Cooling Fan Driver Circuit - Epson Stylus Color 980 Service Manual

EPSON Stylus Color 980

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 C380 main board is considerably large compared to other
printers. Therefore a thermistor is attached to the heat sink fixed to the
trapezoid 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.
Start
t1 = Heat sink temperature on the C380 main board
t2 = TH1 temperature on the C380 main borad.
Is
YES
the fan t1 >/= 50 C
rotating?
t2 >/= 55 C
NO
YES
t1 >/= 40 C
or
t2 >/= 50 C
NO
YES
t1 >/= 36 C
or
t2 >/= 42 C
NO
Return to the Start.
Figure 2-20. Main Routine of the Cooling Fan Drive
Revision A
YES
Error 1
or
NO
YES
t1 >/= 60 C
or
t2 >/= 60 C
NO
Fan On
Fan Off
Error 1
72