Epson LQ-2550 Technical Manual page 127

Control Circuit
The control circuit consists of hybrid IC li8D2 148 (2 C). This IC is divided into four blocks.
1. HF Motor ON/OFF Circuit
This circuit controls the ON/OFF switching of the HF motor using two inputs (ENB signal and HF motor
thermistor resistance). The sub CPU sets the ENB signal LOW when the thermistor in the printhead
detects a temperature of 40"C or higher. While the HF motor is on, the sub CPU monitors the temperature
of the HF motor using a thermistor in the HF motor to prevent the motor coils from burning if the motor
stops due to external noise (Refer to Table 2-5 1.).
Table 2-51. H8D2148 Input Signal and HF Motor Status
TH Terminal Voltage [V]
—
H
L
NOTE: Even when the
received.
Integration Circuit
2.
When the output from the HF motor ON/OFF circuit changes from HIGH to LOW, it is integrated by this
circuit, and output to the block in the second stage. Acceleration control is performed using this
integrated waveform.
3. Unstable Oscillation Circuit
This circuit generates the reference clock to execute phase switching for the HF motor. R43 is an
oscillation frequency selection resistor. The frequency starts rising gradually at the leading edge of the
integrated signal from the previous stage and stablizes at the set value (approx. 1600 Hz).
4. Phase Pulse Generation Circuit
This circuit generates the phase switching pulse for the 2-phase stepper motor. The phase switching
pulse is synchronized
Drive Circuit
The drive circuit consists
absorbs the surge voltage output from the motor coil when the HF motor coil drive transistor changes
from on to off. D4 and D5 are flywheel diodes, and ZD5 is a surge voltage consumption Zener diode.
HF Motor Status
OFF
OFF ~ ON
HF motor is on, the motor will stop five seconds after the last print signal is
pulse output from the previous stage.
with the clock
ON Normal
HF motor abnormal heat generation occurs.
HF motor abnormal heat generation ends.
surge voltage absorption circuit that
2-81
REV.-A
Note