Cooling Fan Driver Circuit - Epson SEIJ98006 Service Manual

EPSON Stylus Color 900

2.3.7 Cooling Fan Driver Circuit

Since this printer drives a large number of PZT elements (total of 480
nozzles) with a high drive frequency (maximum 32.4 K Hz), heat
radiated around the printheads and the trapezoid waveform production
circuit on the C265 main board is considerably large compared to other
printers. Therefore a thernmistor is attached to the heat sink fixed to
thetrapezoid waveform production transistors to prevent the trapezoid
waveform production transistors (Q3 - Q6) and adjacent HIC from
operating abnormally due to high temperature. When the thermistor
detects abnormally high temperature, the printer turns the cooling fan
on to forcibly blow out heat from the lower case. Figure 2-19 shows the
cooling fan driver circuit block diagram. Table 2-19 shows how the
signals output from the ASIC and corresponding fan conditions.
Figure 2-19. Cooling Fan Driver Circuit Block Diagram
Table 2-19. Cooling Fan Control by the ASIC (IC2)
ASIC (IC2, 176- pin) condition
High
Low
Operating Principles
Cooling fan condition
(5 VDC) On
(0 VDC) Off
Electrical Circuit Operation Principles
Figure 2-20 shows the main routine of the cooling fan drive.
Figure 2-20. Main Routine of the Cooling Fan Drive
Revision C
74