Epson DFX-9000 - Page 91

Epson DFX-9000 Revision B
Operating Principles Circuit operation 84
LF Motor drive circuit
The LF Motor is a HB stepping motor. A dedicated unipolar drive
control device for a 2-phase stepping motor uses paper sensor pulse
counts for position control. The speed is controlled using excited-cycle
and open-loop control. Figure 2-29 shows a circuit block diagram of the
LF motor.
Figure 2-29. LF Motor Drive Circuit Block Diagram
The input of an excited cycle output (M_TIM2) from the SoC ASIC to
the Mechanism Control ASIC provides automatic phase-switching
control. The phase data signal LFM [A:D] is output from the MOTOR
control section of the Mechanism Control ASIC, and the internal FET of
the LF motor driver turns ON when the output is “High-Z”, causing
current to be applied to the motor. The motor current passes through the
resistance detection section. At the same time, the voltage applied to the
detection section is compared with the voltage generated in the reference
voltage section of the LF motor driver internal circuit. If the applied
voltage exceeds the reference voltage, a logic operation AND is
performed between the LF motor driver internal comparing circuit and
the phase data signal to turn the internal FET OFF, keeping the output
current constant. The reference voltage generation section contains a
voltage divider with 4 resistances, and controls output current values for
acceleration, deceleration, constant speed, and stop.
ASIC
LFMA
LFMC
LFMB
LFMD
LFMI0
LFMI1
+42V
M_TIM2
Power Unit
Current detection
section
Reference
voltage
generation
section
LF Motor
Driver
Safety Check
detection section
LF MOTOR