REV.-A
General Operation
Figure 2-38 shows the block diagram of
IC2A (STK6722). The carriage motor has four coils A, B, C,
and D, and each coil is driven by the corresponding phase driver A to D. These phase drivers are switched
directory by the output pulses from ports
CRA
to
CRD
of the gate array
(IC3A:
E05A15HA). When the
phase drivers are turned off, the surge voltage (e = – L X
diidt) generated from the coils of the carriage
motor is applied to the surge voltage absorber via the flywheel diode attached to each phase driver,
and is absorbed.
This circuit drives the carriage motor using a constant current chopper type drive system. Most of this
circuit is included in the 4 phase stepper motor driver
IC
(IC2A:
STK6722HA). Chopper control is
performed using a separately-excited system (oscillation frequency: approximately 24 KHz). The carriage
motor supply voltages VCAB and
VCCD
are applied intermittently so that the coil current is kept constant.
.-
+35VDC
1
.—
~
Surge
Voltoge
Absorber
1
+
‘3
,.
—-
--
—
From
E05A15HA
From
E05A15HA
~
A04
Col
B04
A
w
Vcco
B
2
—-
)
Phase A
Phose
B
Phase C Phase D
Driver
Driver
Driver
Driver
1
r
I
------%-LET’
,
I
I
+5V
h
Polof
Vref
E05A16GA
(
From Reference Voltage
Generotlon Circuit
)
Figure 2-38. Carriage Motor Drive Circuit Block Diagram
2-47
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