Control Circuits; Zero Cross Sync Generator; Acp1 - Canon LBP-CX Series Service Manual

4. Control circuits
a. Zero-cross sync generator
0501
COM ,;:.
>it>
L ----
--J5~:J
DC power supply & main
motor driver
ACP
GND
I
R27~ ~
;o
~
-
IC218 +5V
0
N
CI:
10
I
J208-
11
R271
ACP1
26
Figure 3-42 Zero-cross sync generator
1)
Introduction
The zero-cross sync generator full-wave rectifies
the AC voltage, transforms it into a pulse, and inputs
the AC pulse to IC208 of the microcomputer. The
microcomputer uses the AC pulse as a timing signal to
tum on the fixing heater HI at zero-cross.
2) Operation
The AC line voltage
is
transformed to low-voltage
AC output by transformer PTl and applied to rectifi-
cation elements DSOl and D502. DSOl and D502
full-wave rectify the AC output and apply the signal
(ACP) to comparator IC218 on the DC controller.
IC218 compares the reference voltage (Vref) gener-
ated by R273 and R274 with the voltage of the full-
wave rectified output (ACP). If ACP is lower than
Vref, IC218 sends a positive pulse (ACPl) to IC208
pin 26.
Line voltage
ACP
ACP1
(IC208-26)
/\ r
~D
OV
About 0.7V
Figure 3-43 ACP 1
COPYRIGHT
©
BY CANON lllC. CANON LBP·CX SERIES REY.2 JULY 1985 PRINTED IN JAPAN (IMPRIME AU JAPONJ
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