AU-X095 - Sharp Air Conditioner Service Manual (repair manual). Page 4

4

The indoor unit control circuit is constructed around a CPU. Its main functions are reception of signals from the remote
control, transmission and reception of signals from the outdoor unit, control of the indoor fan motor, and control of the
louver motor.

If a jumper has been inserted at the position indicated by the dotted line in the diagram above, when the indoor power
socket is plugged in, CPU IC1 pin 39 goes HIGH (5V) and automatic mode operation begins.

The 220/240 V AC shown in the diagram above is generated when the indoor power socket is plugged in. The voltage
is lowered by the transformer TR. The voltage on the secondary side of the transformer is approximately 16 V AC. The
diode bridge formed by D1 to D4 performs full-wave rectification on this voltage. The resulting waveform is then
smoothed by capacitor C3, and finally approximately 17 V DC is asserted at both ends of C4. When this 17 V DC is
input to IN and GND of the 3-terminal regulator IC3, a stable voltage of 12 V DC is output across OUT and GND. The
17 V DC also passes through R3 to the Zener diode ZD1 and a stable voltage of 5 V can be obtained at both ends of
ZD1.

CPU (IC1) pin 39

5V

+

C4

ZD1

C3

D2

D1

AC 220/240V

12V

5V

R3

IN

OUT

GND

D4

D3

–

C6

+
–

IC3

C5

+
–

TR