Epson Stylus 820 Service Manual page 56

Operating Principles
The figure below shows a block diagram of the carriage motor, and the Table 2-12 lists the connection
between current control value and output current.
Figure 2-24. Carriage Motor Driver Circuit Block Diagram
Table 2-12. Connection between Current Value and Input Signal
I01 (I02)
L
H
L
H
The micro step method is performed by PWM control in the driver IC, as shown below.
Phase 1
Figure 2-25. A2919 Internal Block Diagram
2-24
IC1 (GA)
VREF0
VREF1
VREF2
IC2 (CPU)
10
P56
9
P57
8
BPTO0
Phase A or /A
7
BPTO1
6
BPTO2
Phase B or /B
5
BPT12
I11 (I12)
L
L
H
H
` -`
A -A
B
Full Bridge Full Bridge
Bi-poler Bi-poler
PWM1 PWM2
I12
I11 I01
Frequency is decided by the
external CR circuit.
Stylus Color IIs / Stylus 820
141
142
143
A2919
3
PHASE2
11
PHASE1
Output Current
1 TRIP (100%)
2/3 TRIP (67%)
1/3 TRIP (33%)
0 (0%)
-B
Phase 2
I02
Output Waveform
+5 V
Vref
Rev. A