Epson SEIJ98006 Cooling Fan Driver Circuit, S t a r t, R e t u r n t o t h e S t a, Revision C

EPSON Stylus Color 900 Revision C

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

Figure 2-20 shows the main routine of the cooling fan drive.

S t a r t
	t 1	=	H e a t s in k t e m p e r a
	t 2	=	T H 1 t e m p e r a t u r e o

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.

I s	Y E S t 1 >°C/ =Y E
t h e		f	a n	o r
r o t a t in gt?2 >C/° =
N O					N O

5S0

E r r o r 1

5 5

t 1 >°C/ =Y E6		S0
o r		E r r o r
	6
t 2 >°C/ =		0

N O

+ 4 2

6 . 8
E 0 5 B 5 9 ( I C 2 )	3 5 V .
D r o p s t o
	3 9	K	C N 1 3
		F 6
			1 + 3
1 7 6
F A N			2 G
			F A N

Figure 2-19. Cooling Fan Driver Circuit Block Diagram

Table 2-19. Cooling Fan Control by the ASIC (IC2)

t 1 >°C/ =Y E4S0 o r

t 2 >°C/ = 5 0

N O

t 1 >°C/ =Y E 3S6			F a n
o r		4 2
t 2	>°C/ =

N O

F a n O n

O f f

ASIC (IC2, 176- pin) condition	Cooling fan condition
High	(5 VDC) On
Low	(0 VDC) Off

R e t u r n t o t h e S t a

Figure 2-20. Main Routine of the Cooling Fan Drive

Operating Principles Electrical Circuit Operation Principles 74