Printhead Driver Circuit - Epson Stylus 820 Service Manual

Operating Principles

2.3.2.5 Printhead Driver Circuit

The printhead driver circuit for this printer is composed of the following:
o Common driver circuit (trapezoidal drive pulse generation)
o Head driver circuit (nozzle control built on the printhead)
SED5619D, the 64-bit thermal head driver in the head drive circuit on the carriage, is used as a nozzle selector
to drive printhead nozzles selectively. Print data is converted into serial data by gate array E05B08 (IC1) and
is output from port SO (pin 13) to the black and CMY head driver circuits. Head driver SED5619D latches
head data when gate array E05B08 outputs the LATCH signal, and the latched data becomes 64-bit parallel
data for the black head or 60-bit parallel data for the CMY head. One bit corresponds to each nozzle.
When data transfer and nozzle selection is complete, gate array E05B08 outputs the common drive pulses
(CHG (MCHG) signal, DCHG1 signal, DCHG2 signal, DCHG3 signal) to the common driver circuit. The
common driver circuit then generates the trapezoidal pulse and applies it to the printhead as a common drive
pulse. Then, the nozzle selected by the head data is activated to eject ink.
Normal Mode
Figure 2-27. Head Driver Circuit Block Diagram
The normal mode for the Stylus Color IIs operates differently from the normal mode for other Stylus printers.
The printer uses normal mode printing only when the user selects 360 dpi printing with the custom printer
driver. (Refer to Section 2.2.2. ) The figure below shows the head drive waveform for normal mode.
Note:
If single firing is performed, printer outputs only wave # 1.
B
C
A
A: 1st charge, B: 1st hold, C: 1st discharge
D: 2nd hold, E: 2nd discharge
F: 3rd discharge, G: pause
Figure 2-28. Head Driver Waveform for Normal Mode
2-26
IC1 (GA)
132
HCLK
139
LAT
131
SI
138
MCHG
137
CCHG
133
DCHG1
134
DCHG2
135
DCHG3
136
PWM
Common Driver
Circuit
IC2 (CPU)
96
AN2
76
M/C
99
TH
97
ID4
94
ID3
95
ID2
96
ID1
73
CO
#1
D
E
F
Stylus Color IIs / Stylus 820
SED5619
64-bit data
Common
Printhead
G
#2
Rev. A