AU-X095 - Sharp Air Conditioner Service Manual (repair manual). Page 21

21

This circuit detects the AC current flowing in the inverter section using the current transformer CT1, converts the voltage
causing it to a DC analog voltage, applies it to CPU IC1 pin 7, and using the AD conversion function of the CPU,
performs peak control and abnormality detection. When an AC current flows through the primary side of CT1 in the
diagram above, a proportional voltage is generated on the secondary side. Half-wave rectification is performed by diode
D1, and the wave is smoothed by R4 and the electrolytic capacitor C20. The smoothed DC voltage is divided across R4
and R5, and is input to CPU IC1 pin 7. R6 and C21 form a low-pass filter to absorb noise. D2 is for bypassing the power
supply so that no voltage greater than 5V is applied to CPU IC1 pin 7.

The relationship between the AC current flowing through the inverter and the analog voltage is shown in the following
diagram. Note this does not include the current through the indoor unit, outdoor fan, etc. Add approximately 0.7 A for
the total current of the air conditioner.

CPU (IC1) pin 7

+

C20

R4

R6

R3

D1

CT1

D2

5V

–

C21

R5

0.9V

1.0

1.8V

2.7V

3.6V

2.0

2

3.0

4.0

4

6

8

Load Current (A)

Analog

 Voltage (V)