Epson DFX-9000 Service Manual page 92

Epson DFX-9000
RF Motor drive circuit
The RF motor is a permanent magnet (PM) stepping motor. A dedicated
unipolar drive control device for a 2-phase stepping motor controls the
position using paper sensor pulse counts. The speed is controlled using
excited-cycle and open-loop control. The following shows a detail block
diagram of the RF motor.
Safety Check
+42V
Power Unit
detection section
ASIC
RBMPA
RBMEA
RBMI0 Reference
voltage
generation
RBMI1
section
RBMPB
RBMEB
M_TIM3
Figure 2-30. RF Motor Drive Circuit Block Diagram
The input of an excited cycle output (M_TIM3) from the SoC ASIC to
the Mechanism Control ASIC provides automatic phase-switching
control. A PHASE and ENABLE signal are output from the MOTOR
control section of the Mechanism Control ASIC. The PHASE signal
switches, and the current load direction is determined, when the
ENABLE input is "L" and the BRAKE input is "H". A built-in pre-set
OFF-time PMW current control circuit ensures the load current is
limited to its set value. The limit value is set by the resistance value of
the current detection circuitry and the voltage output from the reference
voltage generation section. The reference voltage generation section
contains a voltage divider with 4 resistances, and controls output current
values for acceleration, deceleration, constant speed, and stop.
Operating Principles
Current detection
RF Motor
section
Driver
RF MOTOR
RF Motor
Driver
Current detection
section
Circuit operation
HCPP Motor, APTC Motor, and OC Motor Drive Circuits
The HCPP motor, APTC motor, and OC motor are PM stepping motors.
The position control of these motors is achieved using paper sensor
pulse counts, and speed is controlled using excited cycle and open-loop
controls. A general-purpose transistor array provides the control logic.
The three motors are constant-voltage motors and their drive circuits
have identical configuration. The following figure shows a block
diagram of HCPP motor as an example.
+42V
Power Unit
ASIC
HCMA
HCMB
HCMC
HCMD
M_TIM4
Figure 2-31. HCPP Motor Drive Circuit Block Diagram
The input of an excited-cycle output (M_TIM4) from the SoC ASIC to
the Mechanism Control ASIC provides automatic phase-switching
control. The phase data signal HCM [A:D] is output from the MOTOR
control section of the Mechanism Control ASIC, and an internal
transistor on the HCPP motor driver turns ON when the output is "High-
Z", causing current to be applied to the motor. Since the drive circuit is a
constant-voltage drive circuit, only the switching timing is controlled by
the Mechanism Control ASIC. For the same reason, the current value for
a single phase depends on the motor winding resistance specification.
The HCPP motor driver is a NPN type Darlington transistor with a built-
in avalanche diode.
Revision B
Safety Check
detection section
HCPP Motor
Driver
HCPP MOTOR
85