Epson SQ-B50/2550 Technical Manual page 127

REV.-A
• Printer head voltage supply circuit
This circuit transforms the 24VDC source power supply up to a range of 93-160VDC to supply the
printer head voltage. Control of the head drive requires the ink temperature as its parameter. The
ink temperature detected by the thermal resistor in the ink cartridge is fed back to the constant voltage
controller.
• Main circuit:
The main circuit is shown in Figure 2-67. For more details, refer to the SEIMA board circuit diagram,
location 9-10/1. The circuit employs the DC-DC converter method. The
+
24VDC supplied to the
primary stage of the voltage transformer T1 is controlled by the switching motion of the chopper
switching controller 494 (3C). Two error amplifiers, EA 1 and EA2, form the constant voltage control
and current limit circuits, respectively, of the main switching board.
Dl0
C42
GH
•
r - - - -
I
:.JlS
I
L
1....r-.-+w\r-....J
TL494
(3C)
Tl
+
2
4~---'---------n
r-r=--....
-+-----I~
Vh
GH
Figure 2-68. Vh Supply Main Circuit
~
~
vy
v v
V
"
"v
V "'"I
IV V
1
bv
5J.lc
Figure 2-69. 494 Switching Wave Form
2-59