Sharp AY-ZP35PR Service Manual page 18

The power source frequency is also determined at the same time.
The IGBT turns ON after the time length determined by the zero-cross point to supply a current to the IGBT via the reactor.
This brings the current waveform closer to the voltage waveform in phase.
As described above, the ON/OFF operation of the IGBT controls the increase/decrease of the compressor power supply voltage (DC
voltage ) to improve the compressor efficiency and maintain a high powerfactor by keeping the current phase closer to that of the supply
voltage.
AC voltage waveform
AC current waveform
AC voltage and current waveforms when PAM is OFF
3.2.1 Detailed explanation of PAM drive circuit sequence
AC voltage waveform
Clock
IGBT ON
3.2.2 AC clock (zero-cross) judgment
‡ The clock circuit determines the time from one rising point of the clock waveform to the next rising point.
The detected clock waveform is used to judge the power source frequency (50Hz).
‡ The zero-cross of the AC voltage is judged as the rising of the clock waveform, as shown in the diagram above.
3.2.3 IGBT ON start time (delay time B)
‡ %DVHG RQ WKH ]HURFURVV RI WKH AC voltage, the IGBT turns ON after a delay time set according to the power source frequency.
3.2.4 IGBT ON time (C)
‡ After the above delay time, the IGBT turns ON to supply a current to the reactor.
‡ The ON time of the IGBT determines the amount of energy (level of DC voltage rise) supplied to the reactor.
DC voltage level in each operation mode (varies depending on external load conditions)
–Cooling operation --- 260 to 280 V
–Heating operation --- 260 to 290 V
3.3. PAM protection circuit
To prevent excessive voltage of PAM output from damaging the IPM and electrolytic capacitor as well as the control printed circuit
board (PCB), this circuit monitors the PAM output voltage and turns off the PAM control signal and PAM drive immediately when an
abnormal voltage output is generated. At the same time, it shuts off the compressor operation.
The protection voltage level is as follows.
A
B C
C9
C10
DC Voltage
550uF
550uF
400V
400V
AC voltage waveform
AC current waveform
Zero-cross detection
IGBT ON period
AC voltage and current waveform when PAM is ON
(Overvoltage detection)
R125
270K
5V
R126
D19
270K
C87
R127
R128
50
13K
13K
0V
2-13
AY-ZP35PR
50Hz
A
1.2mS
B
1.2mS
C
0.25 2.3mS
IC1
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