Samsung SCX-5315F Service Manual page 154

Circuit Description
3-5-7-7. Environment Recognition
THV voltage recognizes changes in transfer roller environment and allows the voltage suitable for the envi-
ronment in order to realize optimum image output. The analog input is converted to digital output by the
comparator that recognizes the environmental changes of the transfer roller. It is to allow the right transfer
voltage to perform appropriate environmental response considering the environment and the type of paper
depending on this digital output by the programs that can be input to the engine controller ROM.
This environment recognition setting is organized as follows: First, set the THV(+) standard voltage.
Allow 200MΩ load to transfer output, enable output and set the standard voltage 800V using VR201.
Then set 56 (CPU's recognition index value) as the standard using VR302.
This standard value with CPU makes sure that the current feedback is 4µA when output voltage is 800V and
load is 200MΩ.
If the load shows different resistance value when 800V is output, the current feedback will also be different
and thus the index value will also be different. according to the index value read by CPU, the transfer voltage
output will differ according to the preset transfer table.
The changes in transfer output required by each load is controlled by PWM-DUTY.
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