Sharp AE-X12PSR, Service Manual

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SHARP(CHINA)INVESTMENT CO.,LTD
When the IGBT is ON, an electric current flows to the IGBT via the reactor.
When the IGBT turns OFF, the energy stored while the IGBT was ON is charged to capacitor.
As such, by varying the ON/OFF duty of the IGBT, the output voltage is varied.
This circuit brings the operating current waves form closer to the waveform of commercial power supply voltage to maintain a high power factor.
Because of the capacitor input, when the PFC circuit is OFF, the phase of the current waveform deviates from the voltage waveform.
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 wave form in phase.
As described above, the ON/OFF operation of the IGBT controls maintain a high power factor by keeping the current phase closer to that of the supply
voltage.
2.2 Detailed explanation of PFC drive circuit sequence
t0~t1: IGBT Off, to detect the voltage Zero-crossing;
t1~t2: IGBT PWM (20KHz), to improve current waveform closer to voltage waveform;
t2~t3: IGBT Off;
t3~t4: IGBT PWM (20KHz), to improve current waveform closer to voltage waveform;
t4~t5: IGBT Off, to detect the voltage Zero-crossing;
The detected clock waveform is used to judge the power source frequency (50Hz/60Hz).
3. Explanation of IPM drive circuit
The IPM for compressor drive is made by Fairchild.
The power supply for the IPM drive, the shunt resistance for over current detection, etc., are provided outside the IPM (control PCB).
3.1. IPM drive power supply circuit
The power supply for the upper-phase IGBT (HU, HV, HW) drive employs a bootstrap system, and provides power to the upper-phase IC.
The 15-V power supply for the lower-phase IC is provided by the control printed circuit board (PCB).
3.1.1 Brief explanation of bootstrap system (single power drive system)
To supply power to the upper-phase IC, the microcomputer (IC1) turns ON the lower-phase IGBT (LU, LV, LW).
This results in a charging current that flows to the electrolytic capacitor of each upper-phase IC input and charges the bootstrap capacitor with a 15V
current
The power supply for the subsequent stages is charged while the lower-phase IGBT is ON in ordinary compressor drive control.
-Bootstrap Circuit Design
Operation of Bootstrap Circuit
The V
BS
voltage difference between V
B(U,V,W)
and V
S(U,V,W)
, provides the supply to the HVIC within the Mini-DIP SPM package family in Motion-SPM
products. This supply must be in the range of 13.0V~18.5V to ensure that the HVIC can fully drive the high-side IGBT. The Mini-DIP SPM package
includes an under-voltage lockout protection for the V
BS
to ensure that the HVIC does not drive the high-side IGBT, if the V
BS
voltage drops below a
specific voltage(refer to the datasheet).This function prevents the IGBT from operating in a high-dissipation mode.
The V
BS
Floating supply can be generated a number of ways, including the bootstrap method described here (refer to Figure 34).This method has the
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