AU-X095 - Sharp Air Conditioner Service Manual (repair manual). Page 11

11

The indoor fan circuit is composed of a drive circuit and a rotation frequency detection circuit.

As shown in the diagram below, phase control is used to control the indoor fan rotation. For each rotation of the motor,
three pulses are input from the rotation frequency detection circuit. The CPU reads these pulses, and computes the fan
rotation frequency, then adjusts the SSR ON timing to attain the target frequency.
IC2 is a transistor array that drive SSR.

AC 220/240V

12V

5V

12V

C1

C21

CNR1

NF1

CPU (IC1) 
pin21

CPU (IC1) pin 49

FAN

MOTOR

SSR1

R1

IC2

R22

R21

R20

C16

SSR ON

CPU (IC1)

 pin 49

AC Power

Supply

Fan motor

InPut

Clock

When CPU IC1 pin 49 is asserted to HIGH, SSR goes ON until the next zero crossing point. The clock is used for the
CPU output timing.