User manual

95.08.23.11.29
Color LaserWriter 12/600 PS Basics & Theory 1–34
Laser Control Circuit
Laser Emission The DC controller generates 8-bit video data signals (
DV2-DV9) and
mode setting signals (
M1-M8) in the gate array (IC109) in accordance
with the video signals (
VDO0-VDO7) and image mode select signal
(
IMCHR) sent by the I/O controller. It sends those signals to the PWM-
IC in the laser driver board. Based on the above signals, the PWM-IC
produces laser drive signals with the pulse width corresponding to the
halftone, and then sends them to the laser driver circuit. At this time,
when the forcible laser-on signal (
/LSON) sent to the laser driver circuit
is “H” and the video-enable signal (
/VDOENB) is “L,” the laser driver
board turns the laser diode on in accordance with the laser drive signal.
Note: The APC-IC monitors the voltage levels of the 5 V and 24 V
power supplies. If both voltage levels exceed the specified value, the
laser driver board uses 12 V power supply produced from the 24 V
power supply.
G.A.
(IC109)
M1 to 8
PD
LD
/VDOENB
Dv2 to 9
CPU
VDO7 to 0
Switching Circuit
Current/Voltage
Conversion Circuit
APC-IC
Constant
Current Circuit
/LSON
LLCNT
PDIN
Laser Drive Dignal
APCENB
APCLW
APCUP
PD
BD Board
/BDI
/TOP
/LSYNC
12VON
(IC103)
(IC101)
IMCHR
+5V
+12V
Laser Driver
Circuit
(IC403)
PWM IC
Laser Driver
Board
DC Controller Board