Epson LQ-1050 Technical Manual page 97

REV.-A
General Operation
Figure 2-56 shows the carriage motor drive circuit block diagram. 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 AO 1 to DO 1 of the MCU (2A). When the phase
drivers are turned off, the surge voltage (e = – L X di/dt) 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 STK6722H ( 1 A). Chopper control is performed using a separately-excited
system (oscillation frequency: approximately 24 KHz). The carriage motor supply voltages
are applied intermittently so that the coil current is kept constant.
+ 35vDC
Surge Voltage
Absorber
-
From E05A09BA
'3 2
— -
- i
Phase A
Driver
1
Fig. 2-56. Carriage Motor Drive Circuit Blockdiagram
From E05A096A
A
B
V
Phase C
Driver
Driver
POT2 Vref
of
Reference Voltage
Generation Circuit
(
2-56
001
Fly wheel diode
Phase D
I I
)
and VCCD
V
CAB
I