Printhead Drive Circuit; Figure 2-24. Trapezoidal Drive Waveform - Epson Stylus Pro Service Manual

Stylus Pro Service Manual

2.3.2.5 Printhead Drive Circuit

The printhead drive circuit for this printer is composed of the following two parts:
r Common drive circuit (trapezoidal drive pulse generation)
r Head drive circuit (nozzle control built on the printhead)
The 64-bit thermal head driver SED5620D in the head drive circuit on the carriage is used as a nozzle selector
to selectively drive the printhead nozzles. Print data is converted into serial data by gate array E05B09 (IC2)
and is output from port BSO (pin 20) to the black head drive circuit or output from port CSO (pin 24) to the
color head drive circuit. Then, head driver SED5620D latches the head data when gate array E05B09 outputs
the BLAT or CLAT signal, and the latched data becomes 64-bit parallel data for the black head, or 48-bit
parallel data for the color head. One bit corresponds to each nozzle.
When data transfer and nozzle selection are complete, gate array E05B09 outputs the common drive pulse
BPWC or CPWC (charge pulse) and BPWD or CPWD (discharge pulse) to the common drive circuit. The
common drive circuit then generates the trapezoidal pulse and applies it to the printhead as a common drive
pulse. After this, the nozzle selected by the head data is activated to eject ink.
Normal Dot / EPSON Micro Dot Printing Mode
The Stylus Color Pro produces two types of ink ejection (normal print mode and EPSON Micro Dot Mode).
The signals for switching ink ejection modes are "SELM" (for normal dot printing) and "SELN" (for EPSON
Micro Dot printing). These signals are output from pin 49 and pin 50 of gate array E05B09 to IC11 and IC18.
In normal dot print mode, the common drive signals (BPWC, CPWC and BPWD, CPWD) are output to the
register arrays (RM12 for black, RM5 for color). In the Micro Dot Mode, the signals (BPWC, CPWC and
BPWD, CPWD) are output to the register arrays (RM11 for black, RM4 for color). The signals through the
resistor array are output to the charge / discharge circuit that consists of Darlington connected transistors.
Then the circuit generates printhead drive pulses.
Common Drive
Signal
Figure 2-23. Normal / EPSON Micro Dot Switching
C O M
G N D
B P W C
C P E C
B P W D
C P E D
Tc: Charge time
Th: Idle time
Td: Discharge time
Rev.A
SELM
Resistor Array
Normal Dot
RM12, RM5
Micro Dot
RM11, RM4
S ELN
T c
P c
Pc: Charge pulse
Ph: Idle pulse
Pd: Discharge pulse

Figure 2-24. Trapezoidal Drive Waveform

Normal Dot
Charge/Discharge
Circuit
Micro Dot
Charge/Discharge
Circuit
T h
T d
V H
P h
P d
Head drive volt age (VH)
Operating Principles
Printhead
2-19