Epson TM-U375 - Electrical Specifications; Electrostatic Protection; Reliability

2-29
Platen switching solenoid drive circuit
The printer’s platen is movable, so that it can produce the
appropriate platen gap during printing when electricity is
supplied to the platen switching solenoid. (Refer to Section
2.2.2,
Printer mechanism .) Figure 2-53 shows the platen
switching solenoid drive circuit.
The platen switching solenoid operations (retraction, hold-
ing, and return) are controlled by changing the direction
and amount of the current. Therefore, the drive signals
PLUNGER+ CN12 (pin 14) and PLUNGER– CN12 (pin 15)
for the platen switching solenoid are generated by applying
the current direction switching signals PL_1 (pin 19), PL_2
(pin 18), and PL_RET (pin 15), output by the CPU (U12), to
the bridge driver (QM5).
The current is controlled during initialization (return opera-
tion) and when the hold current is applied. During initializa-
tion, the current is limited by PWM control through the
software using the PL_RET signal. When the hold current
is applied, the current is limited by PWM control by the
hardware using an IC (U8B). Table 2-6 shows the platen
switching solenoid drive signal logic.
Table 2-6. Platen Switching Solenoid Drive Signal
Logic
Function PL_1 PL_2 PL_RET PL_HL
Off L L L L
Return operation H L PWM L
Retraction L H L L
operation
Holding operation L H L H
Clutch solenoid drive circuit
Supplying current to the clutch solenoid in the printer
mechanism cuts off the driving power of the paper feed
motor so that paper feeding is not performed. This makes
it possible to switch between paper roll printing and cut
sheet printing. (Refer to Section 2.2.4,
Paper feed mecha-
nism
.)
The CPU (U12) outputs the CLUTCH signal from the P53
terminal (pin 14). The clutch solenoid is driven when the
CLUTCH signal is high.
Slip switching solenoid drive circuit
The slip paper holder roller (S holding roller) is normally
open; when current is supplied to the paper holder switch-
ing solenoid, the paper holder roller is pushed to the paper
feed roller (S feed roller) side so that the slip paper can be
fed. (Refer to Section 2.2.2,
Paper feed mechanism .)
The paper holder switching solenoid is driven by setting the
SLP_CHG signal (which is output from the P50 terminal
(pin 17)) of the CPU (U12) high. When this signal is in the
drive state, the solenoid turns on for the prescribed length
of time and then goes into the hold state. When in the hold
state, the supplied current is limited through PWM control.
The paper holder roller is returned to its original position by
setting the SLP_CHG signal low.
Figure 2-52 shows the slip switching solenoid drive signal
timing chart, and Figure 2-53 shows the slip switching
solenoid drive circuit.
Figure 2-52. Platen Switching Solenoid Drive Signal Timing Chart
CONFIDENTIAL