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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)

22

There are two thermistors TH1 and TH2 in the temperature sensor circuit. They are connected in series with resistors
R10 and R9, and the divided voltage is applied to CPU IC1 analog input pins 2 and 4. CPU IC1 performs AD conversion
on the analog voltage from these two thermistors to perform the most appropriate cycle control.
C27, C28 and R11, R12, C30, C31 are inserted to absord noise.

There is a U-phase, V-phase, W-phase, and XYZ-phase power circuit built into the IPM as the power source for the
IGBT base current. It also contains six builtin OPIC elements to drive this base current, and is  to the control signal line.

When a Low PWM signal is output from CPU IC1 pins 34 to 39, the OPIC elements inside the IPM turn ON, the IGBT
base current flows, and the IGBT goes ON. When the CPU output is HIGH, the IGBT goes OFF.

Pairs 34 and 35, 36 and 37, 38 and 39 will never go ON (Low input) simultaneously. When the output changes, there is
an interval of more than 10 

µ

s during which both are OFF.

In this way, the six IGBT ON/OFF combinations are used to apply a 3-phase AC voltage to the compressor, causing the
compressor motor to turn.

R11

R12

+

C28

C30

C31

–

+

C27

R9

R7

5V

CN8

TH1

TH2

R10

–

CPU (IC1) pin 2

CPU (IC1) pin 4

DC 380V

CN2

PM1 (IPM)

R21~26

Compressor

CPU(IC1)

23

The IPM takes a 380 V DC input and generates a 13 V U-phase, V-phase, W-phase and XYZ-phase power supply from
its internal power supply circuit. GND is at CN2 pin 7 and 13 V is output at pin 9.

The 13 V power supply output from IPM is lowered by R15, giving an input voltage of 8 to 9 V to the three-terminal
regulator IC2, and generating the 5 V power supply for the control circuit.

The 5V power supply generated by the control circuit is input to IPM. Inside IPM it is used as the OPIC input power
supply and the fault output power supply. When IPM is operating correctly, the output from pin 10 on CN(2) is HIGH,
turning digital transistor Q5 to ON, and setting CPU input pins 15 and 16 to LOW input.

When IPM detects a fault in the current from the 380 V DC line, or detects an abnormal temperature, CN(2) pin 10 is set
to LOW output, turning Q5 to OFF, and setting CPU pins 15 and 16 to HIGH input. When CPU pin 15 goes to HIGH
input, the internal hardware sets all PWM waveform output (34 to 39) to OFF, and the LOW to HIGH rising edge causes
a software interrupt, causing fault processing to begin. CPU pin 16 is input to monitor the HIGH/LOW input level.

DC 380V

CN2

PM1 (IPM)

13V

IC2

5V

7805

C32

R15

DC 380V

5V

CN2

PM1 (IPM)

5V

C40

Q5

C32

R15

CPU (IC1) pin 15
CPU (IC1) pin 16

24

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