Power Supply Operation; Power Supply Overview - Epson LQ-2170 Service Manual

LQ-2170 Service Manual

2.2 POWER SUPPLY OPERATION

The printer can be powered by either of two power supply boards: the C165 PSB (120 V) or C165 PSE (230
V) power supply. These boards are the same for both the LQ-2170 and FX-2170. Additionally, the PSB and
PSE boards function the same, except for a difference in primary circuitry. The power supply board outputs
the DC current necessary to drive the printer control circuits and drive mechanism. Table 2-5 shows the
input voltages and fuse ratings for these boards.
Board
C165 PSB
C165 PSE

2.2.1 Power Supply Overview

The power supply board has two power outputs for use by the various control circuits and drive mechanisms.
Table 2-6 lists the applications for the two DC output supply voltages.
Table 2-6 Power Supply Output Voltages and Applications
Output Voltage (DC)
+5 V
+35 V
Figure 2-22 shows a block diagram of the power supply circuitry.
Primary Circuit
Full Wave
Rectification
Circuit
Filter Circuit
AC input
Figure 2- 22 Power Supply Circuit Block Diagram
As shown in the figure above, when AC power enters the printer from an external power source, the filter
circuit removes the noise. The AC voltage then undergoes full-wave rectification and is smoothed to produce
direct voltage. The voltage is fed to the gate port for the switching FET (Q1: K1531 or K1692) through
resistors R18 and R31, and then the switching circuit operates. The secondary smoothing circuit produces a
stepped down +35 VDC voltage. The +5 VDC voltage is generated by feeding the +35 VDC voltage through
the +5 VDC power supply circuit, where the +35 VDC is stepped down to a stable +5 VDC from the 35 VDC
line.
Rev.A
Table 2-5. Power Supply Board
Input Voltage
103.5 to 132 VAC
198 to 264 VAC
Main Board Logic Circuit
CR Motor
Switching Smoothing
Smoothing
Circuit Circuit
Circuit
Photo-
Coupler
Photo-
Coupler
Fuse F1 Rating
6.3 A / 125 V
T3.15 AH / 250 V
Applications
Sensors
PF Motor
Secondary Circuit
+5V Switching
Regurator
+5V Constant Voltage
Control Circuit
+5V Over current
Protection Circuit
+35V Line
Over Load
Detector Circuit
+35V Line
Constant Voltage
Control Circuit
+35V Line
Over Voltage
Protection Circuit
+5V Line
Over Voltage
Protection Circuit
+35V Line
Over Current
Protection Circuit
Operating Principles
Control Panel LEDs
Printhead Drive
+5V DC
+35V DC
CPU
Port 20
Operation
SW
2-17