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b. Rush current limit circuit
Similarly to the main section, the circuit shown below limits the rush
current which flows into the smoothing capacitor (C792) when the
power is supplied.
R7040
TR702
1K
BCR8PM8
L729
FA702
CL300-300FD
8.2/115 C
R7038
C791
470K
0.047(PA)
(1/4W)
D760
DSS860
Fig. 33 Rush current limit circuit
c. Rectifying/smoothing circuit
Similarly to the main section, the AC voltage of 50Hz (60Hz) is rec-
tified by the rectifier diode (D760) and smoothed by the smoothing
capacitor (C792). The solid line and the dotted line show the path of
the charging current to C792.
R7040
TR702
1K
BCR8PM8
FA702
6.0/115
R7038
C791
470K
0.22(PA)
(1/4W)
DSS860
Fig. 34 Rectifying/smoothing circuit
d. Invertor circuit (Chopper regulator circuit)
RT
6
OSC
CT
5
DEAD
0.2
time
4
control
Error amp1
+IN
1
+
A1
PWM comparator
-
-IN
2
+IN
16
+
A2
-
-IN
15
Error amp2
Feed
3
back
Fig. 35 IC712 block diagram
D768
ERA9102
R7053
C7017
47(1W)
0.01/50V(RPE)
R7045
C796
47(1W)
470P/1KV(MR)
R7109
Q714
2SK1168
10K
(1W)
Fig.45
R7046
R7042
220(1W)
10K(1W)
D762
R7043
10K(1W)
RO27EB1
R7047
C794
10(1W)
22(PF)
PC706
R7053
C7017
47(1W)
0.01/50V(RPE)
R7109
10K(1W)
R7042
10K(1W)
R7043
D760
10K(1W)
PC706
Output control
13
8
C1
Q
T
9
E1
Q
11
C2
Pulse steering F/F
10
E2
12 VCC
Reference
14 VREF
regurator
7 GND
R7054
47(1W)
C795
470P/1KV(MR)
T704
N-T01-014
D763
2
+IN1
-IN1
F.B.
D.T
CT
RT
GND
C1
After rectifying and smoothing the AC power, the copy lamp voltage is
stabilized by the voltage-fall type chopper circuit (same as the chop-
per in the main section).
The switching frequency generates triangle waveforms of about
50KHz by CR connected to IC712 5pin and 6pin.
TR1
TR2
Fig. 36 Switching waveform in each section
9 – 29
TOP VIEW
1
+
+
16 +IN2
A1
A2
2
-
-
15 -IN2
3
14 VR
4
13 O.C
5
12 VCC
OSC
TR2
6
11 C2
7
10 E2
TR1
8
9 E1
0V
TR1, TR2 (9)(10) pin
voltage waveform
0V
Q717 collector < > emitter
voltage waveform
Switching FET (Q714)
0V
drain < > source voltage waveform
Switching FET (Q714)
0V
drain current
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