Hitachi RAC-25RPA - Description of Main Circuit Operation

Fig. 1-1
Power to operate indoor unit (DC35V) is generated at the power supply in outdoor unit and it is sent to indoor unit
through the connecting cord C and D.
Then, DC 12V (12V line) is generated using DC/DC converter from the voltage sent from outdoor unit, as the
control voltage of 12V is required to drive the auto sweep motor and others.
Furthermore, 5V (5V line), which is necessary to drive the microcomputer and to control the fan motor, is generated
using three-terminal regulator IC121.
1. Power circuit
DESCRIPTION OF MAIN CIRCUIT OPERATION

RAF-25RPA RAF-35RPA
C133
Q111
R114
Q113
Q112
R111
R115
C113
C116
R112
ZD111
R116
R117
C111
Q116
R124
R121
R122
R123
Q115
C112
IC111
8
L751
R631
L752
R752
C132
ZD131
M
CN10
1
2
3
4
5
6
C131
C751
C621
R751
Motor
Indoor Fan
IN OUT
GND
D121
-
0V
+
ZD121
R118
C103
35V
35V
0V
ICP2
C115
L111
C114
D111
R119
ICP1
-
-
+
C102
+
12V
5V
0V
5V
C121
IC121
C123
C122
R125
R126
XA-6P-Top
R131
R132
Q131
CJ2
R120
Q114
Q751
47 97 57 45
7
10
68
IC712
7
6
1
4
3
2
5
12 V power supply Power supply voltage Indoor fan power supply Indoor fan PWM output Indoor fan speed feedback
54