IVT 12KHR-N Service Manual page 21

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 (15). 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 more then 20 s. is generated from IPM Fo pin (14), 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
a1
SC reference voltage
IPM overcurrent
detection circuit
SET
(About 25 A)
SC
Delay by CR time constant circuit
P
Shunt resistance
R49
N
CiN
15
FO
14
2 – 17
RESET
More than 20
Overcurrent
5V
0V
12KHR-N
IC1
34
51 ~ 56