Application Note
25 of 53
V 1.0
2019-04-01
IM393 Application note
IM393 IPM Technical Description
Function and protection circuit
5
Function and protection circuit
5.1
Over-current protection
IM393-XX is equipped with an I
TRIP
input pin. Together with an external shunt resistor, this functionality can be
used to detect over-current events in the negative DC bus. The internal HVIC gate driver will continuously
monitor the voltage on the I
TRIP
pin. Whenever this voltage exceeds the reference voltage (typ. 0.49 V), a fault
signal will be generated on the RFE pin, and all six IGBTs will be turned OFF. Typically, the maximum short-
circuit current magnitude is gate-dependent. A higher gate voltage results in a larger short-circuit current. In
order to avoid this potential problem, the maximum over-current trip level is generally set below twice the
nominal rated collector current.
5.1.1
Timing chart of over-current protection (OCP)
I
TRIP
LIN(U, V, W)
HIN(U, V, W)
T
FLT-CLR
50%
50%
U, V, W
50%
T
ITRIP
50%
RFE
50%
T
FLT
Figure 17
Timing chart of over-current protection function
The threshold of over-current protection can be determined by V
ITRIP+
/ R
SHUNT
, if a single bus shunt is used, and is
directly connected to I
TRIP
pin. The following table shows the delay time of fault reporting and I
TRIP
shutdown:
Table 10
Dynamic electrical characteristics
Symbol
Description
Min.
Typ. Max. Unit
conditions
T
FLT
I
TRIP
to fault propagation delay
400
600
800
ns
V
IN
= 0 V or 5 V, V
ITRIP
= 5 V
T
ITRIP
I
TRIP
to six switches turn OFF
propagation delay
-
-
1.5
μs
I
C
= 5 A, V
DC
= 300 V
In the case of a short-circuit, the current level will rise very quickly to the saturation current of the IGBT. It is
critical to ensure that all IGBTs are turned OFF as soon as possible. Since the IGBTs in IM393-XX are short-circuit
rated (see Table 11), the safe operating of the IPM is guaranteed by minimizing the delay of the external current-
sensing circuit, and ensuring its delay plus T
ITRIP
is less than the IGBT short-circuit rating time. Because IGBT short
circuit rating depends a lot on the gate voltage that is influenced by V
DD
and junction temperature, it is important
to consider all possible conditions.