Fuji Electric Co., Ltd.
3-17
MT6M12343 Rev.1.0
Dec.-2016
Chapter 3
Detail of Signal Input/Output Terminals
5. Over Current Protection Input Terminal IS
Fig.3-20 Operation sequence of Over Current protection
Over current protection (OC) is a function of detecting the IS voltage determined with the external shunt
resistor, connected to N(*)
*1
and COM.
Fig.3-19 shows the over current sensing voltage input IS circuit block, and Fig.3-20 shows the OC
operation sequence.
Fig.3-19 Over current sensing voltage input IS circuit
t1 : IS input voltage does not exceed
V
IS(ref)
, while the collector current of the lower side IGBT is under the
normal operation.
t2 : When IS input voltage exceeds
V
IS(ref)
, the OC is detected.
t3 : The fault output
V
FO
is activated and all lower side IGBT shut down simultaneously after the over current
protection delay time
t
d(IS)
. Inherently there is dead time of LVIC in
t
d(IS)
.
t4 : After the fault output pulse width
t
FO
, the OC is reset. Then next input signal is activated.
*1 N(*) : N(U), N(V), N(W)
To prevent the IPM from
unnecessary operations due to
normal switching noise or recovery
current, it is necessary to apply an
external R-C filter (time constant is
approximately 1.5µs) to the IS
terminal. Also the IPM and the shunt
resistor should be wired as short as
possible.
Fig.3-19 shows that the diodes in
the IPM are electrically connected to
the V
CCL
, IS and COM terminals.
They should not be used for voltage
clamp purpose to prevent major
problems and destroy the IPM.
+
-
IS
Ref
R
Driver
V
CCL
COM
< LVIC >
N ( U , V , W )
Alarm
timer
V
CCL
UV
(OH)
VFO
OC detected
L ower side arm
Input signal
IS input voltage
VFO output voltage
t
1
t
2
t
3
t
4
V
IS(ref)
t
d(IS)
>
t
FO
(min.)
