MT6M15962a
© Fuji Electric Co., Ltd. All rights reserved.
5.5 Short circuit protection (SC) operation
• If a load short circuit occurs after
I
C
is flowing and
I
C
exceeds
I
SC
, the peak current of
I
C
is suppressed
momentarily. After the elapse of
t
SC
, an alarm signal is output and the IGBT is turned off softly
※
1
. (1)
• The SC protection operation is stopped if
V
in
is in OFF-state after the elapse of
t
ALM(OC)
. (2)
• If a load short-circuit occurs as soon as
I
C
began to flow and
I
C
exceeds
I
SC
, the peak current is
suppressed momentarily. After the elapse of
t
SC
, the alarm signal is output and the IGBT is turned off
softly. (3)
• The SC protection operation continues even after the elapse of
t
ALM(OC)
if
V
in
is in ON-state. The SC
protection operation is stopped when
V
in
becomes OFF-state. Even if the protection operating
duration is sufficiently longer than
t
ALM(OC)
, the alarm signal is output only once. (4)
• If a load short-circuit occurs after
I
C
began to flow, the peak current of
I
C
is suppressed momentarily
as soon as the
I
C
exceeds
I
SC
. After that, if
V
in
becomes OFF-state before the elapse of
t
SC
, the SC
protection operation is not activated and the IGBT is turned off normally
※
2
. (5)
• If a load short-circuit occurs as soon as
I
C
began to flow and
I
C
exceeds
I
SC
,
I
C
peak is suppressed
momentarily. If
V
in
becomes OFF-state before the elapse of
t
SC
, the SC protection operation is not
activated and the IGBT is turned off normally. (6)
※
1 Soft turn off: This means a slower than normal turn-off.
※
2 Normal turn off: This means a normal turn-off operation.
3-18
Fig.3-12 SC protection operation
V
in
: Input Signal Voltage
I
C
: Collector current
I
SC
: SC trip level
t
ALM(OC)
: Alarm signal hold time
t
SC
: Short circuit protection delay time
