Sharp AE-Z40KR Service Manual page 19

4. Explanation of IPM drive circuit
The IPM for compressor drive is made by Mitsubishi Electric.
The power supply for the IPM drive, the shunt resistance for over current detection, etc., are provided outside the IPM (control PCB).
4.1. 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).
4.1.1 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.
Initial charge period
V
DB
V
D
V
CIN
4.1.2 DC over current detection circuit
When a current of about 25 A or higher flows through the shunt resistance (R49) on the control printed circuit board (PCB), the voltage at this resis-
tance is input to IPM CIN pin (26). Then, the gate voltage of the lower-phase IGBT (LU, LV, LW) inside the IPM turns OFF to cut off the over current.
At the same time, an L output of about 1.8 ms is generated from IPM Fo pin (24), and this results in an L input to over current detection input pin (34)
of the microcomputer (IC1) and turns OFF the PWM signal output (IC1 pins (51) through (56)) to the IGBT gate.
Charging current group
Bootstrap capacitor
High-voltage-withstanding,
high-speed recovery diode
( )
n
Bootstrap circuit
(HU,HV,HW)
HVIC
(LU,LV,LW)
LVIC
2 – 14
AYZP40KR
P(Vcc)
U,V,W,
N-side
IGBT
N(GND