Electrical Circuit Operation Principles; C265 Psb/Pse Power Supply Board - Epson Stylus Color 980 Service Manual

EPSON Stylus Color 980

2.3 Electrical Circuit Operation Principles

The Stylus Color 980 consists of the following circuit boards:
C380 main board
C265 PSB/PSE board
C265 Panel Board
Operating Principles

2.3.1 C265 PSB/PSE Power Supply Board

This section explains the operating principles of the C265 PSB/PSE
board, in order.
AC power supply voltage is supplied from the AC power socket. Then
the fuse (F1) limits the incoming current of the AC voltage to avoid
damaging the C380 main board and C265 PSB/PSE board. On the
other hand, TH1 and TH2 serve to convert surplus input voltage into
heat energy.
The input voltage is next input to the RLC parallel circuit (a filter circuit),
for higher harmonics absorption. This operation keeps the higher
harmonics in the AC power out of the printer, and also prevents leakage
of higher harmonics generated in the printer.
After noise is removed, the AC voltage goes through the full-wave
rectification circuit. The minus component of the alternate wave is
eliminated as the result.
Then the voltage is smoothed by the electrolysis condenser (C11) for
stabilized DC voltage, and the current is applied to the primary side of
the transformer (T1).
The current, however, does not flow into the primary side of the
transformer (T1) if the main switching FET (Q1) located in the primary
side is off. The Q1 comes on when the voltage is applied to the gate
through the R28, a starting resistor, when the printer is turned on. While
the Q1 is on, current does not flow into the secondary side; because a
reverse-characteristics diode is used to connect to the secondary side.
The transformer (T1) is gradually charged with the current. When it is
full and not charged any more, the gate voltage of the Q1 starts going
down gradually. At this point, C13 abruptly pulls in the gate voltage of
the Q1 to turn the Q1 off.
Electrical Circuit Operation Principles
Revision A
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