IVT AE-X12GR-N Service Manual page 19

4.1.2 DC overcurrent 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 overcurrent. 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 overcurrent detection input pin (34) of
the microcomputer (IC1) and turns OFF the PWM signal output (IC1 pins (51) through (56)) to the IGBT gate.
Protection circuit status
(Lower phase)
Internal IGBT gate
Output current Ic (A)
Sense voltage relative
to shunt resistance
Error output Fo
IPM
detection
(About 22 A)
a1
SC reference voltage
P
N
overcurrent CiN
circuit 26
FO
24
SET
SC
Delay by CR time constant circuit
About 1.8 ms
Shunt resistance
Overcurrent
R49
2 – 15
AEX12GRN
RESET
5V
IC1
34
0V