Service manual

EPSON Stylus COLOR 480 Revision B
Operating Principles Electrical Circuit Operating Principles 45
Figure 2-17. C301PSB/PSE Board Block Diagram
The C367 PSB/PSE board has the various control circuits to stop voltage output if a
malfunction occurs on the power supply board or the main board while the printer
mechanism is on duty. Following explains each control and protection circuit.
o +42V line constant voltage control circuit:
The output level of +42V line is monitored by a R92, R93,Q91,ZD51.
When + 42V line reaches about 42.5V, ZD51 has a continuity with and PC1 start
the operation via Q91. Consequently, Q1 switching operation is controlled by this
circuit to stabilize the 42V line.
o +42Vline over voltage protection circuit:
The output voltage line is monitored by ZD52,ZD87. If the output level of the
voltage level of +42DC line exceeds +48V, this circuit stops the operation of the
switching FET Q1 via PC1,Q82,Q83 and prevents high voltage from applied to the
secondary side
o +42Vline over current protection circuit:
The output voltage is monitored by the F51. When the abnormal current is
detected by F51, F51 is fused and cut off the +42V line output to the Main board
o +5V line constant voltage control circuit/+5V line over current protection circuit:
The output level of the +5VDC line voltage is monitored by the regulator IC51. If
abnormal voltage is detected, the information is fed back to the internal
comparator.
o +5V line over voltage protection circuit:
The output voltage level of the +5V line is monitored by ZD53.
If the output level of the voltage level of +5DC line exceeds +7V, this circuit
stops the operation of the switching FET via PC1,Q82,Q83and prevents high
voltage from applied to the secondary side.
F1
C11
L1
DB1
TRANS(T1)
O ver C urrent
Protection
F ilte r C ir c iu t
Full W ave
R ectifier circuit
Sm oothing
Circuit
M a in S w itc h in g
Circuit
Q1
Abnorm al
Feed back circuit
Q2,Q3
Photo
C oupler
PC1
D51
AC Input
Sm oothing
Circuit
C51
+42V D C Line
C onstant C ontrol
R 92,R 93,Q 91,ZD 51
+42V D C Line
O ver Voltage
L im ita tio n
ZD52,87
+5V R egulator
IC 5 1
+42 V D C
+5 VD C
+5VD C Line
O ver Voltage
L im ita tio n
ZD53
+42V D C over
c u rre n t p ro te c tio n
F51