper pass. So the engine-control f/w supplies the high voltage to the developer unit at the
specified time and position of the paper during the printing process.
The HVPS unit is controlled by PWM. The output voltage is determined by PWM duty. For reference, PWM cycle is
about 14 KHz presented by the power team.
There are 3 kinds of high-voltages as follows:
3.3.6.1 MHV
This high-voltage is supplied to the OPC drum through the charging roller while charging the skin of the OPC drum
with a minus voltage.
3.3.6.2 THV
3.3.6.2.1 THV +
The (+) transfer high voltage is supplied to the transfer roller to transfer the toner on the OPC drum to the paper. It is
determined by the environmental index.
3.3.6.2.2 THV -
The (-) transfer high voltage is supplied to the transfer roller for cleaning polluted transfer roller by moving the toner
remained a transfer roller to the OPC drum. The value is fixed to about -1000V.
3.3.6.3 DEV
This high-voltage is supplied to the developer roller to move the toner to the skin of the OPC drum scanned by laser
beam while printing the image.
The engine controls if a high voltage is supplied or not and its quantity.
The developer team presents the timing chart to control the high voltage.
3.3.7 Functional Requirements of Power Save Mode
The power save mode is controlled by the main system firmware. In order to switch the ready state to the power
save mode after a specified time, the main system sends a sleep command to the engine. When the engine
receives a sleep command, it stops the operation of the fixing unit and the fan unit in the engine and sets the engine
state as a sleep state. Determination of run or stop operation is different according to the engine status.
A user can select one of pre-defined times as power save time from Driver UI. The setting value for power save
time is OFF, 5min, 10min, 15min, 30min, 45min, and 60min. The default time is 5min. Although OFF is selected,
power save time is operated 2 hours to protect fuser.
Service Manual
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Samsung Electronics