AU-X095 - Sharp Air Conditioner Service Manual (repair manual). Page 24

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The diagrams below show the current waveforms for an AC power source with and without the active filter.

As shown in the diagram, when there is no active filter, the current waveform is warped, causing harmonics. Inserting
an active filter reduces the warping and suppresses the harmonics.

The active filter is driven only when the compressor is in operation. This is controlled by CPU IC1 pin 48. When pin 48
is set to HIGH, transistor Q5 goes ON, and connector CN2 pin 12 on IPM goes LOW. When CN2 pin 12 goes LOW, the
IPM internal circuit causes 13 V to be generated at connector CN1 pin 1 on IPM, driving the active filter.

When the active filter detects an abnormal voltage, current or temperature, it sets connector CN1 pin 2 on the active
filter to HIGH. This causes the photo coupler in IPM to go OFF, putting connector CN2 pin 11 on IPM in OPEN state.
When CN2 pin 11 becomes OPEN, HIGH is input to CPU IC1 pin 49, starting the error processing. When error
processing begins, the compressor and the active filter are stopped.

The active filter is combined with a full-wave rectification circuit and smoothing circuit to generate a stable 380 V DC
voltage.

AC 220/
240V

CN1

CN1

Full

rectifier

circuit

Smoothing

circuit

Q5

5V

R27

CPU (IC1) pin 48

CPU (IC1) pin 49

CN2

Without active filter

With active filter