Description Of Main Circuit Operation - Hitachi RAK-18PSPA Service Manual

DESCRIPTION OF MAIN CIRCUIT OPERATION

RAK-18/ 25/ 35PSPA
1. Power circuit
35V
ICP2
35V
R121
ICP1
Q113
Q115
+
-
Q116
0V
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.
Q111
L111
R114
Q112
8
5
R115
7 2
IC111
Q114
6
3
1 4
47
12 V power supply Power supply voltage
12V
D121
+
IC121
-
IN OUT
GND
+
-
IC712
7
97 57
Indoor fan power supply
Fig. 1-1
CJ2
Q131
5V
5V
Q751
0V
0V
10
45
Indoor fan PWM output Indoor fan speed feedback
CN10
XA-6P-Top
6
Indoor Fan
5
Motor
4
M
3
2
1
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