Epson LQ-1170 - Power Supply Operation; Power Supply Overview; Supply Circuit Operation

REV.-A
2.2 POWER SUPPLY OPERATION
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The printer can be powered by either of two power supply boards: the 120 V C060 pSB board or the
220/240 V
C060 PSE board. The only difference between these boards is in the Primary circuitry. The
ways in which they supply power to the printer are identical. These power
SUPPIY boards output the
DC current necessary to drive the printer control circuits and the printer drive mechanism. Table 2-3
shows the input voltages and fuse ratings for these boards.
Table 2-3. Power
Supply Boards
. . .
Board Input Voltage (VAC) Fuse F1 Rating
C060 PSB
103.5 to 132 2.5A
\ 125 V
C060 PSE 198 to 264
1.25A
I 250 V
2.2.1 Power Supply Overview
The power supply board has two power output lines that supply power to the various control circuits
g;
and drive mechanisms. Table 2-4, lists the parts of the printer that run off these two DC output supply
voltages.
2.2.2 supply
Table 2-4. Power Supply Output Voltages and Applications
Output Supply Voltage (DC)
Applications
+35 v
Carriage motor drive
I Paper advance motor drive
Printhead drive
+5
v C060 MAIN board logic circuitry
I
Various sensors
Control panel LEDs
I Pa~er advance motor hold
Circuit Operation
Figure 2-16 shows the power supply circuitry in block diagram form. AC power feeds into the printer
(:’
from the external power source. A filter circuit removes the noise. The AC voltage then undergoes full
wave rectification and is smoothed to produce the direct current supply voltage. This voltage is fed
through a switching circuit and secondary smoothing circuit to produce the stepped down +35
VDC
supply. A
+35 V line voltage detector circuit is connected to the switching circuit. This feedback control
arrangement ensures that the +35
VDC supply remains stable.
The + 5
VDC supply is achieved by feeding the +35 VDC line through the + 5 VDC power supply circuit.
This circuit further steps down the +35
VDC voltage and outputs a stabilized + 5 VDC supply.
There are four circuits to protect the supply circuitry and avoid danger. The + 5
VDC line contains a
current overload protection circuit and a voltage overload protection circuit. The current overload
protection circuit is part of the +5
VDC supply circuit. It cuts the + 5 VDC line if the current is too great.
The + 5 V voltage overload protection circuit cuts the supply if the voltage reaches or exceeds +7 VDC.
It stops switching circuit operation, which stops the output of the
+35 VDC line.
2-12