AU-X095 - Sharp Air Conditioner Service Manual (repair manual). Page 20

20

When 220/240 V AC is supplied to terminal boards (1) and (N), an AC power supply rush current will flow temporarily
because there is an uncharged electrolytic capacitor on the load side. A current surge suppression circuit is included to
prevent damage to the circuit from this rush current,

When 220/240 V AC is supplied between terminal boards (1) and (N), the AC current passes through posistor PTC1 to
charge the electrolytic capacitor on the load side. The rush current is suppressed by passing it through the posistor.
When the load is charged on the electrolytic capacitor, CPU IC1 begins operation, and after an approximately 0.5
second delay, pin 23 goes to HIGH output. When pin 23 goes HIGH, digital transistor Q1 goes ON, MRY1 (main relay)
goes ON, and the circuit begins to operate normally.

Digital transistor Q1 is used here because, like the outdoor fan relay, the CPU cannot directly drive the relay.

CPU (IC1) pin 23

Noise

filter

circuit

13V

N

1

Terminal
Block

Load

Q1

MRY1

PTC1

D3