Laser Diode Drive - Epson EPL-5500 Service Manual

EPL-5500 Service Manual

2.1.2.5 Laser Diode Drive

Figure 2-17 shows the laser diode drive circuit. Laser diode emission is controlled by three signals
(LDATA, LDAPC1, and LDAPC2) from the main board (C169 MAIN-B).
SSCAN
LD_CTL
LDAPC1
LDAPC2
L DATA
Main Board
(C169 MAIN-B)
The LDATA signal is the laser on/off signal. When it is LOW, the laser emits, and when it is HIGH,
the laser stops emitting. LDATA is the combination of the two signals in the figure below. If the
VIDEO or the FORCED LASER DIODE ON signal is activated (LOW), the LDATA signal will be
active. The VIDEO signal is an image signal sent from the video controller circuit. The FORCED
LASER DIODE ON signal is a laser emission signal to apply the laser beam to the SOS sensor.
Forced Laser Diode ON
V I D E O
from the Video
Controller Circuit
(C169 MAIN-B)
The laser diode is forcibly activated after scanner motor M2 turns on. At this time, laser emission
power is adjusted. LDAPC1 and LDAPC2 are the laser emission power adjust signals; they are
analog signals. LDAPC1 is a tuning, and LDAPC2 is a fine tuning.
LDATA
LDAPC1
LDAPC2
P_CTL
Figure 2-19. Laser Emission Power Adjustment Timing
If any of the following conditions are detected, the printer indicates a laser error:
The LDAPC1 signal or LDAPC2 signal has been out of the specified range while laser power is
adjusted.
Rev. B
Figure 2-17. Laser Diode Drive Circuit
Figure 2-18. LDATA Generation Circuit
Scanner Motor On
Laser Diode
LD
SOS
(PWB-D)
SOS Sensor
Operating Principles
SOS Mirror
L DAT A
2-13